No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Model for Estimating Radiated Emissions From a Printed Circuit Board With Attached Cables Due to Voltage-Driven Sources
Abstract
Common-mode currents induced on cables attached to printed circuit boards (PCBs) can be a significant source of unintentional radiated emissions. This paper develops a model for estimating the amount of common-mode cable current that can be induced by the signal voltage on microstrip trace structures or heatsinks on a PCB. The model employs static electric field solvers or closed-form expressions to estimate the effective self-capacitances of the board, trace, and/or heatsink. These capacitances are then used to determine the amplitude of an equivalent common-mode voltage source that drives the attached cables. The model shows that these voltage-driven common-mode cable currents are relatively independent of the cable parameters and the trace or heatsink location when the PCB is small relative to the cable length and to a wavelength.
... In the literature, it has been shown that common mode (CM) currents play a dominant role in the radiated emissions mechanism. CM currents can be classified as parasitic and undesirable in the system loop: device → cable → environment → ground plane [5]- [8]. Furthermore, CM current is sometimes referred to as antenna mode current [5], [6]. ...
... Hence, it can be assumed that most of the radiation is caused by the attached cable, with predominantly common-mode noise. The mechanisms underpinning this type of radiation are discussed extensively in the literature [5], [6], [8]. ...
... There have been several studies on this problem. Several previous studies [8]- [13] utilize a model comprising a simple dipole or monopole antenna driven by a single voltage source that represents the noise source on the PCB. However, these studies assume that the input impedance is purely real and not frequency dependent. ...
Being able to predict radiated emissions before using an accredited laboratory can be both time-effective and cost-effective. This study presents a model for predicting radiated emissions from power converters by measuring the common-mode current in the attached cable. When power converters are tested for radiated emissions, the attached cables tend to be thick because of the high currents they carry. Ideally, these cables leave the chamber through connectors in an opening positioned precisely at the middle of the bottom of the turntable in keeping with CISPR 32. However, these connectors are typically not intended for currents higher than 16 A. Consequently, such cables are usually inserted through the side wall of the chamber and are necessarily laid horizontally on the chamber floor. When the turntable is to be rotated with a device on it during a test, the length of the cable attached to the device can exceed 10 meters. The proposed model in this study is based on the transmission line model of a cable loaded with reactive impedance and the assumption that the current distribution along the cable follows a sinusoidal distribution law, much like in dipole antenna theory. The analytic equation of the radiation pattern is derived, and a simplified approximation equation has also been presented. The proposed model also works with short, attached cables and is thus universal. The Maxima software code for automated calculation of the radiated field from measurement data is supplied as supplemental material. The proposed model was experimentally validated by running the fuel cell converter module at 5 kW output power.
... The study on this kind of structure has gained a lot of interest as it is one of the most commonly seen setup of electronic equipment. There are a few recent papers on the study of EMC effect of attached cable and simplified models are proposed to estimate radiated emission from such structure [1][2][3][4][5][6][7]. These studies showed that the electromagnetic field coupling of noise sources from PCB traces to the attached cable can be modelled as an equivalent board-cable model driven by a common-mode source. ...
... These studies showed that the electromagnetic field coupling of noise sources from PCB traces to the attached cable can be modelled as an equivalent board-cable model driven by a common-mode source. Shim and Hubing showed that the magnitude of this common-mode noise source generated through voltage-driven mechanism was related to the capacitance of the PCB trace and signal return plane [2]. Based on this, Deng et al. proposed that if the magnitude of the common-mode voltage source of such model was known, a closed-from equation can be used to estimate the maximum radiated E field at resonant frequency of such model [3]. ...
... An effective voltage drop exists across the signal return plane due to its finite impedance and this drives a common-mode current on the cable. This mechanism can be a source of radiated emissions if the impedance of the signal return path is significant; i.e., the width of the signal return path is narrow or the signal frequency is very high [2]. ...
Common mode current induced on cable attached to a PCB has been a well-known source of unintentional radiated emissions. The coupling mechanism of the common mode current to the cable can be divided into two types: voltage-driven and current-driven. In voltage-driven mechanism, the common mode current is induced by electric field that couples from traces on PCB to the cable. Previous work showed that these radiated emissions can be estimate based on the self-capacitance of the trace and the signal return plane but the method is only reasonably accurate at lower frequency. This paper develops a model which gives an extended frequency range up to 800 MHz. The formulation for the equivalent common-mode voltage source is improved by taking into account the driving point impedance of the cable which behaves as a wire antenna. The radiated emissions estimated by the improved model match well with the values from 3D electromagnetic simulation of the original PCB with attached cable. It represents an improvement compared to earlier model by 11 dB at 400MHz to 16 dB at 700MHz for board size of 10 cm × 16 cm and cable length of 3 m. Similar improvements are obtained for other combinations of board size and cable length. The results show that the cable length is an important factor, in addition to the board area as suggested by earlier work, in determining the magnitude of the equivalent common-mode voltage source. Resonant of the wire antenna affects not only the radiated electromagnetic field but also the common-mode voltage source magnitude due to varying antenna impedances.
... Hockanson [3], [4] introduced current-driven and voltage-driven source models to describe how differential-mode signals on circuit boards induce common-mode currents on attached wires. Shim [5] developed an equivalent model for estimating the radiated emissions from a printed circuit board with attached cables driven by a signal voltage on a trace. This model employed an equivalent common-mode voltage source located at the junction between the PCB ground structure and the attached wire. ...
... According to the imbalance difference model, the geometry in Fig. 3(b) is equivalent to the geometry in Fig. 3(a) in terms of the common mode currents produced. The amplitude of the equivalent voltage sources is determined by (5). At the source end, ∆h = 0.5 as the geometry transitions from perfectly unbalanced (h = 1.0, since there is only one conductor) to perfectly balanced (h = 0.5, since the two conductors are identical). ...
... where L and W are the length and width of the board, l t is length of the trace, d is the distance between the trace and the return plane of the board, and C DM is the capacitance of the trace over an infinitely wide return plane. The stray capacitance of the board is approximately [5], ...
The imbalance difference model introduced by Watanabe is a method for modeling how differential-mode signal currents are converted to common-mode noise currents. A parameter called the current division factor or imbalance factor uniquely defines the degree of imbalance of a transmission line. The imbalance difference model shows that changes in the imbalance are responsible for differential-mode to common-mode conversion. This paper explores various circuit board and cable geometries to illustrate how the imbalance difference model would be applied, and to determine how well common-mode currents obtained using the imbalance difference model compare to full-wave calculations.
... A previous study of electric field coupling to cables from small sources such as printed circuit board traces and ICs showed that the amount of coupling was directly proportional to the source voltage, the source frequency and the self capacitance of the source [4]. The self capacitance is a measure of the electric flux emanating from the IC (in its intended environment) that is not captured by the circuit board ground plane or other nearby structures. ...
... Each of these quantities (voltage, frequency and self capacitance) is localized to the source geometry and doesn't depend on objects or structures distant from the source. In [4], these quantities are used to develop an equivalent common-mode voltage source that replaces the more complicated trace or IC geometry and drives cables attached to a printed circuit board directly. This process allows the complicated geometries on a printed circuit board to be replaced by much simpler structures in a full-wave system model. ...
... For example, the electric moment of an object that had a 1-volt potential relative to a circuit-board ground plane, an angular frequency of 628 rad/sec (i.e. 100 MHz), and a self capacitance of 15 fF would be 9.4 μA. In a system with one circuit board and attached cables, this would basically represent the maximum sum of all commonmode currents that could be induced on the cables [4]. In an equivalent model of the source, any value of source voltage and self capacitance that had this same product would yield an equivalent result. ...
The electric field coupling from ICs to cables or enclosures is proportional to the source voltage, source frequency and the self capacitance of the IC structure. The product of these three values is a quantity that effectively represents the strength of an electric field source independent of the structure(s) that it may couple to. Magnetic field coupling from the small circulating currents generated by ICs and their packages is proportional to the source current, source frequency and the effective mutual inductance associated with the coupling path. The product of these quantities is also a scalar value and represents an IC's ability to couple to cables and enclosures through a magnetic field. These electric and magnetic "moments" can be used to characterize an IC's ability to couple noise to its external environment. These moments depend on local geometric parameters such as the circuit board dimensions, IC package structure, presence of heatsinks, etc., but they are independent of system parameters such as cable and enclosure geometries. Measurements of ICs in a TEM cell with a hybrid can be used to determine these electric and magnetic moments. These moments can then be used to estimate the maximum radiated emissions from the ICs in a given environment.
... Hence, it can be assumed that most of the radiation is caused by the attached cable, with predominantly common-mode (CM) noise. The mechanisms underpinning this type of radiation are discussed extensively in the literature [1], [2]. Manuscript received 2021 The device under test (DUT) is placed on the turntable in a semi-anechoic chamber (SAC), and the cables are usually threaded vertically through a hole in the floor directly under the table (Fig. 1). ...
... There have been several studies on this problem. Several previous studies [2]- [7] utilize a model comprising a simple dipole or monopole antenna driven by a single voltage source that represents the noise source on the PCB. However, these studies assume that the input impedance is purely real and not frequency dependent. ...
Being able to predict radiated emissions before using an accredited laboratory can be both time-effective and cost-effective. This study presents a model for predicting radiated emissions from power converters by measuring the common mode current in the attached cable. When power converters are tested for radiated emissions, the attached cables tend to be thick because of the high currents they carry. Ideally, these cables leave the chamber through connectors in an opening positioned precisely at the middle of the bottom of the turntable in keeping with CISPR 32. However, these connectors are typically not intended for currents higher than 16 A. Consequently, such cables are usually inserted through the side wall of the chamber and are necessarily laid horizontally on the chamber floor. When the turntable is to be rotated with a device on it during a test, the length of the cable attached to the device can exceed 10 meters. The proposed model in this study is based on the transmission line model of a cable loaded with reactive impedance and the assumption that the current distribution along the cable follows a sinusoidal distribution law, much like in dipole antenna theory. The analytic equation of the radiation pattern is derived, and a simplified approximation equation has also been presented. The proposed model also works with short, attached cables and is thus universal. The Maxima software code for automated calculation of the radiated field from measurement data is supplied as supplemental material. The proposed model was experimentally validated by running the fuel cell converter module at 5 kW output power.
... The existing papers focused on the equivalent driven mechanism of the cable antenna [8], [9] and the calculation of near field emission from cables [10]. They did not investigate the detail inside power converters, so the existing techniques did not reveal the mechanisms based on power electronics circuits, printed circuit board (PCB) layout, and switching waveforms. ...
... More understanding and detail analysis on the radiated EMI models for power converters in terms of converter operation principle, PCB layout, and switching waveforms will be presented in this article. For the power electronics systems with long attached power cables, the power converter behaves like a noise source and the attached power cables behave like an antenna [8]. The switching of power semiconductor devices generates excitation voltages on cables. ...
This paper investigates the radiated electromagnetic interference (EMI) due to the voltage between input and output cables in a non-isolated power converter. The radiated EMI model of a non-isolated power converter is first developed and quantified based on circuit topologies, PCB parasitics, switching waveforms, and transfer functions. Second, an antenna model is developed for converter cables based on the antenna impedance and the antenna transfer function. Third, a complete radiated EMI model is developed based on the converters EMI model and the cables antenna model. Fourth, the radiated EMI is analyzed based on the developed model. Finally, two radiated EMI noise reduction techniques: optimizing PCB layout and adding a cross capacitor, are proposed. The developed radiated EMI model and the proposed radiated EMI reduction techniques are verified with both simulations and experiments. The techniques are also extended to other two non-isolated power converter topologies when the radiated EMI is caused by the voltage between the input and output cables.
... Common-mode currents as low as 5 μA induced on a 1-m cable can result in radiated fields that exceed the FCC Class B limit. The physics of this coupling was first described and quantified in [9,10], and refinements to the original model I/O coupling EMI calculator have been developed over the years [14,16,17,19,21]. Electric-field (or voltage-driven) coupling is illustrated in Fig. 7(a). ...
... Magnetic-field (or current-driven) coupling is the result of a mutual inductance between the signal current path and the effective antenna formed by the board and its attached cables, as illustrated in Fig. 7(b). Equations for determining the amplitude of an equivalent common-mode voltage source that drives the cable are derived in [14,19]. Equations for deriving the maximum possible radiated emissions from a board-cable structure driven by a common-mode voltage source are derived and validated in [17,21]. ...
Meeting electromagnetic compatibility (EMC) requirements can be a significant challenge for engineers designing today's electronic devices. Traditional approaches rely heavily on EMC design rules. Unfortunately, these design rules aren't based on the specific EMC requirements for a particular device, and they don't usually take into account the specific function of the circuits or the many design details that will ultimately determine whether the device is compliant. This paper describes a design methodology that relates design decisions to the product's EMC requirements. The goal of performance-based EMC design is to ensure that electronic designs meet EMC requirements the first time the product is tested. More work needs to be done before this concept reaches its full potential, but electronic system designers can already derive significant benefit by applying this approach to products currently under development.
... Most DUTs require at least a power cable, thus including a cable into the NFFFT becomes almost a necessary step in order to estimate the correct far-field in a practical settings. Many authors have treated the emissions of PCBs with attached cables [8][9][10][11][12][13] focusing mainly on the radiation due to the antenna formed by the PCB and cable. However, to analyse a system where the direct PCB radiation and cable radiation coexist, using near-field to far-field transformation, one possible, simple approach is to scan around the entire DUT and cable. ...
... The direct radiation from PCB refers to the radiation from the PCB if there was no cable attached (e.g. trace currents, return currents on the ground plane, currents caused by energy converting from "transmission line mode" into an "antenna mode" by electrical or magnetic excitation [10,16,17] or change in symmetry [18,19]). The cable radiation refers to the radiation due to the current on the cable and the current on the PCB caused by the continuity of current on the cable. ...
Near-field scanning is often used to solve EMC problems. Aside from the purpose of visualization of near-fields, measured near-field data can be used to estimate far-field. One of many challenges associated with using near-field to far-field transform (NFFFT) technique for EMC application is the handling of attached cables. The objective of this investigation is to evaluate different methods to add cable information to the near-field data for far-field estimation. The investigation is carried out using numerical experiments in EMCoS EMC studio, which is a commercial MoM (Method of Moment) tool for EM simulation. Measurement results from a test structure are also presented to validate the simulation results.
... Ke et al. modeled the radiation emission caused by the power bus noise of circuit boards with cables and applied it to various circuit board-cable connection structures [24]. Shim [25] and Deng et al. [26] indicated that the common-mode current induced on a cable connected to the circuit board may be an important source of accidental radiation. Ji et al. [27] pointed out that the degradation of electrical connectors would reduce communication quality. ...
The coupling relationship between space electronics systems is complex, and the signals of optoelectronic load cables are susceptible to interference, especially the early anomalous weak signals on a ground surface used for immediate remote sensing, which are more susceptible to coupling interference between cables. Ensuring a good grounding state for the cable shield is vital for reducing the interference suffered by cables and increasing the electromagnetic compatibility of the system. In this paper, we propose a shielding grounding optimization method for a spaceborne multi-cable shield, including a cable model and parameter extremization and parameter scanning simulation performed using CST, data processing and truth table transformation conducted using MATLAB, and logic expression extraction carried out using Multisim. The method can sort and classify the shielding effects of all the grounding states of multi-cable shields in batches, and ultimately output logical expressions specifying the mapping relationship between the shield grounding state and shielding effect, allowing the optimal shield grounding state to be quickly identified. Finally, the method was applied to a satellite-borne scanning mirror drive control system, and the effectiveness and accuracy of the method were verified by experimental tests.
... An idealized magnetic dipole antenna constitutes of a small currents loop and its radius a meets the inequality: a<<λ . We can derive the vector and magnitude of E-field and H-field radiated from the model [5]- [7]. ...
With highly requirement for electromagnetic compatibility (EMC) target, effective controlling of radiated emission of equipment or subsystem is of considerable significance. An emission equivalent model of Printed Circuit Board (PCB) is set up in this paper. Prediction of resonance characteristics, far field radiation of the PCB is carried out and analysed. Then, a 3-D model of a typical equipment enclosure is set up. Resonance characteristics and radiating characteristics of the enclosure is carried out and analysed. A co-simulation method to predict radiated emission is proposed and an example of co-design of PCB and enclosure using HFSS and Siwave verified this method.
... The resonance frequency can be reduced when the fin is added to the base. However, these fins can increase the amplitude of the EM wave radiated in the far-field, if the fins are extended in the length (unlike the width) [18]. The max. ...
The active/passive heatsinks have recently garnered much attention due to their benefit to keep the temperature of the electronic device and PCB/ICs in a certain range. They are expected both to perform a maximum cooling thermally and to have a minimum of the radiation in electromagnetic terms since it causes electromagnetic interference (EMI) in devices around. In this paper, many studies discussing the EMI performance of natural convection heatsinks in the literature are investigated. Especially in devices operating at high frequencies, these structures behave like semi-antennas if their electrical dimensions are comparable to λ-λ/20 wavelengths. Accordingly, they act as both a monopole and a patch antenna. To eliminate the EMI effect from a heatsink, the grounding, shielding , and filtering techniques are studied. In the literature, the grounding methods are studied up to 2 GHz and it is determined that it provides improvement up to 12 dB. For 1-40 GHz it is possible to have up to 20 dB improvements in EMI by using absorbers and shielding methods. Finally, the effects of heatsink geometry, design parameters, fin-types, and excitation points on RE are discussed.
... The current-driven and voltage-driven models were experimentally validated by investigating common-mode current on the attached cables in Ref. (2), (3). In addition, voltage-driven model was developed to estimate the radiated emissions from the PCB with the attached cables (4) . ...
When a shielded-twisted-pair (STP) cable is connected with a printed circuit board (PCB) via an Ethernet (RJ45) connector, mode conversion between primary-and secondary-common modes occurs at the connector section due to their structural difference that causes the difference in the imbalance factor of the transmission line. In this paper, we investigate the suppression of the mode conversion at the connector section by using a modal-equivalent circuit model based on imbalance matching. We focus on improving the PCB pattern below the shielded Ethernet connector by placing a copper layer on the PCB surface, and the inadequate shielding at the connector section by soldering and wrapping with copper tape. The application of this improvement based on imbalance matching at the connector section makes the imbalance factor of the connector section closer to that of the cable section and results in the suppression of the mode conversion. Based on the concept of imbalance matching, we confirmed the effect of the shield-improved connector with an improved PCB pattern on the suppression of the mode conversion at the connector section through circuit simulation and measurement, and it was validated that the circuit simulation results obtained from the modal-equivalent circuit model agree well with the measurement results.
... Although an equivalent circuit model may reproduce experimental behavior, it cannot be used to develop a fundamental solution to the noise problem. [5][6][7][8][9][10] In general, equivalent circuit models consider the ground as an ideal reference (i.e., an infinite-size conductor with uniform potential). However, if the ground plane has a finite size, the ground potential is no longer uniform, resulting in the generation of various noises. ...
In this paper, we investigate common‐mode (CM) noise caused by a connection to a two‐dimensional finite‐size ground plane. Numerical calculations are conducted to visualize the time variation of potentials that leads to CM noise. A connection of the signal line to the ground plane, which is conventionally used in circuits, causes an imbalance in the circuit that makes the potential of the ground plane fluctuate, which results in CM noise. CM noise does not occur in a symmetric three‐line circuit because the potential of the middle line is always kept at 0 V. Furthermore, the middle line prevents an externally induced potential fluctuation of the ground plane from being converted to a normal‐mode voltage (i.e., CM noise).
... The mechanism can be modeled as a noise source voltage driving common mode current loop. In this study, the noise source voltage is assumed to be approximately equal to the switch node voltage relative to PCB ground [5]. Since the minor difference between the parasitic capacitances from two switch nodes A and B to chamber ground and the mutual influences between the two switch nodes can be neglected, the whole system can be modeled as a noise source voltage driving common mode current loop while the noise source voltage can be calculated using equation (1) based on superposition theorem in linear systems as shown in ...
... An integrated circuit (IC) processing data can act as a leakage source [29] if it produces a signal that includes information with frequency components corresponding to the time variation rate. Higher-frequency components are often propagated through EM coupling to device components that behave as an antenna [30], resulting in spatial radiation of the leakage following the frequency characteristics of the antenna [31,32]. ...
With the rising importance of information security, the neces-sity of implementing better security measures in the physical layer as well as the upper layers is becoming increasing apparent. Given the development of more accurate and less expensive measurement devices, high-perfor-mance computers, and larger storage devices, the threat of advanced attacks at the physical level has expanded from the military and governmental spheres to commercial products. In this paper, we review the issue of infor-mation security degradation through electromagnetic (EM)-based compro-mising of security measures in the physical layer (i.e., EM information se-curity). Owing to the invisibility of EM radiation, such attacks can be seri-ous threats. We first introduce the mechanism of information leakage through EM radiation and interference and then present possible counter-measures. Finally, we explain the latest research and standardization trends related to EM information security.
... The differential emission estimate for the entire board is obtained by taking a root mean square sum of the fields for each net as, | E | total = √ (E seg 1 ) 2 + (E seg 2 ) 2 + ... + (E seg s ) 2 (5) ...
... The power bus structure in PCBs is the main source of electromagnetic radiated emissions. To analyze the principle of a radiated emission and estimate the amount of the radiated emissions from a power bus, numerous theories and modeling methods are presented in [1][2][3][4][5]. In particular, a number of studies have focused on a parallel plate waveguide (PPW) structure for a power bus because it is typically used in PCB applications [6][7][8]. ...
We present experimental demonstrations of electromagnetic bandgap (EBG) structures for the wideband suppression of radiated emissions from a power bus in high-speed printed circuit boards (PCBs). In most of the PCB designs, a parallel plate waveguide (PPW) structure is employed for a power bus. This structure significantly produces the wideband-radiated emissions resulting from parallel plate modes. To suppress the parallel plate modes in the wideband frequency range, the power buses based on the electromagnetic bandgap structure with a defected ground structure (DGS) are presented. DGSs are applied to a metal plane that is connected to a rectangular EBG patch by using a via structure. The use of the DGS increases the characteristic impedance value of a unit cell, thereby substantially improving the suppression bandwidth of the radiated emissions. It is experimentally demonstrated that the DGS-EBG structure significantly mitigates the radiated emissions over the frequency range of 0.5 GHz to 2 GHz as compared to the PPW.
... system-level ESD testing [5], [6] and from testing of PCBs with attached wires is available in the literature [9], [10], but disturbance thresholds for ESD induced fields for individual ICs have not been published, to the best of the authors' knowledge. Full-wave simulation of a complete product, including ICs and PCB details, is not currently possible because of the complexity of the structures, the lack of soft-error models for ICs, and the proprietary nature of information from multiple vendors. ...
High-speed low-power mobile devices are sensitive to electrostatic discharge (ESD)-induced soft errors, such as unwanted reset, lock up, loss of user interface, disturbed displays, etc. ESD can couple via current and fields into the internal cabling, printed circuit board traces but also directly into the integrated circuits (ICs). Many portable devices shield nearly all traces using top and bottom layer ground planes, and they apply effective filters at cable entry points such that direct field coupling to the IC can dominate the system's ESD sensitivity. However, a little information is available on the robustness of ICs against direct ESD transient field coupling. A methodology for determining this robustness was developed and applied to a set of consumer electronic ICs to create an initial robustness database. Custom-made electric and magnetic field probes are driven by a 400-ps rise time transmission line pulser to evaluate 37 different ICs. The investigation showed that 50% of the ICs were disturbed at approximately 33 kV/m for the electric field injection and 142 A/m for the magnetic field injection at this rise time. This methodology can serve as the basis for further investigations of ICs. The database can be used to estimate the likelihood of field-coupled ESD-induced soft errors in electronic products.
... The result backs up the above consideration. Figure 22 illustrates the concept of a radiation model of EMI [20][21][22][23] for such emissions. The digital signals in the device, which include the driving signal of the display, are represented as a source signal and shown in Fig. 22 (a). ...
The use of tablet PCs is spreading rapidly, and accordingly users browsing and inputting personal information in public spaces can often be seen by third parties. Unlike conventional mobile phones and notebook PCs equipped with distinct input devices (e.g., keyboards), tablet PCs have touchscreen keyboards for data input. Such integration of display and input device increases the potential for harm when the display is captured by malicious attackers. This paper presents the description of reconstructing tablet PC displays via measurement of electromagnetic (EM) emanation. In conventional studies, such EM display capture has been achieved by using non-portable setups. Those studies also assumed that a large amount of time was available in advance of capture to obtain the electrical parameters of the target display. In contrast, this paper demonstrates that such EM display capture is feasible in real time by a setup that fits in an attaché case. The screen image reconstruction is achieved by performing a prior course profiling and a complemental signal processing instead of the conventional fine parameter tuning. Such complemental processing can eliminate the differences of leakage parameters among individuals and therefore correct the distortions of images. The attack distance, 2 m, makes this method a practical threat to general tablet PCs in public places. This paper discusses possible attack scenarios based on the setup described above. In addition, we describe a mechanism of EM emanation from tablet PCs and a countermeasure against such EM display capture.
... Cables driven by unintentional sources cause unintentional radiated emissions [1]- [4]. The radiated fields interfere with nearby components, causing functional degradation or failure. ...
The radiated emissions from a partially shielded cable mounted 5 cm above a metal plane have been found to be dominated by the emissions from the 5 cm vertical conductor segments, which connect the cable shield and the signal wires to the metal plane at various locations. An equivalent circuit model has been developed for predicting radiated emissions from the cable. As part of an extension from the developed model, an additional wire is included and pulled back in the test setup. The methodology of modeling is applied to this new setup by adding an additional transmission line for the wire against the metal plane, and by including the mutual inductance between the transmission lines, which accounts for the locations of the transmission lines. The predicted radiated emissions match the full-wave simulated radiated emissions, further validating the
modelling technique that was previously developed. This modelling procedure can be used to determine if a system meets a given radiated emission specification before any actual testing is done. If the radiation is predicted to be excessive then design changes, such as additional filtering, can be modelled before the cabling is built to determine if the changes will allow the system to meet the radiated emissions specification before testing begins.
... Manufacturing high speed electronic products with cost effective and compliance to Electromagnetic Compatibility (EMC) requirements is a huge challenge for design engineers. Printed Circuit Board (PCB) is known to be the main source of the radiated emission ] 1 [ . This radiated emission is prominent at higher frequencies due to ever increasing clock speed of the PCB. ...
An electronic product has to comply with a myriad of EMC requirements before it can be marketed globally. Radiated Emission is one of the EMC requirements which constantly poses a challenge to many circuit designer due to the ever increasing speed of PCB clocks. Consequently, in the product it is essential to investigate, identify, model and predict the PCB radiated emission before compliance test is performed for cost and time saving. In this paper, a simple double layer PCB board is fabricated to investigate the PCB radiated emission. Three PCB configurations are investigated for the level of emissions and to correlate with the common-mode currents. These configurations are PCB without attached cables, with one attached cable and with two attached cables. The radiated emission from each configuration is measured in a semi-anechoic chamber at open circuit and 50 ohm loads. It can be shown that the cables are the major sources of radiated emission due to the common-mode currents flowing through it.
... Many antenna parameters can affect the design procedure such as antenna bandwidth, radiation pattern, size, and manufacturing technology. Several UWB antennas have been introduced such as slot antenna [1], Vivaldi antenna [2], biconical antenna [3], log-periodic antenna, spiral antenna [4], and printed monopole antenna [5,6]. Because of their simple design and omnidirectional radiation pattern, printed monopole antennas are considered one of the most popular antennas in UWB systems. ...
In this article, the radiated emissions mechanism and the variation of radiated emissions level have been analyzed and investigated, respectively, according to the ratio of the horizontal to vertical traces in a bent signal line when a bent signal line on a printed circuit board (PCB) with two attached cables is used.Though many papers concerning two cables attached to a PCB have appeared, it is seen that the two cables can be modeled as a dipole antenna. In addition, it is conjectured from two- port S-parameters that the ratio between the horizontal and vertical traces in a bent signal line leads to the variation in magnitude of common-mode voltage induced as a noise source of the dipole antenna. As the signal line in parallel with the attached cable becomes longer, the radiated emissions level due to the current-driven mechanism becomes more dominant while the contribution from the voltage-driven mechanism remains unchanged regardless of the ratio between two signal lines. Based on the analysis of measured and simulated S-parameters, we propose an alternate and relatively simple estimation method replacing the 3-m measuring method to measure the radiated emissions level and investigate the accuracy of our analysis using commercially available software CST MWS 2006B. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26114
... The direct radiation from the PCB is caused when the transmission line mode current on the PCB excites the PCB causing antenna-mode (in some literature works, known as commonmode) current. This mechanism can be described via electric field and magnetic field excitation [18], [19] or possibly via an imbalance analysis [10]- [12]. Fig. 12 shows the simulated surface current density on front and back of the ground plane of the test structure at 170 MHz. ...
Near-field scanning is often used to solve electromagnetic compatibility (EMC) problems. Aside from the purpose of visualization of near fields, measured near-field data can be used to estimate radiated fields. One of many challenges associated with using near-field to far-field transform technique for EMC application is the handling of attached cables. The objective of this investigation is to evaluate different methods to add cable information to the near-field data for radiated-field estimation. The investigation is carried out using numerical experiments in EMCoS EMC Studio, which is a commercial software tool for EM simulation providing method-of-moments solver. Measurement results from a specially designed test structure are presented to validate the simulation results.
... Because of this, measurement results cannot be used to represent the IC in EM coupling models. Recent research has helped to quantify how ICs couple to the structures on printed circuit boards that serve as antennas resulting in radiated emissions problems [7]. Most lines of electric flux emanating from an IC are captured by the circuit board or nearby metal objects and do not contribute significantly to radiated emissions below 1 GHz. ...
... Direct radiation from the heatsink-PCB structure is just one way that a heatsink can contribute to radiated emissions from an electronic device. Previous work has shown that heatsinks can drive the interior resonances of a shielded enclosure [9], or couple to cables attached to a circuit board resulting in radiated emissions from the cables [10]. ...
Above 1 GHz, heatsinks on printed circuit boards are often large enough compared to a wavelength to be efficient antennas. Tall heatsinks can radiate like monopole antennas, while short, wide heatsinks can radiate like patch antennas. This paper investigates the development of closed form expressions for estimating the maximum possible radiated emissions from a heatsink based on the heatsink size and the maximum voltage
observed between the heatsink and the printed circuit board power planes.
... Addressing the aforementioned issue, this paper presents a novel analysis of EM information leakage from cryptographic devices based on the electromagnetic interference (EMI) theory [10], [13], [14]. From the viewpoint of EMC, the intensity of EM radiation is represented as the product of three factors: Source, Path, and Antenna. ...
This paper presents a novel analysis of electromagnetic (EM) information leakage from cryptographic devices, based on the electromagnetic interference (EMI) theory. In recent years, side-channel attack using side-channel information (e.g., power consumption and EM radiation) is of major concern for designers of cryptographic devices. However, few studies have been conducted to investigate how EM information leakage changes according to device's physical parameters. In this paper, we introduce a cryptographic device model to analyze EM information leakage based on the EMI theory in a systematic manner. This device model makes it possible to acquire the frequency characteristics of EM radiation depending on physical parameters, such as board size and power-line length, accurately. The analysis results show that EM information leakage can be explained by the major EMI parameters such as board size and cable length attached to the board. In addition, we demonstrate that the intensity of EM information leakage from a generic device is also explained by board size and cable length.
Rapid increase in operating frequencies and power density necessitate the importance of examining electromagnetic compatibility/electromagnetic emissions (EMEs) from high-frequency and high-power integrated circuits (ICs). In this paper, a simulation method is demonstrated to study the EME using gallium nitride high electron mobility transistor power amplifier IC chip as a device under test. Simulation model is developed by collaborating a high-frequency structure simulator with a Keysight Advance Design System for simulation of three-dimensional layout of IC. The simulated EME results are verified with experimental measurement results; the hotspots obtained with higher EME as identified by a near-field scanner and simulation results are identical. With this simulation method, optimization is done using a response surface methodology to reduce the EME for the IC chip. It is found that small changes in the IC layout can make a significant difference in the EME. Simulation model developed with RSM optimization technique opens a gateway for the IC industry to investigate EME of their chip design without going through a costly and time-consuming process of fabrication for testing its EME. IEEE
Heat sink is widely mounted on the integrated circuits to optimize thermal performance. Unfortunately, the cavity resonance between heat sink and package substrate could lead to severe radiation problem, causing that the product fail to satisfy the relevant electromagnetic interference (EMI) standards. It is a critical challenge to simultaneously obtain the excellent radiation attenuation and desirable thermal performance. In order to solve the problem, a combination of ring-shaped absorbing material and flat-shaped graphite is proposed in this paper. Based on a typical wire-bonded package, the effect of graphite on mitigating radiation and optimizing the thermal performance is investigated. As the graphite size varies from 20 to 45 mm, temperature reduction 5 °C and radiation attenuation 10 dB absorption bandwidth is realized. The experiment for EMI radiation is conducted in a semianechoic chamber, and the results of simulation and experiment matched well.
Cables attached to printed circuit board (PCB) are widely known source of common-mode radiated emissions (CM-RE). Therefore, it is important to estimate these emissions at the design phase of the electronic device to reduce the product cost and to increase the market sharing for electromagnetic compatibility (EMC) compliance. In this paper, a novel analytical method is proposed to estimate CM-RE from coaxial and twin-lead cables attached to PCB. This analytical method involve to perform two procedures; first, the CM voltage is computed at the cable-board junction based on the degree of change between the imbalance factors of the board and the cables connected to PCB; The second procedure is to estimate the CM-RE based on the equivalent asymmetrical dipole antenna. The effectiveness of the proposed method has been verified by comparing the estimated results with the measurement results taken in a semi anechoic chamber. A good agreement with accuracy of more than 90% was observed for the frequencies from 30 MHz to 1 GHz.
The experimental measurements clearly show electromagnetic noise patterns in a three-line circuit, which represents a two-line circuit with grounding. A new three-line circuit theory reproduces the noise patterns of an electric circuit with grounding, allowing the origin of the noise of the three-line circuit to be understood. In addition, comparing the theoretical calculations of a three-line circuit to the experimental results reveals that electric power is converted to heat over time due to the resistance in the third line. The results demonstrate the importance of reducing the common-mode noise to avoid heat generation in an electric circuit.
In this study, the coupling between the common and normal modes in distributed lines and the resulting electromagnetic noise were considered. The telegraph equations of three distributed lines with the boundary conditions of a lumped circuit reveal the presence of mode-coupling noise. To reduce the coupling noise, the geometrically and electrically symmetric configuration of the three distributed lines is proposed. The simulation results show that the proposed configuration can decrease the mode-coupling noise by a factor of in comparison with that of asymmetric configurations.
This letter introduces a novel resonator-based suppressor to mitigate the noise transfer on the metal plates inside electronic devices. Compared with the traditional method using ferrite-based absorbers, which is inadequate to fully eliminate gigahertz (GHz) noise, the proposed solution can achieve a high-level noise rejection within the desired frequency band in GHz range. The unit cell of the suppressor is composed of multiple quarter-wavelength (λ/4) strip resonators. By simply cascading unit cells in series, a higher-order suppressor can be implemented with wider bandwidth and deeper suppression level. In this letter, a third-order example is demonstrated with the center frequency at 2.48 GHz. Its ability to reduce the amount of noise transfer is experimentally verified, where the maximum suppression level is about 20 dB. Lastly, for a complete demonstration of noise mitigation, the near-field intensity on the test board attached with the noise suppressor is measured.
Common-mode current on attached cables is a typical source for radiated emission. Several models have been made for conversion of the intended differential signal to unwanted common-mode current on cables. In this paper we refine a method for identifying the radiation sources arising from a long microstrip. This method is used to show that the radiated emission from a PCB with attached cable(s) caused by a long trace depends on whether the trace is facing up or down with different result for voltage and current sources.
This paper presents a potential threat of remote visualization for screen displays of various mobile devices used in public spaces via electromagnetic waves (electromagnetic (EM) screen remote visualization). The traditional EM screen remote visualization uses nonportable equipment on a specific target device, and requires sufficient time to estimate the parameters related to information leakage of each target. In contrast, this paper proposes a method that allows for real-time estimation of information leakage parameters without requiring to know the target of remote visualization in details. The proposed method models the process of information leakage for each device, and consequently determines the frequency that leaks screen information faster than ever before. In addition, in this paper, portable equipment and a pseudo-antenna that blends into the mobile environment were used to implement the proposed method. The experiment shows that the screen image can be reconstructed from EM emanation obtained from the areas near some target devices. Furthermore, we discuss the measures against EM remote visualization of mobile devices.
In discussions of radio noise analysis, the noise coupled from radio to its connected antenna is generally neglected. This coupled noise can degrade signal to noise ratio of the radio receiver and it is the root cause of the radio receiver's radiated desensitization, which is a very common electromagnetic interference problem for compacted radio receivers. A unified antenna noise temperature definition is presented in this paper. With the general definition, the overall receiver noise analysis has theoretical integrity. The overall antenna temperature for tightly coupled radios such as cellphones can be measured using the unified antenna noise temperature definition in conjunction with radio conducted, radiated, and a real environment test. The unified antenna noise temperature definition allows the radio engineer to understand the mechanisms of the receiver-radiated desensitization. With the unified antenna temperature definition, radio radiated sensitivity, effective isotropic sensitivity, and total isotropic sensitivity can be mathematically defined.
This paper presents a novel technique for suppressing cable noise currents, the quadruplet-resonator-based ferrite-free choke (QR-based FFC), to eliminate the gigahertz (GHz) electromagnetic interference caused by noise currents flowing on the cable shielding. This problem is difficult to handle with conventional ferrite materials since their permeabilities dramatically degrade when the operating frequency goes up to several GHz. In this paper, with the aid of QR surrounding on the cable shielding, the FFC forms bandstop responses against the noise currents. The corresponding equivalent lumped circuit model is proposed and investigated. Furthermore, the synthesis procedure is established using microwave filter theory. The QR-based FFC can achieve a high-level current suppression at the desired frequency band. This technology is experimentally verified: a given design example is demonstrated at the operating center frequency of 2.57 GHz. The frequency range of 3-dB current suppression is measured from 2.47 to 2.75 GHz (FBW $= $ 10.8%), where the highest suppression level is up to 36 dB. The FFC-added cable also demonstrates a good result in the reduction of far-field radiation, where the reduction level of radiation peak gain is measured as 7 dB compared with that of a bare cable.
Increased inductance values and contact resistance in connector contact surfaces due to degradation of connector contact performance have been reported. In particular, inductance increases while degradation remains minimal. We focus on slight loosening in which increased inductance values are observed without increased resistance values, and investigate the effect of loose connectors on transmission line coupling noise under such circumstances. We find a proportional relation between coupled noise current and frequency. Moreover, we find a proportional relation between the increased inductance value, which depends on the change in connector contact distribution, and the coupled noise current in the transmission line.
Meeting radiated electromagnetic emissions requirements can be a significant challenge for engineers designing today's electronic devices. Traditional approaches rely heavily on design rules. However, the optimum circuit board designs often violate well-known design rules, while successfully controlling radiated emissions. This paper describes the application of a design methodology that relates design decisions to the product's requirements. The methodology takes advantage of maximum radiated emissions calculations to identify the components and circuits capable of causing the system to fail to meet requirements.
In this study, common mode current, a dominant factor of unintentional radiation, on coaxial cable with twisted wire pair (TWP) is estimated. This cable model is a simplified model of a popular combination of balanced and unbalanced circuit, such as printed circuit board (PCB) with TWP. For the convenience of calculation and measurement the coaxial cable is employed as an unbalanced circuit instead of PCB. The estimation method is based on the imbalance theory which focuses on the difference of balance factors between connected circuits, and some effects of TWP are considered. According to the theory the common mode current is proportional to a differential mode voltage at the connecting point. Thus the differential mode voltage is calculated by cable transmission theory with accounting on TWP electrical characteristic and radiation impedance of cables. The estimated result is compared with measurement, and good agreement is obtained. © 2014 The Institute of Electronics, Information and Communication Engineer.
It's well known that a switched-mode power supply is easily to produce electromagnetic radiation emission and often fails in EMC test for its RFI exceeding limits between 30MHz–100MHz. The accurate radiation emission prediction technology is very helpful for a SMPS designer to find the potential problems at earlier stage and remove them in advance. This paper proposes a novel time domain simulation method, electromagnetic field-circuit collaborative strategy (FCS), to predict the far-field radiation emission of a Buck converter. The feasibility and deviation of this method are analyzed firstly. Then a buck converter is modeled and simulated to predict its EMI source and far-field radiation emissions. The effectiveness of this method is verified by comparing the prediction results and the experiment results.
In this paper, we present the results from two sets of independently performed experiments-real and simulated- which adopt the contact failure model. This model provides an explanation of contact failures caused by faulty transmission line connectors for the purpose of investigating the common-mode (CM) current, which is one of the factors that cause noise radiation. In the first experiment, CM current is measured while gradually increasing contact resistance. In the second experiment, the effect on CM current as the number of contact points is gradually decreased is examined. Both experiments are performed within the uplink bandwidth of cable television (CATV) internet transmission. From both sets of experimental results, we conclude that, in order to maintain electromagnetic compatibility of transmission lines in CATV, it is important for the contact boundary of a connector to have low contact resistance, a sufficient number of contact points, and a symmetric contact distribution.
This paper presents an integrated electromagnetic immunity design and diagnosis system for EMI/EMC scenarios assessment and analysis of electronic devices/equipments. The system is capable of modelling and analyzing electromagnetic emission and interference therefore to evaluate the immunity level of devices under test via analytical/numerical methodologies. It will also be customized so that it can be used for the design verifications and parameter calculation.
The highly frequent switching of semi-conductor devices in power converters is often the source of significant conducted and radiated electromagnetic interference (EMI). In order to understand how radiated EMI is emitted from the noise source, this paper firstly analyzes the generation of EMI currents of a power converter, and then explains that the far-field radiated EMI emission of a power converter is due to the radiation of common-mode (CM) current on attached cables, which is driven by the electric near-field coupling between the printed circuit board (PCB) and the attached cables of the converter. Based on this idea, an estimate model of the far-field radiated EMI emission of a power converter is developed. By using transverse electromagnetic (TEM) cell measurements and full wave numerical calculations, the far-field radiated EMI emissions of a Buck converter with different cable lengths are estimated. The estimated results are compared with the measured results from 3–m semi-anechoic chamber tests with the Buck converter, confirming the validity of the model.
Recently, for the electrical devices operating at high frequency, suppression of electromagnetic radiation field at high-frequency bands is required under EMC guidelines. EMC test measurements and suppression methods for electromagnetic radiation generated at high-frequency bands are under investigation. But, discussion on the electromagnetic radiation resulting from interconnected devices is limited. So, we focus on an effect of connectors which decreases contact performance on electromagnetic radiation when devices are interconnected with each other. In previous studies, we have shown the effect of loose contact of a connector on electromagnetic radiation. These studies have shown that inductance and resistance value at a connector contact boundary are increased by loosening a connector and electromagnetic radiation is increased by changes of values of those high-frequency circuit elements. To investigate the mechanism of increase on electromagnetic radiation field by loose contact connector, we analyze the dominant element of high-frequency circuit to cause electromagnetic radiation. Moreover, to acquire contact requirements for a connector in order to suppress electromagnetic radiation, we compare the impact of inductance and resistance on electromagnetic radiation under different frequencies.
Common-mode current is a significant source of radiated emissions from power inverters. In an ideal power inverter, the currents flowing in one direction on the wires between the inverter and the load are exactly equal to the currents flowing in the opposite direction in the same wire bundle. Unfortunately, imbalances in the switching components and circuit geometry can cause the electrical potential of the wire bundle to change with time resulting in common-mode currents. Most inverters employ pulse-width modulated switching at frequencies below 100 kHz. Balancing an inverter at low frequencies without affecting the performance or efficiency of the inverter can be challenging. However, radiated emissions are more likely to be a problem at higher frequencies (e.g. >30 MHz). One method for reducing common-mode current emissions at high frequencies is through the use of common-mode or differential-mode filters. Common-mode filtering can add significantly to the cost and weight of an inverter. Effective high-frequency differential-mode filtering can be difficult to implement without impacting the inverter performance, and imbalances in differential-mode filters can actually increase common-mode currents. This paper introduces the concept of a balancing network to reduce the common-mode currents on power inverter cables above 30 MHz. Balancing networks are relatively inexpensive to implement and can be more effective than common-mode chokes or ferrites. An experimental test set-up is used to demonstrate the effect of a balancing network on the common-mode current, differential-mode current and the common-mode rejection ratio on a balanced cable with an imbalanced termination. The results show that a balancing network reduces the common-mode noise currents significantly more than the differential-mode signal currents. This balancing network is also evaluated using a 3-phase brushless DC motor driver to verify its effectiveness in a real application.
Expert system algorithms that analyze printed circuit board designs, anticipate EMC problems, and help designers to correct these problems are being developed by the EMI Expert System Consortium at the University of Missouri-Rolla. This paper reviews the basic structure of the EMI expert system and describes newly developed algorithms.
A procedure for diagnosing and modeling radiation from printed
circuit boards with attached cables is presented through a case study of
a production model electronic control unit. Procedures for determining
EMI antennas, IC sources, and mechanisms by which noise is coupled from
the IC source to the antenna are suggested
Fundamental mechanisms leading to common-mode radiation from
printed circuit boards with attached cables have been studied. Two
primary mechanisms have been identified, one associated with a
differential-mode voltage that results in a common-mode current on an
attached cable, and another associated with a differential-mode current
that results in a common-mode current on the cable. The two mechanisms
are demonstrated through numerical and experimental results
Parasitic inductance in printed circuit board (PCB) geometries can
detrimentally impact the electromagnetic interference (EMI) performance
and signal integrity of high-speed digital designs. This paper
identifies and quantifies the parameters that affect the inductance of
some typical PCB geometries. Closed-form expressions are provided for
estimating the inductances of simple trace and ground plane
configurations
Fundamental EMI source mechanisms leading to common-mode radiation
from printed circuit boards with attached cables are presented in this
paper. Two primary EMI source mechanisms have been identified: one
associated with a differential-mode voltage and another associated with
a differential-mode current, both of which result in a common-mode
current on an attached cable. These mechanisms can he used to relate
printed circuit layout geometries to EMI sources. The two mechanisms are
demonstrated through numerical and experimental results, and an example
from a production printed-circuit design is presented
Radiation from cables attached to printed circuit boards and
shielding enclosures is among the primary concerns in meeting FCC Class
A and B limits. The finite-difference time-domain (FDTD) method can be
employed to model radiation from printed circuit boards and shielding
enclosures with complex geometries, but difficulties in modeling wires
and cables of arbitrary radii are encountered. Modeling the wire by
setting the axial component of the electric field to zero in the FDTD
method results in an effective wire radius that is determined by the
mesh discretization. Neglecting the wire radius in applications, such as
electromagnetic interference (EMI) or printed circuit board modeling,
may result in gross errors because near-field quantities are typically
sensitive to wire thickness. Taflove et al. (1988) have developed a
subcellular FDTD algorithm for modeling wires that has been shown to
work well for plane wave scattering. The method uses a quasistatic field
approximation to model wires with a well defined radius independent of
the mesh dimensions. The wire model is reviewed and investigated for
application to common-mode radiation from cables attached to printed
circuit boards, where the source is often a noise voltage at the
connector. Also investigated is energy coupling to attached cables
through enclosure apertures resulting in common-mode radiation from the
cable. The input impedance for a center-fed dipole antenna, as well as a
monopole connected to a conducting half-sheet, is computed with FDTD
methods and compared to moment method input impedance results. A
simulation of a shielding enclosure with an attached cable demonstrates
the utility of FDTD analysis in modeling common-mode radiation
Thesis (Ph. D.)--University of Glasgow, 1994.
Thesis (Ph. D.)--University of Missouri--Rolla, 2004. Vita. Includes bibliographical references. "The papers in this dissertation describe algorithms and techniques developed for the University of Missouri-Rolla PCB (Printed Circuit Board) EMI (ElectroMagnetic Interference) Expert system. The topics discussed in this dissertation are focused on the estimation of the radiated emissions from printed circuit boards and power bus noise."--Abstract, p. iv.
Radiated emission algorithms for a printed circuit board EMC expert system are described. The expert system mimics the thinking processes that human EMC engineers would use to analyze circuit boards and make design recommendations. Working with limited information about the enclosure, cables or the exact nature of the signals, the expert system evaluates different structures on the printed circuit board, looking for potentially strong radiated emission sources. Results obtained from the analysis of a sample printed circuit board are provided to demonstrate how the expert system quickly identifies problems that would otherwise be difficult to locate.
Two models for evaluating the common-mode current on a printed circuit board with a narrow ground plane are compared theoretically and experimentally. One model is the ground inductance model; while the other is a new model we call the "imbalance difference model". The structure of the new model is simpler and more convenient for field application. The theoretical equivalence between the two models is demonstrated analytically, and numerical results agreed for two models to the level of 2 dB with experiments made in an anechoic chamber.
The paper presents results which demonstrate that radiated
emissions from heatsinks are reduced by an amount that depends upon the
distribution and impedance of the grounding structure. Results are also
presented which show the effect on radiated emissions of the presence of
conductors (e.g. PCB tracks) passing under the heatsink. The presence of
conductors reduces the effectiveness of the heatsink grounding but, in
most cases, emissions at high frequencies do not exceed those without
conductors attached. Available: http://eprints.whiterose.ac.uk/97224/
Several researchers have proposed that a primary source of
emissions from digital devices is due to the partial inductance of the
return trace on printed circuit boards. In this “current driven
model,” RF currents derived from the nanosecond rise time of
periodic signals such as clocks create a voltage across the return due
to this inductance. This paper reports on an experimental verification
of this model, but points out apparent limitations-at frequencies above
a certain point, internal characteristics of integrated circuits such as
I<sub>dd</sub> delta appear to dominate the emissions, at least in the
circuits examined
External cables are one of the major sources of radiated
emissions. Theoretical and practical effects of cable shielding, and the
use of ferrites have been analyzed in previous studies under test
conditions such as noise source, cable, termination setup's etc. We have
looked at cabling effects from a practical point of view. We measured
radiated emissions of a typical IT device with Ethernet and RS232
connections under a variety of conditions. We varied cable shielding,
shield grounding, used ferrites at different locations and compared the
results. The results show that shield type and grounding have a more
significant impact on radiated emissions than use of ferrites, with the
exception of internal components (filtered connectors)
Common mode radiation caused by common mode currents has been
analysed using transmission line and circuit theory. An important aspect
is the derivation of the most important designable parameter, the
asymmetry of a transmission line. This asymmetry has a direct impact on
the common mode current amplitude. It is shown that common mode
radiation can be reduced by creating a mechanically viewed, asymmetric,
transmission line. This reduction can be predicted very accurately.
Radiated emission measurements on several practical configurations, such
as PCB transmission lines with large ground planes, shunt- and guard
traces, striplines, gridded ground planes and ground planes with a slit,
support the theoretically developed statements: the measurement results
are in accordance with the theoretically obtained data
A derivation of the inductance of a large ground plane is given.
Some practical situations, such as the ground inductance of bilayer and
multilayer printed circuit boards (PCBs) and the impact on the common
mode radiation, are described. The ground inductance which results in a
much higher ground impedance than only the AC resistance does is
determined. The inductance of a PCB track and therefore the radiated
emission level can be lowered by broadening the track to a plane or
creating a better coupling by reducing the distance between signal and
return track. A multilayer PCB is better than a bilayer PCB. The net
result is a factor of 10 (=20 dB) lower ground impedance per layer
doubling
In today's high performance computers the need to cool the CPU and
other VLSI devices with attached heatsinks is very common. The heatsink
geometry is usually driven by the thermal requirements in conjunction
with the device packaging needs. As the processor speeds increase the
die power dissipation also increases, leading to an increase in the
preferred heatsink size. In this paper the variations in the radiation
characteristics of heatsinks are examined with respect to their
geometries by use of a three dimensional finite difference time domain
(FDTD) technique
Owing to their complex geometry, large heatsinks, such as are
commonly used in power converters and motor drive systems, may exhibit
electromagnetic resonances which enhance RF radiation characteristics
within the frequency range covered by current EU EMC regulations. Such
effects are investigated using the finite-difference time-domain method
and compared with measurements
The subject is a strip Iine formed of a strip and a parallel ground plane separated by a dielectric sheet (commonly termed "microstrip"). Building on the author's earlier papers all the significant properties are formulated in explicit form for practical applications. This may mean synthesis and/or analysis. Each formula is a close approximation for all shape ratios, obtained by a gradual transition between theoretical forms for the extremes of narrow and wide strips. The effect of thickness is formulated to a second-order approximation. Then the result is subjected to numerical differentiation for simple evaluation of the magnetic-loss power factor from the skin depth. The transition formulas are tested against derived formulas for overlapping narrow and wide ranges of shape. Some of these formulas are restated from the earlier derivations and others are derived herein. The latter include the second-order approximation for a narrow thin strip, and a close approximation for a narrow or wide square cross section in comparison with a circular cross section. Graphs are given for practical purposes, showing the wave resistance and magnetic loss for a wide range of shape and dielectric. For numerical reading, the formulas are suited for programming on a digital pocket calculator.
The parasitic ground-plane inductance is responsible for
common-mode radiation, as one of the major unwanted radiation mechanisms
of printed circuit boards. For the computation of the common-mode
inductance simple relations are known for the case that the trace is
centered above the ground plane. In this paper the increase of the
ground-plane inductance for arbitrary trace-to-edge distances is
studied. From the exact analytical result obtained by complex analysis a
much simpler real-valued relation is derived which allows one to set up
dimensioning equations for the minimum distance of the trace to the
board edge. The inductance increase correlates quite well with published
measurement data for the common-mode current increase. A parameter study
for different dimensions of the board provides a quantification of the
potential electromagnetic interference (EMI) level
A knowledge of the net inductance of the ground plane can aid in
the analysis and investigation of printed circuit board emissions. In
this paper, we present a method, based on the concept of partial
inductance, to determine the net inductance of the ground plane
associated with a microstrip line. This method is based on a previously
derived expression for the current density on the ground plane. We show
calculations for the net, self-partial, and mutual-partial inductance of
the ground plane for various trace geometries of practical interest. We
also illustrate how the classical transmission line inductance of a
microstrip line can be obtained from the concept of partial inductance.
Comparisons to different experimental results are also given
The electromagnetic radiation from a VLSI chip package and
heatsink structure is analyzed by means of the
finite-difference-time-domain (FDTD) technique. The dimensions of a
typical configuration call for a multizone gridding scheme in the FDTD
algorithm to accommodate fine grid cells in the vicinity of the heatsink
and package cavity and sparse gridding in the remainder of the
computational domain. The issues pertaining to the effects of the
heatsink on the overall radiative capacity of the configuration are
addressed. Analyses are facilitated by using simplified heatsink models
and by using dipole elements as sources of electromagnetic energy to
model the VLSI chip. The potential for enhancement of spurious emissions
by the heatsink structure is illustrated. For heatsinks of typical
dimensions, resonance is possible within the low gigahertz frequency
range. The exploitation of the heatsink as an emissions shield by
appropriate implementation schemes is discussed and evaluated
It is shown that radiated emissions due to common-mode currents on
printed circuit board lands can greatly exceed those due to
differential-mode currents. It is concluded that predictions of radiated
emissions based solely on differential-mode (transmission line) currents
can bear little, if any, resemblance to actual measured emissions.
Therefore, radiated emission prediction models that use only
differential-mode (transmission-line) currents and ignore common-mode
(antenna) currents are not adequate for the prediction of radiated
emissions from printed circuit boards (as well as cables)
Development of radiated EMI estimation algorithms for PCB EMI expert systems Hwan-Woo Shim was born in Kyungpook Province, Korea, in 1968
- H W Shim
H. W. Shim, " Development of radiated EMI estimation algorithms for PCB EMI expert systems, " Ph.D. dissertation, Univ. Missouri-Rolla, May 2004. Hwan-Woo Shim was born in Kyungpook Province, Korea, in 1968. He received the B.E. degree from Kyungpook National University, Daegu, Korea, in 1991, the M.S. degree from Korea Advanced Insti-tute of Science and Technology, Daejeon, Korea, in 1994, and the Ph.D. degree in electrical engineering from the University of Missouri–Rolla, in 2004.
Fast Cap User's Guide.
- K Nabors
- S Kim
- J White
- S Senturia
Quantitative evaluation of common-mode radiation from a PCB based on imbalance difference model
- T Watanabe
- O Wada
- A Namba
- K Fujimori
- S Matsunaga
- R Koga
quantitative evaluation of common-mode radiation from a pcb based on imbalance difference model
- watanabe