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M-QAM Six-Port Modulator Using Only Binary Baseband Data, Electrical or Optical
Abstract
A new circuit architecture for a direct-carrier six-port modulator is proposed. The proposed architecture uses parallel binary-valued baseband signals to control binary-valued impedance loads for generation of rectangular M-QAM modulation. A theoretical model of the proposed modulator is also derived. A prototype modulator for 64 quadrature amplitude modulation is designed and fabricated for a center frequency of 2.5 GHz for verification of the proposed architecture. The measurements verify the theory and show that good performance can be obtained with the proposed architecture. The proposed modulator does not require any digital-to-analog converter and can operate with both electrical and optical control signals.
... The device allows to integrate the polarization control system and the modulation system in a single structure driven only by four variable impedances, providing a more compact circuit with lower cost and power consumption. The proposed architecture is a variant of the six-port modulators [12], [13], [14], [15] in which four variable loads control the magnitude and phase of the carrier signal at the output port. Our proposal provides two output ports that feed a dual-port antenna, and then, the four variable loads control the envelope and the polarization of the transmitted signal. ...
... Hence, replacing (13) in (12), ...
... It is noted that, considering there is only one output, the definition (23) can be used to calculate the efficiency of the six-port modulators and compare them with this seven-port modulator. For example, in [13] the theoretical efficiency results η = 38% (see (42) in [13]), and in [12] the theoretical efficiency is 50%. To the best of our knowledge, there are not any six-port modulators with a theoretical efficiency greater than 50% in the current literature. ...
This paper presents a seven-port modulator capable of switching the polarization state of the transmitting signal. Similar to the six-port modulator, the proposed device modulates the carrier signal through the reflection coefficients generated by four variable loads. The additional seventh port allows feeding two antennas or a dual-port antenna. The loads control both the complex envelope and the polarization of the transmitted carrier signal. The mathematical model of the device, developed in the paper, is applied to analyze its performance and different modes of operation. For validation, a prototype is manufactured for a center frequency of 1575.42 MHz. It is used to generate M-QAM modulation at different polarizations. The signals recorded at the output of the prototype show good agreement with the values predicted by the model.
... Six-port circuits are potential candidates for 5G wireless communication due to their broadband capability and easy scalability to millimeter-wave frequency. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In conventional quadrature modulator, the mixing action introduces nonlinear distortions, which become severe with quadrature imbalances. [18][19][20][21] Six-port modulator (SPM) on the other hand does not require any mixers for modulating in-phase (I) and quadrature-phase (Q) component of baseband data to radio frequency (RF) carrier. ...
... The working of SPM is based on passive six-port correlator (SPC) with ports terminated with variable loads. 2,[5][6][7][8][9][10][11][12][13][14][15][16][17] These variable loads generate variable reflection coefficients at each port of SPC controlled by I and Q data. The I and Q information is then translated to RF carrier while reflecting from various ports and correlated by the passive SPC. Figure 1 shows transmitter line-up with SPM as well as conventional modulator. ...
... 3,4 The variable loads terminating different ports of SPC in Figure 1C can be realized using PIN diode capable of operating as switches or transistors. 2,5,7,[15][16][17] An alternate approach is to use Schottky diode presenting variable load by controlling its bias voltage. [8][9][10][11][12][13][14] The switch based configuration is limited to low speed operation and its complexity scaled up with the higher order quadrature amplitude modulation (QAM) scheme. ...
This article presents digital correction for hardware imperfection in mixer‐less six‐port modulator. A passive six‐port network correlates radio frequency carrier reflected from its different ports. If the reflection coefficients at these ports are controlled by in‐phase and quadrature‐phase baseband data, the modulated information is translated directly over the radio frequency carrier without any mixing action. However, the six‐port modulator has several hardware impairments resulting into linear and nonlinear distortion. This article presents a digital characterization and distortion mitigation scheme for six‐port modulator using new quadrature interference memory polynomial model and its variant. As a proof of concept, a prototype of digitally assisted six‐port modulator is designed to modulate QAM data to radio frequency carrier at 2.0 GHz. The measurement results show the capability of modulating 16 and 64 QAM data with very low EVM less than 1.2% after employing proposed digital correction scheme.
... The carrier leakage is very prominent in [16] that uses only four ports for implementation and measurement. The method based on phase shifters together with differential baseband signal is adopted in [18]- [21], [26], [28], and [29], however, the carrier leakage cannot be suppressed completely from the modulated RF signal if the diodes are not identical, the electrical length of the transmission line implementing 90°phase shift is not optimal at the operating frequency, or the six-port correlator is not ideal. Second, the crosstalk between the in-phase and quadrature-phase (I/Q) channels is another factor that influences the system performance, and it mainly results from the nonideal characteristic of the six-port correlator, or the variable loads. ...
... Though the diodes [18] and the transistors [24] feature high-speed performance for the SPM, they exhibit nonlinearity and memory effects similar to power amplifiers (PAs) [31]- [34] which negatively impact the SPM performance. Notably, the architecture [29], [30] avoids the nonlinearity issue of the reflection coefficients from the impedance loads in that only binary baseband data are utilized, however, the increased number of the power dividers (PDs) and transistors make the circuit very complicated. Finally, only QPSK and QAM signals have been tested in the SPMs [9]- [30]. ...
... Since carrier leakage has a negative impact on the final system performance, the measured results based on a DPD model (DPD-3) in (29) are compared with those based on the DPD-1 model in (22) to verify that the coefficient ε 0 is used to suppress the carrier leakage. Complete set-up based on the signal generator from Keysight Technologies as a RF modulator. ...
In this paper, a new method to design a digitally assisted and spurious-free direct carrier mixerless modulator based on the six-port correlator is proposed. The calibration of the modulator based on modified Cartesian memory polynomial (MCMP) is used to linearize and mitigate hardware impairment of the whole system. The modulation and the up conversion are performed by using the variable loads controlled by the differential in-phase and quadrature-phase baseband voltages together with common-mode voltages. The proposed MCMP is able to compensate for nonlinearity, frequency responses, residual carrier leakage, crosstalk between the in-phase and the quadrature-phase data. The proof-of-concept of digitally assisted mixerless modulator is developed and its performance is assessed at 2.6 GHz with modern communication signals. The error vector magnitudes between the input ideal baseband signals and the up-converted radio frequency signals are all between 2% and 4%. The residual carrier leakage, which remains present after imperfect suppression through hardware means, degrades the overall system performance and it can be suppressed completely by means of the proposed memory polynomial model.
... However, a natural way to solve these problems is to go back to Maxwell's equations, that is, the electromagnetic wave approach. We Figure 2. Six-port modulator for direct digital modulation [12]. need a unified wave approach to do digital modulation and transmission. ...
... During recent years, we have been doing research on the socalled six-port radio architecture for wireless communication purposes [6,[12][13]. Our recent research results [12] have shown that binary baseband data, either electrical or optical, can be used directly to modulate the sinusoidal wave from the local oscillator to generate high order modulated wideband RF signal, using a six-port modulator without any digital-toanalog conversion. ...
... During recent years, we have been doing research on the socalled six-port radio architecture for wireless communication purposes [6,[12][13]. Our recent research results [12] have shown that binary baseband data, either electrical or optical, can be used directly to modulate the sinusoidal wave from the local oscillator to generate high order modulated wideband RF signal, using a six-port modulator without any digital-toanalog conversion. The modulation is realized by wave interferometry of the transverse electromagnetic mode (TEM) waves in a six-port correlator implemented using microstrip lines in the quasi-TEM mode [9]. ...
This article intends to answer the question how to achieve wireless data rates that can catch up with current Internet speed, from a basic physics point of view. It is shown that the traditional electric circuit theory and design methodology that have been used for generations are unfortunately not adequate for wireless communications in the future. Instead, disruptive approaches such as six-port modulators for processing of electromagnetic waves and optical pulses should be employed to push up the wireless data rate above 100 gigabits per second. The key variables to consider for high speed digital communications are bandwidth, modulation order and signal-to-noise ratio. In principle, it should be possible to achieve a wireless data rate at 100 Gbps within the frequency spectrum below 20 GHz.
... Furthermore, this device has an ability to measure two complex signals. This feature can be further applied in the purpose of signal modulation such as a quadrature phase shift keying (QPSK) and 16-quadrature amplitude modulation (16-QAM) as reported in [1] [2] [3] [4] [5]. ...
... Previous bulky, complex and narrowband multi-portbased modulator gave motivation to design a compact and simple multi-port modulator with low manufacturing cost and good wideband performance. The reported narrowband designs utilizing three couplers and one power divider in [1] [2] [3] [4] consider only single operating frequency of 60, 2.4, 2.5 and 7.5 GHz, accordingly. Meanwhile, there are improved bandwidth performances proposed in [5] and [6] with almost similar operating frequency of 3.1–4.8 ...
... Unfortunately, the bandwidth performance is still inadequate. Furthermore, the use of branch line couplers in the multi-port network in [2] [3] [4] and [5] lead to a large size device, which not favorable in the current trend. Whilst, design in [6] is formed by the power divider and quadrature hybrid implemented using one and two substrates, respectively. ...
The design of the quadrature phase shift keying (QPSK) modulator by using a multi-port network is proposed in this article for the use in wireless communication applications. The multi-port network is in the form of multilayer microstrip-slot technology. This multi-port network is composed of three 3-dB rectangular-shaped directional couplers with virtual stubs and an equal power division divider with in-phase characteristic. The design is performed by applying a full-wave electromagnetic simulation software, CST Microwave Studio (CST MWS). Keysight's Advanced Design System (ADS) is applied in analyzing and evaluating the QPSK constellation of the proposed modulator. This comparatively small size of proposed design has been fabricated, and its wideband performance of 2 to 6 GHz is verified.
... The area in Fig. 5(a) defines the coverage of the modulator that it can be used to generate different modulations. The magnitude of the transfer function defines the efficiency of the modulator as (6). On the other hand, Fig. 5(b) shows that the magnitude of the reflection coefficient |S 11 | dB is always lower than −10 dB for this set of observations. ...
... • EVM = 6.99% for 16-QAM constellation in [5]; • EVM = 7% for 64-QAM constellation in [6]; • EVM = 6.5% for 16-QAM constellation in [7]. In all the cases, the error is lowered when the number of training data in the calibration is increased. ...
... Die Ergebnisse des im vorherigen Abschnitt beschriebenen Sechstor-Abwärtsmischers, insbesondere im Hinblick auf die einfache schaltungstechnische Realisierung und die gute Modellierbarkeit motivieren die Anwendung der Sechstor-Architektur auf die I-Q-Aufwärtswandlung. Im Gegensatz zu den Abwärtsmischern wurden bisher keine integrierten Sechstor-Aufwärtsmischer im Millimeterwellenbereich demonstriert, mit Ausnahme des hier beschriebenen Mischers aus [Rie6]. Allerdings wurden diverse Aufwärtsmischer mit Sechstoren auf Leiterplatten mit FR4-oder Keramiksubstraten und mit verschiedenen diskreten HF-Dioden oder Transistoren als Reflektoren veröffentlicht, z.B. mit HF-Schottky-Dioden [112], [113] oder mit GaAs-Transistoren [114], [115]. In den meisten Halbleiterprozessen auf Basis von Silizium sind diese Arten reflektiver Lasten jedoch nicht verfügbar, was ein Grund für den Mangel an integrierten Sechstor-Aufwärtsmischern sein könnte. ...
... Die Probleme des entworfenen Sechstor-Aufwärtsmischers beschränken sich im Wesentlichen auf die niedrige LO-Unterdrückung, trotz der verwendeten Unterdrückungstechnik mit den /4-Leitungen und den symmetrisch ausgesteuerten Reflektoren, die in [113] vorgestellt wurde. Von ähnlichen Problemen wurden auch in [114] und [112] berichtet. Eine tiefere Analyse der Ursache und eine Optimierung des Sechstors hinsichtlich ...
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
For meta data and other details see the entry on the Qucosa publication server of TU Dresden: https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-748860
... The six-port usually feeded by two signals generated at the outputs four different phase arrangement [16]. Since the last 40 years, the six-port or multiport discriminator has been used for many applications such as direct conversion receivers [17][18][19][20][21][22][23][24]. This technology was used to implement a direct modulation scheme for up-conversion [25,26]. ...
... The mathematical model can provide a spectrum of vital detection. By substituting (19), (20), (21) and (22) into (23), (24), (25) and (26), we obtain I 1 , I 2 , I 3 , and I 4 , respectively. Further analysis of both harmonics and intermodulation (HInt) is given by the term ...
A harmonically driven bio‐radar based on the technique of a multiport interferometer (six‐port) technique is proposed and studied in order to improve the performance of vital signs monitoring. The feasibility of estimating cardiopulmonary parametric signatures by deploying a harmonic multiport interferometer radar is presented. This scheme is helpful to reduce the noise floor and the effects of undesirable parasitic harmonics of breathing and intermodulation. A theoretical analysis is developed to explain why a better heart‐beat detection using the proposed harmonic six‐port radar architecture can be achieved. The well‐known null point problem usually encountered in such radar detections of heart‐beating signs is alleviated by the insertion of a fixed 45° phase shift between the two different frequencies in the six‐port discriminator without an actual phase‐shifter. Simulations are carried out to investigate detection accuracy and sensitivity issues for monitoring the vital signs by cancelling the breathing harmonics and intermodulation products. The concept is then validated by the measured results of an experimental prototype using the proposed harmonic six‐port radar platform operating at 12 GHz (fundamental) and 24 GHz (harmonic).
... Hence, replacing (13) ...
... It is noted that considering there is only one output, the definition (23) can be used to calculate the efficiency of the six-port modulators and compare them with this seven-port modulator. For example, in [13], the theoretical efficiency results in η = 38% (see [13, eq. (42)]), and in [12], the theoretical efficiency is 50%. ...
This paper presents a seven-port modulator capable of switching the polarization state of the transmitting signal. Similar to the six-port modulator, the proposed device modulates the carrier signal through the reflection coefficients generated by four variable loads. The additional seventh port allows feeding two antennas or a dual-port antenna. The loads control both the complex envelope and the polarization of the transmitted carrier signal. The mathematical model of the device, developed in this paper, is applied to analyze its performance and different modes of operation. For validation, a prototype is manufactured for a center frequency of 1575.42 MHz. It is used to generate M-quadratic-amplitude modulation at different polarizations. The signals recorded at the output of the prototype show good agreement with the values predicted by the model.
... Six-port network can also be considered for the modulation[5], however, we focus on the two-port network due to its simplicity.© 2023 Institute of Electrical Engineers of Japan. ...
Multiple‐Input‐Multiple‐Output (MIMO) systems are widely used to enhance the system capacity in wireless communications systems. The complexity and the cost for implementing the multiple radio frequency‐chain (RF‐chain) increases proportional to the number of signal streams. Therefore, so‐called load modulating single‐RF MIMO system is one promising technology in the practical aspects. Load modulating single‐RF MIMO can utilize two‐port network for controlling the load and the desired signal can be generate by loading proper set of impedance. In this paper, the optimization method for choosing the two‐port network impedance solution that is robust to the impedance noise is proposed and the simulations are conducted to verify the robustness. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
... The 5G technology is expected to become key supporting assets for industrial communications with superior performance in high data rate and low latency [5]. In addition to that, in [22][23][24][25], the Six-port technology is researched. With simplified modulation and demodulation using direct baseband data conversion, it is targeting at ultra-low latency (<1 ms) and high-speed (>10 Gbps) communication in the industry. ...
Plant Factory is a newly emerging industry aiming at transforming crop production to an unprecedented model by leveraging industrial automation and informatics. However, today’s plant factory and vertical farming industry are still in a primitive phase, and existing industrial cyber-physical systems are not optimal for a plant factory due to diverse application requirements on communication, computing and artificial intelligence. In this paper, we review use cases and requirements for future plant factories, and then dedicate an architecture that incorporates the communication and computing domains to plant factories with a preliminary proof-of-concept, which has been validated by both academic and industrial practices. We also call for a holistic co-design methodology that crosses the boundaries of communication, computing and artificial intelligence disciplines to guarantee the completeness of solution design and to speed up engineering implementation of plant factories and other industries sharing the same demands.
... Sensors 2020, 20, x FOR PEER REVIEW 5 of 44 This topology has been chosen because resistors cannot be integrated in RWG. The top of the multi-port is a simple metallic plate. ...
Recent advances in millimeter wave technologies, both in component and system design, in line with important size and cost reductions, have opened up new applications in ultra-high-speed wireless communications, radar and imaging sensors. The paper presents the evolution of millimeter wave circuit and modules fabrication and characterization technologies in the past decades. Novel planar low-cost fabrication technologies have been successfully developed in this period. In combination with the standard rectangular wave-guide technology, these offer great opportunities for prototyping and testing of future millimeter wave transceivers or front-ends, which integrate antenna arrays, down-converters, modulators, amplifiers, etc., in a compact fixture. The paper uses, as a suggestive example, the evolution of the multi-port interferometric front-ends implementation from millimeter wave bulky components and systems to miniaturized and high-efficient ones. Circuit and system designs are carefully done to avoid (as much as possible) complicated calibration methods or difficult post-processing of baseband data. This requires an increased effort in design and fabrication, but it allows miniaturization, low-power consumption, while keeping very good overall performances. Useful and straightforward laboratory characterization techniques of circuits and systems are described in detail.
... However, it is difficult to realize such loads at microwave frequencies. Most of the previous works have used transistors [19], diodes [8] and switches [20][21][22] as variable loads and have succeeded to construct modulators Fig. 4 a The Wiener-Hammerstein model, b output spectrum of outphasing system with a linear filter before or after nonlinear block limited to a finite number of constellation points like MQAM modulations. In addition, some of the loads used are sensitive to the power of local oscillator (LO) [8]. ...
In this paper, a simple and efficient architecture for implementation of multilevel outphasing systems is presented. The architecture consists of a six-port modulator and a Doherty power amplifier in each outphasing branch. Pin diodes are used as variable impedances of the six-port modulator and their parasitic elements are analytically compensated. A prototype of the variable load is fabricated and the results show the effectiveness of compensation method to prepare pin diodes as variable loads for a six-port modulator. As a proof of concept, a standard 2.4 GHz Doherty power amplifier is designed with 65% efficiency at peak power and 46% efficiency at 6 dB back off. The proposed system is simulated in advanced design system using a 20 MHz WLAN signal with 7.5 dB PAPR and 5 level outphasing. Simulation results show 31.6% power added efficiency for the Doherty-Outphasing system.
... The multiport circuit can be also used in the front-end design to operate at the frequencies where active components are not yet available in the market. In order to operate as demodulator or modulator, it requires only the use of power detectors or switches [28][29][30][31][32]. Therefore, research activities can be validated by front-end prototyping measurements, years before standard technologies become available. ...
The multiport circuit theory was initially developed in the 1970s by scientists for accurate automatized measurements of the complex reflection coefficients, in microwave network analysis [1–3]. These multiport pioneers highlighted its usefulness in microwave low-cost circuit characterizations (S-parameters).
This paper presents the design of a four-branch reduced-complexity load-modulated MIMO transmitter. The transmitter is designed to operate at 3 GHz. The transmitter can generate 64-QAM constellations at the input of the radiating elements. The waveforms of the 64-QAM constellations are generated by changing the impedance parameters of the load modulator circuits connected to antennas. At the same time, the output oscillator is kept constant. Thus, a single RF chain can drive the entire transmitter where the power amplifier amplifies a constant signal and does not need to operate in the back-off region. A four-way Wilkinson power divider is used to split the power to the four branches of the transmitter. Microstrip patch antennas have been connected to the load modulators to transmit the desired outputs. RF isolators absorb reflections from each load modulator, allowing branches to generate desired constellations independently and maintaining the system matched at the input all the time. Advanced Design System (ADS) has been used to design, simulate, and fully characterize the transmitter. The proposed transmitter does not require mixers and digital-to-analog converters (DACs). The transmitter has been fabricated, and over-the-air transmission of 64-QAM signals has been tested. The architecture can be scaled to larger array sizes, making it suitable for adoption in 5G massive MIMO systems. High cost, energy, and RF-complexity savings can be achieved if the transmitter is scaled to a larger number of branches.
The design of a 64-QAM I/Q modulator based on load modulation is presented. The modulator is designed to operate at 3 GHz. In any standard M-QAM modulation, the RF circuitry of the voltage source generates currents on the antenna corresponding to the transmitted signals. With load modulation, the waveforms of the M-QAM constellation points are generated by changing the internal parameters of the load modulator connected to the antenna. At the same time, the voltage source is kept constant. Thus, the power amplifier amplifies a constant signal all the time and does not need to operate in the back-off region. An optimization algorithm is developed to find the design parameters of the load modulator circuit. The design parameters obtained from the algorithm have been used in the advanced design system (ADS) software to design, simulate, and fully characterize the RF load modulator circuit. The hardware prototype of the load modulator circuit is realized using microstrip lines and a diode-based switching circuit. The measurements show that the load modulator can generate outputs on the
-parameter complex plane matched to the 64-QAM constellation diagram. A microcontroller is programmed to serve the required bias voltages to the p-i-n diodes in the load modulator based on a predetermined lookup table (LUT). The proposed architecture does not require a digital-to-analog converter (DAC). A credible agreement between the simulation results and measurements is obtained.
A reflection-coefficient (gamma, Γ) generator is a key component in multiport transmitters. The binary-weighted gamma generator consists of power dividers and switchable impedance loads to present the different magnitudes of the reflection coefficients. Among different gamma generators, the binary-weighted configuration has many advantages such as no need for additional digital-to-analog converters and avoiding nonlinearity effects caused by nonlinear devices. However, for broadband operation the correct relative amplitude and phase imbalances in the different branches of the binary-weighting network become critical and must be taken into account. Thus, in this paper the broadband capability is elaborately investigated. Based on this study, a broadband gamma generator which has specially designed curved compensation transmission lines for minimal amplitude and phase imbalances is proposed. This design is implemented and compared against another, first design by experiment to demonstrate the improvement in error-vector-magnitude performance. pHEMT devices are used as switches to present high and low impedance to provide a time-varying Γ. The influence of amplitude and phase imbalances in the binary-weighting network on the error-vector-magnitude is evaluated. The proposed design relieves the imbalances leading to better error-vector-magnitude performance compared to the original one. It achieves a fractional bandwidth of 96 % and 105 % for an error-vector-magnitude below 5 % and 10 %, respectively.
A quadrature up-conversion mixer for low-power wireless communication systems is presented. The circuit is based on a six-port junction with reflective loads to modulate a carrier signal at 190 GHz. While most of the previously published six-port up-conversion mixers were fabricated on ceramic substrates and use discrete III–V semiconductors as reflective loads, this circuit uses common-base stages integrated with the six-port junction on a single chip. The circuit was fabricated in a SiGe BiCMOS process and a conversion gain of –3 dB is measured with –10.3 dBm of power from a local oscillator and 36.5 mW of dc power. The –3 dB bandwidth in the baseband is 17 GHz. To the best knowledge of the authors, this is the first demonstration of
an integrated six-port up-conversion mixer operating at mm-wave frequencies.
In this letter, a six-port transceiver for frequency-division duplex (FDD) systems is proposed and experimentally demonstrated. The proposed transceiver that consists of a single six-port correlator and four Schottky diodes can realize both modulation and demodulation simultaneously at different frequencies. To verify the proposed architecture, the six-port transceiver system prototypes are developed, and modulation and demodulation performances are evaluated by using quadrature amplitude modulation signals at 2.9 and 2.68 GHz, respectively. Moreover, the heterodyne demodulation for a six-port transceiver is proposed to mitigate the interferences from baseband modulation signals. The error vector magnitudes of FDD systems based on the proposed transceiver are found below 2%. IEEE
In this letter, a six-port direct modulator with carrier leakage suppression is proposed and experimentally demonstrated for downlinks in the future high-speed high-carrier-frequency wireless communication systems. To handle high carrier frequencies and provide good performance, GaAs metal-semiconductor field-effect transistor RF switches are used to complete the modulation. Up to 500-MBd quadrature phase shift keying signals at 24 GHz are generated and evaluated in our system. Moreover, the proposed six-port modulator is easy to integrate with the optical link and modulated signals at 24 GHz are evaluated after transmission over up to 20-km standard single mode fiber.
Modern society has shown a large demand for ubiquitous and wireless connectivity, information transmission with high data rates, and precise sensors for any kind of physical dimension. Nevertheless, the frequency spectrum is limited and bandwidth restricted by regulatory issues. Over the last few years, a continuous rise in operating frequency linked to rising bandwidth has been observed. For short-range operation, the license-free industrial, scientific, and medical (ISM) bands beyond 100 GHz are becoming more a focus for practical applications. At the same time, microwave monolithic integrated circuit (MMIC) processes must keep up with this rise in operating frequency, requiring high investment costs in new MMIC technology. Initially, before the cost of this technology becomes reasonable, alternative hybrid circuit concepts are needed as a door opener for mass-market applications. For this purpose, an old frontend concept is getting increased support, leading to a constant growth of an originally small, but worldwide, community: multiport technology. This article provides an overview of the basics, possible applications, and specific calibration procedures for the six-port circuit, which is the most common multiport implementation of this promising architecture.
If present, nonlinear effects in a six-port modulator cause distortion and degradation of the quality of the modulated output waveform. How nonlinear effects occur and their impact on system performance were derived in a mathematical model. The model shows that non-ideal performance of the passive six-port correlator is the main contributor to nonlinear distortion. Simulations and measurements on two manufactured six-port modulators were used to validate the theory and to give deeper insight on system performance. It is shown that by using a differentially signaled six-port modulator instead of a single-ended six-port modulator, better performance is achieved over a wide bandwidth. For an error vector magnitude of less than 10%, the relative bandwidth was measured to 12% for the single-ended but 30% for the differentially signaled modulator.
This paper presents a new low-cost millimeter-wave ultra-wideband (UWB) transceiver architecture operating over V-band from 60 to 64 GHz. Since the local oscillator (LO) power required in the operation of six-port receiver is generally low (compared to conventional one using diode mixers), the carrier recovery or LO synchronization is avoided by using second transmission path and cross-polarized antennas. The six-port model used in system simulation is based on S-parameters measurements of a rectangular waveguide hybrid coupler. The receiver architecture is validated by comparisons between transmitter and receiver bit sequences and bit error rate results of 500 Mb/s pseudorandom QPSK signal.
A new direct conversion wide band (23 GHz-31 GHz) six-port millimeter wave receiver suitable for integrated circuit fabrication is proposed to satisfy mass-market wireless communications. The receiver contains one multi chip module (MCM) consisting of a wide band six-port junction, four RF detectors (Schottky diodes), video amplifiers and I&Q decoder. The prototype circuits are fabricated in hybrid integrated circuits, and the receiver topology is suitable for fabrication in microwave monolithic integrated circuits (MMICs). This new hardware receiver is proposed as a robust, rugged, low cost receiver for use in wide band wireless mass market QPSK communications. Hand held and laptop terminals for future e-mail/multimedia services are a prime example of communication equipment needing such receivers. BER measurements and simulation results are presented in the presence of noise, adjacent signal interference, local oscillator (LO) phase shift and LO phase noise
A compact six-port transceiver for time-division duplex systems is proposed. The proposed transceiver only uses a single six-port junction for the Tx and Rx mode. Also, we propose the new radio frequency (RF) and baseband interface component, which consists of switch, reflection coefficient generator, and the power detector. The prototype circuits are fabricated to validate the new transceiver with 15-Mbps quadrature phase shift keying (QPSK) digital modulator and 10-Mbps QPSK demodulator at the carrier frequency of 2.4GHz. The proposed six-port transceiver can provide a simple, low-cost, low-power, and reconfigurable RF design platform
A direct quadrature phase shift keying modulator based on six-port technology is presented. The modulator comprises a six-port circuit, a switch matrix and open and short terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technology has the advantage of signal integrity, low power consumption and physical scalability to attain different frequencies of operation and extendibility to M-ary phase shift keying. Experiment results demonstrate performance with an output phase difference from 0.8 to 4.5° and an amplitude difference from 0.5 to 2.7 dB. A data throughput of 200 Mbits was attained.
Configurable radio terminals require receivers with wide-band capabilities in order to support as many services as possible at most different carrier frequencies. Conventional well-known receiver architectures employing active circuitry are limited in this respect. Therefore, alternative architectures are investigated, such as the six-port, which has been introduced as a very flexible and elegant means for microwave measurements in the 1960s and 1970s. Later on, it has been used in radar applications. It was not until recently that communications receivers have been built upon the six-port principle. However, in all publications, there is always a certain mystic about the six-port. It has even been described as a "black box". In order to help paving the way for a wider application of the six-port technology, this paper describes the basic six-port theory and sets it into relation with the conventional receiver architectures such as the homodyne and heterodyne receiver. Finally, the advantages and possible applications of receivers based on the six-port technology are discussed.
A new direct-conversion wide-band (23-31 GHz) six-port receiver is
proposed suitable for millimeter-wave integrated system design. This new
hardware receiver is found to be robust, rugged, low cost, and suitable
for use in broad-band wireless mass-market QPSK communications. The
prototype circuits are fabricated to validate this new concept with our
miniaturized hybrid microwave integrated-circuit technology and the
proposed receiver topology is also suitable for monolithic-microwave
integrated-circuit fabrication. This application-specific integrated
receiver is designed on the basis of a wide-band six-port junction and
other analogical circuits in the form of a simple multichip module.
Bit-error-rate measurements and simulation results are shown and
discussed in the presence of noise, adjacent signal interference,
local-oscillator (LO) phase shift, and LO phase noise. The maximum bit
rate is fundamentally limited by the speed of the video and decoder
circuits. Nevertheless, several hundred megabits per second can be
achieved at low cost
Direct-carrier modulation is an attractive technique for low-cost
high-performance radar transceivers. In this paper, it is shown that,
when the technique is applied to a generic homodyne radar architecture,
the signaling waveform can be software adapted without requiring any
hardware modifications. The key circuit in this novel software radar is
a W-band monolithic I-Q vector modulator employing two push-pull
(bi-phase) amplitude modulators. To fully exploit this circuit's
capacity to generate accurate constellations at millimeter-wave
frequencies, a generalized theoretical analysis of the I-Q (push-pull)
vector modulator is presented. This is a comprehensive analysis of the
topology and does not assume ideal components. As a demonstration of the
vector modulator's flexibility, a 76.5-GHz MMIC version has been
fabricated and characterized by means of static S-parameter measurements
and by several modulation spectra. Based on the theoretical model and
the measured results, the I-Q (push-pull) vector modulator promises to
be a vital component for the realization of future software radar
RF System Design of Transceivers for Wireless Communications is for RF Engineers and, in particular, those engineers focusing mostly on RF systems and RFIC design. The author develops systematic methods for RF systems design, complete with a comprehensive set of design formulas. Its focus on mobile station transmitter and receiver system design also applies to transceiver design of other wireless systems such as WLAN. The book is filled with detailed wireless systems design information, and addresses specifications that are critical for the design process. Additional highlights include: • Fundamental information on communications, signal and system theories • Coverage of superheterodyne, direct-conversion, low-IF, and band-pass sampling radio architectures • Frequency planning, system link budgeting, and performance evaluation of transmitters and receivers • Nonlinearity effect analyses involving intermodulation, interferer blocking, spectrum regrowth and modulation • Approaches for specifying RF ASICs on which mobile systems are built • AGC systems, ADC dynamic range consideration and power management are addressed • In-depth treatment of both theoretical and practical aspects of mobile station RF system design This comprehensive reference work covers a wide range of topics from general principles of communication theory, as it applies to digital radio designs to specific examples on implementing multimode mobile systems. Wireless engineering professionals will definitely find this an invaluable reference book. © 2005 Springer Science+Business Media, Inc., All rights reserved.
In six-port modulators a phase shifting network on specific ports can be used to suppress the carrier leakage that may be present if this network is not present. A model is derived to predict the carrier leakage suppression and error vector magnitude (EVM) as a function of the phase shifting network S-parameters. Both carrier leakage suppression and EVM can be expressed by the same error function. The error function can be used to find the allowed amplitude and phase mismatch in the phase shifting network, or to optimize the performance of a phase shifting network over a given frequency range. A broadband phase shifting network, based on a loaded transmission line, is designed and optimized to operate at a relative bandwidth of 60% for an EVM <; 10%. This should be compared to a phase shifting network based on a single transmission line with a corresponding bandwidth of only 12%. The broadband phase shifting network is useful for six-port modulators with carrier leakage suppression, targeting UWB applications.
The use of Schottky diodes as high-speed variable impedance loads in six-port modulators are proposed and analyzed in this paper. The impedance dependency of diode parameters and local oscillator power are investigated by theoretical analysis and simulations. A prototype for a direct carrier six-port modulator using Schottky diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 300 Msymbol/s is generated, i.e., at a data rate of 1.2 Gbit/s, validating the use of Schottky diodes as high-speed variable impedance loads in six-port modulators.
An ultrawideband 6–9 GHz six-port correlator is designed and manufactured.Based on this six-port correlator, behavioral models, and true component circuit designs of a transceiver are developed to study the performance of the proposed direct conversion ultrawideband transceiver topology. A new six-port modulator with controllable impedance terminations implemented with a field effect transistor in the linear operation region is presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 740–746, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25021
In this study, a new vector modulator topology is presented. The modulator is composed by two “balanced-load” biphase modulators. The balanced load is a novel principle allowing a topological simplification of commonly adopted vector modulator schemes: seven couplers are used instead of the 9 ones in traditional reflection-type modulators, with comparable performance. The measured results of monolithic 45–65 GHz test vehicles of the methodology for both biphase and vector modulators, are presented. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.
Using our own-developed frequency multiplexing network, a radio architecture for parallel radio signal processing has been proposed for achieving extremely high data rate above 10 Gbit/s. To meet the high requirement on phase linearity, amplitude balance and low noise figure in a very large bandwidth, our own-developed ultra-wideband six-port correlator has been utilized for the modulator and demodulator in the radio architecture.
This paper presents a direct carrier six-port modulator. To allow arbitrary load impedances to be used and for suppression of carrier leakage, a new circuit architecture with a technique to suppress carrier leakage is proposed and implemented. A theoretical model of the proposed modulator is derived. A prototype modulator utilizing diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz for verification of the proposed technique. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 100 Msymbol/s is generated, as well as good carrier leakage suppression.
This paper presents measurement results for a six-port-based demodulator designed for a center frequency of 7.5 GHz and with a bandwidth of 1 GHz for operation in the ultra-wideband band. The demodulator includes the six-port correlator, diodes, and amplifiers needed to recover the baseband data. Measurement results show that the prototype supports data rates at 1.7 Gbit/s with bit-error rate if a two-tap linear equalizer is used and bit-error rate if only threshold detection is used. The measured performance of the used six-port correlator including the amplifiers is presented and their influence on the overall system performance is discussed. Limitations in the present system and possible improvements are also considered.
This paper presents two new diode configurations for use with six-port based demodulators. The first proposed diode configuration allows a simplified diode to filter/amplifier interface. The second configuration allows for full-wave rectification and suppression of odd-order harmonics. A demodulator prototype utilizing the new diode concept is designed for a center frequency of 7.5 GHz and with a bandwidth of 1 GHz for verification. The demodulator includes the six-port correlator, diodes and amplifiers needed to recover the baseband data.
This paper proposes how antenna polarization can be utilized to increase the maximum data rate in a multiple six-port receiver system. By utilizing data and carrier interleaving, the total information bandwidth increases and therefore the maximum data rate. Prototype antennas were manufactured and the measured results were later used in a simulation model with three channels for verification of the concept.
Modern wireless sensing and communication systems are often based on high bandwidth and high carrier frequencies. In the range beyond 100 GHz, common receiver architectures, like active homodyne or heterodyne receivers, have an issue with the amplification needed for mixing. Also, high bandwidth is a problem for these systems. In this context, the six-port receiver is a good alternative, just as well as for lowvolume markets. The six-port concept is based on the additive superposition of the two RF input signals using four different relative phases leading to constructive or destructive interaction. The resulting signals are directly downconverted to baseband by diode circuits operated in detector or mixing mode. The complexvalued information can be easily reconstructed from the four baseband voltages. Historic evolution leads from the reflectometer approach for an alternative vector network analyzer to receivers for sensing and communications. A recent topic is the technology gap in automotive workshops for adjusting the long-range radar sensor of a car. Here, the six-port concept as alignment tool is a good choice, because of its excellent phase resolution. Currently, the integration of the six-port receiver on a MMIC for frequencies beyond 100 GHz is the focus of current work and will be intensified in the future. Will the six-port concept replace common active homodyne and heterodyne receivers? No, but it is a serious alternative for millimeter-wave frequencies and ultrahigh-bandwidth applications in wireless sensing and communication systems. This modern concept can tap new markets for both wireless sensors and sensor networks.
General design equation for an N-way power divider with arbitrary power split ratio is suggested. It consists of N transmission lines and N resistors and may be terminated in arbitrary impedances. Since a transmission line with too high characteristic impedance is difficult to realize in microstrip technology, arbitrary design impedance A is introduced to control it. The A is arbitrary and positive value, and as many sets of design equations as possible may be produced depending on design situation. Therefore, the design formulas containing A may be called "general design equations". To verify them, a 3-way power divider with a power split ratio of 1:2:4 has been fabricated in microstrip technology, and measured results are in good agreements with the predicted ones.
A novel approach is proposed for direct demodulation of various
digitally modulated signals at microwave/millimeter wave frequencies
using a six-port phase/frequency discriminator (SPFD). The proposed
six-port direct digital receiver is capable of handling PSK and QAM as
well as their varieties. Preliminary measurements on demodulation of
DBPSK signals at 26.5 GHz, 33 GHz and 40 GHz have revealed great
potential of this new receiver
A direct 16 quadrature amplitude modulation (QAM) modulator based on the six-port technique is proposed. It uses a six-port passive microwave network to implement the modulation scheme with suitable terminations. A microwave prototype was built to validate the 16 QAM modulation up to 200 Mbit/s data rate at 4.2 GHz carrier frequency. The error vector magnitude and local oscillator (LO) power testing show that this six-port 16 QAM modulator has wide dynamic range capability to overcome the LO power variation. It has potentially low cost and low power consumption for RF communications applications.
The author focuses on light detectors and their properties. A classification of detectors is given, and phototubes and photomultiplier-tubes are described. Just as the tubes were classified, so again a distinction can made between solid-state detectors that have an internal gain and detectors that have no internal gain. Detectors with internal gain are the photoconductive detectors, the avalanche photodiode, and the phototransistor; detectors without internal gain include the p-i-n and Schottky barrier photodiodes. A discussion on how to choose photodetectors for a given application is given. Applications of different photodetectors and future research are discussed.< >
We have derived the transfer functions for two types of six-port quadrature phase-shift keying (QPSK) modulators and investigated their performances in terms of carrier leakage, Gray mapping, and conversion efficiencies. Our result shows that the carrier leakage is minimized when GammaON = -GammaOFF. In addition, our analysis reveals here that only the parallel six-port QPSK modulator demonstrates a Gray mapping feature. Our analysis further proves that the serial and parallel modulator give a maximum conversion efficiency of 100% and 50%, respectively, but the efficiency of the serial modulator deteriorates faster than the parallel modulator when the terminations are not ideal. We have also shown that the serial modulator requires tighter design tolerances due to its cascaded topology. Our theoretical and measured results show good agreements with the six-port modulators developed for 4.2 GHz.
A circularly symmetric power divider is described which splits a signal into n equiphase equiamplitude parts where n can be odd or even. The power divider provides isolation between output terminals and approximately matched terminal impedances over about a 20 per cent band. A theory of operation is given which yields the necessary design parameters, and an experimental model is described which has a minimum isolation of -27 db between output terminals, an output VSWR of 1.6, and an input VSWR of 1.2.
In this paper, we present an integrated circuit technology
suitable for low-power bias-free optical control of microwave circuits
and antennas. We have integrated miniature photovoltaic arrays with
varactor diodes and thin-film resistors to form monolithic optically
variable capacitors (OVCs). For the monolithic OVC described here, only
1.5 mW of optical power was required for more than 2:1 change in
capacitance (0.9-0.4 pF). Optically controlled microwave circuits such
as X-band analog phase shifters and tunable notch filters, which
incorporated the monolithic OVC as the control element, were fabricated
to demonstrate the potential of this technology
A photovoltaic-FET (PV-FET) is demonstrated for RF/μwave
switching with performance improved over other optoelectronic switches
reported while operating with 10-100 times less optical power. The
PV-FET characteristics were 3 Ω on-resistance, >30 MΩ
off-resistance under <1 mW optical power, and 300 fF switch
capacitance. This PV-FET was inductor tuned at 790 MHz and 7.4 GHz to
enhance isolation, intended for reconfigurable antenna applications. The
measured insertion loss and isolation agree well with those from
theoretical calculation and numerical circuit simulation based on the
switch parameters. The measured switch rise and fall times were 20 μs
and 2 μs, respectively. Controlled by light via optical fiber, the
PV-FET can be used for remote RF/μwave switching control with no
electrical bias, complete electromagnetic, and good thermal isolation
Vector modulator for
- D S Mcpherson
- S Lucyszyn