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ABSTRACT: Microelectromechanical systems (MEMS) technology has the potential of replacing many of the radio frequency (RF) components used in to day's satellite communication systems. In many cases, such RF MEMS components would not only substantially reduce size, weight, and power consumption, but also promise superior performance when compared to that of current technologies. The benefits of MEMS technology be come more pronounced for switch matrices because there is a large number of switching elements and, therefore, any size and mass reduction would have large overall impact. Though there has been some controversy on the reliability and lifetime of RF MEMS switches, significant improvements have been made and RF switches with billions of switching cycles have been demonstrated. This article describes the potential applications of RF MEMS switch matrices in the satellite industry, where mass reduction and performance improvement is crucial.
IEEE Microwave Magazine 09/2011; · 2.11 Impact Factor
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ABSTRACT: A waveguide circular polarizer with reconfigurable polarization sense is proposed in this paper. The polarizer can be switched between right and left hand circular polarization. The polarization sense is controlled by RF MEMS switches, which commute between two states for allowing or blocking adequately two different signal paths inside the waveguide structure. The polarizer is made up of three building blocks, involving E-plane waveguide MEMS SP2T switch, ridge to waveguide transitions and a septum-orthomode transducer. A switchable Ku-band polarizer prototype is designed and tested as a proof of concept. The experimental performance shows acceptable return losses and axial ratio levels in the 12.7 to 14.8 GHz band (15.3% fractional bandwidth). The proposed structure is compact and is useful for applications that require fast polarization switching.
Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International; 07/2011
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ABSTRACT: Low-pass filters are implemented as impedance inverters for a bandstop filter design. The choice of the order of the low-pass filter impacts the usable passband bandwidth of the bandstop filter. A great savings in size occurs when implemented with highly miniaturized low temperature superconducting lumped elements. A standard multilayer niobium based fabrication process is used to fabricate the lumped element bandstop filter. The filter is tested and suggestions are made to further improve the return loss outside of the rejection band.
IEEE Transactions on Appiled Superconductivity 07/2011; · 1.04 Impact Factor
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ABSTRACT: A system and method for the automated tuning of coupled resonator tunable filters is presented. The system and method are amenable to integration and are developed for on-board and on-chip automatic tuning of tunable filters without the use of a vector network analyzer and with minimal additional hardware. An analytical coupling matrix-based model of the tuning algorithm is developed to analyze and predict the performance of the tuning algorithm. The tuning model is verified with the automated tuning algorithm operating on a realized tunable filter. Finally, a low-cost hardware prototype for scalar transmission measurement for standalone implementation of the algorithm is also presented.
IEEE Transactions on Microwave Theory and Techniques 01/2011; · 1.85 Impact Factor
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ABSTRACT: μA position sensing scheme for the detection of hysteresis and dielectric charging is presented. The sensing mechanism is based upon piezoresistance and is applied to an RF MEMS variable capacitor fabricated using a standard 0.35 μm CMOS process with MEMS postprocessing. The position sensor, based upon the piezoresistive property of the CMOS polysilicon layer, proves capable of detecting the effects of hysteresis and dielectric charging in the fabricated device. Potential applications of the sensing scheme include the mitigation of the effects of hysteresis and dielectric charging on MEMS variable capacitors through closed-loop control.
IEEE Transactions on Microwave Theory and Techniques 01/2011; · 1.85 Impact Factor
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ABSTRACT: The reflected group delay method can be used to design higher-order superconducting filters. A correction factor is introduced to ensure that the reflected group delay response is symmetric about the center frequency. The method is demonstrated through the design of an eight-pole lumped-element filter using a circuit simulator. A miniaturized high-temperature superconducting eight-pole filter and a highly miniaturized lumped-element low-temperature superconducting eight-pole filter are designed using this method, and their measured results are reported.
IEEE Transactions on Appiled Superconductivity 09/2010; · 1.04 Impact Factor
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ABSTRACT: Fully integrated novel magnetically-actuated dielectric cantilever MEMS switches suitable for high frequency RF applications are reported. A four-mask fabrication process has been developed to produce the MEMS switches with integrated current coils on both the substrate and the dielectric cantilever. The switches are actuated using an electromagnetic force and held in the DOWN state using an electrostatic force. DC actuation currents around 110 mA have been measured to be sufficient for operating the switch. The beam is maintained at DOWN state with the application of a potential difference as low as 24 V between the coils. In terms of the RF performance, the insertion and return losses are lower than -0.3 dB and -24 dB, respectively; and isolation is higher than 34 dB up to 10 GHz. To enhance the switch reliability, it is feasible to force the device into the UP state using a repulsive electromagnetic force in the case of release failure or stiction.
Microwave Symposium Digest (MTT), 2010 IEEE MTT-S International; 06/2010
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ABSTRACT: A variable MEMS capacitor with piezoresistive feedback is presented. The capacitor is fabricated in a commercial 0.35 μm CMOS process with MEMS post-processing. The work presented demonstrates a piezoresistive sensing scheme capable of controlling hysteresis effects in a CMOS-MEMS variable capacitor. Potential applications of the sensing scheme include closed-loop control of variable capacitors and detection of dielectic charging.
Microwave Symposium Digest (MTT), 2010 IEEE MTT-S International; 06/2010
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ABSTRACT: A reconfigurable impedance matching network has been developed for a wideband operating frequency. The network is based on a slow-wave distributed MEMS transmission line (DMTL) coupled with a tri-state MEMS capacitive switch to improve the operating frequency range. The proposed design consists of 8 tri-state RF-MEMS switches producing 6561 (3<sup>8</sup>) impedance states. The size of the tunable matching network fabricated on an alumina substrate is very compact (4.4 × 1.9 mm). The measured results demonstrate wide coverage of the Smith chart between 5 GHz to 20 GHz. The transducer gain of the network is better then 1 dB for a wide range of input impedances. The measured results validate the potential of the proposed structure to realize a miniature reconfigurable matching network with a wide impedance coverage over an extended operating frequency range.
Microwave Symposium Digest (MTT), 2010 IEEE MTT-S International; 06/2010
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ABSTRACT: A tunable RF microelectromechanical system (MEMS) impedance-matching network operating at a frequency band from 13 to 24 GHz based on the distributed microelectromechanical transmission line (DMTL) concept is presented in this paper. The network is implemented using a standard 0.35- ??m CMOS technology and employs a novel suspended slow-wave (SSW) structure on a silicon substrate. The SSW structure results in a reduced total footprint and enhanced impedance coverage. The 8-bit DMTL matching network, fabricated using switched MEMS capacitors and SSW coplanar waveguide on a silicon substrate, results in a wide coverage of the Smith chart up to a maximum voltage standing-wave ratio of 11.5:1 with an impedance matching better than 10 dB and a power transfer ratio of better than -2.84 dB at 24 GHz. To our knowledge, this is the first implementation of a DMTL tunable MEMS impedance-matching network using a standard CMOS technology.
IEEE Transactions on Microwave Theory and Techniques 05/2010; · 1.85 Impact Factor
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ABSTRACT: The objective of this paper is to investigate the integration of capacitive type RF microelectromechanical systems (MEMS) switches in a standard CMOS technology. A maskless monolithic integration process dedicated to electrostatically actuated capacitive type RF MEMS switches is developed and optimized. The fabricated switches consist of composite metal-dielectric warped membranes. The warped-plate structure is used to increase the capacitance ratio of the switch. The switches are fabricated using the interconnect metal and dielectric layers available in a standard 0.35-μm CMOS process. Measurement results for the first switch show an insertion loss less than 0.98 dB, a return loss below 13 dB up to 20 GHz in the up-state, and a down-state isolation of 12.4-17.9 dB from 10 to 20 GHz. The capacitance ratio is enhanced up to 91:1 using the warped-plate structure. A second cascaded switch consisting of two shunt capacitive switches and a slow-wave high-impedance transmission line section is designed and fabricated for high-isolation applications. The measured insertion loss for this switch is less than 1.41 dB up to 20 GHz, the return loss is below 19 dB, and the isolation is 19-40 dB across the frequency band from 10 to 20 GHz. The proposed RF MEMS switches can be used in millimeter-wave CMOS RF front-ends where multiband functionality and reconfigurability is required.
IEEE Transactions on Microwave Theory and Techniques 03/2010; · 1.85 Impact Factor
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ABSTRACT: Electrostatic micro-power generators (MPGs) are modeled and analyzed with particular emphasis on electromechanical coupling and its impact on the system dynamics. We identify two qualitatively different regimes in the MPG response, dubbed slow and fast. A linearized electromechanically coupled model of an electrostatic MPG and two simplified linear models are used to study the response of the MPG. Linear models are found adequate to represent the dynamic response of fast MPGs but inadequate to represent the response of slow and mixed domain MPGs. A nonlinear model is developed and validated to describe the response of those MPGs under moderately large excitations. On the basis of this analysis, we describe a method and provide design rules for realizing wideband electrostatic MPGs, and develop closed-form formulae for the extracted power for MPGs under moderately large excitations.
Smart Materials and Structures 01/2010; 19(2):025007. · 2.09 Impact Factor
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ABSTRACT: We developed a design procedure for wideband electromagnetic micropower generators (WMPGs) based on piecewise-linear oscillators. We find that the dominant factors in the performance of this class of WMPGs are the stiffness ratio of the oscillator and the velocity of the moving structure at the point of impact with the stopper. We also find that designing these WMPGs requires additional steps beyond those required in the design of regular MPGs. The additional steps match the output power and bandwidth of the WMPG to the probability density function of environmental vibrations. While these steps add complexity to the design of WMPGs, they are shown to significantly increase harvested energy.
Journal of Microelectromechanical Systems 01/2010; · 2.10 Impact Factor
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ABSTRACT: Here, a new thermally actuated latching wideband RF microelectromechanical systems (MEMS) switch is presented. The switch employs two thermal actuators connected to two thin metal arms which serve as signal lines of coplanar waveguide switch. The actuators pull the thin arms sequentially, and latch the switch. The switch can be actuated on and off by using either short voltage or current pulses. Using a dielectric bridge (nitride) as an interface between the actuators and the thin arms, the RF circuitry is separated from DC actuators, allowing wide-band operation. The switch demonstrates an excellent wideband RF performance with an insertion loss of better than 0.3 dB up to 20 GHz and better than 0.8 dB up to 40 GHz. The return loss and isolation of the switch is better than 20 dB for the entire frequency band. The switch also has a very satisfactory repeatability with better than 0.1-dB variation in insertion loss and less than 1-dB variation in return loss and isolation at 30-dB level up to 6000 times switching cycles. The switch has been also successfully tested for RF power handling capability up to 40 dBm. The proposed switch has very simple RF structure which makes it an ideal candidate to be integrated in the form of more complex circuitry. An application of the proposed switch for a band selection network which is used in multiband transceivers has been presented here.
IEEE Transactions on Microwave Theory and Techniques 01/2010; · 1.85 Impact Factor
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ABSTRACT: A design methodology for the distributed microelectromechanical system (MEMS) impedance matching networks based on the optimization of the uniformity of the Smith chart coverage has been developed. The proposed approach was validated through a comparison between a traditional coplanar waveguide (CPW) design and an improved design based on a slow-wave (SW) structure. The enhanced reconfigurable impedance matching network has been developed for low-frequency applications. The network is based on a distributed MEMS transmission line (DMTL) coupled with the SW structure to reduce the total physical length of the network by 25% in comparison with a traditional DMTL. An extensive analysis was performed to identify the impact of each design parameter in order to optimize the structure and reduce the required size for relatively low-frequency applications. Several parameters are extracted from the electromagnetic simulation results and are used to design the proposed impedance matching network. Measurement results confirm the efficiency of the proposed design methodology in improving the impedance coverage and also miniaturization of the DMTL impedance matching networks.
IEEE Transactions on Microwave Theory and Techniques 01/2010; · 1.85 Impact Factor
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ABSTRACT: A tunable RF MEMS varactor with three-step behavior is presented. The device has a low actuation voltage of less than 12 V for the final step and a high quality factor of greater than 100 over the entire tuning range up to 10 GHz with a self resonance frequency above 24 GHz. The device shows a capacitance ratio of better than 3:1 with no de-embedding in a CPW shunt configuration.
Microwave Conference, 2009. EuMC 2009. European; 11/2009
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ABSTRACT: This paper demonstrates the electromagnetic modeling and simulation of an implanted Medtronic deep brain stimulation (DBS) electrode using finite difference time domain (FDTD). The model is developed using Empire XCcel and represents the electrode surrounded with brain tissue assuming homogenous and isotropic medium. The model is created to study the parameters influencing the electric field distribution within the tissue in order to provide reference and benchmarking data for DBS and intra-cortical electrode development.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: A novel dual-band dielectric resonator constructed from a single piece of high- K ceramic substrate is presented in this paper. The proposed dual-band dielectric resonator is employed to implement dual-band filters whose center frequencies and bandwidths of the first and second passbands can be controlled independently. To illustrate the concept, two dual-band filters of this type with different bandwidth and separation of two passbands are designed, fabricated, and measured. The filters are both compact in size with a great simplicity in assembly and integration. The developed dual-band dielectric-resonator filters are potentially applicable for multiband applications in future wireless communication systems.
IEEE Transactions on Microwave Theory and Techniques 08/2009; · 1.85 Impact Factor
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ABSTRACT: Here, a new thermally-actuated latching RF MEMS switch is presented. The switch uses two thermal actuators connected to two thin arms which serve as the signal lines of coplanar waveguide switch. The actuators pull the thin arms sequentially, and latch the switch. The switch can be actuated ON and OFF by using voltage or current pulse. Using a dielectric (nitride) as an interface between the actuators and the thin arms, the RF circuitry is separated from DC actuators, allowing wide band operation. The proposed switch has a simple RF circuitry that makes it suitable for integration in more complex configurations. The switch demonstrates excellent RF performance of better than 0.3 dB insertion loss and a return loss of better than 20 dB for the entire frequency band up to 20 GHz.
Microwave Symposium Digest, 2009. MTT '09. IEEE MTT-S International; 07/2009
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ABSTRACT: This paper proposes new solutions for implementing wideband large switch matrices. These solutions are based on crossbar and L-shaped topologies. This paper introduces a high-performance wideband switch cell to build up scalable NtimesN switch matrices and gives an account of the design, fabrication, and characteristics of the switch cell and a 3times3 crossbar switch matrix. The chosen design procedure is seen to be appropriate since it produces valid measured results. In addition, this paper presents an RF microelectromechanical systems L-shaped switch matrix, which indicates less variation of characteristics for certain types of connectivity. It also demonstrates that for a 4times4 switch matrix, there is a 50% improvement in insertion loss and phase-shift variation.
IEEE Transactions on Microwave Theory and Techniques 07/2009; · 1.85 Impact Factor
