R.R. Mansour

University of Waterloo, Ватерлоо, Ontario, Canada

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Publications (197)154.06 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a novel RF-MEMS dielectric-less switched capacitor that exhibits a high capacitance ratio. The proposed design is based on a floating contact element concept that results in a reduced up state capacitance. The switched capacitor was fabricated on 200 mm silicon wafer with an industrial process developed for manufacturing robust and reliable packaged RF MEMS devices. RF Measurements up to 20 GHz were performed on the fabricated device, showing a capacitance ratio higher than 30:1 with a good quality factor over the operating frequency range. This RF MEMS switched capacitor is suitable for adaptive and reconfigurable RF circuits.
    Microwave Integrated Circuits Conference (EuMIC), 2013 European; 01/2013
  • Source
    M. Bakri-Kassem, R.R. Mansour
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    ABSTRACT: A novel CPW based phase shifter that relies on automatic collapse of capacitive switches is designed, fabricated and tested. The novel design of the phase shifter is due to a novel CPW topology and automatic collapse mechanical design that is designed to operate at several and gradual collapse voltages. The novelty of the CPW has been achieved through the corrugated grounds to create a slow wave transmission line. The resulted compact CPW will have an effective electrical length that is physically equivalent to a relatively longer conventional CPW. The automatic collapse of the designed capacitive switches comes through deferent lengths of the beams that are carrying those capacitive switches. The worst measured insertion loss and return loss are 1.7 dB and 13 dB, respectively, at 30 GHz with a phase shift of almost 106 degrees. The phase shifter is built on alumina substrate of gold material using UWMEMS process.
    Microwave Integrated Circuits Conference (EuMIC), 2013 European; 01/2013
  • S.N. Nejad, A.A. Fomani, R.R. Mansour
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    ABSTRACT: In this paper, several Giant Magneto Impedance (GMI) magnetic sensors have been designed, fabricated, post processed and tested to work in low field intensities (miliTesla range). The sensors are multilayer GMI sensors having CoSiB as GMI material surrounded with two thinner gold layers. The conventional thin film microfabrication process is employed to fabricate the sensors on a glass wafer. A post-processing thermal and magnetic treatment is suggested to magnetize GMI material and enhance performance of the sensors. The suggested post-processing step will decrease fabrication cost of GMI sensors and improve their performance effectively.
    Sensors, 2013 IEEE; 01/2013
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    ABSTRACT: We present a compact wireless headset system for simultaneous multi-site neural recording and neurostimulation in the rodent brain. The system comprises flexible-shaft microelec-trodes, neural amplifiers, neurostimulators, a digital time-division multiplexer (TDM), a micro-controller and a ZigBee wireless transceiver. The system is built by parallelizing up to four 0.35µm CMOS integrated circuits (each having 256 neural amplifiers and 64 neurostimulators) to provide a total maximum of 1024 neural amplifiers and 256 neurostimulators. Each bipolar neural ampli-fier features 54dB-72dB adjustable gain, 1Hz-5KHz adjustable bandwidth with an input-referred RMS noise of 7.99µV and dissipates 12.9µW. Each current-mode bipolar neurostimulator generates arbitrary waveform programmable biphasic currents in the range of 20-250µA and dissipates 2.6µW in the stand-by mode. Reconfigurability is enabled by stacking a set of dedicated mini-PCBs that share a common signaling bus within as small as 22×30×15mm 3 volume. The system features flexible polyimide-based microelectrode array design that maximizes pad packing density. Electrodeposition pad nanotexturing reduces the electrode-tissue interface impedance from an average of 2MΩ to 30KΩ at 100Hz. The system has been validated in vivo in Sprague-Dawley rats.
  • S.R.I. Gabran, R. R. Mansour, M.M.A. Salama
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    ABSTRACT: Low power near-ultraviolet laser can be employed in various pattern transfer techniques such as maskless lithography and organic film ablation. Laser maskless lithography allows rapid prototyping using thin as well as thick photoresist films. Non-photosensitive organic films can be patterned by laser ablation, and this technique is applied in creating micro-molds for metal deposition using electroplating and electroless deposition. This paper presents experimental results, a quantitative study and modeling of laser maskless processing using desktop Nd:YAG laser system using four different photoresists. Process variables were experimentally optimized to identify the appropriate laser parameters that would yield reliable and reproducible patterns. A finite element thermal model of the ablation process was created to investigate the effects of different substrate materials on the process quality.
    Optics and Lasers in Engineering 05/2012; 50(5):710–716. DOI:10.1016/j.optlaseng.2011.11.020 · 1.70 Impact Factor
  • S.S. Attar, S. Setoodeh, R.R. Mansour, D. Gupta
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    ABSTRACT: A novel niobium-based superconducting DC-contact RF MEMS switch is presented for the first time. The switch is amenable to integration with the superconducting micro-electronics (SME) technology. A comparison of the switch RF performance at room and cryogenic temperatures indicates a great improvement in the insertion loss of the switch when niobium is superconducting. The mechanical characteristic of the switch at extremely low temperature (4K) is investigated. The switch exhibits only 18% increase in the actuation voltage as temperature changes from room temperature (300K) to 4K. A niobium superconducting tunable resonator is designed and fabricated employing the proposed switch as the tuning element. The concept can be extended to realize a high-Q switched capacitor bank for reconfigurable RF front-end components in SME receivers.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
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    ABSTRACT: We present the design and experimental results of a scanning microwave microscopy (SMM) system that does not require the use of a conventional atomic force microscope (AFM). Microfabricated SMM probes are actuated by integrated MEMS scanners in a commercially available multi-user process. This design is unique in the sense that the tip can be scanned over the sample both laterally and vertically, over a 10µm × 10µm scan range. We first validate our approach with a test-bench consisting of a fixed probe and an integrated sample-scanning stage. This device is used to obtain characteristic approach curves of S11 as a function of tip-sample separation. We then investigate the effect of tip-sample separation on the resolution of the instrument. CPW probes with integrated 1-D and 2-D actuation are then presented. These devices can be used to modulate the tip-sample separation to off-chip samples with a periodic (200Hz) signal, improving immunity to long-term system drifts. To increase measurement sensitivity, a single-stub matching network has been used to match high tip to sample impedance to the 50 ohm of a performance network analyzer. Measurement results agree very well with reported SMM measurements in the literature
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
  • Source
    M. Bakri-Kassem, R.R. Mansour
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    ABSTRACT: A novel latching RF MEMS Switch is proposed. The single pole single throw (SPST) switch is built on a 20 μm thick nickel layer eliminating any potential warping due to thermal mismatch. The switch exhibits a 40 μm displacement with a power consumption of 175 mW at 80K under vacuum. The measurement was done over ambient and vacuum and over wide range of temperatures from 300 K to 80 K. The switch demonstrates an excellent RF performance up to 26 GHz.
    Microwave Integrated Circuits Conference (EuMIC), 2012 7th European; 01/2012
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    ABSTRACT: Mass and volume of the payload electronics are significant contributors to the overall cost of space systems. Satellite systems rely on switch matrices to provide system redundancy and to enhance capacity by providing flexible interconnectivity. The RF-MEMS technology offers the potential of large reductions in the mass and volume of satellite switch matrices leading to a significant cost reduction of satellite systems. The technology has also the potential of accelerating the development and implementation of new advanced satellite systems. This paper presents various configurations for highly miniature RF MEMS switch matrices. It also presents novel configurations for high power multiport waveguide switches that eliminate the need to use bulky motors.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
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    ABSTRACT: Out-of-plane Micro-Power Generators (MPG) are investigated to identify their optimal design and operating conditions. Those MPGs employ a variable capacitor, an electret layer embedded between its electrodes, and an inertial mass carried by a movable electrode. Using a linear model, we study the impact of varying the capacitor gap, load resistance, and electret voltage on the output power. In addition, we analyze the effect of squeeze-film damping on the MPG performance. We find that the linear model breaks down as the excitation level increases. A nonlinear model is developed to capture the MPG response and estimate its output power in closed-form.
    IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society; 01/2012
  • J.A. Ruiz-Cruz, M.M. Fahmi, R.R. Mansour
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    ABSTRACT: A novel combline resonator is introduced in this paper for realizing compact microwave dual-band filters. The basic resonator is based on the well-known combline topology, where an additional metallic conductor is introduced for having two TEM modes. The resonant frequencies of the two asynchronous TEM resonant modes are controlled by the length of the two concentric conductors and their spacing. The proposed structure is employed to realize a dual-band filter, where each combline resonator provides one resonant mode per pass-band. The control of the filter parameters, such as pass-band bandwidths and band separation, is addressed. These filters harness the advantages of combline technology for dual-band filters, using the compactness provided by the proposed resonator. A complete design is introduced. Simulations as well as experimental results are presented showing excellent agreement, thus validating the proposed concept.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
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    ABSTRACT: This paper presents an overview of recent advances in radio frequency and microwave filter topologies for satellite communication systems. Many types of filters have been developed during the last years in order to satisfy the demands of modern applications in both terrestrial systems and onboard spacecrafts, leading to a great variety of aspects such as transfer functions, resonator implementations or coupling structures. This paper revisits some of the last advances in this area, including the modeling and full-wave simulation. Some recent designs using dual-mode cavities along with other novel implementations in ridge waveguide will be shown.
    Journal of Communications and Networks 12/2011; 13(6):625-632. DOI:10.1109/JCN.2011.6157479 · 0.75 Impact Factor
  • M. Daneshmand, R.R. Mansour
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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; 12(5-12):92 - 109. DOI:10.1109/MMM.2011.941417 · 1.67 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: Compact components for radio frequency (RF) front-ends realised in low-temperature co-fired ceramics (LTCC) are presented. The aim of this study was to highlight recent advances in realisation of different components for modern RF/microwave subsystems, stressing such attributes as compactness, wide bandwidth and operation in multiple bands. Two key components of every RF front-end are filters and couplers. To illustrate the feasibility of using LTCC technology to realise these components, several designs of filters and couplers are presented. Very compact LTCC ridge waveguide filter covering the whole US ultra-wide band is first discussed, followed by a dual-band LTCC ridge waveguide filter. Two types of wide-band couplers are shown: ridge waveguide couplers realised in LTCC and empty metallic waveguide and also a strip-line LTCC coupler. A common characteristic that will be shown is that the presented components by the authors are modelled using computer-aided design tools based on modal analysis for waveguides as well as commercially available finite-element tools. The shown examples have simulation results compared by different methods as well as some experimental results in LTCC and empty metallic waveguide, used to demonstrate the proposed approach.
    IET Microwaves Antennas & Propagation 07/2011; 5(8-5):870 - 876. DOI:10.1049/iet-map.2010.0371 · 0.97 Impact Factor
  • Fengxi Huang, Siamak Fouladi, R. R. Mansour
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    ABSTRACT: This paper presents the design and implementation of a new class of high-Q tunable dielectric resonator (DR) filters based on microelectromechanical systems (MEMS) switches. The use of MEMS switches results in the compact implementation of the proposed filter with near to zero DC power consumption for tuning and high tuning speed. The filter consists of two disk shape dielectric resonators with circular holes created in the center of each resonator. An initial prototype of the filter is assembled. The filter operates in TME mode at a center frequency of 4.8 GHz with a bandwidth of 21 MHz. Measurement results of this prototype demonstrate a tuning range of 160 MHz while the quality factor ranges from 1200-510 over the tuning range. The proposed tuning approach is applicable to other modes of dielectric resonator filters.
    IEEE MTT-S International Microwave Symposium digest. IEEE MTT-S International Microwave Symposium 06/2011; DOI:10.1109/MWSYM.2011.5973365
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    ABSTRACT: This paper introduces a finite difference time domain (FDTD) model for the electromagnetic simulation and analysis of a 4-channel deep brain stimulation (DBS) electrode. The analysis uses non-homogenous tissue models representing the gray and white tissue matter. The model includes the encapsulation layer of unexcitable tissues. Several low frequency signal models for brain tissue and the DBS electrode are developed to investigate the effect of the dielectric properties, stimulation pulse parameters and firing pattern (current steering) on controlling the field intensity distribution. These models are used to provide a quantitative formulation of the tissue-field interaction and the parameters influencing the electric field distribution within the brain tissue. The simulation results provide reference and benchmarking data for DBS electrode development.
    Neural Engineering (NER), 2011 5th International IEEE/EMBS Conference on; 01/2011
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    ABSTRACT: This study aims to investigate the electrodynamics of intra-cortical micro-electrodes and the effects of the different design parameters on the electrode electrical functionality. Finite difference time domain (FDTD) was used to create a low frequency electromagnetic model for the stimulation electrodes and the surrounding brain tissue. The paper also presents the effect of mechanical reinforcement metal planes on the electric field distribution within the brain tissue. The knowledge extracted from the simulation results will be used in the optimization of micro-electrode architectures and stimulation pads layouts in order to improve the electrodes functionality and biocompatibility.
    Neural Engineering (NER), 2011 5th International IEEE/EMBS Conference on; 01/2011
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    ABSTRACT: This paper presents the results of a comprehensive study on the performance of RF MEMS devices at cryogenic temperatures. More than 50 shunt capacitive RF MEMS switches are tested at room temperature (294 K) and liquid nitrogen temperature (77 K). The switches have various supports. The variation of the actuation voltage of each switch at room and cryogenic temperatures is investigated by mechanical simulation. The results show that the type of supports significantly affects the switch actuation voltage. In fact, depending on the shape of the supports the actuation voltage can decrease or increase at cryogenic temperatures. The hypothesis obtained from the analysis of the gold-based RF MEMS devices is confirmed by testing superconducting niobium-based RF MEMS devices, at liquid helium temperature (4 K). The RF performance of a capacitive shunt niobium-based RF MEMS switch and a niobium-based RF MEMS varactor show significant improvement of the insertion loss of the switch and an enormous enhancement of the quality factor of the varactor.
    Microwave Conference (EuMC), 2011 41st European; 01/2011
  • N. Zahirovic, R.R. Mansour, Ming Yu
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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

Publication Stats

2k Citations
154.06 Total Impact Points

Institutions

  • 1988–2013
    • University of Waterloo
      • Department of Electrical & Computer Engineering
      Ватерлоо, Ontario, Canada
  • 2011
    • University of Alberta
      Edmonton, Alberta, Canada
  • 2009
    • University of Regina
      Regina, Saskatchewan, Canada
    • University of New South Wales
      • School of Electrical Engineering and Telecommunications
      Kensington, New South Wales, Australia
  • 2008
    • University of Arkansas
      • Department of Electrical Engineering
      Fayetteville, AR, United States
    • Ain Shams University
      Al Qāhirah, Al Qāhirah, Egypt
  • 1989–2008
    • COM DEV International Ltd.
      Cambridge, Ontario, Canada
  • 2002–2004
    • Hochschule Bremen
      Bremen, Bremen, Germany
  • 2001
    • Canadian Space Agency
      Ottawa, Ontario, Canada
  • 1995–1996
    • University of Maryland, College Park
      • Department of Electrical & Computer Engineering
      College Park, MD, United States