Raafat R. Mansour

University of Waterloo, Ватерлоо, Ontario, Canada

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Publications (318)221.65 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a novel single-port multi-pole resonant sensor array fabricated on a novel Frame-Flex flexible substrate for a wearable epidermal ethanol sensor system, in which individual sensors carrying different functional polymers are brought together to share the same electrical input and output, and their resonance behavior along with inter-resonator coupling are captured through the single reflected array response curve ( S 11). The coupling-matrix readout extraction (CMRE) technique is then further proposed to determine, from the S 11 response, the changes in the diagonal-coupling coefficient, ∆M ii , which are used to identify different chemical analytes as the coupling signature. Two sensor arrays implementing different functional polymer sets—one with siloxane-based polymers and the other with crystalline-based polymers—are fabricated and tested under two selected mechanical loading conditions. The CMRE technique is then employed to obtain the coupling signatures of ethanol, methanol, acetone, and benzene on the arrays. It is successfully shown that the array response analyzed through the CMRE technique can clearly distinguish the presence of ethanol from other chemical interferents. For complicated mixtures of ethanol and other unwanted analytes, the distinctive coupling signatures obtained by CMRE can be used as a reliable data source fed to post-readout multi-variant analysis for pattern recognition.
    No preview · Article · Oct 2015 · IEEE Transactions on Microwave Theory and Techniques
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    ABSTRACT: A compact and low-loss MEMS-based phase shifter is proposed for microwave/millimetre-wave phased array antenna systems. The proposed phase shifter is an alumina-based CPW line, loaded with a variable series capacitor. The phase shifter uses an electromagnetic MEMS actuator to change the capacitor value. A simple three-mask surface micromachining process has been developed for device fabrication. The measurements at 26 GHz show a phase shift of 20°. The overall size of the phase shifter (including the actuator) is 0.5 × 1.5 mm. The measured average insertion loss is 0.75 dB with a variation of 0.4 dB for different phase shifts across the band from 24.5 to 26.5 GHz.
    No preview · Article · Jul 2015 · Electronics Letters
  • W.T. Chen · K.M.E. Stewart · R.R. Mansour · A. Penlidis
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    ABSTRACT: This paper introduces a novel undercoupled RF resonant sensor platform that enables gaseous phase chemical detection for passive sensor-embedded RF devices and RFIDs. The resonant sensor is implemented with an interdigital chemi-capacitor and a transmission-line inductor, thus only requiring a simple two-layer fabrication process. Its superior sensitivity at RF frequencies arises from the benefits of response amplification near resonance, as well as the shorter wavelength at radio-frequencies. Furthermore, the interdigital capacitor allows polymeric sensing materials to be directly deposited atop, thereby improving fabrication repeatability. The sensor prototypes are loaded with three different polymeric sensing materials – OV225, OV275, and SC201(SXFA) – aiming to detect certain pre-perspiratory transdermal biomarkers including gaseous phase ethanol, methanol, and benzene. Their respective responses are recorded in terms of three distinctive RF parameters – resonant frequency shift (Δf0), response amplitude change (ΔS11), and response delay change (ΔGD11) – from which the sensitivities of these sensors are determined, and their selectivities with respect to the sample gas analytes are subsequently characterized. Finally, evaluation of the response signatures of the polymeric sensing materials to each gas analyte enables future development of sensor array systems that can distinguish desired analytes from unwanted interferents.
    No preview · Article · Jul 2015 · Sensors and Actuators A Physical
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    ABSTRACT: We have designed single-bit comparators and multi-bit flash analog-to-digital converters (ADCs) using three flavors of periodic comparators; one flavor uses a differential “quasi-one-junction” SQUID (DQOS) comparator, the second use a differential SQUID wheel comparator (DSW) and the third uses a symmetric differential SQUID wheel comparator (SDSW) with time-interleaved clocks. We have also developed a new performance analysis scheme that enables full reconstruction of input signal using a single-bit comparator. The signal is reconstructed based on multiple beat frequency measurements that track the position of the comparator thresholds in response to a dc offset to the input signal. In addition, to eliminate the frequency dependent distortions resulting from impedance mismatches over wide bandwidths, the signal and clock distribution network have been optimized using EM simulations. For distributing the clock signal to the multi-bit comparators, a 50 Ω coplanar transmission line has been designed. Test results for a 1-bit DSW comparator demonstrates a performance of 4.5 bits of resolution in Gray code for a beat frequency test using a 20 GHz input signal and 5.3 bits for 10 GHz input. 4 and 8-bit versions of the flash ADC with a DQOS comparator and a 3-bit time-interleaved ADC using the SDSW comparator have also been designed. The DQOS ADC has been tested up to 25 GHz input signal frequency with performance of 4.3 bits of resolution in Gray code for 19.7 GHz input signal. The time-interleaved ADC performance is 4.3 bits for a 15 GHz beat frequency test with an effective sampling rate of 30 GHz.
    No preview · Article · Jun 2015 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Poly (2,5-dimethyl aniline) (P25DMA), with and without NiO and ZnO as dopants, is evaluated as a sensing material for ethanol to detect transdermal ethanol emissions. Three sensing materials—P25DMA, P25DMA doped with 20 wt % NiO, and P25DMA doped with 20 wt % ZnO—are eventually deposited onto a radio frequency identification sensor. The limit of detection for the materials is found to be 3, 24, and 420 ppm, respectively. Also, all three sensing materials are selective toward ethanol with benzene and methanol used as interferents. The response and recovery times are also measured for the three sensing materials and are in the order of seconds, which is acceptable for a transdermal ethanol sensor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42259.
    No preview · Article · Apr 2015 · Journal of Applied Polymer Science
  • N. Sarkar · D. Strathearn · G. Lee · M. Olfat · R.R. Mansour
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    ABSTRACT: This paper reports the highest resolution achieved with a single-chip Atomic Force Microscope (sc-AFM). Images of a 20nm AFM calibration standard were obtained to show, for the first time, that single-chip instruments may obtain a vertical resolution comparable to state-of-the-art instruments at a minuscule fraction of the size (volume=1/1,000,000) and cost (1/1000). A maskless, 2-step release process is performed on CMOS chips in order to obtain devices that can image a sample without the need for any off-chip scanning or sensing components. We report a four-fold improvement in resolution when compared to previously reported sc-AFMs, enabling metrology for nanoscale manufacturing using MEMS AFM technology.
    No preview · Article · Feb 2015 · Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)
  • Saman Nazari Nejad · Raafat Mansour

    No preview · Article · Jan 2015 · IEEE Transactions on Magnetics
  • Maher Bakri-Kassem · Raafat R. Mansour
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    ABSTRACT: Latching RF MEMS Switches of Single-Pole-Single-Throw (SPST), Single-Pole-Double-Throw (SPDT) and Single-Pole-Triple-Throw (SP3T) types are proposed. The switches are built of a 20 μm thick nickel layer covered with a plated 2 μm gold on the top and side walls of nickel layer eliminating any potential warping due to thermal mismatch. The switches are actuated using a high stroke latching thermal actuator that exhibits a 32 μm displacement with a dc power of 250 mW under ambient pressure at 25 ° C (298 ° K) and 153 mW under vacuum at -193° C (80 ° K). The measured velocity for the actuator is 2.3 μm/msec. The RF measurement of the SPST switch is done under ambient and vacuum and over a wide range of temperatures from 25 ° C (298 ° K) to -193° C (80 ° K). The switches survived a temperature cyclic test from 25 ° C (298 ° K) to 85 ° C (358 ° K) with a total variation of 0.2 dB in insertion loss. The switch demonstrates a worst IP3 of 60.14 dBm and high power handling capabilities that exceeds 30 Watt, only tested for an hour in 1 cycle. The RF performance of the SPST, SPDT and SP3T exhibits a worst insertion loss of 0.8 dB, 1.2 dB and 1.5 dB up to 40 GHz, 40 GHz and 18 GHz, respectively.
    No preview · Article · Jan 2015 · IEEE Transactions on Microwave Theory and Techniques
  • Sara S. Attar · Paul Laforge · Raafat R. Mansour

    No preview · Conference Paper · Oct 2014
  • Desireh Sh-Asanjan · Raafat R. Mansour
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    ABSTRACT: This paper presents a simple analysis for analyzing the power handling capability of microwave resonators and filters. The method relates the resonator stored energy obtained by circuit theory to that obtained by HFSS simulations. The method is used to investigate the power handing capability of conventional combline resonators as well as non-traditional coaxial resonator configurations. A novel resonator configuration is proposed, offering a 15% improvement in power handling capability in comparison with traditional combline resonators. Simulation and measured results are given for a 4-pole filter employing the proposed resonator.
    No preview · Conference Paper · Oct 2014
  • Jorge A. Ruiz-Cruz · Mohamed M. Fahmi · Raafat R. Mansour
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    ABSTRACT: This paper addresses the design of a single-pole multiple-throw (SP12T) switch with twelve output ports in waveguide technology. The cumbersome and bulky routing waveguide networks required to deal with large number of ports in waveguide switches are reduced to a very compact structure that uses ridge waveguide junctions. The switch concept is provided by short circuit elements inside the ridge waveguides that select the signal path inside the waveguide structure. This concept avoids the use of complex rotary systems to provide path switching, resulting in an extremely compact network. A SP12T waveguide switch is built and tested to validate the concept. The fabricated prototype integrates the transitions to SMA outputs and metallic posts for the short-circuit elements. The experimental results show that the proposed approach provides a very compact structure, with design parameters that can be optimized depending on the targeted application
    No preview · Conference Paper · Oct 2014
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    ABSTRACT: A novel nickel/gold based electroplated 4-bit RF MEMS phase shifter is designed, fabricated and tested. The proposed design can candle high power and utilizes CPW transmission lines that use 8 latching SPDT RF MEMS switches that can work at 80°K. The design is based on 4 cascaded phase shifting units where every unit has two different electrical lengths of CPW transmission lines. Every unit has one common electrical length that is used as a reference where the second electrical length CPW has different electrical length. The second electrical length CPW in every unit is designed to give a relatively different phase shift once it is engaged in. The worst measured insertion loss and return loss are-6 dB and-16 dB, respectively, at 13 GHz with a phase shift of almost-125 degrees. The phase shifter is built using high resistive silicon substrate using MetalMUMPs process.
    No preview · Conference Paper · Oct 2014

  • No preview · Conference Paper · Oct 2014
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    ABSTRACT: A novel niobium-based superconducting RF microelectromechanical system (MEMS) varactor is presented, and its mechanical performance is characterized at both room and cryogenic temperatures. The device is amenable to integration with superconducting microelectronics (SME) technology. The RF performance of the varactor at cryogenic (4 K) temperatures indicates capacitance variations from 40 fF to 0.46 pF. Hence, the varactor is used to design a monolithically integrated tunable resonator, whose measured results at cryogenic temperature show a sweep of frequency from 2.62 to 2.54 GHz and a discrete shift from 2.54 to 1.95 GHz, when the biasing voltage varies from 0 to 58 V. Using the same fabrication process, a fixed niobium-based three-pole bandstop filter is designed with a center frequency of 2 GHz and a size of 5 mm × 0.85 mm. Tunable versions of the three-pole filter using semiconductor varactors and monolithically integrated MEMS varactors are also designed and characterized at 4 K. The results of the tunable bandstop filters are analyzed both theoretically and experimentally.
    Full-text · Article · Aug 2014 · IEEE Transactions on Applied Superconductivity
  • K.Y. Chan · Rodica Ramer · Raafat R. Mansour · Y. Jay Guo
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    ABSTRACT: A novel reconfigurable millimeter-wave bandpass filter (BPF) capable of operating between 60 GHz and the E-band, with a good channel isolation, is presented. This fully integrated filter is designed with all reconfigurable elements embedded for compactness. A new method that increases fractional bandwidths is introduced. It uses inductively coupled invertersbut does not require tuning. New circuit models are provided for these inverters, reconfigurable resonators, and the reconfigurable bandstop stubs. The compact BPF achieved a footprint of only 4.75 mm $,times,$ 3.75 mm. Measurements for the filters show good agreement with the simulation results.
    No preview · Article · Aug 2014 · IEEE Microwave and Wireless Components Letters
  • Raafat R. Mansour · Fengxi Huang · Siamak Fouladi · Winter Dong Yan · Mitra Nasr
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    ABSTRACT: High-Q tunable filters are in demand in both wireless and satellite applications. The need for tunability and configurability in wireless systems arises when deploying different systems that coexist geographically. Such deployments take place regularly when an operator has already installed a network and needs to add a new-generation network, for example, to add a long-term evolution (LTE) network to an existing third-generation (3G) network. The availability of tunable/reconfigurable hardware will also provide the network operator the means for efficiently managing hardware resources, while accommodating multistandards requirements and achieving network traffic/capacity optimization. Wireless systems can also benefit from tunable filter technologies in other areas; for example, installing wireless infrastructure equipment, such as a remote radio unit (RRU) on top of a 15-story high communication tower, is a very costly task. By using tunable filters, one installation can serve many years since if there is a need to change the frequency or bandwidth, it can be done through remote electronic tuning, rather than installing a new filter. Additionally, in urban areas, there is a very limited space for wireless service providers to install their base stations due to expensive real estate and/or maximum weight loading constrains on certain installation locations such as light poles or power lines. Therefore, once an installation site is acquired, it is natural for wireless service providers to use tunable filters to pack many functions, such as multistandards and multibands, into one site.
    No preview · Article · Jul 2014 · IEEE Microwave Magazine
  • Sara S. Attar · Sormeh Setoodeh · Raafat R. Mansour · Deepnarayan Gupta
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    ABSTRACT: A niobium-based superconducting dc-contact RF microelectromechanical systems switch is introduced and is thoroughly analyzed. The switch is amenable to integration with superconducting microelectronics technology. A comparison of the switch's RF performance at room and cryogenic temperatures indicates a significant improvement in the insertion loss of the switch when niobium is superconducting. The mechanical characteristic of the switch at extremely low temperature (4 K) is also investigated. The switch exhibits an increase of 18% on the actuation voltage as the temperature changes from 293 K (room temperature) to 4 K. A niobium superconducting tunable resonator is designed and tested, employing the proposed switch as the tuning element in the form of a switched capacitor bank monolithically integrated with the resonator. The measured results at 4 K clearly indicate the discrete resonance frequency states of the resonator. A three-pole tunable bandstop filter is designed with a center frequency of 1.2 GHz and dimensions of only 5 mm $times$ 1.2 mm. The results demonstrate a tuning range of 12% while maintaining an excellent RF response of the filter.
    No preview · Article · Jul 2014 · IEEE Transactions on Microwave Theory and Techniques
  • W.T. Chen · R.R. Mansour · J. Carroll
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    ABSTRACT: This paper presents a novel application of RF-filter parameter extraction techniques with coupling matrix model to obtain decoupled capacitive sensor readings from the S11 of a single-port, multi-resonator passive RF resonant sensor array. As an example application, two dual-resonator sensor arrays loaded with four selected functional polymers are implemented to allow ethanol and acetone identification. Through the parameter extraction techniques, the changes in capacitances of the sensor pair are obtained as chemical signatures to differentiate the presence of ethanol from acetone.
    No preview · Conference Paper · Jun 2014
  • Li Zhu · Raafat R. Mansour · Ming Yu
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    ABSTRACT: This paper outlines a new class of diplexers realized using a combination of dual-band cavities and single-band cavities. The proposed diplexer does not require junctions and can achieve similar performance with fewer cavities, thus significantly reducing the size of the diplexer when compared to traditional approaches. The concept is potentially applicable to most dual-band cavities as demonstrated in this paper using rectangular waveguide cavities. A unique layout is proposed that combines the use of dual-band cavities operating in TE101 and TE011 modes as well as single-band cavities operating in TE101 or TE102 mode. The result is a diplexer that is very compact in size while offering increased Q and an improved spurious free window. To verify the concept a 4th order Ku-band diplexer is designed, manufactured, and tested to allow comparison to a traditional design.
    No preview · Conference Paper · Jun 2014
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    ABSTRACT: We introduce a new 3-D flexible microelectrode array for high performance electrographic neural signal recording and stimulation. The microelectrode architecture maximizes the number of channels on each shank and minimizes its footprint. The electrode was implemented on flexible polyimide substrate using microfabrication and thin-film processing. The electrode has a planar layout and comprises multiple shanks. Each shank is three mm in length and carries six gold pads representing the neuro-interfacing channels. The channels are used in recording important precursors with potential clinical relevance and consequent electrical stimulation to perturb the clinical condition. The polyimide structure satisfied the mechanical characteristics required for the proper electrode implantation and operation. Pad post-processing technique was developed to improve the electrode electrical performance. The planar electrodes were used for creating 3-D "Waterloo Array" microelectrode with controlled gaps using custom designed stackers. Electrode characterization and benchmarking against commercial equivalents demonstrated the superiority of the Flex electrodes. The Flex and commercial electrodes were associated with low-power implantable responsive neuro-stimulation system. The electrodes performance in recording and stimulation application was quantified through in vitro and in vivo acute and chronic experiments on human brain slices and freely-moving rodents. The Flex electrodes exhibited remarkable drop in the electric impedance (100 times at 100 Hz), improved electrode-electrolyte interface noise (dropped by 4 times) and higher signal-to-noise ratio (3.3 times).
    Full-text · Article · May 2014 · IEEE Transactions on Neural Systems and Rehabilitation Engineering

Publication Stats

3k Citations
221.65 Total Impact Points


  • 1985-2015
    • University of Waterloo
      • Department of Electrical & Computer Engineering
      Ватерлоо, Ontario, Canada
  • 2011
    • University of Alberta
      Edmonton, Alberta, Canada
  • 1988-2011
    • COM DEV International
      Кембридж, Ontario, Canada
  • 2008
    • University of Arkansas
      • Department of Electrical Engineering
      Fayetteville, AR, United States
  • 2002
    • 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