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Abbas Tamijani

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Srinath Gopalan

Anis Nurashikin Nordin

International Islamic University Malaysia

Coventry University

Abubakar Tafawa Balewa University, Bauchi Nigeria

Universidad Politécnica de Valencia

Yolanda Jiménez

University of Valencia

Matthias Schreiter

María Isabel Rocha Gaso

Universidad de Quintana Roo

Dr Sultan Akhtar

Imam Abdulrahman bin Faisal University

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Papers by Abbas Tamijani

Integration of a Film Bulk Acoustic Resonator with Microfluidic Channels for Biomedical Sensing in Liquid

This paper reports an integration of microfluidic channels with a film bulk acoustic resonator (F... more This paper reports an integration of microfluidic channels with a film bulk acoustic resonator (FBAR) for in liquid biomedical sensing applications. The device consists of a zinc oxide (ZnO) film based longitudinal mode FBAR and parylene encapsulated microfluidic channels. By confining the liquid with the height comparable to the acoustic wavelength of the FBAR in the microfluidic channels, the quality factor (Q) of the resonating system significantly increases, resulting in very high sensitivity FBAR sensor for liquid samples. We demonstrate a FBAR with Q up to 120, an improvement of more than 8 times over that of existing FBARs in liquid. A bio-molecular (streptavidine) sensing test presents a sensitivity of 638 Hz cm 2 /ng and an extremely fine resolution of 2.025 ng/cm 2 of the sensor.

Evaluation of a Novel Topology for MEMS Programmable Reflectarray Antennas

IEEE Transactions on Microwave Theory and Techniques, 2009

ABSTRACT This paper presents a programmable reflectarray topology for passive beamforming at mill... more ABSTRACT This paper presents a programmable reflectarray topology for passive beamforming at millimeter-wave frequencies. This topology relies on reconfigurable antenna-filter-antenna (AFA) elements and has a multilayer structure that makes it suitable for implementation as a monolithic MEMS device. We address different aspects of design, modeling, and characterization of the AFA elements and the reflectarray. A 2-bit reflective AFA element is introduced and studied using full-wave and hybrid models. An approximate bistatic reflectance model is proposed and used in a ray-based formulation to predict the radiation pattern of the reflectarray. The principle of operation, scanning performance, and modeling approach are validated experimentally using proof-of-concept reflectarray prototypes designed for 35 GHz. Pattern measurements in offset-fed and folded center-fed configurations show that the proposed topology is capable of wide-angle scanning in two dimensions. The measured scan loss is less than 2 dB for up to 45?? scan in both E - and H -planes. The cross-pol level is &lt; -11 dB in all cases, and the worst case sidelobe level is -9 dB. A near-scan-blindness behavior is observed for 60?? scan in the E -plane. These results are consistent with the simulations, indicating the effectiveness of the bistatic reflectance model.

2010 Index IEEE Transactions on Instrumentation and Measurement Vol. 59

IEEE Transactions on Instrumentation and Measurement, 2010

This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this... more This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this periodical during 2010, and items from previous years that were commented upon or corrected in 2010. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

Miniature and Tunable Filters

,), a miniature three-pole filter was developed with 8.6% bandwidth based on high- MEMS bridge ca... more ,), a miniature three-pole filter was developed with 8.6% bandwidth based on high- MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate ( , ). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 0.2 and a midband insertion loss of 3.85‐4.15 dB. The of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The increases to 50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150‐300 MHz s.

A millimetre-wave bandpass filter–lens array

IET Microwaves, Antennas & Propagation, 2007

A filter-lens array (FLA) is a planar array of bandpass integrated antenna-filter-antenna (AFA) e... more A filter-lens array (FLA) is a planar array of bandpass integrated antenna-filter-antenna (AFA) elements which are stagger-tuned in the vicinity of a centre frequency, so as to provide the phase shift required for transforming spherical and planar wavefronts. Due to the filtering response of the AFA elements, FLA presents a bandpass gain and can act as a combination of a conventional lensarray and a filter. An FLA structure is demonstrated with f/D ¼ 1.25 and 8.2% bandwidth at 35 GHz. This FLA is composed of 137 AFA elements and fabricated on two three-inch glass wafers (e r ¼ 4:45). A gain of 25.6 dBi and a total efficiency of 45% have been measured at 35 GHz. The Ka-band FLA shows a low-loss scanning performance for up to at least +308 in the H-plane and +208 in the E-plane.

Study of 2-bit Antenna&ndash;Filter&ndash;Antenna Elements for Reconfigurable Millimeter-Wave Lens Arrays

IEEE Transactions on Microwave Theory and Techniques, 2006

ABSTRACT This paper presents a new reconfigurable antenna-filter-antenna (AFA) element based on s... more ABSTRACT This paper presents a new reconfigurable antenna-filter-antenna (AFA) element based on slot antennas and switchable resonators. This reconfigurable AFA can operate in four modes of operation as a three- or four-pole filter, and yields a 2-bit variable phase delay. As a result, the multimode AFA can be used as the building block of 2-bit adaptive lens arrays. This paper details design, modeling, and miniaturization of the reconfigurable AFA, and demonstrates its performance through preconfigured prototypes. The proposed AFA has a loss of 1.4-1.6 dB measured at 32 GHz in both three- and four-pole filter modes, and exhibits a frequency response that is almost insensitive to the angle of incidence. Several proof-of-concept fixed lens arrays have been also fabricated for output beams scanned to 0deg, 15deg, 30deg, 45deg, and 60deg in the E- and H-plane. The measurement results show that the output beam can be scanned to plusmn60deg in both principle planes, with a worst case sidelobe level of less than -11 dB and a scan loss that hardly exceeds the theoretical limit

A Programmable Lens-Array Antenna With Monolithically Integrated MEMS Switches

IEEE Transactions on Microwave Theory and Techniques, 2009

ABSTRACT This paper describes a reconfigurable millimeter-wave lens-array antenna based on monoli... more ABSTRACT This paper describes a reconfigurable millimeter-wave lens-array antenna based on monolithically integrated microelectromechanical systems (MEMS) switches. This device is constructed as a planar array of 2-bit programmable MEMS antenna-filter-antenna (AFA) unit cells that are used to provide a 1-D programmable ldquoaperture transfer functionrdquo between the input and output wavefronts. The fully integrated device consists of 484 (22 times 22) AFA elements and 2420 switches. Switches, bias lines, antennas, and the rest of the RF structure are fabricated on two quartz wafers (epsiv r = 3.8, tandelta = 0.002) that are subsequently stacked using adhesive bonding to form the tri-layer metal structure of the AFA array. The bonded structure also forms a package for the MEMS switches. This paper investigates the design and fabrication issues and presents the measured data related to yield and frequency response of this lens-array. It also characterizes the performance of this device as a steerable antenna. Measured results show that this lens-array can be used to steer the beam of a low gain horn antenna to plusmn40deg in either the E- or the H-plane. For the fabricated prototype, the yield is estimated to be 50% for the best region of the array, resulting in a relatively high insertion loss and sidelobe level.

Antenna–Filter–Antenna Arrays as a Class of Bandpass Frequency-Selective Surfaces

IEEE Transactions on Microwave Theory and Techniques, 2004

A method is introduced for designing bandpass frequency-selective surfaces (FSSs) using arrays of... more A method is introduced for designing bandpass frequency-selective surfaces (FSSs) using arrays of antenna-filter-antenna (AFA) modules. An AFA module is a filter with radiation ports, which is obtained by integrating two antennas and a nonradiating resonant structure in between. AFA modules are designed based on circuit models and microwave filter design techniques. Three types of these AFA modules are designed using microstrip antennas and coplanar-waveguide resonators, and are used to form FSSs with three-and four-pole shaped bandpass response at 35 GHz. FSS structures are formed by arraying these modules in a periodic grid with an optimal cell size. The proposed concept and the design method are validated using numerical simulation (finite-element method), as well as experimental results.

An affordable millimeter-wave beam-steerable antenna using interleaved planar subarrays

IEEE Transactions on Antennas and Propagation, 2003

Design and fabrication aspects of an affordable planar beam steerable antenna array with a simple... more Design and fabrication aspects of an affordable planar beam steerable antenna array with a simple architecture are considered in this paper. Grouping the elements of a phased array into a number of partially overlapped subarrays and using a single phase shifter for each subarray, generally results in a considerable reduction in array size and manufacturing costs. However, overlapped subarrays require complicated corporate feed networks and array architectures that cannot be easily implemented using planar technologies. In this paper a novel feed network and array architecture for implementing a planar phased array of microstrip antennas is presented that enables the fabrication of low-sidelobe, compact, beam-steerable millimeter-wave arrays and facilitates integration of the RF front-end electronics with the antenna structure. This design uses a combination of series and parallel feeding schemes to achieve the desired array coefficients. The proposed approach is used to design a three-state switched-beam phased array with a scanning width of 10. This phased array which is composed of 80 microstrip elements, achieves a gain of 20 dB, a sidelobe level of 19 dB and a 10-dB bandwidth of 6.3% for all states of the beam. The antenna efficiency is measured at 33-36% in band. It is shown that the proposed feeding scheme is insensitive to the mutual coupling among the elements.

Oscillatory <formula formulatype="inline"><tex Notation="TeX">$Q$</tex> </formula> Factor in Film Bulk Acoustic Resonators With Integrated Microfluidic Channels

IEEE Sensors Journal, 2011

When a film bulk acoustic resonator (FBAR) is coupled to a liquid layer with thickness comparable... more When a film bulk acoustic resonator (FBAR) is coupled to a liquid layer with thickness comparable to the acoustic wavelength, the factor varies in a damped oscillatory pattern with the liquid thickness. This letter reports an analytical modeling and experimental demonstration of this behavior by integrating microfluidic channels to MEMS-based FBARs. It is found that assumes its maxima and minima when the channel thickness is an odd multiple of quarter-wavelength and a multiple of half-wavelength, respectively. The microfluidics integrated FBARs achieve a improvement of over fully immersed FBARs, showing the potential of use as high-resolution sensors involving liquids.

A Fully Passive Wireless Microsystem for Recording of Neuropotentials Using RF Backscattering Methods

Journal of Microelectromechanical Systems, 2011

The ability to safely monitor neuropotentials is essential in establishing methods to study the b... more The ability to safely monitor neuropotentials is essential in establishing methods to study the brain. Current research focuses on the wireless telemetry aspect of implantable sensors in order to make these devices ubiquitous and safe. Chronic implants necessitate superior reliability and durability of the integrated electronics. The power consumption of implanted electronics must also be limited to within several milliwatts to microwatts to minimize heat trauma in the human body. In order to address these severe requirements, we developed an entirely passive and wireless microsystem for recording neuropotentials. An external interrogator supplies a fundamental microwave carrier to the microsystem. The microsystem comprises varactors that perform nonlinear mixing of neuropotential and fundamental carrier signals. The varactors generate third-order mixing products that are wirelessly backscattered to the external interrogator where the original neuropotential signals are recovered. Performance of the neurorecording microsystem was demonstrated by wireless recording of emulated and in vivo neuropotentials. The obtained results were wireless recovery of neuropotentials as low as approximately 500 microvolts peak-to-peak (µV pp) with a bandwidth of 10 Hz to 3 kHz (for emulated signals) and with 128 epoch signal averaging of repetitive signals (for in vivo signals). [2010-0338] Index Terms-Backscattering, biomicroelectromechanical systems, neural recording, neural telemetry, radio frequency (RF) identification (RFID). I. INTRODUCTION T HE AIM OF developing wireless neurointerfaces is to resolve complex challenges underlying basic understanding Manuscript

In-Liquid Quality Factor Improvement for Film Bulk Acoustic Resonators by Integration of Microfluidic Channels

IEEE Electron Device Letters, 2009

We demonstrate a significant improvement in the quality factor (Q) of film bulk acoustic resonato... more We demonstrate a significant improvement in the quality factor (Q) of film bulk acoustic resonators (FBARs) in liquid environments via the integration of microfluidic channels. Our device consists of a longitudinal-mode excited zinc oxide (ZnO) FBAR and parylene-encapsulated microfluidic channels. Considerable enhancement in the Q of the resonant system is obtained by confining the liquid in the microfluidic channels of thickness comparable to the acoustic wavelength. The improved FBAR achieves Q values of up to 120, which represents an improvement of a factor of eight over those of current state-of-the-art devices.

Miniature and tunable filters using mems capacitors

IEEE Transactions on Microwave Theory and Techniques, 2003

Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tun... more Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tunable bandpass filters at 18-22 GHz. Using coplanar waveguide transmission lines on a quartz substrate (= 3 8, tan = 0 0002), a miniature three-pole filter was developed with 8.6% bandwidth based on high-MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate (= 4 6, tan = 0 006). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 0.2% and a midband insertion loss of 3.85-4.15 dB. The IIP 3 of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The IIP 3 increases to 50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150-300 MHz s. Index Terms-Filters, microelectromechanical system (MEMS), MEMS varactors, MEMS devices, miniature filters, tunable filters. I. INTRODUCTION L OW-LOSS bandpass filters are the basic components of transceivers, either as band-select or image-reject units. In the highly integrated systems, however, design of the bandpass filters is generally subject to serious size constraints. In active phased arrays, for example, one filter is required per antenna element, and the filter size cannot exceed a fraction of the free-space wavelength, which is the typical cell size in the array. Also, in multiband receivers, a single filter cannot fulfill the filtering requirements for all operating bands and multiple filters must be used, which proves inconvenient in most communication systems. An ideal solution in such circumstances is a miniature filter that can be tuned for different bands. The existing work in the area of filter miniaturization includes loading of the transmission-line resonators with lumped elements [1],

A Planar Filter-Lens Array For Millimeter- Wave Applications

Planar lens arrays have been addressed by a number of researchers in the existing literature [1][... more Planar lens arrays have been addressed by a number of researchers in the existing literature [1][2] [3][4]. In these works, focusing is obtained by using arrays of receive and transmit antennas which are connected by transmission-line sections of appropriate lengths. Presence of these line sections has adverse effects on the frequency-response and complicates the layout design for large arrays.

An experimental verification of a microwave backscatter tag for recording neural signals

2008 IEEE Antennas and Propagation Society International Symposium, 2008

... Neural Signals Muhammad F. Farooqui (1) , Junseok Chae (1) , Bruce Towe (1) , and Abbas Abbas... more

Oscillating behavior of quality factor of a film bulk acoustic resonator in liquids

TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference, 2009

ABSTRACT When a film bulk acoustic resonator (FBAR) is coupled to a thin liquid layer, the qualit... more ABSTRACT When a film bulk acoustic resonator (FBAR) is coupled to a thin liquid layer, the quality factor (Q) of the resonator varies in a damped oscillatory pattern versus the liquid thickness. This paper reports this behavior with an analytical modeling and experimental demonstration of it. The thin liquid layer with thickness comparable to the acoustic wavelength is realized by integrating a microfluidic channel to the FBAR. Q assumes its maxima (up to 150) and minima (as low as 50) when the channel thickness is an odd multiple of quarter-wavelength and a multiple of half-wavelength, respectively. We also present a bio-molecular detection test for aptamer immobilization and thrombin binding as a proof-of-concept sensing application.

Planar implementation of the partially overlapped subarrays for millimeterwave beam steerable antenna applications

2002 IEEE MTT-S International Microwave Symposium Digest (Cat. No.02CH37278), 2000

ABSTRACT Grouping the elements of a phased array into the partially overlapped subarrays with in-... more ABSTRACT Grouping the elements of a phased array into the partially overlapped subarrays with in-phase excited elements amid using a single phase shifter per subarray has been studied in the past as an approach for reducing the number of phase shifters. Overlapped subarrays require complicated: feeding scenarios, however, that cannot be easily implemented in planar technologies. This paper focuses on a planar implementation which is especially useful for compact millimeterwave arrays and facilitates integration of the antenna and electronics. This design uses a unique combination of series and parallel feeding schemes to form a standing wave array of. microstrip elements. The proposed feeding scheme is theoretically insensitive to the mutual coupling between the elements

A simplified scanning scheme for millimeter-wave active phased arrays

IEEE Antennas and Propagation Society International Symposium. 2001 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.01CH37229), 2000

ABSTRACT A novel and efficient scanning technique using a discrete phasing scheme and proper patt... more ABSTRACT A novel and efficient scanning technique using a discrete phasing scheme and proper pattern synthesis is presented. As in many other beamforming applications, precise control of the array coefficients is crucial for a successful implementation of the array design. A resonant standing wave feeding network is used to ensure proper excitation of the radiating elements. The new scanning technique proves to be very effective in reducing the complexity of the phasing network and hence the fabrication costs. The effectiveness of this simplification procedure becomes more evident when high resolution and a large number of scanning angles are required. In the applications where expensive phase shifters are the most costly and sensitive parts of the antenna system, when the scanning width is relatively small, the new technique can provide a cost-effective alternative

A negative-index annular lens device for feeding 360°-steerable ring arrays

2010 IEEE Antennas and Propagation Society International Symposium, 2010

This paper describes the design of a negative-index annular lens device intended for use as the c... more This paper describes the design of a negative-index annular lens device intended for use as the core element of the beam-forming network in circular ring electronically-steerable arrays (ESA). Circular ring ESA's offer the benefit of full 3600 scan coverage, and hence are ideal for application in mobile and portable communication devices. The proposed lens device can be used as an interface between the front-end electronic and the antenna elements, as depicted in Fig. 1. The lens has an annular geometry. The antenna ports are defined along the outer rim and electronic (or beam) ports lie on the inner rim of the device. The lens is made of inhomogeneous material, where the refractive index varies with radius. Antenna ports can be extended using equal lengths of transmission line to feed an array with a radius greater than that of the lens.

Low-loss bandpass antenna-filter-antenna arrays for applications in quasi-optical systems

2005 European Microwave Conference, 2005

ABSTRACT A new type of 3-pole frequency selective surface (FSS) is proposed as a low-loss bandpas... more ABSTRACT A new type of 3-pole frequency selective surface (FSS) is proposed as a low-loss bandpass filter for quasi-optical applications. This FSS is realized as a uniform array of antenna-filter-antenna (AFA) elements. Each AFA element is a three layer structure consisting two slot antennas and a stripline resonator. A Chebyshev bandpass AFA with 9.5% bandwidth was designed for 32 GHz and fabricated on two layers of Teflon substrates (εr=2.2, tan δ=0.0009). The maximum measured in-band insertion loss for this design is &amp;lt;0.5 dB, which is limited by the in-band ripple of the Chebyshev response.

Integration of a Film Bulk Acoustic Resonator with Microfluidic Channels for Biomedical Sensing in Liquid

This paper reports an integration of microfluidic channels with a film bulk acoustic resonator (F... more This paper reports an integration of microfluidic channels with a film bulk acoustic resonator (FBAR) for in liquid biomedical sensing applications. The device consists of a zinc oxide (ZnO) film based longitudinal mode FBAR and parylene encapsulated microfluidic channels. By confining the liquid with the height comparable to the acoustic wavelength of the FBAR in the microfluidic channels, the quality factor (Q) of the resonating system significantly increases, resulting in very high sensitivity FBAR sensor for liquid samples. We demonstrate a FBAR with Q up to 120, an improvement of more than 8 times over that of existing FBARs in liquid. A bio-molecular (streptavidine) sensing test presents a sensitivity of 638 Hz cm 2 /ng and an extremely fine resolution of 2.025 ng/cm 2 of the sensor.

Evaluation of a Novel Topology for MEMS Programmable Reflectarray Antennas

IEEE Transactions on Microwave Theory and Techniques, 2009

ABSTRACT This paper presents a programmable reflectarray topology for passive beamforming at mill... more ABSTRACT This paper presents a programmable reflectarray topology for passive beamforming at millimeter-wave frequencies. This topology relies on reconfigurable antenna-filter-antenna (AFA) elements and has a multilayer structure that makes it suitable for implementation as a monolithic MEMS device. We address different aspects of design, modeling, and characterization of the AFA elements and the reflectarray. A 2-bit reflective AFA element is introduced and studied using full-wave and hybrid models. An approximate bistatic reflectance model is proposed and used in a ray-based formulation to predict the radiation pattern of the reflectarray. The principle of operation, scanning performance, and modeling approach are validated experimentally using proof-of-concept reflectarray prototypes designed for 35 GHz. Pattern measurements in offset-fed and folded center-fed configurations show that the proposed topology is capable of wide-angle scanning in two dimensions. The measured scan loss is less than 2 dB for up to 45?? scan in both E - and H -planes. The cross-pol level is &lt; -11 dB in all cases, and the worst case sidelobe level is -9 dB. A near-scan-blindness behavior is observed for 60?? scan in the E -plane. These results are consistent with the simulations, indicating the effectiveness of the bistatic reflectance model.

2010 Index IEEE Transactions on Instrumentation and Measurement Vol. 59

IEEE Transactions on Instrumentation and Measurement, 2010

This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this... more This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this periodical during 2010, and items from previous years that were commented upon or corrected in 2010. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

Miniature and Tunable Filters

,), a miniature three-pole filter was developed with 8.6% bandwidth based on high- MEMS bridge ca... more ,), a miniature three-pole filter was developed with 8.6% bandwidth based on high- MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate ( , ). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 0.2 and a midband insertion loss of 3.85‐4.15 dB. The of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The increases to 50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150‐300 MHz s.

A millimetre-wave bandpass filter–lens array

IET Microwaves, Antennas & Propagation, 2007

A filter-lens array (FLA) is a planar array of bandpass integrated antenna-filter-antenna (AFA) e... more A filter-lens array (FLA) is a planar array of bandpass integrated antenna-filter-antenna (AFA) elements which are stagger-tuned in the vicinity of a centre frequency, so as to provide the phase shift required for transforming spherical and planar wavefronts. Due to the filtering response of the AFA elements, FLA presents a bandpass gain and can act as a combination of a conventional lensarray and a filter. An FLA structure is demonstrated with f/D ¼ 1.25 and 8.2% bandwidth at 35 GHz. This FLA is composed of 137 AFA elements and fabricated on two three-inch glass wafers (e r ¼ 4:45). A gain of 25.6 dBi and a total efficiency of 45% have been measured at 35 GHz. The Ka-band FLA shows a low-loss scanning performance for up to at least +308 in the H-plane and +208 in the E-plane.

Study of 2-bit Antenna&ndash;Filter&ndash;Antenna Elements for Reconfigurable Millimeter-Wave Lens Arrays

IEEE Transactions on Microwave Theory and Techniques, 2006

ABSTRACT This paper presents a new reconfigurable antenna-filter-antenna (AFA) element based on s... more ABSTRACT This paper presents a new reconfigurable antenna-filter-antenna (AFA) element based on slot antennas and switchable resonators. This reconfigurable AFA can operate in four modes of operation as a three- or four-pole filter, and yields a 2-bit variable phase delay. As a result, the multimode AFA can be used as the building block of 2-bit adaptive lens arrays. This paper details design, modeling, and miniaturization of the reconfigurable AFA, and demonstrates its performance through preconfigured prototypes. The proposed AFA has a loss of 1.4-1.6 dB measured at 32 GHz in both three- and four-pole filter modes, and exhibits a frequency response that is almost insensitive to the angle of incidence. Several proof-of-concept fixed lens arrays have been also fabricated for output beams scanned to 0deg, 15deg, 30deg, 45deg, and 60deg in the E- and H-plane. The measurement results show that the output beam can be scanned to plusmn60deg in both principle planes, with a worst case sidelobe level of less than -11 dB and a scan loss that hardly exceeds the theoretical limit

A Programmable Lens-Array Antenna With Monolithically Integrated MEMS Switches

IEEE Transactions on Microwave Theory and Techniques, 2009

ABSTRACT This paper describes a reconfigurable millimeter-wave lens-array antenna based on monoli... more ABSTRACT This paper describes a reconfigurable millimeter-wave lens-array antenna based on monolithically integrated microelectromechanical systems (MEMS) switches. This device is constructed as a planar array of 2-bit programmable MEMS antenna-filter-antenna (AFA) unit cells that are used to provide a 1-D programmable ldquoaperture transfer functionrdquo between the input and output wavefronts. The fully integrated device consists of 484 (22 times 22) AFA elements and 2420 switches. Switches, bias lines, antennas, and the rest of the RF structure are fabricated on two quartz wafers (epsiv r = 3.8, tandelta = 0.002) that are subsequently stacked using adhesive bonding to form the tri-layer metal structure of the AFA array. The bonded structure also forms a package for the MEMS switches. This paper investigates the design and fabrication issues and presents the measured data related to yield and frequency response of this lens-array. It also characterizes the performance of this device as a steerable antenna. Measured results show that this lens-array can be used to steer the beam of a low gain horn antenna to plusmn40deg in either the E- or the H-plane. For the fabricated prototype, the yield is estimated to be 50% for the best region of the array, resulting in a relatively high insertion loss and sidelobe level.

Antenna–Filter–Antenna Arrays as a Class of Bandpass Frequency-Selective Surfaces

IEEE Transactions on Microwave Theory and Techniques, 2004

A method is introduced for designing bandpass frequency-selective surfaces (FSSs) using arrays of... more A method is introduced for designing bandpass frequency-selective surfaces (FSSs) using arrays of antenna-filter-antenna (AFA) modules. An AFA module is a filter with radiation ports, which is obtained by integrating two antennas and a nonradiating resonant structure in between. AFA modules are designed based on circuit models and microwave filter design techniques. Three types of these AFA modules are designed using microstrip antennas and coplanar-waveguide resonators, and are used to form FSSs with three-and four-pole shaped bandpass response at 35 GHz. FSS structures are formed by arraying these modules in a periodic grid with an optimal cell size. The proposed concept and the design method are validated using numerical simulation (finite-element method), as well as experimental results.

An affordable millimeter-wave beam-steerable antenna using interleaved planar subarrays

IEEE Transactions on Antennas and Propagation, 2003

Design and fabrication aspects of an affordable planar beam steerable antenna array with a simple... more Design and fabrication aspects of an affordable planar beam steerable antenna array with a simple architecture are considered in this paper. Grouping the elements of a phased array into a number of partially overlapped subarrays and using a single phase shifter for each subarray, generally results in a considerable reduction in array size and manufacturing costs. However, overlapped subarrays require complicated corporate feed networks and array architectures that cannot be easily implemented using planar technologies. In this paper a novel feed network and array architecture for implementing a planar phased array of microstrip antennas is presented that enables the fabrication of low-sidelobe, compact, beam-steerable millimeter-wave arrays and facilitates integration of the RF front-end electronics with the antenna structure. This design uses a combination of series and parallel feeding schemes to achieve the desired array coefficients. The proposed approach is used to design a three-state switched-beam phased array with a scanning width of 10. This phased array which is composed of 80 microstrip elements, achieves a gain of 20 dB, a sidelobe level of 19 dB and a 10-dB bandwidth of 6.3% for all states of the beam. The antenna efficiency is measured at 33-36% in band. It is shown that the proposed feeding scheme is insensitive to the mutual coupling among the elements.

Oscillatory <formula formulatype="inline"><tex Notation="TeX">$Q$</tex> </formula> Factor in Film Bulk Acoustic Resonators With Integrated Microfluidic Channels

IEEE Sensors Journal, 2011

When a film bulk acoustic resonator (FBAR) is coupled to a liquid layer with thickness comparable... more When a film bulk acoustic resonator (FBAR) is coupled to a liquid layer with thickness comparable to the acoustic wavelength, the factor varies in a damped oscillatory pattern with the liquid thickness. This letter reports an analytical modeling and experimental demonstration of this behavior by integrating microfluidic channels to MEMS-based FBARs. It is found that assumes its maxima and minima when the channel thickness is an odd multiple of quarter-wavelength and a multiple of half-wavelength, respectively. The microfluidics integrated FBARs achieve a improvement of over fully immersed FBARs, showing the potential of use as high-resolution sensors involving liquids.

A Fully Passive Wireless Microsystem for Recording of Neuropotentials Using RF Backscattering Methods

Journal of Microelectromechanical Systems, 2011

The ability to safely monitor neuropotentials is essential in establishing methods to study the b... more The ability to safely monitor neuropotentials is essential in establishing methods to study the brain. Current research focuses on the wireless telemetry aspect of implantable sensors in order to make these devices ubiquitous and safe. Chronic implants necessitate superior reliability and durability of the integrated electronics. The power consumption of implanted electronics must also be limited to within several milliwatts to microwatts to minimize heat trauma in the human body. In order to address these severe requirements, we developed an entirely passive and wireless microsystem for recording neuropotentials. An external interrogator supplies a fundamental microwave carrier to the microsystem. The microsystem comprises varactors that perform nonlinear mixing of neuropotential and fundamental carrier signals. The varactors generate third-order mixing products that are wirelessly backscattered to the external interrogator where the original neuropotential signals are recovered. Performance of the neurorecording microsystem was demonstrated by wireless recording of emulated and in vivo neuropotentials. The obtained results were wireless recovery of neuropotentials as low as approximately 500 microvolts peak-to-peak (µV pp) with a bandwidth of 10 Hz to 3 kHz (for emulated signals) and with 128 epoch signal averaging of repetitive signals (for in vivo signals). [2010-0338] Index Terms-Backscattering, biomicroelectromechanical systems, neural recording, neural telemetry, radio frequency (RF) identification (RFID). I. INTRODUCTION T HE AIM OF developing wireless neurointerfaces is to resolve complex challenges underlying basic understanding Manuscript

In-Liquid Quality Factor Improvement for Film Bulk Acoustic Resonators by Integration of Microfluidic Channels

IEEE Electron Device Letters, 2009

We demonstrate a significant improvement in the quality factor (Q) of film bulk acoustic resonato... more We demonstrate a significant improvement in the quality factor (Q) of film bulk acoustic resonators (FBARs) in liquid environments via the integration of microfluidic channels. Our device consists of a longitudinal-mode excited zinc oxide (ZnO) FBAR and parylene-encapsulated microfluidic channels. Considerable enhancement in the Q of the resonant system is obtained by confining the liquid in the microfluidic channels of thickness comparable to the acoustic wavelength. The improved FBAR achieves Q values of up to 120, which represents an improvement of a factor of eight over those of current state-of-the-art devices.

Miniature and tunable filters using mems capacitors

IEEE Transactions on Microwave Theory and Techniques, 2003

Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tun... more Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tunable bandpass filters at 18-22 GHz. Using coplanar waveguide transmission lines on a quartz substrate (= 3 8, tan = 0 0002), a miniature three-pole filter was developed with 8.6% bandwidth based on high-MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate (= 4 6, tan = 0 006). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 0.2% and a midband insertion loss of 3.85-4.15 dB. The IIP 3 of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The IIP 3 increases to 50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150-300 MHz s. Index Terms-Filters, microelectromechanical system (MEMS), MEMS varactors, MEMS devices, miniature filters, tunable filters. I. INTRODUCTION L OW-LOSS bandpass filters are the basic components of transceivers, either as band-select or image-reject units. In the highly integrated systems, however, design of the bandpass filters is generally subject to serious size constraints. In active phased arrays, for example, one filter is required per antenna element, and the filter size cannot exceed a fraction of the free-space wavelength, which is the typical cell size in the array. Also, in multiband receivers, a single filter cannot fulfill the filtering requirements for all operating bands and multiple filters must be used, which proves inconvenient in most communication systems. An ideal solution in such circumstances is a miniature filter that can be tuned for different bands. The existing work in the area of filter miniaturization includes loading of the transmission-line resonators with lumped elements [1],

A Planar Filter-Lens Array For Millimeter- Wave Applications

Planar lens arrays have been addressed by a number of researchers in the existing literature [1][... more Planar lens arrays have been addressed by a number of researchers in the existing literature [1][2] [3][4]. In these works, focusing is obtained by using arrays of receive and transmit antennas which are connected by transmission-line sections of appropriate lengths. Presence of these line sections has adverse effects on the frequency-response and complicates the layout design for large arrays.

An experimental verification of a microwave backscatter tag for recording neural signals

2008 IEEE Antennas and Propagation Society International Symposium, 2008

... Neural Signals Muhammad F. Farooqui (1) , Junseok Chae (1) , Bruce Towe (1) , and Abbas Abbas... more

Oscillating behavior of quality factor of a film bulk acoustic resonator in liquids

TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference, 2009

ABSTRACT When a film bulk acoustic resonator (FBAR) is coupled to a thin liquid layer, the qualit... more ABSTRACT When a film bulk acoustic resonator (FBAR) is coupled to a thin liquid layer, the quality factor (Q) of the resonator varies in a damped oscillatory pattern versus the liquid thickness. This paper reports this behavior with an analytical modeling and experimental demonstration of it. The thin liquid layer with thickness comparable to the acoustic wavelength is realized by integrating a microfluidic channel to the FBAR. Q assumes its maxima (up to 150) and minima (as low as 50) when the channel thickness is an odd multiple of quarter-wavelength and a multiple of half-wavelength, respectively. We also present a bio-molecular detection test for aptamer immobilization and thrombin binding as a proof-of-concept sensing application.

Planar implementation of the partially overlapped subarrays for millimeterwave beam steerable antenna applications

2002 IEEE MTT-S International Microwave Symposium Digest (Cat. No.02CH37278), 2000

ABSTRACT Grouping the elements of a phased array into the partially overlapped subarrays with in-... more ABSTRACT Grouping the elements of a phased array into the partially overlapped subarrays with in-phase excited elements amid using a single phase shifter per subarray has been studied in the past as an approach for reducing the number of phase shifters. Overlapped subarrays require complicated: feeding scenarios, however, that cannot be easily implemented in planar technologies. This paper focuses on a planar implementation which is especially useful for compact millimeterwave arrays and facilitates integration of the antenna and electronics. This design uses a unique combination of series and parallel feeding schemes to form a standing wave array of. microstrip elements. The proposed feeding scheme is theoretically insensitive to the mutual coupling between the elements

A simplified scanning scheme for millimeter-wave active phased arrays

IEEE Antennas and Propagation Society International Symposium. 2001 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.01CH37229), 2000

ABSTRACT A novel and efficient scanning technique using a discrete phasing scheme and proper patt... more ABSTRACT A novel and efficient scanning technique using a discrete phasing scheme and proper pattern synthesis is presented. As in many other beamforming applications, precise control of the array coefficients is crucial for a successful implementation of the array design. A resonant standing wave feeding network is used to ensure proper excitation of the radiating elements. The new scanning technique proves to be very effective in reducing the complexity of the phasing network and hence the fabrication costs. The effectiveness of this simplification procedure becomes more evident when high resolution and a large number of scanning angles are required. In the applications where expensive phase shifters are the most costly and sensitive parts of the antenna system, when the scanning width is relatively small, the new technique can provide a cost-effective alternative

A negative-index annular lens device for feeding 360°-steerable ring arrays

2010 IEEE Antennas and Propagation Society International Symposium, 2010

This paper describes the design of a negative-index annular lens device intended for use as the c... more This paper describes the design of a negative-index annular lens device intended for use as the core element of the beam-forming network in circular ring electronically-steerable arrays (ESA). Circular ring ESA's offer the benefit of full 3600 scan coverage, and hence are ideal for application in mobile and portable communication devices. The proposed lens device can be used as an interface between the front-end electronic and the antenna elements, as depicted in Fig. 1. The lens has an annular geometry. The antenna ports are defined along the outer rim and electronic (or beam) ports lie on the inner rim of the device. The lens is made of inhomogeneous material, where the refractive index varies with radius. Antenna ports can be extended using equal lengths of transmission line to feed an array with a radius greater than that of the lens.

Low-loss bandpass antenna-filter-antenna arrays for applications in quasi-optical systems

2005 European Microwave Conference, 2005

ABSTRACT A new type of 3-pole frequency selective surface (FSS) is proposed as a low-loss bandpas... more ABSTRACT A new type of 3-pole frequency selective surface (FSS) is proposed as a low-loss bandpass filter for quasi-optical applications. This FSS is realized as a uniform array of antenna-filter-antenna (AFA) elements. Each AFA element is a three layer structure consisting two slot antennas and a stripline resonator. A Chebyshev bandpass AFA with 9.5% bandwidth was designed for 32 GHz and fabricated on two layers of Teflon substrates (εr=2.2, tan δ=0.0009). The maximum measured in-band insertion loss for this design is &amp;lt;0.5 dB, which is limited by the in-band ripple of the Chebyshev response.