Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 2009"

Multiresonator-Based Chipless RFID System for Low-Cost Item Tracking

Abstract: A fully passive printable chipless RFID system is presented. The chipless tag uses the amplitude and phase of the spectral signature of a multiresonator circuit and provides 1:1 correspondence of data bits. The tag comprises of a microstrip spiral multiresonator and cross-polarized transmitting and receiving microstrip ultra-wideband disc loaded monopole antennas. The reader antenna is a log periodic dipole antenna with average 5.5-dBi gain. Firstly, a 6-bit chipless tag is designed to encode 000000 and 010101 IDs. Finally, a 35-bit chipless tag based on the same principle is presented. The tag has potentials for low-cost item tagging such as banknotes and secured documents.

A Methodology for Realizing High Efficiency Class-J in a Linear and Broadband PA

Abstract: The design and implementation of a class-J mode RF power amplifier is described. The experimental results indicate the class-J mode's potential in achieving high efficiency across extensive bandwidth, while maintaining predistortable levels of linearity. A commercially available 10 W GaN (gallium nitride) high electron mobility transistor device was used in this investigation, together with a combination of high power waveform measurements, active harmonic load-pull and theoretical analysis of the class-J mode. Targeting a working bandwidth of 1.5-2.5 GHz an initial power amplifier (PA) design was based on basic class-J theory and computer-aided design simulation. This realized a 50% bandwidth with measured drain efficiency of 60%-70%. A second PA design iteration has realized near-rated output power of 39 dBm and improved efficiency beyond the original 2.5 GHz target, hence extending efficient PA operation across a bandwidth of 1.4-2.6 GHz, centered at 2 GHz. This second iteration made extensive use of active harmonic load-pull and waveform measurements, and incorporated a novel design methodology for achieving predistortable linearity. The class-J amplifier has been found to be more realizable than conventional class-AB modes, with a better compromise between power and efficiency tradeoffs over a substantial RF bandwidth.

Characterization of the Propagation Properties of the Half-Mode Substrate Integrated Waveguide

Abstract: The propagation properties of the half-mode substrate integrated waveguide (HMSIW) are studied theoretically and experimentally in this paper. Two equivalent models of the HMSIW are introduced. With the first model, equations are derived to approximate the field distribution inside and outside the HMSIW. Using the second model, an approximate closed-form expression is deduced for calculating the equivalent width of an HMSIW that takes into account the effect of the fringing fields. The obtained design formulas are validated by simulations and experiments. Furthermore, the attenuation characteristics of the HMSIW are studied using the multiline method in the frequency range of 20-60 GHz. A numerical investigation is carried out to distinguish between the contributions of the conductive, dielectric, and radiation losses. As a validation, the measured attenuation constant of a fabricated HMSIW prototype is presented and compared with that of a microstrip (MS) line and a substrate integrated waveguide (SIW). The SIW is designed with the same cutoff frequency and fabricated on the same substrate as the HMSIW. The experimental results show that the HMSIW can be less lossy than the MS line and the SIW at frequencies above 40 GHz.

Substrate Integrated Waveguide Loaded by Complementary Split-Ring Resonators and Its Applications to Miniaturized Waveguide Filters

Abstract: A substrate integrated waveguide with square complementary split-ring resonators (CSRRs) etched on the waveguide surface is investigated in this paper. The proposed structures allow the implementation of a forward-wave passband propagating below the characteristic cutoff frequency of the waveguide. By changing the orientations of the CSRRs, which are incorporated in the waveguide surface and can be interpreted in terms of electric dipoles, varied passband characteristics are observed. A detailed explanation for the generation and variations of the passbands has been illuminated. The application of this waveguide and CSRR combination technique to the design of miniaturized waveguide bandpass filters characterized by transmission zeros is then illustrated. Filter design methodology is examined. These proposed filters exhibit high selectivity and compact size due to the employment of the subwavelength resonators and an evanescent-wave transmission. By slightly altering the configuration of the CSRRs, we find that the propagation of the TE10 mode can be suppressed and filters with improved selectivity and stopband rejection can be obtained. To verify the presented concept, three different types of filters are fabricated based on the standard printed circuit board process. The measured results are in good agreement with the simulation.

Integrated Broadband Microwave and Microfluidic Sensor Dedicated to Bioengineering

Abstract: This paper presents an innovative high-frequency- based biosensor, which combines both microwave detection and microfluidic network for time-efficient and accurate biological analysis. It is composed of a coplanar waveguide with a microfluidic channel placed on top. With the help of an appropriate de-embedding technique and modeling of the measurements, the relative effective permittivity of human umbilical vein endothelial cells has been evaluated successfully. Furthermore, experiments have been performed with the sensor on various cell concentrations in suspension, which validates its use in bioengineering applications such as cell quantification and counting in solution. This sensor requires no direct contact or use of labels on the cells, contrary to other usual types of biosensors (optical, mechanical or dc/low-frequency-detection-based ones).

A 77-GHz FMCW MIMO Radar Based on an SiGe Single-Chip Transceiver

Abstract: This paper describes a novel frequency-modulated continuous-wave radar concept, where methods like nonuniform sparse antenna arrays and multiple-input multiple-output techniques are used to improve the angular resolution of the proposed system. To demonstrate the practical feasibility using standard production techniques, a prototype sensor using a novel four-channel single-chip radar transceiver in combination with differential patch antenna arrays was realized on off-the-shelf RF substrate. Furthermore, to demonstrate its practical applicability, the assembled system was tested in real world measurement scenarios in conjunction with the presented efficient signal processing algorithms.

A Universal UHF RFID Reader Antenna

Abstract: A broadband circularly polarized patch antenna is proposed for universal ultra-high-frequency (UHF) RF identification (RFID) applications. The antenna is composed of two corner-truncated patches and a suspended microstrip line with open-circuited termination. The main patch is fed by four probes which are sequentially connected to the suspended microstrip feed line. The measurement shows that the antenna achieves a return loss of -15 dB, gain of 8.3 dBic, axial ratio (AR) of 3 dB, and 3-dB AR beamwidth of 75deg over the UHF band of 818-964 MHz or 16.4%. Therefore, the proposed antenna is universal for UHF RFID applications worldwide at the UHF band of 840-960 MHz. In addition, a parametric study is conducted to facilitate the design and optimization processes for engineers.

Impedance Characterization of RFID Tag Antennas and Application in Tag Co-Design

Abstract: In this paper, an experimental methodology for the characterization of the impedance of balanced RF identification (RFID) tag antennas is presented, and the application of the proposed method in RFID tag co-design is demonstrated. The balanced tag antenna is considered as a two-port network and the impedance of the antenna is characterized using network parameters. In the measurement, the antenna is connected to the two ports of a vector network analyzer through a test fixture. The influence of the test fixture is deembedded by using a port-extension technique and the antenna impedance can be extracted directly from the measured S -parameters. The proposed method is useful in practical RFID applications for co-designing the RFID tag with the attached platforms for enhancing the tag performance. An example of co-designing an ultra-high-frequency RFID tag with a plastic Sushi plate is demonstrated. The co-designed tag antenna achieves conjugate matching with the application-specific integrated circuit so that the reading range of the RFID tag is greatly enhanced.

A Novel Wideband Common-Mode Suppression Filter for Gigahertz Differential Signals Using Coupled Patterned Ground Structure

Abstract: A wideband and compact filter design for common-mode noise suppression in high-speed differential signals is proposed based on two U-shaped and one H-shaped coupled patterned ground structure. An equivalent model of three coupled LC resonators to predict the common-mode suppression characteristics is also developed with good agreement to the full-wave simulation and measurement result. A test sample is designed and fabricated on a standard printed circuit board (PCB). It is found the common-mode noise can be reduced by the filter over 15 dB from 3.6 to 9.1 GHz and over 75% of amplitude in the time domain. More important, the differential signal integrity, in terms of insertion loss and group delay in the frequency domain and eye diagrams in the time domain, is not degraded within the wide bandwidth. The fractional bandwidth of the stopband can reach 87% and the filter size is about 0.44 lambdag times 0.44 lambdag. The radiation caused by the common-mode current on the attached I/O cables is also efficiently suppressed by 10 dB on average within the designed stopband. To our best knowledge, it is the first low-cost common-mode filter designed for the gigahertz high-speed signals with the largest fractional bandwidth and most compact size on a PCB.

High- $Q$ Fully Reconfigurable Tunable Bandpass Filters

Abstract: In this paper, the authors present a design technique that enables inter-resonator and external coupling control for high-quality-factor (Q) tunable bandpass filters. The design incorporates low-Q varactors as part of the inter-resonator and external coupling mechanisms without degrading the overall high Q of the original filter. Detailed design methodology and equations are presented to illustrate the concepts. A first-time demonstration of these concepts is presented for a widely tunable high-Q evanescent-mode cavity bandpass filter. The cavities are integrated in a low-loss substrate with commercially available piezoelectric actuators and solid-state varactors for frequency and bandwidth tuning. This technique allows for reduced bandwidth variation over large tuning ranges. As one example, a constant 25-MHz absolute-bandwidth filter in the 0.8-1.43-GHz tuning range with loss that is as low as 1.6 dB is presented as an example. The filter third-order intercept point is between 32.8 and 35.9 dBm over this tuning range. To further show the impact of the technique on high- Q filters, a filter Q that is as high as 750 is demonstrated in the range of 3-5.6 GHz, while using low-Q varactors (Q < 30 at 5 GHz for a 0.4-pF capacitance) to achieve more than 50% reduction in bandwidth variation over the tuning range.

Sensitivity and Impedance Measurements of UHF RFID Chips

Abstract: In this paper, we describe the sensitivity and impedance measurement method for UHF RF identification (RFID) chips The measurements are performed using an RFID tester (RFID reader with variable output power and frequency) and a vector network analyzer No special impedance matching is required: chips can be connected to standard 50-Omega connectors allowing the sensitivity and threshold impedance to be measured directly in a fast and efficient way We present experimental data for two UHF Gen2 chips (NXP UCODE G2XM and Impinj Monza 2) in thin-shrink small outline packages The results have been verified using two chip assemblies matched to 50 Omega This method can also be applied to chips in other packages: flip-chip, strap, etc

Design of Varactor-Based Tunable Matching Networks for Dynamic Load Modulation of High Power Amplifiers

Abstract: In this paper, the design of varactor-based tunable matching networks for dynamic load modulation of high power amplifiers (PAs) is presented. Design guidelines to overcome the common breakdown, and tunability problems of the varactors for high power applications are proposed. Based on the guidelines, using commercially available abrupt junction silicon varactors, a tunable matching network is built and measured. The matching network is then used for load modulation of a 1-GHz 7-W class-E LDMOS PA. Static measurements of the load modulated PA show that the power-added efficiency of the PA is improved by an absolute value of 10% at 10-dB backoff. This promising result proves, for the first time, the feasibility of load modulation techniques for high-power applications in the gigahertz frequency range.

Assessment of Heart Rate Variability and Respiratory Sinus Arrhythmia via Doppler Radar

Abstract: An investigation of heart rate variability (HRV) and respiratory sinus arrhythmia (RSA) indices using data obtained from Doppler radar cardiopulmonary remote sensing is presented in this paper. High accuracy in extracting the HRV and RSA indices was achieved using a direct-conversion quadrature radar system with linear demodulation method. This method was validated using data obtained from 12 human subjects in seated and supine positions. For supine position measurements, all standard deviation of normal beat-to-beat interval indices from Doppler radar and electrocardiogram reference differed less than plusmn9 ms of each other, while all the root mean square of differences of successive normal beat-to-beat interval indices differed less than plusmn76 ms. The measurements from subjects in seated and supine positions with normal RSA demonstrated that the results from radar correlated well with both respiratory piezoresistor chest belts. Higher level of HRV and RSA was detected in seated position, as expected.

A Polar Transmitter With CMOS Programmable Hysteretic-Controlled Hybrid Switching Supply Modulator for Multistandard Applications

Abstract: This paper presents the realization of a linear polar transmitter supporting multistandard applications. The harmonic-tuned class-AB biased (class-AB/F) power amplifier (PA) with the novel envelope shaping method linearly amplifies the input signal with high efficiency. The hybrid switching supply modulator with programmable hysteretic comparator enables the multimode operation whatever the envelope signal characteristics such as the peak-to-average power ratio and the bandwidth are. The designed polar transmitter is fabricated with CMOS 0.13-mum technology and InGaP/GaAs 2-mum HBT process for the supply modulator and the PA, respectively. For the IEEE 802.16e m-WiMax signal, it shows a power-added efficiency (PAE), an average output power (Pout), and a gain of 34.3%, 23.9 dBm, and 27.9 dB, respectively. Without any predistortion techniques, it satisfies the overall spectrum emission mask specifications. The relative constellation error and the error vector magnitude for the m-WiMax signal are -30.5 dB and 2.98%, respectively. For a WCDMA signal, it presents a PAE, a Pout, and a gain of 46%, 29 dBm, and 27.8 dB, respectively. For the EDGE signal, it delivers a PAE of 45.3% at a Pout of 27.8 dBm with a gain of 29.4 dB. There is about a 7% improvement of the overall PAE for EDGE through the optimum multimode operation.

A Dual Band Unequal Wilkinson Power Divider Without Reactive Components

Abstract: This paper presents an unequal Wilkinson power divider operating at arbitrary dual band without reactive components (such as inductors and capacitors). To satisfy the unequal characteristic, a novel structure is proposed with two groups of transmission lines and two parallel stubs. Closed-form equations containing all parameters of this structure are derived based on circuit theory and transmission line theory. For verification, two groups of experimental results including open and short stubs are presented. It can be found that all the analytical features of this unequal power divider can be fulfilled at arbitrary dual band simultaneously.

Microwave Analog Real-Time Spectrum Analyzer (RTSA) Based on the Spectral–Spatial Decomposition Property of Leaky-Wave Structures

Abstract: A novel analog real-time spectrum analyzer (RTSA) for the analysis of complex nonstationary signals (such as radar, security and instrumentation, and electromagnetic interference/compatibility signals) is presented, demonstrated, and characterized. This RTSA exploits the space-frequency mapping (spectral-spatial decomposition) property of the composite right/left-handed (CRLH) leaky-wave antenna (LWA) to generate the real-time spectrograms of arbitrary testing signals. Compared to digital RTSAs, it exhibits the advantages of instantaneous acquisition, low computational cost, frequency scalability, and broadband or ultra-wideband operation. The system is demonstrated both theoretically by a commercial full-wave simulator and an efficient Green's function approach and experimentally by a parallel-waveguide prototype including a metal-insulator-metal CRLH LWA, 16 patch antenna probe detectors circularly arranged around the LWA, and a digital oscilloscope performing analog/digital conversion and time-domain acquisition before the postprocessing and displaying of the spectrogram. The system is tested for a large diversity of nonstationary signals and generates, in all cases, spectrograms that are in excellent agreement with theoretical predictions. The fundamental tradeoff between time and frequency resolutions inherent to all RTSA systems is also discussed, and an interchangeable multi-CRLH LWA solution is proposed to handle signals with different time durations.

Single and Four-Element $Ka$ -Band Transmit/Receive Phased-Array Silicon RFICs With 5-bit Amplitude and Phase Control

Abstract: Ka-band SiGe BiCMOS single- and four-element phased arrays capable of both transmit and receive operation with 5-bit phase and amplitude control are presented. The design is based on the All-RF architecture with RF phase shifters and attenuators, and a 4:1 passive power combining/dividing network. The four-element array results in an average gain of ~ 0 dB per channel and a noise figure of 9.0 dB, and is designed to be placed behind III-V T/R modules. The rms phase error is 5.6° (5-bit operation) and < 12.5° (4-bit operation) over a 2 or 5 GHz instantaneous bandwidth, respectively, centered at around 36.5 GHz. In the receive mode, the input P1dB is -16 dBm per channel (IIP3 of - 5.9 dBm), and in the transmit mode, the output P1dB is +4-5 dBm, all at 35-36 GHz. The measured isolation between the channels is better than 30 dB. The array maintained excellent phase characteristics up to 100°C with no change in the rms phase error. Also, ten different four-element phased arrays were tested (40 channels) and result in an rms gain variation of 0.5 dB at 34-39 GHz. The four-element array consumes 171 and 142 mW in the Tx and Rx modes from 1.8 V, and occupies an area of 2.0 × 2.02 mm2. To our knowledge, this is the smallest and lowest power consumption on-chip K ?-band phased-array to-date.

A 90-W Peak Power GaN Outphasing Amplifier With Optimum Input Signal Conditioning

Abstract: A 90-W peak-power 2.14-GHz improved GaN outphasing amplifier with 50.5% average efficiency for wideband code division multiple access (W-CDMA) signals is presented. Independent control of the branch amplifiers by two in-phase/quadrature modulators enables optimum outphasing and input power leveling, yielding significant improvements in gain, efficiency, and linearity. In deep-power backoff operation, the outphasing angle of the branch amplifiers is kept constant below a certain power level. This results in class-B operation for the very low output power levels, yielding less reactive loading of the output stages, and therefore, improved efficiency in power backoff operation compared to the classical outphasing amplifiers. Based on these principles, the optimum design parameters and input signal conditioning are discussed. The resulting theoretical maximum achievable average efficiency for W-CDMA signals is presented. Experimental results support the foregoing theory and show high efficiency over a large bandwidth, while meeting the linearity specifications using low-cost low-complexity memoryless pre-distortion. These properties make this amplifier concept an interesting candidate for future multiband base-station implementations.

Crossover Digital Predistorter for the Compensation of Crosstalk and Nonlinearity in MIMO Transmitters

Abstract: This paper proposes a novel crossover digital predistorter (CO-DPD) model to compensate for crosstalk and nonlinearity in multiple-input multiple-output (MIMO) radio systems. Crosstalk can take place before or after the power amplifiers, designated herein as nonlinear and linear crosstalk, respectively. This paper demonstrates that, contrary to linear crosstalk, nonlinear crosstalk significantly affects the performance of the digital predistortion algorithm; and, it cannot be embedded and compensated for by the conventional channel matrix inversion algorithm at the receiver side of MIMO links. Based on a parametric study of system-level simulations and measurements, it was found that for a -20-dB nonlinear crosstalk level, the use of a memory multibranch polynomial predistorter, along with the channel matrix inversion algorithm, bounds the adjacent channel power ratio (ACPR) for a wideband code division multiple access (WCDMA) signal to -46 dBc and the error vector magnitude (EVM) for a world interoperability for microwave access (WiMAX) signal to -43 dB in MIMO links. The proposed CO-DPD was investigated and analyzed for the MIMO transmitter with N = 2, where N is the number of RF front-ends. Its performance was evaluated through measurements, the experimental results obtained show that, in the presence of -20-dB nonlinear crosstalk, the proposed CO-DPD improve the ACPR of the WCDMA signal by 13 dB to -56.81 dBc from those obtained using a conventional digital predistorter. The same improvement was observed in the EVM measurement of the WiMAX signal, where the EVM decreases from -21.22 dB for the conventional DPD to -49.71 dB for the proposed CO-DPD.

Physics-Based Via and Trace Models for Efficient Link Simulation on Multilayer Structures Up to 40 GHz

Abstract: Analytical models for vias and traces are presented for simulation of multilayer interconnects at the package and printed circuit board levels. Vias are modeled using an analytical formulation for the parallel-plate impedance and capacitive elements, whereas the trace-via transitions are described by modal decomposition. It is shown that the models can be applied to efficiently simulate a wide range of structures. Different scenarios are analyzed including thru-hole and buried vias, power vias, and coupled traces routed into different layers. By virtue of the modal decomposition, the proposed method is general enough to handle structures with mixed reference planes. For the first time, these models have been validated against full-wave methods and measurements up to 40 GHz. An improvement on the computation speed of at least two orders of magnitude has been observed with respect to full-wave simulations.

Substrate Integrated Waveguide Filter With Improved Stopband Performance for Satellite Ground Terminal

Abstract: In this paper, patent pending substrate integrated waveguide (SIW) bandpass filters with moderate fractional bandwidth and improved stopband performance are proposed and demonstrated for a Ka-band satellite ground terminal. Nonphysical cross-coupling provided by higher order modes in the oversized SIW cavities is used to generate the finite transmission zeros far away from the passband for improved stopband performance. Different input/output topologies of the filter are discussed for wide stopband applications. Design considerations including the design approach, filter configuration, and tolerance analysis are addressed. Two fourth-order filters with a passband of 19.2-21.2 GHz are fabricated on a single-layer Rogers RT/Duroid 6002 substrate using linear arrays of metallized via-holes by a standard printed circuit board process. Measured results of the two filters agree very well with simulated results, showing the in-band insertion loss is 0.9 dB or better, and the stopband attenuation in the frequency band of 29.5-30 GHz is better than 50 dB. Measurements over a temperature range of -20degC to +40degC show the passband remains almost unchanged.

A Chipless RFID Sensor System for Cyber Centric Monitoring Applications

Abstract: A chipless RF identifiction (RFID) sensor system platform consisting of passive chipless RFID sensor tags and specialized reader has been developed for cyber centric monitoring applications. The sensor tags are fabricated on a flexible substrate, and the tag identification (ID) generation circuit consists of microstrip transmission lines. Two tag configurations are presented. The first configuration (conf-I) consists of an antenna and an integrated sensor. The second configuration (conf-II) consists of an antenna, ID generation circuit, and a sensor. The specialized reader system, consisting of an analog reader section and an on-board computer system, communicates with the sensor tags using load modulated backscattered communication techniques, at 915-MHz carrier signal. The reader, receiving the ID code generated by a tag, constructs it into a standardized RFID data frame, suitable for cyberspace information exchange. The developed system has been tested for wireless monitoring of ethylene gas. Using a conf-I tag, demodulated voltage change of 3.05 mV is observed at the reader, when the ethylene gas concentration changes from 0 to 100 ppm. The presented conf-II tag prototype allows generation of eight different ID codes and an average of 26.51deg/pF phase change in the backscattered signal, when the load capacitance (sensor) of the tag changes between 1-5 pF.

Signal-to-Noise Ratio in Doppler Radar System for Heart and Respiratory Rate Measurements

Abstract: A CMOS Doppler radar sensor has been developed and used to measure motion due to heart and respiration. The quadrature direct-conversion radar transceiver has been fully integrated in 0.25-mum CMOS, the baseband analog signal conditioning has been developed on a printed circuit board, and digital signal processing has been performed in Matlab. The theoretical signal-to-noise ratio (SNR) is derived based on the radar equation, the direct-conversion receiver's properties, oscillator phase noise, range correlation, and receiver noise. Heart and respiration signatures and rates have been measured at ranges from 0.5 to 2.0 m on 22 human subjects wearing normal T-shirts. The theoretical SNR expression was validated with this study. The heart rates found with the radar sensor were compared with a three-lead electrocardiogram, and they were within 5 beats/min with 95% confidence for 16 of 22 subjects at a 0.5-m range and 11 of 22 subjects at a 1.0-m range. The respiration rates found with the radar sensor were compared with those found using a piezoelectric respiratory effort belt, and the respiration rates were within five respirations per minute for 18 of 22 subjects at a 0.5-m range, 17 of 22 subjects at a 1.0-m range, and 19 of 22 subjects at a 1.5-m range.

Miniaturized Dual-Band Hybrid Couplers With Arbitrary Power Division Ratios

Abstract: Branch-line and rat-race couplers are designed to have dual-band operation with arbitrary power division ratios. An elementary two-port is proposed to imitate the 90deg section at the two designated frequencies with different characteristic impedances. The two-port consists of a stepped-impedance section with open stubs attached to its two ends, and its circuit parameters are determined by the transmission line theory. The use of the stepped-impedance sections also leads to circuit miniaturization. By the standard microstrip technology, investigated also includes the realizable power division ratios and circuit bandwidths in the two bands, the upper limit of the ratio of the two designated frequencies and the miniaturization factor of the proposed circuit. Hybrid couplers operating at 2.45/5.2 GHz with various power division ratios are designed, fabricated and tested. Experiment results are compared with the theory and simulation.

A Programmable Lens-Array Antenna With Monolithically Integrated MEMS Switches

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 (epsivr = 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.

Design of Compact Tri-Band Bandpass Filters Using Assembled Resonators

Abstract: A novel approach for designing tri-band bandpass filters with independently controllable center frequencies and improved stopband rejection characteristic is presented in this paper. The assembled resonator constructed by a stepped impedance resonator and a common half-wavelength resonator is employed to obtain tri-band response. The stepped impedance resonator is designed to operate at the first and third passbands and the other resonator is designed to operate at the second passband. Two kinds of filter configurations with cascaded and pseudointerdigital formats are proposed. Based on lossless lumped-element equivalent circuit, it is found that both filter structures can introduce transmission zeros between passbands. To verify the proposed approach, two filters are designed and fabricated, the measured results exhibit tri-band bandpass responses with high selectivity.

10-Gbit/s Wireless Link Using InP HEMT MMICs for Generating 120-GHz-Band Millimeter-Wave Signal

Abstract: We have developed a 120-GHz-band wireless link whose maximum transmission data rate is 11.1 Gbit/s. The wireless link uses millimeter-wave monolithic integrated circuits (MMICs) for the generation of a 120-GHz-band millimeter-wave wireless signal. The MMICs were fabricated using 0.1-mum-gate InP-HEMTs and coplanar waveguides. The wireless link can handle four kinds of data rate for OC-192 and 10-Gbit Ethernet standards with and without forward error correction (FEC). We succeeded in the error-free transmission of a 10-Gbit/s signal over a distance of 800 m. The introduction of FEC into the 120-GHz-band wireless link decreased the minimum received power for error-free transmission, and improved the reliability of the link.

Miniaturized Bandpass Filters With Double-Folded Substrate Integrated Waveguide Resonators in LTCC

Abstract: This paper proposes miniaturized bandpass filters with double-folded substrate integrated waveguide (SIW) resonators using multilayer low-temperature co-fired ceramic (LTCC) technology. Formed by inserting a metal plate with two orthogonal slots into the cavity, the double-folded SIW resonator is used for the circuit size reduction with its footprint about a quarter of the conventional TE101 mode. With LTCC technology, there is more flexibility to organize the cavities of filters because of the 3-D arrangement. The vertically stacked cavities are coupled by ldquoLrdquo- or ldquoUrdquo-shaped slots, and if arranged horizontally, by an inductive window on the common sidewall or a suspended stripline between the cavities. Through experimental measurements and simulations at both the Ka- V -bands, it has been demonstrated that the proposed filter has compact sizes and good frequency responses. The area of the fully stacked Chebyshev filter has 88% size reduction in comparison with a three-pole planar waveguide filter, while the vertically stacked quasi-elliptic filter has 74% size reduction in comparison with a four-pole planar waveguide filter.

Dielectric Loaded Impedance Matching for Wideband Implanted Antennas

Abstract: In implanted biomedical devices, due to the presence of surrounding dissipative biological tissue, the antenna suffers poor impedance matching. This causes degradation in the performance of a wideband or ultra-wideband (UWB) implanted device. Moreover, the electrical properties of tissue change from organ to organ, and possibly from time to time. In this paper, it is shown that loading of antennas with suitable insulators can deliver broadband matching across a range of dissipative medium properties. An impedance-matched UWB antenna designed to operate inside a lossy medium, which has varying electromagnetic properties within the range expected in biological tissues, is presented. The operating bandwidth of the proposed design is 3.5-4.5 GHz, which is an interference-free subset of the unlicensed UWB band in the US. It is demonstrated that once the dielectric loading is applied, the conventional procedure for antenna design in free space can be followed. The proposed implantable small capsule-shaped slot antenna has been characterized using numerical simulations. Details of a proof-of-concept experiment are presented.

Evaluation of Cardiovascular Stents as Antennas for Implantable Wireless Applications

Abstract: In this study, we explore the use of stents as radiating structures to support transcutaneous wireless telemetry for data transfer of internal measurements from within the circulatory system. The implant location is chosen for the specific application of heart failure detection by monitoring internal pressure measurements of the pulmonary artery. The radiative properties of the single stent are quantified in free space within an anechoic chamber and compared with measurements taken while implanted in a live porcine subject. The in vivo studies of our 2.4-GHz stent-based transmitter, implanted at a depth of 3.5 cm within the chest, showed a 32-35-dB power reduction at a receive distance of 10 cm for both co- and cross-polarizations. The approximate far-field H-plane antenna pattern is quantified at a distance of 50 cm both in free space within an anechoic chamber and while implanted within a porcine chest. These results are used to explore the accuracy of a high-fidelity simulation model developed using Ansoft's High Frequency Structural Simulator and components of their Human Body Model to provide a model that is validated with empirical data. This study provides insight into the effects of tissue on high-frequency electromagnetic transcutaneous transmission and develops a high-fidelity model that can be used for further design and optimization.