Showing papers in "IEEE Microwave and Wireless Components Letters in 2001"
TL;DR: In this paper, a planar platform is developed in which the microstrip line and rectangular waveguide are fully integrated on the same substrate, and they are interconnected via a simple taper.
Abstract: Usually transitions from microstrip line to rectangular waveguide are made with three-dimensional complex mounting structures. In this paper, a new planar platform is developed in which the microstrip line and rectangular waveguide are fully integrated on the same substrate, and they are interconnected via a simple taper. Our experiments at 28 GHz show that an effective bandwidth of 12% at 20 dB return loss is obtained with an in-band insertion loss better than 0.3 dB. The new transition allows a complete integration of waveguide components on substrate with MICs and MMICs.
1,631 citations
TL;DR: A computationally efficient and robust image reconstruction algorithm for breast cancer detection using an ultrawideband confocal microwave imaging system and a two-dimensional anatomically realistic MRI-derived FDTD model of the cancerous breast is presented.
Abstract: We present a computationally efficient and robust image reconstruction algorithm for breast cancer detection using an ultrawideband confocal microwave imaging system. To test the efficacy of this approach, we have developed a two-dimensional (2-D) anatomically realistic MRI-derived FDTD model of the cancerous breast. The image reconstruction algorithm is applied to FDTD-computed backscatter signals, resulting in a microwave image that clearly identifies the presence and location of the malignant lesion. These simulations demonstrate the feasibility of detecting and imaging small breast tumors using this novel approach.
479 citations
TL;DR: In this article, the authors presented the design and measured performances of a microstrip 4:1 unequal Wilkinson power divider, which was designed using the conventional Wilkinson topology with the defected ground structure.
Abstract: This letter presents the design and measured performances of a microstrip 4:1 unequal Wilkinson power divider. The divider is designed using the conventional Wilkinson topology with the defected ground structure (DGS). The DGS on the ground plane provides an additional effective inductive component to the microstrip line. This enables the microstrip line to be realized with very high impedance of over 150 /spl Omega/. By employing the DGS to the unequal Wilkinson topology, 4:1 power dividing ratio can be obtained easily without any problem in realization, while it has been impractical to fabricate a 4:1 divider using the conventional microstrip line because of very thin conductor width and extremely low aspect ratio (W/H). As an example, a 4:1 divider has been designed and measured at 1.5 GHz in order to show the validity of the proposed DGS and unequal divider. The measured performances of the 4:1 unequal power divider well agree with the exactly same dividing ratio as that expected.
215 citations
TL;DR: In this article, a physically flexible, practicable THz interconnect with minimal pulse distortion and loss is presented. But the authors show that the attenuation is mainly due to the finite conductivity of copper with some additional loss caused by the beam spread in the unguided dimension.
Abstract: We report the demonstration of a physically flexible, practicable THz interconnect with minimal pulse distortion and loss. The interconnect is a parallel-plate waveguide, with the TEM mode excited, constructed of two thin copper strips. The incoming 0.22 ps THz pulse broadens to 0.39 ps after propagating 250 mm in the waveguide and is also attenuated by a factor of ten. We show that this attenuation is mainly due to the finite conductivity of copper with some additional loss caused by the beam spread in the unguided dimension. The pulse broadening is due to the frequency-dependent loss since the group velocity dispersion is negligible.
192 citations
TL;DR: In this paper, the authors describe a microelectromechanical (MEM) relay technology for high-performance reconfigurable RF circuits, which is a metal contact relay with electrical isolation between signal and drive lines.
Abstract: We describe a microelectromechanical (MEM) relay technology for high-performance reconfigurable RF circuits. This microrelay, fabricated using surface micromachining, is a metal contact relay with electrical isolation between signal and drive lines. This relay provides excellent switching performance over a broad frequency band (insertion loss of 0.1 dB and isolation of 30 dB at 40 GHz), versatility in switch circuit configurations (microstrip and coplanar, shunt and series), and the capability for monolithic integration with high-frequency electronics. In addition, this MEM relay technology has demonstrated yields and lifetimes that are promising for RF circuit implementation.
172 citations
TL;DR: A monolithic true-time delay (TTD) network containing sixteen metal-to-metal contact RF microelectromechanical systems (MEMS) switches has been successfully fabricated and characterized.
Abstract: A monolithic true-time delay (TTD) network containing sixteen metal-to-metal contact RF microelectromechanical systems (MEMS) switches has been successfully fabricated and characterized The TTD network was designed to produce flat delay time over a dc-to-40 GHz bandwidth with full 360-degree phase control at 225-degree intervals at 108 GHz Measurements show a close match to the designed delay times for all sixteen switch states with 22 to 26 dB of insertion loss at 10 GHz The worst group delay ripple in the dc-to-30 GHz range was 3 ps, well within the single bit delay time of 58 ps
152 citations
TL;DR: In this paper, the authors used the finite difference time domain (FDTD) technique and the Pade approximation with Baker's algorithm to calculate the mode frequencies and quality factors of cavities.
Abstract: The finite-difference time domain (FDTD) technique and the Pade approximation with Baker's algorithm are used to calculate the mode frequencies and quality factors of cavities. Comparing with the fast Fourier transformation/Pade method, we find that the Pade approximation and the Baker's algorithm can obtain exact resonant frequencies and quality factors based on a much shorter time record of the FDTD output.
150 citations
TL;DR: In this paper, the performance of a new microelectromechanical structure (MEMS) cantilever microswitch was reported for both dc-and capacitively-contacted microswitches.
Abstract: The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 /spl Omega/, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted switches have an impedance ratio of 141:1 from the open to closed state and in the closed position have a series capacitance of 1.2 pF. The capacitively-contacted switches have been measured up to 40 GHz with S/sub 22/ less than -0.7 dB across the 5-40 GHz band.
139 citations
TL;DR: In this article, a conformal Finite Difference Time Domain (FDTD) technique was used to analyze curved dielectric surfaces. But unlike the existing conformal techniques for handling dielectrics, the present approach utilizes the individual electric field component along the edges of the cell, rather than requiring the calculation of its area or volume.
Abstract: In this paper, we present a simple yet accurate conformal Finite Difference Time Domain (FDTD) technique, which can be used to analyze curved dielectric surfaces. Unlike the existing conformal techniques for handling dielectrics, the present approach utilizes the individual electric field component along the edges of the cell, rather than requiring the calculation of its area or volume, which is partially filled with a dielectric material. The new technique shows good agreement with the results derived by mode matching and analytical methods.
125 citations
TL;DR: In this paper, a direct synthesis technique of coupled symmetric resonator filters with source-load coupling is presented, and the implications of power conservation on the possible solutions to the synthesis problem is examined.
Abstract: A direct synthesis technique of coupled symmetric resonator filters with source-load coupling is presented. An examination of the implications of power conservation on the possible solutions to the synthesis problem is examined. It is shown that at least two different coupling matrices whose entries differ not only in signs but in magnitude, as well, can be extracted. The two matrices have the same coupling and routing scheme. Typical examples of synthesized filters are presented to document the validity of the technique.
121 citations
TL;DR: In this paper, the effects of defected ground structure (DGS) on the output power and efficiency of a class-A power amplifier were evaluated at 4.3/spl sim/4.7 GHz.
Abstract: The authors report the effects of defected ground structure (DGS) on the output power and efficiency of a class-A power amplifier. In order to evaluate the effects of DGS on the efficiency and output power, two class-A GaAs FET amplifiers have been measured at 4.3/spl sim/4.7 GHz. One of them has a 50 /spl Omega/ microstrip line with DGS at the output section, while the other has only 50 /spl Omega/ straight line. It is shown that DGS rejects the second harmonic at the output and yields improved output power and power added efficiency by 1/spl sim/5%.
TL;DR: In this article, a high-performance absorbing boundary condition is developed for the reduction of spurious reflections in photonic crystal (PC) waveguide simulations, where the PC waveguide is terminated with a perfectly matched layer (PML) in which the original PC structure remains as is.
Abstract: A high-performance absorbing boundary condition is newly developed for the reduction of spurious reflections in photonic crystal (PC) waveguide simulations. The PC waveguide is terminated with a perfectly matched layer (PML) in which the original PC structure remains as is. This PC-based PML works well, compared to a conventional PML, which acts as a homogeneous absorbing medium, simulating a semi-infinite free space and to a distributed-Bragg-reflector waveguide, which was recently developed to reduce reflections from PC waveguide ends, improving a wavenumber matching condition for PC waveguide modes.
TL;DR: In this article, a rigorous application of the integral forms of Maxwell's curl equations on the Yee's lattice leads to the desired values in a straightforward fashion, and numerical experiments in a two-dimensional (2-D) cavity are used to verify that the calculated effective permittivities preserve the second-order accuracy of the FDTD scheme.
Abstract: In Yee's finite-difference time-domain (FDTD) scheme, effective permittivities are often used to account for offsets of dielectric interfaces from grid nodes. The specific values of these effective permittivities must be chosen in such a way that the second-order accuracy of the scheme is preserved. It is shown in this work that, contrary to more elaborate techniques proposed recently for the development of these effective permittivities, a rigorous application of the integral forms of Maxwell's curl equations on the Yee's lattice leads to the desired values in a straightforward fashion. Numerical experiments in a two-dimensional (2-D) cavity are used to verify that the calculated effective permittivities preserve the second-order accuracy of the FDTD scheme.
TL;DR: In this article, a general formulation for time-domain finite-element modeling of electromagnetic fields in a general dispersive medium is described, based on the second-order vector wave equation and incorporating the dispersion effect of a medium via a recursively evaluated convolution integral.
Abstract: A general formulation is described for time-domain finite-element modeling of electromagnetic fields in a general dispersive medium. The formulation is based on the second-order vector wave equation and incorporates the dispersion effect of a medium via a recursively evaluated convolution integral. This evaluation is kept to second order in accuracy using linear interpolation within each time step. Numerical examples are given to validate the proposed formulation.
TL;DR: In this article, a new ultra wideband, ultra short-pulse transmitter was developed using microstrip lines, step-recovery and Schottky diodes, MESFET, and monolithic microwave integrated circuit (MMIC) amplifier.
Abstract: A new ultra-wideband, ultra-short-pulse transmitter has been developed using microstrip lines, step-recovery and Schottky diodes, MESFET, and monolithic microwave integrated circuit (MMIC) amplifier. This transmitter employs a novel MESFET impulse-shaping circuit to achieve several unique advantages, including less distortion, easy broadband matching, and increased pulse repetition rate. The transmitter produces 300-ps monocycle pulses with about 2 V peak-to-peak and a pulse repetition rate of 10 MHz. The measured pulses have good symmetry and low ringing level.
TL;DR: In this article, a microwave electric field mapping system based on electrooptic sampling has been developed using micromachined GaAs crystals mounted on gradient index lenses and single-mode optical fibers.
Abstract: A microwave electric-field mapping system based on electrooptic sampling has been developed using micromachined GaAs crystals mounted on gradient index lenses and single-mode optical fibers. The probes are able to detect three orthogonal polarizations of electric fields and, due to the flexibility and size of the optical fiber, can be positioned not only from the extreme near-field to the far-field regions of microwave and millimeter-wave structures, but also inside of enclosures such as waveguides and packages.
TL;DR: In this article, an all-metal series switch with several different pull-down electrode geometries is presented, achieving an upstate capacitance of 5-9 fF and an isolation of -25 to -30 d8 at 10 GHz.
Abstract: This paper presents a novel all-metal series switch with several different pull-down electrode geometries. The switch results in an up-state capacitance of 5-9 fF and an isolation of -25 to -30 d8 at 10 GHz. The fabrication process is completely compatible with the standard capacitive (or dc-contact) shunt switch, A dc-30 GHz series/shunt switch is also presented with an isolation of -60 dB at 5 GHz and -42 dB at 10 GHz. This is the highest isolation switch available to-date. The performance is limited by radiation in the CPW lines and not by the series/shunt switch characteristics. The application areas are in high-isolation switches for basestations and satellite systems.
TL;DR: In this article, an inline capacitive MEMS shunt switch for X/K-band and Ka/V-band applications is presented, which allows for a low or high inductance connection to the ground plane without changing the mechanical characteristics of the MEMS bridge.
Abstract: This paper presents inline capacitive MEMS shunt switches suitable for X/K-band and Ka/V-band applications. The inline switch allows for a low- or high-inductance connection to the ground plane without changing the mechanical characteristics of the MEMS bridge. Excellent isolation and loss are achieved with this design, and the performance is very similar to the standard capacitive MEMS shunt switch. Also, a new metal-to-metal contact MEMS shunt switch is presented. A novel pull-down electrode is used which applies the electrostatic force at the same location as the metal-to-metal contact area. A contact resistance of 0.15-0.35 /spl Omega/ is repeatable, and results in an isolation of -40 dB at 0.1-3 GHz. The measured isolation is still better than -20 dB at 40 GHz. The application areas are in high-isolation/low-loss switches for telecommunication and radar systems.
TL;DR: In this paper, a coplanar stripline (CPS)-to-microstrip line was developed for wideband coplanars with a simple structure for the ease of fabrication with low cost.
Abstract: A wideband coplanar stripline (CPS)-to-microstrip line was developed. The transition has a simple structure for the ease of fabrication with low cost. The measured performance of two back-to-back transitions exhibits an insertion loss of less than 3 dB and a return loss of better than 10 dB over a bandwidth from 1.3 GHz to 13.3 GHz (1:10.2). For narrower bandwidth, an insertion loss of less than 1 dB with a return loss of better than 10 dB was achieved from 1.4 GHz to 7.3 GHz (1:5.2).
TL;DR: In this paper, an experimental investigation of a compact microstrip 180/spl deg/ ring hybrid incorporating a one-dimensional (1-D) slow-wave structure, in the form of perforations on the ring itself, is presented.
Abstract: An experimental investigation of a novel compact microstrip 180/spl deg/ ring hybrid incorporating a one-dimensional (1-D) slow-wave structure, in the form of perforations on the ring itself, is presented. The size of the hybrid is reduced by 23% due to the slow-wave effect, and this size reduction technique has potential applications in MICs and MMICs. The measured insertion loss is comparable to that of a conventional microstrip hybrid.
TL;DR: In this article, a new temporal basis function that has all-order continuous derivative has been constructed using a nonlinear optimization scheme, which provides a much more stable explicit marching-on-in-time (MOT) solution, based on the time-domain integral equation (TDIE) method, than that presently available.
Abstract: A new temporal basis function that has all-order continuous derivative has been constructed using a nonlinear optimization scheme. This new basis function provides a much more stable explicit marching-on-in-time (MOT) solution, based on the time-domain integral equation (TDIE) method, than that presently available. Two examples are presented to illustrate the superior stability of the proposed temporal basis function.
TL;DR: In this article, a dual-path power amplifier using two MEMS switches at the input to guide the RF signal between two paths was proposed. But the performance of the amplifier was limited.
Abstract: RF MEMS switches have been successfully integrated with HEMT MMIC circuits on a GaAs substrate to construct a dual-path power amplifier at X-band. The amplifier uses two MEMS switches at the input to guide the RF signal between two paths. Each path provides single-stage amplification using different size HEMT devices, one with 80-/spl mu/m width and the other with 640-/spl mu/m. Depending on the required output power level, one of the two paths is selected to minimize the dc power consumption. Measurements showed the amplifier producing similar small signal gains of 13.2 and 11.5 dB at 10 GHz for the small and the large devices, respectively. The best PAE was 28.1 percent with 8.5 dBm of output power for the small device, and 15.3 percent with 14.6 dBm for the large device.
TL;DR: In this paper, the authors present the design, fabrication and measurement of single, T-match and /spl pi/-match W-band high-isolation MEMS shunt switches on silicon substrates.
Abstract: This paper presents the design, fabrication and measurement of single, T-match and /spl pi/-match W-band high-isolation MEMS shunt switches on silicon substrates. The single and T-match design result in -20 dB isolation over the 80-110 GHz range with an insertion loss of 0.25/spl plusmn/0.1 dB. The /spl pi/-match design results in a reflection coefficient lower than -20 dB up to 100 GHz, and an isolation of -30 to -40 dB from 75 to 110 GHz (limited by leakage through the substrate). The associated insertion loss Is 0.4/spl plusmn/0.1 dB at 90 GHz. To our knowledge, this is the first demonstration of high-performance MEMS switches at W-band frequencies.
TL;DR: The error analysis for the truncation error in the multipole expansion of vector Green's functions is given and it is shown that the infinite series should be truncated for the addition theorem.
Abstract: One of the most important mathematical formulas in fast multipole algorithms (FMA) is the addition theorem. In the numerical implementation of the addition theorem, the infinite series should be truncated. In this paper, the number of terms needed for the scalar Green's function is derived, and the error analysis for the truncation error in the multipole expansion of the vector Green's functions is given. We have found that the error term in vector Green's functions is proportional to 1/R. If the scalar Green's function is truncated at the L-th term and the relative error is /spl epsiv/, then the relative error in the dyadic Green's function is /spl epsiv//4, if it is truncated at the (L+2)-th term. For the vector Green's function related to MFIE, the relative error is /spl epsiv//2 if it is truncated at the (L+1)-th term.
TL;DR: In this article, a design method for chirped delay lines (CDLs) in microstrip technology is presented, which consist in a continuously varying strip width, so that the coupling location between the quasi-TEM microstrip mode and the same but counter-propagating mode is linearly distributed in frequency.
Abstract: In this paper, we report on a design method for chirped delay lines (CDLs) in microstrip technology. They consist in a continuously varying strip width, so that the coupling location between the quasi-TEM microstrip mode and the same but counter-propagating mode is linearly distributed in frequency. High delay/spl times/bandwidth products, over frequency ranges of several gigahertzs, can be obtained following this procedure. Experimental data confirm the design method. Real-time Fourier analysis of wideband pulses can be performed using these CDLs.
TL;DR: In this paper, a new CPW to waveguide transition is developed based on the concept of tapered slot antenna and E-plane probe coupling, which has the advantages of broad bandwidth, compact size, low fabrication cost and high reliability.
Abstract: A new CPW to waveguide transition is developed based on the concept of tapered slot antenna and E-plane probe coupling. The transition consists of a tapered slotline probe and a slotline to CPW matching section. The current design has the advantages of broad bandwidth, compact size, low fabrication cost, and high reliability. The characteristics of a prototype transition are investigated by numerical simulation on Duroid substrate and WR-90 waveguide. The back-to-back combination is measured to verify the agreement with the simulated results and realization of this design.
TL;DR: In this article, a novel transistor oscillator incorporating a compact microstrip resonant cell (CMRC) as its terminating resonance is proposed, where the fundamental frequency can be positively and negatively fed back at the input port of the oscillator.
Abstract: A novel transistor oscillator incorporating a compact microstrip resonant cell (CMRC) as its terminating resonance is proposed. Adjusting the dimensions of the cell, it is possible that the fundamental frequency can be positively fed back and the second harmonic negatively fed back at the input port of the oscillator. The fundamental output is enhanced with the second harmonic being suppressed. The output power of the proposed CMRC oscillator is 14.7 dBm at 2.5 GHz with 27.1 dB rejection of the second harmonic, outperforming the conventional microstrip termination with a 40% size reduction.
TL;DR: In this article, two reduced-size coplanar-waveguide (CPW) bandpass filters are proposed for broadband and slow-wave applications, and the proposed filters are examined theoretically and experimentally.
Abstract: Two novel reduced-size coplanar-waveguide (CPW) bandpass filters are proposed. Specifically, the bended short-end parallel stubs together with the folded open-end series stubs are utilized to design a broadband filter, and the slow-wave structures are adopted to implement a narrowband filter. In this study, the proposed filters are examined, theoretically and experimentally.
TL;DR: In this article, the first demonstration of a CMOS power amplifier (PA) utilizing fully integrated multilayer low-temperature co-fired ceramic (LTCC) high-Q passives for 1.9 GHz DECT applications is presented.
Abstract: We present the first demonstration of a CMOS power amplifier (PA) utilizing fully integrated multilayer low-temperature co-fired ceramic (LTCC) high-Q passives for 1.9-GHz digital European cordless telecommunications (DECT) applications. The inductor and capacitor library were built in a multilayer LTCC board using a compact topology. An inductor Q-factor as high as 100 with a self-resonant frequency (SRF) as high as 8 GHz was demonstrated. Measured results of the CMOS-LTCC PA show good agreement with the simulated results exhibiting 48% power added efficiency, 26-dBm output power and 17-dB gain at 1.9 GHz with a 3.3-V drain supply voltage. This result is the first significant step toward a compact DECT transceiver module development utilizing fully integrated multilayer LTCC passives and a standard CMOS technology.
TL;DR: In this article, the concept of electromagnetic bandgaps (EBGs) has been utilized to develop a high-quality filter that can be integrated monolithically with other components due to a reduced height, planar design.
Abstract: The concept of electromagnetic bandgaps (EBGs) has been utilized to develop a high-quality filter that can be integrated monolithically with other components due to a reduced height, planar design. Coupling adjacent defect elements in a periodic lattice creates a filter characterized by its ease of fabrication, high-Q performance, high-port isolation, and integrability to planar or 3-D circuit architectures. The filter proof of concept has been demonstrated in a metallo-dielectric lattice. The measured and simulated results of 2-, 3-, and 6-pole filters are presented at 10.7 GHz.