Showing papers in "IEEE Microwave and Wireless Components Letters in 2008"

Macromodeling of Multiport Systems Using a Fast Implementation of the Vector Fitting Method

Abstract: Broadband macromodeling of large multiport systems by vector fitting can be time consuming and resource demanding when all elements of the system matrix share a common set of poles. This letter presents a robust approach which removes the sparsity of the block-structured least-squares equations by a direct application of the QR decomposition. A 60-port printed circuit board example illustrates that considerable savings in terms of computation time and memory requirements are obtained.

An Embedded Common-Mode Suppression Filter for GHz Differential Signals Using Periodic Defected Ground Plane

Abstract: A novel low-cost filter design for common-mode noise suppression in high-speed differential signals is proposed. It is realized by periodically etching the dumbbell-shape defected ground structure (DGS) to perturb the return current of the common- mode noise. A transmission-line model for the proposed structure is also developed with good agreement to the full-wave simulation and measurement result. It is found that over 20 dB suppression of common-mode noise can be achieved over a wide frequency range from 3.3 to 5.7 GHz with 3 cascaded DGS cells, while the differential signals still keep good signal integrity in eye-pattern observation. The common-mode current, which generally results in common-mode EMI, on the attached input/output cable is also proved to be efficiently suppressed (15 dB in average) within the stopband by the proposed filter.

Tri-Band Bandpass Filter With Sharp Passband Skirts Designed Using Tri-Section SIRs

Abstract: This letter presents a second-order tri-band bandpass filter (BPF) designed using tri-section stepped-impedance resonators (TSSIRs). The impedance ratios of the TSSIRs were computed using the formulas expressed as functions of the passband center frequencies, which are located at 1.57, 2.45, and 3.5 GHz. A cross-coupled configuration was arranged to sharpen the passband skirts. The newly designed tri-band BPF was verified by circuit implementation and very good agreement between the simulated and measured results was observed.

A High-Resolution Imaging Radar at 580 GHz

Abstract: We have developed a high-resolution imaging radar at 580 GHz. Coherent illumination in the 576-589 GHz range and phase-sensitive detection are implemented in an all-solid-state design based on Schottky diode sensors and sources. By employing the frequency-modulated continuous wave (FMCW) radar technique, we achieve centimeter-scale range resolution while utilizing fractional bandwidths of less than 3%. Our high operating frequencies also permit centimeter-scale cross-range resolution at several-meter standoff distances without large apertures. Scanning of a single-pixel transceiver enables targets to be rapidly mapped in three dimensions, and here we apply this technology to the detection of concealed objects on persons.

Ultra-Wideband Power Divider With Good In-Band Splitting and Isolation Performances

Abstract: An ultra-wideband (UWB) power divider on microstrip line is proposed, analyzed and designed. This divider is formed by installing a pair of stepped-impedance open-circuited stubs and parallel-coupled lines to two symmetrical output ports. In addition, a single resistor is properly placed between two output ports. After simple transmission line theory analysis, it is demonstrated that 3 dB power splitting from one input to two output ports, good impedance matching at all the three ports and excellent isolation between two output ports are achieved over the specified 3.1-10.6 GHz UWB range. Finally, a prototype divider is fabricated and measured to provide an experimental verification on the predicted attractive features.

A Dual-Band Wilkinson Power Divider

Abstract: A new scheme is proposed for the dual-band operation of the Wilkinson power divider/combiner. The dual band operation is achieved by attaching two central transmission line stubs to the conventional Wilkinson divider. It has simple structure and is suitable for distributed circuit implementation.

Small Ultra-Wideband (UWB) Bandpass Filter With Notched Band

Abstract: A compact ultra-wideband (UWB) bandpass filter (BPF) with notched band has been proposed and implemented in this letter. H-shaped slot is studied and adopted to tighten the coupling of inter-digital capacitor in order to improve the BPF's performance. Three pairs of tapered defected ground structures (DGS) are formed to assign their transmission zeros towards the out of band signal, thereby suppressing the spurious passband. Combining these two structures we obtain a small sized UWB BPF. Meander line slot is developed to reject the undesired wireless local-area network (WLAN) radio signals. An experimental UWB filter with notched band was fabricated with 35% less length as compared to an embedded open-circuited stub. The measured BPF insertion loss is less than 1.0 dB throughout the pass band of 2.8 to 10.8 GHz, the variation of group delay less than 0.20 ns in this band except for the notched band, and a wide stopband bandwidth with 20 dB attenuation up to at least 20.0 GHz.

Implementation of Compact UWB Bandpass Filter With a Notch-Band

Abstract: An ultra-wideband (UWB) bandpass filter on microstrip line with notch-band, compact-size and improved upper-stopband performances is presented and implemented. A modified non-uniform resonator is at first formed by transversely attaching three pairs of impedance-stepped stubs. Its resonance behavior is thoroughly characterized so as to allocate the first three resonant frequencies within 3.1-10.6 GHz band while suppressing spurious harmonics in the upper-band. As this resonator is linked at two sides with two feed lines via interdigital coupled lines with enhanced coupling degree, a preferred UWB passband is realized. Then, one of two arms in the coupled-line sections is largely extended and folded, aiming to create a notch band at the frequency of 5.6 GHz by virtue of out-of-phase transmission cancellation. Two filter prototypes are optimized and fabricated to demonstrate the notch-band-included and upper-stopband-improved UWB bandpass performances.

A Compact Envelope-Memory Polynomial for RF Transmitters Modeling With Application to Baseband and RF-Digital Predistortion

Abstract: In this letter, a compact envelope-memory polynomial based model, suitable for forward and reverse modeling of weakly nonlinear wireless transmitters and power amplifiers (PAs) exhibiting electrical memory effects, is presented. This model is implemented in a complex gain based architecture and takes advantage of the dependency of PA nonlinearity on the magnitude of the input signal. Contrary to conventional memory polynomials, the proposed model can be implemented in baseband, as well as in radio frequency, digital predistorters. A 100-W average power transmitter is used for experimental validation of the forward and reverse models. Both forward and reverse modeling results obtained with the proposed model are comparable to that of the conventional memory polynomial.

A Second-Order Dual X-/Ka-Band Frequency Selective Surface

Abstract: In this letter, a new technique for designing dual-band frequency selective surfaces with arbitrary bands of operation, with second-order band-pass responses at each band of operation, is presented and experimentally verified. The technique is based on utilizing a particular topology of a second-order band-pass microwave filter and synthesizing its constituting elements using periodic structures with inductive, capacitive, or resonant type surface impedances. The result is a low-profile planar structure composed of three metal and two dielectric layers that acts as a spatial version of the dual-band microwave filter.

A Compact Dual-Band Bandpass Filter Using Meandering Stepped Impedance Resonators

Abstract: This letter presents a miniaturized dual-band narrow bandpass filter (BPF) using meandering stepped impedance resonators (SIRs) with a new coupling scheme, which exhibited a size reduction of 50% compared with the traditional direct coupling structure at the same frequency, while the new structure can generate three transmission zeros in the insertion loss response. To validate the design and analysis, two dual-band BPFs centered at 2.4-GHz/5.2-GHz and 2.4-GHz/5.7-GHz for WLAN application were fabricated and measured. It is shown that the measured and simulated performances are in good agreement. The BPFs achieved insertion loss of less than 2 dB and return loss of greater than 16-dB in each band.

Stopband-Expanded Low-Pass Filters Using Microstrip Coupled-Line Hairpin Units

Abstract: In this letter, a class of stopband-expanded low-pass filters (LPFs) is proposed via attenuation poles of microstrip coupled-line hairpin unit. By centrally tap-connecting this coupled-line unit and adjusting its coupling strength, three attenuation poles can be excited above the desired low passband. A coupled-line-oriented closed-form model is then constructed to provide a physical insight into the excitation of these poles and to execute an efficient synthesis design of this LPF. Two prototype filters with single and two units are finally designed with the specified cutoff frequency at 2.5 GHz. Measured results of the fabricated filters evidently demonstrate good LPF performance, sharp roll-off skirt, and a wide upper-stopband of 3.2 to 11.8 GHz with the insertion loss higher than 20.0 dB.

Lifetime Measurements on a High-Reliability RF-MEMS Contact Switch

Abstract: Radio frequency microelectromechanical systems (RF MEMS) cantilever contact switches have been tested for lifetime. The mean cycles-to-failure measured on an ensemble of switches was 430 billion switch cycles. The longest lifetime exhibited without degradation of the switch was 914 billion switch cycles. The devices were switched at 20 kHz with an incident RF frequency of 10 GHz and an incident RF power of 20 dBm. Testing was performed continuously over a period of approximately 18 months. The switches were operated in a cold-switched mode.

Reply to the Comments on “Super-Compact Substrate Integrated Waveguide Cruciform Directional Coupler”

Abstract: For original paper see ibid., vol.17, no.5, p.757-9, (2007). For comment see ibid., p.374, (2008). Our proposed coupler was developed and designed on the basis of an idea similar to the H-plane crossed-waveguide hybrid. In our design, the standard metallic waveguide scheme was replaced by the substrate integrated waveguide (SIW) technology. This technology offers a number of advantages that can overcome several constraints with respect to the standard waveguide technique. A small inventory of coupler structures with the use of standard waveguide techniques was enumerated together with the existing SIW couplers. By properly choosing a dielectric constant and a sheet thickness, a directional coupler can be designed for a given frequency.

Compact Rat-Race Coupler Using Shunt-Stub-Based Artificial Transmission Lines

Abstract: In this letter, a compact rat-race coupler is developed using shunt-stub-based artificial transmission lines (SSB ATLs). A conventional quarter-wavelength microstrip can be equivalent to an SSB ATL realized by two series high-impedance microstrips with the high-impedance branch-type shunt stubs. The circuit configuration of the SSB ATL is beneficial to miniaturize the circuit size using the folding technique. By integrating six SSB ATLs, a compact rat-race coupler can be implemented with a 3.9% circuit size of the conventional one. The measured results of the developed rat-race coupler are in a good agreement with the simulated results by full-wave electromagnetic simulator.

Folded Half Mode Substrate Integrated Waveguide 3 dB Coupler

Abstract: In this letter, novel compact 3 dB double-slot and single-slot couplers are proposed and implemented based on folded half mode substrate integrated waveguide (FHMSIW) The size of the FHMSIW coupler is reduced by nearly 50% and 75% compared with half-mode substrate integrated waveguide coupler and substrate integrated waveguide coupler, respectively Prototype couplers at X-band are fabricated and measured and good performance in bandwidth, insertion loss, and balance are achieved

Dual-Band Capacitive Loaded Frequency Selective Surfaces With Close Band Spacing

Abstract: In this letter, a novel miniaturized dual-band capacitive loaded frequency selective surface (FSS) is presented, in which each periodic cell consist of two neighboring capacitive loaded ring slot resonator with the same dimension. To eliminate the undesired coupling between unit cells, the unit cell is placed in a Faraday cage structure created by arrays of metallic substrate vias. An S-band dual-band FSS with such structures is designed and fabricated, both simulated and measured results show that the proposed FSS provides high transmission with close band spacing at 2.5 and 3.5 GHz, and there is no other resonance frequency up to 15 GHz. Furthermore, the FSS dimension is miniaturized to 0.082 lambda (lambda refer to the resonant wavelength of 2.5 GHz). Also, it is not sensitive to the angle of oblique incidence wave. The design and discussion about dual-band FSS loading with lumped elements is presented for the first time.

Application of Composite Right/Left Handed (CRLH) Transmission Lines based on Complementary Split Ring Resonators (CSRRs) to the Design of Dual-Band Microwave Components

Abstract: In this letter, composite right/left handed transmission lines based on complementary split ring resonators are applied to the design of dual-band microwave components. Specifically, impedance inverters operative at two (arbitrary) different frequencies (one of them within the left-handed band and the other within the right-handed band) are designed and applied to the implementation of a dual-band branch line hybrid coupler. The characterization of this device reveals good performance and dual-band operation. The fabricated device is small, fully planar, and vias are not required.

Broadband Radial Waveguide Spatial Combiner

Abstract: A broadband eight-way spatial combiner using coaxial probes and radial waveguides has been proposed and designed. The simple electromagnetic modeling for the radial waveguide power divider/combiner has been developed using equivalent-circuit method. The measured 10-dB return loss and 1-dB insertion loss bandwidth of this waveguide spatial combiner are all demonstrated to be about 8 GHz.

Varactor-Loaded Complementary Split Ring Resonators (VLCSRR) and Their Application to Tunable Metamaterial Transmission Lines

Abstract: In this letter, the varactor-loaded complementary split ring resonator (VLCSRR) is presented for the first time. This particle is the dual counterpart of the varactor-loaded split ring resonator (VLSRR), which was introduced previously by some of the authors. Thanks to the presence of the varactor diodes, the electrical characteristics of the particle can be electronically tuned. Thus, by loading a microstrip line with VLCSRRs, the structure exhibits a tunable rejection band which is attributed to the negative effective permittivity provided by the particle. It is also shown in this letter that by adding a gap to the structure, the rejection band is switched to a tunable pass band with left handed wave propagation. Due to the topology of the complementary split rings resonators, the insertion and polarization of the diode varactors is not straightforward. These aspects are discussed in the letter. A circuit model for the VLCSRR is proposed. From parameter extraction and comparison between simulation of the circuit model and experiment good agreement is obtained.

Compact Dual Band Bandpass Filter Using Novel E-Type Resonators With Controllable Bandwidths

Abstract: A compact microstrip dual band bandpass filter (BPF) using novel E-type resonators is presented in this letter. The E-type resonator is a short-circuited stub loaded hairpin resonator, two passband frequencies of which can be regulated by adjusting the characteristic impedance and electrical length of the hairpin and the stub. By combining pseudo-interdigital coupling structure, the coupling coefficients of two bands can be adjusted to a desired value in a relatively wide range. In addition, hook feed line is introduced to obtain desired external coupling degrees for two bands. Thus, controllable fractional bandwidths (FBWs) can be achieved. Two two-order 2.45/5.25 GHz dual band BPFs with 3 dB FBW 7%/7% and 5%/5%, respectively, are designed. The measured result agrees well with the simulation.

In-Phase Power-Combined Frequency Triplers at 300 GHz

Abstract: We report on the design, fabrication and characterization of a 300 GHz Schottky-diode frequency tripler made of two mirror-image integrated circuits that are power-combined in-phase in a single waveguide block using compact Y-junctions at the input and output waveguides. Each chip features six anodes on a 5 thick GaAs membrane. The tripler has 5-15% conversion efficiency measured across the 265-330 GHz band when driven with 50-250 mW of input power at room temperature. At 318 GHz it delivers a peak power of 26 mW with 11% conversion efficiency. The power-combined frequency multiplier is compared with a single-chip tripler designed for the same band using the same integrated circuit.

Miniaturization of Microstrip Branch-Line Coupler With Dual Transmission Lines

Abstract: The dual transmission lines are proposed to replace conventional quarter-wavelength transmission lines for a compact microstrip branch-line coupler in this study. The developed coupler can be easily fabricated on the printed circuit board without lumped element; moreover, its size is greatly reduced compared to the conventional branch-line coupler. Furthermore, simulated and measured frequency responses match well to validate the proposed coupler with dual transmission lines.

A Compact Wideband Bandpass Filter Using Transversal Resonator and Asymmetrical Interdigital Coupled Lines

Abstract: A compact wideband microstrip bandpass filter using transversal resonator and asymmetrical interdigital coupled lines is proposed in this letter. A wide passband is first constructed using transversal signal-interference technique, resulting a pair of transmission zeros at each side of the desired passband. By driving this transversal resonator with two asymmetrical interdigital coupled lines at two sides, five extra transmission zeros are generated in the lower/upper stopbands with excellent dc-choked property, thus making up a wide passband with improved out-of-band performance. This wideband microstrip filter is then designed, implemented and experimented. Good insertion/return losses, flat group delay and good out-of-band rejections are achieved as demonstrated in both simulation and experiment.

An Unequal Wilkinson Power Divider for a Frequency and Its First Harmonic

Abstract: This letter presents a Wilkinson power divider operating at a frequency and its first harmonic with unequal power divider ratio. To obtain the unequal property, four groups of 1/6 wavelength transmission lines with different characteristic impedances are needed to match all ports. Theoretically, closed-form equations for the design are derived based on transmission line theory. Experimental results have indicated that all the features of this novel power divider can be fulfilled at f 0 and 2f 0 simultaneously.

Design of a Substrate Integrated Waveguide (SIW) Filter Using a Novel Topology of Coupling

Abstract: We report on a new topology of coupling between substrate integrated circular cavities designed to produce particular filtering functions through combination with the classical iris-based coupling. This coupling is achieved by a grounded coplanar line etched at the top of cavities. This topology was used to realize a Ku-Band third-order filter, whose synthesis, electromagnetic simulation with HFSS, and experimental performances are presented here.

Design of Novel Compact Coupled Microstrip Power Divider With Harmonic Suppression

Abstract: A new microstrip power divider (PD) is proposed which consists of a pair of parallel coupled-lines (PCLs) on a defected ground, and its two outputs are connected by a resistor and a capacitor. The even/odd-mode analysis shows that the defected ground structure (DGS) etched on the ground plane of PCL is equivalent to a strong parallel resonance circuit in the case of even-mode, and a weak inductance in the case of odd-mode. So, this kind of additional reactance effect is used intentionally to design compact coupled microstrip PD with harmonic suppression. Also, the phase-delay through the PD is discussed, which is different from conventional one. A 0.9 GHz PD is developed and experimental results verify it has low insertion loss, good impedance matching and isolation. Furthermore, the third harmonic suppression of this PD is better than -35 dB and the overall area of divider is only 34% of the conventional case.

Electronically Reconfigurable Dual-ModeMicrostrip Open-Loop Resonator Filter

Abstract: A new type of reconfigurable asymmetric frequency response bandpass filter using dual-mode open-loop resonator is investigated. It explores the unique characteristic of the dual-mode open-loop resonator whose two operating modes, i.e., the even- and odd-modes do not couple. Thus, tuning the passband frequency is accomplished by merely changing the two modal frequencies proportionally, which makes the electronic tuning simple. Furthermore, for a single filter of this type, its selectivity can be electronically reconfigured to exhibit a higher selectivity with a finite-frequency transmission zero on either side of the passband. For the demonstration, both simulated and measured results are presented.

A Broadband Quadrature Power Splitter Using Metamaterial Transmission Line

Abstract: A broadband quadrature power splitter (QPS) is developed using the metamaterial transmission line (MM TL). It consists of a Wilkinson power divider and two phase-adjusting TLs, namely a MM TL and a microstrip (MS). The slope of the phase-response curve of the MM TL is synthesized to be the same as that of the MS along with the 90deg phase increment at two design frequencies. Hence, the broadband quadrature phase difference over the desired frequency range can be obtained. In this letter, the QPS is developed at the center frequency of 2 GHz. Over the frequency range of 1.1-3.5 GHz, an amplitude imbalance of less than 0.9 dB and a phase error of less than plusmn5deg have been experimentally demonstrated.

X-Band Substrate Integrated Waveguide Amplifier

Abstract: Design and realization of a compact X-band single-transistor amplifier with substrate integrated waveguide (SIW)-based input and output matching networks is presented. The overall size of the proposed SIW amplifier is only 1.5lambdag at the center frequency. Using a calibration technique, we extract the S-parameters of the fabricated amplifier with reference to its SIW ports. Measurements show that the amplifier features 10 dB of power gain with less than 2 dB of ripple and more than 10 dB of input and output return losses on the SIW ports in the entire frequency band. Due to an appropriate modeling of the constituent blocks of the amplifier, a good agreement between the simulation and measurement results is observed.