Showing papers on "Microstrip published in 1999"

A uniplanar compact photonic-bandgap (UC-PBG) structure and its applications for microwave circuit

Abstract: This paper presents a novel photonic bandgap (PBG) structure for microwave integrated circuits. This new PBG structure is a two-dimensional square lattice with each element consisting of a metal pad and four connecting branches. Experimental results of a microstrip on a substrate with the PEG ground plane displays a broad stopband, as predicted by finite-difference time-domain simulations. Due to the slow-wave effect generated by this unique structure, the period of the PBG lattice is only 0.1/spl lambda//sub 0/ at the cutoff frequency, resulting in the most compact PEG lattice ever achieved. In the passband, the measured slow-wave factor (/spl beta//k/sub 0/) is 1.2-2.4 times higher and insertion loss is at the same level compared to a conventional 50-/spl Omega/ line. This uniplanar compact PBG (UC-PBG) structure can be built using standard planar fabrication techniques without any modification. Several application examples have also been demonstrated, including a nonleaky conductor-backed coplanar waveguide and a compact spurious-free bandpass filter. This UC-PBG structure should find wide applications for high-performance and compact circuit components in microwave and millimeter-wave integrated circuits.

A 1.9-GHz, 1-W CMOS class-E power amplifier for wireless communications

Abstract: This paper presents a 1-W, class-E power amplifier that is implemented in a 0.35-/spl mu/m CMOS technology and suitable for operations up to 2 GHz. The concept of mode locking is used in the design, in which the amplifier acts as an oscillator whose output is forced to run at the input frequency. A compact off-chip microstrip balun is also proposed for output differential-to-single-ended conversion. At 2-V supply and at 1.98 GHz, the power amplifier achieves 48% power-added efficiency (41% combined with the balun).

Cross-slot-coupled microstrip antenna and dielectric resonator antenna for circular polarization

Abstract: Circular polarization (CP) design of microstrip antennas and dielectric resonator (DR) antennas through a cross slot of unequal slot lengths in the ground plane of a microstrip line is demonstrated. The proposed CP design is achieved by choosing a suitable size of the coupling cross slot, which results in the excitation of two near-degenerate orthogonal modes of near-equal amplitudes and 90/spl deg/ phase difference. This CP design can be applied to both configurations of microstrip antennas and DR antennas and has the advantages of easy fine-tuning and less sensitivity to the manufacturing tolerances, as compared to their respective conventional single-feed CP designs. For the proposed design applied to a low-profile circular disk DR antenna of very high permittivity studied here, a large CP bandwidth, determined from 3-dB axial ratio, as high as 3.91% is also obtained. Details of the proposed antenna designs are described, and experimental results of the CP performance are presented and discussed.

Full band waveguide-to-microstrip probe transitions

Abstract: Design data in the form of dimension tables is presented for probe transitions for microstrip substrates with 4 dielectric constants (2.2, 6.0, 10.1, and 13) in two orientations relative to the waveguide (broadside and longitudinal). These dimensions have been optimized for full waveguide bandwidth with >20 dB return loss using an electromagnetic CAD procedure. The dimensions can be applied to any size waveguide with a 2:1 width/height aspect ratio. Experimental verification for two of the designs applied to a W-band waveguide is presented.

A shaped-beam microstrip patch reflectarray

Abstract: This paper describes a microstrip reflectarray antenna designed to produce a shaped-beam coverage pattern using phase synthesis. The concept is demonstrated with a Ku-band linearly polarized reflectarray designed to provide coverage of the European continent and measured results are compared to those obtained for a previously designed shaped-reflector antenna designed for the same coverage specifications. Results validate the shaped-beam reflectarray concept, although there are disadvantages to the reflectarray such as narrow bandwidth and reduced aperture efficiency that may offset the mechanical and cost advantages of the flat surface of the reflectarray.

Neuromodeling of microwave circuits exploiting space-mapping technology

Abstract: For the first time, we present modeling of microwave circuits using artificial neural networks (ANN's) based on space-mapping (SM) technology, SM-based neuromodels decrease the cost of training, improve generalization ability, and reduce the complexity of the ANN topology with respect to the classical neuromodeling approach. Five creative techniques are proposed to generate SM-based neuromodels. A frequency-sensitive neuromapping is applied to overcome the limitations of empirical models developed under quasi-static conditions, Huber optimization is used to train the ANN's. We contrast SM-based neuromodeling with the classical neuromodeling approach as well as with other state-of-the-art neuromodeling techniques. The SM-based neuromodeling techniques are illustrated by a microstrip bend and a high-temperature superconducting filter.

Hybrid FE/BI modeling of 3-D doubly periodic structures utilizing triangular prismatic elements and an MPIE formulation accelerated by the Ewald transformation

Abstract: We present the formulation of a finite-element/boundary-integral method for the analysis of three-dimensional doubly periodic structures based on arbitrary nonorthogonal lattice configurations. The method starts from a functional description of the field problem where only a single unit cell of the array is considered. This unit cell is meshed with triangular prismatic volume elements and the electric field intensity is discretized with edge-based expansion functions. On the sidewalls of the unit cell, phase boundary conditions are employed to relate the fields on opposing walls of the unit cell. On the top and/or bottom unit cell planar surfaces, the mesh is terminated using a mixed potential integral equation. The required space-domain periodic Green's function is calculated after applying the Ewald (1921) transformation to convert the slowly converging series representation into two rapidly converging series. The method is validated for simple slot and strip frequency-selective surfaces as well as microstrip dipole arrays. More complex geometries investigated are slot-coupled microstrip patches, photonic bandgap materials, and the so-called "artificial puck plate" frequency-selective surface bandpass structure.

Harmonic control by photonic bandgap on microstrip patch antenna

Abstract: In this work, the single microstrip patch antenna having two-dimensional photonic bandgap (PBG) in the ground has been demonstrated experimentally, and the effectiveness of the PBG structure is discussed for the suppression of the resonance at the harmonic frequencies of the antenna. Experimental results indicate that the radiation patterns at the harmonic frequencies can be drastically diminished comparing with the normal microstrip patch antenna without the PBG structure. For instance, the radiation to the forward of the PBG antenna is suppressed at more than 15 dB at the third harmonic frequency.

Design of nonplanar microstrip antennas and transmission lines

Abstract: Introduction and Overview. Resonance Problem of Cylindrical Microstrip Patches. Resonance Problem of Spherical Microstrip Patches. Characteristics of Cylindrical Microstrip Antennas. Characteristics of Spherical and Conical Microstrip Antennas. Coupling between Conformal Mircostrip Antennas. Conformal Microstrip Arrays. Cylindrical Microstrip Lines and Coplanar Waveguides. Appendices. Index.

X-band RF MEMS phase shifters for phased array applications

Abstract: In this work, development of a low-loss radio frequency (RF) microelectromechanical (MEMS) 4-bit X-band monolithic phase shifter is presented. These microstrip circuits are fabricated on 0.021-in-thick high-resistivity silicon and are based on a reflection topology using 3-dB Lange couplers. The average insertion loss of the circuit is 1.4 dB with the return loss >11 dB at 8 GHz. To the best of our knowledge, this is a lowest reported loss for X-band phase shifter and promises to greatly reduce the cost of designing and building phase arrays.

A broad-band microstrip-to-waveguide transition using quasi-Yagi antenna

Abstract: A novel microstrip-to-waveguide transition utilizing a coplanar-strip Yagi-like antenna is presented. The compact and single-layered quasi-Yagi antenna fabricated on high dielectric-constant substrate has end-fire radiation patterns. This monolithic-microwave integrated-circuit (MMIC)-compatible antenna is inserted in the E-plane of the rectangular waveguide to launch the TE/sub 10/ dominant mode. With this new scheme of excitation, compact design and low-cost fabrication is achieved without requiring multilayered substrate or backshort hermetic sealing. This transition, in addition, achieves very broad bandwidth and relatively low insertion loss. The transition's broad-band characteristics are analyzed, and optimization guidelines for individual components of the transition are discussed in detail. A tolerance study proves that the transition is robust in mechanical alignment. The X-band transition with alumina substrate demonstrates 35% bandwidth with return loss better than -12- and -0.3-dB insertion loss at the center frequency. This transition should find wide applications due to its high compatibility with microwave-integrated-circuit/MMIC technology and very low fabrication cost.

Dielectric Loaded Antennas

Abstract: The sections in this article are 1 Dielectric Lens Antennas 2 Effect of Lens on Amplitude Distribution 3 Aberrations 4 Zoned Lenses 5 Reflection from Lens Surface 6 Lenses with n < 1 7 Constrained Lenses 8 Inhomogeneous Lenses 9 Dielectric Loaded Horns 10 Dielectric Loaded Waveguides 11 Microstrip and Dielectric Resonators 12 Insulated Antennas 13 Medical and Biological Antennas

Suppression of unwanted probe radiation in wideband probe-fed microstrip patches

Abstract: The radiation from the probe feed of a microstrip patch can contribute significantly to the cross-polarisation radiation or to pattern distortion, especially if the patch is fabricated on a relatively thick, low-permittivity substrate. By introducing a second probe, which is fed out of phase with the original probe, this unwanted radiation can effectively be suppressed. To demonstrate this technique, two L-band patches were fabricated, one with and one without the extra probe. The dual probe-fed patch produced more symmetrical radiation patterns and had a reduction in the peak cross-polarisation level of nearly 20 dB. The unwanted radiation is effectively suppressed over a bandwidth of >10%.

A microstrip patch antenna using novel photonic band-gap structures

Abstract: Printed antennas exemplified by the microstrip patch antenna offer an attractive solution to compact, conformal and low cost design of modem wireless communications equipment, RF sensors and radar systems. Recent applications have pushed the frequency well into the ram-wave region even in the commercial arena as evidenced by the worldwide race to develop advanced collision warning radar systems for automobiles at the 76 GHz band.[1] Microstrip-based planar antennas fabricated on a substrate with a high dielectric constant (Si, GaAs and InP) are strongly preferred for easy integration with the MMIC RF front-end circuitry. However, it is well known that patch antennas on high dielectric constant substrates are highly inefficient radiators due to surface wave losses and have very narrow frequency bandwidth (approximately one to two percent). This situation becomes extremely severe as applications move to higher frequencies, resulting in patch antennas with reduced gain and efficiency as well as an unacceptably high level of cross polarization and mutual coupling within an array environment. Therefore, much effort has been made recently to realize high efficiency patch antennas on high permittivity substrates, including using the latest micromachining technology.[2,3]

Voltage tunable laminated dielectric materials for microwave applications

Abstract: A tunable dielectric structure includes a first layer of dielectric material, a second layer of dielectric material positioned adjacent to the first layer of dielectric material, with the second layer of dielectric material having a dielectric constant that is less than the dielectric constant of the first layer of dielectric material, and electrodes for applying a controllable voltage across the first dielectric material, thereby controlling a dielectric constant of the first dielectric material, wherein at least one of the electrodes is positioned between the first and second layers of dielectric material. The dielectric materials can be formed in various shapes and assembled in various orientations with respect to each other. The tunable dielectric structure is used in various devices including coaxial cables, cavity antennas, microstrip lines, coplanar lines, and waveguides.

Modeling of a photonic bandgap and its application for the low-pass filter design

Abstract: A new photonic bandgap unit structure for microstrip line is proposed. The equivalent circuit for the proposed photonic bandgap unit structure is derived by means of three dimensional field analysis methods. The equivalent circuit parameters are extracted by using the circuit analysis method. By employing the extracted parameters, the wide-band harmonic rejection low-pass filter is designed. The experimental results show the excellent agreements with theoretical results.

Microstrip directional couplers with ideal performance via single-element compensation

Abstract: Microstrip directional couplers suffer from poor directivity because of inhomogeneous dielectric, i.e., partly dielectric substrate, partly air. It is possible to compensate for this poor performance by introducing a single lumped capacitor or inductor at the edges or center of the coupled region. No attempt at a theoretical design of these couplers has been made in the literature. This paper fills the void by presenting an accurate approach to the design of microstrip directional couplers with ideal match or high directivity of both, using a single capacitive of inductive compensation. The method is valid for tight and loosely coupled structures. The method is validated via design and experimental results.

Aperture-coupled microstrip open-loop resonators and their applications to the design of novel microstrip bandpass filters

Abstract: The rapid growth of wireless and mobile communications has stimulated the development of multilayer filter technology. In this paper, two types of aperture-coupled microstrip open-loop resonators in a multilayer structure are proposed and investigated for the applications to the design of a new class of compact microstrip bandpass filters. The new filter configuration consists of two arrays of microstrip open-loop resonators that ran be coupled through the apertures on the common ground plane. Depending on the arrangement of the apertures, different filtering characteristics can easily be realized. Electromagnetic modeling of the aperture couplings is presented. Three experimental filters of this type with Chebyshev, elliptic function, and linear phase response respectively, are described together with theoretical and experimental results. The filter asymmetric responses associated with frequency-dependent couplings are investigated.

A joint field/circuit model of line-to-ring coupling structures and its application to the design of microstrip dual-mode filters and ring resonator circuits

Abstract: A joint field/circuit model is proposed in this paper to characterize a class of line-to-ring coupling structures for design and optimization of microstrip dual-mode filters and ring resonator circuits. The generic model is derived from field theory and presented in terms of circuit elements by applying a newly developed numerical deembedding technique called "short-open calibration" in a deterministic method-of-moments scheme. It provides a new design strategy for characterizing and optimizing electrical performance of the line-to-ring coupling structures. Such three-port topologies are explicitly formulated by using an equivalent network having circuit elements calculated by the proposed joint field/circuit model. Three microstrip tightly coupling geometries and their related ring resonators are studied with the extracted J-inverter susceptance parameters. Experiments are performed to validate the joint model and also show coupling characteristics of the three types of line-to-ring circuit for the design of ring resonators and dual-mode filters. With this new technique, an optimized microstrip dual-mode filter is successfully designed and the prediction agrees well with our measurements.

1‐D and 2‐D photonic bandgap microstrip structures

Abstract: Recently, 2-D photonic bandgap reflectors in microstrip technology have been proposed. Finite-element 3-D electromagnetic simulation shows negligible values of the fields outside the central row of the periodic pattern. This suggests the use of 1-D patterns to reduce the transversal size of the reflectors. Simulations and measurements have been realized, giving very similar performance for both 1-D and 2-D structures. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 411–412, 1999

Neural computation of resonant frequency of electrically thin and thick rectangular microstrip antennas

Abstract: A method for calculating the resonant frequency of electrically thin and thick rectangular microstrip antennas, based on the backpropagation multilayered-perceptron network, is presented. The method can be used for a wide range of substrate thicknesses and permittivities, and is useful for the computer-aided design (CAD) of microstrip antennas. The calculated resonant-frequency results are in very good agreement with the experimental results reported elsewhere.

A broadband microstrip-to-waveguide transition using quasi-Yagi antenna

Abstract: A novel microstrip-to-waveguide transition utilizing a coplanar strips Yagi-like antenna is presented. The X-band transition demonstrates about 40% bandwidth with return loss better than -12 dB. This transition should find wide applications due to its high compatibility with MIC/MMIC technology at very low fabrication cost.

A high-power fixed-tuned millimeter-wave balanced frequency doubler

Abstract: We report on the design and evaluation of a 40-80-GHz (40/80-GHz) high-power wide-band fixed-tuned balanced doubler. The active device is a single GaAs chip comprising a linear array of six planar Schottky varactors. The varactors and a quartz microstrip circuit are embedded in a split waveguide block. We have achieved a measured 3-dB fixed-tuned bandwidth of 17% and measured flange-to-flange peak efficiency of 48% at an input-power level of 200 mW. The doubler operates at near-peak efficiency (45%) at an input power of 250 mW. We have cooled the block to 14 K and achieved an efficiency of 61% at an input-power level of 175 mW and an efficiency of 48% at an input-power level of 365 mW. Emphasis has been placed on making the design easy to fabricate and scalable to higher frequencies.

Analysis of passive microwave circuits by using a hybrid 2-D and 3-D finite-element mode-matching method

Abstract: A method of analysis of passive microwave circuits based on the segmentation concept is introduced. Complex three-dimensional (3-D) structures are divided into regions delimited by arbitrarily shaped waveguide ports, in which a modal expansion of the field is made. Waveguides can also be filled with inhomogeneous and/or anisotropic media. The regions are analyzed by the mode-matching method (MM) combined with either a two-dimensional (2-D) finite-element method (2-D FEM/MM) or a 3-D FEM (3-D FEM/MM). Open regions are dealt with using the perfectly matched layer. The result of the 3-D FEM analysis is a multimode multiport generalized admittance matrix, from which a generalized scattering matrix is computed. Finally, the method is applied to the analysis of a coax-to-waveguide transition and of a pair of unshielded microstrip lines coupled through an aperture in the common ground plane.

On the coupling of an external electromagnetic field to a printed circuit board trace

Abstract: Compact analytical solutions are developed for the terminal responses of a printed circuit board (PCB) trace exposed to an external electromagnetic field in the frequency and time domain. The analysis based on transmission line theory in a scattered voltage formulation uses a quasi-TEM propagation model for the trace and the exact distribution of the external electric field within the air/dielectric medium for the excitation terms. From the general solutions obtained for arbitrary wave incidence and terminal impedances, several much simpler approximations are derived revealing the principal behavior and indicating the relevant parameters to minimize the coupling. Practical examples with a comparison of the different results are presented.

Circularly polarized aperture-coupled circular microstrip patch antennas for L-band applications

Abstract: Circularly polarized aperture-coupled circular microstrip patch antennas are investigated with the goal of obtaining an 8% impedance and ellipticity bandwidth in the L-band. Three varieties-a single-feed patch with perturbation segments, a single-feed stacked patch with perturbation segments, and a dual-feed patch with a 3-dB branch line coupler as an external polarizer are considered to obtain the required performance. All the three investigated patch configurations meet the impedance bandwidth requirement, but only two varieties: the single-feed stacked patch and the dual-feed patch meet the required ellipticity bandwidth. These antennas feature more than 9-dBi gain. They use low-cost substrates and foam for bandwidth enhancement and, hence, they are attractive for applications where the production cost is of importance.

The theory of surface-wave and space-wave leaky-mode excitation on microstrip lines

Abstract: This paper discusses the excitation and physical validity of both surface-wave and space-wave leaky modes on microstrip lines. This is done by analyzing the discrete modal spectrum excited by a realistic source on or near an infinite microstrip line. A semi-analytical three-dimensional (3-D) Green's function is used for this purpose, which provides the current excited on the conducting strip due to the source. The 3-D Green's function is in the form of a spectral integration (inverse Fourier transform) in the longitudinal wavenumber plane. The poles of the integrand directly determine the excitation amplitudes of the modes on the structure that are launched by the source. The integrand also has different types of branch points, and the location of the poles on the various Riemann sheets is used to determine the physical significance of the leaky modes. Although the theory presented here is illustrated for a microstrip line, the conclusions apply in general to open printed-circuit structures.

Microstrip cross-coupled trisection bandpass filters with asymmetric frequency characteristics

Abstract: A pair of microstrip trisection bandpass filters, consisting of cross-coupled open-loop resonators and exhibiting asymmetric frequency characteristics, are introduced. The utilisation of the microstrip open-loop resonators not only makes the filters compact, but also allows either positive or negative cross coupling to be realised. This results in an attenuation pole of finite frequency on either the high side or the low side of the pass band, so that the frequency response is asymmetric. Two filter designs of this type are described. Theoretical and experimental results are presented.

Resonant frequencies of rectangular microstrip antennas with flush and spaced dielectric superstrates

Abstract: This paper presents a predictive model for the resonant frequencies of rectangular microstrip antennas with flush and spaced superstrates This closed-form model is suitable for CAD and is directly applicable for the integration of microstrip antennas beneath plastic covers or protective dielectric superstrates in portable wireless equipment The model utilizes conformal mapping and the concept of equivalent capacitance to determine the effective permittivity of a covered microstrip structure A comparison between calculated and measured resonant frequencies demonstrates that the model provides less than 1% errors for structures with low relative permittivities (/spl epsi//sub r/<3) and slightly higher errors for structures that contain higher permittivity materials Generally, the model predicts the resonant frequency of a spaced superstrate structure as accurately as possible within the tolerance range of the structure's electrical and physical parameters

High-frequency module

Abstract: Heretofore, a plurality of packages were used in a high frequency module in which a plurality of waveguide terminals were positioned resulting in problems, such as degradation of characteristics in the connection lines between packages, lower ease of assembly when mounting and connecting the connection lines, increased cost, and so forth. To solve these problems, a plurality of cavities having a part or the entire side metallized is formed in a multi-layer dielectric substrate. The multi-layer dielectric substrate is provided with a plurality of waveguide terminals, microstrip line-waveguide converters, RF lines, bias and control signal wiring, and bias and control signal pads. A high frequency circuit is mounted within the cavity and sealed with a seal and cover. This is intended to reduce the number of package, improve performance, improve fabrication, and lower the cost.