Abstract: This paper demonstrates a novel means of achieving cophasal far-field radiation for a circularly polarized microstrip reflectarray with elements having variable rotation angles. Two Ka-band half-meter microstrip reflectarrays have been fabricated and tested. Both are believed to be the electrically largest reflectarrays ever developed using microstrip patches. One, a conventional design, has identical square patches with variable-length microstrip phase-delay lines attached. The other has identical square patches with identical microstrip phase-delay lines but different element rotation angles. Both antennas demonstrated excellent performance with more than 55% aperture efficiencies, but the one with variable rotation angles resulted in better overall performance. A brief mathematical analysis is presented to validate this "rotational element" approach. With this approach, a means of scanning the main beam of the reflectarray over a wide angular region without any RF beamformer by using miniature or micromachined motors is viable.

Abstract: The characteristics of a rectangular microstrip antenna with an L-shaped probe are investigated. A foam layer with a thickness of around 10% of the wavelength is used as the supporting substrate. An impedance bandwidth of 35% and an average gain of 7.5 dBi can be achieved. The radiation pattern is stable across the passband.

Abstract: This paper features some of the advances in dielectric-resonator antenna technology at the Communications Research Centre. Several novel elements are presented that offer significant enhancements to parameters such as impedance bandwidth, circular-polarization bandwidth, gain, or coupling to various feed structures. Several linear and planar arrays are also presented, to illustrate the performance of dielectric-resonator antenna elements in the array environment.

Abstract: Electrically small microstrip patches incorporating shorting posts are thoroughly investigated. These antennas are suitable for mobile communications handsets where limited antenna size is a premium. Techniques to enhance the bandwidth of these antennas are presented and performance trends are established. From these trends, valuable insight to the optimum design, namely broad bandwidth, small size, and ease of manufacturing, is given.

Abstract: Two class AB GaAs field-effect transistor (FET) power amplifiers have been designed and fabricated in the 4.4-4.8 GHz range. In the first case, a dielectric PBG line was incorporated in the design to tune the second harmonic. In the second case, a 50-/spl Omega/ line is used with no harmonic tuning. The PBG structure allows broad-band harmonic tuning and is inexpensive to fabricate. A 5% improvement in power-added efficiency was achieved at the design frequency of 4.5 GHz, in both simulation and measurement.

Abstract: A new class of cross-coupled planar microwave filters using microstrip hairpin resonators is introduced. The realization of bath the canonical and the cascaded quadruplet (CQ) filters is feasible. Coupling characteristics of four basic coupling structures encountered in this class of filters are investigated in the light of full-wave electromagnetic (EM) simulations. A four-pole cross-coupled filter of this type is designed and fabricated. Both the theoretical and experimental performance is presented.

Abstract: The application of photonic bandgap structures (PBG's) as substrates in microstrip circuits has been investigated. The effects of substrate thickness, microstrip transmission line location, and length of the PBG structure were studied using a finite-difference time-domain (FDTD) simulation and experimental measurement. A low-pass filter with a very wide high-frequency rejection bandwidth was constructed from a serial connection of many different PBG structures.

Abstract: Two Dimensions -- Getting Started: Shielded Microstrip Lines. Tools. Microwave Guiding Structures: Characterization. Microwave Guiding Structures: Devices and Circuits. Scattering and Antennas: Hybrid Methods. Scattering and Antennas: Absorbing Boundary Conditions. Three Dimensions - Finite Elements in 3D. Resonant Cavities. Waveguide Devices.

Abstract: This paper presents an in depth characterization of thin film microstrip (TFMS) lines fabricated on Dupont PI-2611 polyimide. Measured attenuation and effective dielectric constant is presented for TFMS lines with thicknesses from 2.45-7.4 /spl mu/m and line widths from 5-34.4 /spl mu/m over the frequency range of 1-110 GHz. The attenuation is separated into conductor and dielectric losses to determine the loss tangent of Dupont PI-2611 polyimide over the microwave frequency range. In addition, the measured characteristics are compared to closed form equations for /spl alpha/ and /spl epsiv//sub eff/ from the literature. Based on the comparisons, recommendations for the best closed form design equations for TFMS are made.

Abstract: The typical single-layer patch printed on a dielectric substrate is a narrow-band element. This well-known fact is mainly due to the limitations imposed by the dielectric substrate. From efficiency and cost considerations, in most of the cases, the substrate cannot be too thick. In order to increase the microstrip element bandwidth, additional resonators in different configurations and combinations can be used: parasitic elements, slots, etc. However, the microstrip antenna element with the widest bandwidth (a variation of the aperture-fed stacked-patch element) is about 40-50%. This antenna, an aperture-fed stacked patch, has a relatively poor front-to-back ratio, due to the fact that it has a slot in the ground plane. In this paper, a new type of patch element is presented. The patch is suspended over the ground plane and supported by a nonconductive pin. It is fed by a three-dimensional (3-D) transition connecting the patch to a perpendicular connector. The typical bandwidth of this element (in terms of VSWR) is 90%. When built on a large ground plane, the front-to-back of this element is better than 25 dB across the band.

Abstract: A simple circular polarisation (CP) design of microstrip antennas using a tuning stub is proposed and studied. It is also demonstrated that, by applying this CP design method to a circular microstrip patch with a cross slot having equal slot lengths, a compact circularly-polarised microstrip antenna can easily be implemented, with much more relaxed manufacturing tolerances as compared to the case of using a cross slot of unequal slot lengths. Details of the antenna designs are described, and experimental results are presented and discussed.

Abstract: This paper discusses various methods of implementing a shared-aperture dual-frequency dual-polarized array antenna for spaced-based synthetic aperture radar (SAR) applications. After evaluating the use of several potential array architecture concepts and radiating elements, a design using interlaced C-band microstrip patches and X-band printed slot elements was chosen as the best choice for the present system requirements. Layout considerations for the two arrays and their associated feed networks are addressed in terms of a practical design. A dual-frequency (C- and X-band), dual-linear polarized SAR array antenna prototype was designed, fabricated, and tested. The principal goal of this effort was to demonstrate the viability of the dual-band dual-polarized array concept, and this has been accomplished. Test results are shown with good correlation between measured and predicted results, validating the design approach used. This work demonstrates that a dual-frequency dual-polarization SAR antenna within a single aperture is a feasible approach to meeting user requirements in future SAR spacecraft.

Abstract: Printed microstrip antennas and arrays are known to have limitations in terms of bandwidth and efficiency, all imposed by the very presence of the dielectric substrate. Microstrip arrays printed on a very thin film and separated from the ground-plane by foam were successfully designed; however, the fabrication difficulties associated with the use of foam considerably increases the fabrication cost. In this paper, a new concept is presented. Rather than using a superstrata geometry, the "printed circuit" is etched out of metal and supported at "strategic points" by (metallic or nonmetallic) posts. The main motivation for this work was to obtain large microstrip arrays, which exhibit a higher efficiency than conventional ones, and can be fabricated using inexpensive large quantity production techniques. However, this technology was also used to develop many new types of microstrip antennas. Microstrip elements and arrays based on this technology were designed and fabricated for the L, S, and C bands.

Abstract: The effects of various physical and electrical parameters of circular microstrip patch antennas on their radiation characteristics are investigated. These parameters include the ground plane size, substrate permittivity, ground plane and substrate thicknesses and the ground plane shape. The investigation is carried out for the first four modes. A numerical method based on the moment methods is utilised which computes surface currents on the conductors and field distributions on the dielectric substrate. To avoid excessive computation, circular patch and ground planes are selected to allow the use of moment method for bodies of revolution. Initially, a circular patch with a finite ground plane is studied. The ground plane is then deformed, above and below the substrate, to increase the gain or shape the radiation patterns. It is shown that the ground plane effects are significant and a wide range of radiation pattern shapes can be generated.

Abstract: Novel compact elliptic-function narrow-band bandpass filters have been designed and fabricated. This new configuration consists of two identical microstrip open-loop resonators with coupled and crossing lines. A theoretical investigation has confirmed that this novel configuration is capable of providing elliptic-function filtering. Furthermore, the feasibility of this filter is verified experimentally. Centered at 2.039 GHz, the fabricated microstrip bandpass filter shows a measured 3-dB bandwidth of 2% and two deep notches in its stopband. In addition, the main circuit of this filter occupies only 2.5 cm/spl times/1.5 cm using a substrate with dielectric constant of 10.5, making it very attractive for applications in the mobile and personal communication systems (PCS's).

Abstract: A waveguide to microstrip transition (124) formed in a multi-layer substrate (208) is disclosed. The waveguide to microstrip transition (124) may be incorporated into a hermetically sealed package including a metal base (202), a multi-layer circuit (208), a metal ring (206), and a metal cover (204). The multi-layer circuit (208) has at least a first dielectric layer (230), a second dielectric layer (222), and a first conductive layer (218) disposed between the bottom side of the first dielectric layer (230) and the top side of the second dielectric layer (222). The multi-layer circuit (208) includes a waveguide (234). An electromagnetically reflective material (236) coats the walls of the waveguide (234) to allow signals to propagate by reflection through the waveguide (234) toward the first dielectric layer (230). Plated through vias (126) are located in at least the first dielectric layer (230). The plated through vias (126) are arranged to form an approximate outline around the land region on the first dielectric layer (230). The plated through vias (126) form a waveguide extension to the waveguide (234) that guides signals through the first dielectric layer. A microstrip (112) is located on the top side of the first dielectric layer (230). The microstrip (112) connects to an E-plane probe (113) located over the waveguide (234) and inside the waveguide extension.

Abstract: This paper presents a double slot-line–microstrip transition employing a 90° cross over them. Using radial stubs at the crossover between the transmission lines, an insertion loss of less than 1.3 dB was measured (0.65 dB per transition) over the 3–15 GHz range. The transition is simulated using a commercial electromagnetic finite-element simulator. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 339–342, 1998.

Abstract: This paper discusses various methods of imple- menting a shared-aperture dual-frequency dual-polarized array antenna for spaced-based synthetic aperture radar (SAR) ap- plications. After evaluating the use of several potential array architecture concepts and radiating elements, a design using interlaced -band microstrip patches and -band printed slot elements was chosen as the best choice for the present sys- tem requirements. Layout considerations for the two arrays and their associated feed networks are addressed in terms of a practical design. A dual-frequency ( - and -band), dual- linear polarized SAR array antenna prototype was designed, fabricated, and tested. The principal goal of this effort was to demonstrate the viability of the dual-band dual-polarized array concept, and this has been accomplished. Test results are shown with good correlation between measured and predicted results, validating the design approach used. This work demonstrates that a dual-frequency dual-polarization SAR antenna within a single aperture is a feasible approach to meeting user requirements in future SAR spacecraft.

Abstract: We report on a gold/strontium titanate (Au-SrTiO/sub 3/) thin-film K-band tunable bandpass filter on a lanthanum aluminate substrate. The two-pole filter has a center frequency of 19 GHz and a 4% bandwidth. Tunability is achieved through the nonlinear temperature dependence and the DC electric field dependence of the relative dielectric constant of SrTiO/sub 3/. A center frequency shift of 0.85 GHz was obtained at 400 V DC bias and 77 K without degrading the insertion loss of the filter.

Abstract: A three-dimensional (3-D) multiresolution analysis procedure similar to the finite-difference time-domain (FDTD) method is derived using a complete set of three-dimensional orthonormal bases of Haar scaling and wavelet functions. The expansion of the electric and the magnetic fields in these basis functions leads to the time iterative difference approximation of Maxwell's equations that is similar to the FDTD method. This technique effectively models realistic microwave passive components by virtue of its multiresolution property; the computational time is reduced approximately by half compared to the FDTD method. The proposed technique is validated by analyzing several 3-D rectangular resonators with inhomogeneous dielectric loading. It is also applied to the analyses of microwave passive devices with open boundaries such as microstrip low-pass filters and spiral inductors to extract their S-parameters and field distributions. The results of the proposed technique agree well with those of the traditional FDTD method.

Abstract: The design of a bow-tie antenna fed by broadside-coupled striplines (BCS) for the 2.4-GHz ISM band is described. The two fins of the bow tie are, respectively, on the two sides of the substrate. The feeding balanced lines adopted are the BCS. A quarter-wave transformer is used to transform the microstrip line input to the BCS feed. An analysis method based on the mixed-potential integral equation method is used to characterize the input characteristics of the bow-tie antenna. The numerical results obtained are in good agreement with the experimental data. Through experiments with bow-tie antennas of various extended angles, the bow-tie antenna with a 90/spl deg/ extended angle exhibits the widest bandwidth in the desired frequency band, which has a bandwidth of 19% for a VSWR<1.5:1.

Abstract: The finite difference time domain (FDTD) method has been used to calculate electromagnetic radiation patterns from 915-MHz dual concentric conductor (DCC) microwave antennas that are constructed from thin and flexible printed circuit board (PCB) materials. Radiated field distributions are calculated in homogeneous lossy muscle tissue loads located under variable thickness coupling bolus layers. This effort extends the results of previous investigations to consider more realistic applicator configurations with smaller 2 cm-square apertures and different coupling bolus materials and thicknesses, as well as various spacings of multiple-element arrays. Results are given for practical applicator designs with microstrip feedlines etched on the backside of the PCB antenna array instead of previously tested bulky coaxial-cable feedline connections to each radiating aperture. The results demonstrate that for an optimum coupling bolus thickness of 2.5-5 mm, the thin, flexible, and lightweight DCC antennas produce effective heating to the periphery of each aperture to a depth of approximately 1 cm, and may be combined into arrays for uniform heating of large area superficial tissue regions with the 50% power deposition contour conforming closely to the outer perimeter of the array.

Abstract: A high-frequency package comprising a dielectric substrate, a high-frequency element that operates in a high-frequency region and is mounted in a cavity formed on said dielectric substrate, and a microstrip line formed on the surface or in an inner portion of said dielectric substrate and electrically connected to said high-frequency element, wherein a signal transmission passage of a waveguide is connected to a linear conducting passage or to a ground layer constituting the microstrip line. In the junction portion of the waveguide, for example, an end of the linear conducting passage is electromagnetically opened, so that the end portion works as a monopole antenna inside the waveguide that is connected. The high-frequency package makes it possible to connect the waveguide without adversely affecting the sealing of the high-frequency element and to transmit high-frequency signals with a low loss.

Abstract: A new method based on artificial neural networks for calculating the resonant frequency of circular microstrip patch antennas is presented. This neural method is simple and is useful for the computer-aided design (CAD) of microstrip antennas. The theoretical resonant frequency results obtained by using the method are in very good agreement with the experimental results reported elsewhere. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 270–277, 1998.

Abstract: This paper presents a new method that accurately determines the characteristic impedance of planar transmission lines printed on lossy dielectrics even when contact-pad capacitance and conductance are large. We demonstrate the method on a coplanar waveguide fabricated on fused silica and a microstrip line fabricated on a highly conductive silicon substrate.

Abstract: A knowledge of the net inductance of the ground plane can aid in the analysis and investigation of printed circuit board emissions. In this paper, we present a method, based on the concept of partial inductance, to determine the net inductance of the ground plane associated with a microstrip line. This method is based on a previously derived expression for the current density on the ground plane. We show calculations for the net, self-partial, and mutual-partial inductance of the ground plane for various trace geometries of practical interest. We also illustrate how the classical transmission line inductance of a microstrip line can be obtained from the concept of partial inductance. Comparisons to different experimental results are also given.

Abstract: By embedding a pair of properly-bent narrow slots close to the non-radiating edges of a rectangular microstrip patch, a novel dual-frequency operation of microstrip antennas using a single probe feed is proposed and experimentally studied. The two operating frequencies have parallel polarisation planes and similar broadside radiation patterns, and the frequency ratio of the two frequencies is controlled by the bent angle of the embedded slots. Details of the obtained dual-frequency performance are presented and discussed.

Abstract: A new amplifier module construction enhances the manufacturer's ability to repetitively construct multiple copies of millimeter microwave amplifiers having performance characteristics that are consistent with one another, particularly in input VSWR ratio characteristic, and which performance characteristic do not significantly change following any necessary rework of the amplifier module, including any MMIC chip replacement. In this module, a waveguide to microstrip transition is formed of a backshort member that is separate from the metal base or cover and that backshort member is held pressed in place against the substrate by force exerted by the module's cover plate through a spring member against the exterior of the backshort member. The spring member is formed by a resilient compressible gasket.

Abstract: The present invention relates to a small microstrip antenna device, mountable inside a hand-held radio communication device, for receiving and transmitting RF signals in one or more frequency bands. The microstrip antenna comprises a ground plane means (101), at least a first feeding means (107) and N radiating elements where N is an integer greater than zero. Said microstrip antenna structure having a first conductive patch (104). Said feeding means being arranged on said first patch for feeding radio frequency signals to said N radiating elements, at least a first of said N radiating elements having a second patch (106). Said second patch being inductively coupled (108) to the first patch.