Abstract: Radiation and scattering characteristics of microstrip antennas and arrays printed on ferrite substrates with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable circularly polarized radiation from a microstrip antenna having a single feed point, dynamic wide-angle impedance matching for phased arrays of microstrip antennas, and a switchable radar cross section reduction technique for microstrip antennas. Results are obtained from full-wave moment method solutions for single microstrip antennas and infinite arrays of microstrip antennas. A cavity model solution for a circular patch antenna on a biased ferrite substrate is also presented, to aid in understanding the operation of these antennas. >

Abstract: Multilayer microstrip transmission lines are investigated. The conformal mapping method is used to obtain simple analytical relations for the filling factors and the effective permittivity of two fundamental types of three-layer microstrips. Numerical results obtained by the present method are compared with available data from other authors. >

Abstract: A method has been devised to experimentally characterize a packaged GaAs Schottky barrier diode by inserting it into a microstrip test mount. The nonlinear equivalent circuit parameters of the diode are determined by a small-signal test method. A large-signal measurement using the same test mount has also been configured to determine the power conversion efficiency from microwave to DC as well as determining the de-embedded network impedance of the diode. A nonlinear circuit simulation program using a multireflection algorithm is used to verify the experimental results for the 2.45-GHz diode. A Ka-band mixer diode is simulated for a 35-GHz rectenna. Based on the simulation results, a patch-type 35-GHz rectenna is designed and tested in a waveguide simulator. The efficiency is 29% with 120-mW input power. Because the diode could generate undesirable harmonic radiation, a frequency-selective surface is designed to reduce the second harmonic radiation for a 2.45-GHz rectenna. Theoretical results agree fairly well with experiments for all these studies. >

Abstract: The authors present analysis, design and experimental results of a 16 element planar oscillator array for quasi-optical power combining. Each element in the array consists of a single FET oscillator with an input port for injection of the locking signal and an output port which is connected to a patch radiator. The array is synchronized using a 16-way power dividing network which distributes the locking signal to the oscillating elements. The array is constructed using a two-sided microstrip configuration, with the oscillators and feed network on one side of a ground plane, and the patch radiators on the opposite side. An effective radiated power (ERP) of 28.2 W CW with an isotropic conversion gain of 9.9 dB was measured at 6 GHz. For an injected power of 10.3 dBm, a locking range of 453 MHz at a center frequency of 6.015 GHz was obtained; a bandwidth of 7.5%. Because of the simple nature of the individual oscillator elements, this approach is well suited to MMIC implementation. >

Abstract: A microstrip antenna composed of parallel dipole resonators of different lengths fed by a rectangular slot cut in the ground plane of a microstrip line is analyzed using an integral equation technique solved in the spectral domain using the Galerkin method of moments. Multifrequency operation of this antenna is demonstrated using two different configurations. Experimental data are shown to be in good agreement with predicted results. The fundamental parameters influencing the realization of multifrequency operation, as well as impedance matching of the different resonances, are studied. Lastly, the radiation patterns of the antenna at different frequencies and the relative contribution of the dipoles to the radiation are investigated. >

Abstract: A dispersive absorbing boundary condition (DBC) which allows the dispersion characteristics of waves to be used as a criterion for designing absorbing boundary conditions is presented. Its absorbing quality is superior to that of the presently used Mur's first-order boundary condition for microstrip component analysis, and its implementation is much simpler when compared to that of the super boundary condition treatment. Due to the significant performance improvement of the new boundary condition, the memory requirement can be reduced greatly when applying this boundary condition to microstrip component analysis. >

Abstract: An efficient method of analysis of large infinite arrays based on a convolution technique that allows one to obtain the finite array characteristics from the infinite array results is presented. The edge effects are taken into account by convoluting the infinite array results with the proper current amplitude window on the array. The method is based on the use of Poisson's sum formula in the case of finite arrays applied here to microstrip antennas. It is an approximate technique that can be assimilated into a perturbation method. >

Abstract: A spatial domain mixed-potential integral equation method is developed for the analysis of microstrip discontinuities and antennas of arbitrary shape. The algorithm is based on roof-top basis functions on a rectangular and triangular mixed grid and analytical evaluation of the quadruple moment integrals involved. The algorithm has been successfully implemented into an accurate, efficient, and versatile computer program. The numerical results agree with the measured ones very well. >

Abstract: A planar ferro-electric phase shifter which is compatible with commonly-u microwave transmission media to include microstrip, inverted microstrip, and slot line. The ferro-electric material, Bax Sr1-x TiO3, which has a high dielectric-constant, is the phase shifting element. In the microstrip embodiment, the microstrip circuit consists of a ferro-electric element interposed between a conductor line and a ground plane. A DC voltage is applied between the conductor line and the ground plane, thereby controlling the dielectric constant of the ferro-electric material. The dielectric constant of the ferro-electric element in turn controls the speed of the microwave signal, which causes a phase shift. Microwave energy is prevented from entering the DC supply by either a high-impedance, low pass filter, or by an inductive coil. DC voltage is blocked from traveling through the microstrip circuit by a capacitive high-voltage DC bias blocking circuit in the ground plane.

Abstract: A new compact two dimensional FDTD for the dispersion analysis of guided wave structures, a traditionally three dimensional task, is proposed. To prove the validity of this method, the results for a boxed microstrip line on a sapphire substrate are presented and compared with available results. >

Abstract: A method for the computation of radiation patterns of microstrip antennas on substrates of finite dimensions by a combination of the mixed potential integral equation technique (MPIE) for patch antennas and the weak form of the conjugate gradient-fast fourier transform (WCG-FFT) method for the scattering by the finite ground plane is presented. The computation is carried out in three steps. The MPIE formulation is first used for the accurate evaluation of the current distribution on the conducting surface of the patch. Using these currents as primary sources, equivalent polarisation currents in the dielectric slab are then evaluated. These two steps are based on the infinite grounded dielectric slab assumption. Finally the current distribution on the finite ground plane is determined using the WCG-FFT method. Since matrix inversion is not involved in the last step, the method is very convenient for treating small to moderate size ground planes. An alternative approach for the derivation of far field patterns of microstrip antennas on an infinite grounded dielectric slab using the volume equivalence theorem and image theory is also presented. Numerical results of radiation patterns have been verified experimentally. >

Abstract: The crosspolarisation characteristics of coaxially fed microstrip patch antennas are studied using the cavity model. Numerical results showing the variation of crosspolarisation level for different feed positions, substrate thicknesses, substrate permittivities and resonance frequencies are given when the antenna is excited in the TM 11 mode

Abstract: The optimal treatment with hyperthermia of superficially located tumors which involve large surface areas requires applicators which can physically conform to body contours, and locally alter their power deposition patterns to adjust for nonuniform temperature caused by tissue inhomogeneities and blood flow variations. A series of 915-MHz microstrip array applicators satisfying these criteria have been developed and clinically tested. Clinical and engineering design tradeoff's for practical devices are discussed. Measurements taken in tissue equivalent phantoms and a summary of clinical experiences with these microstrip arrays are presented. >

Abstract: A highly sensitive, direct-contact, in situ sensor for nondestructively measuring or monitoring the complex dielectric and conductive properties of solids, liquids, or gasses at microwave frequencies. A metal microstrip dipole resonator (11) is etched on the surface of a dielectric substrate (12) which is bonded to a copper ground plane (14). The dipole resonator is electromagnetically driven by mutual inductive coupling to a short nonresonant feed slot (13) formed in the ground plane (14). The slot (13) is driven by a coaxial feed line (7) or a microstrip feed line (16) extending from a swept microwave frequency source (2) which excites the incident wave (17). Alternatively, the metal resonator is omitted and the length of the slot (15) is increased so that it becomes the resonator. In use, the sensor is placed in close physical contact with the test material (9) having complex dielectric constant e* (=e'-je") or conductivity σ. As the frequency of the microwave source (2) is swept, a sharp dip in the reflected wave (18) occurs at the resonant frequency, provided that the coaxial feed line (7) or microstrip feed line (16) is nearly critically coupled to the sensor input. Measurement of the resonant frequency and input coupling factor determines small changes in e', e" and σ with great resolution. To diminish the electromagnetic coupling between the resonator (11) and the test material (9), and to protect the resonator (11) from damage and wear, a superstrate (26) may be added.

Abstract: Very small, multilayer monolithic microwave integrated circuit (MMIC) couplers are proposed. Novel methods for size reduction, i.e., a quasi-lumped elements approach and a newly developed multilayer coupled-line structure, are also described. A 24-26-GHz-band branch-line coupler and a 20-30-GHz-band broadside coupler were implemented in very small areas of less than 0.4 mm*0.4 mm and 0.2 mm*0.2 mm, respectively. Both couplers used a meanderlike thin-film microstrip line configuration to achieve a drastic size reduction. >

Abstract: Major advances in millimeter-wave antennas have been made in recent years, in particular in two areas. A new class of leaky-wave antennas based on open millimeter waveguides has been proposed and investigated, and substantial progress has been achieved in integrated antennas where active and passive circuits, possibly in monolithic form, are combined with the radiating elements in one compact unit. Interesting developments have taken place also in a third group of millimeter-wave antennas, that of microstrip antennas and printed circuit antennas in general. An attempt is made to summarize these developments. >

Abstract: The design of planar microwave components using multilayer configurations with potentially arbitrary numbers of dielectric layers and metallization planes is described. Analysis and design are based on a combination of a spectral domain immittance matrix approach and standard CAD methods. To verify the design procedure, three examples-microstrip-slot-line-microstrip transition, a stripline band-pass filter, and a microstrip coupler with lines on different sides of a common ground plane-are investigated theoretically and experimentally. >

Abstract: A microwave sampler circuit which operates over the frequency band of 1-20 GHz and has a number of novel features is described. These features include a wideband microstrip-to-slot balun and a wideband active isolator the function of which is to reduce the local oscillator to RF leakage from the input port of the sampler. The signal-to-noise ratio over the input bandwidth is greater than 20 dB at an input power level of -32 dBm. This signal-to-noise ratio was measured in an IF bandwidth of 175 MHz and includes the contribution from the IF amplifier. The sampler, which is made on alumina using MIC techniques, has an integrated impulse generator driven with a sinusoidal local oscillator of only 20 dBm over the frequency band of 250-350 MHz. The IF signal is in the 10-175-MHz band. The RF input VSWR is better than 2:1 up to 20 GHz, and the oscillator to RF breakthrough is better than -58 dBm (-78 dBc) when driven with a local oscillator of 20 dBm. This unusually low leakage was achieved by using the active isolator prior to the sampling circuit. >

Abstract: The present invention provides a microstrip antenna that includes a microstrip element with an integral member which is used to establish an electrical connection between the microstrip element and a transmission line. The use of the integral member to establish this electrical connection yields advantages in performance, reliability, and manufacturing, among others, that make the microstrip antenna particularly suitable for mobile applications. The present invention also provides a method of manufacturing such a microstrip antenna.

Abstract: The determination of an equivalent circuit to approximate the behavior of an interconnect in a computer package is addressed. Equivalent circuits allow the analysis of a complete interconnect path in a circuit simulator where a full-wave analysis tool would require more memory or computer time than in currently available. Two important components of an interconnect in a computer package are uniform transmission lines, such as a microstrip line or a stripline, and discontinuities in the interconnects, such as a via between two transmission lines. A methodology for deriving a frequency-dependent description of coupled transmission lines and an equivalent circuit of a via using time-domain full-wave solutions of Maxwell's equations is presented. >

Abstract: Two generalized multilayer transmission lines are investigated: microstrip lines (MSL) and asymmetrical coplanar waveguide (CPW). The conformal mapping method is used to obtain simple analytical expressions for quasi-TEM effective permittivity of these structures. Accuracy of derived generalized formulas is verified for any special case of multilayer structures. >

Abstract: A space-domain approach based on a mixed-potential integral equation formulation is developed for efficient computation of complex resonant frequencies of laterally open microstrip-pitch resonators of arbitrary shape. The effects of the substrate-which may consist of any number of planar, possibly uniaxially anisotropic, dielectric layers-are rigorously incorporated in the formulation by means of the vector and scalar potential Green's functions. The current distribution on the conducting patch is approximated in terms of vector basis functions defined over triangular elements. Computed resonant frequencies, quality factors, modal currents, and far-field radiation patterns are presented for several microstrip resonators. For patches of simple, regular shapes, the results are in agreement with published data obtained by specialized techniques, which, unlike the method presented here, are not easily extendible to arbitrary shapes. >

Abstract: A dual frequency microstrip rectangular patch antenna resonating at frequencies 520 MHz and 2.5 GHz is presented. This antenna incorporates a matching structure to improve the impedance characteristic at one resonance frequency and uses symmetrically positioned varactor diodes to control resonance at a lower frequency. The use of varactor diodes also provides the benefit of a broad tuning range at the lower resonance frequency. A tuning range of 32%; at 520 MHz was measured.

Abstract: The authors present a periodic second-harmonic spatial power combining oscillator. The power combining is achieved by phase locking the oscillators at the fundamental frequency and combining the second-harmonic power in space through an array of microstrip patch antennas. The effect of moding and multiple device-circuit interaction is investigated. This circuit is planar, and therefore simplifies the design of monolithic circuits, X-band Gunn diodes are used for the purpose of demonstration. >

Abstract: A rigorous full-wave analysis of microstrip via hole grounds is presented using a three-dimensional mode-matching technique in connection with a suitable segmentation of the structure into homogeneous parallelepipedal cells. The adoption of the novel impressed source technique reduces substantially the numerical effort compared to the transverse resonance technique and, in addition to the finite metallization thickness, accounts for possible package interaction. theoretical results are compared with experimental data from various sources, including the authors' experiments, showing excellent agreement. Package effects have been observed experimentally and shown to be fully predicted by the theory. >

Abstract: The authors report on the fabrication and testing of millimeter-wave microstrip/stripline Y-junction circulator operating at K/sub a/ band. By exploiting the properties of high-anisotropy magnetic field, external magnetic field requirements are reduced. The design of microstrip/stripline circulators involves calculations of the radius of the ferrite disks and the port suspension angles in terms of the microstrip dielectric constant and saturation magnetization of the ferrite material. In addition, the operation frequency is determined largely by the uniaxial anisotropy field of the barium-strontium hexagonal ferrite. >

Abstract: An accurate analysis for the microwave and millimeter-wave transmission lines, which include the high T/sub c/ superconductor materials, is presented. This analysis is based on blending a full electromagnetic wave model with London's equations and the two-fluid model. It is capable of fully characterizing the transmission lines, including obtaining the current distributions inside the superconducting material, the electromagnetic fields, the power handling capability, and the quality factor. A simplified model based on the TM-mode solution is also presented. The solution is obtained using the finite-difference scheme. This approach is employed in investigating the superconducting microstrip structure. Results showing current distributions and quality factors are presented. Variations of the line characteristics with the strip width are also presented. The possibility of developing empirical relations for the current carrying capacity as functions of the critical current density and the critical magnetic flux density is also demonstrated. >

Abstract: Results are presented for isolated microstrip antennas and infinite arrays of microstrip antennas printed on chiral substrates, computed from full-wave spectral domain moment method solutions. Data for resonant length, impedance, directivity, efficiency, cross-polarization level, and scan performance are compared to results obtained for a dielectric substrate of the same thickness and permittivity. It is concluded that, from the point of view of antenna characteristics, there does not seem to be any advantage to using chiral antenna substrates, while there are disadvantages in terms of increased cross-polarization levels and losses due to surface wave excitation. >

Abstract: A microwave antenna and receiver assembly is described for use at gigaherz frequencies wherein the antenna is a microstrip antenna and the receiver includes a stripline filter circuit which is integrated in a layered configuration with both the microstrip antenna and the amplifier so as to achieve a very low noise figure, a low SWR and preserve good receiver characteristics, while being easily assembled inside a common radome housing. An inexpensive substrate material formed of alternating layers of polypropylene and woven glass is described for use with the microstrip antenna and other microwave structures.