Showing papers on "Microstrip antenna published in 1989"

Handbook of microstrip antennas

Abstract: Analysis and design of circular microstrip elements microstrip patch antennas circular polarization and bandwidth electromagnetically coupled dipoles multilayer configurations large bandwidth hybrid flat dipoles and arrays numerical analysis of microstrip patch antennas segmentation and desegmentation methods for microstrip antenna design transmission line model of microstrip antennas design and technology of low cost printed antennas analysis and design considerations of printed array antennas circularly polarized array antennas microstrip antenna feeds advances in substrate technology special measurement techniques for printed antennas CAD of microstrip and triplate systems resonant microstrip antenna elements and arrays applications of microstrip antennas monolithic conical conformal microstrip tracking antenna extensions and variations of the microstrip antenna concept.

An impedance-matching technique for increasing the bandwidth of microstrip antennas

Abstract: The nature of the inherent narrow bandwidth of conventional microstrip patch antennas is considered. It is observed that, except for single-feed circularly polarized elements, their bandwidth is limited only by the resonant behavior of the input impedance and not by radiation pattern or gain variations, which usually are negligible over a moderate 10 to 20% bandwidth. Therefore, broadband impedance matching is proposed as a natural to increase the bandwidth. The maximum obtainable bandwidth is calculated using Fano's broadband matching theory. It is found that by using an optimally designed impedance-matching network, the bandwidth can be increased by a factor of at least 3.9, the exact value depending on the degree of matching required. A transmission-line prototype for a proper matching network is developed. The translation of this prototype network into a practical structure (e.g. a microstrip or stripline circuit) is considered. Practical design examples and experimental results which clearly show the validity of the technique are given. >

A study of microstrip array antennas with the feed network

Abstract: The radiation and losses in microstrip antennas with a corporate feed network are studied. A surface current approach is applied in which the electrical currents in the feed lines are modeled as in ideal transmission lines. The free-space radiation and the surface-wave excitation of typical segments in printed feed networks are studied. A four-element array antenna with its printed feed network is analyzed and predicted radiation patterns, directivity, and gain are presented and compared with experimental results. The gain and directivity of large arrays of 16, 64, 256 and 1024 elements are calculated and measurements in the frequency range of 10 to 35 GHz are reported. >

Effect of microstrip antenna substrate thickness and permittivity: comparison of theories with experiment

Abstract: A set of measurements of patch antennas on substrates of varying thickness and permittivity, using three types of feeds, is presented. Resonant frequency and resonant resistance are compared with calculated values from the representative theories. The measurements show that erratic results may be obtained for substrates thicker than about 0.02 lambda /sub 0/, where lambda /sub 0/ is the free-space wavelength at the resonant frequency. These problems may be related to coax-to-microstripline transitions, but their cause is not yet definitely known. The theoretical models that are compared give reasonably good results for resonant frequency, but none give impedance results that are consistently reliable. It thus appears that further work is needed to develop analytical models that can adequately predict the impedance performance of microstrip antennas on thick and/or high dielectric constant substrates. >

Design principles of sequentially fed, wide bandwidth, circularly polarised microstrip antennas

Abstract: The technique of sequentially rotating the feed position of a microstrip patch antenna to improve the circular polarisation bandwidth of an array of such elements is briefly reviewed in the wider context of other known antenna parameter staggering concepts. A first order analysis then shows how the sequential technique significantly improves the axial ratio bandwidth in the relation to the number of patches in the array and the feeder connections. Unwanted effects such as feeder phase errors, multiple reflections in feeders, the presence of higher order modes and mutual coupling are then considered. Computations embracing these effects and measurements illustrate the various properties and topological options available. Finally, the application of the technique is briefly illustrated for a single patch and an array of patches. In conclusion the design principles are summarised and feeder effects are identified as the main limitation when implementing the sequential technique.< >

Analysis of the cylindrical-rectangular patch antenna

Abstract: An analysis is presented of a thin cylindrical-rectangular microstrip patch antenna. After obtaining the electric field under the curved patch and the resonant frequencies using the cavity model, the far-field is found by considering the equivalent magnetic current radiating in the presence of a cylindrical surface. The input impedance and the total Q-factor are then calculated. Numerical and graphical results are presented to illustrate the effect of curvature on the characteristics of the TM/sub 10/ and TM/sub 01/ modes. >

Analysis of microstrip patch antennas using finite difference time domain method

Abstract: The study of microstrip patch antennas is directly treated in the time domain, using a modified finite-difference time-domain (FDTD) method. Assuming an appropriate choice of excitation, the frequency dependence of the relevant parameters can readily be found using the Fourier transform of the transient current. The FDTD method allows a rigorous treatment of one or several dielectric interfaces. Different types of excitation can be taken into consideration (coaxial, microstrip lines, etc.). Plotting the spatial distribution of the current density gives information about the resonance modes. The usual frequency-dependent parameters (input impedance, radiation pattern) are given for several examples. >

Planar microstrip Yagi array antenna

Abstract: The Yagi concept is introduced for the planar microstrip array. With parasitic director and reflector patches located on the same plane of the driven element, the beam peak, by the effect of mutual coupling, can be tilted toward the endfire direction. With this capability, the power divider and phase delay transmission lines in a conventional array are no longer needed, and hence the array efficiency is increased. Both linear and circular polarization microstrip Yagi arrays are described. >

Experiments on injection locking of active antenna elements for active phased arrays and spatial power combiners

Abstract: Two types of active antenna elements have been studied experimentally. One type uses a microstrip antenna with an active device mounted directly on the antenna. The other uses an active device coupled to a microstrip patch antenna through an aperture. Microstrip active antenna elements and two-element arrays have been demonstrated for both types of circuits. Injection locking of the antenna elements has been achieved through space and mutual coupling. The circuit Q factor was calculated based on the locking gain and the locking bandwidth. The power output from two elements has been successfully combined in free space with a combining efficiency of over 90%. For a single active antenna with a Gunn diode mounted directly on the patch, an electronic tuning range exceeding 9% has been achieved by varying the DC bias. The results should have many applications in low-cost active arrays, active transmitters, and spatial power combiners. >

Portable communication apparatus with folded-slot edge-congruent antenna

Abstract: A portable radiotelephone unit is provided with an internal antenna in a space between an internal, electrically conductive enclosure for electrical apparatus of the unit and an external, electrically nonconductive housing of the unit. The antenna is a microstrip, folded-slot, edge-congruent device comprising a stack of alternate, electrically conductive layers and dielectric layers. A high frequency band antenna module and a low frequency band antenna module are included in the antenna, and all layers of that antenna are dimensioned to determine, at least in part, the frequency characteristics of the antenna. Perpendicular and parallel attachments are shown for a feed cable extending, via a hole in the enclosure, between the antenna and radiotelephone unit electrical apparatus within the enclosure.

An Integral Equation Approach to the Analysis of Finite Microstrip Antennas: Volume/Surface Formulation

Abstract: An E-field integral equation for the analysis of finite printed circuit antennas with multiple dielectric regions is developed. In this analysis, the ground plane is considered to be finite. The dielectric substrates may be either lossless or lossy, and they may be inhomogeneous but must be finite. The equivalence principle is used to replace all conducting bodies by equivalent surface electric currents and all dielectrics by equivalent volume polarization currents. The respective boundary conditions on the dielectrics and the conductors are utilized to solve for the electric current on the entire structure. Typical results are presented to illustrate the potential of this method. >

Analysis of infinite arrays of probe-fed rectangular microstrip patches using a rigorous feed model

Abstract: An analysis of infinite arrays of rectangular microstrip patches with each element fed by one or two coaxial probes is presented. The probe self-impedance and the rapidly varying patch current near the feed connection point are rigorously included in the analysis by using an attachment mode derived from the corresponding cavity model solution. Two-probe-fed patches are analysed for both reduced cross-polarisation and circular-polarisation applications, and the effect of probe-to-probe coupling in the unit cell is determined. The theory generates results in excellent agreement with waveguide simulator measurements over a wide range of substrate dielectric constants and thicknesses for both one- and two-probe-fed patches, overcoming the drawbacks of previous solutions that used an idealised probe feed model. Similar solutions can be developed for other types of patch antennas and arrays.

Transmission line analysis of aperture-coupled microstrip antenna

Abstract: The letter presents an original analysis of a slot-coupled microstrip antenna. The transmission line model uses previous expressions of conductance and susceptance due to the fringing fields near the edges of the patch; moreover, a simple interpretation of the different impedance transformations is given. Resullts based on the transmission line model are compared with other theoretical analyses (cavity model, moment method) and measurements.

Analysis of an infinite phased array of aperture coupled microstrip patches

Abstract: An analysis of an infinite array of aperture-coupled microstrip patch antennas is described; this type of element is well suited to integrated phased-array applications, offering several advantages over other array configurations. The solution uses the spectral-domain moment-method approach, and combines features of a previous solution of infinite arrays of probe-fed patches and a reciprocity analysis of single-aperture-coupled microstrip element. The theoretical analysis is described and data are presented for the active input impedance of several arrays. Experimental data from a waveguide simulator confirm the theory. >

Analysis of aperture-coupled microstrip antenna using cavity method

Abstract: The letter presents an original analysis of aperture coupling of a microstrip antenna. The theory is based on the cavity model, and results are compared with the moment method and measurement

Rigorous analysis of a circular patch antenna excited by a microstrip transmission line

Abstract: Boundary conditions are enforced on a portion of the microstrip feed line as well as the patch antenna. The integral equation for the unknown currents on the antenna and feed is solved by applying the Galerkin method of moments in the Fourier transform domain. The validity of the solution is tested by comparison of computed results with experimental data. The theoretical treatment proves to be applicable to the most common feeding arrangements, namely, the direct edge-feed and proximity coupling excitation. In the latter case, two-layer substrates having distinct dielectric constants are studied. The purpose of the study is to deduce, for a given overall substrate thickness, the smallest line-ground plane separation for which a match of the radiator to the feed line is still possible. The advantages of such a configuration are discussed. >

Numerical analysis of microstrip patch antennas

Abstract: In this chapter, microstrip patch antennas are thin and lightweight radiating elements, formed by a substrate, including one or several dielectric layers, backed by a metallic sheet (the ground plane). Thin metallic patches (the radiating elements) are located on the air-substrate interface and, possibly, between the dielectric layers. Microstrip antennas are manufactured by the photolithographic process developed for printed circuits. Their low profile, low weight and mechanical ruggedness make them an ideal choice for aerospace applications. They can be mass-produced, and could thus provide inexpensive receiver antennas for direct reception of microwave signals from satellites (television, mobile communications). Finally, they are ideally suited to be combined in large arrays, the individual patches sharing the same substrate. Thus directive antennas can be obtained in spite of the inherent low directivity of a single patch.

Dual-frequency square patch antenna with rectangular NOTCH

Abstract: A dual-frequency antenna consisting of a square microstrip patch with a rectangular notch is experimentally investigated. The resonant frequencies and return loss are shown as a function of the rectangular notch depth. The radiation patterns show that the polarisation planes at the first and second resonant frequencies are perpendicular to each other.

Gain of circularly polarised arrays composed of linearly polarised elements

Abstract: The gain of circularly polarized (CP) array antennas realized by proper phasing of sequentially rotated linearly polarized (LP) elements is compared to that of arrays using CP elements and demonstrated by calculations for microstrip patch elements. When element spacing is large and array size is small, the advantages of LP elements are offset by the significant reduction in gain due to high cross polarized lobes in the diagonal planes. For large arrays of closely spaced elements, this gain loss reduces to a negligible amount. However, for spacings above a critical value of about 0.7 wavelengths, unacceptably high gain losses will be incurred.

A theoretical and experimental study of mutual coupling in microstrip antenna arrays

Abstract: Each microstrip antenna element in the array is replaced by an equivalent magnetic current source distribution over a grounded dielectric slab derived from the electric field on the walls of the element as given by the cavity model. A dyadic Green's function is developed for a grounded dielectric slab, using the rectangular vector wave functions. The function is used to calculate the magnetic field due to the magnetic current distributions. The formula for mutual impedance based on the reaction concept is used to calculate the mutual coupling in arrays of antenna elements. Some measurements have been conducted for mutual coupling between two rectangular patches in the C-band. Calculated results are in excellent agreement with measurements, including those of other authors. >

The C-patch: a small microstrip element

Abstract: We present a radiating element operating in the UHF and L-bands; its dimensions are smaller than those of conventional square or circular elements. For this type of antenna, good matching is obtained with a coaxial feed, and the omni-directional radiation pattern is achieved using linear polarisation. The bandwidth, however, remains somewhat narrow.

A comparison of models to determine the resonant frequencies of a rectangular microstrip antenna

Abstract: Three variations of the cavity model for determining the resonant frequencies of a rectangular microstrip antenna are compared. The results for each of the variations were experimentally verified by studying a set of patched antennas fed to excite different modes. The method's applicability to electrically thick rectangular microstrip antennas was also investigated. It is also shown that the uncertainties of the patches' dimensions and substrate properties can greatly affect the final result. >

Resonance in cylindrical-rectangular and wraparound microstrip structures

Abstract: A rigorous analysis of the resonance frequency problem of both the cylindrical-rectangular and the wraparound microstrip structure is presented. The problem is formulated in terms of a set of vector integral equations. Using Galerkin's method to solve the integral equations, the complex resonance frequencies are studied with sinusoidal basis functions which incorporate the edge singularity. The complex resonance frequencies are computed using a perturbation approach. Modes suitable for resonator or antenna applications are investigated. The edge singularity of the patch current is shown to have no significant effect on the accuracy of the results. It is shown that the HE/sub 10/ modes of the cylindrical-rectangular and wraparound patches are more appropriate for resonator applications. The HE/sub 01/ and TE/sub 01/ modes of the cylindrical-rectangular and wraparound patches, respectively, are efficient radiating modes. >

Microstrip port design and sidewall absorption for printed Rotman lenses

Abstract: Microstrip Rotman lenses are multiple beam forming devices for antenna arrays. The research described here has investigated factors limiting the performance of microstrip lenses compared to parallel plate lenses. New techniques for sidewall absorption and lens port pointing have been identified and demonstrated.

Folded broadband antenna with a symmetrical pattern

Abstract: A folded broadband antenna provides a symmetrical radiation pattern comparable to corresponding planar antennas (such as a planar spiral). The folded antenna can be integrated into a leading edge radome, eliminating the forward antenna cavity, and thereby, eliminating the internal wall reflections that cause radiation pattern distortion. A broadband antenna (61/62), such as an archimedean spiral, is folded at an apex area (64) that includes a fold-slot (66). The fold-slot enhances flexure, and allows a center-feed balun shielding tube (84) to extend into close proximity to the antenna aperture (61) for increased balun shielding.

Plug-in package for microwave integrated circuit having cover-mounted antenna

Abstract: A TO-style plug-in package for MMICs and associated antenna structure is comprised of a microwave circuit component carrier having a generally cylindrically shaped conductive header upon which one or more MMICs are supported. An aperture through the header contains a conductor pin supported within a glass seal interface, so as to form a hermetically sealed matched impedance transmission line through the package. The conductor pin is connected to a bonding pad of a microwave circuit component on the header. A generally cylindrical conductive cover engages the header and encloses a cavity within which the microwave circuit components are supported. A microstrip antenna is supported on a dielectric layer overlying an outer surface of the conductive cover and is connected to a further conductor pin that extends through a glass-sealed aperture in the cover and forms a matched impedance transmission line from the antenna to the header. The interface between the further conductor pin and the header is configured to provide an effectively blind mated, matched impedance feed-through signal path, so as to facilitate attachment of the conductive cover to the header.

Half-split dielectric resonator placed on metallic plane for antenna applications

Abstract: A practical dielectric resonator antenna structure has been proposed for use at microwave and millimetre-wave frequencies. The radiator can be designed to have a low radiation Q-factor resulting in a relatively wider bandwidth of operation. The scheme used for feeding the antenna shields the feeding arrangement and the associated circuitry from the radiation zone.

On the resonant frequencies of microstrip antennas

Abstract: An appropriately corrected formula for the resonant frequencies of microstrip antenna elements is obtained that is based on the evaluation of the average value of the effective dielectric constant. The author describes the integration averaging technique and presents two examples of its use in more accurately calculating the resonant frequencies of the first five modes of an equilateral triangular microstrip antenna. >