Showing papers on "Microstrip antenna published in 1984"

Fundamental superstrate (cover) effects on printed circuit antennas

Abstract: The fundamental effects of superstrate (cover) materials on printed circuits antennas are investigated. Substrate-superstrate resonance conditions are established which maximize antenna gain, radiation resistance, and radiation efficiency. Criteria are determined for material properties and dimensions for which surface waves are eliminated and a radiation efficiency due to substrate-superstrate effects of e_{s} = 100 percent is obtained. Criteria for nearly omnidirectional \bar{H} -plane patterns and nearly omnidirctional \bar{E} -plane patterns are presented. Finally, a general criterion is given for choosing a superstrate to optimize efficiency for the important case of nonmagnetic layers with the antenna at the interface.

Resonant hemispherical dielectric antenna

Abstract: An antenna consisting of a resonant dielectric hemisphere on top of a ground plane is investigated. Calculations of the internal and external fields are made with emphasis on the lowest-order mode that results in efficient radiation in the direction perpendicular to the ground plane. Measured input impedance data are also presented for a practical radiator.

Broad-band microstrip antennas using additional resonators gap-coupled to the radiating edges

Abstract: A method for increasing the bandwidth of microstrip patch antennas by incorporating two additional resonators which are gap-coupled to the radiating edges of a rectangular patch is described. A two-dimensional analysis using Green's function and segmentation method is used for analyzing the proposed antenna configurations. A bandwidth as large as five times a single rectangular patch is obtained in S -band. Changes in the radiation pattern over this wide bandwidth are discussed. Experimental results are in reasonable agreement with the analysis.

Accurate Wide-Range Design Equations for the Frequency-Dependent Characteristic of Parallel Coupled Microstrip Lines

Abstract: In this paper, closed-form expressions are presented which model the frequency-dependent even- and odd-mode characteristics of parallel coupled microstrip lines with hitherto unattained accuracy and range of validity. They include the effective dielectric constants, the characteristic impedances using the power-current formulation, as well as the open-end equivalent lengths for the two fundamental modes on coupled microstrip. The formulas are accurate into the millimeter-wave region. They are based on an extensive set of accurate numerical data which were generated by a rigorous spectral-domain hybrid-mode approach and are believed to represent a substantial improvement compared to the state-of-the-art and with respect to the computer-aided design of coupled microstrip filters, directional couplers, and related components.

Analysis of an infinite array of rectangular microstrip patches with idealized probe feeds

Abstract: A solution is presented for the problem of an infinite array of microstrip patches fed with short current elements. The input reflection coefficient is calculated versus scan angle in an arbitrary scan plane, and the effects of substrate parameters and grid spacings are considered. The scan blindness phenomenom is observed and discussed in terms of a forced surface wave response. Measurements from waveguide simulators confirm the theory for thin substrates.

Circularly polarized conical patterns from circular microstrip antennas

Abstract: A method is presented for generating circularly polarized conical patterns from circular microstrip antennas. These antennas are excited at higher order modes and require different feed arrangements for different mode excitations. It is determined that the peak direction of the conical pattern can be varied over a wide angular range. Modal expansion technique is employed to calculate the radiation patterns of these antennas.

Accurate transmission-line model for the rectangular microstrip antenna

Abstract: An accurate and numerically efficient model for the rectangular microstrip antenna is presented. It concerns a transmission-line model which features the following three major improvements with respect to earlier such models: the mutual radiative coupling (both real and imaginary parts) between the equivalent slots is fully taken into account; the influence of the side slots on the radiation conductance is taken into account implicitly; simple analytic expressions are introduced for all relevant model parameters. By way of illustration, the new model is applied to antennas with a single microstrip feed line. Excellent agreement is shown with available experimental and theoretical results for the input impedance of a rectangular antenna. The improvements with respect to previous transmission-line models are illustrated for a square antenna.

On the modeling of electromagnetically coupled microstrip antennas--The printed strip dipole

Abstract: A generalized solution for a class of printed circuit antennas excited by a strip transmission line is presented. The strip transmission line may be embedded inside or printed on the substrate. As an example, microstrip dipoles electromagnetically coupled (Parasitically excited) to embedded strip transmission line have been analyzed accurately, and design graphs are provided for a specific substrate material. These graphs permit the establishment of a design procedure which yields the microstrip dipole length, overlap, offset, and substrate thickness with the goal of a desired input match for a given substrate material. The method accounts for conductor thickness and for arbitrary substrate parameter. Comparison with experiment shows excellent agreement.

Microstrip antennas for dual-frequency operation

Abstract: Single element microstrip antenna for dual-frequency operation have been investigated. By placing shorting pins at appropriate locations in the patch, the ratio of two-band frequencies can be varied from 3 to 1.8. In many applications a smaller ratio is desired, and this can be achieved by introducing slots in the patch. In so doing, the ratio can be reduced to less than 1.3. For this type of antenna, a hybrid multiport theory is developed and theoretical results are found to be in excellent agreement with the measured.

Circular-disk microstrip antenna with an air gap

Abstract: The circular-disk microstrip antenna with an air gap between the substrate and the ground plane is analyzed using the cavity-model theory. A simple formula for the resonant frequencies is obtained. The internal fields, the radiation fields, the effective loss tangent, and the input impedance are derived when the antenna is provided with a coaxial feed. The theory predicts that the air gap does not alter the relative field patterns significantly but it provides a simple parameter by which the resonant frequencies of the antenna can be tuned. Measurements have been performed on a 5 cm circular-disk microstrip antenna with an air gap and good agreement between theory and experiment is obtained.

Antenna engineering handbook /2nd edition/

Abstract: Essential principles, methods, and data for solving a wide range of problems in antenna design and application are presented. The basic concepts and fundamentals of antennas are reviewed, followed by a discussion of arrays of discrete elements. Then all primary types of antennas currently in use are considered, providing concise descriptions of operating principles, design methods, and performance data. Small antennas, microstrip antennas, frequency-scan antennas, conformal and low-profile arrays, adaptive antennas, and phased arrays are covered. The major applications of antennas and the design methods peculiar to those applications are discussed in detail. The employment of antennas to meet the requirements of today's complex electronic systems is emphasized, including earth station antennas, satellite antennas, seeker antennas, microwave-relay antennas, tracking antennas, radiometer antennas, and ECM and ESM antennas. Finally, significant topics related to antenna engineering, such as transmission lines and waveguides, radomes, microwave propagation, and impedance matching and broadbanding, are addressed. Bibtex entry for this abstract Preferred format for this abstract

Planar Circuit Analysis of Microstrip Radial Stub

Abstract: Microstrip radial line stubs are analyzed using a planar circuit technique and characterized for design purposes. Experiments performed on various structures are in excellent agreement with the theory.

Reactively steered adaptive array using microstrip patch elements at 4 GHz

Abstract: A reactively steered adaptive array (RESAA) has one element connected by a transmission line to a receiver and a number of closely spaced parasitic elements, each of which is terminated by an adjustable reactive load. The pattern is formed by control of the reactive loads. Experimental results and the theory are presented for a RESAA consisting of five microstrip rectangular patch elements resonant at 4.0 GHz. Using steepest descent control of the reactive loads in a power inversion mode (no reference), we find that a null with a depth of 30 dB (relative to the pattern maximum) and an angular width of about 25\deg can be steered towards an interferer. Typically, about 40 steps (iterations) are needed for forming the null. With the slow power meter and general purpose minicomputer that served as the controller, adaptation times of several seconds are required; extrapolation to a dedicated microprocessor controller predicts adaptation times of several milliseconds. Operation in a mode using a reference signal demonstrates that the pattern can be shaped to steer a null toward interference and a lobe towards a desired signal. The nulling bandwidth is approximately 40 MHz with this array. The advantages of a RESAA, as compared With a conventional adaptive array, include the elimination of the mixers and other hardware needed to perform the complex weighting of the output of each element at an intermediate frequency, and better pattern control for closely spaced elements. These advantages are obtained at the expense of a more complicated control algorithm.

A theoretical and experimental investigation of annular, annular sector, and circular sector microstrip antennas

Abstract: An analysis is presented for three related shapes of microstrip antenna elements: the annular; annular sector; and circular sector. The method of analysis involves the full expansion of resonant modes within the cavity formed by the radiating patch and the ground plane. Experimental results for representative radiators are also included for comparison.

Transmission line model for mutual coupling between microstrip antennas

Abstract: Although more rigorous treatments have been developed for mutual coupling between microstrip antennas, the purpose of this transmission line model is to provide a numerically efficient substitute for them. Therefore, two approximations have been introduced: first, the surface waves have been neglected and second, each rectangular resonator is replaced by two equivalent radiating slots. In most practical cases the approximations are acceptable; this has been proved while comparing the transmission line model with other published results. It is obvious that the efficieney of the transmission model and can be used to include mutual coupling in practical analysis or synthesis routines for arrays of rectangular microstrip antennas.

Broadband circular polarization arrangement for microstrip array antenna

Abstract: The invention relates to a circular polarization (CP) technique and a microstrip array antenna implementing this technique. Using four microstrip radiating elements with proper phasing of the excitation in a 2×2 array configuration, the technique averages out the cross-polarized component of the radiation, generating circular polarization of high purity. The technique is broadband and capable of dual-polarized operation. The resultant 2×2 array can be used either independently as a CP radiator or as the building subarray for a larger array.

Computer analysis method for arbitrarily shaped microstrip antenna with multiterminals

Abstract: An analysis method is presented for an arbitrarily shaped microstrip antenna with multiterminals. The method is based on the variational method and the modal-expansion technique. Eigenvalues and eigenfunctions are determined using the Rayleigh-Ritz method. Input impedance and other antenna parameters are derived at nonresonance. Furthermore, the network model, useful for the network analysis of a microstrip antenna with multiterminals, is presented by introducing an ideal transformer. Finally, numerical examples are compared with experimental results. The agreement is quite good, and the validity of the present method is confirmed.

Radiation characteristics of higher-order modes in microstrip ring antenna

Abstract: The results of the theoretical analysis of modal fields and radiation characteristics of the microstrip ring antenna are presented. Radiation patterns for the different modes are derived from the fringing fields at the inner and outer peripheries of the ring. Theoretical patterns are compared with experimental results at 1.8 GHz. The analyses show that the TM 1m -modes (m = 2, 4, 6,...) are suitable for broadband boresight antennas while TM 1m -modes (m = 1,3,...) may be used for narrowband boresight antennas.

Microstrip disk antennas, Part II: The problem of surface wave radiation by dielectric truncation

Abstract: The far zone fields radiated from a microstrip disk antenna with a truncated dielectric layer were obtained using the cavity model with magnetic side walls, the dyadic Green's functions are stratified media, and the integral representation analysis of the fields in the complex plane. It is shown that the truncation of the dielectric is responsible for the ondulations observed in the radiation patterns of these antennas and that they result from the interference of the space wave fields with those radiated as a consequence of the incidence of the surface wave into the truncation region. It is suggested that this interference problem may be alleviated by truncating the dielectric as far as possible from the antenna elements and by using lower values of dielectric thickness to disk radius ratios d/a , and of dielectric relative permittivities \epsilon_{r} .

Microstrip antenna system with fixed beam steering for rotating projectile radar system

Abstract: A microstrip antenna system has a central two-dimensional array (preferably square having at least 16×16 elements) of integrally formed conductive dual slot microstrip radiator patches. A corporate-structured array of interconnected microstrip feedlines connects a common input/output r.f. signal feedpoint to each of the central array patches and also incorporates a fixed-angle phasing offset so as to steer the main lobe or beam of the overall radiation pattern off-center. The common r.f. signal input/output connection point is itself physically offset to one side of the overall composite of array elements. Auxiliary tapered amplitude linear arrays of dual slot patches also preferably extend on all sides outwardly from the periphery of the central array so as to reduce the side lobe amplitude and main lobe beamwidth of the overall radiation pattern. Both series-fed and series-tapped tapered amplitude feedlines are used depending upon whether the auxiliary linear array extends in the E-plane direction or the H-plane direction. The fixed phasing offset is preferably in the H-plane direction of the overall central array. Pairs of broad-banding microstrip stubs may be disposed along the corporate structure feedline in association with predetermined subsets of dual slot patches within the central array so as to increase the frequency bandwidth over which impedance matched signal feeding is achieved.

Nested microstrip arrays

Abstract: An antenna structure in which two or more microstrip arrays are disposed onop of each other to minimize the required space. The shape of the microstrip elements and the polarization thereof are chosen so that the individual elements radiate only in specific areas along the edges of the elements with the remainder of the element having no appreciable electric field concentration. Because of the operating frequency of a microstrip element is a function of the size of the element, a second antenna of smaller higher-frequency elements may be disposed over a larger lower-frequency antenna such that the higher frequency antenna does not cover the areas of the lower antenna that radiate but lies over only those areas having no appreciable electric fields concentrations. Increasingly higher-frequency antennas can be placed on top of the lower-frequency antennas if the foregoing conditions are maintained with respect to all of the covered antennas. This arrangement permits separate feed networks and omnidirectional coverage or directional coverage for each of the arrays independent of the others.

A Multiport Patch Antenna for Mobile Communications

Abstract: Application of the circular patch antenna at the mobile is discussed. Diversity branches are available from the same patch by feeding at different backplane ports. The conditions for diversity action and appropriate analysis of the antenna are reviewed.

Resonant frequency of a tunable rectangular patch antenna

Abstract: The uniform transmission-line model is applied to determine the resonant frequency of a coaxial probe fed rectangular patch antenna tuned by a number of passive metallic posts suitably placed within the antenna's boundary. An approximate expression is given for the resonant frequency as a function of the post location and number, and of the other characteristic parameters of the antenna. Theoretical results are compared with available measured values.

The design of a slot array in nonradiating dielectric waveguide, part II: Experiment

Abstract: Measurement procedures for obtaining the self-impedance of an isolated inclined radiating slot in the metal wall of a nonradiating dielectric (NRD) waveguide are discussed. The design procedure for an antenna array fed by NRD-waveguide and making use of this information is described. As an example, the design, construction and evaluation of a ten-element input-matched broadside linear array is described.

Microstrip disk antennas, Part I: Efficiency of space wave launching

Abstract: A theoretical study on the problem of surface wave excitation of microstrip disk antennas is presented. The cavity model with magnetic sidewalls and dyadic Green's functions in stratified media is used to obtain the radiated fields in an integral form. Lossless media are assumed such that there is no cross coupling between the powers in the space ( P_{SP} ) and surface ( P_{SU} ) waves. The separate contributions of these two powers is examined. With the assumption that P_{SU} does not contribute to the main radiation patterns of the antenna an efficiency of space wave launching and a corresponding antenna directivity are defined. Values of efficiency and directivity as functions of the dimensions of the antenna and for two values of dielectric constants of the substrate are shown. Agreement of these results with some of the available data is observed. It is worth noting that P_{SU} may correspond to an appreciable portion of the total radiated power.

Microstrip patch array antenna

Abstract: A microstrip array with mutual coupled rectangular patch radiators is described. By the avoidance of a corporate feeding network, advantages in the antenna performance and design are realisable. Experimental results are presented for both linearly and circularly polarised antennas which demonstrate the usefulness of this special antenna configuration.

The effect of a dielectric cover on the current distribution and input impedance of printed dipoles

Abstract: The effect of the thickness and relative permittivily of a dielectric cover on a printed microstrip dipole has been analyzed. It is shown that the current distribution and the input impedance are, in general, very sensitive to variations of the cover parameters. For a dielectric plate with a constant thickness the dipole resonant length decreases substantially with an increase of the relative permittivity. Because of the limited bandwidth presented by single-element microstrip antennas the effects of the dielectric cover on the design of these antennas have to be carefully considered. For the calculation of the current distribution, the Hertz vector potential associated with the problem was determined for an element of current located in a stratified medium with four layers. Pocklington's integral equation was solved for the currents, using Galerkin's method with piecewise-sinusoidal expansion and weighting functions.