Showing papers on "Patch 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.

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. >

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.

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.

Cavity-backed wide slot antenna

Abstract: We propose a wide slot antenna to expand the frequency bandwidth of a cavity-backed slot antenna. In the antenna the slot width is significant in comparison with the slot length. We present the analysis of the antenna including the feed line. The result obtained is a 35% frequency bandwidth (VSWR < = 2), which is also verified by experiment.

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. >

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.

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. >

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. >

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. >

A broad-band transmission line model for a rectangular microstrip antenna

Abstract: A method is developed using the transmission line model to predict the input characteristics of rectangular microstrip antennas over a wide band of frequencies. A series combination of transmission lines is used to represent each transverse magnetic (TM) model. Following a brief summary of the basic transmission line model, the idea of an equivalent length, width, and feed offset are introduced to model each mode. The results predicted by the model compared well with experimental results that assumed varying feed positions. The concept of equivalent length, width, and feed offset was validated by experimental results but shows that the equivalent offset term needs some improvement. The number of modes incorporated in the model depends on the frequency range over which the antenna must be modeled. Using three transmission lines gives good results up to the frequency at which the TM/sub 02/ mode is excited. >

Frequency independent circular array

Abstract: A circular array includes a plurality of antenna elements which are spaced apart from each other and situated in a conical arrangement and in parallel rows circumferentially about the longitudinal axis of the conical arrangement. The circumferential spacing between the phase centers of adjacent antenna elements of any one row situated closer to the base of the conical arrangement is greater than that of adjacent antenna elements situated relatively closer to the apex of the conical arrangement. The respective operating frequencies of the antenna elements of any one row situated closer to the base of the conical arrangment is lower than the operating frequencies of the antenna elements of any other row situated relatively closer to the apex. The circuit array antenna further includes a plurality of feed lines, where each feed line is coupled to an antenna element of each row in progression. The circumferential spacing between the phase centers of adjacent antenna elements of the conical arrangement is maintained at a fixed value of the wavelength of the operating frequencies of the antenna elements.

Internally mounted broadband antenna

Abstract: An internally mounted broadband antenna (Figure 5) utilizing two resonators (503, 501 and 505, 501) and a reactive ground feed is disclosed. A nonconductive notch (511) separates a conductive surface (501) into two portions which are coupled to a respective one of each resonator. Each resonator (503, 501 and 505, 501) is a microstrip conductor forming a transmission line with its respective conductive surface portion. Coupling to the antenna is accomplished by connection (519 and 521) across the notch (511).

Stripline feed for a microstrip array of patch elements with teardrop shaped probes

Abstract: A circularly polarized microstrip array antenna utilizing a honeycomb substrate made of dielectric material to support on one side the microstrip patch elements in an array, and on the other side a stripline circuit for feeding the patch elements in subarray groups of four with angular orientation and phase for producing circularly polarized radiation, preferably at a 0°, 90°, 180° and 270° relationship. The probe used for coupling each feed point in the stripline circuit to a microstrip patch element is teardrop shaped in order to introduce capacitance between the coupling probe and the metal sheet of the stripline circuit that serves as an antenna ground plane. The capacitance thus introduced tunes out inductance of the probe. The shape of the teardrop probe is not critical. The probe capacitance required is controlled by the maximum diameter for the teardrop shaped probe, which can be empirically determined for the operating frequency. An aluminum baffle around each subarray blocks out surface waves between subarrays.

Wristband with loop antenna

Abstract: An apparatus for adjusting the length of a single segment loop antenna while automatically compensating for the antenna so as to maintain a substantially constant resonant frequency thereof.

The analysis of coaxially fed microstrip antennas with electrically thick substrates

Abstract: The analysis of a microstrip patch antenna with an electrically thick substrate is performed using a mixed potential integral equation. Basis functions are employed on the coaxial probe thus eliminating the often used thin substrate approximations. There is no theoretical limit to the thickness of the structures that can be analyzed. A special attachment mode, employed at the coaxial probe-antenna junction, is introduced. Measured and calculated input impedance results for isolated rectangular microstrip antennas are compared.

Dual polarization microstrip array antenna

Abstract: Dual polarization microstrip array antennas for high efficiency power reception or transmission of electro­magnetic waves are easy to manufacture, applicable over a wide range of frequencies and angles of incidence, and permit true conformal appli­cation and high power handling The antenna, according to an embodiment, has an array of microstrip patch antenna elements (3), wave filters (13), matching stubs (17) and rectifier term­inals (15), all highly symmetrically arranged to each other on one side of a dielectric layer (19) A common ground plane (21) is provided on the other side of the dielectric layer (19) Recti­fiers are connected to the terminals to produce rectified outputs of each patch antenna element (3)

Radar cross-section of microstrip antenna on normally biased ferrite substrate

Abstract: Calculated results for the radar cross-section of a microstrip antenna on a ferrite substrate are presented, and it is shown that the peaks in the RCS can be moved with respect to frequency by changing the magnetic bias field. This effect offers a way of minimising the radar visibility of microstrip antennas and arrays.

Dual plate antenna

Abstract: Portable radio equipment which is thin enough to enhance portability and, yet, has a sufficiently high antenna gain. The equipment has an antenna which is made up of a pair of metal plates located face-to-face, and a short-circuiting member for short-circuiting the metal plates. A circuit board loaded with radio circuitry is interposed between two metal plates with the radio circuitry being connected to the antenna. A capacitor is connected between the metal plates to lower the resonance frequency of the antenna, as needed. A circular cell for powering the equipment is located in a cell receiving portion near the short-circuiting member.

Broadband microstrip-fed antenna

Abstract: A broadband antenna capable of transmitting or receiving radio frequency signals. The antenna (16) includes a substrate (18) having a surface upon which a microstrip feed element (30) is positioned orthogonal to the substrate, and a portion of the antenna element (16) is positioned on and in direct contact with a portion of the microstrip feed element (30) for transmitting or receiving signals therebetween. A ground plane (32) is disposed on a surface of the substrate (28) which is in opposing relation to and spaced from the microstrip feed element. Additionally, the antenna element includes a tapered notch (22) of a "Vivaldi" configuration which facilitates endfire operation and reduces beamwidth.

Loop antenna with transmission line feed

Abstract: A loop antenna includes a circuit board having a ground plane layer. A formed loop is located on one side of the circuit board and a transmission line is located on the opposite side of the circuit board. Capacitors interconnect the ends of the formed loop and the transmission line. The transmission line is a microstrip formed by the ground plane layer in a microstrip portion. The circuit board includes RF circuitry that is located on the side of the circuit board opposite to the transmission line so that the ground plane shields the circuitry from the transmission line.

Passive temperature compensation scheme for microstrip antennas

Abstract: A temperature dependent capacitor formed from bi-metallic strips is used to compensate for changes in the resonant frequency of a microstrip patch antenna array structure due to dielectric constant thermal effects.

Planar FET oscillators using periodic microstrip patch antennas

Abstract: An integrated oscillator/antenna is presented that uses a single microstrip leaky-wave structure as both the resonant and the radiating element. This resonant antenna is connected to a GaAs metal-semiconductor field-effect transistor which acts as the negative resistance element in the oscillator circuit. This type of oscillator is similar in its operating principle to one reported using Gunn diodes and a periodically notched dielectric image guide. This circuit exhibits the high DC-RF conversion efficiency that is typical of field-effect transistor oscillators. The planar circuit is simple and inexpensive to construct, occupies a small volume, and can conform to different surface profiles. Such circuits are suitable for use in millimeter-wave systems as well as at microwave frequencies. A design procedure is given, and the performance of X-band prototype circuits is reported. Prototype circuits showed a 9 dB isotropic conversion gain and 40 MHz tuning range at 9.5 GHz. >

Analysis of circular microstrip antennas with superstrate

Abstract: The spectral domain analysis is applied to study the effects of dielectric cover on a circular microstrip patch antenna. Numerical examples indicate that the resonant frequency of the patch is decreased considerably while the bandwidth is varied slightly.

Method and apparatus for measuring the thickness of a layer of geologic material using a microstrip antenna

Abstract: A method of determining the thickness of a layer of material, such as soil, wood, ice or coal, that utilizes a microstrip antenna as a thickness measuring sensor. The sensor is positioned over the layer and a value for a parameter of the antenna such as conductance or resonant frequency is measured. The value is compared to a calibration table of values and the thickness of the layer is determined by interpolation. Alternatively, the value is compared to a control value to initiate a decision process. The decision could be that a layer of ice is building up on a wing of an aircraft or that an explosive device is buried under a layer of soil.

On the leaky modes of open microstrip lines

Abstract: Dispersion characteristics and modal currents of an open microstrip line are computed using the mixed-potential electric field integral equation. Particular attention is given to the correct determination of the radiating, leaky-wave modes.

Multifrequency antenna, useable in particular for space telecommunications

Abstract: The present invention relates to a multifrequency antenna comprising a microstrip patch first antenna (10, 11, 12) operating at one or more frequencies, and a second antenna (17) disposed in front of the antenna and using the same radiating surface and operating at a different frequency. The invention is applicable, in particular, to space telecommunications.

Accurate model for the input impedance of coax-fed rectangular microstrip antenna with and without airgaps

Abstract: A simple and numerically efficient model for the input impedance of a rectangular microstrip antenna with and without an airgap between the substrate and the ground plane is presented This airgap does not significantly alter the relative field pattern but it does provide a simple parameter by which the resonant frequencies of the antenna can be tuned This model describes an improvement to the cavity model of a rectangular coax-fed antenna whereby the dynamic permittivity accounts for the fringing fields of the patch This model, valid for both electrically thin and thick substrates is well suited for computer-aided-design (CAD) The computations are compared with experimental data, showing good agreement >