Showing papers on "Patch antenna published in 1985"

Microstrip antenna aperture-coupled to a microstripline

Abstract: A new technique for feeding printed antennas is described A microstrip antenna on one substrate is coupled to a microstripline feed on another parallel substrate through an aperture in the ground plane which separates the two substrates A simple theory explaining the coupling mechanism is presented, as well as measurements of a prototype aperture-fed antenna

Nonradiating edges and four edges gap-coupled multiple resonator broad-band microstrip antennas

Abstract: Two novel configurations for increasing the impedance bandwidth of the microstrip patch antennas are described. One of these configurations uses two additional resonators which are gap-coupled to the nonradiating edges of a rectangular patch, whereas in the second case, four additional resonators are gap-coupled to the four edges of a rectangular patch. Green's function approach and segmentation method are used for analysis. The experimental results are in reasonable agreement with analysis and impedance bandwidths of 480 MHz and 815 MHz are obtained for the three resonators and five resonators configurations, respectively (in S -band with substrate \epsilon_{r} = 2.55 and thickness = 0.318 cm).

Dual-band reactively loaded microstrip antenna

Abstract: A previously derived theory is applied to a microstrip antenna with a reactive load to produce a dual-band radiator. A model consisting of a rectangular patch radiator loaded with a variable length short-circuited coaxial stub was investigated experimentally. Comparisons of theoretical predictions and experimental data are made for the impedance and resonant frequencies as a function of the position of the load, the length of the stub, and the characteristic impedance of the stub.

Electric surface current model for the analysis of microstrip antennas on cylindrical bodies

Abstract: An approach to the analysis of microstrip antennas on cylindrical bodies is presented. The printed radiator is replaced by as assumed surface current distribution, and the fields are solved taking into account the presence of the dielectric layer and the metallic cylinder. Calculation takes place in the Fourier domain. The far field, calculated asymptotically from this solution, is used to get the radiation patterns of the wraparound antenna for any dielectric and the half-wavelength patch for \epsilon_{r} = 1 .

Directly coupled multiple resonator wide-band microstrip antennas

Abstract: Three new configurations for increasing the impedance bandwidth of the microstrip patch antennas are described. In these configurations, additional resonators are directly coupled through short sections of microstrip line to the radiating edges, nonradiating edges, and all the four edges of the rectangular patch antennas, respectively. Green's function approach and segmentation method are used for the analysis. The experimental results are in reasonable agreement with the analysis and impedance bandwidths of 548 MHz, 605 MHz, and 810 MHz are obtained for these three configurations, respectively in S -band (substrate thickness = 0.318 cm and \epsilon_{r} = 2.55 ). The variation in the radiation pattern over this impedance bandwidth is discussed.

Adaptive array antenna

Abstract: A small linearly polarized adaptive array antenna for communication systems is disclosed. The directivity and pointing of the antenna beam can be controlled electronically in both the azimuth and elevation planes. The antenna has low RF loss and operates over a relatively large communications bandwidth. It consists, essentially, of a driven λ/4 monopole surrounded by an array of coaxial parasitic elements, all mounted on a ground plane of finite size. The parasitic elements are connected to the ground plane via pin diodes or equivalent switching means. By applying suitable biasing voltage, the desired parasitic elements can be electrically connected to the ground plane and made highly reflective, thereby controlling the radiation pattern of the antenna.

Input impedance of annular ring microstrip antenna using circuit theory approach

Abstract: Input impedance and bandwidth of an annular ring microstrip antenna have been determined by modeling the antenna as a section of radial line loaded with wall admittances. The effect of mutual coupling between the radiating apertures has been taken into account. The theoretically calculated values of input impedance for TM 12 -mode are compared with measurements. The agreement is good. Higher order modes have been found to be present in the vicinity of TM 12 -mode. The reactance due to these modes can be utilized to increase the voltage standing-wave ratio (VSWR) bandwidth of the antenna.

Electric surface current model for the analysis of microstrip antennas with application to rectangular elements

Abstract: An approach to the analysis of microstrip antennas which is applicable also to relatively thick substrates using the relevant Green's function is presented. The Green's function is derived and closed form expressions for various antenna characteristics which explicitly take into account the presence of the dielectric material are obtained in terms of the electric surface current density. For rectangular microstrip elements near resonance the current distribution is approximated using lossless transmission line analysis, thus enabling the complete evaluation of the characteristics of the element near resonance. The results obtained in this approach for the radiation resistance, surface wave resistance, radiation pattern, directivity, and bandwidth are presented in a detailed set of graphs for a representative set of parameters.

Theory and experiment on microstrip antennas with airgaps

Abstract: In a microstrip antenna, the resonant frequency of a particular mode is determined by the shape and size of the conducting patch, the relative permittivity of the substrate and, to some extent, the thickness of the substrate. If the resonant frequency is to be changed, a new antenna is usually needed. Recently, Lee and Dahele have shown that the resonant frequencies of microstrip antennas can be changed by introducing an adjustable airgap between the substrate and the ground plane. In addition to providing a means for tuning the resonant frequencies, the airgap also has the effect of increasing the bandwidth of the antenna. The purpose of the paper is to present a comprehensive report on our research on microstrip antennas with airgaps. First, experimental results obtained by introducing an airgap in (i) circular-discs, (ii) annular-rings and (iii) dual-frequency stacked-disc microstrip antennas are presented. Secondly, the theories that have been developed are described. Thirdly, comparison between theoretical and experimental results is given.

Dual-band microstrip antennas with monolithic reactive loading

Abstract: The design and experimental measurement of a dual-band, monolithic microstrip antenna is presented. The structure utilises a short-circuited length of microstrip transmission line to provide reactive loading and, thereby, retains the low-profile characteristic of a normal microstrip patch radiator.

Rectangular ring and H-shaped microstrip antennas—alternatives to rectangular patch antenna

Abstract: H-shaped and rectangular ring microstrip antennas have been compared with the commonly used rectangular patch antenna. It has been found that the H-shaped patch antenna is smaller in size (about half), and is broadbeam but with narrow bandwidth. On the other hand, for larger bandwidth and/or narrow beamwidth applications a rectangular ring antenna is better than a rectangular patch antenna. Because of size reduction the H-shaped patch looks attractive for UHF applications.

Shortened wideband decoupled sleeve dipole antenna

Abstract: A shortened wideband decoupled sleeve dipole antenna is disclosed in which a helically wound upper radiating element and an inductively loaded lower radiating sleeve element reduce the linear size of the antenna. Substantial decoupling is provided by a helically wound feed coaxial transmission line within the sleeve element. A matching network at the antenna feed point provides capacitive reactance above the antenna resonant frequency and inductive reactance below the antenna resonant frequency such that an impedance match between the feed coaxial transmission line is obtained at frequencies above and below the resonant frequency and dual-band performance may be obtained.

Wideband multilayer coaxial-fed microstrip antenna element

Abstract: Electrically thick (and hence wideband) microstrip patch antenna elements are difficult to excite without adversely affecting their performance. A novel feeding technique is presented which circumvents the difficulties. A simple design theory is presented and a practical example is described which operates between 11 and 12 GHz.

Microwave plane antenna

Abstract: A microwave plane antenna in which antenna bodies carrying thereon respectively at least a pair of microstrip lines are mounted to a supporting frame through means for movably positioning the antenna bodies along a plane including an axis perpendicular to the plane of the antenna body and another axis in the width direction of each pair of the microstrip lines, whereby the main beam direction of the plane antenna is made settable optionally in three-dimensional zone to be in the optimum direction with respect to a geostationary broadcasting satellite for remarkably improving the reception gain.

Microstrip array antenna

Abstract: PURPOSE:To realize light weight by forming a path antenna and a feeding circuit on one plane with etching, covering a part of the feeding circuit with a metallic shield plate so as to attain tri-plate structure thereby suppressing the deterioration of the directivity due to the leaked radiation from the feeding circuit and utilizing the dielectric plate for reinforcement for the incorporated structure with the antenna. CONSTITUTION:The patch antenna 21 and the feeding circuit 23 are etched on the surface of a dielectric substrate 24. The feeding circuit 23 is designed as a strip line and the feeding circuit 33 of the part shielded by the metallic plate 26 is designed as a tri-plate line. Since the structure like this is adopted, the radiation of an electromagnetic wave from the feeding circuit 33 is shielded by the metallic plate 26 having a dielectric layer, while power is supplied to the feeding circuit 23 not covered by the metallic plate 26 and the patch antenna 21 so as to attain a desired directivity.

Wide-band matching of a small disk-loaded monopole

Abstract: A wide-band, electrically small, disk-loaded antenna, comprising of a disk, 0.26 wavelength (at midband) in diameter, located 0.097 wavelength above a ground plane, has been designed and tested. A unique experimental procedure was used to determine the parameters of the impedance matching network, which consists of a conductive biconical center post and two structural side posts located in the space under the disk. The resulting antenna has a maximum voltage standing-wave ratio (VSWR) of 2:1 over a frequency bandwidth ratio of approximately 2:1. A second model, designed using the same technique, has a maximum VSWR of 3:1 over a frequency bandwidth ratio of 3:1. This antenna was compared to a multi-element disk-loaded antenna (with the same size profile) designed by Dr. Georg Goubau. This multi-element antenna also has a maximum VSWR of 2:1 over a frequency band of approximately 2:1. The comparison shows that the simple disk-loaded antenna, with fixed double tuning, achieves the same low VSWR as the multi-element disk-loaded antenna with fixed triple tuning. Therefore, an increase in bandwidth could be achieved in the simple disk-loaded antenna by applying higher order tuning.

Patch antenna with a strip line feed element

Abstract: A patch-type antenna is disclosed for radiating electromagnetic radiation in the microwave band. The antenna comprises first and second electrically conductive plates which are supported in spaced-apart parallel relationship. The first plate serves as a ground plane, whereas the second plate forms a patch antenna element. A feed element supplies RF energy to the patch antenna without physically contacting it. This feed element is formed by an elongate, electrically conductive strip line arranged between the two plates and extending from one edge of the second plate to an interior point thereof. The length of this feed element, in its longitudinal direction, is approximately equal to one fourth of the wavelength of the EMR radiation by the antenna at the radio frequency applied thereto.

A bandwidth enhancement method for microstrip antennas

Abstract: Bandwidth enhancement methods for electromagnetically coupled microstrip dipoles are discussed. It is demonstrated that if parasitic metallic strips are incorporated in the structure either co-planar and parallel to the embedded microstrip transmission line open end, or between the transmission line and the microstrip dipole, then substantial bandwidth enhancement results. Experimental verification of this model is introduced for a bandwidth definition based on the frequency range which satisfies a voltage standing-wave ratio (VSWR) \bar{E} - and \bar{H} -plane patterns verify the theoretical model which accounts for radiation from the microstrip dipole, the parasitics, and the transmission line.

Generalised transmission line model for microstrip patches

Abstract: A transmission line model for microstrip configurations, for which separation of variables is possible, is presented. For this, the patch is modelled as a transmission line joining the radiating apertures. Each section of the transmission line is replaced by a π-network. The effect of apertures in the direction perpendicular to the direction of propagation is included through the complex eigenvalues. The effect of mutual coupling between the radiating edges can be described using variational technique and finally incorporated in the equivalent circuit of the structure. Application of the transmission line method appears to be large. Some patch shapes have been analysed and others indicated.

Broadband printed circuit antenna with direct feed

Abstract: A relatively broadband printed circuit antenna structure includes a dielectric sheet having printed circuit-like conductive structures printed on both sides in predetermined registration with one another. A traditional non-radiating microstrip transmission line structure extends from a common r.f. feedpoint to at least one terminal end portion. However, apertures disposed within the underlying (or overlying) conductive reference surface of the double-cladded printed circuit board in the vicinity of each terminal end cause substantial r.f. radiation to occur over a relatively broader bandwidth than with a more traditional microstrip antenna radiator structure. In one embodiment, the aperture in the microstrip ground plane itself becomes a radiating aperture due to the transmission line currents flowing within the ground plane. In other embodiments, the terminal end portion of the microstrip transmission line becomes a monopole radiator when it is encompassed by an aperture or opening in the pattern of the printed ground plane. A conductive reflector surface may also be disposed about one-fourth wavelength behind the printed ground plane--unless radiation directed away from either side of the antenna structure is desired.

Analysis of elliptical and circular microstrip antennas using moment method

Abstract: A method of calculating the input impedance of either a circular or a slightly ellipitcal microstrip antenna excited by a coaxial probe is presented. Using the reaction integral equation and the exact dyadic Green's function, the finite substrate thickness is taken into account in the formulation. Good agreement with experimental results for an elliptical patch is obtained and a design procedure for a circularly polarized antenna is presented.

Integral monitor system for circular phased array antenna

Abstract: The circular phased array antenna includes a plurality of radiating elements spaced about the circumference of a mounting ring. The radiating elements are fed with r.f. currents having relative phase and amplitude distribution to form a focused beam from the antenna. The beam is steerable to a selected direction. The monitor system includes a probe element mounted near each radiating element, phase shifters and couplers for combining signals from the probes into a transmission line. The amplitude of the transmission line signal is compared with a known value of signal for a normally operating antenna for each beam direction. A failure alarm is generated whenever the difference between the compared signals exceeds tolerance.

Microstrip Transmission Line with Finite-Width Dielectric and Ground Plane (Short Paper)

Abstract: Design data for microstrip transmission lines with finite-width dielectric and ground plane are presented. The characteristic impedance and velocity of propagation are tabulated from results of a moment-method solution of a quasi-TEM transmission-line model of this microstrip structure.

Microstrip patch antenna system

Abstract: A microstrip antenna system (10) is comprised of either a single antenna element (patch) (16) or a plurality of stacked antenna elements (16,36 and 40) having one or more feedpins (30) connected to a corresponding number of conductive elements (fiags) (28) capacitively coupled to the antenna element or elements. The one or more feedpins (30) have an inductive reactance which is canceled by trimmed flags (28) to provide the capacitance necessary to cancel the inductance for tuning the one or more antennas (16, 36 and 40) and providing maximum gain and minimum VSWR.

Vandalism-resistant UHF antenna

Abstract: A vandalism-resistant antenna for the UHF band comprises a ring-shaped radiator printed on a dielectric board or disc mounted within a shallow enclosure of insulating material having high impact strength. The radiator is approximately 1/4 wavelength long at the operating frequency and is located at a constant spacing above a ground plane. A coaxial RF connector fastens the radiator-board assembly to a mounting surface serving as the ground plane, and couples the antenna to a transmitter or receiver.

Microwave oven having resonant antenna

Abstract: A circularly polarized microwave oven. Microwave energy is coupled from a waveguide above the ceiling to the cavity by a rotatable vertical probe extending through a circular aperture in the cavity. A strip conductor closely spaced to the ceiling to limit radiation therefrom conducts the microwave current to an air dielectric patch antenna radially offset from the axis of the probe. A vertical section of the strip conductor spaces the patch antenna more than one-eighth wavelength from the ceiling which functions as a ground plane. The patch antenna is rectangular and the dimensions of its sides are selected to be respectively resonant above and below the operating frequency of the oven. More specifically, the dimensions are selected so that the orthogonal currents parallel to the rectangle sides produce orthogonal radiated components that are equal in magnitude and separated by 90° in phase. Accordingly, the resonant patch or flag antenna radiates substantially circular polarization. The probe is supported on a vertical post of a support cradle suspended from the ceiling and the patch antenna is rotated about the axis of the probe.