Showing papers on "Slot antenna published in 1988"

Aperture-coupled patch antennas with wide-bandwidth and dual-polarization capabilities

Abstract: The authors discuss the design of a wideband, dual-proportion, C-band patch radiator with a 20% bandwidth for input voltage-standing-wave ratio >

Opto-electronic vivaldi transceiver

Abstract: A planar integrated opto-electronic transceiver apparatus having a pair of broadband tapered slot line antennas which are monolithically integrated on an ion implanted silicon on sapphire substrate. An optical pulse which is applied to the narrow slot of the transmitting antenna, generates an electromagnetic transient to the antenna aperture from which it is radiated to receiver slot line antenna. The received electromagnetic transient is detected at the narrow slot and is time resolved by an optical sampling signal.

A linearly polarized radial line slot antenna

Abstract: A design for linearly polarized radial line slot antenna (RLSA) is proposed. A novel slot arrangement is presented which couples to the rotationally symmetric guided waves to produce a uniform aperture distribution with linear polarization. Basic characteristics were measured in the 12-GHz band on a model antenna. The radiation patterns indicate a reasonable cross-polarization level more than 15 dB below the copolarization. The poor VSWR response is typical for waveguide broadside arrays. A technique to suppress this reflection is to tilt the beam from the boresight. >

A design procedure for slot arrays fed by single-ridge waveguide

Abstract: R.S. Elliott's (1983) design procedure for arrays of longitudinal slots in one broad wall of each rectangular waveguide is extended to the case in which the waveguides have ridges in the opposite broad walls. External mutual coupling has been taken into account. A two-be-eight array was constructed and tested, and the results validate the theory. Ridging is significant because it permits E-plane scanning from broadside to endfire. >

Antenna theory and practice

Abstract: Electromagnetic Fields and Theory of Radiation. Thin Linear Antenna. Cylindrical Antenna. Biconical Antenna. Antenna Arrays. Loop Antenna. Helical Antenna. Slot and Micro-Strip Antennas. Horn Antennas. Reflector Antennas. Lens Antennas. Leaky-Wave And Surface-Wave Antennas - Dielectric And Dielectric-Loaded Metal Antennas. Wide-Band Antennas. Antenna Synthesis. Antenna Practice. Antenna Measurements. Electro-Magnetic Wsve Propagation.

The Design of Waveguide-Fed Slot Arrays

Abstract: Many different types of wave-guiding structures have found practical application in a variety of microwave devices. These guiding structures include the coaxial line, rectangular and circular waveguides, stripline, and microstrip. A characteristic of each of these structures is that it will support a set of modes, usually described as consisting of two subsets: TE (transverse electric) and TM (transverse magnetic). For the multiple-conductor structures (coaxial line, stripline, and microstrip) a TEM mode is also possible—indeed, is the dominant mode.

Coplanar patch antenna

Abstract: A coplanar patch antenna is formed, e.g as a printed circuit, on a dielectric support (1) by a metal patch (2) spaced from a coplanar ground plane (3) by a peripheral slot (4), and in the improvement is series fed by means of a slot line (5). The slot (4) can be made resonant by having a periphery of one wavelength or an odd multiple thereof, and a second slot line (7) can be fed into the slot (4) at a distance of one or an odd multiple of a quarter wavelength from the slot line (5) to provide an independent feed. The arrangement presents a feedpoint impedance of about 50 ohms at the ports (6,8) instead of about 400 ohms in prior arrangements. Balancing loads or 180 degree hybrid feeds to other quadrature ports (11,12) can be used to correct beam asymmetry due to the slot line feeders (5 and 7).

Quasi-optical HEMT and MESFET self-oscillating mixers

Abstract: Planar quasi-optical receivers that compactly integrate a coupled slot antenna and a HEMT or MESFET balanced self-oscillating mixer and on the same substrate for applications in microwave and millimeter-wave receiver arrays are discussed. Both the HEMT and the MESFET circuit are designed and demonstrated at X-band. The HEMT circuit exhibits an isotropic conversion gain of 4.5 dB and a noise figure of 6.5 dB. The isotropic conversion gain of the HEMT circuit is 7.5 dB higher than the mixer diode circuit previously reported. >

Mode stability of radiation-coupled interinjection-locked oscillators for integrated phased arrays

Abstract: An analysis is presented of a two-element, 10-GHz array consisting of two oscillators coupled solely by means of the free-space interaction between their respective antenna elements. The oscillators are modeled as energy-storing L-C tank circuits in parallel with voltage-dependent negative conductances. A simplified far-field slot antenna model is used to derive the mutual admittance of the two antennas. Even-odd mode analysis yields the normal modes of the system, and a theorem from averaged potential theory is used to determine which mode is stable. Two microstrip Gunn diode oscillators were built to verify the essential features of the model. Oscillator frequencies, relative phases, and radiation patterns were measured as functions of the interantenna distance, and the periodic alternation of modes with distance predicted by theory was confirmed quite well. >

Quasi-optical integrated antenna and receiver front end

Abstract: A quasioptical receiver front end applicable to both microwave and millimeter-wave receiver arrays is presented. Two planar microwave integrated circuit (MIC) quasioptical receiver circuit designs that integrate a coupled slot antenna, a Schottky-diode balanced mixer, and a local oscillator on the same substrate are described. The even-mode/odd-mode characteristics of the coupled slotlines are used to achieve intrinsic RF/LO and RF/IF isolation. To demonstrate circuit feasibility, X-band scaled models of the circuit unit using a Gunn-diode oscillator on an Epsilam-10 substrate, and MESFET local oscillator on a R/T Duroid substrate were built and tested. Results of these tests are included. >

Wide band antenna

Abstract: A cavity backed crossed slot antenna wherein the cavity depth d is less than one eighth of the operating wavelength λ at the lowest frequency of operation, the major dimension a of the cavity in the plane of the slots is less than one half of the wavelength λ at the lowest operating frequency, and the slots are excited by four symmetrically located capacitive coupled feed probes.

Slot coupling in a radial line slot antenna for 12-GHz band satellite TV reception

Abstract: Coupling between slots and slow-wave waveguides in a radial line slot antenna (RLSA) is discussed. Field analysis of the waveguide with a surface impedance wall revealed a considerable change in the propagation constant due to coupling. Experiments were performed to confirm these results and to obtain the surface impedance for actual slots. The change in the propagation constant caused the antenna efficiency to exhibit its maxima at two separated frequencies. An efficiency of 60% and 50% was measured at 11.6 and 12.4 GHz, respectively, which confirms a theoretical prediction. This effect suggests the possibility of broadband planar antennas. >

Characterisation of an optoelectronically pulsed broadband microwave antenna

Abstract: Exponentially tapered coplanar stripline antennas are characterised for the generation of broadband transient radiation with excitations from picosecond photoconductors. The measured radiation spectrum extends up to 150 GHz. The dependence of the antenna bandwidth on its geometry is investigated.

A linearly-polarized radial line slot antenna

Abstract: The authors present the design of a linearly polarized RLSA (radial line slot antenna). A key feature consists of the slot arrangement that realizes the linear polarization of the rotationally symmetric travelling wave excitation. The design is verified by experiments. Fresnel patterns indicate the reasonable XPD of more than 17 dB. To suppress the reflection from slots, beam tilting techniques should be used in the practical design of the linearly polarized RLSA. >

Realizable feed-element patterns and optimum aperture efficiency in multibeam antenna systems

Abstract: The results of an earlier paper by Y Rahmat-Samii et al (ibid, volAP-29, pp961-3, 1981), regarding realizable patterns from feed elements that are part of an array that feeds a reflector antenna, are extended The earlier paper used a cos/sup q/ theta model for the element radiation pattern, whereas here a parametric study is performed, using a model that assumes a central beam of cos/sup q/ theta shape, with a constant sidelobe level outside the central beam Realizable q-values are constrained by the maximum directivity based on feed element area The optimum aperture efficiency (excluding array feed network losses) in an array-reflector system is evaluated as a function of element spacing using this model as well as the model of the earlier paper Experimental data for tapered slot antenna arrays are in agreement with the conclusions based on the model >

A leaky-wave antenna in nonradiative dielectric waveguide

Abstract: A leaky-wave mechanism in a nonradiative dielectric (NRD) waveguide is described. The antenna used in the analysis consists of a long slot in one ground plane of the NRD guide; the currents present in the side walls cause the slot to radiate as a traveling-wave antenna. The antenna was designed to operate at 9.5 GHz to reduce the costs involved in working at high frequencies. The analysis of the slot follows the procedure outlined by L.O. Goldstone and A.A. Oliner (1959). A simple expression for the amount of coupling from the guide is derived under certain assumption made because information on the reactances necessary to model the slot is not as yet available. The theoretical coupling values verified by measurement and the design, construction, and performance of both leaky-wave antennas are described. >

Slot antenna in circular waveguide.

Abstract: Disclosed is a circular waveguide in which a slots are formed which are shaped and disposed such that they interrupt either the right hand or left hand circulating mode (RC and LC respectively) residing in the waveguide. Locating the slots in the waveguide wall is accomplished in accordance with the theory that for TE modes in circular waveguide with circumferential variation of e.sup.±jmφ, current flow lines are produced that are helical. The slots are located so as to interrupt the helical current of the desired mode. In one embodiment, an ortho-polarization mode transducer and a circular polarizer are used to feed the slotted waveguide. By control of the amplitude and phase of the energy propagating in the waveguide, aximuthal pattern control can be effected. By dielectric loading the waveguide to make λ g in the loaded waveguide equal to λ-free space, endfire radiation can be achieved.

Efficient and accurate method for calculating and representing power density in the near zone of microwave antennas

Abstract: A method for computing and exhibiting Fresnel-region fields radiated by microwave antennas that uses plane-wave scattering matrix analysis is presented. Near-fields are calculated by numerically integrating the complex far-field antenna pattern. The predicted near fields are exhibited as relative power density contours lying in a longitudinal plane bisecting the antenna's aperture. With spatial-coordinate scaling, each set of contours becomes a function of the relative aperture distribution and the electrical size of the antenna. If the electrical diameter is much larger than any normalized transverse coordinate of interest, the contour set becomes invariant with respect to antenna size. The coordinate normalization can produce contours applicable to any antenna with the same relative aperture distribution, regardless of antenna size. >

Fin-line horn antenna

Abstract: A fin line circuit card containing a fin line slot feeds a dipole antenna ich extends a quarterwave outside the waveguide and provides an energy beam focal point at or near the open end of the waveguide. The dipole antenna thus maintains a wide and nearly constant beamwidth, low VSWR and a circular symmetric radiation pattern for use in electronic warfare direction finding and surveillance applications.

Integrated millimeter-wave transceiver

Abstract: An integrated millimeter-wave transceiver comprising a substrate on which is provided an annular slot antenna (D) and a balanced mixer (F). Transmitter power is applied to one point of the antenna and the balanced mixer (F) is coupled to a second point of the antenna, the second point being orthogonal to the one point in the plane of the antenna. The coupling of the balanced mixer to the second point is by way of a coplanar waveguide (C). A short circuit (H) in the coplanar waveguide (G) at a quarter wavelength from the mixer prevents an even (asymmetric) mode on the coplanar waveguide from being propagated to the antenna. An IF signal is derived using an RF band stop filter (I).

Variable circular polarization antenna having parasitic Z-shaped dipole

Abstract: A specially designed, Z-shaped, parasitic dipole is spaced radially outwardly from the slot provided in a cylindrical antenna; a controlled amount of energy which is in a horizontally polarized direction is coupled to the Z-shaped dipole so as to radiate energy into the vertical plane, thus creating a variable circularly polarized antenna capable of adding a selectable amount of vertical component to the horizontal in quadrature; since the dipole element, which parasitically develops its polarized energy, is in the same horizontal plane as the polarized energy emanating from the slot, a good, ie constant, axial ratio is maintained throughout the elevation pattern

A triplate stripline slot antenna developed for time-domain measurements on phased arrays

Abstract: A frequency-independent, triplate feed structure is described that is easily matched, even if slot shape and dimensions are varied, and has the advantage of causing a minimum of disturbance to the aperture fields. This feed structure does not extend the impulse response of the antenna. The properties of the slots can thus be separated from the effects of the edges of the ground plane by making measurements in the time domain. The results show that the resonant frequency may be predicted by simple cavity theory. >

Moment method analysis of a feeding system in a slotted-waveguide antenna

Abstract: The electromagnetic boundary value problem of finite thickness orthogonal waveguides coupled by inclined slots is studied using a moment method and dyadic Green's function theories. The coupling properties between two inclined slots are analysed and a model of equivalence circuits is put forward. Theoretical results are presented for scattering and impedance parameters of slots. In general, these are in good agreement with the experimental measurement.

Measured relative performance of antenna pattern diversity, antenna angle diversity and vertical space diversity in Mississippi

Abstract: Presents the results of an experiment to test the relative performance of antenna pattern diversity, antenna angle diversity, and vertical space diversity for line-of-site microwave digital radio. The experimental results indicate that if the outage time is due to thermal noise it is not negligibly small compared to that caused by multipath dispersion, the diversity improvement factor of vertical space diversity is greater than those of antenna pattern diversity or antenna angle diversity by at least one order of magnitude. Thus, if thermal noise fade margin is not substantially greater than the dispersive fade margin, vertical space diversity is preferred. >

Frequency-Independent Antennas

Abstract: Antennas which theoretically have no limitation on the bandwidth are called frequency independent. In practice, the lower frequency limit is determined by the size of the antenna; the upper frequency limit, by the precision of construction. Actually, the electrical performance is not strictly independent of frequency, rather it is periodic with the logarithm of the frequency. Hence these antennas are called logarithmically periodic, log-periodic, or simply LP antennas. Some, which have the shape of equiangular spirals, are called logarithmic spirals,or log-spirals.

Dual-Band Microstrip Antenna With Reactive Loading

Abstract: Effective but bulky coaxial stub replaced. Short-circuited microstrip transmission line serves as reactive loading element for microstrip antenna. Constructed integrally with stripline radiating element, shorted line preserves low microstrip profile and enables tuning of antenna for two-band operation.

Vector fourier transform analysis of dielectric‐covered slot in the broad wall of a waveguide

Abstract: The resonant length versus offset of a dielectric-covered narrow square ended slot is studied. The slot, located in the broad wall of a rectangular waveguide, is excited by a single mode. The external field is matched to the internal field by the Galerkin method concept. Corrections due to finite wall thickness are also included.

Design of a radial line slot antenna with improved input VSWR

Abstract: A radial line slot antenna is a planar antenna which in principle has high efficiency. An excellent efficiency of no less than 57 percent has been measured in the 12-GHz band. To realize the predicted 80 percent efficiency, reflection in the antenna feeding structure should be suppressed. In this paper, field analysis by means of the finite element method (FEM) provides the shapes of the feeding structures which minimize the reflection. Numerical results predict that the antenna overall reflection can be suppressed to less than -15 dB. The theoretical design is confirmed by the model experiments in 6-GHz band. The optimum design reduces the efficiency degradation due to reflection from 15 to 3 percent.