Showing papers on "Reflective array antenna published in 1987"
TL;DR: In this article, a nearly distortionless antenna beam pattern and 180° steering were demonstrated in a linear seven-element array with a Bragg cell and an offset and radar frequency of 3.2 GHz.
Abstract: Microwave signals for all array elements in a phared array microwave antenna are simultaneously generated by spatial sampling of a moving sinusoidal interference pattern formed between two frequency-offset injection-locked laser diodes. The offset and radar frequency of 3.2 GHz were generated by a Bragg cell. A nearly distortionless antenna beam pattern and 180° steering are demonstrated in a linear seven-element array.
64 citations
Patent•
29 Sep 1987
TL;DR: In this article, the performance of an electronic system utilizing a phased array antenna as its principal radiator into a predetermined sector of space is tested using an enclosure which bounds a miniature anechoic chamber located in the near-field region of the antenna array and lined with material absorbing free space electromagnetic radiation.
Abstract: An arrangement for testing the performance of an electronic system utilizing a phased array antenna as its principal radiator into a predetermined sector of space includes, as one of its main components, an enclosure which bounds a miniature anechoic chamber located in the near-field region of the antenna array during the performance of a testing operation and lined with material that absorbs free space electromagnetic radiation. The enclosure has an opening that is aligned with the phased array antenna the performance of which is being tested. Two dual-polarized testing horn antennas are situated at a wall of the enclosure that is opposite to the wall provided with the opening. Electrical signals received from the horn antennas and representative of the near-field electromagnetic radiation emitted by the phased array antenna are supplied to an evaluating circuit which gives indication of the performance of the electronic system of the phased array antenna. A control circuit is employed for energizing the testing antennas in any desired manner to issue electromagnetic radiation toward the phased array antenna being tested. A polarimeter is used to accurately determine the polarization capabilities of the antenna over a wide bandwidth.
27 citations
Patent•
03 Sep 1987TL;DR: In this article, a radio frequency transponder/repeater is provided where an array of receiving antenna elements is coupled to the array of transmitting antenna elements to provide a directional antenna system.
Abstract: A radio frequency transponder/repeater is provided wherein an array of receiving antenna elements is coupled to an array of transmitting antenna elements to provide a directional antenna system and including additionally an internal radio frequency source which is also coupled to the array of transmitting antenna elements. With such arrangement, an internally generated signal provided by the radio frequency source may be transmitted using the transmitting array of the Van Atta System.
26 citations
01 Jun 1987
TL;DR: In this article, a planar phased array (PFA) was proposed as one of the land vehicle antennas for the U.S. Mobile Satellite Experiment (MSAT-X) program, where the objective is to develop medium gain satellite tracking antennas that will alleviate the spacecraft power burden through higher gain, and enable multiple-satellite operation in the same frequency band through narrower beam.
Abstract: The planar phased array, due to its low profile and beam agility, has been proposed as one of the land vehicle antennas for the U.S. Mobile Satellite Experiment (MSAT-X) program. The objective is to develop medium gain satellite tracking antennas (as versus omni low gain antennas) that will alleviate the spacecraft power burden through higher gain, and enable multiple-satellite operation in the same frequency band through narrower beam. In addition, this narrower beam can spatially filter out a significant portion of the undesired multipath component. The major challenges are to seek technologies that will minimize the antenna insertion loss, achieve accurate beam pointing with sufficient inter-satellite isolation, and minimize the antenna production cost.
23 citations
Patent•
27 May 1987
TL;DR: In this article, the phase difference between the signal from the reference antenna and the signals from the other antennas is used to determine the direction of the signal in a radio direction finding system.
Abstract: Radio direction finding equipment has an array of direction finding antennas. The antennas are connected to receivers and signals from the antennas are processed, for example with a microcomputer, to give direction information derived from the phase difference between the signals. A reference antenna is also provided and this is of greater sensitivity than the other antennas. The direction information is derived from phase differences determined between the signal from the reference antenna and the signals from the other antennas.
20 citations
15 Jun 1987
13 citations
15 Jun 1987
13 citations
01 Jun 1987
TL;DR: Two types of compact mobile antennas for a multi-beam satellite communication system are described, one of them is conically shaped beam antennas and the other is an electronically controlled beam-steerable antenna with a simple tracking system.
Abstract: This paper describes two types of compact mobile antennas for a multi-beam satellite communication system. One of them is conically shaped beam antennas. Quadrifilar helix and microstrip antenna are discussed, and they can be extremely simple and inexpensive antennas, although their beamwidths are narrow. The other one is an electronically controlled beam-steerable antenna with a simple tracking system. This antenna is applicable as a mobile antenna to cover a wide elevation angle.
10 citations
01 Aug 1987
Abstract: Present methods for determining open area as well as other test site qualifications to measure radiated emissions for compliance with FCC and other regulatory requirements depend on comparing horizontal polariza tion site attenuation measurements to a theoretical m odel.1 Horizontal polarization measurements are generally inadequate to identify site anomalies which may actually cause significant errors when equipment emision com pliance is subsequently measured. Both vertical and horizontal site attenuation measurements are necessary as well as adequate theoretical models to use in the comparisons. This paper summarizes recent efforts of the voluntary standards community to standardize adequate site qualification measurements. This work is being considered primarily by the American National Stan dards Institute Accredited Standards Committee C63 (EMC) and the Special International Committee on Radio Interference (CISPR).2,3
8 citations
01 Apr 1987
TL;DR: In this paper, the authors present an overview of the current multi-beam and contoured-beam antenna technology and the limitations of the offset reflector with respect to beam scanning and cross polarization.
Abstract: : High-gain spacecraft antennas with multiple beams and contoured beams are key components in satellite communications and direct broadcast systems. This is reflected on the latest generation of communications satellites, where the antenna subsystem is the largest subsystem with its weight of more than 300 kg. The antennas achieve a large communications capacity through multiple frequency re-uses and may be reconfigured to serve different coverage areas. The paper overviews the current multi-beam and contoured-beam antenna technology. Different implementations, reflector or lens with feed array or direct radiating array, are considered. The emphasis is placed upon systems with offset paraboloidial reflectors. The limitations of the offset reflector with respect to beam scanning and cross polarization are reviewed. computer-aided design procedures and design examples are presented.
TL;DR: In this paper, the radiation and reception characteristics of a planar array of straight-wire coupled antennas are analyzed by a numerical method in the time domain, and the results are used to show how the monopulse technique with the slope pattern promises a much higher accuracy of angle measurement for a target.
Abstract: The radiation and reception characteristics of a planar array of straight-wire coupled antennas are analyzed by a numerical method in the time domain. The numerical method allows us to calculate some significant magnitudes in an array of coupled wire antennas, such as the frequency dependence of the self- and mutual impedances between antennas. The antennas are fed by a time-varying Gaussian pulse, and they are loaded with various nonlinear elements to exert some control over the radiation field. The results are used to show how the monopulse technique with the slope pattern promises a much higher accuracy of angle measurement for a target.
01 Feb 1987
TL;DR: In this paper, an eight-element linear array of aperture coupled patches that is designed for Eplane scanning is presented, where an intervening ground plane isolates the feed network from the radiating face of the array and undesirable via connections are not required.
Abstract: : Phased arrays of microstrip patch antennas are being studied extensively millimeter wave applications, in which the feeds for several elements including the T/R modules might be integrated onto a single GaAs substrate It is hoped that this integrated method of fabrication will improve performance and reduce the cost per element in large arrays Many investigators are finding, however, that patch arrays on GaAs do not perform as well as they would on a lower permittivity substrate Also, the area available in the unit cell (generally lambda(o)/2 by lambda(o)/z) is not sufficient to place the radiators and all of the circuit components on a single surface The aperture coupled patch antenna permits the use of a low epsilon(r) substrate for the antenna, and GaAs for the active circuits An intervening ground plane isolates the feed network from the radiating face of the array, and undesirable via connections are not required This paper describes an eight-element linear array of aperture coupled patches that is designed for E-plane scanning
15 Jun 1987
TL;DR: In this paper, the Fourier transform relationship between the far-field pattern and a function related to the indud current is exploited to localize the distortion with the aid of an FFT algorithm.
Abstract: Among the many different diagnostic techniques, microwave holography has been s~~ccessfully applied in recent years [l-31. In this technique, the far-field amplitude and phase are measured and then the Fourier transform relationship which exists between the far-field pattern and a function related to the indud current is exploited to localize the distortion with the aid of an FFT algorithm. Up to now the technique has been applied to far-field data either measured in the far field or construded from planar near-field measurements.
Patent•
19 Jun 1987
TL;DR: In this paper, the authors proposed a multi-band antenna for the GHz band, where at least three broadband spiral antennas for the reception of radar signals are arranged uniformly, concentrically, about a centre axis.
Abstract: In the proposed multi-band antenna for the GHz band, at least three broadband spiral antennas for the reception of radar signals are arranged distributed uniformly, concentrically, about a centre axis. Located in the centre of the spiral antennas are a plurality of millimetric-wave antennas, one of which, on the centre axis, is the transmitting antenna and at least three of which, grouped around it, are the receiving antennas. In order to focus the millimetric waves, a dielectric lens (which is preferably integrated as a stepped lens into the radome of a surveillance antenna head) is provided in front of the millimetric-wave antennas.
TL;DR: A procedure to design a switched pattern antenna array is developed and demonstrated on a 16- and eight-element array to demonstrate the feasibility of the pattern switching concept for improved sidelobe performance.
Abstract: A procedure to design a switched pattern antenna array is developed and demonstrated on a 16- and eight-element array. The variable spacing of elements allows us to reduce the number of switchable elements to a minimum and to reduce the sidelobes of the effective pattern. Based on this design we have built and tested an eight-element prototype array. Measurements demonstrate the feasibility of the pattern switching concept for improved sidelobe performance.
25 Nov 1987
TL;DR: In this article, an optical system is described which provides a set of microwave signals to be applied to elements in a phased array employing solid state TR modules for both transmission and reception.
Abstract: An optical system is described which provides a set of microwave signals to be applied to elements in a phased array employing solid state TR modules. The set is globally controlled by two sinusoids to permit beam formation in the 2D angle space of the antenna for both transmission and reception. Experimental results are shown. The basic conceptual design is described in terms of lightwave components which is extended to monopulse beam formation and wideband waveform beam steering which counteracts the intrinsic dispersion of arrays.
15 Jun 1987
TL;DR: In this paper, a monostatic millimeter-wave radar Ntenna by integrating transmit, receive, phase shift, control and other functions into a single monolithic integrated circuit, and then assembling them in large numbers with antenna elements to form electronically-controlled phased arrays, leads to such a large concentration of heat generating components in such a small volume that cooling the assembly for safe reliable operation appears to be impossible if the transmit power exceeds some modest limit.
Abstract: Building a monostatic millimeter-wave radar ntenna by integrating transmit, receive, phase shift, control and other functions into a single monolithic integrated circuit, and then assembling them in large numbers with antenna elements to form electronically-controlled phased arrays, leads to such a large concentration of heat generating components in such a small volume that cooling the assembly for safe reliable operation appears to be impossible if the transmit power exceeds some modest limit.
15 Jun 1987
TL;DR: This paper proposes a new array antenna with a reflector that is composed of active elements with equal phase shifts and is spatially fed by a multibeam horn, and experimentally verified with a 19-element array antenna.
Abstract: A multibeam antenna allows a large communication capacity and is suitable for satellite-borne instrument. The present paper proposes a new array antenna with a reflector. The array is composed of active elements with equal phase shifts and is spatially fed by a multibeam horn. The array emits a spherical wave to a reflector. Its compact size fits satellite-borne instrument and at the same time a good quality is expected for the gain and the sidelobe properties. Optimal values of the parameters are theoretically determined for S band operation with array construction, array position, number of elements, and apertures, and the properties of this antenna are derived. It is theoretically predicted that the space feed gives rise to a uniform power distribution over the elements. This prediction has been experimentally verified with a 19-element array antenna. High power repeaters are no longer required and an arbitrary power distribution over the elements is readily realized.
09 Nov 1987
TL;DR: The system, consisting of a 2-element array with one user and one jamming signal, has been shown to achieve almost 25 dB of nulls in less than 3 microseconds for signals in the L-band.
Abstract: This paper reports on the work in progress at Lockheed Electronics Company in the area of acousto-optic processors for adaptive antenna arrays. The work encompasses both theoretical and hardware implementation of such processors. For demonstration of the basic concept, an optical/electronic brassboard has been built and tested. The system, consisting of a 2-element array with one user and one jamming signal, has been shown to achieve almost 25 dB of nulls in less than 3 microseconds for signals in the L-band.
TL;DR: In this article, the fundamental characteristics of an antenna, namely radiation pattern, directivity, gain, and polarization, are defined and discussed in relation to the dipole and the conical spiral, both low-gain antennas.
Abstract: Antennas for three-axis stabilized spacecraft that are in circular orbit and must communicate with one or more earth-based antennas are discussed. Antennas for many military satellites of a classified nature and for NASA's deep space probes are excluded. The fundamental characteristics of an antenna, namely radiation pattern, directivity, gain, and polarization, are defined. These properties are discussed in relation to the dipole and the conical spiral, both low-gain antennas. A consideration of the nature of the transmission of information over long, free space paths reveals that high-gain antennas are required when the information data rate is high, as in color TV transmissions. Some typical satellite antennas are briefly described, including those of the Global Positioning System's Navstar and the Telecommunications Data Relay satellites.
15 Jun 1987
TL;DR: The design of a hybrid C-band and K-band communications system for use in space has been described in this article, which was designed to require minimum satellite surface without using deployable components but still providing maximum gain, cross polarization isolation, suitable pattern coverage and high reliability.
Abstract: The design of a hybrid C-band and K-band communications system for use in space has been described. The .systems were designed to require minimum satellite surface without using deployable components but still providing maximum gain, cross polarization isolation, suitable pattern coverage and high reliability. The antenna systems have been successfully launched by space shuttle and the ARIANE rocket. Expectation for continued use is high.
15 Jun 1987
01 May 1987
TL;DR: In this article, an expression for the gain of a curtain array antenna over a perfectly conducting, flat Earth with no mutual impedance between elements is derived by a FORTRAN computer subroutine created to calculate the expression.
Abstract: An expression for the gain of a curtain array antenna over a perfectly conducting, flat Earth with no mutual impedance between elements is derived in this report A FORTRAN computer subroutine created to calculate the expression is described here This subroutine considers interelement spacing and length of the individual elements, the spacing between the radiators and the reflecting screen behind the radiators, the antenna design and operating frequencies, and the number of elements in the array
15 Jun 1987
TL;DR: In this paper, the authors evaluate the focal region of dual-reflector antennas and derive the excitation CXP efficients of the array feed by conjugate matching, which is then used to determine the array characteristics.
Abstract: A. Introduction. In low-sidelobe beam scanning applications of reflector antennas an array of feeds is normally enployed as the excitation source. The fundamental design problem is then to determine the array characteristics which corresponds t o a p r e scribed radiation pttern. This papr addresses this problan through the evaluation of the focal region f ie lds of dual-reflector antennas fran which, by conjugate matching, the excitation CXP efficients of the array feed are abtained.
15 Jun 1987