Showing papers on "Antenna array published in 1980"

Method and apparatus for processing spread spectrum signals

Abstract: In order to avoid the need for individual RF down-converters in each channel of a spread spectrum adaptive array receiver, means are provided for frequency offsetting the received spread spectrum signals in each antenna array element from spread spectrum signals in the other array elements. The frequency offset signals are summed to form a broadband composite signal of spread spectrum signals separated from one another by the frequency offsets. After summing, the spread spectrum signals in the composite broadband signal are despread to form a narrowband composite signal having narrowband signals separated by the frequency offset. Since the resulting composite despread signal has a relatively narrow bandwidth, it can be passed through a single common receiver. Accordingly, the input to an adaptive array processor from the receiver is a low frequency relatively narrow signal. This significantly reduces the tracking requirements of the adaptive array processor and allows for significant reduction in costs, weight and size of the adaptive array processor in addition to the elimination of unnecessary RF down-converters.

New wideband microstrip antenna using log-periodic technique

Abstract: A novel wideband microstrip antenna using a series-fed linear array of patch resonators in a log-periodic arrangement is described. A 9-element example gives good input v.s.w.r. and radiation control over a 30% bandwidth with better than 70% efficiency. The new array configuration gives wider bandwidth than single-layer or stacked microstrip patches combined with better efficiency than patches on lossy substrates or microstrip spirals.

Antenna array with adaptive sidelobe cancellation

Abstract: A beam space adaptive array antenna system utilizing a two-stage Butler matrix configuration is disclosed. The individual elements of one subarray are input to the respective ports of a first-stage Butler matrix and the remaining summed subarray elements are input to a second-stage Butler matrix. The zero order output of the first stage Butler matrix is fed to the input of the second stage Butler matrix.

An Adaptive Antenna for Rejection of Wideband Interference

Abstract: A modification to the adaptive array under the directional constraint [1] is proposed to improve its performance of rejecting wideband interference. By analogy to the pattern synthesis of an antenna array which produces a flat null in its radiation pattern, an additional quantity that corresponds to the derivative of the pattern is generated and combined with the standard feedback quantity to control the weights of the array. This composite system is tested by computer simulation experiments and the following points are demonstrated in contrast to the conventional, simple system: 1) faster adaptation against wideband interference, 2) remarkable improvement of the signal-to-noise ratio of the output, i. e., very small fluctuation.

Direction finding and ranging system for locating scanning emitters

Abstract: Three or more receiving antennas are arrayed in a triangle that in turn is oriented in the same generally defined plane as a scanning RF beam emitted by a distant source of radar or other RF transmission, which is to be located. Signals received by the arrayed antennas are coupled to signal processing circuitry which measures the various time intervals (or differentials) that it takes for the source transmission to sweep through the angles subtended, at the source, by different spaced-apart pairs of the arrayed antennas. From these measured time differentials and the known geometry of the arrayed antennas and a measured scan rate of the transmission source, the signal processing circuitry determines the angle of arrival of the transmission with respect to the array, and then further combines the thusly determined angle of arrival with a signal representing the measured time differential associated with one selected pair of the arrayed antennas, to yield a signal proportional to the distance (range) of the source from the antenna array.

Non-dissipative load termination for travelling wave array antenna

Abstract: This specification discloses a nondissipative load termination for a traveling wave antenna array whereby energy incident at the end of the antenna array is applied directly to the main beam of the array with the same polarization as the main beam so that the gain of the antenna is improved.

Resolution of coherent sources incident on a circular antenna array

Abstract: A method of processing voltages received on a circular antenna array which calculates the number, azimuths, and relative strengths of coherent sources is described. The method can be extended to any array geometry where inverse filtering (or deconvolution by the inverse beamspreading function) can be applied. In particular, it can be applied directly to a linear array geometry. In the analysis, the effects of mutual coupling between elements hasn ot been considered.

Endfire antenna arrays excited by proximity coupling to single wire transmission line

Abstract: A lightweight, efficient, microwave power transmitting antenna is disclosed, suitable for use in a space borne transmitter for beaming solar generated electrical power down to earth based receiving antennas. The space borne antenna structure is formed by modules that are structurally integrated into a multimodule antenna array. Each module comprises a rectangular framework of limited depth having rigid sides circumscribing a generally open region in which a plurality of spaced parallel single wire Goubau transmission lines are strung to create a "see-through" harp-like configuration. A Klystron powered feed wave guide is disposed as one structural side of the module for exciting standing electromagnetic waves on the plurality of Goubau lines. Printed circuit Yagi endfire radiators are supported on dielectric webs disposed in juxtaposition with the Goubau lines for being synchronously excited by the standing waves on such lines. The modular, open framework construction together with the use of single wire Goubau transmission lines for exciting the web mounted Yagi radiators, forms an exceptionally lightweight structure which when disassembled can be consolidated in a high density package for being launched into orbit, and then subsequently assembled in space.

A Microstrip Antenna for Medical Applications

Abstract: A ring-type microstrip antenna as a potential microwave power radiator for biomedical applications is discussed. Heating pattern measurements show that the structure is capable of providing relatively uniform heating over a cylindrical volume.

Wire grid microstrip antenna

Abstract: An antenna, adapted to be used as a monopulse antenna in a guided missile, is shown to comprise four separate microstrip circuits in different quadrants of a circular microstrip arrangement, each one of such microstrip circuits being made up of an array of contiguous rectangular meshes with the widths of the shorter sides of such meshes being varied to provide an amplitude taper

Omnidirectional side lobe sum and difference beam forming network for a multielement antenna array and method for determining the weights thereof

Abstract: A beam forming network for a circular antenna array having N groups of N radiating elements which is coupled to the antenna array through N-1 phase shifters and an NxN Butler matrix, said beam forming network comprising: a power divider network (102, 104,106); a sum pattern generating network (108); a difference pattern generating network (110); and a sum-difference combiner network (112,114,116, 118); the various networks are used either alone or in simultaneous combination to provide sum and difference antenna patterns respectively having an omnidirectional side lobe.

Disk-type ultra-high frequency antenna array with its supply device and the application thereof to angular deviation measurement radars

Abstract: A disk-type antenna array is described with its supply device. The antenna is supplied with an electromagnetic wave having circular polarization in the TE 11 mode delivered through a particular coupling means.

Method for siting cosine-squared antennas and antenna array obtained thereby

Abstract: A method for optimally siting cosine-squared antennas in an array is taught, along with the array which is produced by use of the array. The array in question utilizes a dense hexagonal cellular grid, and each individual antenna is assigned a frequency group on which the antenna operates. The cells are ordered in such a fashion as to keep co-channel interference to a minimum.

Target angle measurement of radar

Abstract: PURPOSE:To restrain the reception of the unnecessary reflected waves from a sea surface by controlling the phase of an antenna array elements in accordance with the transmission and reception thereby to form a preset beam pattern. CONSTITUTION:The phase shift of a phase shifter 2 corresponding to the antenna elements arranged vertically in an array is controlled through a beam control circuit 5 and a drive circuit 4. Then, the pattern transmitted from an antenna 1, which constitutes a single antenna of all the antenna elements, has a sufficiently small gain in the vicinity of the elevation of 0 degrees. Upon reception, the phase shifter 2 is so controlled that the beam pattern of each unit antenna formed by the plural antenna elements of each half wavelength of the radar waves for each time after the reception become equal. Then, the reception having the rear surface reflection restrained is performed by the transmitted pattern having little sea surface reflection is performed to measure the target angle in high accuracy.

Frequency agility technique for frequency scanned antenna

Abstract: In a serpentine feed structure for a frequency scanned antenna a switchingetwork is provided which allows the serpentine to be fed from either end on alternate or random scans. This variable transmission system significantly increases the frequency bandwidth that must be jammed by detrimental countermeasure systems. The feed switching network comprises first, second and third switching circulators coupled to receive radiant energy from a radar transmit-receive switch and selectively couple this energy to one or the other end of a serpentine feed structure for controlling the direction of electromagnetic radiation energy coupled through the serpentine structure. The serpentine feed structure supplies radiant energy to an antenna array of a frequency scanned antenna for controlling the sector scanning of the antenna. Reversing the direction of energy flow through the serpentine causes a change in the particular frequencies scanning a given sector of the scan. This allows two separated frequencies to be alternately used for directing a beam toward a particular direction thereby reducing the effects of countermeasure systems. Additionally, energy reflected from a target may be coupled back through the array and switching network to the radar transmit-receive circuitry.

Radiating element with parallel planes and its use in creating an antenna array

Abstract: Radiating element with parallel planes, operating in the microwave range, and transforming a spherical wave into a plane wave, consisting of at least two successive focusing systems (13 and 7) the first of which is illuminated by a source (8) delivering a spherical wave and the last of which delivers a plane wave at its output. The focusing systems consist of two elementary cheeses or pill- boxes coupled together by a slot (10) running throughout the length of a hyperbolic cylindrical reflecting base (11), apart from the last focusing system whose reflector (15) is parabolic cylindrical. Application to linear antenna-networks and to slab antennas.

Around-the-mast rotary coupler

Abstract: An annular rotary RF coupler for installation about a vertical support structure, particularly the mast of a ship. Two annular troughs are regularly divided in circumferential increments providing a cellular structure of individual waveguide cross-sections. A lower annulus remains fixed, the individual waveguide sections therein being fed from a power-divided, equal-phase, feed configuration. The oppositely facing upper annulus rotates with respect to the lower one about a common mechanical center of rotation of a mechanically rotating antenna system. Connection to the rotating waveguide sections may be through power combiner/divider means, or individual subarrays may be discretely connected to one or more waveguide sections in the rotating annulus. For power tapering across an antenna array aperture, the waveguide section dimensions in the circumferential direction within the rotating annulus are appropriately tailored.

Simplified analytical procedure for four-element nonuniformly spaced arrays

Abstract: A simplified analytical procedure is suggested for the design of a four-element symmetrical uniformly excited nonuniformly spaced linear antenna array. The errors resulting from the simplification are shown to be negligible for sidelobes of practical significance.

Antenna array with impedance matching using mutual coupling

Abstract: A circularly polarized antenna has bays stacked at spacings of less than one wavelength in order to have a broadband SWR characteristic and to minimize radiation along a supporting mast axis Vertical stubs are used to increase the circularity of the horizontal pattern and to improve the axial ratio

Real-Time Holography With Microwaves And Millimeter Waves

Abstract: A new approach to real-time, long-wavelength holography is described. The method utilizes one wavelength for formation and another for reconstruction. The reconstruction is done with a millimeter wave lens illuminated by an antenna array operating at the shorter wave-lengths. The amplitude distribution from the array is a replica of the sampled microwave hologram. PIN-diode modulators control the reconstruction array. Experimental verification is given.

Multiple input antenna system

Abstract: CM-74608 IMPROVED MULTIPLE INPUT ANTENNA SYSTEM An improved antenna system is disclosed in which a single antenna array is simultaneously used in conjunction with several independent radio devices. Isolated and independent radio transmitters are coupled, without any signal cancellation, to each and every one of a plurality of isolated independent antenna elements by a combining network which maintains the isolation between each of the radio transmitters and each of the antenna elements. The combining network comprises an array of hybrid networks and creates a predetermined electrical phase difference between each signal received by an individual antenna element. The antenna elements form a single antenna array consisting of circularly disposed corner reflector antennas. Each reflector independently creates an individual radiation pattern and these patterns combine to form a single desired composite radiation pattern. By maintaining isolation between each of a number of radio transmitters, a plurality of these transmitters may be used simultaneously in conjunction with a single antenna array.

Active retrodirective arrays for SPS beam pointing

Abstract: The basic requirement of the SPS beam pointing system is that it deliver a certain amount of S-band (lambda = 12.5 cm) power to a 9.6 km diameter receiving rectenna on the ground. The power is transmitted from a 1.0 km diameter antenna array on the SPS, which is, for a rectenna at about plus or minus 40 deg. latitude, some 37.5x10 to the 6th power km distant. At the present time ARA's appear to be the best bet to realize this very stringent beam pointing requirement. An active retrodirective array (ARA) transmits a beam towards the apparent source of an illuminating signal called the pilot. The array produces, not merely reflects, RF power. Retrodirectivity is achieved by retransmitting from each element of the array a signal whose phase is the "conjugate" of that received by the element. Phase conjugate circuits and pointing errors in ARA's are described. Results obtained using a 2-element X-band ARA and an 8-element S-band ARA are included.

Synthesis of Arrays for Suppressing a Wide-Band Jammer

Abstract: This paper presents a design technique for a large antenna array to yield a pattern with low near-in sidelobes and a deep null in a specified direction The performance of the array under wide-band operation and its effectiveness in suppressing wide-band jamming are investigated Numerous transient patterns are plotted for various bandwidths and pulse-compression ratios It has been found that, with a wide, deep null steered in the direction of jamming and by slightly increasing the rise time of the matched filter, the array is capable of suppressing an "impulse" jammer