Showing papers on "Antenna array published in 1974"

Space oriented microwave power transmission system

Abstract: A combined active phased antenna array for satellite solar power station systems includes a plurality of directly coupled microwave energy generators for conversion of the dc power generated by a system of solar energy conversion means to microwave energy. The microwave power is transmitted through space in a narrow beam for capture and rectification at the receiving point. The microwave energy generator devices embodied in the invention are of the crossed field amplifier type having a very high efficiency and extremely long life through the use of a cold cathode secondary emitting electron source. The microwave generated power is transmitted through slotted waveguide radiator arrays with the phase of the energy monitored and corrections are made by phase shifting devices where necessary.

Antenna arrays of internally phased elements

Abstract: An antenna array which receives radio waves and reradiates them in a controllable direction. Direction of the reradiated wave is controlled by controlling the phase relationship between waves reradiated from individual antennas which are elements of the complete array assembly. Phase control of the individual element antennas is effected by altering the relative phase between the received wave and the reradiated wave for each individual element antenna. The phase of the received signal is controlled at terminals on the individual antennas at which that received signal arrives. The phase-altered signal is reapplied to those terminals to serve as an excitation signal for the antenna for causing a reradiated wave to be emitted. The difference between the direction of the reradiated wave and the direction of the received wave is controlled by diode switches or by varactor diodes (or by both) which can be mounted integrally with the individual element antennas of the array assembly.

A solution of the general nonuniformly spaced antenna array

Abstract: An effort is made to give a solution of the general non-unifomly spaced antenna array by the orthogonal method when the array factor f(ϕ, ϑ) is given.

Radar randome antenna with switchable R.F. transparency/reflectivity

Abstract: Control of the directivity, reflectivity, transparency and tuning of R.F. antenna array is accomplished by building antenna with short dipole segments with a switch between each two segments. The elements are properly connected to exhibit these electrical characteristics by remotely controlling the closing and opening of selected switches. The means for controlling the switches is isolated from the R.F. working frequencies of the antenna.STATEMENT OF GOVERNMENT INTEREST

Signal source position-determining process

Abstract: A signal source position is determined using an angle-measuring, interferter system employing a longitudinal antenna array having a baseline length greater than the signal wavelength. The long, multi-lambda (nλ) baseline produces ambiguous phase measurement ( ). Thus, the true angular position or bearing could correspond either to φ, or φ±360°, or φ±2.sup.. 360°, -φ±(n-1)360°, or φ-n .360°. Ambiguities are resolved by the longitudinal array angular motion relative to the signal source and by phase tracking the signal during the relative movement. To determine the true signal position, (2n) different software solutions for signal position are set up to process the 2n different angular data produced by each phase measurement (φ). The "Lobe Tracking" procedure (there are n-number of data lobes in a (nλ) array) which is achieved by phase tracking provides the means of matching the n-different angular data produced by the phase measurement (φ) to the n-different solutions set-up. From the n-different solutions set-up for signal position, only one will converge to the true signal position and the rest will diverge. The convergence or divergence depends on matching the vehicles position translation to the angular position change relative to the signal source. The solution elimination process is set up by certain solution conveyance criteria. Also the elimination process is enhanced by solution rejection based on unacceptability of angular data or lobe. Since lobe tracking matches the angular data produced by the measurement to the solution, unacceptability of data constitutes rejection of the solution.

Co-channel interference suppression apparatus

Abstract: The present invention refers to apparatus intended to suppress multiple co-channel interference and reflections from desired stations. The outputs of a two antenna array, which has been directed at the desired station, are fed to a sum-and-difference hybrid. The outputs of the hybrid are adjusted in amplitude and phase and combined to null the interference signal. The phase shift required for nulling is either ±90°. The sign is determined by the side of the array on which the interference source is located. The phase relation is true regardless of the exact location of the interference, requiring only a single adjustment in amplitude to null the source of interference. By adding a third antenna to the array and a phase detector to the system, a signal representing the direction of the source of interference is produced and is used to introduce either a ±90° phase shift and to set the required attenuation automatically cancelling the interference signal even if the interference signal source moves as effectively occurs with the resultant of multiple sources of interference.

Collinear dipole array with reflector

Abstract: This invention comprises an antenna array of collinear, end-fed dipoles spaced substantially less than one-quarter wavelength from the reflector. Consecutive dipoles are energized through phasing loops with the end dipole energized by a coaxial feeder or by one of the two output ports of a balun. A radome with a helically wound resistance heating wire is used to protect the array from the elements. Means comprising the addition of small auxiliary radiators at one of the ends of each dipoles are provided to reduce radiation polarized perpendicular to the axis of the array.

Radio direction finding apparatus

Abstract: A circle arc array of element antennas is capable of receiving at all times radio signals from a source located anywhere in a wide angle or complete circle of azimuth directions, the direction of arrival of a received signal being indicated by radio receiving equipment. The source signal received by each element antenna is directed into two or three channels having different phase delays. The output signals from the first channels of all of the element antennas are combined and connected to a first radio receiver, the phase delays in the first channels being equal for all of the element antennas. The output signals from the second channels of all of the element antennas are combined and connected to the input of a second receiver, the phase delays in the second channels all being different from each other in a uniform phase progression. The phase progression corresponds to a clockwise azimuthal progression of the associated element antennas. The phase difference between the signals of the first and second radio receivers indicates the azimuth direction from which the source radio wave is arriving at the antenna array. If desired, counterclockwise-phased output signals from third channels of all of the element antennas may be employed for a redundant indication of azimuth direction of arrival, to reduce errors. Antenna elements may be arranged in the same circular arc array fashion, with the plane of the elements being vertical, in order to measure elevation direction of arrival.

Antenna array for aircraft guidance system

Abstract: The antenna array preferably consists of a plurality of slotted wave guide microwave signal radiating elements positioned to directly radiate separate beams of microwave energy at different azimuth angles to a common horizontally aligned cylinder sector reflector, the radiating elements being operable to primarily determine the direction and shape of the resultant reflected beams in azimuth and the reflector being operable to primarily determine the elevation patterns of the resultant reflected beams.

Electronically scanned TACAN antenna

Abstract: This paper describes the principles of operation of the Tactical Air Navigation (TACAN) antenna system and compares the performance characteristics of the mechanically rotated with a proposed electronically scanned system. An analysis is provided of the various factors involved in the design of an electronically scanned TACAN antenna. The discussions in this paper serve as an introduction to a paper in this issue which describes the design, fabrication, test, and evaluation of one example of an experimental model of an electronically scanned cylindrical TACAN antenna array [1].

Optimization of array performance subject to multiple power pattern constraints

Abstract: Many antenna array performance indices can be expressed as ratios of Hermitian quadratic forms in the element excitation coefficients. A method is presented for the optimization of such performance indices with respect to the excitation coefficients and subject to multiple nonzero constraints on the array power pattern. The optimum excitation vector is shown to satisfy a characteristic equation with quadratic constraints. The solution of this equation is reduced to another quadratic form optimization problem for which solution techniques exist. Intended for applications involving power pattern constraints, the method of this communication avoids the penalty generally incurred by the alternative approach of arbitrarily specifying radiation pattern phase and using existing results on performance index optimization with radiation pattern constraints. As an example the method is applied to the problem of reducing the sidelobes of a circular array under a constraint on the main-lobe beamwidth of the power pattern.

Phase shifter for linearly polarized antenna array

Abstract: There is disclosed herein a linearly polarized mat-strip phased antenna array wherein the antenna array is phased by incorporating in series relationship one or more mat-strip loaded line type phase shifters in the mat-strip power division distribution network for the mat-strip dipole elements and/or a combined mat-strip dipole element and phase inverter. Two embodiments are illustrated.

Radio direction finder with means for reducing sensitivity to multipath propogation errors

Abstract: A surface based direction finder for determining the direction of radiations from a remote station (aircraft for example), using a plural element linear or circular receiving antenna array The arriving energy phases are measured in at least one element group with two element pairs, (for example) the elements of each pair being equally spaced and aligned so that a line joining elements of even ordinal number is parallel to the line joining the elements with odd ordinal numbers The amplitudes (m1, m2, m3 and m4) and the phases (α1, α2) of the rf signal picked up by each element are measured separately and the phase β of the desired wave is determined by computer solution of the typical equation derived from the law of consines; m1sup2 + m2sup2 -2m1 m2 cos (α1 - β)= m3sup2 + m4sup2 - 2m3m4 cos (α2- β) Other configurations employing three elements in line and elements in a circle are also described and the corresponding cosine law equations given

Broadband beacon antenna system

Abstract: Tactical radio navigation systems provide bearing information to an interrogating aircraft in response to pairs of interrogation pulses received at a beacon transponder, the system also provides distance measuring and identification information. To provide the required bearing information, pulses radiated from the central antenna array are modulated at a 15 Hz frequency and by 135 Hz frequency, by parasitic elements rotating around a stationary central array. Broadband operation of the system is provided by a distribution pattern of the 135 Hz parasitic elements mounted radially from the central antenna array on a dielectric disc. Nine groups of radially displaced 135 Hz elements are circumferentially arranged around the dielectric disc and each element of a group is tailored to a particular frequency band in the frequency spectrum allotted to radio navigation systems.

Linear antenna arrays with broadened nulls

Abstract: It is shown that a null in the radiation pattern of a linear antenna array can be broadened into a null sector by the use of suitable forms of amplitude taper. For a uniformly spaced array, binomial taper coefficients with alternate positive and negative signs produce a maximally-flat null broadening. Null slewing by means of phase taper and null broadening by means of amplitude taper can be regarded as two independent operations.

Endfire commutated antenna array

Abstract: A commutated linear antenna array of general utility in simulated Doppler guidance systems. The array operates as an entire array of n elements in which n-1 elements are successively excited in accordance with a commutation (scan) program. As each element is excited, the immediately adjacent element to the rear (opposite the radiation direction) has a base loading circuit activated such that it acts as a short circuit and therefore the element itself acts as a reflector in cooperation with the excited element. At the same time all other elements are provided with base loadings so that they are open circuited and appear transparent for radiation purposes. A dummy parasite reflector is provided behind the first element of the array (not commutated) and has a fixed short-circuit loading at its base. Thus the radiation pattern is substantially the same in the forward direction during the successive exitation of each of the commutated elements.

Erection and retraction mechanism for a foldable antenna and its mast

Abstract: There is disclosed herein a mechanism to erect and retract a foldable antenna and its mast for use in a submarine antenna buoy. A first sheave is fixed to the mast and buoy base in a rotating relation to the mast and in a non-rotating relation to the buoy base and a second sheave is carried as a rotational component upon the antenna mast but affixed as non-rotating with respect to the antenna array. The first sheave is made twice the diameter of the second sheave and a band interconnects the peripheries of the sheaves. A drive mechanism is provided to drive the antenna mast such that, when the antenna mast is rotated 90* clockwise, the second sheave would then be rotated 180* counterclockwise about its axis to unfold the antenna so as to be vertical with respect to the buoy base and in line with the mast. A similar band interconnecting the peripheries sheaves opposite the first periphery connections would cause a positive reversal of this process. With this mechanism, a positive erection and positive retraction can be obtained through driven members under efficient tensile loading. A cable, a chain, and a toothed belt can be used instead of the bands and drums and sprockets can be used instead of the sheaves.

A theory of antenna array conformal to surfaces of revolution

Abstract: For a conformal array of nonparallel radiators the classical array theory fails to offer a convenient way for calculating the array pattern and its cross-polarized counterpart. This study shows that under a wide range of conditions, these patterns can be simply obtained from the array space factor by partial differentiation. The scalar space factor of an array, therefore, can be considered as a generating function for the array patterns for both the principal and the cross-polarized fields in a vector form. To illustrate the theory, arc arrays of uniformly spaced dipoles and slots are treated. The analysis is extended to the case of conical arrays.

Optimum Processing of Antenna Array Signals in the Presence of Discrete Noise Sources

Abstract: Previous formulations of the signal-to-noise power ratio (SNR) of an antenna array are shown to fail when a number of monochromatic discrete noise sources smaller than the number of elements in the array are considered in the formulation. It is shown how the performance of the array with respect to SNR may, nevertheless, be optimized using a gain maximization procedure The derivation of the theory is carried out in terms of network parameters defined at the input terminals of the array elements. Mutual coupling effects are taken into account. Numerical and experimental results are also presented to illustrate how this technique can be physically implemented.

Method of transmitting glide slope navigation signals for aircraft

Abstract: A multiple element antenna array provides a separate beam of carrier signal from each element in a pattern of beams spaced at different angles above the horizon. The array is adjusted upwardly to avoid obstructions on the horizon, and a program of modulation is applied to the separate beams to define the desired glide slope path while compensating for the mechanical upward adjustment of the array.

Linear antenna arrays with broadened nulls

Abstract: The `small-sine? taper has recently been proposed as a method of broadening a null in the radiation pattern of a linear array, and this is discussed. The nulls are compared with the broad null sectors obtained from a Dolph-Chebuy?shev array.

Beacon Target Enhancement.

Abstract: : The report describes theoretical and experimental work directed toward development of a low-cost solid-state target-enhancement device The purpose of the device is to increase the detectability, at 2700 to 2900 MHz, of light aircraft by existing airport surveillance radars at distances of 30 nmi with a detection probability of 08 The basic concept studied was that of a retrodirective antenna array, having a two-way gain of about 20 dB, supplemented by negative-resistance, inverted-common-collector-connected transistor amplifiers terminating each array element and having about 11 dB of reflection gain (Modified author abstract)

Evaluation of Two Dimensional HF Adaptive Antenna Arrays

Abstract: : The primary task was to modify an existing HF phased array facility in Hudson, Colorado so that data could be collected on a large two-dimensional array in a format suitable for use for adaptive processing. The principal modifications included the construction of a 32 element cross array of vertical monopoles and the addition of quadrature outputs to the existing 32-channel receiver and data acquisition system. Additional tasks included the development of software (for controlling the data collection system, for processing and displaying the field data, for producing simulated field tapes for specific array geometries and model environments), data collection under a variety of conditions, and analysis (numerical simulations to guide the design of the antenna array and data reduction to evaluate the performance improvement obtained through adaptive processing).

Radiation Patterns of a Cardioid Shaped Antenna Array

Abstract: The paper deals with an investigation of the horizontal and the vertical patterns due to a plane array of isotropic radiators arranged along a cardioid Following a brief theoretical analysis, seve

A Matrix Feed System for a Cylindrical Antenna Array

Abstract: The cylindrical matrix is a reciprocal corporate microwave network connected between a selector switch and an antenna ring array. The matrix divides and controls the amplitude and phase of the input power and feeds it to a sector of the array. The active array sector forms a highly directive beam normal to the array sector.

Application of adaptive arrays to communications

Abstract: The phase and amplitude weighting of the waveform received at each element of an antenna array can be adaptively controlled in real time to optimize the antenna pattern for a variety of communication links. In this paper we present the results of experiments conducted with an SHF self-phasing array and with an adaptive UHF null-forming array.