Showing papers on "Phased array published in 1970"

Circularly polarized phased array antenna element

Abstract: A phased array antenna element which provides good circular polarization over a broad sector of coverage in an array environment has been designed and evaluated. The concept is the superposition of complementary antennas, the dipole, and the slot, to achieve equal E - and H -plane patterns in the array environment. This element, when evaluated in a large test array, demonstrated an ellipticity of less than \pm2.0 dB over a coverage of \pm60 degrees. By proper control of the excitation of the two isolated antennas any desired polarization can be achieved.

Sequential methods in radar detection

Abstract: Certain sequential tests of statistical hypotheses known as sequential probability ratio tests (SPRT) possess an optimum property that they can accelerate, on the average, the termination of the test or alternately execute the test in the same time with less error, or with the same error but on less distinguishable hypotheses than a fixed sample-size test These properties are of practical importance when applied to the radar problem, but in the application of sequential methods to radar surveillance some modification of an SPRT is frequently necessary In particular, design problems relating to phased array radars are considered This paper reviews the problem of angle search constraints, existence of multiple resolution elements in range and velocity, possibility of a flexible allocation of pulses, and fluctuations of radar cross sections of targets Representative numerical results are included to indicate what performance can be expected with the use of sequential methods An attempt is made to present an integrated theoretical and practical picture Key references are listed

Randomly phase coded antenna technique for search radar

Abstract: A search radar having an array antenna wherein the individual antenna array elements are energized by random phases having a beam forming matrix to sense direction dependent phase codes in the antenna far field, which phase codes are in turn used in correlation processing in the radar receiver for the purpose of obtaining angular resolution and radar sensitivity.

Phased array beam steering control with phase misalignment correction

Abstract: A system for remotely controlling the phase of active antenna elements in a phased array that has the capability of correcting the inherent phase misalignment of each individual antenna element within the array. Beam azimuth and elevation signals are fed into an appropriate arithmetic unit by a radar signal processor. Roll, yaw and pitch signals are fed into the same arithmetic unit by an inertial navigation system. The arithmetic unit, using the information from the inertial navigation system and the radar signal processor, computes the phase shift required for each individual antenna element in order to point the radar beam in the desired direction. To compensate for inherent phase alignment in the system, an antennule position and alignment store feeds a predetermined alignment factor for each antennule into the arithmetic unit. The arithmetic unit then adds or subtracts the alignment factors from the respective computed phase angles. All the calculated phase angles are then sent to the control circuitry of the antenna array. A Csc2 beam phase shift store provides for generation of a Csc2 beam at the array.

An X-band Reciprocal Latching Faraday Rotator Phase Shifter

Abstract: Industry has given considerable attention to the development of low-cost phase shifters to be used as beam steering elements in phased array RADARs. Latching reciprocal ferrite phase shifters have received special attention because of the following considerations: (1) they can handle relatively high peak and average power levels, (2) they require no bias to maintain a phase setting, and (3) their reciprocal nature allows transmitting and receiving functions to occur without resetting the array. This paper presents a technique for obtaining a low loss X-band reciprocal latching ferrite phase shifter. The phase shifter is described by first considering the propagation constant of the circularly-polarized phase shift section and then discussing the nonreciprocal circular polarizers which are necessary to obtain reciprocal phase shift. The theoretical and experimental results of the phase shifter are then presented.

Phased array laser source

Abstract: This invention is directed to an electronically scanned laser array. It utilizes a phase-locking laser, an array of variable phase shifters, an array of semiconductor lasers and a control computer. The output of the phase-locking laser is optically coupled, by means of reflective or transmission optics, to the phase shifters which are controlled in a predetermined pattern by the computer. The phase shifters are optically coupled to the array and cause uniform shifts in the phase front of the arrayed lasers to provide a scanning effect of the output beam.

Satellite communications system

Abstract: A ground-air communications system is disclosed that includes ground station processors, aircraft, and satellite borne repeaters. Satellite weight and power economies are achieved by scanning with repeater antennas. The preferred embodiment utilizes a phased array antenna having its antenna elements and amplifiers disposed in the satellite borne repeater and its phase shifting and modulating components disposed in the ground station processor. Phase shifted modulated carrier waves are translated in frequency prior to transmission from the ground station processor and are retranslated to their original frequencies by the repeater. Means are provided to lock transmitted and received carrier waves in phase and frequency.

Step-scanned circular-array antenna

Abstract: A circular-array radar antenna designed for operation over a 20-percent bandwidth has demonstrated improved performance over that of linear arrays. A major advantage is that the beam pointing angle is independent of frequency. The array developed and tested provides 128 beam positions with a beam crossover of about -2 dB, a half-power beamwidth on the order of 4 or 5 degrees, and a sidelobe level of -25 dB. Step increments of one element per beam position allow practical implementation of step scanning, i.e., simple commutation of the current distribution. Two approaches are possible for feeding and scanning the ring array: 1) a vector-transfer system involving 3-bit phase and amplitude boards which are capable of amplitude attenuation (VT scan) and 2) a lens feed system employing an R-2R parallel-plate region, with the spacing between the plates less than 1/2 a free-space wavelength, so that only the electric-field component perpendicular to the plates is propagated. Energy is launched and extracted from the lens by means of monopoles mounted 1/4 wavelength in front of the circumferential ground plane enclosing the lens. Computations involved in determining current distribution are based on [1] and [2].

Acoustic holography with crossed linear arrays

Abstract: This paper is an analysis of how acoustic (or microwave) holography can be applied to large masses, such as natural bodies of water or the earth, by means of a linear array of microphones and by scanning with one or more transmitters to produce holographic phase shifts. This type of hologram, in which the phased array has a conical antenna pattern, is shown to be superior to the area hologram for computing images in the near field. Computer simulations are given of virtual holograms and image reconstructions for specular and diffuse reflectors; simulations are also made for the case of pulse holography, which yields geniune three-dimensional images with reduced highlight distortions.

Phase control circuits using frequency multiplication for phased array antennas

Abstract: The disclosure describes a phase control coupling circuit for use with a phased array antenna. The coupling circuit includes a combining circuit which is coupled to a transmission line, a frequency multiplier circuit which is coupled to the combining circuit, and a recombining circuit which is coupled between the frequency multiplier circuit and phased array antenna elements. In a ''''doubler'''' embodiment, the frequency multiplier circuit comprises frequency doublers and the combining and recombining circuits comprise four-port hybrid power dividers. In a generalized embodiment, the multiplier circuit comprises frequency multiplier elements which multiply to the Nth power, the combining circuit comprises four-port hybrid power dividers, and the recombining circuit comprises summing circuits. In a quadrupler embodiment, the multiplier circuit comprises frequency quadrupler elements, the combining circuit comprises four-port hybrid power dividers and the recombining circuit comprises two levels of four-port hybrid power dividers.

Sidelobe-reduction techniques for phased arrays using digital phase shifters

Abstract: Through the introduction of a new parameter the radiation pattern of a phased array using digital phase shifters for beam steering can be made periodic, and pattern considerations can be confined to a very narrow range of the scan angle. Arrays designed on the basis of a least mean-square pattern error are shown to require the smallest absolute values of a phase-index function. A systematic and easy-to-apply method is developed for reducing the peak sidelobes of nonreciprocal phased arrays by one-step phase adjustments in certain elements. The amount of possible sidelobe reduction depends on the scan angle and the size of phase-quantization steps. Typical examples for 4-bit phase shifters show that reductions in excess of 9 dB are possible for certain main-beam directions.

Method and apparatus for electronically controlling the pattern of a phased array antenna

Abstract: Method and apparatus for controlling the directional pattern of a phased array antenna in one, two or three dimensions and in which the phased array antenna comprises a plurality of individual radiators each of which has a phase shifter that may be adjusted by special resistance values fed by a controlling direct voltage. Phase controlling resistors are arranged analogous to the spacings of the radiators of the antenna array and to form voltage dividers such that the directional characteristic of the antenna array may be adjusted by selectively connecting resistors to the phase shifting network. Means are also provided for tracking a signal as, for example, a satellite and to eliminate jamming signals.

Phased array antenna

Abstract: A phased-array radar antenna system has a scan pattern which is pivotal about the center of the array. The scan pattern is directed from a common set of scan-control circuitry which consists primarily of digital counters and logic whose output describe the settings of ON-OFF ferrite phase shifters for the elements on one side of the array. The one''s complements of these outputs are used to control the settings for the other one-half of the array, without need for an extra least bit. Each phase shifter consists of four bits. When all four bits are in their ON state, a phase shift of 360* is obtained. The minimum or increment of phase shift is 24*.

Electronically scanned antenna array

Abstract: A phased array antenna system in which the phase of successive radiating elements is produced by a series of injection locked oscillators each driven by or locked to the signal fed to the preceding elements. Since the phase of an injection locked oscillator depends upon the difference between its natural frequency and its injected frequency, the array may be scanned either by varying the injected frequency or the natural frequency. IMPATT diode oscillators are preferred because of the ease with which they can be injection locked and/or varied in frequency.

A class of phase-interpolation circuits for scanning phased arrays

Abstract: A class of circuits is described that can be used with a phased-array antenna in order to allow a given array feed system to provide phase control for a phased array with many more elements Alternatively, certain variations of these circuits can be used alone to provide phase control for small arrays while using only a single phase shifter for each direction of scan

Wide-frequency-band radar array antenna system with suppressed grating lobes

Abstract: When array antennas are used for wide-frequency operation a difficulty with grating lobes is encountered at the upper frequency end of the operating band. This paper points out that the use of arrays for transmission and reception with different interelement spacings can be used to extend the operating frequency band in a radar system. The principle of transmitting-receiving arrays with different illuminations was used by Mattingly [2] to lower the sidelobe level of a radar array antenna. Birge [3] used it to reduce the number of elements in an array while preserving the resolution. The same principle is used in this paper to extend the operating frequency bandwidth of a radar antenna system. Relationships for an optimized radar array antenna system are derived. The criterion for optimization is the maximum bandwidth with a given total number of elements. It is shown that in an optimized system the number of elements in one array antenna is one greater than in the other, and the ratio of interelement spacings is inversely proportional to the square of the number of elements in the respective arrays. Based on these conditions, a function k is computed and tabulated. This function determines the number of grating lobes permissible in the specified angular sector, without overlap, as a function of the number of elements in the two arrays. An application to a high frequency (HF) ionospheric radar antenna system, now under construction, is used as an illustration of the principles outlined in the paper.

Process for the automatic tracking of the directional beam of a phased array antenna

Abstract: A device for automatic tracking of the directional beam of a phased array antenna which includes a plurality of modules arranged in rows and columns. A part of the output voltages of the modules are coupled together to develop signals which are indicative of either the even numbered or odd numbered rows and columns of modules. The output signals are coupled to phase discriminators which develop positive or negative voltages in dependence on the sign of the angle of incidence of the arriving signal. The control voltage is then used in a closed regulating circuit to control delay lines associated with each of the modules.

Rf transmission through a plasma

Abstract: System for microwave transmission through a plasma. Radio communication through a layer of ionized gas is achieved by initially adjusting the impedance of the antenna system to match free space conditions, thereafter applying the radio signal to the antenna system, monitoring the standing wave ratio to detect a change in the ionization level of the ionized gas surrounding the antenna and thereafter adjusting the impedance of the antenna system to match that of the ionized gas. The ionization level is continuously monitored and the impedance continuously changed to match the constantly changing plasma conditions. Increased signal transmission is achieved by increasing the power of the signal up to a predetermined level and adjusting the impedance of the antenna system to match the changed ionized gas conditions which result from the increased input power. The increase in input power may be C.W. or may take the form of a series of pulses with subsequent monitoring of the changed ionization level delayed a predetermined time period after each pulse in order to monitor the effects of the increased pulsed power levels. Additional enhancement of signal transmission is achieved by adjusting the phased array of the antenna system in response to vehicle orientation data and remote tracking station signal data. The strength of the required power level may also be dependent upon this data.

Digital phase shift control for phased array antenna

Abstract: 1,204,342. Aerials. TEXAS INSTRUMENTS Inc. 30 Aug., 1967 [25 Nov., 1966], No. 39704/67. Heading H4A. In a phased aerial array, each element in a line thereof is fed from separate selectively variable delay means controlled by a counter having outputs of differing orders and corresponding in number to the number of elements in the line, and clock pulses are applied during a time gate proportional to the desired angle of radiation. The embodiment utilizes a twodimensional array of modules (14, Fig. 1) similar to the kind described in Specification 1,124,266. Each module includes a phase shifter 31, Fig. 4 having delay sections 100 . . . 103 in an R.F. path, and being selectively brought into circuit by corresponding switches 104 ... 107; the switches are energized from a counter 111 fed from the point y, Fig. 5. Azimuth and elevation time gate pulses are fed in at respective terminals 133, 134 to AND gates which are fed also at terminal 132 with clock pulses. Azimuth and elevation respective binary circuits 135, 136 (decsribed with reference to Fig. 6, not shown) are associated with switches to produce pulses into " quantizers " in the ratio 1, 2, 3 ... 28 (the aerial array being formed from a 28 by 28 matrix of elements), and the quantizers count down by a factor of 8. Each counter 111, Fig. 4 is associated with a different output of a NAND gate matrix 140, Fig. 5. Voltages on lines 146, 147 determine whether a beam is to be switched left or right of boresight (the magnitude of the beam deflection being determined by the width of the pulse applied to terminal 133) and similarly for beam deflection above and below boresight. A diagram of the switches and quantizers is described, Fig. 7 (not shown). A modification is described, Figs. 8, 9 and 10 (not shown).

ARRAY 1: Calculation of the Active Transmit Impedance for a Phased-Array Antenna of Lossless Elements (Computer Program Descriptions)

Abstract: This program computes, for a phased-array antenna of Iossless elements simulated in waveguide, the array-transmit impedance at the simuIated scan angle.

Phased array antenna for satellite

Abstract: A spin stabilized, earth orbitting satellite having a phased array antenna capable of radiating a plurality of steered electromagnetic beams to predetermined earth locations. The antenna array extends around the satellite and is made up of individual elements which are energized through semiconductor diode devices by electron beams. The electron beams are controlled by fields having the same frequency as the spin frequency of the satellite.

Time Scanned Array Radar Experiment.

Abstract: : The objective of the experimental test program was to demonstrate the feasibility of the Time Scanned Array Radar (TSAR) beam steering techniques by performig tests on a UHF LINEAR ARRAY MODEL. A principal motivation for this new phase steering or true time delay steering technique is cost reduction of array radar by removing all active beam steering components from the array element level. Experimental and theoretical results were obtained and compared. The result of this program is the conclusion that TSAR beam steering can be successfully implemented into a transmit or receive linear array to beam steer wideband or narrowband signals. A preliminary outline of a UHF planar array for future effort utilizing TSAR beam steering is included. (Author)

Very wide-band phased arrays

Abstract: A phased array is described that has been matched to operate over nearly an octave. A method of achieving very wide bandwidth with phased arrays integrated with transistors is suggested.

APPA: A Phased Array System Designed for Space Application

Abstract: Artificial pilot phased array (APPA) is a system designed for application as a multiple narrow-beam communication satellite. The design uses an adaptive array principle in a multiple-beam configuration. Two ground pilot signals are used to make beam steering independent of array attitude. Beam steering is accomplished without the requirement of user pilots by deriving array phase shifter settings from user locations. The system's principle of operation is persented along with a description of a laboratory model and a design application to a data relay satellite.

Phased array antennas for applications on spacecraft

Abstract: This is a survey paper wherein phased array antenna systems, now operating on spacecraft, are reviewed so as to reveal their basic techniques of beam formation, steering, and receive/transmit (transponder) functions. Laboratory developmental antennas, designed for ultimate spacecraft flight qualification, are assessed in terms of the needs of communications, earth resources instrumentation, and area surveillance.

Effects of changes in operating conditions on the phase of a frequency-locked Gunn oscillator in X band

Abstract: The frequency and phase-locking properties of solid-state microwave oscillators are of current interest in the contexts of phase control of oscillators, and the combining of a number of oscillators to achieve improved output power. A particular case of interest is that of the phased array antenna, in which the dual functions of power combination and beam steering are needed. In the latter case, it may be necessary to have control over the relative phases of a large number of oscillators locked to a common frequency. In a phased array, there is a special need to set the relative phases of the oscillators accurately, and to maintain the accuracy of the settings as parameters such as ambient temperature vary. A number of workers have investigated the frequency-locking properties of negative-resistance oscillators, but no comprehensive study of their phase-locking properties has been reported.