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Unit divides power from single input among any 12 of 120 output terminals and redistributes it in 6 microseconds. Microwave current from coaxial line excites disk feeding many radial strip transmission lines. Built for use in electronically-steered S-band antenna, device also divides and switches energy among filters and phase shifters.
A method and apparatus for increasing the signal to noise ratio of a receiving facility for coherent frequency reception by arraying receiving systems using separate antennas for each, or one antenna for all systems are presented. One system is operated with a carrier tracking loop to provide a first local oscillator frequency for the first and all other systems arrayed, with individual tracking loops in all other systems operated at IF for tracking out any phase differences due to separate group delays using an adjustable phase shifter for a second reference to compensate for different group delays in the antenna and low noise amplifier of each of the other systems. The second IF output of all systems is summed into the first system. This technique may also be used when two systems are arrayed to an antenna designed for circular or linear polarization diversity reception to effectively provide the same signal to noise ratio for both polarized signal transmission channels that would result from matched polarization. An arrangement adapted to high rate telemetry reception is disclosed. With additional components, the same arrangement is adapted to provide low rate telemetry reception as well.
Following the original idea of Peters, techniques have been developed to fabricate large area powder silica counters with refractive index between 1.06 to 1.12 in thicknesses of 1 cm and 2 cm respectively. The maximum size counter is 25 cm x 25 cm but the technique can be easily extended to 40 cm x 30 cm counters. Techniques have also been developed to dope this counter with the wavelength shifter p-terphenyl uniformly. The results of test runs at the Brookhaven National Laboratory and of laboratory runs using a superconducting magnet spectrometer on their performance are reported.
A J-band, space-fed transmissive array suitable to the constraints of space platform applications has been designed and an engineering model array has been fabricated and tested. Attention is given to the design of the aperture, radiating element, phase shifter module, and flatplate feed. Test results and performance are discussed with reference to gain, sidelobe level, and beamwidth as functions of frequency and scan angle.
A coherent optical spatial integration approach to ambiguity function generation is described. It uses one dimensional acousto-optic Bragg cells as input tranducers in conjunction with a space variant linear phase shifter, a passive optical element, to generate the two dimensional ambiguity function in one exposure. Results of a real time implementation of this system are shown.
The basic concept and design of a flatplate-fed transmission array are described and system performance requirements are summarized. Particular emphasis is given to the design of the aperture, the radiating element, the phase shifter, the flatplate feed, and the mechanical support structure. Fabrication and testing techniques are considered. Of the three major parameters of interest in demonstrating the performance capabilities of the transmissive array, beamwidth was shown to be the least sensitive to system amplitude and phase errors. Beam pointing angle was also shown to be relatively insensitive to errors. Close agreement between measured and calculated values was found for array gain. The greatest difference was found for array sidelone level.
A parallel architecture for computation of the linear convolution of two sequences of arbitrary lengths using the Fermat number transform (FNT) is described. In particular a pipeline structure is designed to compute a 128-point FNT. In this FNT, only additions and bit rotations are required. A standard barrel shifter circuit is modified so that it performs the required bit rotation operation. The overlap-save method is generalized for the FNT to compute a linear convolution of arbitrary length. A parallel architecture is developed to realize this type of overlap-save method using one FNT and several inverse FNTs of 128 points. The generalized overlap save method alleviates the usual dynamic range limitation in FNTs of long transform lengths. Its architecture is regular, simple, and expandable, and therefore naturally suitable for VLSI implementation.
An attempt to define a relationship between the strength and curvature of the latitudinal wind shear and the planetary waves is presented. Previous work based on the WKB method is reviewed and compared with Galerkin's method, which is found to be effective when considering low-order modes. The WKB method, however, increases in accuracy with the mode number. Both methods are applied to a linear wind shear profile and the Galerkin method is determined to be significantly superior in predicting the lowest order, and is therefore suitable for formulating the latitudinal structure of quasi-stationary Rossby waves in the middle atmosphere. In a second paper the mean zonal wind is assumed to depend on latitude only, and the effects of critical latitudes, where the Doppler shifter frequency is zero, on planetary waves are shown to include shear-induced instability in Kelvin waves. Further research to assay the extent that baroclinity alters stable winds is indicated.
Digital phase-shift standard used in combination with oscillator to calibrate other phase standards and phase-angle voltmeters. Phase-shifter circuit provides two square-wave outputs, A and B, with phase difference between them selectable in 30 degrees increments. Circuit is used with input signals as low as 1 volt rms, in almost any waveform.
Spacecraft array fed reflector antenna systems were assessed for particular application to a multiple fixed spot beam/multiple scanning spot beam system. Reflector optics systems are reviewed in addition to an investigation of the feasibility of the use of monolithic microwave integrated circuit power amplifiers and phase shifters in each element of the array feed.
Two algorithms are described which allow the plotting of individual points on a root locus diagram with or without time delay. The development was performed during the design of a continuous phase shifter used in the Baseband Antenna Combiner for the Deep Space Network (DSN). The algorithms, which are expected to be useful in similar DSN efforts, are simple enough to be implemented on a programmable pocket calculator. The coordinates of the open-loop zeros and poles, the gain constant K, and the time delay T are the data inputs.
Technology features of a beam forming network (BFN) employing ferrite devices to provide multiple beam antenna pattern control for satellites used in telecommunications are described. The BFN produces the phase and amplitude distribution for each horn in an antenna array, with the number of horns in the array being equal to the number of outputs in the BFN. One configuration involves microwave switches and permits illumination of a single feed horn at a time using ferrite latching circulators that function by reversing the circulation direction. A more flexible version, yielding a variable amplitude distribution across the feed horn array to accommodate changing traffic patterns or serving a TDMA system, includes the capability of forming nulls in the system with a variable phase shifter in the input ports. The antenna scan angles in phased arrays can be limited to 8 deg from center. Acceptable insertion losses have been demonstrated in BFN with hundreds of ports and switching rates as high as 10 kHz.
Located in a narrow canyon 15 km west of Boulder, Colorado, the Sunset pulsed Doppler radar was the first radar designed and constructed specifically as a VHF ST radar. The antenna system is a phased array of coaxial-colinear dopoles with computer-controlled phase shifters for each line of dipoles. It operates at a frequency of 40.475 MHz and a wavelength of 7.41M. Peak transmitter power is 100 kW. Aperture efficiency is 0.58 and resistive loss is 0.30 for its 3600 sq m area. The practical steering rate is 1 record/minute/position to any arbitrary antenna beam position. The first clear-air turbulence echoes and wind velocity measurements were obtained in 1974. Significant accomplishments are listed.
The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.
A mobile VHF Doppler system was developed. The electronic part is installed in a 20 ft container and tested using a special log periodic aerial to illuminate the 300 m dish. The system was extended by designing a mobile phased antenna array with finally 576 Yagi elements. The grouping of the single Yagis, the system of transmission lines, the phase shifters, the power splitters and the T/R switch are described. Results from the first two campaigns and a survey of future programs demonstrating the flexibility of this mobile system are summarized.
An apparatus and technique are described for receiving and tracking analog or digital phase modulated signals from 0 deg to 360 deg phase shift. In order to track a signal with many phases, a detector discerns the phase modulation of the incoming signal and a phase shifter generates a negative phase shift opposite in angle to the detected phase angle. This produces a converted series sideband component barrier signal. The residual carrier signal and the converted series sideband component carrier are added together to produce a tracking carrier signal. The tracking carrier signal is multiplied with the output from a voltage controlled oscillator in the tracking loop to obtain an error signal which drives the voltage controlled oscillator and tracks the incoming signal frequency. The technique is less susceptible to carrier interference which may degrade tracking and tracking may be performed at lower signal to noise ratios and for lower input signal power levels.
A technique for self-calibrating and phasing a lens-feed array antenna, while normal operation is stopped, utilizes reflected energy of a continuous and coherent wave broadcast by a transmitter through a central feed while a phase controller advances the phase angles of reciprocal phase shifters in radiation electronics of the array elements at different rates to provide a distinct frequency modulation of electromagnetic wave energy returned by reflection in one mode and leakage in another mode from the radiation electronics of each array element. The composite return signal received by a synchronous receiver goes through a Fourier transform processing system and produces a response function for each antenna element. Compensation of the phase angles for the antenna elements required to conform the antenna response to a precomputed array pattern is derived from the reciprocal square root of the response functions for the antenna elements which, for a rectangular array of NXM elements, is a response function T(n,m). A third mode of calibration uses an external pilot tone from a separate antenna element. Respective responses are thus obtained from the three modes of calibration.
Several antenna design concepts, operating at UHF (821 to 825 MHz transmit and 866 to 870 MHz receive bands), with gain ranging between 6 and 12 dBic, that are suitable for land mobile vehicles are presented. The antennas may be used within CONUS and ALASKA to communicate to and from a geosynchronous satellite. Depending on the type of steering mechanism, the antennas are broken down into three categories; (1) electronically scanned arrays with phase shifters, (2) electronically switched arrays with switchable power dividers/combiners, and (3) mechanically steered arrays. The operating characteristics of two of these design concepts, one a conformal antenna with electronic beam steering and the other a nonconformal design with mechanical steering, were evaluated with regard to two and three satellite system. Cost estimates of various antenna concepts were made and plotted against their overall gain performance.