Showing papers on "Antenna array published in 1981"

Microstrip array technology

Abstract: Past and present technological developments in microstrip antenna arrays are summarized. Emphasis is on exploring the potential of such arrays for satisfying the requirements of advanced military and commercial applications.

Phased array system to produce, steer and stabilize non-circularly-symmetric beams

Abstract: A phased array antenna system for eliminating antenna induced errors and distortions comprising an antenna array consisting of orthogonal rows and columns of antenna elements in which each row of elements is supplied signal power by a single beam forming network. Each input port of the beam forming network corresponds to an element of only one of a number of composite beam constituents which, when combined, form the complete composite beam. The beam constituents are adjusted in position to correct the composite beam shape as necessary by means of plurality of phase shifters, each of which is placed in series with only one input port of the beam forming networks. This unique positioning of the phase shifters in the antenna distribution system reduces the total number of phase shifters required to control the beam, permits the forming of a shaped beam such as a fan beam without the need for amplitude control and simplifies the complexity of the phased array control system.

Active millimeter wave simulator for missile seeker evaluations

Abstract: An active millimeter wave simulator for missile seeker evaluations wherein a missile seeker generates seeker signals and transmits them in the direction of an array of active antenna elements. Range timing signals are delayed in a time delay circuit to simulate a range between the missile seeker and a target. The seeker signals as received by the active antenna elements are supplied to a millimeter wave spectrum analyzer for determination of their frequency. A computer receives the determined frequency and controls a millimeter wave source to generate simulated target response signals with that same frequency but delayed in accordance with the time delay signal. The computer controls a master target control circuit to select a triad of antennas in the antenna array and to generate a phase center in the triad generating the target response signals. The millimeter wave spectrum analyzer further determines the frequency of the target response signals. The computer compares the frequencies of the target response signals and the missile seeker signals and controls the millimeter wave source to ensure correspondence between those frequencies.

Broadband microstrip antenna element and array

Abstract: Foam-supported highly efficient microstrip antennas are described. Theoretical and experimental results show that bandwidths up to 15 percent can be obtained at the expense of an increase in the antenna height (to about 0.1 wavelength). The performance of an array of broadband elements fed by a microstrip corporate feed network is also described.

Radar jammer with an antenna array of pseudo-randomly spaced radiating elements

Abstract: Disclosed herein is a radar jammer which utilizes an electronically agile, sparsely populated, phase controlled antenna array of pseudo-randomly spaced radiating elements to form a high gain, single narrow beam of radiation directed at a detected threat radar, but containing only a small fraction of the available transmitting power, while providing simultaneously therewith effective jamming radiation over a wide coverage region. Preferably, the plurality of radiating elements are sparsely disposed pseudo-randomly over an area surface to form an antenna array, the number of radiating elements in the array being less than the value of the surface area divided by the transmitting carrier wavelength (λ) squared.

Control device for steerable null antenna processor

Abstract: A radio receiving system partially overcomes jamming and other interferencey receiving on a narrow selected frequency which is rapidly changed, i.e., fast frequency hopping (FFH). The system includes a broadband receiving antenna array and a steerable null antenna processor which creates an antenna null pattern. A control device connected to the (FFH) radio connects a portion of the intermediate frequency (IF) of the radio to a bank of three narrowband IF filters in the control device. The output of the first IF filter, at the IF frequency, provides the signal (S) level and the outputs of the second and third filters, which are offset from the IF frequency, are summed to provide the interference (I) level; the I and S levels being used to control the antenna processor.

The design of a microstrip antenna array for a UHF space telemetry link

Abstract: An array of microstrip antenna panels was designed for use on a small instrumented satellite as part of a 400-MHz telemetry link between that satellite and NASA's shuttle spacecraft. A roughly omnidirectional \phi -plane pattern was desired. The 1.4-wavelength diameter of the satellite and the various ports and structures on its surface presented strong constraints on the antenna array design. Eight antennas, each one a quarter-wavelength panel with one radiating and one shorted edge, were chosen. A \phi -plane pattern ripple of 4.4 dB and a gain of at least 0.1 dB relative to a half-wavelength dipole were realized. The design technique used for the individual antenna panels included the study of feed-point location for impedance matching and the effect of losses in the dielectric. A superposition method was used to synthesize the radiation patterns for different numbers and different excitations of antennas on the satellite.

Radio signal receiving system

Abstract: A radio signal direction tendency system which includes an antenna array providing signals having a phase indicative of signal direction and a dual compressive receiver for reviewing and processing said signals to provide an output signal indicative of received signal direction.

Tracking radar system

Abstract: A tracking radar system which includes a variable frequency oscillator for supplying to a vertical antenna array an oscillation frequency which is changed for each of a number of pulses transmitted from the antenna array. The antenna array transmits an electric wave toward a target at a low altitude and receives an echo from the target. An electronic computer estimates an elevation angle of the target from the echo received by the antenna array according to array aperture sampling technique for each pulse. An averaging circuit averages those estimated elevation angles of the target to provide its elevation angle. Alternatively, the oscillation frequency may change for each of finite time intervals.

The effects of receiver tracking phase error on the performance of the concatenated Reed-Solomon Viterbi channel coding system

Abstract: Analytical and experimental results are presented of the effects of receiver tracking phase error, caused by weak signal conditions on either the uplink or the downlink or both, on the performance of the concatenated Reed-Solomon (RS) Viterbi channel coding system. The test results were obtained under an emulated S band uplink and X band downlink, two way space communication channel in the telecommunication development laboratory of JPL with data rates ranging from 4 kHz to 20 kHz. It is shown that, with ideal interleaving, the concatenated RS/Viterbi coding system is capable of yielding large coding gains at very low bit error probabilities over the Viterbi decoded convolutional only coding system. Results on the effects of receiver tracking phase errors on the performance of the concatenated coding system with antenna array combining are included.

Antenna array system usable for AM/FM receiver

Abstract: An antenna array system which comprises at least one balanced antenna having an electric neutral point and two output end terminals positioned closely to each other, at least one unbalanced antenna having one end thereof dc-coupled with the electric neutral point of the balance antenna and the other end thereof positioned closely to the end terminals of the balanced antenna, first means for picking up a first frequency wave signal such as FM wave signal from the balanced antenna, and second means for picking up a second frequency wave signal such as an AM wave signal from the unbalanced antenna.

Lossless annular rotary RF coupler

Abstract: An annular rotary RF coupler for installation about a vertical support structure, such as the mast of a ship. Two annuli are divided into circumferential increments providing a cellular structure of individual waveguide cross-sections. A lower annulus (stator) remains fixed, the individual waveguide sections therein being fed from a power-divided, equal-phase, feed configuration. The oppositely facing upper annulus (rotor) rotates with respect to the lower one about the 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. A single enlarged stator cell is employed to accept the residual energy in the power distribution transmission line, eliminating the need for a termination load and the corresponding power loss.

Antenna array with element isolation in the coupling network

Abstract: To isolate adjacent elements of an antenna array from each other, each feeder contains a power divider with four terminals, two of which are connected to the power dividers associated with the adjacent elements. The power dividers feed r.f. energy to the inactive elements in such a way that the latter no longer act as parasitic elements. The r.f. power dividers are so designed that three is a mismatch when looking from the antenna toward the power divider. This gives a further improvement in the isolation between adjacent antennas.

Array for reducing the number of antenna elements for radiating instrument landing system localizer signals

Abstract: In an antenna array for radiating Instrument Landing System localizer signals, a method for reducing the required number of antenna elements by the combination of average element to element spacing exceeding one wavelength and end-fire directive antenna elements which suppress spurious radiation that would otherwise occur.

Imaging Antenna Arrays

Abstract: A far-infrared imaging antenna array has been demonstrated for the first time. The array is a line of evaporated silver bow-tie antennas on a fused-quartz substrate with bismuth-micro-bolometer detectors. The measured optical transfer function shows that the system is diffraction-limited. This imaging array should find direct application in fusion plasma diagnostics. If the microbolometers can be replaced by more sensitive diode detectors, the array should also find application in radiometry and radar.

Millimeter wave monopulse comparator circuit

Abstract: An improved monopulse comparator circuit is achieved by a unique circuit layout. Four hybrid junctions are arranged on a low dielectric constant substrate and are interconnected in such way as to form a closed square figure. Distances between adjacent hybrid junctions are thus minimized. Input lines which connect the comparator circuit to a monopulse antenna array are disposed on the substrate external to the closed figure, as are output lines which connect the comparator to a monopulse guidance system. Right angle microstrip to waveguide transitions are used so that the comparator circuit need not be integrated onto the same substrate as the antenna array and the guidance system. The entire comparator layout is channelized to increase isolation between closely spaced lines.

Antenna drive arrangement for very high frequency omnidirectional range navigation system

Abstract: An antenna drive arrangement for a very high frequency omnidirectional range (VOR) navigation system for aircraft. The antenna has two vertically arrayed antenna elements located above a ground plane, and reference and variable phase signals are distributed to each of the antenna elements in amplitude and phase relationship selected to produce a null in the H-component of the radiated field which is substantially tangential to a projection of the ground plane. The null is located in a region of the field disposed radially outwardly of the antenna array.

Signal-to-noise ratios of array receiving systems with internal losses

Abstract: A formulation of the signal-to-noise ratio (SNR) for a typical antenna array receiving system that is more complete than those now available in the literature is presented. In addition to the external noise accepted by the array, it includes all forms of internal noise generated by the lossy components of the system. Distinct measurable factors account for distinct noise sources. For the analysis, it is shown that the actual lossy system can be replaced by an equivalent lossless system with appropriate attenuators. The formulation is used to design the combining network that will optimize the receiving system SNR for signals incident from a given direction in the presence of a known external noise distribution. The theory is applied to a specific array antenna receiving system operating under a variety of noise conditions, internal as well as external. A discussion of some typical results is presented.

Radio wave angle of incidence measurement apparatus

Abstract: This invention relates to a radio wave angle of incidence measurement apparatus which is applicable to radar and other detection systems, and which utilizes an antenna array with radiator elements distributed at a spacing larger than one half of the propagation wavelength. A radio signal is received by an antenna array that exhibit at least two different values of d/λ (where d is the inter-element spacing of the radiator elements, λ the propagation wavelength), and the resultant inter-element phase differences, of which there are at least two sets, are digitally measured. A phase difference converter circuit receives the digital signals representing the inter-element phase differences and processes them and generates an output signal that varies monotonically as the incident angle of the radio signal incident on the antenna array varies.

Collapsible antenna reflector

Abstract: According to the invention, this reflector comprises an articulated structure (11, 13) on which a reflective cap (15) can be mounted, the shape of which is adjustable thanks to tension links (16). Equipment of artificial satellites.

Loop-coupler commutating feed for scanning a circular array antenna

Abstract: A multiple-port loop-coupled commutating feed for a circular or cylindrical antenna array which is circumferentially scanned. A rotor assembly having a plurality of elongated coupling loops circumferentially spaced about an arc of its perimeter is fed from a stripline feed configuration excited at the driven central axis of the rotor. The rotor loops are formed by extension of printed circuit traces extant within the stripline feed about an arc of the rotor assembly. A plurality of elongated stator loops with essentially the same radial dimensions as the aforementioned rotor loops is provided, however the stator loops are distributed throughout the full 360° of the circular perimeter of the device to continuously couple a changing fraction of the stator loops to the rotor as the latter is rotated. An output port is provided connected to each stator loop and these output ports may then be discretely connected to corresponding elements of a circular array or columns of elements of a cylindrical array.

Beam Steering Antenna Control Technique

Abstract: A technique which reduces the requirement for constructing high accuracy phase shifters for steering the main beam in a small (less than 20 elements) linear antenna array is described. The key hardware components are the phase detectors which monitor the phase difference between adjacent radiating elements and a microcomputer to read the phase differences and adjust phase shifters to obtain the desired antenna performance. This closed loop technique will also provide a means for future investigations to verify theoretical versus experimental phase distributions and other element effects in small antenna arrays.

Antenna system for doppler omnidirectional range

Abstract: not available for EP0044456Abstract of corresponding document: US4412223To isolate adjacent elements of an antenna array from each other, each feeder contains a power divider with four terminals, two of which are connected to the power dividers associated with the adjacent elements. The power dividers feed r.f. energy to the inactive elements in such a way that the latter no longer act as parasitic elements. The r.f. power dividers are so designed that three is a mismatch when looking from the antenna toward the power divider. This gives a further improvement in the isolation between adjacent antennas.

Non-dispersive antenna array and its application to electronic scanning

Abstract: Antenne reseau non dispersive, du type antenne prisme dans laquelle le reseau primaire d'entree dispersif (1) et le reseau secondaire (IV) de sortie font un angle a entre eux, realisee par empilement d'antennes reseau non dispersives monodimensionnelles (Figure 3), pour chacune desquelles la propagation entre lesdits reseaux est guidee. Non-dispersive array antenna, antenna type prism in which the primary entry dispersive network (1) and the secondary network (IV) output at an angle between them, realized by stacking non-dispersive dimensional array antennas (Figure 3 ), for each of which the propagation between said networks is guided. Application aux antennes prismes a balayage electronique. Application antennas scanning electron prisms.

Noise in phased antenna arrays

Abstract: 1. Interaction of radiators has an appreciable effect on the noise characteristics of passive as well as active phased antenna arrays. This effect can be rather accurately accounted for with the aid of only one parameter of the radiator array, namely its effective reflection coefficient defined in the transmission mode with excitation of all channels. 2. The sensitivity of a phased antenna array depends on the effective reflection coefficient differently than does the antenna gain. In passive phased antenna arrays, moreover, the sensivity decreases with beam deflection more than does the gain. 3. In active phased antenna arrays there is a theoretical possibility to weaken the dependence of the sensitivity on the scanning angle, viz., by optimizing the parameters of the input stages.

Study of a MIC - Phased Array Antenna for Man - Transportable Solid State Search Radar

Abstract: This work describes a possible approach towards the design of a particular class of phased array such as MIC solid state antenna array for search radars. The main characteristics of such an antenna are brought out in accordance with a general theory of open - ended waveguide planar array[l]. The electromagnetic field problem for the single MIC radiating element is developed on the basis of the model having an imperfect electric and magnetic wall cavity[2], obtaining theoretical formulas which agree very well with experimental results. The mutual coupling coefficient between rectangular X-band MIC antennas has been considered too and a new general formula, in close agreement with the experimental data, has been determined. A description of synthesizing method for symmetrically and asymmetrically shaped beams with a numerical evaluation of the radiating characteristics of an X-band MIC planar array antenna having an E - plane "pencil" beam and an H-plane "quasi cosec2" shaped beam is given.