Showing papers on "Feed horn published in 1990"

Individually fed multiloop antennas for electronic security systems

Abstract: An antenna system for use in an electronic security system transmitter (10) or receiver (12) having two or more loops. Each loop (24,26,28,30,40,42,44,46) of the transmitter or receiver antenna system (14,16) being individually connected to a splitter network (20) in the transmitter (10) and a combiner network (22) in the receiver (12).

Vehicular radar detector integrated into rear-view mirror - is metallised in segments on rear surface for transmission of microwaves and reception of echoes

Abstract: The optical mirror (3) is transparent to the microwave radiation from a feed horn (4) directed at a reflector (5) mounted on the inside of the rear wall (1) of the mirror housing contg. the millimetric-wave generator (2). The radar is protected against dirt and moisture by a radome (6) of dielectric material with a thickness of half a wavelength (or an integral multiple). The metallised glass (3) can serve this purpose if suitable sealed. ADVANTAGE - Blind zone of rear-view mirror is monitored by integral microwave radar for greater safety in traffic.

Fan beam generated by a linear-array fed parabolic reflector

Abstract: The theoretical background and the results of computer simulations and experimental studies for a parabolic reflector fed by a linear array are detailed. The concept of using a parabolic reflector antenna fed by a small linear array to generate fan-beam patterns is validated. Large angle scan along the broad-beam direction of the fan beam can be achieved by offsetting the linear array laterally. It is both empirically and numerically demonstrated that the array feed must be displaced in the reflector's axial direction to an optimum location from the focal plane in order to achieve the best antenna gain performance. As a result, the linear-array fed parabolic reflector can be used in place of a long planar array in a multifunctional reflector antenna system. >

A wide-band prime-focus horn for low-noise receiver applications

Abstract: A horn suitable for a prime-focus antenna requiring low cross polarization, wide bandwidth, and low spillover is described. The design is particularly suited for low-noise applications such as high-quality satellite earth-station antennas and radio telescopes. The horn has a return loss substantially better than 20 dB, a cross polar sidelobe level better than -20 dB, a beamwidth variation of 40% and negligible phase center shift. >

Space fed phased array antenna with dual phase shifter

Abstract: An array antenna (10) for a radar includes a phase shifter arrangement wherein, in the transmitting mode, ferrite phase shifters (35) are used to collimate and direct a beam of transmitted radio frequency energy originating at a feed horn and, in the receiving mode, amplifiers (45) and diode phase shifters (37) are used to amplify and to focus received radio frequency energy on a feed horn. Each front antenna (31) is coupled by a switch (39), limiter (43), amplifier (45), diode phase shifters (37), and a circulator (41) to the corresponding rear antenna (33), and the rear antenna (33) is coupled through the circulator (41), the ferrite phase shifters (35), and the switch (39) to the front antenna (31).

Ranging system beam steering

Abstract: An aircraft radar and altimeter system, comprising a radio transmitter and a transmitting antenna for radiating a beam of radio energy, a radio receiver and receiving antenna for receiving radio energy reflected from the ground, processing means for comparing the signal received by the receiver with the signal transmitted by the transmitter and determined from the comparison the instantaneous altitude of the aircraft above the ground, and means for changing the direction of radiation of the beam relative to the aircraft to compensate for changes in the attitude of the aircraft relative to the horizontal about at least one of the fore and aft and side-to-side axes.

Dual-band/wide-illumination-angle feed horns with low off-axis cross polarization

Abstract: A design for a wide-angle illumination feed horn appropriate for front-fed, symmetric, and offset-fed reflectors is discussed. Low cross polarization and control of the copolarized beamwidths in two separated frequency bands are achieved. The design combines a Potter (1963) dual-mode (TE/sub 11/+TM/sub 11/) step and scalar rings to achieve this performance. The approach is feasible for frequency band separations of between 1.3 and 1.7 and has been used for the 4/6-, 11/14-, 12/17-, and 20/30-GHz satellite communications bands. The cross-polarization performance is more a function of the individual bandwidths than the separation of the two bandwidths. Data are presented on a feed horn design operating over the frequency bands of 4.0 to 4.2 GHz and 6.2 to 6.4 GHz. Pattern and cross-polarization data on a broader-band feed horn operating from 3.7 to 4.2 GHz and 5.925 to 6.425 GHz are also presented. A swept frequency tuning procedure for minimizing the cross polarization over the frequency bands of interest is also discussed. >

A Multimode Feed System for Angle Diversity Operation in Two Polarizations

Abstract: A new feed system is presented providing dual polarized angle diversity operation of microwave links. It requires only one feed horn to generate the two main and two diversity beams, due to the utilization of higher order modes. First experimental results are provided for a feed system which has been integrated in a 4×4 m shell antenna (XPD improved) operating in the frequency band 5.925-6.425 GHz.

Arcjet plasma plume effect on a microwave reflector antenna. [thruster plasma effects on reflector antenna microwaves

Abstract: A configuration is described to measure the effect of the plasma produced by an arcjet thruster on a reflector antenna. The diagnostic consists of a small movable rf probe coupled to a Hewlett–Packard 8510 network analyzer. Because the perturbation is expected to be small (<10° phase shift), wall reflections are an important consideration. To minimize their effect we use Fourier transform gating techniques.

Experimental shaped reflector antenna

Abstract: A shaped reflector antenna was designed using an aperture synthesis method. The antenna was designed to operate over the Ku band transmit frequencies (11.7 to 12.2 GHz). The design consists of a single Potter horn feeding a 28.34 in by 28.24 in. square aperture shaped reflector with a 26.15 in. effective focal length. It turns out that the phase front for the radiation pattern of the Potter horn feed is not spherical over the angular extent of the reflector. If the Potter horn feed had a true spherical phase front, then the measured phase would be constant, as was assumed in the calculated results. It is also suspected that the variation of this phase with frequency is the cause of the large frequency variation in the measured shaped reflector radiation patterns. Some preliminary work was done in which a shaped reflector radiation pattern was recalculated using a feed model that took into account phase variation. >

A comparison of reflector antenna designs for wide‐angle scanning

Abstract: Conventional reflector antennas are typically designed for up to ±20 beamwidths scan. In this paper, we try to stretch this scan range to some ± 300 beamwidths by varying various parameters of single- and dualreflector antennas. It is found that a symmetrical parabolic reflector with f/D = 2 and a single circular waveguide feed has the minimum scan loss (only 0.6 dB at θ0 = 8°, or a 114 beamwidth scan). Reduction of antenna size by means of focal length folding (Cassegrain) of cluster feed implementation is discussed.

Simulated corrugated feed horn antenna

Abstract: A technique for developing a new type of feed horn with the same radiation characteristics as a metallic corrugated horn is presented. This horn antenna with low back and sidelobe levels can be used as a substitute for a metallic corrugated horn with added advantages of high gain, low cross polarization, low cost, and light weight. The convenience of the photolithographic technique for fabricating simulated corrugated surfaces opens the possibility of the mass production of such horns with simpler methods. >

Analysis of horn antennas with impedance walls

Abstract: An integral-equation moment-method technique has been developed for rigorous analysis of horn antennas. Using this technique, one can accurately analyze a horn antenna with perfectly conducting or impedance walls, and with or without an infinite ground plane. Horn antenna performance in the case of impedance walls was investigated by using a high-permeability X-band magnetic absorbing nitrile material. The impedance tapering on the walls is shown to have a significant effect on the horn antenna pattern. >

Performance evaluation of a near field fed double curvature reflector

Abstract: Hybrid antenna systems making use of near-field fed reflector consist of one or two reflectors fed by a cluster of radiating elements placed out of the focal plane and mainly controlled in phase, thus generating a multibeam coverage. Results showing the possibility of reducing the number of feeds, when the scanning area is no longer circular, by shaping the reflector surface as well as the feed cluster contours are reported. Numerical results are presented indicating that in a near-field fed antenna the number of the radiating elements, independently fed, may be reduced together with a reduction of the scanning area, even when this area is not regular. In this case both the reflector surface and the feed cluster contours have to be properly shaped. >

Radio receiver measurement of vehicle position variation - comparing transition times from fixed transmitter to vehicle mounted receiver

Abstract: Radio receiver measurement of the variation of a vehicle's position involves a vehicle mounted receiver receiving a sequence of radio signals (SO-Sn) transmitted at constant time intervals by a stationary radio transmitter (A). A time measurement is started at a first operating position (P1) of the radio receiver and the difference in transition times determined from the transmitter to the first position and to a second position (P2) to which the receiver is moved.

A multimode pyramidal horn with symmetrical dielectric loading-a high efficiency feed for reflector antennas in satellite communications

Abstract: A novel multimode pyramidal horn with symmetric dielectric loading on the horn walls is presented. The horn possesses the desirable features of high aperture efficiency (on-axis gain), low sidelobe levels, and low cross polar radiation suitable for applications in satellite communication. In the development of this efficient pyramidal horn, the technique of multimode generation of high order TE/TM/sub 12/ modes by a step discontinuity and a change ill the horn flare angle for equalizing E- and H-plane patterns at reduced sidelobe levels is combined with symmetrical dielectric loading on the horn walls for aperture efficiency enhancement. This pyramidal feed horn can be used for developing an antenna system with monopulse capability for searching and tracking purposes in radar and astronomy applications. Experimental results are presented on a multimode (double-flare) pyramidal horn for operations in the Ku-band. >

Dual band coaxial feedhorn design

Abstract: A dual band coaxial feedhorn was investigated for use in a deep-dish paraboloidal reflector antenna. The radiation patterns were measured and compared with computed results at the mid frequencies, 3.95 GHz and 11.95 GHz, of two different bands. The test results confirm that the dual band coaxial feedhorn with a coaxial cavity has the broad beam radiation patterns which are required for deep-dish paraboloidal reflector antennas. The ripples existing in the upper-band radiation pattern are caused by the coaxial waveguide which surrounds the inner circular waveguide. >

Development of X-band space feed phased array antenna system

Abstract: An electronically controlled phased-array antenna system using space feed through a lens array is presented. The aperture excitations of the array elements for monopulse sum and difference patterns are illuminated by a multimode feed horn which provides an efficient aperture illumination with less spillover loss than the conventional multiple feed horn does. The radiating element couples the pickup element through a dual-mode reciprocal ferrite phase shifter. The beam position in space is electronically steered by a beam-steering controller. The antenna system consists of 496 radiators spread over a circular aperture of 24-cm radius. The focal ratio is set to be 0.61. A triangular lattice grid is adopted to optimize the aperture efficiency. Results of simulation and measured far-field patterns are presented. >

An offset reflector antenna

Abstract: A cross polarisation component of electric field on an aperture plane of a reflector 1 in an offset reflector antenna is prevented by purposely generating a cross polarisation component on an opening plane 4 of a feed horn 2, so as to reduce the cross polarisation component of electric field on the aperture plane of the reflector. The structure for providing the cross polarisation component on the aperture of a feed horn 2 may be, for instance, an oblique structure, figure 4a, with a slant angle theta A-between normal axis direction of an aperture of a feed horn and an axis of the feed horn; an asymmetrical flange (6), figure 4C, attached on an aperture plane of the feed horn (2); asymmetrical chokes (8a-8n), figure 5a, on a symmetrical flange on an aperture plane of the feed horn; or an asymmetrical corrugated structure (9), figure 5b, attached on an inner wall of the feed horn.

Rain-Blowing Plenum For Antenna Feed Horn

Abstract: Double-diaphragm radome drives raindrops away from antenna feed horn. Includes solid diaphragm at mouth of feed horn surmounted by perforated diaphragm. Pressurized air in plenum between diaphragms flows out through perforations. Eliminates increase in noise temperature occuring when water covers radome. Useful for X-band and higher frequencies, susceptible to effects of water.

Antennas for direct to home reception of DBS television

Abstract: Outdoor units were required for domestic DBS TVRO stations. Satellites had been ordered to provide 59 dBW EIRP or more, as had receivers incorporating custom DMAC integrated circuits and eurocypher modules. It was established that an antenna aperture width of about one foot would be required and that the antenna could be either a parabolic dish or a flat plate array. Research confirmed that both flat plate arrays and offset-feed parabolic reflector antennas are acceptable to the market. Two Squarial arrays and two reflectors were made available by approved manufacturers in time for launch of BSB programmes. The antennas are designed to facilitate installation by professionals and by the DIY enthusiast. An installation display facility was incorporated in the receiver to monitor the DMAC bit error rate.

Highly contoured beam antennas for 21 ghz‐band ldr hub stations

Abstract: With a view to applications of the 21-GHz LDR (local distribution radio) system to point-to-multipoint systems, a hub station antenna was developed which produces an improved cosecant square beam in the vertical plane and the fan beam in the horizontal plane. The antenna is made of an offset-shaped reflector fed by a corrugated conical horn with a rotationally symmetric beam. As a shaped reflector synthesis, an efficient and accurate method is proposed, which is a combination of the geometrical optics method and the physical optics method. To produce the high gain part of the shaped beam (beam nose), the method of a doubly curved reflector is extended so that the main part of the reflector surface is obtained in the geometrical optic process. Next, to form the low gain part (beam skirt), the physical optics shaped reflector design method is applied to an upper portion of the reflector. By defining the boundary shape of the reflector on the cone with a horn as the vertex and the flare angle from the horn axis constant, the control of the illumination level over the entire reflector edge is low and uniform regardless of the polarization, thereby improving the sidelobe characteristics. The measured radiation characteristics of the test antenna are extremely good so that the validity and effectiveness of the present antenna design are proven. The measured values include the simulated experimental results in the case where rain drops are attached to the radome.

An advanced multi-fraction Ku-band antenna for satellite application

Abstract: A high-performance Tx/Rx, reorientable dual linearly polarized, steerable spot beam Ku-band antenna has been developed. The reflector configuration of this antenna offers a number of desirable features in terms of compactness, reliability, and electrical performance. The feed system implements a range of innovative component designs to accomplish a multifunction operation. The compact Gregorian reflector with the multifunction feed system offers an attractive solution for steerable spot beam spacecraft antennas. A protoflight model of this feed system has been built and successfully tested for space qualification requirements. >

Research prototype of a multi-aperture coupler for mode diversity

Abstract: A multiaperture mode-diversity coupler built to operate in the A-band (26.5-40.0 GHz) is described. It can separate the horizontally polarized higher-order mode from the feed waveguide of a horn reflector antenna. This type of coupler can be used to provide diversity protection to microwave radio links. Measurements show that this coupler adequately separates the higher-order horizontal mode and does not affect propagation of the vertical polarized signals; therefore, it can be used in links where both polarizations are employed. This coupler can be retrofitted to existing horn antennas. Unlike other pattern diversity schemes it does not degrade the sidelobe performance. >

Elliptical and rectangular dielcore horns for reflector antenna applications

Abstract: A novel class of dielectric-loaded feed horns, so-called dielcore horns, for generating elliptical radiation patterns is presented. The dielcore horns are used as feeds in an offset parabolic reflector with an elliptical aperture. Their characteristics are high feed efficiency for elliptical beams and high cross-polar isolation for dual-linear and for dual-circular polarization. Compared to corrugated rectangular or elliptical horns they have considerably larger cross-polar bandwidth and potentially lower production costs. The calculated feed patterns in the narrowest pattern planes of the open-ended waveguides are shown for both the fundamental orthogonal modes. Copolar and cross-polar patterns in the two major planes of an offset parabolic reflector with an elliptical projected aperture fed by a rectangular open-ended dielcore waveguide are also shown. >

A pattern synthesis technique to compensate for distortions in large reflector antennas

Abstract: Surface errors on parabolic reflector antennas degrade the overall performance of the antenna. An approach to electromagnetic compensation that uses pattern synthesis to compensate for the surface errors is presented. It differs from previous methods in two major respects. The previous studies used a global algorithm that attempts to correct the entire focal plane field. The pattern synthesis approach uses a localized algorithm in which pattern corrections are directed specifically towards portions of the pattern requiring improvement. The second major difference is that the pattern synthesis technique does not require knowledge of the reflector surface, but instead uses radiation pattern data to perform the compensation. Amplitude-only measurements can be used to determine the relative phase with reasonable accuracy at the location of the pattern distortions. Once the relative phase is known, the weighting of the auxiliary beams can be determined for compensation. Results from a specific application of the compensation technique are presented. >

Device for scanning (sampling) and/or testing body surfaces

Abstract: A device for scanning and/or testing body surfaces having a transmitter for electromagnetic waves and having a receiver for the waves reflected from the body. Said device has a reflector, which is arranged between the transmitter and the body and can be pivoted and/or rotated, for the waves, the reflection surface of which reflector is intersected by the rotation axis of the reflector at an angle other than 90@.