Showing papers on "Feed horn published in 1973"

Short axial length broad-band horns

Abstract: Ever-increasing antenna frequency bandwidth requirements for countermeasures applications and electromagnetic compatibility measurements have provided the impetus for the development of a series of very broad-band horns. In addition to the broad bandwidth, a substantial reduction in axial length over that of earlier models has been achieved for the two designs discussed in this communication. The first horn described covers the frequency range from 1.0-12.0 GHz with the flared portion of the horn having an axial length of 6 in as compared with 12 in for an earlier model. Although horn antennas are not commonly considered for use at frequencies as low as 0.2 GHz, the short axial length design appeared to be an attractive approach in developing a very reasonably sized antenna operating in the 0.2-2.0 GHz range. The technique of fabricating the H plane walls in the form of a grid was used in both designs as a means of maintaining the required H -plane half-power beamwidths. The grid for the 1.0-12.0 GHz horn is of printed circuit form while the grid elements of the lower frequency horn are made of aluminum tubing. Electrical characteristics of both designs are presented, as well as some additional data for recent advances which indicate that a further reduction in axial length or an increase in bandwidth can be achieved with only a moderate rise in VSWR in the lower portion of the frequency range.

Coaxial feeds for high aperture efficiency and low spillover of paraboloidal reflector antennas

Abstract: Coaxial feeds produce an approximate sector-shaped pattern, an almost optimum pattern of a feed for high aperture efficiency and low spillover of paraboloid antennas. Such a coaxial feed consists of a central circular waveguide which is surrounded by one or more conductors with circular cross sections. Theoretical and experimental investigations on coaxial feeds excited by H 11 modes have shown that the first ring yields the highest increase in the aperture efficiency of paraboloid antennas illuminated by them. Measurements performed on paraboloid antennas illuminated by a coaxial feed with only one ring yielded aperture efficiencies of 68 to 75 percent for angular apertures of the paraboloidal reflector of 100\deg to 160\deg . Circularly symmetric patterns in conjunction with almost linearly polarized aperture fields can be achieved by multimode coaxial feeds. The values for the aperture efficiency, which are calculated for paraboloid antennas illuminated by multimode coaxial feeds, nearly reach the theoretical optimum. The measured values are 68 to 80 percent. In addition, the multimode feeds produce very little cross polarization.

Effects on correlation between two mobile radio base-station antennas

Abstract: The correlation between signals received by two mobile radio base-station antennas is investigated to determine spacing requirements for space diversity. Measurements of the fading of UHF signals received by two base-station horn antennas oriented at different angles with respect to the incoming mobile radio signal were made for different antenna spacings. The experimental results are compared with an analytical expression derived in this paper; they agree fairly well. A further experiment was made after removing the possible local scatterers surrounding the base station. Comparing these two experimental results, we find that the following are true. 1) Propagation in the direction of a line connecting the two base-station antennas is the critical case and requires a large separation of 70 wavelengths. As soon as the incoming wave is 10° away from the in-line axis, the spacing requirement drops to 30 wavelengths. 2) Local scatterers at the base station tend to decrease the correlation between signals received at the two antennas. We conclude that an upper limit to the spacing of antennas used for diversity can be obtained and that it is within the achievable range.

Radio frequency communication systems

Abstract: A radio communication system suitable for use in tunnels and mines uses a leaky radiating transmission line connected between a transmitter and a receiver to transmit radio frequency signals to a local receiver. Unidirectional repeaters are located in the transmission line and a return path is provided by a normal wire carrying demodulated signals from the receiver to the transmitter.

Determination of Horn Antenna Phase Centers by Edge Diffraction Theory

Abstract: The edge diffraction method of analysis utilized in the past to determine amplitude patterns is extended in this paper to predict the radiation phase center of pyramidal horn antennas. A series of extensive phase and amplitude measurements were performed on these antennas to determine the validity of the theoretical results. The measurements were performed over a frequency range of 7.5 to 10.5 GHz in the E plane of the antennas. The phase measurements were accurate to ±0.2 electrical degrees, so that the phase center locations relative to the horn apertures were repeatably determined to better than 0.010 inch for horn apertures as large as 7 inches. The results of the measurements indicate that excellent agreement is obtained with the theory in predicting the phase center location of the larger horns (kRE > 50). For the smaller horns, however, there is a large discrepancy between the theory and measurements. The measured phase centers of the smaller horns exhibit a large variation with frequency which cannot be explained with the existing theory. Several reasons for the discrepancy are presented, and it is concluded that a more rigorous approach involving higher order modes has to be developed for the smaller horns.

Microwave powered reusable orbiting space tug

Abstract: This space vehicle is used as a ''''tugboat'''' for propelling other space vehicles. The tug has a pair of propulsion nozzles to which a propulsion fluid is fed by way of an absorption chamber. A large microwave antenna is mounted on the space tug for receiving and concentrating a microwave beam which may come from the earth''s surface. The nozzles and antenna are pivotable relative to each other. Large but short wave guides lead from the feed horn of the antenna through the pivot trunnions for conveying the concentrated microwave beam to the absorption chambers. The beam, which to this point has travelled through a vacuum, is nearly quantitively absorbed by the propulsion fluid which is thereby heated to a plasma. The plasma is directed to the propulsion nozzle by a magnetic field. A single component propulsion fluid is contained in replaceable tanks and energy is imparted to the fluid by way of the microwave beam rather than by chemical reaction. A phased array of antennas permits focusing at high orbital altitudes.

Scale model development of a high efficiency dual polarized line feed for the Arecibo spherical reflector

Abstract: The experimental development of a 1:6.535 scale model line feed for the Arecibo spherical reflector is described. The 14.7-ft long model at 2810 MHz simulates a 96.6-ft feed at 430 MHz capable of illuminating the full 1000-ft aperture of the reflector. The feed design requirements are discussed and an experimental program is outlined in which the necessary line source parameters were established using a number of leaky cylindrical test sections. Experimental measurements of both the near and far fields of the model feed are described and typical results are quoted and discussed. Finally, some results obtained after installation of a full size feed in the reflector are given and compared with predictions based on the model data.

Coaxial horn antenna

Abstract: A wide band, multi-mode antenna having a plurality of coaxial, independently fed, radiating horns. Each horn has multiple feeds which can be energized in various phase relationships to control polarization. The antenna can be used as a direct radiator, or to illuminate a reflector, has transmit or receive capabilities, and is adaptable to monopulse operation. The antenna is a compact rigid unit of very simple construction.

Dual-band reflector-feed element for frequency-reuse applications

Abstract: Proposed frequency-reuse systems have created a need for reflector-feed elements that generate symmetrical primary patterns with low crosspolar content. The letter describes a horn radiator of only 1? diameter that meets these requirements over two discrete frequency bands.

Experimental verification of the analysis of umbrella parabolic reflectors

Abstract: Gored umbrella parabolic reflectors with symmetric aperture illumination have been treated analytically in a recent paper. This communication extends the analysis to the case where the primary feed illumination is not symmetric, because real primary feeds usually have unequal E - and H -plane beamwidths. The gore loss and the shift in the defocusing curve obtained using the modified gain expression are in excellent agreement with values measured for a smooth parabolic reflector and a gore parabolic reflector of the same diameter.

Wide angle antenna system

Abstract: An antenna employing electronically controlled radiating elements that produce a primary illumination of a circular ring source aperture. The aperture is fed by a parallel plate waveguide that contains radiating elements curved around to conform to a cylindrical surface, and that is fed by a similarly curved widely flared feed horn forming a power divider to the radiating elements.

Design of multiple-edge blinders for large horn reflector antennas

Abstract: Attaching blinders to the sides of pyramidal horn reflector antennas and other large aperture antennas is one method of controlling high sidelobes for horizontal polarization. This paper describes analysis and design procedures for arriving at a useful multiple-edge blinder for reducing undesirable sidelobes of a pyramidal horn reflector antenna. Several blinders have been designed and tested for use with a pyramidal horn reflector antenna. They are directed at reducing a high sidelobe near 90\deg in the azimuth plane where levels (referred to the main lobe) of -52 dB at 3.74 GHz and -58 dB at 6.325 GHz are presently typical. A 14-edge blinder designed using these techniques reduced these levels by 20 dB at 3.74 GHz and 12 dB at 6.325 GHz and did not significantly degrade antenna performance for other angles and other polarizations.

Multiple-beam antenna for domestic communication satellites

Abstract: This communication describes the design method of and experimental results obtained from a new multiple-beam antenna for domestic communication satellites. A seven-beam model antenna 1.98 m in diameter has been fabricated and evaluated in the 50-GHz frequency band, and the measurement data are reported here.

Feed horns for reflector dishes

Abstract: A feed horn for a parabolic reflector includes a feed waveguide capable of supporting a first electromagnetic mode and a cylindrical member surrounding an open-ended radiating portion of said feed guide and located about said open end at a distance to cause a second mode to be supported. Said first and second modes as propagating combine to provide a radiation pattern for illuminating said reflector to provide a high performance antenna system.

High performance S-band horn antennas for radiometer use

Abstract: Horn antennas of four types: pyramidal corrugated, conical corrugated, pyramidal dual mode and conical dual mode, have been constructed and evaluated for use as S-band radiometer antennas. Each of the structures is described and radiation patterns and impedance and resistive loss measurements including a layer of foreign material on a thin radome, are presented. A precision method for determining reflection losses is described using a multiprobe reflectometer technique. The same technique is also applied to the measurement of resistive losses by closing the ends of the antennas with short circuit plates and determining the losses from an accurate measurement of the reflection coefficient. The radiation patterns were recorded with the aid of a real-time digital computer. The stored patterns were then processed to yield gain and beam efficiency. It was concluded that it is possible to design a highly efficient antenna for radiometer use and to measure its parameters precisely. However, it was found that it is necessary to modify the conventional definition of beamwidth somewhat if this term is to be meaningful for radiometer applications.

Modified diffraction coefficients for focusing reflectors

Abstract: A modification to the halfplane diffraction coefficients is given for a plane wave incident on a curved screen. The result is used to calculate the near field of a parabolic reflector under plane-wave illumination. Comparison with the physical-optics method shows excellent agreement.

Offset-reflector antennas with offset feeds

Abstract: The development of a simple mathematical model for the vector radiation fields from offset-parabolic-reflector antennas is outlined. The model permits the primary feed to be offset from the reflector geometric focus, and thus allows the study of multiple-beam antennas. Predicted results are shown and correlated with measurements made on a 30 GHz antenna system.

Selective reduction in back radiation from paraboloidal reflector antennas

Abstract: By structurally changing the rim of reflector antennas, reduction of radiation is achieved in the shadow region. An experimental approach is used based on the concepts of edge diffraction theory.

Double spherical cassegrain reflector antennas

Abstract: There is a need for high gain antennas that are capable of rapid scanning and multibeam operations. This paper presents a study of the double-spherical Cassegrain reflector to ascertain whether this antenna is practical for these purposes. Aperture blocking, spread of the field, and phase and amplitude distributions are examined using geometric optical techniques. Some radiation patterns are calculated to show the effects of illumination taper, aperture blocking, and phase errors.

Low-noise dual-hybrid-mode horn—an experimental model†

Abstract: This paper presents a detailed description of an experimental corrugated feed horn designed to operate at the focus of a paraboloidal reflector. It is found that the corrugation depth does not critically restrict the bandwidth of the antenna, and the main requirement is that the thickness of the corrugation teeth must be small compared to the wavelength. The radiation pattern of the horn maintains a near-perfect cylindrical symmetry over o 10% bandwidth, and the V.S.W.R. is less than 1-1 within the some bandwidth. The overall efficiency of the antenna system is found to be within 3% of the maximum value predicted by the theory. In addition, the spill-over loss is very small, and is of the order of 3·5%. This indicates that a low-noise, high-efficiency antenna can be designed without the need of a massive and more costly conical horn used in dual-reflector systems to date.

Multi-horn wheel scanner with stationary feed pipe for schwarzschild radar antenna

Abstract: A plurality of radial waveguides communicate microwave energy to respective circumferentially positioned horns. A stationary feed horn is disposed in the center of the waveguides to sequentially feed microwave energy to centrally located inlet openings in the waveguides. The waveguides rotate as a wheel while the circumferential horns generate a unidirectional sector scan beam. The scanner is installed in a Schwarzschild reflector system to provide a high gain, scanning, pencil beam in the far field. In addition, a conical scan mode is provided. A switchable mirror permits the operator to select either mode of operation.

Influence of horn length on radiation pattern of oblique-flare-angle corrugated horn

Abstract: The influence of horn length on the radiation pattern of an oblique-flare-angle corrugated horn is described Two experiments with a 110° horn are reported These show that a horn with three slots has a radiation pattern which is essentially the same as that of a horn with five slots It is also demonstrated that the innermost slot has a dominant effect on the pattern

Calculation of the secondary-radiation pattern for a paraboloid reflector with a given illumination function and feed position

Abstract: A computer program is described for the calculation of the near-axis secondary-radiation pattern of a parabolic reflector. The program has been devised for a laterally or axially displaced feed, in particular a log-periodic dipole array. The illumination-function data are input in the form of radiation-pattern co-ordinates of the feed aerial.

Hybrid Mode Tracking Feed Techniques Study.

Abstract: : EW ;F30602-72-C-0171RADCTR-73-71(*antenna feeds, tracking), waveguides, reflectors, antenna radiation patterns, standing wave ratios, bandwidth, radiofrequency interferenceEquations were developed for the hybrid mode fields which exist in a square corrugated waveguide. Propagation constants were obtained for the various modes of interest. A hybrid-mode tracking feed horn was designed and tested, and its characteristics compared with those obtained analytically. Evaluation was based on radiation characteristics, VSWR, bandwidth, and channel isolation. Emphasis was placed in two areas: first, to show the radiation characteristics the feed horn would have if working perfectly and second, to obtain a good understanding of the feed system to point out the areas requiring further effort.