Showing papers on "Feed horn published in 1989"

Horn array antenna

Abstract: PURPOSE: To prevent the reduction in gain and to suppress thermal noise generated in the inside of an antenna lower by arranging a horn antenna in an array, connecting a waveguide to the connection of horn antennas so as to combine power through the waveguide. CONSTITUTION: Horn antennas 1 are arranged as an array, waveguides 2, 3 are connected to the connection of each horn antenna 1 to combine the power with the waveguide. For example, 16 horn antennas 1 are arranged in an array of 4×4 to constitute the horn array antenna. The radiation efficiency of the horn antenna 1 is ≥80% being close to 90% and the waveguide 2 is directly connected to the horn 1 integrally to reduce the connection loss. Thus, the decrease in the gain is prevented and the thermal noise caused in the inside of the antenna is suppressed lower. COPYRIGHT: (C)1990,JPO&Japio

Compensated microwave feed horn

Abstract: A feed horn employing a novel compensator design which substantially re­duces off-axis cross polarized components of circularly polarized energy over a wide range of angular directions. The compensator comprises a plurality of L-shaped compensating conductors (22) disposed in a generally symmetrical fashion about a longi­tudinal axis of the feed horn (10). The conductors (22) extend inwardly from the output aper­ture (18) of the feed horn (10) and then radially outwards a predetermined distance away from the axis toward the horn sidewall. The conductors (22) are disposed at an angle relative to the axis, which angle is generally defined by an cone whose apex is the same as the apex of the feed horn. A nonconducting support structure (20) supports the conduc­tors (22) within the feed horn (10). A dielectric matching member (26) is disposed in the feed horn (10) to eliminate unwanted energy reflections.

Gaussian beam techniques for illuminating reflector antennas

Abstract: Simple design procedures are presented for use when a Gaussian beam is used to illuminate a classical reflector antenna. Displacement of the location of the beamwaist toward the focusing element in the case of electrically small antennas where the aperture is in the near field of the feed was calculated together with modification of the required beamwaist radius. Dual reflector antennas were discussed and design procedures appropriate for systems with large and small focal length to diameter ratio developed. Cases where a reflector or subreflector is electrically small, or in the near field of a feed, are readily treated. For elliptical beam antennas, a simple illumination system using only a scalar horn and a single cylindrical lens can generally be found; this has no ray optics analogue. A configuration of this type is discussed, with a practical case study of a 28-by-80- lambda elliptical Cassegrain antenna operating at a wavelength of 3 mm. The design process for designing the feed system is discussed in detail. Despite the small size and relatively large aperture blockage, an aperture efficiency of 0.48 was measured, which compared quite well with the expected efficiency of 0.53, thus verifying the validity of the Gaussian beam design approach. >

Anti-icing and de-icing system for reflector-type microwave antennas

Abstract: An improved anti-icing and de-icing system is provided for reflector-type microwave antennas having a paraboloidal reflector and an associated feed horn for launching microwave signals onto the reflector and receiving microwave signals from the reflector. The improved system comprises a non-conductive, insulated enclosure forming an enclosed cavity adjacent the rear side of the reflector, and a radiant heating system disposed within the enclosure for heating the rear side of the reflector with radiant energy, whereby the air in said cavity is in turn heated by heat transferred to said air from the rear side of the reflector. The radiant heating system comprises at least one infra-red heating source, and is supplemented by a highly reflective mirror coating disposed on the inside surface of the insulated enclosure behind the heating source to direct the radiant energy emanating from the back of the heating source of all regions of the reflector. Sections of highly reflective mirror coating are also provided in regions of the rear surface of the reflector immediately opposing the front side of the heating source to divert excess radiant energy emanating from the front of the heating source and disperse it to all regions of the reflector.

Polarization diversity radio communication system

Abstract: PURPOSE: To attain the miniaturization of a receiver and a large S/N by sending a series of data by selecting plural transmission antennas with different main polarizing components sequentially from a transmitter, and reproducing a data group by receiving them by the receiver. CONSTITUTION: The plural transmission antennas 11H and 11V with the different main polarizing components are provided at the transmitter 10, and a series of data groups are transmitted at least for one time by selecting the antennas 11H and 11V sequentially by a switching circuit 12. The receiver 20 receives the data group at least for one time, and processes and reproduces it at a processing circuit 25. Therefore, it is enough to provide one reception antenna 21 at the receiver 20. In other words, the receiver 20 including the reception antenna 21 can be miniaturized, and a polarization diversity system is constituted by providing the plural transmission antennas 11H and 11V. Thereby, no switching means and synthetic means are required at the receiver 20, and since the antenna switching circuit 12 is provided at the transmitter 10, the S/N can be taken widely. COPYRIGHT: (C)1990,JPO&Japio

A Broadband Coaxial Ridged Horn Antenna

Abstract: The bandwidth of a circular ora rectangular waveguide can he enhanced by introducing ridges into the waveguide. In this work, ridges are introduced into the coaxial waveguide with the same intention. Simple formulae are given to calculate the cut-off frequencies of the coaxial ridge waveguide. Several set of curves are presented for the cut-off frequencies. Also, a coaxial ridge horn antenna is designed and the measured results are presented. By a multi-coaxial feed of the horn antenna dual polarization or circular polarization can be obtained without significant1y affecting the bandwidth of the antenna. The advantange of this anttenna over conventional circular or rectangular quadruple ridged antenna is that the feed points being in the same plane without any crossing, the ridge gaps can be decreased to enhance the bandwidth. Also thee power handling capability is expected in be better.

Radiation properties of parabolic torus reflector

Abstract: General radiation-pattern formulas for a torus reflector antenna have been developed using physical optics. These expressions are valid at arbitrary feed locations not only within the primary focal arc but also for beam scanning with squinted feed horn illuminations. Numerical results were obtained at 22 GHz for an experimental 1.25 m*2.5 m torus reflector in both elevational beam scanning and extended azimuthal scanning outside the primary +or-15 degrees field of view. An elevation scanning range of 7 degrees showed only a 1 dB gain reduction. The 20 degrees azimuth beam (i.e. 5 degrees extended azimuth scanning) showed a 1.4 dB gain reduction. Comparison between calculated and measured patterns showed agreement in beamwidth and most pattern features. The discrepancy between calculated and measured sidelobe levels in the azimuthal plane is attributed to imperfection enhancement by the horizontal oversize of the reflector. >

Dual channel 115 and 230 GHz SIS receivers in operation at the Owens Valley Radio Observatory

Abstract: The Owens Valley Radio Observatory millimeter-wave interferometer array is presently operating with dual-channel SIS (superconductor-insulator-superconductor) tunnel junction receivers. The first channel covers the frequency range from 85 to 120 GHz and the second channel covers the frequency range from 200 to 300 GHz. The mixers consist of a corrugated feed horn, a single-stage circular-to-rectangular waveguide transition a reduced-height waveguide with an SIS junction mounted across the E-plane, and a non-contacting backshort. The mixer block has a built-in RF choke for the IF (intermediate frequency) signal path which is designed to present a short circuit to the junction at frequencies above the 2-GHz IF frequency. The small-area ( >

Efficient small reflector with hat feed

Abstract: The hat feed is a new axially self-supported feed for a single-reflector antenna. The advantage of it is that the outer surface of the axial waveguide is used as a desired radiating element, and thereby it does not cause an undesired blocking of the aperture like in other self-supported feeds. The authors present a hat feed at 15 GHz in a deep reflector with 43 cm diameter. The reflector is so deep that a plane radome can be mounted across the aperture. The antenna efficiency including mismatch is larger than 60% over a 6% bandwidth, and the sidelobes are extremely low.

Communication Antenna Subsystem for the Chinese Satellite DFH-3

Abstract: The development of a C-Band contoured beam antenna for the coverage of the People's Republic of China is described. The antenna applies two polarisation sensitive reflector shells which are mounted behind each other. The orthogonally gridded reflectos of 2 m diameter are fed by two 7-horn clusters of corresponding linear polarisations, providing both combined transmit (3.7 - 4.2 GHz) and receive (5.925 - 6.425 GHz) functions. Each array consists of diagonal horns followed by waveguide diplexers which are fed by two beamforming networks (Tx and Rx respectively) in coaxial technique (barline). A dual mode transmit network provides two independent input ports. The engineering model of this antenna will be completed in 1989. First breadboard results of the most critical components of the feedsystem are given.

Parabolic antenna for shf

Abstract: PURPOSE: To minimize the deterioration in the electric characteristic due to a dielectric plate by adopting a double structure for a dielectric cap so as to adjust the interval of the dielectric material plates. CONSTITUTION: A double structure comprising 1st and 2nd dielectric plates 2a, 2b is adopted for a cap part covering the tip opening of a horn of a dielectric resin cap 2. The interval L between the dielectric plates is adjusted so as to make reflected waves R 1 and R 3 opposite in the phase, where R 1 is a reflected wave caused by the 1st dielectric plate 2a, R 2 is a reflected wave caused in the 2nd dielectric plate 2b and R 3 is a reflected wave R 2 passing through the 1st dielectric plate 2a. Thus, the reflected waves are cancelled and the effect of the cap is eliminated. Then the electric characteristic deterioration of a feed horn due to the cap is minimized. COPYRIGHT: (C)1991,JPO&Japio

Off‐axis performance of shaped antennas at millimeter wavelengths

Abstract: Antennas which have been shaped for optimal aperture efficiency will not give sharp off-axis images. This is true for even quite small fields of view. The shaping to match feed horn illumination is at fault here; it leads inevitably to severe coma and curvature of the field. The analysis presented here is based upon geometrical optical computations.

A compact EHF/SHF dual-band reflector antenna

Abstract: A new 5.5-in. diameter EHF/SHF dual-band reflector antenna was developed as an earth terminal for satellite communication. With minimal changes from an old design, this new design demonstrates significantly higher antenna efficiencies at both hands. The original design was a 5.5-in. diameter parabolic main reflector with a 1.87-in. focal length. One of the criteria for the new design is that the main reflector must stay the same. The single-shaped configuration with a parabolic main reflector and shaped subreflector turned out to be an excellent choice for this case. A test model was built and tested. Antenna gains of 27.0 dB at 20.7 GHz and 33.3 dB at 44.5 GHz, which are at least 0.5 dB higher than the antenna gain requirements, were obtained. >

A general and effective approach to the synthesis of shaped reflector antennas

Abstract: Starting from the analytical properties of the scattered fields, a complete and simple operational relationship is established between the primary field and the secondary one. On this basis the reflector shape and the far field of the feed system are synthesized starting from the knowledge of only the dimensions and positions of the reflector and feed region. The technique makes it possible to synthesize essentially the same pattern with different reflector-feed couples, thus allowing the effects of the reflector shaping and the primary source extension to be balanced at the designer's convenience. The technique turns out to be numerically effective, as it is based on the use of fast Fourier transforms. >

Design of elliptical and offset reflector antennas using Gaussian beam theory

Abstract: Procedures for applying Gaussian beam theory to reflector antenna design are discussed, and a suggested method for generalising inverse square law factors in a mixed Gaussian-ray geometry illustrated. These methods allow practical designs to be generated with almost negligible computation, in unusual geometries. In the practical elliptical antennas described, Gaussian beam concepts have led to a single-lens configuration, involving a real imaged waist in one plane. >

Offset parabolic reflector antenna

Abstract: An antenna for use in both C band and Ku band communications (3.65 GHz to 14.5 GHz) comprises a parabolic reflector (10) with support means (14) for mounting the antenna feed and/or receiver (13) offset relative to the aperture of the reflector. The antenna is designed such that F/D is in the range 1 to 1.12 and d/D is in the range 0.052 to 0.11, where F is the focal length, D is the diameter of the projected beam of the reflector, and d is the displacement of the projected beam edge from the focal axis of the axisymmetric parent paraboloid of the reflector. The antenna is suitably fed by a low flare angle corrugated feed horn.

Recent advances on elliptical-beamshape horns

Abstract: The crosspolar performance of horn antennas with elliptical beams, operated in dual linear or circular polarization, is discussed. Rectangular and elliptical horns based on the dielectric core approach have been designed and measured. Only linearly polarized patterns need to be measured to determine the performance when the horn is operated in circular polarization, assuming that other crosspolar sources are small. It is shown that the simple dielectric core horns potentially have a much larger crosspolar bandwidth than their corrugated counterparts (probably more than 30%). They also represent a much cheaper design. The horn approach is very critical to tolerances on the alignment of the dielectric core inside the horn and has a large mass of low frequencies. The elliptical horn exhibited lower sidelobes than the rectangular horn, which makes it more efficient for illuminating an elliptical reflector. >

Pattern diversity in a microwave digital radio system utilizing a single horn reflector antenna

Abstract: During multipath fading in a terrestrial digital radio system, off-axis arrival of signals excites higher-order modes in a horn reflector antenna. In the disclosed system specified ones of these higher-order modes and the fundamental mode are allowed to propagate in a main waveguide connected to the antenna. At least one of the higher-order modes is abstracted from the main waveguide and fed to a standby receiver while the fundamental mode is propagated intact to a main receiver. Error occurrences in the fundamental and higher-order modes due to multipath fading are substantially uncorrelated. Hence, upon detecting an error in the signals delivered to the main receiver, the system switches to the standby receiver thereby to provide in a single-antenna a significant improvement in performance against multipath fading.

Dielectric-loaded horn feeds for radiometer antenna

Abstract: The authors have developed a low-loss high-quality dielectric material that can be used in space antennas. A 7.5 degrees semi-flare angle dielectric-loaded horn is shown. The dielectric material is placed against the thin-wall metal cone of the horn and a thin layer of Left Koweld glue is used in the gap. Experimental E- and H-plane patterns of the horn antenna at 15.3 GHz are shown. The peak cross-polarization level is better than -40 dB at 6.84, 10.68, 18.7, 23.8, 36.5, and 90 GHz. Computed copolar footprints of a typical radiometer antenna using the dielectric-loaded horn feed are shown. >

An EHF omnidirectional lens antenna

Abstract: A shaped reflector antenna, illuminated by a corrugated horn, has been designed, fabricated, and tested. The test results show that the feed blockage and the strut support blockage cause performance degradation. The deficiency can be corrected by using a shaped lens, illuminated by a corrugated horn. The lens antenna avoids both the feed and the strut blockage. The lens surface is shaped to provide a nearly uniform coverage over a +or-90 degrees cone. A good axial ratio at 44 GHz is achieved by designing the corrugated horn with nearly equal E- and H-plane patterns. >

Rf equipment for satellite communication earth station

Abstract: PURPOSE:To form a small sized portable satellite communication equipment by forming the trunk cover by a transmission/reception antenna respectively, opening the cover at the communication so as to direct the antenna and a feed horn to a prescribed direction. CONSTITUTION:The RF equipment of a transmission RF equipment and the RF equipment of a reception earth station are both formed into a trunk accommodation type. Parabolic reflecting mirrors 11, 12 are placed to the part corresponding to the trunk cover and a power amplifier 7, a transmission frequency converter 9 or a low noise amplifier 8 and a reception frequency converter 10 are provided to the containing box. Then horns 21, 22 and polarized wave converters 41, 42 are removed from the trunk in the operation and placed on the upper face of the trunk in opposition to the reflecting mirror. Then the horns 21, 22, the transmission polarized wave converter 41 and the reception polarized wave receiver 42 are interconnected by a cable. Thus, small sized portable horn feeding system is formed.

Compact range design with axial-symmetric main reflector

Abstract: A design for a dual-reflector compact range system with axial-symmetric main reflector is proposed. The advantage of this design is that it provides a larger quiet zone area and reduces the manufacturing cost. The configuration consists of a large surface of revolution as primary mirror, and a conventional point-source spherical-wave feed. The point-source feed is located outside the column of parallel rays reflected from the primary mirror in the Z-axis. Using geometrical ray tracing, a subreflector contour can be generated. Since the proposed approach is based on the surface of revolution, either a paraboloid or a spherical surface can be chosen as the main reflector. >

Transmitter and antenna

Abstract: The invention relates to small low voltage transmitters for transmitting at single frequency, preferably in the VHF range, suitable for use in the location or tracking of birds, animals, vehicles, people or other objects where the transmitter is required to be small and light. The transmitter circuit includes an oscillator stage (61) based on a crystal oscillator XL1 having a predetermined nominal frequency, a frequency multiplying and amplifying circuit (62) arranged to double the nominal frequency and a pulsing circuit (60) designed to give a pulsed output at predetermined frequency, the pulsing stage (60) includes a pair of transistors TR11, TR12 having effective negative resistance, which transistors are separate from the transistor TR3 in the oscillating circuit and which are off during an Off Period and on during an On Period with the Off to On period in the ratio of at least 15 to 1. The oscillator circuit (61) includes a tuning means C3 by which the tolerances of the crystal frequency and other components of the oscillator stage can be compensated. The frequency multiplying and amplifying circuit (62) includes a distinct tuning means (66) by which the final desired frequency of the amplifyer stage can be tuned to compensate the component tolerances in the stage. The transmitter circuit together with batteries (30) are located in a casing (18, 20) all of which components weigh no more than 7 grams.

Investigation of a variable peripheral cavity feed for front-fed reflector antennas

Abstract: Presents experimental results obtained for a variable peripheral cavity waveguide feed during the investigation of small reflector antenna configurations suitable for sequential lobing and continuous beam steering tracking operation. The presented results, detailing primary and secondary, copolar, cross-polar and phase characteristics, extends the work previously published and highlights the operational capabilities of the system. >

The dielectric-filled parabola: a new high frequency integrated receiver or transmitter front end

Abstract: A design is presented for a high-frequency front end that can be used as a receiver or transmitter, in a heterodyne or direct detection mode, as a single device or in conjunction with a focal-plane array. The novel feed system combines the simplicity and robustness of a dielectric substrate lens with the high gain of a parabolic reflector in a single structure, the dielectric parabola. The design is easy to fabricate, can be scaled to very high frequencies, and is cryogenically coolable. Beam patterns and antenna input impedances have been measured for a number of different planar antenna elements on the dielectric-filled parabola from 4 to 12 GHz. The results of these measurements show clearly that the system performs well. >

Adaptive beamforming using multimode feed horn antennas

Abstract: The authors develop a new model for implementing adaptive nulling of interfering signals which is based solely on a single-feed horn antenna. The model uses a multimode feed antenna in which various modes are generated or extracted by means of slot coupling. Adaptive nulling is then carried out by treating each mode as an element of a phased-array antenna. The algorithm that is used to implement the adaptive nulling relies quite heavily on the QR decomposition method, a recursive least-squares algorithm which is amenable to systolic array processing. With proper choice of modes and design parameters for the feed horn antenna, simulation studies show that wide beamwidths (bandwidth), low sidelobe levels, and high signal-to-noise and interference ratio can be achieved with the proposed adaptive beamforming technique. >

Alternate bi-directional (half-duplex) radio link system with sub-carrier modulation

Abstract: The invention relates to an alternate bi-directional (half-duplex) radio link system with sub-carrier modulation. The system includes first transmitter/receiver means 1 and second transmitter/receiver means 2. For transmitting messages, the transmitter/receiver means 1 transmit a continuous UHF wave towards the transmitter/receiver means 2, which reflect the abovementioned electromagnetic wave towards the transmitter/receiver means 1, while performing sub-carrier modulation at intermediate frequency by means of a modulator 52110, 5211. Detection of the standing wave system created as a result of the transmission of the electromagnetic wave and of the reflection of the latter towards the transmitter/receiver means 1, is performed by means of two detection diodes 5161, 5162, offset by an odd multiple of quarter wavelengths in the direction of propagation of the electromagnetic wave in the waveguide feeding the antenna 515 of the first transmitter/receiver means 1. Logic processing 514 makes it possible to recover the binary modulation signal constituting the message transmitted by the transmitter/receiver means 2. Application to the exchange of bidirectional messages between one or more vehicles and a point which is fixed or itself mobile.

Dielectric loaded horn feed arrays for reflections in shaped beam applications

Abstract: With satellite applications in mind, the authors have analyzed an array of dielectric loaded horns. They outline some of the methods used and present preliminary results, including a shaped beam for an AUSSAT satellite. Reflection and mutual coupling, dielectric loss, and radiation are considered. The horn analysis software was used to design a shaped beam to cover New Zealand from the AUSSAT geostationary positions of 156 degrees E and 160 degrees E. An optimized transit beam at 12.5 GHz, obtained with a 1.5-m offset parabolic reflector and a seven-element feed array, is shown. >