Showing papers on "Feed horn published in 1987"

Feed horn for a telecommunications antenna

Abstract: A feed horn comprising a radiating portion having a circular aperture, a transition formed by progressively varying waveguide sections and a flange which provides a coupling with a rectangular waveguide is fabricated from moldable material and designed to be fixed in a support. The radiating portion of the horn is formed by a cylindrical flange having at least two concentric grooves which form two traps.

Computer controlled broadband receiver

Abstract: A programmable signal receiver for use in a computer system. The signal receiver is located inside the computer's chassis and has an interface directly coupled to the computer's bus for receiving instruction signals which specify one or more channels to be selected from a broadband input signal. Each selected channel of the broadband signal is amplified using amplifying circuitry of sufficiently low impedance that the RF radiation produced does not interfere with the operation of the computer system. In one embodiment the signal receiver's input port is d.c. coupled to the computer's d.c. power supply so that the computer's d.c. power supply can be used to provide power to apparatus external to said computer system--such as a satellite dish's feed horn.

Reconfigurable beam-forming network that provides in- phase power to each region

Abstract: A reconfigurable beam-forming network for use with a transmitter has a waveguide R-switch that is interconnected with a Magic T. The R-switch contains phasing elements and is connected to a dual-mode power-­dividing network, which in turn is connected to first, second and third region power-dividing networks, each having their own feed horn array. The R-switch can be moved to three different positions so that in a first position power is divided between two input ports of the dual-mode network on substantially a fifty-fifty basis with the power on the two input ports being out of phase on a positive basis. In a second position of the R-switch, power is also divided on substantially a fifty-fifty basis between the two input ports but the power is out of phase between the two ports on a negative basis. In a third position of the R-switch, substantially all of the power entering the R-switch is passed into the first input port of the dual-mode network. The power being fed to the feed horns of any one of the regions has the same phase. In a variation of the invention, the R-switch and Magic T are replaced by a variable phase shifter and Magic T.

Horn antenna array phase matched over large bandwidths

Abstract: An array of horn antennas with non-uniform aperture sizes is disclosed wherein the individual horns phase track over a wide frequency band. The horn with the smallest aperture is considered the reference horn, and its length defines the overall horn length of the other horn in the array. The flare lengths of the other horns of the array are less than the length of the reference horn, and lengths of waveguide are added to the other horns such that the respective combined flare lengths and waveguide lengths of each of the other horns equals the horn length of the reference horn. The respective lengths of the flare and the waveguide section are chosen such that the resultant horn antenna phase tracks the reference horn over the frequency band. Therefore, horn antennas of various aperture sizes, and restricted to a maximum length can be phase matched over a band of frequencies by reducing the flared length of each horn in relation to that of the smallest or reference horn, and making up the resulting length difference by a waveguide section.

Supporting structure for reflector-type microwave antennas

Abstract: A reflector-type microwave antenna includes a paraboloidal reflector and a feed horn located at the focal point of the reflector for launching microwave signals onto the reflector and receiving microwave signals from the reflector. A supporting frame for the reflector and feed horn includes three arms extending along the rear side of the reflector to three spaced mounting locations on the rear side of the reflector. The arms are fastened to the spaced mounting locations on the rear side of the reflector by fastening means having a loose condition in which the arm is attached to the reflector but free to move relative to the reflector, and a tightened condition in which the respective arm is rigidly attached to the reflector. The fastening also includes swivel means for permitting tilting movement of the arm relative to the reflector surface when the fastening means is in the loose condition, and permitting the arm to assume different positions relative to the reflector when the fastening means is in the tightened condition. In its preferred form, the fastening means includes a cupped member having a peripheral flange secured to the rear side of the reflector so that forces transmitted between the respective arms and the reflector are distributed over the area of the reflector encompassed by the flanges.

Reflector antenna for telecommunications

Abstract: A telecommunications antenna is provided with a reflector having a semi-offset geometry, a feed mounted on a feed source rigidly fixed to the reflector, an antenna pedestal for supporting the reflector and the feed. Positioning of the feed is such that, in respect of a reflector illumination half-angle β as seen from the feed such that 45°<β<55°, the offset angle α (angle between the focal axis ΔFoc and the median ray of the total beam which is emitted by the feed and illuminates the reflector) is 25°<α<35°, the antenna mount being of the azimuth-elevation type known as an az-el mount.

Antenna exciter for at least two different frequency bands

Abstract: An antenna exciter for two different frequency bands which consists of two polarization switches (3, 4) arranged axially one behind the other and of a feed horn (5). The polarization switches (3, 4) are circular tubes of different inside diameters, the diameters being the same over the entire length. To each polarization switch (3, 4) there can be connected, spaced axially from each other, two wave guides (6, 7, 8, 9) 90° apart from each other. Opposite the wave guide (9) adjacent the feed horn (5) a stop closed by a short-circuit plate (12) is arranged in the corresponding polarization switch (4). Between the feed horn (5) and the adjacent wave guide (9) and between the points of connection of the two wave guides (8, 9) of the larger polarization switch (4), two axially extending webs lying diametrically opposite each other and of a predetermined dimension are arranged therein.

Spacecraft Multi-Beam and Contoured-Beam Antennas

Abstract: : High-gain spacecraft antennas with multiple beams and contoured beams are key components in satellite communications and direct broadcast systems. This is reflected on the latest generation of communications satellites, where the antenna subsystem is the largest subsystem with its weight of more than 300 kg. The antennas achieve a large communications capacity through multiple frequency re-uses and may be reconfigured to serve different coverage areas. The paper overviews the current multi-beam and contoured-beam antenna technology. Different implementations, reflector or lens with feed array or direct radiating array, are considered. The emphasis is placed upon systems with offset paraboloidial reflectors. The limitations of the offset reflector with respect to beam scanning and cross polarization are reviewed. computer-aided design procedures and design examples are presented.

Composite antenna reflector with polarized subreflector

Abstract: A composite reflector structure (28) for a spacecraft antenna system (20, 50) is formed of a honeycomb material, transparent to electromagnetic radiation, and having inner and outer arcuate surfaces (30, 32) substantially uniformly spaced apart and carrying corresponding sets of inner and outer reflective elements (68). The sets of reflective elements (68) comprise parallel strips of electrically conductive material (72), the strips on the inner surface (30) being perpendicular to the strips on the outer surface (32). The two sets of reflective elements (68) having sufficient spacing therebetween to provide adequate rigidity to the supporting structure (62). A pair of feed horns (40, 42) illuminate the reflectors (68) via a subreflector (44) having a polarization sensitive surface which reflects electromagnetic waves having a polarization of one plane while being transmissive to radiation having polarization in a perpendicular plane. This arrangement of the components of the antenna system permits the feed horns (40, 42) to be individually positioned at both sides of the respective reflectors while retaining decoupled independent transmission of cross-polarized signals, and reducing overall weight while maintaining adequate rigidity to the entire structure. Each feed horn (40, 42) may be replaced by an array of feed horns having the same polarization as the horn they replaced.

Radio transmitter arrangements

Abstract: In a cordless telephone arrangement in which a plurality of radio transmitters are required to transmit modulated radio-frequency signals by way of a common antenna, each transmitter has its output connected to a common path to the antenna by way of a respective directional coupler.

Closer spacing of geostationary satellites through adaptive nulling at the ground terminal

Abstract: The results of a preliminary study suggest that interference to the downlink of one geostationary satellite from that of another satellite in the adjacent orbital slot can be substantially reduced by the addition of a simple adaptive nulling system to the ground terminal antenna. Alternatively, the nulling system allows the satellites to be spaced significantly closer together with no increase in interference. Significant improvement is obtained with simple open-loop antenna pointing. The improvement is greater, however, if the adaptive antenna automatically tracks the direction of the desired source. For a dish antenna with a single receiving feed horn, the extra hardware required to provide the adaptive capability consists of two more receiving feed horns, a variable weighting device for each of the feed lines (now three in number) and the adaptive control electronics. An example shows that the minimum spacing between one satellite and an interfering satellite, consistent with certain assumed operating requirements, could be reduced from the 2.25\deg needed for a simple single beam antenna to 1.35\deg , for the adaptive antenna using open loop pointing, to as little as 0.7\deg , for the adaptive antenna using automatic pointing. The adaptive hulling also provides essentially the same protection against downlink interference from the two other satellites occupying the slots on both sides of the satellite serving the terminal. The three degrees of freedom of the postulated nulling system, however, cannot cope with three or more nearby interfering satellites.

Spacecraft Antenna Design using Optimisation

Abstract: The design of shaped-beam antennas suitable for satellite broadcasting and satellite communication is described. The method employs an optimisation search routine in which the reflector shape is varied and the antenna far-field is compared at sample points to the desired far-field. Three examples are given corresponding to the CONDOR, EUTELSAT 2 and AFSAT Satellites. In the latter it is found that two feeds are needed in order to meet the specification and their excitation is included in the search in addition to the reflector shape. As far as is known this is the first time a shaped reflector and a small array have been used together to meet intricate pattern requirements.

A Reconfigurable Satellite Antenna System for Regional and Domestic Communications in Africa

Abstract: An antenna system is proposed for a C-band African communication satellite (AFSAT). The design consists of a pair of TX and RX antennas (4/6 GHz) based on dep1oyab1e dual gridded reflectors having diameters of 2.3 m and 1.4 m respectively with a total of 100 horns. The design of the antennas is compatible with the Eurostar bus and Ariane IV Spelda 10 launcher. Eight shaped beams are formed (2 UP-link, 6 DN-link) by using orthogonal linear polarizations. Reconfigurability is allowed for most of the 24 channels (40 MHz each). A 12 horn feed array system, based on light weight stepped horns and dual mode "TEM line" Beam Forming Network, has been developed and tested.

Beam waveguides in the Deep Space Network

Abstract: A beam waveguide is a mechanism for guiding electromagnetic radiation from one part of an antenna to another through a series of reflectors. Appropriate placement of reflectors on an antenna allows a beam to be guided around the elevation axis and/or below the alidade. The beam waveguide permits placement of all electronics in a room on the alidade below the elevation axis, or below the alidade; feed horn covers to be protected from the weather; and feed electronics to be in spacious rooms rather than in crowded cones, and always level rather than tipping with change in elevation angle. These factors can lead to lower costs in implementation such as Ka-band, better antenna performance at X-band, more efficient and stable performance of transmitters and receivers, and lower maintenance and operating costs. Studies are underway to determine methods for converting the major antennas of the Deep Space Network (DSN) to beam waveguide operations by 1995.

A protective cover for an antenna feed

Abstract: An offset Gregorian antenna has a protective cover (11) fitted around its feed horn (5) and sub-reflector (4). The cover (11) has a hole (9) coincident with the focal region of the main reflector thereby allowing passage of radiation between the main and sub-reflectors (3,4) whilst preventing substantial ingress of rain and other precipitation.

Modification of Parabolic Dish Antenna Pattern Using Two Symmetrically Placed Circular Flat Plates.

Abstract: : This study aims to formulate a method of predicting the far field pattern of a parabolic dish antenna with two moveable flat plates mounted symmetrically on either side of the feed horn. The approach taken has been to first analyze the radiation pattern of the antenna with the disks at certain heights out from the surface of the dish. To do this the near-field radiation in amplitude and phase was measured over a plane surface in the near-field and the values were then transformed into the far field using a Fast Fourier Transform. Far field pattern values of the antenna were directly measured for each setting of the plates. The results obtained from the Fast Fourier Transform of the near field data were in good agreement with the values obtained by measurement. Finally, an approximate model of the antenna was developed and implemented as a computer program. This model, while relatively unsophisticated, provided some insights into the changes in the near field phase distribution caused by the moveable circular flat plates.

94 GHz Search And Track Antenna

Abstract: An offset Cassegrain modified focal-pivot-scan monopulse antenna was designed for use with a 94 GHz search and track radar system which would be mounted on an armored vehicle. The focal-pivot-scan design provides for scanning of the main reflector about its focal point while the feed horn and subreflector remain fixed. This permits rapid beam scanning in azimuth for target acquisition while minimizing the mass that must be scanned (and the required scan motor capacity) and precludes the necessity for rotary joints with their attendant losses and possible mechanical failure. The elevation search function and tracking in both azimuth and elevation are accomplished using separate drive motors.

Linearly polarized wave receiver

Abstract: PURPOSE:To attain the reception with excellent reproducibility both horizontally and vertically polarized waves by incorporating a feed horn and an equipment main body and mounting the incorporated equipment to an antenna support via a mounting part. CONSTITUTION:A linearly polarized wave receiver 14 is equipped with an equipment main body 18 incorporating an amplifier circuit and a single probe and a feed horn 16 fixed to the main body 18. The probe is arranged coaxially to the feed horn 16. In this case, the mounting part 34 fitted turnably freely around the shaft of the feed horn 16 is provided to the antenna support 12. In switching the reception of a horizontally polarized wave or a vertically polarized wave into the reception of the vertically or the horizontally polarized wave, a motor 42 is driven and the feed horn 16 has only to be driven by 90 deg.. Thus, the reception with excellent reproducibility is attained for both the horizontally and vertically polarized waves.

Device for adjusting the polarization of an antenna and a method for the practical application of said device

Abstract: A device for adjusting the polarization of a rotatable-feed antenna with respect to a reference plane makes use for an angular reference device located near the feed-horn aperture. The angular reference device consists of a tilting mercury switch having spaced contacts bridged by a mass of mercury and rigidly fixed to the feed horn. The adjusting device includes a connector located at the rear of the antenna in a zone which is accessible for adjustment and a multiple-conductor cable establishing an electrical connection between the contacts and the connector in order to provide an electrical link between the angular reference device and a visual display device.

Arrangement for transmitting radio signals

Abstract: A spatially limited radio system for simplex communication with simplex frequencies contains a receiver and a transmitter which is AF-connected to the receiver, which in each case exhibit their own leaky-cable antennas, the spacing of the cables or respectively of the transmitter and of the receiver being selected in such a manner that cross-coupling is avoided.

Distress communication method by geostationary satellite

Abstract: PURPOSE:To detect a distressed position by utilizing a geostationary satellite by obtaining information of said position from a reception power level of a distress signal radio wave at each multi-beam antenna even when no distressed position information is sent from a transmitter of a wrecked ship. CONSTITUTION:When a wrecked ship exists in a beam irradiation area of an antenna beam 13-i and when a distress signal from a transmitter of the wrecked ship is found out, the distress signal radio wave is caught by the antenna beam 13-i, the signal passes through a feed horn 17-i, received and detected by a receiver 18-i and converted into a reception power level signal and inputted to a signal processing circuit 19. The signal processing circuit 19 applies A/D conversion signal to each reception power level signal and sends the result to an earth station 9 in a signal format corresponding to each antenna beam. Since the sending point of the distress signal exists in the beam irradia tion area of the antenna beam having the maximum reception power level, the earth station finds out the distressed position.

Optical method for searching for, and suitability testing of, locations for satellite receiving antennas

Abstract: The method is used by the erectors of parabolic reflector antennas to find the correct location for an antenna, especially for those for private domestic reception from direct-broadcast radio and television satellites. Depending on the apparatus design, it is thus also possible to align the parabolic reflector to the satellite. The apparatus enables an aimed sectional view of the location (which is known in terms of direction and inclination angle) of the invisible satellite and thus indicates possible obstructions.

A dual polarized line source feed for cylindrical reflector antennas

Abstract: A line source feed for an offset cylindrical parabolic reflector antenna is described. The line source consists of two transverse and longitudinal dipole arrays over a ground plane. The elements of each array are fed separately from a feed waveguide through a coaxial line which is connected to a probe inserted into the waveguide. Within each waveguide these probes form a tapered array. The probes are treated as an N-port network to determine their penetration depth for a required Taylor distribution along the line source. The line source is then constructed and tested for both aperture field distribution and the input impedance. Its performance as a feed for an offset cylindrical parabolic reflector antenna is also studied.

Shaped-beam antennas for hybrid communication satellites

Abstract: The design of a hybrid C-band and K-band communications system for use in space has been described. The .systems were designed to require minimum satellite surface without using deployable components but still providing maximum gain, cross polarization isolation, suitable pattern coverage and high reliability. The antenna systems have been successfully launched by space shuttle and the ARIANE rocket. Expectation for continued use is high.

Preset method of satellite broadcast reception system

Abstract: PURPOSE:To quicken the preset operation for selecting a satellite by applying scanning from one end to other end of an antenna turning region and moving the antenna to the turning position applying a minimum AGC voltage stored after the end of the scanning. CONSTITUTION:In depressing a preset button of a keyboard 13, a signal is sent from a signal output section of an antenna positioner 7 to a motor and an antenna reflecting plate 1 starts moving from the east to the west position. A feed horn pickup antenna starts moving from the position of 200 deg. to the position of 100 deg. for the scanning. The AGC voltage being the detection of an intermediate frequency signal is inputted to a microcomputer 19 while being voltage-ampligied and A/D-converted. The microcomputer 19 compares the AGC voltage with the AGC voltage stored in advance and the minimum voltage is rewritten and stored together with a turning angle. Then the feed horn pickup antenna is driven to the position applying a minimum value and then stopped.

Dual reflectors employing cylindrical parabolic surface as a line source

Abstract: Reflector antennas such as spherical, conical and cylindrical parabolas have the property of focusing a line source to a point at infinity. Among these configurations spherical reflectors have been studied most extensively [l], which provide a unique beam scanning property. Conical reflectors have found limited attention, but have the advantage of using a singly curved reflector [2]. The cylindrical parabolic reflectorb also employ singly curved surfaces and are studied mostly using a cylindrical parablic reflector as a line source [3].

Target detecting device

Abstract: PURPOSE:To enlarge an aperture of a reflecting mirror by using a main reflecting mirror being common to a radio wave and a light beam, and a sub-reflecting mirror for reflecting a radio wave and making a light beam transmit through, and focusing simultaneously the radio wave and the light beam to other part on the antenna aperture center axis. CONSTITUTION:A target detecting device is provided with a main reflecting mirror 1 for reflecting a radio wave and a light beam, and a sub-reflecting mirror 2 for reflecting a radio wave and making a light beam transmit through, and an optical sensor 3 converts an incident infrared ray signal to an electric signal, and outputs it to a target detecting circuit 6. A feed horn 4 radiates a transmitting output from a transmitter-receiver 5, and also, leads an incident receiving power to the transmitter- receiver 5. The transmitter-receiver 5 outputs the transmitting output to the feed horn 4, also, converts a receiving power from the feed horn 4 to a receiving signal, and outputs it to the target detecting circuit 6. The target detecting circuit 6 outputs a target detecting circuit 6. The target detecting circuit 6 outputs a target detecting signal, when one of signals from the optical sensor 3 and the transmitter-receiver 5 exceeds some prescribed time. In this way, a size in the width direction of a device can be made small, and an aperture of the reflecting mirror can be enlarged.