| 摘要 |
1497430 Stand by facilities in satellite communication system earth stations; parametric amplifiers COMMUNICATIONS SATELLITE CORP 12 May 1975 [31 May 1974] 19874/75 Headings H4L and H3X An earth terminal for transmitting data to and receiving data from two or more earth orbiting satellites in a satellite communication system incorporates: (a) an antenna 11 with a fixed reflector apparatus and a separate feed, e.g. 12 1 , 12 2 for each satellite with which the terminal communicates; (b) a transmitter for each separate antenna feed, including a number of identical high power amplifiers, e.g. 22 1 , 22 2 , 30, exceeding the number of communication channels, the band width of each amplifier being equal to or slightly greater than the total satellite communication band, a modular filter matrix 24 divided into the same number of contiguous frequency bands as the number of channels, and switching arrangements 31 for connecting amplifiers to the channels of the filter matrix, the remaining amplifiers being spares which can be substituted by the switching arrangement when any amplifier fails; (c) a low noise receiver 15 connected to each separate antenna feed, including an uncooled parametric amplifier having independent identical interchangeable parametric amplifier modules connected in cascade by an integrated multi-port microwave circulator, whereby the modules can be removed and replaced without interruption to service. The terminal may transmit and receive two orthogonal polarizations, and the antenna may then include a polarizer and orthomode transducer 14 connected to each separate feed to isolate the orthogonally polarized transmit and receive signals. The feeds 12 1 , 12 2 &c. for the separate satellites may be horns which are positioned and steered to a limited extent to follow the satellite by a sliding carriage 52 controlled from the central control facility 43. The receiver may incorporate a parallel redundant transistor amplifier coupled to the parametric amplifier output, followed by a frequency demultiplexer 16, each channel thereafter incorporating a down converter 17, IF filter 18, demodulator 20 and baseband processor 21. The transmitter incorporates complementary components 33, 34, 35, 36. Monitor and control arrangements 44, 45, 46 connected to the transmitter and low noise receiver transmit operating data over one of the communication links to a central monitoring and control facility. Parametric amplifier (Fig. 2) incorporates a succession of circulators, to an input of the first of which, 102 1 , the received signal input is applied. The second arm of this has coupled to it a varactor diode modulator 105, supplied from a Gunn oscillator 104. The third, output, arm of the circulator supplies a further identical stage based on circulator 102 3 via an isolating circulator 102 2 . The amplifier contains a further stage similarly arranged. If any stage becomes inoperative, the amplifier continues to function, albeit at slightly lower efficiency. |
