Abstract: A satellite orientation detection system disposed to detect the pointing orientation of a geosynchronous satellite (10) relative to a reference location on the earth. The present invention is also capable of ascertaining the angular orientation of a longitudinal axis of the satellite (10) relative to a defined axis on the surface of the earth. A ground station (20) is included for transmitting a first linearly polarized and a second circularly polarized electromagnetic reference beam. The present system also includes a receive antenna (28) coupled to the satellite (10) for receiving the first and second reference beams and for generating an antenna-beam pattern P1 and P2 disposed to rotate about a reference axis A. A rotating polarizer arrangement (44), aligned with the receive antenna (28), periodically varies the portion of the linearly polarized energy within the first reference beam transmitted thereby.

Abstract: In a cross-polarization interference canceller employing a transversal filter, when a tap coefficient of the transversal filter is generated by averaging resultant values of correlation between a residual error component and a data polarity signal of a different polarized wave, a moving average derived by averaging with a sum of most recent given number of bits of correlation results, is employed. Even when offset is caused on the correlation results due to random characteristics of the received signal, the offset cannot be accumulated to allow derivation of the true tap coefficient since the sum of most recent given number of bits of correlation results is used.

Abstract: A dual linearly-polarized cross-correlating radiometer including an apparatus for calibrating the cross-correlating channel of the radiometer is described. The apparatus for calibrating the cross-correlating channel comprises a first calibration load, a second calibration load positioned perpendicularly thereto, and means for rotating the calibration loads relative to the feedhorn of the radiometer. The calibration loads are moved through several angular positions and the output voltages of the cross-correlating channel are measured at the various angular positions and used to estimate the gains and offset of the cross-correlating channel.

Abstract: In a cross-polarization interference conceller for use in a digital radio communication system which transmits digital modulated signals over radio frequencies having planes of polarization orthogonal to each other, signals from the interfering polarized wave are sampled with a frequency equal to double the frequency of the affected polarized wave and, after latching the sampled signals with the frequency of the symbol rate, interference cancelling signals are generated by adding the products of their multiplication with control signals. Therefore, the digital multipliers and the digital adders for generating the interference cancelling signals can be operated at low speed.

Abstract: An adaptive polarization combining system automatically adjusts the polarization of a polarization diverse antenna to match that of the incoming RF signal, thereby maximizing the received signal-to-noise ratio. Signals from the orthogonally polarized ports of the antenna are passed through a variable combiner circuit which is adjusted to maximize the combined signal at a single output port. Sample signals from each antenna port are provided to a calibration circuit which obtains phase and amplitude information from the two orthogonally polarized received signals and uses this information to control the combiner circuit phase shifters to adapt the combiner circuit to the polarization of the received signals. Therefore, the combining system can rapidly adapt electronically to polarization changes in the received signals.

Abstract: In a preferred embodiment, the disclosed system is part of a communication system (10) formed by a satellite (12) and aircraft (14). The system includes a controllable antenna network (16) and polarization tracking network (18). The controllable antenna network includes an array (28) of orthogonal antenna pairs (34) whose beams are steerable by phase shifters (46) to correct for changes in the aircraft's attitude. Similarly, amplifier circuits (44) compensate for changes that would otherwise occur in the signal-to-noise ratio of the antenna's output. The polarization tracking network includes a forward section (62), defined by quadrature hybrids (66) and (70) and an adjustable phase shifter (68), and a feedback section (64) that monitors each polarity for the presence of a single select channel. The phase shifter responds to the comparison made by a phase detector (86) in the feedback section to maintain the desired polarization of all channels.

Abstract: In a cross-polarization interference cancellation system operable in response to desired and undesired or interference source signals which are obtained from polarized waves having planes of polarization orthogonal to each other and which are produced in accordance with clock signals having a predetermined clock frequency, an interference signal is included in the desired signal and is derived from the interference source signal to be removed from the desired signal by the use of an interference canceller and to be produced as an interference free signal. The interference free signal is demodulated into demodulated signals, error signals, and quadrant detection signals by a demodulator unit. In this event, the quadrant detection signals alone are stably demodulated by the use of specific clock signals which are sent through a frequency doubler operable to double the predetermined clock frequency of the clock signals.

Abstract: In a digital radio transmission system for transmitting independent dual data by using cross polarization, an interference canceller detects cross polarization interference either directly or indirectly. An interference compensating signal is generated and applied to the main signal to cancel the interference element. In a case where no interference element is present, deterioration of cross polarization discrimination from an interference cancelling circuit is prevented by first determining whether an interference element actually exists and applying the interference compensating signal only when it does exist. The interference compensating signal can be attenuated based on the value of interference element so as to prevent undo deterioration of the cross polarization discrimination when the interference element is minimal.

Abstract: The invention provides a master controller to store and call up on command a plurality of setups for numerous satellites. An antenna is directed to a desired satellite, the polarization of the feed horn is changed to that of the signal to be received and a receiver or receivers are switched to the proper band, C or Ku. A transponder is selected as are audio and/or video frequencies, half or full transponder modes in the Ku band, and video reverse. The setup is recalled by an operator or by a timer which can call or set up at prescribed periodic intervals or on a one-time basis. An operator can change one or more parameters of a specific setup.

Abstract: A satellite TV receiver for receiving a satellite broadcasting, wherein neighboring televison signals are vertical and horizontal polarized waves, and wherein a polarizer for the satellite receiver controls an antenna so that the polarization plane of the antenna is adapted to the polarization plane of television signal to be received. The receiver further includes a narrow band-pass filter for rejecting terrestrial interference so that the desired polarization plane can be more easily determined.

Abstract: In a TVRO earth station having an antenna for receiving incoming satellite signals and polarizing means associated with the antenna for adjusting the relative alignment of the antenna orientation and the polarization of the incoming signals, an automatic polarization control system comprising means for producing an electrical control signal for controlling the polarizing means to adjust the relative alignment, means for detecting the noise level in the satellite signals received by the antenna, and means responsive to the detected noise level for adjusting the control signal, and thereby adjusting the polarizing means, to minimize the detected noise level.

Abstract: An improved decision-directed control circuit is disclosed which supplies adjustments to adaptive circuitry in a communications system. The improvement is achieved by only supplying adjustments when there is a high probability that the adjustment is correct. In the disclosed embodiments, this high probability equates, at a minimum, to times when the adaptive circuit output has an amplitude which lies outside of a range extending from the largest to the smallest value of the digital signal. This adjustment approach can be used to adjust a variety of adaptive circuits including transversal equalizers, timing recovery circuits, cross-polarization cancellers and carrier recovery circuits.

Abstract: A process and apparatus for the day-or-night monitoring of weather phenomena by means of the analysis of the movements of air masses, wherein the movements are determined by monitoring and receiving the multi-band VLF electromagnetic radiation generated in the atmosphere with directionally selective receivers. The received frequencies are then compared with values which have been correlated with atmospheric events. Means are provided for displaying the predictive results for events occurring up to 500 km away from the VLF receivers--typically updatable within seconds--in at least two stages according to the (near or far) range desired or the type of electrical polarization.