Communications Satellite Corporation

Arnold L Berman

Francois T Assal

Christoph E Mahle

Ali E Atia

Tsvi F Assal

Janaki R Potukuchi

Marvin R Wachs

Cristoph Erhardt Mahle

Khodadad Betaharon

A method of measuring input-backoff to an amplifier in a time-division multiple access (TDMA) communication system having a carrier recovery segment and a clock recovery segment prior to a data segment in a traffic burst. A monitoring station transmits a CW pilot signal within the amplifier's bandwidth. In the guard time between bursts, the monitoring station measures the unsuppressed pilot level output by the amplifier. While a ground station is transmitting an unmodulated carrier during carrier recovery or a carrier modulated at the clock frequency during clock recovery, the monitoring station measures the suppressed pilot level, suppressed by the non-linear interaction of pilot and carrier. The amount of pilot suppression is related to the input power back-off of the carrier by a previously measured or a theoretically derived relationship. The carrier-to-suppressed noise ratio is determined by measuring the carrier level during the carrier recovery and by measuring the suppressed noise during carrier or clock recovery through a noise filter centered away from any transmitted signals or their intermodulation products.

Monitoring of input backoff in time division multiple access

A multichannel correlation receiver at an earth station is provided for determining the depolarization effects of atmospheric conditions on satellite communications. The receiver provides a first co-polarized signal and a second, relatively weak, cross-polarized signal indicative of the depolarization effects, and uses a phase locked loop demodulator to produce a noise free replica of the relatively strong co-polarized signal. This co-polarized signal is highly correlated with the second cross-polarized signal and is mixed therewith to provide a relatively noise free, narrow band signal which has a level indicative of the cross-polarization signal strength for both up-link and down-link propagation paths. The relative signal strengths are recorded on a digital storage means and provide an accurate measure of the depolarization effects of the existing atmospheric conditions. A programmable local oscillator also provides multiple channel capability.

Multichannel correlation receiver for determining depolarization of

A microwave PIN diode switch is provided with circuitry to achieve impedance matching at both input and output ports and for both 'on' and 'off' switching states.

Resistively matched microwave PIN diode switch

Frequency bands in spot beams received by a satellite transponder are selectively routed to transmitted spot beams. The total band width from each spot beam receiver is divided among a plurality of independently adjustable variable bandpass filters, and the outputs from the selected bandpass filters at each receiver are combined at the spot beam transmitters so that each downlink spectrum is made up of a frequency multiplex of selected bands from each uplink spot beam.

Communication satellite transponder interconnection utilizing variable

A temperature-compensated microwave integrated circuit device such as a delay line in which the phase delay imparted to signals coupled through the delay line is substantially constant over a wide range of temperatures. A dielectric substrate is provided, with strip conductors on one surface defining a desired device configuration such as a multi-pole Butterworth filter configuration. The substrate is enclosed within a support frame with the lower side of the substrate positioned upon the bottom surface of the enclosure forming a ground plane. A conductive plate is attached to the top cover of the enclosure through a layer of compensating material. As the temperature changes, the layer of compensating material expands or contracts, thereby varying the height of the conductive plate above the substrate, which changes the electromagnetic field pattern of signals propagating along the delay line and, consequently, the propagation velocity. The thickness and coefficient of expansion of the compensating layer are chosen to maintain the delay time through the device at a substantially constant value.

Temperature-compensated microwave integrated circuit delay line

A four-port waveguide switch is described which allows any two pairs of ports to be connected together. A separate waveguide independently connects each port with each of the remaining ports. In each of the six separate waveguides there is provided at least one resonant cavity having a passband that includes the frequencies of the incident microwave signals to be switched. A disrupting structure is provided for each resonant cavity. Each disrupting structure may be switched between a first state wherein the respective cavity is not detuned and a second state wherein the respective cavity is detuned such that it reflects the incident microwave signals. By switching the appropriate disrupting structures to their second state, any of the three possible connecting states of a four port switch of the present invention can be obtained.

Waveguide switch having four ports and three connecting states

A redundant microwave configuration providing a highly flexible routing of a plurality of inputs to a plurality of outputs is characterized by at least two switching layers wherein each switching layer comprises a plurality of four port switches and the switches in at least one of the switching layers are connected in a ring, corresponding switches in the layers being interconnected. This redundancy configuration is not limited to microwave applications only but could be implemented at all other frequencies. One microwave configuration employs 2N amplifiers between said switching layers as building blocks to provide N inputs to N antenna ports. This configuration allows any combination of (m-N) amplifier failures without loss of service, where N .ltoreq. m .ltoreq. 2N. In other configurations, only one type of switch is used and fewer than 2N amplifiers are used for N inputs and N outputs. Moreover, by properly choosing path lengths, the outputs of two or more amplifiers can be combined where greater power output is required than that provided by a single amplifier. In still other configuratons, the switching layers are directly connected, and one of the switching layers comprises a matrix of fast switching elements.

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Kensington, MD, United States of America

Arnold L Berman