Communications Satellite Corporation

Comsat Corporation

Christoph E Mahle

Francois T Assal

Arnold L Berman

William H Childs

Amir Ibrahim Zaghloul

Ramesh K Gupta

John V Evans

Ali E Atia

Tsvi F Assal

A 'modified rearrangeable' switch matrix combines both .beta. switching elements and crossbar switch matrices in a single switch configuration, with .beta. switching elements used at the input and output and at least one crossbar switch matrix in the middle to receive its inputs from .beta. switching elements and provide its outputs to .beta. switching elements.

Switch matrix including both B switching elements and crossbar switch

On-board satellite switching is performed in three stages, an outer stage of switching on the up-link side for routing the received signals to either demodulators or frequency translators, a first inner stage of switching, preferably a baseband switch and processor, for routing and processing the outputs of the demodulators, a second inner stage of switching, e.g., a microwave switch matrix, for routing the outputs of the frequency translators, and an outer stage on the down-link side for assembling and routing the down-link spot beams. For a multiple hopping-beam system, the outer stages are microwave switch matrices, and for a hybrid scanning-hopping system the outer stages are beam forming matrices. A general purpose modified rearrangeable switch matrix is also disclosed.

Multiple spot-beam systems for satellite communications

A microwave integrated circuit (MIC) quadrature phase shift keying (QPSK) modulator uses a novel arrangement of couplers to permit the IF ports to be adjacent one another so that, in mixer applications, it is unnecessary for the circuitry to leave the plane of the MIC. A symmetrical arrangement of the MIC ensures near-perfect phase orthogonality of the RF.sub.2 split and the power/phase identity of the RF.sub.1 split.

Planar QPSK demodulator

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 integrated circuit (MIC) quadrature phase shift keying (QPSK) demodulator uses a novel arrangement of couplers to permit the IF ports to be adjacent one another so that, in mixer applications, it is unnecessary for the circuitry to leave the plane of the MIC. A symmetrical arrangement of the MIC ensures near-perfect phase orthogonality of the RF.sub.2 split and the power/phase identity of the RF.sub.1 split.

A planar microwave switch matrix is composed of three-state phase shifter switches, a planar crossover and switchable 3-dB attenuators. The three-state phase shifter switches are each composed of two planar 3-dB quadrature hybrid couplers interconnected by two switchable phase shifters. The phase shifters are both switchable between zero phase delay and a predetermined phase delay, but the predetermined phase delay is different for each phase shifter. The planar crossover is composed of two cascaded 3-dB quadrature hybrid couplers. The construction of all components of the switch matrix is readily implemented using microwave integrated circuit (MIC) technology. The switch matrix is intended for use in switched satellite time division multiple access (SS-TDMA) systems but can be remotely configured for broadcast applications.

Two-dimensional (planar) TDMA/broadcast microwave switch matrix for

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.

Growing community of inventors

Washington, DC, United States of America

Christoph E Mahle