Abstract: In a flat plate antenna, insertion loss is reduced significantly by providing an extensive waveguide structure at the back of the ground plane of the antenna. Depending on antenna size, the waveguide may feed the antenna at one or a plurality of points. According to a preferred embodiment, the transition from waveguide to stripline is made via a coaxial connection, with a quarter-wave transformation, including mode suppression walls to direct the energy more efficiently. Alternatively, a direct waveguide to stripline transition may be provided. The technique has wide applicability to a number of antenna designs, including single- and dual-polarization structures, and linear and circular polarization operation.

Abstract: 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.

Abstract: 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.

Abstract: In antenna arrays having normally unexcited or little-excited elements, a technique for configuring the array to provide both global and spot beam coverage, wherein the normally unexcited or little-excited elements are excited at a higher level, together with other normally excited elements to provide spot beam coverage, the normally unexcited elements being left unexcited to provide global beam coverage. Ring redundancy configurations for amplifiers in a transponder provided in the configuration are optimized to minimize additional hardware requirements. The specific example of the INMARSAT II satellite system is discussed.

Abstract: 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.

Abstract: 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.

Abstract: 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.