Abstract: This invention is a digital phase modulator for microwave transmitter systems. A digital signal is bandwidth limited at baseband, then is shaped to compensate for the nonlinear reflection coefficient versus bias voltage characteristics in a phase modulator. The shaped signal is applied to the phase modulator to modulate a carrier. The carrier signal is derived from a high power amplifier operating at its maximum power handling capability. Linear multiplication is then obtained, and use of linear intermediate frequency stages, up-converters as well as operation of the high powered amplifier at less than maximum power to obtain linear operation is thus avoided.

Abstract: A circuit for reducing the effects of polarization crosstalk occurring on a first RF signal due to a second RF signal, wherein the first and the second RF signals are two approximately orthogonally polarized RF signals having essentially the same frequency. The circuit comprises a first antenna and a first signal path (including RF and IF sections) for the first RF signal and a second antenna and a second signal path (including RF and IF sections) for the second RF signals. A first coupler diverts a portion of the signal on the second signal path into a first network comprising the series combination of a variable attenuator and a variable phase shifter. A summing circuit sums both the signal on the first signal path and the signal output from the first network with the result that the undesired signal on the first signal path is reduced. A logic circuit, responsive to the magnitude of one of the RF signals, controls the first network according to a predetermined relationship.