Abstract: An apparatus and method for efficiently implementing a satellite transceiver system comprises a digital signal processor for providing input signals to a transmitter, a vector modulator for generating a modulated signal from the input signals, and an output amplifier for amplifying the modulated signal to produce a transmit signal. The invention also includes an attenuator that samples the transmit signal to generate an error signal, a mixer that downconverts the error signal to produce a downconverted error signal, a feedback vector demodulator that demodulates the downconverted error signal to generate result signals that contain error information pertaining to the transmit signal. The digital signal processor may then compare the result signals with the input signals to responsively alter the input signals, and thereby correct for distortion in the transmit signal.

Abstract: The operating temperature of the active region of an RF semiconductor device such as a microwave hybrid circuit having a gallium arsenide field-effect transistor therein is determined by measuring signal gain of the device at variable times following application of bias voltage to the device. Bias voltage is applied in response to a constant duty cycle pulse train from which are derived a sample-and-hold command pulse and a synchronized bias control pulse.

Abstract: A field effect transistor microwave circuit device includes first and second field effect transistors having common source connections with a pair of coupled transmission lines connecting the drain of a first transistor to the source of the second transistor and the source of the first transistor to the gate of the second transistor. The cross coupled transmission lines function as a balun between the transistors. The device is formed in III-V semiconductor and has an increased operating range in microwave frequencies. In alternative embodiments, the balun is connected to the circuit output thereby permitting the cascading of a plurality of FET devices. The balun can be integrated into the device structure or connected as a discrete element in a hybrid circuit arrangement.

Abstract: A microstrip balun comprises a ceramic substrate having a ground plane on one surface and three elongated conductive strips on the opposite surface. First ends of the outer strips are interconnected with the ground plane through vias in the substrate. The unbalanced signal input is applied to the ground plane near the vias and one end of the inner strip. The other ends of the outer strips are interconnected, and the balanced signal output is taken at this interconnection and at one end of the inner strip. A portion of the ground plane beneath portions of the strips can be removed.