Hughes Aircraft Company

Hughes Electronics Corporation

David L Crampton

Arnold L Berman

John R Grebliunas

Howard T Ozaki

Joseph E Davis

A limiter for a solid state power amplifier (SSPA) protects the amplifier against large peak, short duration noise signals while controlling drive level related phase shifts. The limiter limits noise signals to a safe input level for the power output section of the SSPA. It also uses a pair of resistor networks at its input and output to dampen reflected energy and thus control drive level related phase shifts.

Solid state power amplifier with low distortion noise protection limiter

A predistortion linearizer (10) and method for distorting an AC input signal (42) to a power amplifier (24) provide a distortion to the input signal which is complementary to a distortion, in terms of gain and phase, introduced by the power amplifier as a function of signal amplitude, thereby to linearize the power amplifier. The linearizer includes a switching circuit (26, Z.sub.1 28, Z.sub.2) having an input terminal (16) and an output terminal (20) and a pair of antiparallel diodes (26, 28) connected between the input terminal and the output terminal of the switching circuit. The linearizer has also an impedance circuit (Z.sub.3) comprising solely passive electrical elements connected between the input terminal and the output terminal of the switching circuit, wherein elements of the impedance circuit have values selected to introduce the complementary distortion to the input signal as a function of amplitude of the input signal to linearize the power amplifier.

Microwave predistortion linearizer

RF power is sampled and measured at the input and output of a solid state power amplifier using directional couplers and matched square law detectors. Outputs from the detectors are applied to differential inputs of a DC operational amplifier. Outputs from the detectors are compared and filtered in the operational amplifier and the resulting difference signal is applied to a control input on a switching type power supply. The power supply converts a DC input voltage to the various positive and negative voltages required to operate the RF devices in the solid state power amplifier. When the control loop is closed, the supply voltage varies to maintain a constant operating point resulting in constant gain, efficiency, and linearity for the overall solid state power amplifier despite variations in signal levels and signal composition. In another embodiment, the solid state power amplifier has a series of single-ended low power amplifiers terminating in an output high power module. In the output module, one medium power device acts as a driver stage for four high power devices connected in parallel. The output stages are hybrid coupled, and isolators before and after these hybrid coupled output stages isolate the driver from the final amplifiers and protect the output devices from reflected signals. A dynamically controlled PIN diode variable attenuator at the amplifier input allows the operating point of the amplifier to be selected and adjusted while the closed loop function is in operation. A hybrid matrix power amplifier system is also disclosed.

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Long Beach, CA, United States of America

David L Crampton