The present invention relates to a non-linearity compensating circuit for high-frequency amplifiers comprising a branch coupler for dividing the input signal into two components, two high-frequency amplifiers, one operating in the non-linear region, the other operating in the linear region, and each receiving one of the two signal components from said branch coupler, and a signal synthesizing circuit for taking the vectorial sum of the two antiphase signals from the two amplifiers whereby the non-linearity compensating circuit provides an input/output characteristics which is just the opposite of the input/output characteristics of the high-frequency amplifier to be compensated. Basically, the non-linearity compensating circuit according to the present invention does not require long delay lines, variable attenuators or variable phase-shifters of a special design so that the whole circuit can be constructed in a microwave integrated circuit form which has a reduced power loss.

A device for compensating for nonlinearity of amplifiers by use of a predistortion principle, and a nonlinear signal generating circuit built in such a device. The nonlinear signal generating circuit includes a quadrature hybrid of the type using a distributed constant line. Two diodes and a terminal resistor are connected in parallel and opposite in polarity to each other and connected between the terminals of coupling and passing ports of the hybrid and ground. The nonlinear compensating device is constituted by the combination of a plurality of quadrature hybrids of the type using a distributed constant line and various kinds of diodes. All the circuit segments of the device are implemented with a planar circuit provided on a single dielectric substrate and diodes which are held in a pair chip condition. Such circuitry is accommodated in a single air-tight housing to complete a microwave integrated circuit.

A linear power amplifier includes a driver stage, employing an active feedforward-type predistorter, connected in cascade with a final power stage. The active feedforward-type predistorter has an amplifier with a predistorter connecting between its input and output. This driver stage has opposite gain and phase characteristics to that of the final power stage and is used to predistort an input signal. When combined with the final power stage, the nonlinear gain and phase of the power stage are compensated and linearized by the driver stage, resulting in a linear power amplifier with low distortion amplification and high efficiency operation.

The present invention relates to a device for correcting the phase induced by the class C operation of a solid state amplifier. It is applied in the field of the manufacture of pulse radar transmitters. Solid state amplifiers are prone to generating phase variations. The invention relates to a measurement and correction loop which allows the real time elimination of phase variations due to heating up.

A power amplifier includes a plurality of signal amplifying stages. An amplitude compensator positioned prior to the ultimate signal amplifying stage equalizes the signal amplitudes in the frequency band of interest to provide a substantially flat frequency response. Fail-soft operation is established by providing switchably redundant amplifiers. When an operating amplifier is detected as failing, automatic switching is performed to replace the failing unit with an identical unit to maintain amplifier operation. High-power amplification is accomplished by splitting a preamplified signal into a plurality of signals, amplifying the lower level signals so obtained, and then recombining the amplified signals.