Siemens Aktiengesellschaft

Tzu-Hung Chen

Mahesh Kumar

Raymond M Waugh

Amplifiers operating in push-pull are implemented to obviate input baluns and output signal combiners and their attendant losses. Amplifiers having two signal branches that each receive the input signal and have their signal branch outputs connected directly together. Each branch operates during alternate half cycles of the input signal while direct combining of the branch signal outputs produces a composite signal corresponding to the complete input signal. Each branch includes a matching input circuit and a heterojunction bipolar transistor whcih may be configured in either common collector or common emitter arrangement. The transistors are different since one is an NPN while the other is a PNP but they are selected to have similar direct current and radio frequency characteristics.

High efficiency amplifier

A broadband monolithic balanced mixer employs a unidirectional active 180.degree. hybrid. The hybrid is fabricated utilizing two active signal splitters, two all pass phase shifting networks and two active signal combiners. The all pass networks provide a controlled phase response while the absolute phase of the network varies with frequency whereby the frequency difference between the two networks remains constant at 180.degree. over a very broad frequency range. Because the phase varies with frequency, the source and load impedance are rendered equal and resistive. Thus the above-described apparatus employs a common source FET with feedback for the signal splitter and a common gate FET for the combiner. Matching networks are used at all four ports of the active hybrid to achieve the desired match over the desired frequency ranges. The outputs of the hybrid are applied to suitable mixer circuits including FET or diode devices.

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East Brunswick, NJ, United States of America

Tzu-Hung Chen