Broadband monolithic balanced mixer apparatus
 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. 
Siemens Aktiengesellschaft
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Raymond M. Tzu-Hung Mahesh
Waugh Chen Kumar