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Singly-balanced active mixer circuit

  • US 4,369,522 A
  • Filed: 08/30/1979
  • Issued: 01/18/1983
  • Est. Priority Date: 07/03/1978
  • Status: Expired due to Term
First Claim
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1. A singly-balanced active mixer for developing an intermediate frequency (IF) signal from a radio frequency (RF) signal and a local oscillator (LO) signal, the local oscillator signal being comprised of two substantially equal components phase shifted by 180 degrees with respect to one another, said mixer comprising:

  • (a) first and second bipolar transistor devices each having an emitter, base and collector and arranged in a common-emitter configuration, the base of the first device coupled to the RF signal and to one of the LO signals for providing a first mixer signal, and the base of the second device coupled to the RF signal and to the other one of the LO signals for providing a second mixer signal;

    (b) a first DC biasing network coupled to the emitters of the first and second devices for applying a predetermined bias voltage hereto;

    (c) a second DC biasing network coupled to the bases of the first and second devices for applying a predetermined bias voltage thereto;

    (d) an output transformer having a tap at a predetermined location on the primary winding, said tap not being bypassed at the RF, LO and IF frequencies, the first and second mixer signals from the first and second devices coupled to opposite ends of the primary winding, IF components of the first and second mixer signals adding in phase in the primary winding, and the composite IF signal provided across the secondary winding of said output transformer; and

    (e) a third DC biasing network coupled to said tap of the primary winding of the output transformer for applying a predetermined bias voltage to the collectors of the first and second devices.

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