GB705685A - Improvements in or relating to mixer circuit arrangements for use at ultra high frequencies - Google Patents

Abstract

705,685. Radio frequency systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. March 5, 1952 [April 19, 1951], No. 9212/51. Class 40 (5) A mixer circuit for generating an intermediate frequency signal from an incoming ultra-high frequency signal comprises local oscillator and rectifier circuits for deriving I.F. signals in phase opposition, and a phase-changing network to opposite ends of which the oppositely-phased I.F. signals are applied, the I.F. output being taken from one end of the phase-changing network. In the arrangement shown in Fig, 2, the output of local oscillator 6 is mixed by means of rectifiers 3, 4 with two oppositely-phased U.H.F. outputs from the R.F. network 2. The resultant oppositely-phased I.F. signals are applied to opposite ends of a #-type filter section producing a 180 degree phase-shift so that the two signals combine in phase at the input to the first I.F. amplifier 9. Chokes CH1, CH2 are connected as shown to provide a D.C. return path for the rectifier circuits. A condenser 10 (and also if desired a shunt resistance) may be provided to balance the input impedance of the valve 9. A neutralizing condenser 11 may also be provided. In an alternative arrangement, Fig. 4 (not shown), the phase-shifting network is replaced by two 90 degrees phase-shifting #-sections connected in series. Fig. 3 shows a further arrangement in which the phase-shifting network comprises a length of transmission line. The output from the transmission line is coupled to the I.F. amplifier through an impedance transformer CR comprising a length of short-circuited transmission line as shown.