GB590209A - Improvements in or relating to radio receivers operating with diversity reception - Google Patents

Abstract

590,209. Radio receiving circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Jan. 15, 1945, No. 1121. Convention date, Jan. 14, 1944. [Class 40 (v)] A diversity receiver has two receiving channels each arranged to feed separately a pair of signal conbining circuits arranged to afford in phase and anti-phase combination respectively of signals fed from both channels in phase, and a load circuit arranged to be fed in common from the output of both signal combining circuits. Fig. 1 shows an arrangement including two channels A, B, each comprising an aerial 1, R.F. amplifier 10, frequency changer 11 fed by a common oscillator 13, and I.F. amplifier 12. The outputs from the two channels are fed to pairs of valves C, D, the pair C being arranged to supply the difference of the two signals to a tuned circuit 14, while pair D supplies the sum of the two signals to tuned circuit 17. The resultant signals in circuits 14, 17 are rectified in valve pair 15, 16 having a common bias and load resistor 25. With this arrangement, the greater signal produces a bias across 25 which effectively suppresses the weaker signal. The only case where the signals are equal is when they are in quadrature and so there is no cancellation distortion. For frequency modulation a signal is taken through tuned circuit 18 to detecting apparatus 26. An amplitude modulation signal may be taken from resistor 25. In a modification, Fig. 2 (not shown), two additional valve pairs corresponding to C and D are provided and are fed from channels A and B through networks introducing a 90 degrees phase shift. All four resultants are rectified using a common resistor 25. Specifications 252,798, 296,678, [both in Class 40 (v)], and 489,094 are referred to.