GB925764A - Microwave circuit arrangement for single sideband suppression - Google Patents

Abstract

925,764. Automatic phase control systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Feb. 13, 1962 [April 25, 1961], No. 14926/61. Class 40 (5). In a microwave single sideband generator with carrier suppression carrier is fed along two waveguides 1, 2 from a 3 db. coupler 3 with 90 degrees phase difference to two ferrite modulators 5, 6 with modulation applied to each in phase quadrature so that the upper (or lower) sidebands of the modulators outputs are in phase and the lower (or upper) sidebands in anti-phase. All of any unmodulated carrier is fed by polarization sensitive side arms 7, 8 to dummy loads 9, 10. If one pair of sidebands is phase shifted at 12 by +90 degrees and both pairs applied to a 3 db. coupler 4 producing a 90 degrees phase shift (lag) of the output of modulator 6 then only the lower sideband is produced at B (and the upper sideband suppressed). A variable phase shifter 11 in one waveguide 1 compensates for any phase difference variation from 90 degrees of the two carrier inputs and is automatically controlled from an amplifier 30 energized by a phase detector 25- 27. This takes inputs from both side arms 7, 8 through 10 db. couplers 24, 23 shifting one through 90 degrees at 29 so that both inputs to a 3 db. coupler 25 are normally in phase, and its two outputs rectified at 26, 27 are normally equal, and their difference taken as input to amplifier 30. (28 is an attenuator to equalize the two rectifier outputs).