GB931252A - Improvements in or relating to phase detectors for synchronising a local oscillator - Google Patents

Abstract

931,252. Phase discriminators. PHILIPS ELECTRICAL INDUSTRIES Ltd. Oct. 7, 1959 [Oct. 10, 1958], No. 34005/59. Class 40 (5). In a phase discriminator in which rectangular pulses 1 are additively and subtractively combined with a saw-tooth wave 10 as pedestal and the resultant peaks rectified and differentially combined across an output capacitor 11 the saw-tooth slope gives the pulse peaks a corresponding slope so that the rectifiers conduct at different instants resulting in errors. This may be avoided by producing across the capacitor 16 of a R.C. time constant network 16, 17 a saw-tooth voltage 18 compensating the saw-tooth slope and producing flat top sum and difference voltages 14<SP>1</SP>, 15<SP>1</SP> as shown, the top 22 being selected to equalize the resultant maximum and minimum amplitude. Alternatively, Fig. 7, a saw-tooth wave 26 may be added to only one pulse 27 to more than compensate the slope of saw-tooth 10 and make the peaks of resultant voltages 28, 29 slope opposite ways. Alternatively, Fig. 9, an R.C. leakage circuit 16, 17 may be connected across one half of the pulse input so that the pulse peaks of waveforms 28<SP>1</SP>, 29<SP>1</SP> slope opposite ways and their leading edges render the rectifiers 3, 6 conductive at the same instant.