| 摘要 |
1,217,746. Angle modulated receivers. CONSIGLIO NAZIONALE DELLE RICERCHE. 22 May, 1968 [22 May, 1967], No. 24318/68. Heading H3R. The invention comprises an arrangement for detecting sudden abrupt changes in phase in the output of a phase demodulator, being characterized by the steps of filtering out at the demodulator output a frequency band below the spectrum of the modulating signal and detecting in the filtered frequency transients due to the phase changes in the demodulator. At low signal levels, the output of an angle-modulation demodulator 1 comprising a multiplicative mixer 2 having as one input the signal to be demodulated and as the other the output of a locked oscillator 4 controlled from the output of amplifier 3 which is fed from mixer 2, can exhibit sudden jumps in phase, comprising 2# and multiples thereof as the oscillator 4 falls out of synchronism and is re-locked. The output of the demodulator 1 is fed via equalizer 6 to a low-pass filter 7 passing only frequencies below the modulation frequencies. Sudden phase jumps, constituting noise, are selected by a threshold circuit 9 and applied to a waveform generator 10 which pro- @es equal and opposite pulses. These are combined in addition circuit 11 with the signal, suitably delayed by passage through a delay line 8, to produce a signal in which the noise due to phase jumps is eliminated. |
