Heterodyne receiver with synchronous demodulation for time signal reception

摘要

The receiver accepts the various international time signal frequencies and converts them into intermediate frequencies which are synchronously demodulated by means of a second mixer (M2) obtaining its signals from a second phase-locked loop (PLL2). This produces a frequency (f2) from a voltage-controlled oscillator delivering two outputs in quadrature. The control signal for the oscillator is obtained from addition of the output of the phase comparator via a loop filter to the weighted part of the control signal supplied by the first loop (PLL1) to the band-pass filter (BP) interconnecting the two mixers.