Frequency synthesis using frequency controlled carrier modulated with pll feedback signal

Abstract From the Canadian patent

In a frequency synthesizer, a phase detector receives an externally-generated reference clock signal of a constant frequency and a feedback signal to produce an error signal, which is output through a loop filter to a voltage-controlled oscillator (VCO). A direct digital synthesizer (DDS) receives the reference clock signal and externally-generated phase data to produce a DDS output signal whose frequency is precisely controlled by the phase data. The DDS output signal is applied as a carrier to a differential detector where it is modulated with the output of the VCO to produce a signal corresponding to the lower sideband of the modulated carrier. The output of the differential detector is …