A COMPLEX VALUED DELTA SIGMA PHASE LOCKED LOOP DEMODULATOR

摘要

The demodulator (10) is a multiple stage demodulator. The first stage is a conversion stage (20) which converts an incoming signal (80) into a first complex representation (60/70). The second stage is a direct digital synthesizer (DDS) / mixer (30) which synthesizes a signal to be mixed with the first complex signal (60/70) and performs the mixing operation to produce a second complex output (120). This second complex signal (120) is controlled by a bitstream (100) fed back from the third stage - a phase quantizer stage (40). The bitstream (100) represents the quantized phase difference between the synthesized signal and the first complex signal (60/70). The DDS/mixer stage (30) then measures the synthesized signal for any phase difference from the incoming signal (80) through the feedback inherent to a PLL, the bitstream (100) thus provides an output that gives the frequency of the desired signal. As a side benefit, the real component (110) of the second complex signal (120), provides an amplitude estimate of the desired signal.