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