| 摘要 |
<p>A FM demodulator characterized in that: as far as the use of a circuit (2) for generating frequency-dependent phase differences and a phase difference comparing circuit (3) successively connected to the circuit (2) is concerned, the demodulator is the same as a conventional FM demodulator; instead of producing the demodulated ouptut in an analog signal form by averaging the binary outputs of the phase difference comparing circuit (3), these binary outputs are quantized on a time axis by a fixed rate clock signal (8) without averaging them; and further, the resultant binary signals of a pulse density modulation from are converted into signals in a parallel digital word string from by a counter or a decimation filter (6) to obtain an object signal directly in a digital word string form. The advantages of the direct digital demodulator are, self-evidently, the reduction of the number of parts and cost by virtue of the reduction of the number of steps of the processing, the reduction of size and the enhancement of reliability. Further, nonlinear distortion, generation of offset, variation of gain, entrance of noise all of which arise from analog parts can be avoided, because the object signal is not passed through analog stages.</p> |
