| 摘要 |
<p>A pilot signal detection circuit receives a supply of a pilot signal (P) produced by frequency-modulation of a predetermined third frequency carrier signal by a first discrimination signal of a first frequency and a second discrimination signal of a second frequency, and makes a discrimination between the first discrimination signal and the second discrimination signal by whether a signal detected is of the first frequency or of the second frequency. The pilot signal detection circuit is constituted by first and second multiplying and filtering stages (30,40). The first multiplying and filtering stage (30) includes first and second multipliers (2,3) and first and second low-pass filters (4,5). The first and second multipliers multiply the pilot signal (P) respectively with the first reference signal (e1(t)) and the second reference signal (e2(t)), and produce respectively first and second multiplied signals (R1,R2). The first and second low-pass filters (4,5) carry out a predetermined low-pass filtering in response to a supply of the first and second multiplied signals, and produce respectively first and second filtered signals (Q1,Q2). By providing these multipliers and the low-pass filters at the input side for pre-processing of signals, the requirement of the linearity of the second multiplying and the filtering stage elements is relaxed. <IMAGE></p> |
