| 摘要 |
PURPOSE:To attain ease of noise detection even with a small IF band by using a low range component of an output obtained by multiplaying a signal shifted respectively for the phase by 90 deg. to a pilot signal or a subcarrier signal by a composite signal as a noise detection output. CONSTITUTION:The composite signal detected by an FM detector 1 is multiplied by the signal shifted for the phase by 90 deg. to the pilot signal at a phase comparator 3 of a PLL circuit comprising the phase comparator 3, LPF4, VCO5 and a frequency divider 6. If a noise exists near the pilot signal, it is detected through the LPF7. Since the noise near the pilop signal is detected in such a way, the noise detection is attained accurately even with a small IF band width. |
