| 摘要 |
<p>Image signal demodulation apparatus for demodulating an FM image signal having a carrier, an upper sideband and first and second lower sidebands, of which a modulating signal frequency is comparably close to a frequency of the carrier. The apparatus comprises an equalizer for equalizing a group delay characteristics of the FM image signal at around the carrier frequency, a moire reduction circuit for delaying, with respect to the carrier, respective aliasing components of the first and second lower sidebands by predetermined amounts respectively in response to the output of the equalizer, a limiter for removing amplitude variations of the output of the moire reduction circuit and restoring the upper sideband, a demodulator for demodulating the output of the limiter. The output of the demodulator contains a baseband component having a maximum frequency, and a lowpass filter for passing only the baseband component lower than the maximum frequency. The demodulator together with the moire reduction circuit causes to perform as such that a first moire component generated due to an aliasing caused upon modulation of the FM image signal, becomes opposite in phase relationship to a second moire component generated upon demodulation of the FM image signal, so that the first and second moire components are cancelled out each other.</p> |
