| 摘要 |
<p>PURPOSE: To detect BPSK modulation of a suppressed carrier orthogonal to a video carrier by providing a digital comb filter which receives a digitized detection response to generate a response mainly dependent upon a suitable detection response. CONSTITUTION: A keying signal and an attendant part of an NTSC composite video signal detected by a quadrature phase video detector 47 are supplied to a matching filter 58. The response from the filter 58 is supplied to an ADC 106, and the AC 106 samples it. The digital response of the ADC 106 is inputted to a high pass frame comb filter 72 through an LPF 107 and a subsampler 108, and residual luminance elements representing the frame-to-frame correlation are removed. The output of the filter 72 is inputted to a high pass line comb filter 120, and elements of the composite video signal which don't appear are suppressed. A symbol determination circuit 75 which receives the digital response of the filter 120 determines whether a symbol is '0' or '1'.</p> |
