公开(公告)号：US4563651A

公开(公告)日：1986-01-07

申请号：US370795

申请日：1982-04-22

申请人： Tomozo Ohta ,  Yoshio Tsutsumi ,  Yoshihiro Konishi

发明人： Tomozo Ohta ,  Yoshio Tsutsumi ,  Yoshihiro Konishi

IPC分类号： H03D3/00 ,  H03G5/24

CPC分类号： H03D3/00 ,  H03G5/24

摘要： The threshold level for demodulating an FM signal, for instance a television picture signal, has been improved or lowered by adaptively restricting the bandwidth of the signal using an adaptive bandpass filter, and therefore, the picture quality and/or S/N ratio of the demodulated television signal has been improved. The adaptive bandpass filter has enough bandwidth when the signal level is sufficiently higher than the threshold level, but is narrow when the signal level is close to or lower than the threshold level. The bandwidth of the adaptive bandpass filter is adjusted according to the total power of the input FM signal and C/N (the carrier signal to noise) ratio. The improvement of the threshold level is almost 2 dB.

摘要翻译： 通过使用自适应带通滤波器自适应地限制信号的带宽，已经改善或降低了用于解调FM信号（例如电视图像信号）的阈值电平，因此，图像质量和/或S / N比 解调后的电视信号得到改善。 当信号电平足够高于阈值电平时，自适应带通滤波器具有足够的带宽，而当信号电平接近或低于阈值电平时，该带宽较窄。 自适应带通滤波器的带宽根据输入FM信号的总功率和C / N（载波信号对噪声）的比例进行调整。 阈值水平的提高几乎为2 dB。