| 摘要 |
<p>Amplitude limiting of a frequency modulated signal, in particular a sampled signal such as a multiplexed analogue component television signal, in order to reduce the bandwidth taken up by the signal. A number of problems arise when applying limiting to a signal, in particular limiting especially a sampled signal can produce aliasing effects due to harmonics. Also if any filtering is applied to the signal after limiting much of the effect of the limiting is removed. The present invention overcomes these problems by applying differing degrees of limiting to the signal depending upon the frequency being limited at a particular time. In one embodiment the signal is filtered prior to the application of limitation, so that more of some frequencies are allowed to pass through to the limiter than others. A post-filter is applied to the signal after limitation to correct for the effects of the pre-filter.</p> |
