| 摘要 |
<p>A decoder circuit which employs digital sampling and correlation apparatus to detect the presence of a received tone signal exhibiting a predetermined frequency. Samples of received tone signals are taken and, in effect, multiplied by a substantially rectangualr observation window which includes a bite interval of selected duration and location therein. A correlator correlates the windowed samples to detect samples corresponding to the predetermined frequency (main lobe frequency). A significant decrease in undesired side lobe response is thus achieved. </p> |
