| 摘要 |
<p>The detector includes two bandstop filters (1,2) with each filter receiving a modulated signal (Rx). Two energy calculating circuits (3,4) are also provided with one associated with each filter. Each filter has a cut-off frequency (F0,F1) which corresponds to one of the frequencies used for frequency jump modulation of the received signal. The outputs of the energy calculating circuits are applied to a comparator (5) which generates a final detection signal at its output. The two frequencies used by the system can be 165 Hz and 185 Hz.</p> |
