| 摘要 |
Data is extracted from a demodulated signal (V) by reference to a mean amplitude level (Vref, Mp1) of the signal determined by monitoring the time which the signal spends above and below said mean level and adjusting said signal and mean level relative to one another to equate the mean time the signal spends above and below said mean level. A mean zero level (0) may be determined by monitoring the whole of the time that the signal spends either above or below said mean zero level, and can be used to establish the zero crossings where the signal passes through the mean zero level. Also, a mean level may be determined in relation to a threshold level (O, Mp2) by monitoring only while the signal is above (or below) the threshold, the signal being monitored according to the time spent between the threshold and the mean level (Mp1) and the time spent above (or below) the mean level. The threshold may be the mean zero level (O) and may subsequently be set at a level (Mp2) offset from the zero level towards the peak signal values. |
