| 摘要 |
<p>A charge-coupled device has a transversal filter portion (10) having split sensing electrodes (109, 113, 117, 121, 125) whose segments (A, B) are connected to respective output lines (SE1, SE2), and an auxiliary portion (20) which has one or more auxiliary split sensing electrodes (209) whose segments (A, B) are respectively connected to the same output lines (SE1, SE2). There are many more sensing electrodes in the filter portion (10) than in the auxiliary portion (20). In use, signal-independent charge packets are transferred along the channel in the auxiliary portion to provide a controllable offset signal, which can be used to provide a controllable threshold for tone detection. There may additionally be a dummy portion (30) to balance the capacitative loading of the output lines (SE1, SE2) by the auxiliary electrodes (209). </p> |
