| 摘要 |
Compression of a digital microphone signal for transmission on a bus A digital compression circuit 106 uses a form of differential encoding in which the output codes depend on both the present and previous differences of digital audio samples from a multi-bit quantizer 120. The quantizer is part of a sigma-delta analogue-to-digital converter 104 coupled to a microphone 102. The output codes may be selected to reduce bit transitions, and a digital processing circuit 108 may instruct the compressor 106 to output words with more bits if the circuit 108 detects ultrasonic signal content. The feedback signal in the converter 104 may be derived from the output of the compression circuit 106 (figure 4). Multiple conversion and compression paths (figure 3) may be selected or combined to provide a larger dynamic range. |
