| 摘要 |
A capacitive sensing system operates according to a method which uses an ADC with a low resolution r, to produce a digital signal with a higher resolution R. The analog signal to be digitized is modulated with a triangular or saw-tooth modulating signal, so that a modulated analog signal is obtained, which is sampled with the ADC. Thereby, digital samples are produced. An average is taken over N (>1) successive digital samples. The triangular or saw-tooth signal is chosen to have a peak-to-peak amplitude corresponding at least approximately to an integer multiple L, with L≥1, of the quantization step size of the ADC. The saw-tooth or triangular signal, furthermore, has a number M, of periods per each sequence of N samples. M and N are chosen such that M > 1 and M ≠ N and such that R = r*N/(k*gcd(N, M)*L), where gcd(M, N) is the greatest common divisor of N and M and where k=2 if the modulating signal is a saw-tooth signal and k=4 if the modulating signal is a triangular signal. |
