Frequency specification testing of analog filters using wavelet transform of dynamic supply current

The wavelet transform has the property of resolving the signal in both time and frequency, unlike the Fourier transform. In this work, we show that time-domain information obtained from wavelet analysis of the supply current can be used to efficiently test the frequency specification of analog filters. The pole/zero locations in the frequency response of analog filters shift due to changes in component values with process variations. It is essential to test the filters for the shift in frequency response and fix it, during production test. Wavelet analysis of the supply current can be a promising alternative to test the frequency specification of analog filters, since it needs only one ac stimulus and is virtually unaffected by transistor threshold variation. Simulation results on two test circuits demonstrate that we can estimate the pole/zero shift with less than 3% error using only one measurement, which requires about 18 measurements in the conventional technique.