Digital Processing of SAW Filters Responses, Exited by Pulse Signals in Time to Digital Converter

The paper discusses the application of the classical digital signal processing algorithms to the problem of the measuring a time interval between two pulses. The value of the measured interval is determined by the position of the maximum of the cross-correlation function of two impulse responses of Surface Acoustic Wave (SAW) filters. The responses of the SAW filters are sampled at a lower frequency, which reduces requirements to an analog-to-digital converter. In post-processing, the response sampling rate can be increased to an arbitrarily large value. Increasing the sampling rate improves the resolution in determining the value of the time interval being measured. The Cross-Correlation Function (CCF) of two responses is calculated at the increased frequency using the discrete Fourier transform. The search for the maximum of the CCF is performed on its envelope, calculated through the discrete Hilbert transform. The position of the maximum of the CCF is further refined due to the local interpolation of the envelope by a polynomial of even degree. The results of the algorithms are demonstrated using the real responses of a SAW filter.