On the Performance of Variable Fractional Delay Arbitrary Sample Rate Conversion for Digital Signals

Arbitrary sample rate conversion (ASRC) is a critical digital signal processing function for any signal that is received and down converted from analog RF to either digital-IF or-base band. There are numerous ASRC applications, including, but not limited to commercial and military communications, radar- and audio-signal processing, and multi-function systems (such as coexistence of EW and communication systems). Furthermore, variable fractional delay (VFD) processing is critical when synchronizing to any transmit signal, for precise timing in geolocation processing or for any receiver process where accurate timing is required. There are many designs for VFD-ASRC which may operate across a wide range of parameters in a functional sense, but which do not perform equally across their operational range. Few methods exist in the literature for evaluating the performance of these designs in a generalized fashion for applicability to project specifications. This work proposes a method for evaluating the performance of any VFD-ASRC system. The generalized technique uses a high performance filter bank followed by frequency-domain magnitude- and group delay-error metrics to provide a measure of the quality of a VFD-ASRC design. The method can be applied to any single- and multiple-carrier modulation signal.