Electronic time stretching for fast digitization

Pulses can be stretched in time by driving them into a filter whose group delay is more than the pulse duration and increasing the time constants of the filter. The stretched pulse can be digitized using a slow analog to digital converter, effectively realizing a high sampling rate for the input signal. This can be used for digitizing short bursts at high speed. The effect of clock jitter is reduced due to the reduced slope of the signal. High order Bessel allpass filters provide a maximally flat group delay and are suitable for this application.