Time-interleaved samplers

A calibration apparatus for calibrating a time interleaved analogue to digital sampler said sampler comprising a plurality (N) of time-interleaved channels, each sampled by an ADC, said sampler having an input for receiving an analogue input signal and an output for providing a digital output signal, and the apparatus including:

• (a) means for injecting in turn N calibration signals into the input of said sampler such that each calibration signal occupies at least one of N related frequencies, wherein the related frequencies are those for which, given an input signal at any one of those frequencies, mismatches in the interleaving channels affect the resultant output of the sampler at the other related frequencies;
• (b) means for measuring in the frequency domain of the interleaved sampled data the output signal at each of the N related frequencies for each one of the N calibration frequencies;
• and
• (c) means for determining the relationship that relates the input signal to the output signal at each of the N related frequencies for each one of the N calibration frequencies.