Patent ID: 8788234

Claim:
A method of calibrating interleaved digitizer channels for a multi-channel oscilloscope, each channel of the oscilloscope being of the type having a preamplifier for receiving an input signal and a digitizer for outputting sampled data derived from the input signal, the sampled data representing a waveform and the preamplifier and digitizer being coupled in series through a switch to produce a channel path, comprising the steps of: calibrating a bandwidth enhance filter for the output of each channel path to compensate for frequency and phase characteristics; configuring the switch to an interleaved mode such that the input signal applied to the preamplifier of one channel is applied to the digitizer for that channel to produce a reference digitizer channel path and to a digitizer of another channel to form an interleaved digitizer channel path; computing a match filter for the interleaved digitizer channel path based upon fast Fourier transforms performed on the outputs of the corresponding bandwidth enhance filters for the reference digitizer channel path and for the interleaved digitizer channel path so the output of the interleaved digitizer channel path matches the output of the reference digitizer channel path in phase and magnitude at all frequencies when the match filter is applied to the output of the interleaved digitizer channel path; performing a fast Fourier transform on the outputs of the reference digitizer channel path and the interleaved digitizer channel path after application of the respective bandwidth enhance filters to determine a phase angle between the reference and interleaved digitizer channel paths at a largest harmonic greater than a predetermined frequency value; and converting the phase angle into a time value for delaying a sample clock for the digitizer for the reference digitizer channel path to become a delayed sample clock for the digitizer for the interleaved digitizer channel path.