rate is 100 M/s). We can simply digitise this pulse by a 1000
dimension vector consisting of 1000 time-series data points. A
longer waveform, which may involve multiple PD pulse, thus
requires a higher dimensional vector for its representation. In
addition, we can also extract features for pulse shape (e.g.,
the pulse height, the pulse rise and decay time, etc.) from the
time domain [18] and some other properties for pulses from
the frequency domain by signal processing methods.