Correcting Timebase Errors in Ultra-Wideband Equivalent-Time Sampling Receivers

Timebase errors in UWB pulsed-radar equivalent-time sampling receivers can be significant, leading to unacceptable time-domain and frequency-domain distortions when picosecond pulses are processed. Here, we report a calibration method which mitigates these errors effectively. The method is demonstrated with an in-house dual-channel receiver with an effective sampling rate of 20 GSa/s. A 200-MSa/s analog-to-digital converter (ADC) is used in conjunction with a programmable delay chip (PDC), which shifts the temporal sampling point from one pulse period to the next. The programmable delays of the PDC are provided by manufacturers. However, the actual delays deviate from the prescribed values. Moreover, the deviation depends on environmental factors, especially temperature. Therefore, a calibration procedure is needed to obtain the true delays provided by the PDC. The calibration’s effectiveness is demonstrated through sinusoidal waveforms and picosecond pulse measurements.