Design of a sampling mixer for use in UWB radar applications

The design, simulations and measurements of a sampling mixer are presented in this paper. Ultra-Wide-Band pulse radar applications demand high performance digitalization of the received RF signal with few GHz of bandwidth. Since high sampling rate analog to digital converters are very expensive and complex, we designed an inexpensive sampling mixer based on the equivalent sample time technique. A sampling mixer uses a bridge with two diodes for capturing a portion of a signal in each period. After a certain amount of repetitive periods, the sampling mixer reconstructs the original RF signal. The reconstructed signal is stretched from the sub-nanoseconds order into the microsecond order. Such stretched RF signal can be digitalized using a low rate analog to digital converter with sampling rate of a few MSa/s.