Abstract Aiming at the problems that serious coupling existing in the double antennas of ground-penetrating radar may intensely impact the signal detection, a high-speed T/R switch system is developed. A series/shunt mode microstrip SPDT was made by using PIN diodes. By ADS simulation and parameter optimization, a SPDT with ultra-wide bandwidth and high isolation was achieved. The power supply and driving circuits were developed and the experiment results show that the switch system meets the requirements of ground-penetrating radars.