Abstract: An active Q-switching circuit using a transformer is described for reducing the recovery time of NQR probes. A MOSFET was used to control the coupling and decoupling states of the Q-switching circuit to the probe so that it did not operate during the reception of NQR signals. The performance of the circuits was demonstrated by experimental results. It was shown that the circuit did not create new ringing, and caused no loss in sensitivity.

Key words: NQR, probe, Q-switching, recovery time