TRANSMIT-RECEIVE SWITCHING CIRCUIT FOR USE IN AN NMR SPECTROMETER

摘要

A transmit-receive switching circuit is offered which is for use in an NMR spectrometer that employs a solid-state NMR probe using a cooled detection coil. The switching circuit is cryogenically cooled to reduce thermal noise in use. The switching circuit has a first terminal for applying high-power RF pulses sent in from the power amplifier of the NMR spectrometer, a second terminal for sending the RF pulses applied from the first terminal to the NMR detector via crossed-diodes and for receiving and entering a low-power NMR signal detected by the NMR detector, and a third terminal for sending the NMR signal entered from the second terminal toward a preamplifier. Plural stages of shunts are connected to the transmission line connecting the second and third terminals such that one stage of shunt corresponds to a 90° phase shift in the RF radiation.