A NEW NMR DUPLEXER MADE WITH QUADRATURE COUPLERS

A new type of duplexer is presented which employs two 90-degrees couplers. It is an ideally lossless device, with an attenuation of about 1 dB in both receiving and high power (> 50 dBm) transmitting modes, and with a transmitter-receiver isolation better than 40 dB. We describe two duplexers built with multi-octave couplers, covering the frequency ranges 30-90 MHz and 90-500 MHz, respectively. These broadband devices are conveniently employed in high RF-power, multinuclear NMR spectrometers.