Wideband RF Transmit-Receive Switch for Multi-Nuclei NMR Spectrometers

The utility of wideband high field nuclear magnetic resonance (NMR) spectrometers is significant in many applications. Wideband radio frequency (RF) front-ends are critical for the realization of multi-nuclei spectrometers. To realize such systems, wideband Transmit-Receive (TR) switches and low noi...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. II, Express briefs Express briefs, 2022-03, Vol.69 (3), p.904-908
Main Authors: Abou-Khousa, Mohamed A., Mustapha, Ademola A.
Format: Article
Language:English
Subjects:
Bandwidths
Broadband
Continuous radiation
Driver circuits
Insertion loss
Low noise
Narrowband
NMR
Nuclear magnetic resonance
Nuclei
PIN diode driver
PIN diodes
PIN photodiodes
Radio frequency
radio frequency front-end
Signal measurement
signal-to-noise ratio (SNR)
spectrometer
Spectrometers
Switches
Switching circuits
Wideband
wideband TR switches
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Summary:The utility of wideband high field nuclear magnetic resonance (NMR) spectrometers is significant in many applications. Wideband radio frequency (RF) front-ends are critical for the realization of multi-nuclei spectrometers. To realize such systems, wideband Transmit-Receive (TR) switches and low noise amplifiers (LNA) should be implemented at the RF front-end (FE) of the system. Most of the common designs used nowadays on NMR spectrometers are either inherently narrowband and/or of relatively high noise-figure which limit the overall system performance to a large extent. To improve upon the conventional FE performance, a new design of wideband high-power TR switch which could be devised for multi-nuclei NMR spectrometers is introduced in this brief. The developed wideband TR switch employs PIN diode switching technique and a dual-driver circuit. A prototype was constructed and experimentally characterized. The small-signal measurement results show that the switch has a bandwidth from 30 - 200MHz where the return loss is maintained below 18 dB with insertion loss of 0.09 - 0.2dB in the transmit mode and 0.11 - 0.37dB in the receive mode. It also exhibits a very high isolation of 63 - 80dB over the entire bandwidth. It is demonstrated that the switch can withstand continuous-wave RF input with power levels as high as 125 W while maintaining low insertion loss and high isolation.
ISSN:1549-7747
1558-3791
DOI:10.1109/TCSII.2021.3121210