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A passive dual-circulator based transmit/receive switch for use with reflection resonators in pulse EPR
V S Subramanian1, Boris Epel, Colin Mailer
1Center for EPR Imaging In Vivo Physiology, Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60637.
Summary
Protecting sensitive equipment in pulsed Electron Paramagnetic Resonance (EPR) spectroscopy is crucial. This study introduces a novel method using circulators and PIN diodes to achieve high isolation, safeguarding the low noise amplifier (LNA).
Area of Science:
- Physical Chemistry
- Spectroscopy
- Electronics
Background:
- Pulsed Electron Paramagnetic Resonance (EPR) bridges require protection for the low noise amplifier (LNA) from high power pulses.
- Effective isolation is needed to prevent damage to the LNA while preserving signal integrity.
Purpose of the Study:
- To develop and evaluate a passive protection system for the LNA in a 250 MHz pulsed EPR bridge.
- To ensure undistorted signal transmission to the LNA after high power excitation.
Main Methods:
- Utilized a combination of a power-routing circulator and a second circulator acting as an isolator.
- Incorporated passive shunt PIN diodes to create an impedance mismatch during high power pulses.
- Designed a system to reflect high power to a matched load, protecting the LNA.
Main Results:
- The developed system passively limits output power to 14 dBm, irrespective of input power.
- Achieved isolation exceeding 60 dB for high input power levels.
- Demonstrated sufficient protection for the LNA in pulsed EPR bridge applications.
Conclusions:
- The passive protection circuit effectively safeguards the LNA in pulsed EPR bridges.
- This method provides robust isolation against high power pulses without compromising signal quality.
- The system offers a reliable solution for maintaining LNA integrity in demanding spectroscopic environments.
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