Dual diode detector for homodyne EPR microwave bridges

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Abstract
After low noise FET amplifiers found widespread use in both X‐band and low‐frequency systems, it became possible to use multidiode mixers for signal detection. Here, a novel dual diode mixer is described for use in homodyne microwave bridges for both cw and pulsed electron paramagnetic resonance spectrometers. The structure is composed of a 90° hybrid coupler and separate detectors in two arms. The device provides common mode rejection of noise‐like regular balanced mixers but, by making diode dc currents accessible, offers big advantages for tuning of the bridge when low Q sample probes are used. Although the use of this detector does not affect sensitivity directly, tuning precision and increased long‐term stability leads to unexpected improvements.