Abstract: A multi-functional spectrometer, capable of dynamic nuclear polarization (DNP) and electron paramagnetic resonance (EPR) experiments, is put forward on the basis of a home-built DNP-magnetic resonance imaging (MRI) spectrometer. A key component of the multi-functional spectrometer, microwave bridge, was designed and implemented. The microwave bridge was used to integrate the microwave transmitter of the DNP spectrometer and to enable the EPR capability. A transmitter system with high spectrum purity and dynamic range as well as a detector with low noise figure were also implemented by structure designing, circuit simulation and system evaluation. DNP and continuous wave EPR experiments were conducted to verify the reliability of the microwave bridge.

Key words: dynamic nuclear polarization (DNP), microwave bridge, low noise amplifier (LNA), electron paramagnetic resonance (EPR)