An active cancellation system may be utilized to cancel interference, such as from transmitter leakage or self-interference in a transceiver of an electron paramagnetic resonance (EPR) spectrometer. The active cancellation system may be inserted between the transmitter and receiver. The active cancellation system may receive the output of the transmitter, and generate a cancellation signal with the same amplitude, but phase shifted relative to the self-interference signal. The cancellation system may include an attenuator/amplitude tuner, buffer, VQ generator, and phase shifter.