A new pulse width reduction technique for pulsed electron paramagnetic resonance spectroscopy

We present a new technique for a microwave pulse modulator that generates a short microwave pulse of approximately 1 ns for use in an electron paramagnetic resonance (EPR) spectrometer. A quadruple-frequency multiplier that generates a signal of 16-20 GHz from an input of 4-5 GHz was employed to reduce the rise and fall times of the pulse prepared by a PIN diode switch. We examined the transient response characteristics of a commercial frequency multiplier and found that the device can function as a multiplier for pulsed signal even though it was designed for continuous wave operation. We applied the technique to a Ku band pulsed EPR spectrometer and successfully observed a spin echo signal with a broad excitation bandwidth of approximately 1.6 mT using 80° pulses of 1.5 ns.