Short-duration pulses for time-domain spectrometry using directional couplers

Quarter-wavelength directional couplers can be used to give pulses of short duretion from sources, such as the tunnel diode, which produce relatively long pulses with a fast leading edge. These time-limited pulses can be used in time domain spectrometry of active devices to reduce the incident power, while increasing the signal/noise ratio over a band of frequencies.