Picosecond Pulse Expansion Using The Low-Pass Filter in Event Timer-Based PPM Communication System

Pulse position modulation (PPM) is a highly energy-efficient signaling technique in which the information is encoded in the time position of short pulses. However, due to the limited bandwidth of PPM receiver, detecting very short pulses could be challenging. The electrical pulse expansion can be applied to overcome this limitation. This is especially important in ultra-high precision timer applications in PPM signal demodulation. The paper discusses the radio frequency (RF) low-pass filter (LPF) application for pulse expansion purposes. Analytical and experimental results demonstrate the expansion of electrical pulses having 50 ps duration at full width at half maximum (FWHM) using several types of LPFs. The impact of the filter parameters on the PPM pulse shape, amplitude, and duration is discussed.