Pulse Position Modulation based on phase locked loop

It is well know that pulse position modulation (PPM) play an important role in optical and wireless communication, because of they save the power for transmission and obtained the high utilization of bandwidth. Consequently, in this paper PPM based on phase locked loop (PLL) with carrier and without carrier are proposed. It can easily adjust carrier frequency by tuning reference signal frequency of PLL. The proposed circuit is compose of voltage control oscillator (VCO), RC low pass loop filter, two mono stable multi vibrator and RS F/F. In order to obtain the PPM with carrier, we only add both output mono stable multi vibrator together. The experimental result show that this proposed PPM circuit work well and it is a compact size, when we compare with various signals that it can generate, such as pulse width modulation (PWM), PPM, with and without carrier.