Indirect VCO Phase Modulation with PLL Divider Control

Abstract:
This paper presents an alternative and simple architecture of phase modulation technique compared to the classical PLL phase modulation techniques. In contrast to classical PLL phase modulation techniques, the PLL loop in novel technique is not broken at any point. Here the modulating signal momentary changes the divider values to achieve phase modulation at the output of PLL. Therefore the circuit complexity and mismatch problems of classical approaches caused due to addition of an external modulating signal in PLL loop are removed. To verify the concept, simulations and measurements of PLL phase modulation at 2.4GHz are presented. Simulations results of 16-PSK are shown. The hardware measurements are also included showing the phase modulation. With less complexity this approach overcomes the drawbacks of classical techniques and provides an alternative PLL phase modulation technique.