All-Digital Phase Locked Loop with Single Reference Frequency Oscillator

All-digital Phase Locked Loop is designed in this article. A combinational frequency multiplier is developed and tested to achieve completely integrated system using only one low frequency reference oscillator. Adaptive proportional-integral regulation is used to ensure high stability, low phase noise and fast synchronization in wide frequency range. The system is developed and tested on Spartan 3E FPGA by Xilinx.