Phase Correction Algorithm for Single-Chip Wireless Motes with Crystal-Free CMOS Oscillators

Free-running oscillators allow a chip designer to minimize the size and power design requirements of a system by removing the crystal phase reference. Removing a crystal referenced phase-locked loop (PLL), introduces phase noise to the oscillator. This work demonstrates that an offline phase synchronization algorithm is able to correct the frequency variations on a free-running LC-tank based oscillator sufficient to incorporate a phase shift keying-based protocol. The data-aided implementation of the algorithm successfully demodulates and corrects the phase offset at near minimum bit error rate (BER) until E_b/N₀ of 8dB after which phase noise dominates. The non-data aided mode preforms zero bit errors after E_b/N₀ of 13dB, within the limits of the 8512 bits and 300 Monte Carlo iterations.