A DPLL for Joint Tracking of Frequency Offsets in RF Carriers and DAC/ADC Clocks in OFDM

The performance of an OFDM wireless communication system is adversely affected by two types of frequency offsets. One is the difference between the frequency of the local oscillator (LO) and the received signal carrier frequency. The other is the frequency offset in the clocks of DAC’s and ADC’s. The frequency offset in the receiver LO is usually acquired at the beginning of each packet and later tracked in the data demodulation mode. Methods for estimation and compensation of DAC/ADC clocks frequency offset by processing of sampled data also exist. In this paper, we present an algorithm for joint tracking and compensation of the two frequency offset phenomena. Simulation results show that the algorithm works quite effectively even in the presence of large amount of offsets.

Keywords:

OFDM , Wireless LAN , frequency offset , tracking