A METHOD AND APPARATUS OF ESTIMATING CARRIER FREQUENCY

摘要

A method and apparatus of estimating carrier frequency, which is including: demodulate forward pilot channel symbols in succession at each arm of the Rake receiver; multiply demodulated value by the conjugation of the previous one at each arm of the Rake receiver; add up the multiplying value of each arm of the Rake receiver and obtain complex z=Ae<jϕ>, where ϕ is the phase rotation of the estimated successive symbles; caculate ϕ=arctan(Im[z]/Re[z]) and get the phase rotation between the successive symbles; caculate the residual carrier frequency offset Deltaf=ϕV(2piTd), where Td is the duration of a symbol; send Deltaf to a loop filter for processing and figure out corresponding frequency control words; a Number Controlled Oscillator read in the frequency control words to generate corresponding frequency. It is used for frequency variation of Crystal Oscillator and random Doppler shift, and it can keep the frequency offset within the acceptable range by correcting the VCO or NCO to track the average offset thereinto.