GPS REFERENCE FREQUENCY DRIFT ESTIMATION FROM PDC-HANDSET VCO-BURST USING VCO BURST INFORMATION RECEIVED PERIODICALLY THROUGH PDC HANDSET

摘要

PURPOSE: A GPS(Global Positioning System) reference frequency drift estimation from a PDC(Personal Digital Communicator)-handset VCO(Voltage Controlled Oscillator)-burst is provided to improve initialization by using the VCO burst information received periodically through the PDC handset. CONSTITUTION: An NCO(Numerical Controlled Oscillator)(204) periodically receives an NCO value to which an NCO output frequency follows. A first look-up table(220) is used to approximate a sinusoidal wave from an in-phase version of the NCO output frequency. A first mixer(226) is connected to an output of the first look-up table and couples the output to a gated master clock signal to generate an I-mix signal output. An I-correlator(228) has an I-correlation output and correlates the I-mix signal output. A second look-up table(216) is used to approximate a cosine wave from a quadrature phase version of the NCO output frequency. A second mixer(227) is connected to an output of the second look-up table and couples the output to the gated master clock signal to generate a Q-mix signal output. A Q-correlator(230) has a Q-correlation output and correlates the Q-mix signal output.