A GNSS receiver tracks the AltBOC (15, 10), or composite E5a and E5b, codesusing hardware that locally generates the complex composite signal bycombining separately generated real and the imaginary components of thecomplex signal. To track the dataless composite pilot code signals that are onthe quadrature channel of the AltBOC signal, the receiver operates PRN codegenerators that produce replica E5a and E5b PRN codes and square wavegenerators that generate the real and imaginary locally generated complexcomposite code. The receiver removes the complex composite code from thereceived signal by multiplying the received signal, which has beendownconverted to baseband I and Q signal components, by the locally generatedcomplex composite code. The receiver then uses the results, which arecorrelated I and Q prompt signal values, to estimate the center frequencycarrier phase angle tracking error. The error signal is used to cotnrol anumerically controlled oscillator that operates in a conventional manner, tocorrect the phase angle of the locally generated center frequency carrier. Thereceiver also uses early and late versions of the locally generated complexcomposite pilot code in a DLL, and aligns the locally generated compositepilot code with the received composite pilot code by minimizing thecorresponding DLL error signal. Once the receiver is tracking the compositepilot code, the receiver determines its pseudorange and global position in aconventional manner. The receiver also uses a separate set of correlators toalign locally generated versions of the in-phase composite PRN codes with thein-phase channel codes in the received signal, and thereafter, recover thedata that is modulated thereon.
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