GPS L5 receiver implementation issues
Résumé
The new L5 signal is QPSK-modulated, with a nominal carrier frequency of 1176.45 MHz and a bandwidth of 24 MHz. Its two components have each a different spreading code clocked at 10.23 MHz. The in-phase component, also called the data channel, carries the navigation message at 100 symbols per second (50 bits per second with a convolutional encoder) while the quadrature component, called the pilot channel, carries no message at all. The data and pilot L5 spreading codes are each modulated with a distinct Neumann-Hoffman code clocked at 1kHz. The specified power is such that the received levels on the ground should be -154.9 dBW (i.e. -157.9 dBW for each component). Such a new signal structure implies new receiver structures for acquisition, tracking and data demodulation. In particular, different strategies can be envisioned for L5 codes and Neumann-Hoffman acquisition, and several correlator outputs using data and pilot signals can be combined to form the tracking loops discrimination functions. The aim of the proposed paper is to show results of an analysis of the possible structures for acquisition of the L5 codes and of the Neumann-Hoffman codes, as well as structures used for L5 signal tracking, and evaluated performance of these acquisition and tracking structures.
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