CS-POCET: A Dual-frequency Constant Envelope Multiplex Method for GNSS Signals

Z. Zhou, J. Wei, Z. Tang, T. Yan

Abstract:	In modernization Global navigation satellite system(GNSS), there is strong demand for multiplexing multiple binary spreading signals on two adjacent frequencies, while the presented multiplexing methods are most focus on signals at one carrier frequency, there are only a few methods can multiplex signals at dual-frequency, the alternate binary offset carrier (AltBOC) method ,TD-AltBOC method and the rotating Dual-QPSK method have strict constraint on relative power allocation among component signals, and the signals on each carrier frequency must be two quadrature signals; the POCET method can combine any signals at different carrier frequencies, but it’s desired storage space will rapidly increase with sampling rate increased, it’s power efficiency will also be lower and lower with sampling rate increased; In this paper we proposed a CS-POCET (POCET for complex subcarrier signals) method; it is suitable for the situation that several signals at the transmitting frequency and another component signal at the frequency deviate from transmitting frequency with a frequency difference of . As a solution, we can first modulate the signal deviate from transmitting frequency with a complex subcarrier, thus, we obtain two quadrature signals, and their center frequency is shifted to transmitting frequency, in theory, any method for single frequency combining can be used to combine all signals, but a problem is that the correlates between the two quadrature signals generated by complex subcarrier modulation are not independence, so in fact, the general multiplex methods are unsuitable, and CS-POCET is proposed to combine signals modulated by complex subcarrier into a constant envelope signal. This approach generates an optimized table of transmitted phase values, which correspond to the combinations of bits of the codes. For implementation of satellite, it looks up the table by combination of bits to get a phase value, and then modulated the carrier by this phase. The results of our technique are presented later. Finally the simulation of cross-correlations between the composite signal and component signals are presented, and the code tracking error for component signals are also depicted. The simulation results show that CS-POCET technology is an effective approach to combine dual-frequency signals with complex subcarrier modulation.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	835 - 843
Cite this article:	Zhou, Z., Wei, J., Tang, Z., Yan, T., "CS-POCET: A Dual-frequency Constant Envelope Multiplex Method for GNSS Signals," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 835-843.
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