Frequency-Domain Receiver for Modernization GPS Signals Via Full-Band Multi-Code Processing

Chun Yang

Abstract:	The three GPS frequencies will soon be populated with nine to ten different codes, namely, C/A-code, P(Y)-code, and M-code on L1 (and possibly an L1C-code); P(Y)- code, M-code, and L2C-code (with CM- and CL-code) on L2; and I5-code and Q5-code on L5. Conventional GPS receiver architecture would require the same amount of hardware channels for each GPS satellite in view, each having four to six correlators. Although integrating hundreds and even thousands of correlators is not a technological issue today, the resulting size, power consumption, and cost per integrated circuit (IC) chip are of practical concerns. In this paper we present a frequency-domain software GPS receiver with a full-band multi-code simultaneous processing feature. It is based on the observation that the maximum bandwidth is 24 MHz for L1 and L2 and 20 MHz (null to null) for L5 and the minimum bandwidth is 2 MHz (null to null) for the C/A-code on L1 and the CM- and CL-codes on L2. With either the Nyquist sampling or a bandpass sampling scheme, these GPS signals have to be sampled at least at 50 MHz. If a 50,000-point complex fast Fourier transform (FFT) or an equivalent transform can be carried out continuously every 1 millisecond (ms), then all the GPS codes within each frequency band are made available simultaneously. Frequency-domain algorithms are described in this paper for acquisition and tracking of all modernization codes using spectrum segmentation and translation. This includes the short cyclic C/A-code, long P(Y)-code, long split-spectrum M-code, cascaded PRN and NH-codes on L5, and time division multiplexed (TDM) L2C code. Simulation results are presented to illustrate the advantages of this frequency-domain GPS receiver architecture. In particular, the different acquisition schemes are readily applicable to the M-code. This includes the full-band coherent, single sideband, noncoherent sideband combination, and cross sideband acquisition, which are comparatively evaluated.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	1564 - 1576
Cite this article:	Yang, Chun, "Frequency-Domain Receiver for Modernization GPS Signals Via Full-Band Multi-Code Processing," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 1564-1576.
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