Design and Practical Implementation of Multi-Frequency RF Front Ends Using Direct RF Sampling

M.L. Psiaki, S.P. Powell, H. Jung, P.M. Kintner Jr.

Abstract:	The use of direct RF sampling has been explored as a means of designing multi-frequency RF front ends. Such front ends will be useful to future GNSS receivers which seek to exploit new signals that are slated to appear in the GPS L2 and L5 bands and in the Galileo bands. The design of a practical multi-frequency direct RF sampling front end is dependent on having an ADC that can accept input signals with bandwidths up to 2 GHz and that can sample at frequencies up to 100 MHz or higher. The principal of direct RF sampling is used to alias all frequency bands of interest onto portions of the Nyquist spectrum that do not overlap. This criterion can be met through careful selection of a sampling frequency that obeys a complicated set of mathematical constraints. The front end also requires a multi-frequency bandpass filter that passes the frequency bands of interest while rejecting out-of-band signals and noise. Bit selection and gain control logic is also useful as a means of reducing the data rates out of the front end without sacrificing much sensitivity. A prototype front end has been designed, built and tested. It receives GPS C/A code on the L1 frequency and GPS P(Y) code on both L1 and L2. Dual-frequency signals with received carrier-to-noise ratios in excess of 52 dB Hz have been acquired and tracked using this system.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	90 - 102
Cite this article:	Psiaki, M.L., Powell, S.P., Jung, H., Kintner, P.M., Jr., "Design and Practical Implementation of Multi-Frequency RF Front Ends Using Direct RF Sampling," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 90-102.
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