Pinch the Correlation Function: A Method to Improve Delay Estimation in Multipath

Chun Yang and Andrey Soloviev

Abstract:	Correlation at an intermediate frequency (IF) produces a composite correlation function, which is made of an envelope being that of the underlying code and an internal structure being that of the IF carrier. The IF carrier correlation introduces zerocrossings to the code correlation as if it pinches the code correlation envelope at the zero-crossing points, having the effect of creating a main peak and secondary peaks. The quick decay towards zero-crossings sharpens the main peak, which is desired for accurate timing of the direct signal while isolating close-in multipath and spoofing signals. Either sequential or parallel use of variable IF correlation (VIC) helps lock onto the main peak among secondary peaks without ambiguity and false lock. In this paper, a zero-padded spectrum translation (ZPST) technique is introduced to enable VIC for baseband signals, which is especially suitable for software-defined radios (SDR) that make use of FFT-implemented correlation and very natural for radio transmissions that specify reference signals in the frequency domain such as pilot subcarriers in OFDM (e.g., Wi-Fi, 4G LTE, and DVB-T). Results of simulation and of processing in-the-air DVB-T data are presented to demonstrate the principle and viability of VIC.
Published in:	Proceedings of the 2017 International Technical Meeting of The Institute of Navigation January 30 - 2, 2017 Hyatt Regency Monterey Monterey, California
Pages:	347 - 364
Cite this article:	Yang, Chun, Soloviev, Andrey, "Pinch the Correlation Function: A Method to Improve Delay Estimation in Multipath," Proceedings of the 2017 International Technical Meeting of The Institute of Navigation, Monterey, California, January 2017, pp. 347-364. https://doi.org/10.33012/2017.14951
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