Broadband Interference Cancellation Using Digital Beam Forming and a Software Receiver

Y. T. Jade Morton, Liyeh L. Liou, David M. Lin, James B. Y. Tsui and Qihou Zhou

Abstract:	This paper presents the performance analysis of a digital beam forming algorithm used in conjunction with a software GPS receiver to mitigate broadband interference to GPS signals. The beam form processor minimizes the total receiver input signal power while maintaining a constant gain along a known satellite direction. Both space-only and space-time processing were implemented in the study. The study was performed using experiment data collected in an anechoic chamber to obtain GPS and interference signals. A two by two GPS antenna array and a four channel radio frequency front end were used to collect and digitize the GPS signals in the controlled broadband interference environment. The interference power levels used were +20, +30, and +40 dB above the GPS signal power. A software GPS receiver was used to perform coarse and fine acquisition of GPS signals to evaluate the performance of the beam former processor. The result showed that both space-only and space-time processors can effectively mitigate broadband interference at all three power levels if a single interference source is present. For multiple interference sources, the performances of both processor implementations degrade as the interference power level increases and the number of interference sources increases. For the space-time beam former, we implemented one, two, and three taps for performance comparisons. For each tap number, we used six different delay times. An optimal number of taps and delay time were identified for the integrated receiver system based on the receiver coarse and fine acquisition performance. The optimal space-time beam former implementation slightly outperforms the space-only beam former in terms of the total number of successfully acquired satellites and the beam former output signals signal-to-noise ratio. This advantage, however, is overshadowed by the higher number of false alarms observed in the space-time implementation. Detailed analysis and results for the beam former performances are presented in the paper.
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:	1275 - 1284
Cite this article:	Morton, Y. T. Jade, Liou, Liyeh L., Lin, David M., Tsui, James B. Y., Zhou, Qihou, "Broadband Interference Cancellation Using Digital Beam Forming and a Software Receiver," 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. 1275-1284.
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