In-Band Interference Suppression for GPS/GLONASS

M.Zhodzishsky, D.Cherniavsky, A.Kirsanov, M.Vorobiev, V.Prasolov, A.Zhdanov, J.Ashjaee

Abstract:	The operation of a GPS receiver can severely be limited or completely disrupted in the presence of in-band interfer-ence and jamming signals. The threat of in-band interfer-ing and jamming signals increases daily as new communi-cation systems are launched and the radio frequency spectrum becomes more populated. The threat is not only from the interfering signals themselves but also from their harmonics fall inside the GPS band. In this paper we present technique that we have integrated inside the digital signal processor chip to suppress in-band interference in any one of the GPS L1/L2, GLONASS L1/L2 as well as direct spread spectrum radio modem in 902-928 MHz band (patent pending). The technique is based on two completely digital compensation type sup-pressors with quadrature processing of the difference of an input interference signal and an appropriate copy of the estimated interfering signal used for compensation. The compensation signal is used to suppress continuous (CW), narrow band (NB) and pulse interference whose powers are comparable or significantly exceed the system noise power in the reception band (about 16 MHz). Each Suppressor contains an 8-bit ADC, which converts the IF-signal into digital samples with the quantization frequency of 40 MHz, and three anti-jam modules tracking for interference frequency. The characteristic of the loops, as well as the rejection bands, are dynamically adjusted according to the characteristics of the interfering signal. The rejection band at the -40 dB level may be adjusted from 5 kHz up to 80 kHz. The interference suppression can be up to 60 dB. Two completely digital scanning spectrum analyzers with adjustable resolution are used for analyzing interfering signals. Suppressor operation is software controlled with the reaction time of 0.82 ms. Two of such suppressors are integrated inside our Para-digm chip along with 40 universal GPS-GLONASS chan-nels and spread spectrum radio modems (direct and fre-quency hopping). Up to 6 in-band interference/jammers can be suppressed simultaneously. The power consumption of the total system, including all GPS-GLONASS satellite tracking and spread spectrum radio receiver is less than 3 Watts.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	769 - 773
Cite this article:	M.Zhodzishsky,, D.Cherniavsky,, A.Kirsanov,, M.Vorobiev,, V.Prasolov,, A.Zhdanov,, J.Ashjaee,, "In-Band Interference Suppression for GPS/GLONASS," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 769-773.
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