Title :
Making nonlinear interference rejection work in QPSK-SS receivers
Author :
Abrams, Burton S.
Author_Institution :
Zeger-Abrams Inc., Glenside, PA, USA
Abstract :
A strong memoryless nonlinearity excited by a strong interference and a weak QPSK spread spectrum (SS) signal produces the weak signal and an intermodulation product (IMP) with equal amplitudes. With QPSK modulation used for both the data and the SS code, it is shown that the conventional QPSK-SS demodulator´s SS processing cannot discriminate between the signal and the IMP even though it can discriminate the weak signal from the strong interference. An alternative QPSK-SS configuration is presented which overcomes this IMP interference vulnerability while still suppressing the strong interference
Keywords :
demodulation; demodulators; filtering theory; interference suppression; intermodulation; matched filters; quadrature phase shift keying; radio receivers; radiofrequency interference; spread spectrum communication; QPSK modulation; QPSK spread spectrum signal; QPSK-SS demodulator; QPSK-SS receivers; data; intermodulation product; matched filter demodulation; memoryless nonlinearity; nonlinear interference rejection; spread spectrum code; spread spectrum processing; strong interference suppression; weak signal; Additives; Demodulation; Interference suppression; Matched filters; Modulation coding; Phase modulation; Quadrature phase shift keying; Repeaters; Signal processing; Spread spectrum communication;
Conference_Titel :
Military Communications Conference, 1995. MILCOM '95, Conference Record, IEEE
Conference_Location :
San Diego, CA
Print_ISBN :
0-7803-2489-7
DOI :
10.1109/MILCOM.1995.483632
