Novel Narrowband Interference Rejection for an Asynchronous Spread Spectrum Wireless Modem Using a SAW Convolver

Hiroyuki NAKASE

IEICE TRANSACTIONS on Communications   Vol.E76-B    No.8    pp.947-954
Publication Date: 1993/08/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Spread Spectrum Techniques and Applications)
spread spectrum,  SAW convolver,  asynchronous SS modem,  notched reference signal,  programmable PN code,  self-convolution canceler,  

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An asynchronous spread spectrum (SS) wireless modem has been implemented using an efficient ZnO-SiO2-Si surface acoustic wave (SAW) convolver. The modem is based on a direct-sequence/frequency-shift-keying (DS/FSK) method for the modulation. The demodulation is carried out asynchronously utilizing the coherent correlation characteristics of the SAW convolver. In order to improve the narrowband interference rejection capability, we propose a new technique based on the reference signal control. A notched-reference-signal circuit and a self-convolution canceler are implemented in the SS modem for the reference signal control. It was found that the antijam capability for narrowband interference is at least -24dB of desired-to-undesired power ratio (D/U); the improvement of the antijam capability is 16dB up as compared with our previous SS modem.