NOVEL NARROW-BAND INTERFERENCE REJECTION FOR AN ASYNCHRONOUS SPREAD-SPECTRUM WIRELESS MODEM USING A SAW CONVOLVER

An asynchronous spread spectrum (SS) wireless modem has been implement ed using an efficient ZnO-SiO2-Si surface acoustic wave (SAW) convolve r. The modem is based on a direct-sequence/frequency-shift-keying (DS/ FSK) method for the modulation. The demodulation is carried out asynch ronously 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 c ontrol. A notched-reference-signal circuit and a self-convolution canc eler are implemented in the SS modem for the reference signal control. It was found that the antijam capability for narrowband interference is at least -24 dB of desired-to-undesired power ratio (D/U); the impr ovement of the antijam capability is 16 dB up as compared with our pre vious SS modem.