SAW device implementation of a weighted stepped chirp code signal for direct sequence spread spectrum communications systems

This paper introduces a new weighted stepped chirp code signal for direct s equence spread spectrum (DS/SS) communications systems. This code signal us es the truncated cosine series functions as the chip functions, and it is t he result of discretizing a continuous wave (CW) chirp that results in enha nced performance versus a pseudonoise (PN) code and equivalent performance and easier implementation than a CW chirp. This code signal will be shown t o have improved compression ratio (CR) and peak sidelobe level (PSL) versus a PN code with identical code length and chip length. It also will be show n to have a similar CR and PSL compared to a CW chirp with identical pulse length and frequency deviation. The code signal is implemented on surface a coustic wave (SAW) devices that will be used as the code generator at the t ransmitter and the correlator at the receiver. The design considerations fo r the SAW device implementation of the code signal are discussed, including the effects of intersymbol interference. Experimental data is presented an d compared to the predicted results for 8 different SAW devices examining t he effects of code length (9 or 13 chips), weighting (uniform, cosine-squar ed, and Hamming), and sampling on the performance of the code signal.