Development and saw device implementation of a new weighted stepped chirp code signal for direct sequence spread spectrum communications systems

This work introduces the new weighted stepped chirp code signal for direct sequence spread spectrum (DS/SS) communications systems. This code signal uses the truncated cosine series functions as the chip functions. This code signal is the result of discretizing a continuous wave (CW) chirp which results in enhanced performance versus a pseudonoise (PN) code and equivalent performance and easier implementation than a CW chirp. This code signal will be shown to possess improved compression ratio (CR), peak sidelobe level (PSL), integrated sidelobe level (ISL), and bit error rate (BER) when compared to a PN code of identical code length and chip length. It also will be shown to have a similar CR, PSL, ISL, and loss in processing gain (LPG) when compared to a CW chirp with identical pulse length and frequency deviation. The code signal is implemented on surface acoustic wave (SAW) devices which can be used as the code signal generator at the transmitter and the correlator at the receiver in a DS/SS communication system. SAW design considerations for the weighted stepped chirp signal are discussed. Experimental data is presented and compared to the predicted CR, PSL, ISL, LPG, and BER