This paper introduces a 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, and it is the result of discretizing a continuous wave (CW) chirp that 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 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 shown 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 acoustic wave (SAW) devices that will be used as the code generator at the transmitter and the correlator at the receiver. The design considerations for the SAW device implementation of the code signal are discussed, including the effects of intersymbol interference. Experimental data is presented and compared to the predicted results for 8 different SAW devices examining the effects of code length (9 or 13 chips), weighting (uniform, cosine-squared, and Hamming), and sampling on the performance of the code signal.

This paper discusses a new surface acoustic wave (SAW) device implementation of a weighted stepped chirp code signal for use in direct sequence spread spectrum communications systems. The theoretical performance of the code signal is evaluated including the following figures of merit: compression ratio, peak sidelobe level, integrated sidelobe level, processing gain, and probability of error. The design considerations for the SAW device implementation of the code signal are discussed including the effects of intersymbol interference. Experimental results are presented for 8 different SAW devices examining the effects of code length (9 or 13 chips), weighting (uniform, cosine-squared, and Hamming), and sampling on the performance of the code signal.

A critical parameter in any finite impulse response (FIR) design is the impulse response length, which must be optimized for the given design specifications in order to reduce the size of the filter. To this end, many design algorithms have been introduced, such as Remez exchange, linear programming, and least mean squares. A new algorithm has been derived that is simple, efficient, and accurate for the design of arbitrary filter specifications and requires fewer computations than many other FIR approaches. This paper provides the definition of the basic functions used for the design process. An overview of the design process is given and the design technique used to design filters with tailored passband and stopband responses to yield a near-optimum time length is presented. This design can be very useful when compensating for the effects of a second transducer or other second order effects in surface acoustic wave (SAW) devices. The effects of monotonically increasing sidelobes on the impulse response length are discussed and illustrated. The addition of arbitrary phase response to the filter design process is discussed. The results of the current FIR approach are discussed and compared with other design techniques.