Code optimization for direct sequence spread spectrum and SAW-matched filter implementation

Abstract

This paper introduces a new optimization algorithm for the minimization of the time sidelobes of the correlation function of a pseudonoise (PN) sequence by applying dynamic weighting to the sequence. The resulting optimized time sidelobe level sequences are to be used in direct sequence spread spectrum (DS-SS) systems with digital modulations such as BPSK, DPSK, QPSK, etc. The new optimization algorithm starts with a PN sequence. It first optimizes the correlation time sidelobes for the case where the consecutive data bits are identical (11 or 00). It then optimizes the correlation time sidelobes for the case of alternating consecutive data bits (10 or 01). The suppressed time sidelobe level sequences are derived by iterating these algorithms alternately starting from the initial PN sequence. The derived suppressed time sidelobe sequences show excellent correlation characteristics when compared to conventional PN sequences such as maximal length sequences, Gold sequences and Barker codes. Surface acoustic wave (SAW) devices were used to implement the optimized time sidelobe level sequences in a matched filter pair. The design of the apodized SAW-matched filters and their predicted second order effects are presented. The experimental results for the SAW-matched filters for the optimized time sidelobe level sequences derived from a Barker code were found to be in good agreement with the theoretical predictions from this new algorithm.

Sensors Network for Ultrasonic Ranging System

“…Griep et al (1995) adopted a global optimization technique to select proper coding signal for multiple-user ultrasonic ranging sysrem. Osamu Hikino and his colleagues (Hikino O., Belkerdid M., & Malocha D, 2000) optimized PN sequences to reduce autocorrelation function's side-lobe. Nakahira et al (2005) used a combination of simulated annealing and hill climbing to minimize the peaks in the cross-correlation function as well as minimize the maximum side-lobe in the autocorrelation function.…”

Optimization of Matched Chaotic Frequency Modulation Excitation Sequences for Multichannel Simultaneously Triggered Ultrasonic Ranging System

“…Griep, Ritcey, and Burlingame (1995) adopted a global optimization technique to select proper coding signal for multiple-user ultrasonic ranging system. Hikino, Belkerdid, and Malocha (2000) optimized PN sequences to reduce autocorrelation function's side-lobe. Nakahira et al (2005) used a combination of simulated annealing and hill climbing to minimize the peaks in the cross-correlation function as well as minimize the maximum side-lobe in the autocorrelation function.…”

Optimized Pseudorandom BASK Emission Sequences for Ultrasonic Multi-Life Location System

“…The better correlation characteristics of emission sequences mean that their echoes should have sharper autocorrelation and flatter cross-correlation. To obtain the better correlation characteristics of emission sequences, Osamu Hikino et al [11] optimized PN sequences to reduce autocorrelation side-lobe. Nakahira [8] used a combination of simulated annealing and hill climbing to minimize the maximum side-lobe in the autocorrelation as well as minimize the peaks in the cross-correlation.…”