Almost perfect sequences based on cyclic difference sets

作者：Chen Gang^*; Zhao Zhengyu

来源：Journal of Systems Engineering and Electronics, 2007, 18(1): 155-159.

DOI：10.1016/S1004-4132(07)60067-X

• perfect sequence
• almost perfect sequence
• cyclic difference sets
• autocorrelation coefficients
• side lobes
• ionospheric sounding

The perfect sequences are so ideal that all out-of-phase autocorrelation coefficients are zero, and if the sequences are used as the coding modulating signal for the phase-modulated radar, there will be no interference of side lobes theoretically. However, it has been proved that there are no binary perfect sequences of period 4 < n <= 12 100. Hence, the almost perfect sequences with all out-of-phase autocorrelation coefficients as zero except one are of great practice in engineering. Currently, the cyclic difference set is one of most effective tools to analyze the binary sequences with perfect periodic autocorrelation function. In this article, two characteristic formulas corresponding to the autocorrelation and symmetric structure of almost perfect sequences are calculated respectively. All almost perfect sequences with period n, which is a multiple of 4, can be figured out by the two formulas. Several almost perfect sequences with different periods have been hunted by the program based on the two formulas and then applied to the simulation program and practical application for ionospheric sounding.

• 出版日期2007-3
• 单位武汉大学