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Almost perfect sequences applied for ionospheric oblique backscattering detection
Author(s) -
Chen Gang,
Zhao Zhengyu,
Pu Tianyao,
Huang Yujie,
Zhu Guoqiang
Publication year - 2009
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/2009rs004148
Subject(s) - autocorrelation , sequence (biology) , ionosphere , doppler effect , physics , pseudorandom binary sequence , pseudorandom number generator , depth sounding , phase (matter) , complementary sequences , binary number , optics , mathematics , algorithm , geology , statistics , genetics , arithmetic , oceanography , quantum mechanics , astronomy , biology
Pseudorandom sequences are often used in radio systems; however, the nonzero out‐of‐phase autocorrelation of many binary sequences induces range sidelobes which significantly reduce the echo signal‐to‐noise ratio (SNR). In this paper, the use of almost perfect sequences, exhibiting zero out‐of‐phase autocorrelation except one value in the middle is examined with reference to common m sequences and perfect sequence. The ambiguity functions demonstrate that it is possible to use the almost perfect sequences for ranging without sidelobes and that their Doppler measurement performance is similar to m sequence of the same length. This is an important result for ionospheric oblique backscattering detection where the echoes are superposed and where range sidelobes can submerge the main lobes of weak signals. The 124‐bit almost perfect sequence and the 127‐bit m sequence are applied to the Wuhan Ionospheric Oblique Backscattering Sounding System for sequence testing. The test results have proven that the almost perfect sequence exhibits a higher echo SNR for the same detection conditions.