JZUS - Journal of Zhejiang University SCIENCE

Frontiers of Information Technology & Electronic Engineering 2015 Vol.16 No.9 P.796-804

A block zero-padding method based on DCFT for L1 parameter estimations in weak signal and high dynamic environments

Author(s): Chao Wu, Lu-ping Xu, Hua Zhang, Wen-bo Zhao
Affiliation(s): School of Aerospace Science and Technology, Xidian University, Xi’an 710126, China
Corresponding email(s): wuchaoid@126.com
Key Words: Threshold detection, Discrete chirp-Fourier transform, Block zero-padding, High dynamic, Weak L1 signal acquisition

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Abstract: weak L1 signal acquisition in a high dynamic environment primarily faces a challenge: the integration peak is negatively influenced by the possible bit sign reversal every 20 ms and the frequency error. The block accumulating semi-coherent integration of correlations (BASIC) is a state-of-the-art method, but calculating the inter-block conjugate products restricts BASIC in a low signal-to-noise ratio (SNR) acquisition. We propose a block zero-padding method based on a discrete chirp-Fourier transform (DCFT) for parameter estimations in weak signal and high dynamic environments. Compared with the conventional receiver architecture that uses closed-loop acquisition and tracking, it is more suitable for open-loop acquisition. The proposed method combines DCFT and block zero-padding. In this way, the post-correlation signal is coherently post-integrated with the bit sequence stripped off, and the high dynamic parameters are precisely estimated using the threshold set based on a false alarm probability. In addition, the detection performance of the proposed method is analyzed. Simulation results show that compared with the BASIC method, the proposed method can precisely detect the high dynamic parameters in lower SNR when the length of the received signal is fixed.

高动态弱信号环境下针对L1信号参数估计的基于离散chirp-Fourier变换块补零方法

目的：为克服高动态弱信号环境下信号的积分峰值受比特符号翻转和频率误差的影响，提出一种基于离散chirp-Fourier变换块补零方法。
创新点：与传统闭环捕获和跟踪的接收机结构相比，该方法适用于开环捕获。该方法结合了离散chirp-Fourier变换和块补零思想，能够使后相关信号在剥离比特符号后进行相干积累并同时进行高动态参数精准预测。同时，对所提方法的检测性能进行分析推导捕获概率和虚警概率表达式。
方法：首先，后相关信号通过块补零处理被分为一些块，然后这些块通过离散chirp-Fourier变换处理。以这种方式比特翻转对积分峰值的影响可以被削弱，同时后相关信号可以进行相干积累。最后通过阈值检测积分峰值来完成高动态参数的预测，这个阈值是通过设定的虚警概率得出的。仿真结果表明当接收信号长度一定时，本文方法较BASIC方法能在更低的信噪比下检测到高动态参数。
结论：本文结合离散chirp-Fourier变换和块补零思想，在弱信号高动态环境下提出基于离散chirp-Fourier变换的块补零方法。仿真结果表明本文方法较BASIC方法在更低的信噪比下预测高动态参数。与利用传统接收机结构的闭环捕获和跟踪方法的相比，这种方法是一种开环捕获的方法，非常适合软件无线电接收机。

关键词：阈值检测；离散chirp-Fourier变换；块补零；高动态；弱L1信号捕获

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