宽带DBF系统多通道校正及性能分析

针对数字波束形成(DBF)技术在宽带扩频通信系统中的应用,提出了一种基于复数傅里叶变换(CFFT)的宽带多通道校正方法。采用宽带线性扫频信号作为通道幅相误差校正的测试信号,在采集实际接收机数据的基础上,分析了信噪比、频谱泄漏以及由通道校正滤波器引起的群时延对校正精度的影响。通过修正复系数FIR滤波器(CFIR)的频域响应特性可以有效消除群时延的影响。依据宽带测试信号的时域和频域特性,选择适当的FFT点数,解决了测试信号频谱泄漏引起的校正精度低的问题。理论分析与实测结果都表明了该方法的有效性。利用实际数据仿真了天线阵列波束方向图,结果显示校正后的波束图十分接近理想情况下的波束图,两者峰值增益相差仅仅0.1dB,指向误差近似为0。

Multi-channel Calibration and Performance Analysis of Broadband DBF system

A new broadband multi-channel calibration method based on complex FFT(CFFT) for DBF system in broadband spread spectrum communication is presented.Linear frequency modulation (LFM) signal is considered as calibration test signal.Three factors affecting the performance of the proposed algorithm are analyzed,including signal-noise ratio (SNR),frequency spectrum leakage and group-delay.In order to eliminate group-delay effect,the frequency response of calibration filter is modified.Based on time and frequency characteristics,the precision of residual errors after calibration can be improved by selecting proper number of FFT points to remove frequency spectrum leakage effect.The results show that the beam pattern after calibration is close to the ideal beam pattern after avoiding the influence of the several factors.The difference of the peak gain between the beam pattern after calibration and the ideal beam pattern is 0.1dB,and the difference of direction is approximately zero.