时域宽带恒定束宽波束形成器的优化设计

Optimum Design on Time Domain Broadband Beamformer with Constant Beamwidth

为了使用较低阶次的FIR滤波器组实现高精度的时域恒定束宽波束形成器,本文提出了一种优化设计方法。此方法使用了数字延迟线和FIR滤波器组相结合的宽带波束形成器结构。在FIR滤波器组的设计中,使用半定规划的优化方法,使设计波束的主瓣逼近期望波束,同时使用矩阵不等式约束旁瓣高度。在建立最优化问题时考虑了设计频段上的所有频率点,因此可以得到全设计频段上束宽恒定的波束形成器。应用本文的方法,针对8元均匀离散圆弧阵设计时域恒定束宽波束形成器,并与已有方法的设计结果进行了比较,验证了此方法的正确性和有效性。

In order to precisely design time domain broadband beamformer with constant beamwidth, an optimum design method using semi-definite programming is presented in this paper. By combining the beamformer structure of a FIR filter fan and digital delay lines, the order of a FIR filter fan is reduced. In optimum design procedure, the beampattem at each frequency bin is constrained as same as the desired beampattem in the mainlobe region and at same time matrix inequality constrains are used to limit the height of sidelobe. All frequencies in designing frequency band are considered, so the designed beamformer can give constant beamwidth beampattem at entire designing frequency band. By computer simulations, it is shown that the presented method can give more accurate time domain constant beamwidth beamformer with low-order filter fan compared to traditional methods.