提出了一种迭代算法，在FIR数字滤波器的自适应设计过程中自动改变各个频率指标上代价因子的值，最终实现代价因子的最优取值。利用这种改进方法，可以实现FIR数字滤波器和设计指标之间的最佳拟合。给出了两个设计实例，其中幅度响应每倍频程衰减6dB的滤波器，可以用于模拟水声阵列接收的宽带海洋噪声，而高精度时延的滤波器，则可以实现波束形成中所需要的非整数倍采样间隔的时延。

A wide-band beamforming scheme for uniform circular array is proposed to improve the detection performance for weak passive signals in this paper. In our processing scheme, the wide-band signals sampled from the underwater acoustic array are firstly decomposed into different narrow-band signals using FFT, and then the narrow-band high gain beamforming process is performed for each subband of the FFT outputs. The subband beamformer outputs are squared nd summed using the Eckart weighting coefficients. The length of FFT is selected to make every subband satisfy the condition of narrow-band assumption. The fifty percent of overlapping ratio and-30 dB sidelobe level chebyshev window are used for FFT processing to obtain better system performance. This approach was employed to process some wide-band experimental data recorded from a 24-element circular array at a lake in China. Compared to the conventional beamforming, enhanced detection performance is obtained without improving the complexity of realization.

提出了一种任意结构阵列宽带恒定束宽波束形成的新方法。该方法把任意结构阵列的响应向量表示成以Bessel函数为核函数的级数之和，并将高阶项截断，然后把频带内各个频率点上的阵列响应向量转化到参考频率上，从而得到恒定束宽波束形成向量，使得各个频率上的波束和参考波束相同。同时，本文还给出了一种基于自适应处理的参考波束优化方法。结合均匀分布离散圆阵所作的计算机仿真验证了本文所提方法的有效性。

将阵元域高分辨加权子空间拟合算法（wsF算法）推广到了波束域中，利用声系统接收基阵波束输出信息估计目标方位。由于波束输出可以看作是，一个阵元数为波束个数的虚拟阵的阵元输出，而在大多数的水声系统中，参与确定某个来向的信号方位的波束数通常远小于阵元数，从而算法的运算量得以大大降低。针对某水声系统接收基阵波束输出所作的计算机仿真结果表明，波束域wSF算法应用到实际的水声系统时，可以保持其在阵元域中估计目标方位的优越性能。

In this paper, a new method is presented to design low-sidelobe wideband constant beamwidth beamformers (WCBB) in time domain, which alleviates the effect caused by array mismatch errors by applying the measured array models into the design procedure. A combination of FIR filters and digital delay lines is used in the beamformer structure to reduce the order of FIR filters. In FIR filter design, the semi-definite programming is utilized which is able to constrain both the mainlobe shapes and the sidelobe levels within the whole design frequency band. Results from lake experiments with a practical sonar system verified the effectiveness of the proposed method.

针对空气中基于时延的任意阵列被动定向问题，提出了一种基于最小二乘法的统一模型，并对影响该模型定向精度的几种因素进行了深入的分析。由于可以用于任意结构阵形，该统一模型能够方便地分析阵元位置误差引起的定向误差，能够避免实际系统由于更换阵形而带来的较大的软件变化；并且，当实际阵列与设计模型存在较大误差时，可以方便地改变模型参数使其与实际的阵列匹配。对影响定向误差的各种因素的分析和计算机仿真，为确定和提高被动声定向的精度提供了有价值的参考。

The generalized steering vector is blindly estimated from the CM array, where the steering vectors to all coherent signals are reconstructed directly by using the property of sub-array shift-invariance. When used as the array weighting, the steering vectors will provide recovered signals in corresponding beams. DOAs can be estimated from the angular spectrum subsequently. esults from the computer simulations and the real data analysis.are in good agreement with theoretical analysis. Our method not only can resolve closely spaced coherent signals, but also is shown to be more robust to system errors compared to some other DOA estimation algodthms.

本文内容分理论研究和实验研究两部分。首先，对高分辨目标方位估计算法IMP提出了两种改善其收敛速度的方法。利用这两种改进方法，可将原算法的收敛速度提高一倍。计算机仿真验证了改进方法的有效性。其次，针对该算法进行了水池实验研究，实验分析结果显示，IMP算法能够有效地分辨和估计非等功率的两个相干信号源。

The problem of beamforming and related beamspace high resolution direction-of-arrival (DOA) estimation is studied in this paper. All beamspace processing methods are based on the beam outputs and the beampattern design plays an important role in providing high quality beam output data for further processing. Three typical situations which are frequently encountered in practical sonar system working environment and the most widely studied MUSIC algorithm are considered herein. First, when isotropic noise is the dominant noise at sensors, conventional beamforming techniques provide the optimum performance in the sense that DOA estimate is the ML estimate. Good DOA estimates are obtainable by applying MUSIC to the beam outputs directly. Then, uncorrelated interferes with much higher strength than the wanted signals are assumed to be present in the sidelobe region, and low sidelobe Dolph-Chebyshev and adaptive MVDR beampatterns are designed to guarantee the performance of MUSIC. And finally, the robustness of conventional techniques is combined with the adaptivity of MVDR beamforming to deal with the situation when the interfere in the sidelobe region is strongly correlated with one of the wanted sources. Performance in all three situations is studied with numerical examples.

To overcome the azimuth sampling constraints imposed in synthetic aperture sonar (SAS), many SAS systems employ a single transmitter and multiple-receiver configuration, which can be regarded as a system containing many bistatic transmit-receive pairs. In traditional reconstruction, the multiple receiver system data is often preprocessed into an equivalent single receiver (monostatic) data by using the phase center approximation (PCA) and along track interpolation, and then followed by standard image reconstruction algorithms. But a blurring will occur at the edge of the target area as the length of the receiver array increasing. In this paper, a novel approach is proposed to overcome the blurring problem caused by PCA based on the bistatic model. In this method, an image is firstly reconstructed with the data of each hydrophone independently, and then all the images are coherently added to give the high quality imagery. Simulation results show the feasibility and availability by applying this algorithm.