First-order differential microphone arrays (FODMAs), which combine a small-spacing uniform linear array and a first-order differential beamformer, have been used in a wide range of applications for sound and speech signal acquisition. However, traditional FODMAs are not steerable and their main lobe can only be at the endfire directions. To circumvent this problem, we propose in this letter a new method to design steerable FODMAs. We first divide the target beampattern into a sum of two sub-beampatterns, i.e., cardioid and dipole, where the summation is controlled by the steering angle. We then design two sub-beamformers, one is similar to the traditional approach and is used to achieve the cardioid sub-beampattern, while the other is designed to filter the squared observation signals and is used to approximate the dipole sub-beampattern. The overall beampattern resembles the target beampattern for any steering angle. Simulations and experiments are performed to justify the effectiveness of the developed method.

中文翻译：

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设计可控一阶差分波束形成器的新方法

一阶差分麦克风阵列（FODMA）结合了小间距均匀线性阵列和一阶差分波束形成器，已广泛用于声音和语音信号采集。但是，传统的FODMA不可操纵，其主瓣只能朝着终射方向。为了避免这个问题，我们在这封信中提出了一种设计可控FODMA的新方法。我们首先将目标波束模式划分为两个子波束的总和，即心形和偶极子，它们的总和由转向角控制。然后，我们设计了两个子波束形成器，一个类似于传统方法，用于实现心形子beampattern，而另一个用于过滤平方的观测信号并用于近似偶极子beampattern。对于任何转向角，整个波束图都类似于目标波束图。进行仿真和实验以证明所开发方法的有效性。