This work generalizes the Fourier transform (FT)-based frequency-invariant beamforming (FIB) method to the synthesis of scanned frequency-invariant (FI) beam pattern with space-frequency notching for an array with non-isotropic elements. Wideband FI pattern characteristics are described by using multiple reference sub-band FI patterns. By applying fast Fourier transform (FFT) on the combination of these multiple reference sub-band FI patterns, a wideband excitation distribution can be generated. Based on this excitation distribution, we construct a new wideband excitation distribution that is conjugate-symmetric about zero frequency, so that real-valued finite-impulse-response (FIR) filter coefficients can be obtained by applying FFT on the constructed distribution. Two numerical examples are introduced to show the effectiveness and efficiency of the proposed method.

中文翻译：

---

扫描宽带变频不变波束方向图和空频陷波滤波器与阵列的高效合成

这项工作将基于傅立叶变换（FT）的频率不变波束形成（FIB）方法推广到具有非全同性元素阵列的具有空频陷波的扫描频率不变（FI）波束方向图的合成。通过使用多个参考子带FI模式来描述宽带FI模式特性。通过对这些多个参考子带FI模式的组合应用快速傅里叶变换（FFT），可以生成宽带激励分布。基于此激励分布，我们构造了一个关于零频率共轭对称的宽带激励分布，从而可以通过在构造的分布上应用FFT来获得实数值的有限冲激响应（FIR）滤波器系数。