Benefits of Adaptive Beamforming

Narrowband Phase Shift Beamformer for a ULAuses weights chosen independent of any data received by the array. The weights in the narrowband phase shift beamformer steer the array response in a specified direction. However, they do not account for any interference scenarios. As a result, these conventional beamformers are susceptible to interference signals. Such interference signals can be a particular problem if they occur at sidelobes of the array response.

By contrast, adaptive, or statistically optimum, beamformers can account for interference signals. Anadaptive beamformer算法基于所接收数据的统计信息选择权重。例如，自适应波束形成器可以通过使用接收的数据来改善SNR以在阵列响应中放置空值。这些空在与干扰信号对应的角度放置。

金宝app支持自适应波束成形

相控阵系统工具箱™ software provides these adaptive beamformers:

Nulling with LCMV Beamformer

This example shows how to use an LCMV beamformer to point a null of the array response in the direction of an interfering source. The array is a 10-element uniform linear array (ULA). By default, the ULA elements are isotropic antennas created by thephased.IsotropicAntennaElementSystem Object™。设置天线元件的频率范围，使载波频率位于操作范围内。载波频率为1 GHz。

fc = 1e9; lambda = physconst('LightSpeed'/ fc;数组= phased.ula（'NumElements',10,'ElementsPacing',lambda/2); array.Element.FrequencyRange = [8e8 1.2e9];

使用简单的矩形脉冲模拟测试信号。

t = linspace(0,0.3,300)'; testsig = zeros(size(t)); testsig(201:205) = 1;

Assume the rectangular pulse is incident on the ULA from an angle of 30° azimuth and 0° elevation. Use theControllanewave.function of the ULA System object to simulate reception of the pulse waveform from the incident angle.

angle_of_arrival = [30;0]; x = collectPlaneWave(array,testsig,angle_of_arrival,fc);

信号x是一个有十列的矩阵。每个列表示其中一个数组元素处的接收信号。

构造传统的相移波束形成器。设定WeightsOutputPortproperty to真的输出空间滤波器权重。

convbeamformer = phased.phaseshiftBeamFormer（'SensorArray'，大批，。。。'工作频率'1 e9'Direction',angle_of_arrival,。。。'WeightsOutputPort'，真的）;

Add complex-valued white Gaussian noise to the signalx。设置可重复结果的默认随机数流。

rng.defaultnpower = 0.5; x = x + sqrt(npower/2)*(randn(size(x)) + 1i*randn(size(x)));

创建一个10W干扰源。指定磁阻干扰器以具有10W的有效辐射功率。来自拦截干扰器的干扰信号从120°方位角和0°高度的角度入射在ULA上。使用Controllanewave.function of the ULA System object to simulate reception of the jammer signal.

jamsig = sqrt（10）* randn（300,1）;jammer_angle = [120; 0];jamsig = colorplanewave（阵列，jamsig，jammer_angle，fc）;

Add complex-valued white Gaussian noise to simulate noise contributions not directly associated with the jamming signal. Again, set the default random number stream for reproducible results. This noise power is 0 dB below the jammer power. Beamform the signal using a conventional beamformer.

noisepwr = 1e-5;RNG（2008）;噪声= sqrt（noisepwr / 2）*。。。（randn（尺寸（jamsig））+ 1j * randn（尺寸（jamsig）））;jamsig = jamsig +噪音;rxsig = x + jamsig;[yout，w] = convbeamformer（rxsig）;

Implement the adaptive LCMV beamformer using the same ULA array. Use the target-free data,jamsig, as training data. Output the beamformed signal and the beamformer weights.

steeringvector = phased.SteeringVector('SensorArray'，大批，。。。'繁殖',physconst('LightSpeed')); LCMVbeamformer = phased.LCMVBeamformer('所诊断'，1，。。。'TrainingInputPort',true,'WeightsOutputPort'，真的）;lcmvbeamformer.constraint = steeringvector（fc，distl_of_arrival）;lcmvbeamformer.desiredresponse = 1;[ylcmv，wlcmv] = lcmvbeamformer（rxsig，jamsig）;

Plot the conventional beamformer output and the adaptive beamformer output.

子图（211）绘图（t，abs（yout））轴紧的title('传统的波束形成器'）ylabel（'Magnitude'）子图（212）绘图（t，abs（ylcmv））轴紧的title('LCMV（自适应）波束形成器'）Xlabel（'Seconds'）ylabel（'Magnitude')

自适应波束形成器显着改善了0.2秒的矩形脉冲的SNR。

使用常规和LCMV重量，绘制每个波束形成器的响应。

子图（211）模式（阵列，Fc，[ -  180：180]，0，'繁殖',physconst('LightSpeed'),。。。'CoordinateSystem','rectangular','Type','powerdb','Normalize',true,。。。“重量”，w）标题（'Array Response with Conventional Beamforming Weights'）;子图（212）模式（阵列，Fc，[ -  180：180]，0，'繁殖',physconst('LightSpeed'),。。。)'CoordinateSystem','rectangular','Type','powerdb','Normalize',true,。。。“重量”,wLCMV) title('Array Response with LCMV Beamforming Weights'）;

自适应beamform places a null at the arrival angle of the interference signal, 120°.