www.gusucode.com > phased 案例源码 matlab代码程序 > phased/ULAGratingLobeDiagram3Example.m
%% Create Grating Lobe Diagram for ULA With Different Phase-Shifter Frequency % Plot the grating lobe diagram for a 4-element uniform % linear array having element spacing greater than one-half % wavelength. Apply a phase-shifter frequency that differs from % the signal frequency. Grating lobes are % plotted in u-v coordinates. % % Assume the signal frequency is 3 GHz and the % spacing between elements is 0.65 $\lambda$. All elements are % isotropic antenna elements. The phase-shifter frequency is set to % 3.5 GHz. Steer the array in the direction $45^{\circ}$ % azimuth, $0^{\circ}$ elevation. % Copyright 2015 The MathWorks, Inc. c = physconst('LightSpeed'); f = 3e9; f0 = 3.5e9; lambda = c/f; sIso = phased.IsotropicAntennaElement; sULA = phased.ULA('Element',sIso,'NumElements',4,... 'ElementSpacing',0.65*lambda ); plotGratingLobeDiagram(sULA,f,[45;0],c,f0); %% % As a result of adding the shifted frequency, the mainlobe % shifts right towards larger $u$ values. The beam no % longer points toward the actual source arrival angle. % % The mainlobe of the array is indicated by a filled black % circle. The grating lobes in the visible and nonvisible regions are % indicated by empty black circles. The visible region, marked by the two % black vertical lines, corresponds to arrival % angles between $\mbox{-90}^{\circ}$ and $\mbox{90}^{\circ}$. The % visible region is defined by the direction % cosine limits $-1 \le u \le 1$. Because the array spacing is greater than % one-half wavelength, there is now a grating % lobe in the visible region of space. There are an infinite % number of grating lobes in the nonvisible regions, but only those % for which $-3 \le u \le 3$ are shown. % % The grating-lobe free region, shown in green, is the range of % directions of the main lobe for which there are no grating % lobes in the visible region. In this case, it lies inside % the visible region.