www.gusucode.com > phased 案例源码 matlab代码程序 > phased/CreateGratingLobeDiagramForUndersampledURAExample.m
%% Create Grating Lobe Diagram for Undersampled Microphone URA % Plot the grating lobe diagram for an 11-by-9-element uniform % rectangular array having element spacing greater than one-half % wavelength. Grating lobes are plotted in u-v coordinates. % % Assume the operating frequency of the array is 10 kHz and the % spacing between elements is 0.75 of a wavelength. All elements % are omnidirectional microphone elements. Steer the array in % the direction 20 degrees in azimuth and 30 degrees in elevation. % The speed of sound in air is 344.21 m/s at 21 deg C. % Copyright 2015 The MathWorks, Inc. cair = 344.21; f = 10000; lambda = cair/f; sMic = phased.OmnidirectionalMicrophoneElement(... 'FrequencyRange',[20 20000]); sURA = phased.URA('Element',sMic,'Size',[11,9],... 'ElementSpacing',0.75*lambda*[1,1]); plotGratingLobeDiagram(sURA,f,[20;30],cair); %% % The main lobe of the array is indicated by a filled black circle. % The grating lobes in visible and nonvisible regions % are indicated by unfilled black circles. The visible region is the % region in u-v coordinates for which $u^2 + v^2 \le 1$. The visible region is shown % as a unit circle centered at the origin. Because the array % spacing is greater than one-half wavelength, there are grating % lobes in the visible region of space. There are an infinite % number of grating lobes in the nonvisible regions, but only % those in the range [-3,3] 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. Because the mainlobe is outside the green area, there is a % grating lobe within the visible region.