MATLAB: Plotting the beamwidth from a matrix

antenna patternbeamwidhplot

Hi everyone, i have this given matrix (Elevation, azimuth & gain) in the attachment. How can i plot the 3db-beamwidth of this antenna pattern ? I just want to see the pattern and want to calculate the 3db-beamwidth. Thank you so much.

Best Answer

Another way to compute the beamwidth is to plot the azimuth and Gain :

 Data=load('data_ABS_antenna_CASMA.mat');
X=Data.ABS_antenna_gain;
Gain=X(:,3);
Azimuth=X(:,2);
[index,c]=find(Gain>=max(Gain)-3);
figure; plot(Azimuth(index),Gain(index),'*')
figure; plot(Azimuth,Gain,'*')

The beamwidth is 20° .

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MATLAB: Subarray Simulation have different output by using similar method

Conceptually the two approach is equivalent. The discrepancy you see is related to how you generate the custom antenna in your second approach. When you use the result from pattern, you essentially get only the magnitude data. However, even though the elements are isotropic, the response of an array has phase information in there. Therefore, instead of using

[embpattern, az, el] = pattern(subarray,fc);
ant_sub = phased.CustomAntennaElement('FrequencyVector',[10e9,50e9],...
    'AzimuthAngles',az,...
    'ElevationAngles',el,...
    'MagnitudePattern',embpattern,...
    'PhasePattern',zeros(size(embpattern)));

I would use the following code to generate the custom antenna element

az = -180:180;
el = -90:90;
embpattern = complex(zeros(numel(el),numel(az)));
subarrayresp = phased.ArrayResponse('SensorArray',subarray);
for m = 1:numel(el)
    embpattern(m,:) = subarrayresp(fc,[az;el(m)*ones(size(az))]);
end
ant_sub = phased.CustomAntennaElement('FrequencyVector',[10e9,50e9],...
    'AzimuthAngles',az,...
    'ElevationAngles',el,...
    'MagnitudePattern',mag2db(abs(embpattern)),...
    'PhasePattern',angle(embpattern));

If you use this ant_sub in your program, you will see that the two approach give the same power level.

HTH

MATLAB: Directivity did not match our expectation

Hi Ralph,

In this example you are using an isotropic antenna element. So even though in this cut the beam is more focused, it has strong lobe all around the array axis, so in some sense the energy is not well focused.

If we change the element type to a more realistic pattern, such as cosine antenna pattern, then you can see the directivity of the ULA starts to be better than the URA

figure
ha = phased.ULA('NumElements',16,'Element',phased.CosineAntennaElement);
plotResponse(ha,3e8,3e8,'RespCut','Az','Format','Polar','Unit','dbi');
hold on;
ha = phased.URA('Size',[4 4],'Element',phased.CosineAntennaElement);
plotResponse(ha,3e8,3e8,'RespCut','Az','Format','Polar','Unit','dbi');

If you use a Hertzian dipole, the ULA is also better

figure
ha = phased.ULA('NumElements',16,'Element',phased.ShortDipoleAntennaElement);
plotResponse(ha,3e8,3e8,'RespCut','Az','Format','Polar','Unit','dbi');
hold on;
ha = phased.URA('Size',[4 4],'Element',phased.ShortDipoleAntennaElement);
plotResponse(ha,3e8,3e8,'RespCut','Az','Format','Polar','Unit','dbi');

In short, I'm not saying that you are wrong since I don't really have a theoretical result to back me up. But I'm also not convinced that the toolbox is giving the wrong answer. If you do have a number that I can compare to, please let me know and I'd love to take a look.

Thanks

Best Answer

Related Solutions

MATLAB: Subarray Simulation have different output by using similar method

MATLAB: Directivity did not match our expectation

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