How to provide independent inputs to elements of a phased array transmitter?

I am trying to analyze the phased array antenna described in "Novel Compact Steerable Antenna with Radar Applications" by Galejs and Fenn in IEEE Xplore, 2015, pp 1536-1540. That paper describes an antenna with three dipoles and three loops (six elements in total), all pointing in different directions, and each with its own phase and amplitude (weight) that are explicitly provided functions of the desired steering angle. I want to apply each computed input to its own antenna element, and analyze the result (e.g., the gain pattern as a function of steering angle). I do NOT want simply to accept a pre-fab beamformer. The paper provides that, and I want to test it. I think I see how to construct a phased.HeterogeneousConformalArray ; however, I haven't yet found how to provide each of the six elements its own feed. Thanks for any help you can provide.

Answer 1

[Umar]

Hi @Richard,

After going through documentation provided at the link below

https://www.mathworks.com/help/phased/ref/phased.heterogeneousconformalarray-system-object.html

It seems that it is designed for constructing arrays with different types of sensor elements in arbitrary positions and orientations. So, the key properties you will utilize include:

ElementSet: cell array containing your specific antenna elements.

ElementIndices: A vector that maps the elements in your array to their respective indices in the ElementSet.

ElementPosition: A matrix defining the spatial coordinates of each element.

ElementNormal: Defines the direction each element is pointing.

Taper: Allows you to set individual weights (both amplitude and phase) for each element.

Please see steps below to implement your analysis.

Define Your Elements: Create instances of your dipole and loop antennas using MATLAB’s Antenna Toolbox.

    dipole = phased.IsotropicAntennaElement;
    loop = phased.IsotropicAntennaElement; % Replace with actual loop 
    definition

Set Up the Heterogeneous Conformal Array: Define your array using the properties outlined above:

    % Create an array with 6 elements
    H = phased.HeterogeneousConformalArray(...
        'ElementSet', {dipole, loop, dipole, loop, dipole, loop}, ...
        'ElementIndices', [1, 2, 1, 2, 1, 2], ...
        'ElementPosition', [x_positions; y_positions; z_positions], ...
        'ElementNormal', [azimuth_angles; elevation_angles]);

Here, x_positions, y_positions, z_positions, azimuth_angles, and elevation_angles need to be defined based on your specific configuration.

Assign Weights: You can specify unique tapers for each element by defining a vector:

    weights = [weight1, weight2, weight3, weight4, weight5, weight6]; % Define 
    weights based on your steering angles
    H.Taper = weights;

Compute Response: Use the step method or call the object directly to compute the response for specified angles:

    steeringAngles = [desired_azimuth; desired_elevation]; % Define desired 
    angles
    response = H(steeringAngles);

Analyze Gain Pattern: To analyze the gain pattern as a function of steering angle, use:

    fc = frequency; % Define operating frequency
    pattern(H, fc, azimuth_range, elevation_range);

Replace azimuth_range and elevation_range with vectors specifying the range of angles you wish to analyze.

When analyzing an array of multiple elements, consider mutual coupling effects which may alter the expected gain patterns. You can compute embedded patterns if necessary using termination settings. Also, MATLAB provides various visualization tools such as patternAzimuth and patternElevation which can help in assessing how well your steering works across different angles.

Hope this helps.

[Richard]

Wow! Thank you for the terrific answer. You answered my question when you informed me that tapers are used to assign weights. When I see the word "taper", I think of the shape of a candle; it did not occur to me that it applied to signal weights. You went well beyond my question and outlined how I can use the toolbox to do more analysis. Thanks!

[Umar]

Hi @Richard,

Thank you for your kind words regarding my response. I am pleased to hear that the information about tapers and their application in assigning weights was helpful to you. It is always my goal to provide clarity and additional insights, so I'm glad that the explanation exceeded your expectations and offered guidance for further analysis with the toolbox. If you have any more questions or need further assistance, please do not hesitate to reach out. Thank you once again for your feedback!