step

System object: phased.AngleDopplerResponse
Namespace: phased

Calculate angle-Doppler response

Syntax

[RESP,ANG_GRID,DOP_GRID] = step(H,X)
[RESP,ANG_GRID,DOP_GRID] = step(H,X,ELANG)
RESP,ANG_GRID,DOP_GRID = step(H,X,PRF)


Description

Note

Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

[RESP,ANG_GRID,DOP_GRID] = step(H,X) calculates the angle-Doppler response of the data X. RESP is the complex angle-Doppler response. ANG_GRID and DOP_GRID provide the angle samples and Doppler samples, respectively, at which the angle-Doppler response is evaluated. This syntax is available when the ElevationAngleSource property is 'Property'.

The size of the first dimension of the input matrix can vary to simulate a changing signal length. A size change can occur, for example, in the case of a pulse waveform with variable pulse repetition frequency.

[RESP,ANG_GRID,DOP_GRID] = step(H,X,ELANG) calculates the angle-Doppler response using the specified elevation angle ELANG. This syntax is available when the ElevationAngleSource property is 'Input port'.

RESP,ANG_GRID,DOP_GRID = step(H,X,PRF) uses PRF as the pulse repetition frequency. This syntax is available when the PRFSource property is 'Input port'.

Note

The object performs an initialization the first time the object is executed. This initialization locks nontunable properties and input specifications, such as dimensions, complexity, and data type of the input data. If you change a nontunable property or an input specification, the System object issues an error. To change nontunable properties or inputs, you must first call the release method to unlock the object.

Input Arguments

H	Angle-Doppler response object.
X	Input data as a matrix or column vector. If X is a matrix, the number of rows in the matrix must equal the number of elements of the array specified in the SensorArray property of H. If X is a vector, the number of rows must be an integer multiple of the number of elements of the array specified in the SensorArray property of H. In addition, the multiple must be at least 2.
ELANG	Elevation angle in degrees. You can specify this argument as single or double precision. Default: Value of Elevation property of H
PRF	Pulse repetition frequency specified as a positive scalar. To enable this argument, set the PRFSource property to 'Input port'. Units are in Hertz. You can specify this argument as single or double precision.

Output Arguments

RESP	Complex angle-Doppler response of X. RESP is a P-by-Q matrix. P is determined by the NumDopplerSamples property of H and Q is determined by the NumAngleSamples property.
ANG_GRID	Angle samples at which the angle-Doppler response is evaluated. ANG_GRID is a column vector of length Q.
DOP_GRID	Doppler samples at which the angle-Doppler response is evaluated. DOP_GRID is a column vector of length P.

Examples

Calculate Angle-Doppler Response

Calculate the angle-Doppler response of the 190th cell of a collected data cube.

Load data cube and construct a phased.AngleDopplerResponse System object™.

load STAPExampleData;
x = shiftdim(STAPEx_ReceivePulse(190,:,:));
response = phased.AngleDopplerResponse(...
    'SensorArray',STAPEx_HArray,...
    'OperatingFrequency',STAPEx_OperatingFrequency,...
    'PropagationSpeed',STAPEx_PropagationSpeed,...
    'PRF',STAPEx_PRF);

Plot angle-Doppler response.

[resp,ang_grid,dop_grid] = response(x);
contour(ang_grid,dop_grid,abs(resp))
xlabel('Angle')
ylabel('Doppler')

Algorithms

phased.AngleDopplerResponse generates the response using a conventional beamformer and an FFT-based Doppler filter. For further details, see [1].

References

[1] Guerci, J. R. Space-Time Adaptive Processing for Radar. Boston: Artech House, 2003.