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step

System object: phased.STAPSMIBeamformer
Package: phased

Perform SMI STAP processing on input data

Syntax

Y = step(H,X,CUTIDX)
Y = step(H,X,CUTIDX,PRF)
Y = step(H,X,CUTIDX,ANG)
Y = step(H,X,CUTIDX,DOP)
[Y,W] = step(___)

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.

Y = step(H,X,CUTIDX) applies SMI processing to the input data, X. X must be a 3-dimensional M-by-N-by-P numeric array whose dimensions are (range, channels, pulses). The processing weights are calculated according to the range cell specified by CUTIDX. The targeting direction and the targeting Doppler are specified by Direction and Doppler properties, respectively. Y is a column vector of length M. This syntax is available when the DirectionSource property is 'Property' and the DopplerSource 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.

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

Y = step(H,X,CUTIDX,ANG) uses ANG as the targeting direction. This syntax is available when the DirectionSource property is 'Input port'. ANG must be a 2-by-1 vector in the form of [AzimuthAngle; ElevationAngle] (in degrees). The azimuth angle must be between –180 and 180. The elevation angle must be between –90 and 90.

Y = step(H,X,CUTIDX,DOP) uses DOP as the targeting Doppler frequency (in hertz). This syntax is available when the DopplerSource property is 'Input port'. DOP must be a scalar.

You can combine optional input arguments when their enabling properties are set: Y = step(H,X,CUTIDX,ANG,DOP)

[Y,W] = step(___) returns the additional output, W, as the processing weights. This syntax is available when the WeightsOutputPort property is true. W is a column vector of length N*P.

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.

Examples

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Process a data cube using an SMI beamformer. The weights are calculated for the 71st cell of a collected data cube pointing in the azimuth and elevation direction (45°,-35°) and with a Doppler of 12.980 kHz.

Load the cube data and create the SMI beamformer.

load STAPExampleData;
beamformer = phased.STAPSMIBeamformer('SensorArray',STAPEx_HArray, ...
    'PRF',STAPEx_PRF,'PropagationSpeed',STAPEx_PropagationSpeed, ...
    'OperatingFrequency',STAPEx_OperatingFrequency, ...
    'NumTrainingCells',100,'WeightsOutputPort',true, ...
    'DirectionSource','Input port','DopplerSource','Input port');
[y,w] = beamformer(STAPEx_ReceivePulse,71,[45;-35],12.980e3);

Plot the angle-doppler response.

response = phased.AngleDopplerResponse( ...
    'SensorArray',beamformer.SensorArray, ...
    'OperatingFrequency',beamformer.OperatingFrequency, ...
    'PRF',beamformer.PRF,'PropagationSpeed',beamformer.PropagationSpeed);
plotResponse(response,w)