Beamscan Spectrum

Beamscan spatial spectrum estimator

  • Library:
  • Phased Array System Toolbox / Direction of Arrival

Description

The Beamscan Spectrum block estimates the 2-D spatial spectrum of incoming narrowband signals by scanning a range of azimuth and elevation angles using a narrowband conventional beamformer. The block optionally calculates the direction of arrival of a specified number of signals by locating peaks of the spectrum.

Ports

Input

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Received signal, specified as an M-by-N complex-valued matrix. The quantity M is the length of the signal, the number of sample values contained in the signal. The quantity N is the number of sensor elements in the array.

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.

Data Types: double

Output

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2Magnitude of the estimated 2-D spatial spectrum, returned as a non-negative, returned as a real-valued P-by-Q matrix. Each entry represents the magnitude of the estimated MUSIC spatial spectrum. Each entry corresponds to an angle specified by the Azimuth scan angles (deg) and Elevation scan angles (deg) parameters. P equals the length of the vector specified in Azimuth scan angles (deg) and Q equals the length of the vector specified in Elevation scan angles (deg).

Data Types: double

Directions of arrival of the signals, returned as a real-valued 2-by-L matrix. L is the number of signals specified by the Number of signals parameter. The direction of arrival angle is defined by the azimuth and elevation angles of the source with respect to the array local coordinate system. The first row of the matrix contains the azimuth angles and the second row contains the elevation angles. If the object cannot identify peaks in the spectrum, it will return NaN. Angle units are in degrees.

Dependencies

To enable this output port, select the Enable DOA output check box.

Data Types: double

Parameters

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Signal propagation speed, specified as a real-valued positive scalar. The default value of the speed of light is the value returned by physconst('LightSpeed'). Units are in meters per second.

Example: 3e8

Data Types: double

System operating frequency, specified as a positive scalar. Units are in Hz.

The number of bits used to quantize the phase shift component of beamformer or steering vector weights. Specify the number of bits as a non-negative integer. A value of zero indicates that no quantization is performed.

Select this parameter to use forward-backward averaging to estimate the covariance matrix for sensor arrays with a conjugate symmetric array manifold structure.

Scan angles in azimuthal direction, specified as a real-valued vector. The angles must lie be between –180° and 180°, inclusive. You must specify the angles in ascending order. Units are in degrees.

Data Types: double

Scan angles in elevation direction, specified as a real-valued vector. The angles must lie be between –90° and 90°, inclusive. You must specify the angles in ascending order. Units are in degrees.

Data Types: double

Select this parameter to output the signals directions of arrival (DOA) through the Ang output port.

Specify the expected number of signals for DOA estimation as a positive scalar integer.

Dependencies

To enable this parameter, select the Enable DOA output check box.

Data Types: double

Block simulation, specified as Interpreted Execution or Code Generation. If you want your block to use the MATLAB® interpreter, choose Interpreted Execution. If you want your block to run as compiled code, choose Code Generation. Compiled code requires time to compile but usually runs faster.

Interpreted execution is useful when you are developing and tuning a model. The block runs the underlying System object™ in MATLAB. You can change and execute your model quickly. When you are satisfied with your results, you can then run the block using Code Generation. Long simulations run faster with generated code than in interpreted execution. You can run repeated executions without recompiling, but if you change any block parameters, then the block automatically recompiles before execution.

This table shows how the Simulate using parameter affects the overall simulation behavior.

When the Simulink® model is in Accelerator mode, the block mode specified using Simulate using overrides the simulation mode.

Acceleration Modes

Block SimulationSimulation Behavior
NormalAcceleratorRapid Accelerator
Interpreted ExecutionThe block executes using the MATLAB interpreter.The block executes using the MATLAB interpreter.Creates a standalone executable from the model.
Code GenerationThe block is compiled.All blocks in the model are compiled.

For more information, see Choosing a Simulation Mode (Simulink).

Sensor Array Tab

Method to specify array, specified as Array (no subarrays) or MATLAB expression.

  • Array (no subarrays) — use the block parameters to specify the array.

  • MATLAB expression — create the array using a MATLAB expression.

MATLAB expression used to create an array, specified as a valid Phased Array System Toolbox array System object.

Example: phased.URA('Size',[5,3])

Dependencies

To enable this parameter, set Specify sensor array as to MATLAB expression.

Array Parameters

Array geometry, specified as one of

  • ULA — Uniform linear array

  • URA — Uniform rectangular array

  • UCA — Uniform circular array

  • Conformal Array — arbitrary element positions

The number of array elements for ULA or UCA arrays, specified as an integer greater than or equal to 2.

Dependencies

To enable this parameter, set Geometry to ULA or UCA.

Spacing between adjacent array elements:

  • ULA — specify the spacing between two adjacent elements in the array as a positive scalar.

  • URA — specify the spacing as a positive scalar or a 1-by-2 vector of positive values. If Element spacing (m) is a scalar, the row and column spacings are equal. If Element spacing (m) is a vector, the vector has the form [SpacingBetweenArrayRows,SpacingBetweenArrayColumns].

Dependencies

To enable this parameter, set Geometry to ULA or URA.

Linear axis direction of ULA, specified as y, x, or z. All ULA array elements are uniformly spaced along this axis in the local array coordinate system.

Dependencies

  • To enable this parameter, set Geometry to ULA.

  • This parameter is also enabled when the block only supports ULA arrays.

Dimensions of a URA array, specified as a positive integer or 1-by-2 vector of positive integers.

  • If Array size is a 1-by-2 vector, the vector has the form [NumberOfArrayRows,NumberOfArrayColumns].

  • If Array size is an integer, the array has the same number of elements in each row and column.

For a URA, array elements are indexed from top to bottom along the leftmost array column, and continued to the next columns from left to right. In this figure, the Array size value of [3,2] creates an array having three rows and two columns.

Dependencies

To enable this parameter, set Geometry to URA.

Lattice of URA element positions, specified as Rectangular or Triangular.

  • Rectangular — Aligns all the elements in row and column directions.

  • Triangular — Shifts the even-row elements of a rectangular lattice toward the positive row-axis direction. The displacement is one-half the element spacing along the row dimension.

Dependencies

To enable this parameter, set Geometry to URA.

Array normal direction, specified as x, y, or z.

Elements of planar arrays lie in a plane orthogonal to the selected array normal direction. Element boresight directions point along the array normal direction.

Array Normal Parameter ValueElement Positions and Boresight Directions
xArray elements lie in the yz-plane. All element boresight vectors point along the x-axis.
yArray elements lie in the zx-plane. All element boresight vectors point along the y-axis.
zArray elements lie in the xy-plane. All element boresight vectors point along the z-axis.

Dependencies

To enable this parameter, set Geometry to URA or UCA.

Radius of UCA array, specified as a positive scalar.

Dependencies

To enable this parameter, set Geometry to UCA.

Positions of the elements in a conformal array, specified as a 3-by-N matrix of real values, where N is the number of elements in the conformal array. Each column of this matrix represents the position [x;y;z]of an array element in the array local coordinate system. The origin of the local coordinate system is (0,0,0). Units are in meters.

Dependencies

To enable this parameter set Geometry to Conformal Array.

Data Types: double

Direction of element normal vectors in a conformal array, specified as a 2-by-1 column vector or a 2-by-N matrix. N indicates the number of elements in the array. If the parameter value is a matrix, each column specifies the normal direction of the corresponding element in the form [azimuth;elevation] with respect to the local coordinate system. The local coordinate system aligns the positive x-axis with the direction normal to the conformal array. If the parameter value is a 2-by-1 column vector, the same pointing direction is used for all array elements.

You can use the Element positions (m) and Element normals (deg) parameters to represent any arrangement in which pairs of elements differ by certain transformations. The transformations can combine translation, azimuth rotation, and elevation rotation. However, you cannot use transformations that require rotation about the normal direction.

To enable this parameter, set Geometry to Conformal Array.

Data Types: double

Specify element tapering as a complex-valued scalar or a complex-valued 1-by-N row vector. In this vector, N represents the number of elements in the array.

Also known as element weights, tapers multiply the array element responses. Tapers modify both amplitude and phase of the response to reduce side lobes or steer the main response axis.

If Taper is a scalar, the same weight is applied to each element. If Taper is a vector, a weight from the vector is applied to the corresponding sensor element. The number of weights must match the number of elements of the array.

Data Types: double

Introduced in R2014b