Beamscan Spectrum
Beamscan spatial spectrum estimator
Libraries:
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
X — Received signal
M-by-N complex-valued matrix
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
Y — Beamscan 2-D spatial spectrum
non-negative real-valued P-by-Q
matrix
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
Ang — Directions of arrival
non-negative, real-valued 2-by-L matrix
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
Signal propagation speed (m/s) — Signal propagation speed
physconst('LightSpeed')
(default) | real-valued positive scalar
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
Operating frequency (Hz) — System operating frequency
3e8
(default) | positive real scalar
System operating frequency, specified as a positive scalar. Units are in Hz.
Number of bits in phase shifters — Number of phase shift quantization bits
0
(default) | nonnegative integer
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.
Forward-backward averaging — Enable forward-backward averaging
off (default) | on
Select this parameter to use forward-backward averaging to estimate the covariance matrix for sensor arrays with a conjugate symmetric array manifold structure.
Azimuth scan angles (deg) — Scan angles in azimuth direction
-180:180
(default) | real-valued vector
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
Elevation scan angles (deg) — Scan angles in elevation direction
-90:90
(default) | real-valued vector
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
Enable DOA output — Output directions of arrival through output port
off (default) | on
Select this parameter to output the signals directions of arrival (DOA) through the Ang output port.
Number of signals — Expected number of arriving signals
1
(default) | positive integer
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
Simulate using — Block simulation method
Interpreted Execution
(default) | Code Generation
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 Simulation | Simulation Behavior | ||
Normal | Accelerator | Rapid Accelerator | |
Interpreted Execution | The block executes using the MATLAB interpreter. | The block executes using the MATLAB interpreter. | Creates a standalone executable from the model. |
Code Generation | The block is compiled. | All blocks in the model are compiled. |
For more information, see Choosing a Simulation Mode (Simulink).
Programmatic Use
Block
Parameter:SimulateUsing |
Type:enum |
Values:Interpreted
Execution , Code Generation |
Default:Interpreted
Execution |
Specify sensor array as — Method to specify array
Array (no subarrays)
(default) | MATLAB expression
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.
Expression — MATLAB expression used to create an array
Phased Array System Toolbox™ array System object
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
.
Geometry — Array geometry
ULA
(default) | URA
| UCA
| Conformal Array
Array geometry, specified as one of
ULA
— Uniform linear arrayURA
— Uniform rectangular arrayUCA
— Uniform circular arrayConformal Array
— arbitrary element positions
Number of elements — Number of array elements
2
for ULA arrays and 5
for UCA
arrays (default) | integer greater than or equal to 2
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
.
Element spacing (m) — Spacing between array elements
0.5
for ULA arrays and [0.5,0.5]
for URA arrays (default) | positive scalar for ULA or URA arrays | 2-element vector of positive values for URA arrays
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
.
Array axis — Linear axis direction of ULA
y
(default) | x
| z
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.
Array size — Dimensions of URA array
[2,2]
(default) | positive integer | 1-by-2 vector of positive integers
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
.
Element lattice — Lattice of URA element positions
Rectangular
(default) | Triangular
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 — Array normal direction
x
for URA arrays or
z
for UCA
arrays (default) | y
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 Value | Element Positions and Boresight Directions |
---|---|
x | Array elements lie in the yz-plane. All element boresight vectors point along the x-axis. |
y | Array elements lie in the zx-plane. All element boresight vectors point along the y-axis. |
z | Array 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 (m) — UCA array radius
0.5 (default) | positive scalar
Radius of UCA array, specified as a positive scalar.
Dependencies
To enable this parameter, set Geometry to
UCA
.
Element positions (m) — Positions of conformal array elements
[0;0;0]
(default) | 3-by-Nmatrix of real values
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
Element normals (deg) — Direction of conformal array element normal vectors
[0;0]
| 2-by-1 column vector | 2-by-N matrix
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
Taper — Array element tapers
1 (default) | complex scalar | complex-valued row vector
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
Version History
Introduced in R2014b
See Also
phased.BeamscanEstimator2D
| phased.ConformalArray
| phased.UCA
| phased.ULA
| phased.URA
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