GSC Beamformer
Generalized side lobe suppressor.
blockType: GSCBeamformer
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Path in the library: |
Description
Block GSC Beamformer implements a generalized side lobe suppressor (generalized sidelobe cancellation, GSC). The GSC beamformer unit separates the array of incoming signals and sends them through the conventional path of the ray shaper and the path with side lobe suppression. The algorithm first pre-adjusts the array to the direction of beamforming, and then adaptively selects the filter weights to minimize the output power of the side lobe suppression path. The algorithm uses the least mean squares (LMS) method to calculate adaptive weights. The final signal generated by the beam is the difference between the outputs of the two paths.
Ports
Entrance
X — input signal
complex matrix M by N
The input signal, specified as a matrix on , where — the number of signal samples, and — the number of array elements.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Support for complex numbers: Yes
Ang — directions of formation of the output signal
a 2-by-1 real vector
The radiation directions of the signals are specified as a 2-by-1 real matrix in the form of [AzimuthAngle;ElevationAngle]. The azimuth angle must be in the range from -180° to 180° inclusive. The elevation angle must be in the range from -90° to 90° inclusive. The angles are set relative to the local coordinate system of the array.
Dependencies
To use this port, set the Source of beamforming direction parameter to Input port.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Output
Y is the output signal generated by the pass beam:q[<br>] complex vector M by 1
The output signal returned as a complex vector on 1, where — the number of signal samples.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Support for complex numbers: Yes
Parameters
Main
Signal propagation speed (m/s) — signal propagation speed, m/s
3e8 (default) | positive scalar
The propagation velocity of the signal in the form of a real positive scalar. The default value for the speed of light is `3e8 m/s'.
The units of measurement are meters per second.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Inherit sample rate — inheriting the sampling rate from higher-level pass:q blocks[<br>] enabled (by default) | disabled
Select this option to inherit the sampling rate from the higher blocks. Otherwise, specify the sampling rate using the Sample rate (Hz) parameter.
Data types: Bool
Sample rate (Hz) — sampling rate of the pass signal:q[<br>] 1e6 (default) | positive scalar
The sampling frequency of the signal, set as a positive scalar. The units of measurement are hertz.
Dependencies
To use this option, uncheck the Inherit sample rate checkbox.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Signal path FIR filter length — the order of the FIR filter on the path of the pass signal:q[<br>] 1 (default) | positive integer
The order of the FIR filter on the signal path, set as a positive integer. The FIR filter is a delta function.
Adaptive filter step size — the step size coefficient of the adaptive LMS filter
0.1 (default) | positive scalar
The step size coefficient of the adaptive filter, set as a positive scalar. This value, divided by the total power in the side lobe suppression path, determines the actual step size of the adaptive filter used by the LMS algorithm.
Beamforming direction (deg) — directions of ray formation
[0; 0] (default) | a 2-by-1 real matrix
The directions of ray formation, defined as a 2-by-1 real matrix, where each column has the form [AzimuthAngle;ElevationAngle]. The angle measurement units are degrees. The azimuthal angle should be in the range of −180° to 180°. The elevation angle should be in the range of −90° to 90°. The angles are set relative to the local coordinate system of the array.
Dependencies
To use this parameter, set the Source of beamforming direction parameter to Property.
Source of beamforming direction — source of the beamforming direction
Property (default) | Input port
The source of the beam formation direction is set as Property or `Input port'.
-
Property— the direction is set using the Beamforming direction (deg) parameter. -
`Input port' — the direction is determined by the input to the Ang port.
Sensor Array
Specify sensor array as — method for setting the pass array:q[<br>] Array (no subarrays) (default)
Array assignment method, available values:
-
Array (no subarrays)
Element
Element type — types of antenna array elements
Isotropic Antenna (default) | Cardioid Antenna | Cosine Antenna | Custom Antenna | Gaussian Antenna | Sinc Antenna | Omni Microphone | Custom Microphone
The type of antenna array element.
Available values:
-
Isotropic Antenna -
Cardioid Antenna -
Cosine Antenna -
Custom Antenna -
Gaussian Antenna -
Sinc Antenna -
Omni Microphone -
Custom Microphone
Operating frequency range (Hz) — operating frequency range of the pass antenna array element:q[<br>] [0,1e20] (default) | a real vector is a 1 by 2 row
The range of operating frequencies of the antenna array element in the form of a vector row 1 by 2 in the form of [LowerBound,UpperBound]. The element has no response outside this frequency range. The units of frequency measurement are Hz.
Dependencies
To use this parameter, set the Element type parameter to Isotropic Antenna, Cosine Antenna, or 'Omni Microphone'.
Baffle the back of the element — accounting for radiation through the rear beam of the radiation pattern into the rear hemisphere of the Isotropic Antenna element or Omni Microphone'
`disabled (by default) | enabled
`disabled (by default)
Set this flag to exclude radiation into the rear hemisphere. The response from the rear hemisphere at all azimuth angles outside the ±90° range from the wide side is set to zero. The wide-angle direction is defined as the azimuth angle of 0° and the elevation angle of 0°.
Dependencies
To use this parameter, set the Element type parameter to Isotropic Antenna or `Omni Microphone'.
Null axis direction — the direction of the axis along the zero radiation.
-x (default) | +x | +y | -y | +z | -z
The direction of the axis is along the zero radiation.
Dependencies
To use this parameter, set the Element type parameter to Cardioid Antenna.
Exponent of cosine pattern — exponent exponent when defining the shape of a cosine radiation pattern
[1.5, 1.5] (default) | non-negative scalar | a real matrix of non-negative values of 1 by 2
The exponent of the exponent of the cosine model in the form of a non-negative scalar or a 1 by 2 real matrix of non-negative values. If the Exponent of cosine pattern is a 1 by 2 vector, then the first element is the exponent in the direction of the azimuth, and the second is in the direction of the angle of the place. With a scalar value of this parameter, the cosines in the azimuthal and elevation directions are raised to one power.
Dependencies
To use this parameter, set the Element type parameter to Cosine Antenna.
Operating frequency vector (Hz) — array of operating frequencies of the antenna array element
[0,1e20] (default) | real vector is a string
An array of operating frequencies of an antenna array element in the form of a row vector 1 on increasing actual values. The element has no response beyond the frequency range specified by the minimum and maximum elements of this vector. The units of frequency measurement are Hz.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna or `Custom Microphone'. To set the responses at these frequencies, use the Frequency responses (dB) parameter.
Frequency responses (dB) — frequency responses of the antenna array element
[0,0] (default)| real vector string
The frequency response of the user elements of the antenna arrays is determined by the parameter Operating frequency vector (Hz). The dimensions of the Frequency responses (dB) vector must match the dimensions of the vector specified by the Operating frequency vector (Hz) parameter.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna or `Custom Microphone'.
Input Pattern Coordinate System — selection of the coordinate system of the radiation pattern of the user antenna
az-el (default) | phi-theta
The choice of the coordinate system of the radiation pattern of the user antenna is indicated by az-el or phi-theta'. When selecting `az-el, the Azimuth angles (deg) and Elevations angles (deg) parameters are used to set the coordinates of the directional pattern points. When specifying the phi-theta parameter, the Phi angle (deg) and Theta angles (deg) parameters are used to set the coordinates of the part points.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna.
Azimuth angles (deg) — azimuth angles of the antenna radiation pattern
[-180:180] (default) | real vector is a string
The values of the azimuth angles, which will be used to calculate the antenna pattern in the form of a vector row 1 on . it must be more than 2. The azimuth angles should be in the range of −180° up to 180° inclusive and arranged in strictly ascending order.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna and the Input Pattern Coordinate System parameter to az-el.
Elevation angles (deg) — values of the angles of the antenna pattern position
[-90:90] (default) | real vector is a string
The values of the angles of the location at which it is necessary to calculate the radiation pattern in the form of a vector 1 on . it must be more than 2. The units of measurement of angles are degrees. Elevation angles should be in the range of −90° to 90° inclusive and arranged in strictly ascending order.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna and the Input Pattern Coordinate System parameter to az-el.
Phi Angles (deg) — values of the Phi angles of the antenna radiation pattern
[0:360] (default) | real vector is row 1 on P
The angular coordinates of the Phi points where the antenna radiation pattern is set. They are defined as a real vector-row 1 on . it must be more than 2. The units of measurement of angles are degrees. The values of the Phi angles should be in the range from 0° to 360° and arranged in strictly ascending order.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna and the Input Pattern Coordinate System parameter to phi-theta.
Theta Angles (deg) — values of the angles of the Theta radiation pattern of the antenna
[0:180] (default) | real vector-row 1 on Q
The angular coordinates of the Theta points where the antenna radiation pattern is set. They are defined as a real vector-row 1 on . it must be more than 2. The units of measurement of angles are degrees. The values of the Theta angles must range from 0° to 180° and be arranged in strictly ascending order.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna and the Input Pattern Coordinate System parameter to phi-theta.
Magnitude pattern (dB) — the magnitude of the antenna radiation pattern
zeros(181.361) (default) | real matrix Q on P | real array Q on P on L
The value of the antenna pattern, set as a matrix on or an array on on .
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If the Input Pattern Coordinate System parameter is set to `az-el', then is equal to the length of the vector defined by the Elevation angles (deg) parameter, in turn, — the length of the vector defined by the Azimuth angles (deg) parameter.
-
If the Input Pattern Coordinate System parameter is set to `phi-theta', then is equal to the length of the vector defined by the parameter Theta Angles (deg), in turn, — the length of the vector defined by the Phi Angles (deg) parameter.
Value is equal to the value of the Operating frequency vector (Hz) parameter.
-
If the value of this parameter is a matrix on , then the same scheme is applied for all frequencies specified in the parameter Operating frequency vector (Hz).
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If the value is an array on on , each element on The array defines a template for the corresponding frequency specified in the parameter Operating frequency vector (Hz).
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna.
Phase pattern (deg) — phase of the radiation pattern of the user antenna
zeros(181,361) (default) | real matrix Q on P | real array Q on P on L
The phase radiation pattern of the combined antenna, defined as a matrix on or an array on on .
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If the Input Pattern Coordinate System parameter is set to `az-el', then is equal to the length of the vector defined by the Elevation angles (deg) parameter, in turn, — the length of the vector defined by the Azimuth angles (deg) parameter.
-
If the Input Pattern Coordinate System parameter is set to `phi-theta', then is equal to the length of the vector defined by the parameter Theta Angles (deg), in turn, — the length of the vector defined by the Phi Angles (deg) parameter.
Value is equal to the value of the Operating frequency vector (Hz) parameter.
-
If the value of this parameter is a matrix on , then the same scheme is applied for all frequencies specified in the parameter Operating frequency vector (Hz).
-
If the value is an array on on , each element on The array defines a template for the corresponding frequency specified in the parameter Operating frequency vector (Hz).
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna.
Align element normal with array normal — align the normal of the antenna array element relative to the grid normal
enabled (by default) | disabled
If the parameter value is enabled, the radiation pattern of the antenna element is rotated to align with the normal of the array. If it is off, then the drawing of the element does not rotate.
If the antenna is used in an antenna array and the Input Pattern Coordinate System parameter has the value az-el, checking this box rotates the radiation pattern so that the x-axis of the element coordinate system points along the normal of the array. If there is no selection, the element template is used without rotation.
If the antenna is used in an antenna array and the Input Pattern Coordinate System parameter has the value phi-theta, checking this box rotates the radiation pattern so that the z axis of the element coordinate system points along the normal of the array.
Use this parameter together with the Array Normal parameter of the URA and UCA arrays.
Dependencies
To use this parameter, set the Element type parameter to Custom Antenna.
Radiation pattern beamwidth (deg) — the beam width of the antenna pattern
[10, 10] (default) | real scalar | a real vector is a 1 by 2 row
The beam width of the antenna pattern in degrees.
Dependencies
To use this parameter, set the Element type parameter to Gaussian Antenna.
Polar pattern frequencies (Hz) — frequency values for the polar pattern of the microphone
1e3 (default) | real scalar | real vector-row 1 on L
The frequency values for the polar radiation pattern are set as a real scalar or a real vector-row 1 on . The frequencies are in the frequency range specified by the parameter Operating frequency vector (Hz).
Dependencies
To use this parameter, set the Element type parameter to Custom Microphone.
Polar pattern angles (deg) — angle values for the polar radiation pattern of the microphone
[-180:180] (default) | real vector is row 1 on P
The angle values for the polar radiation pattern of the microphone are set as a vector . The angles are measured from the central axis of the microphone and should be in the range of −180° to 180° inclusive.
Dependencies
To use this parameter, set the Element type parameter to Custom Microphone.
Polar pattern (dB) — polar directional pattern of the microphone
zeros(1,361) (default) | real vector-row 1 on L
Set the value of the polar radiation pattern of the user microphone element in the form of a real vector-row 1 on , where — the number of frequencies specified in the parameter Polar pattern frequencies (Hz). The string represents the value of the polar radiation pattern measured at the corresponding frequency specified in the Polar pattern frequencies (Hz). The radiation pattern is measured in the azimuthal plane. In the azimuthal plane, the elevation angle is 0°, and the central axis is 0° in azimuth and 0° in elevation. The polar radiation pattern is symmetrical around the central axis. Based on the polar diagram, it is possible to construct a microphone directional pattern in three-dimensional space.
Dependencies
To use this parameter, set the Element type parameter to Custom Microphone.
Array
Geometry — geometry of the pass array:q[<br>] ULA (default) | URA | UCA | Conformal Array
The geometry of the array, set as:
-
'ULA' is a uniform linear array.
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`URA' is a uniform rectangular array.
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'UCA' is a uniform circular array.
-
`Conformal Array' — arbitrary arrangement of elements.
Number of elements — number of elements of the pass array:q[<br>] 2 for ULA arrays and 5 for UCA arrays (default) | an integer greater than or equal to 2
The number of array elements for ULA or UCA arrays, set as an integer greater than or equal to 2.
Dependencies
To use this parameter, set the Geometry parameter to ULA or `UCA'.
Array size — dimensions of the URA pass array:q[<br>] [2 2] (default) | positive integer | vector of positive integers 1 by 2
The dimensions of the URA array, specified as a positive integer or a vector of positive integers 1 by 2.
-
If the size of the array is a 1 by 2 vector, then the vector has the form
[NumberOfArrayRows,NumberOfArrayColumns]. -
If the size of the array is an integer, then the array has the same number of rows and columns.
To do this, the array elements are indexed from top to bottom in the leftmost column, and then move to the next columns from left to right. The figure shows an array for which the Array size parameter has the value [3 2], that is, it has three rows and two columns.
Dependencies
To use this parameter, set the Geometry parameter to `URA'.
Element spacing (m) — the distance between the elements of the pass array:q[<br>] 0.5 for ULA arrays and [0.5 0.5] for URA arrays (default) | positive scalar for ULA or URA arrays | vector of positive integers 1 by 2 for URA arrays
The distance between adjacent array elements:
-
'ULA` — specify the distance between two adjacent array elements as a positive scalar.
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URA' — the distance is set as a positive scalar or a vector of positive values 1 by 2. If Element spacing (m) is a scalar, then the distances between rows and columns are equal. If Element spacing(m) is a vector, then the vector has the form `[SpacingBetweenArrayRows,SpacingBetweenArrayColumns].
Dependencies
To use this parameter, set the Geometry parameter to ULA or `URA'.
Array axis — direction of the ULA pass linear axis:q[<br>] y (default) | x | z
The direction of the ULA linear axis, set as y, x or z. All elements of the ULA array are evenly distributed along this axis in the local coordinate system of the array.
Dependencies
-
To use this parameter, set the Geometry parameter to
ULA. -
This parameter is also used if the block supports only ULA arrays.
Element lattice — grid of positions of URA pass elements:q[<br>] Rectangular (default) | Triangular
A grid of URA element positions, set as rectangular or triangular.
-
'Rectangular' — aligns all elements in rows and columns.
-
Triangular— shifts the elements of an even row of a rectangular grid towards the positive direction of the row axis. The offset is half the distance between the elements according to the size of the row.
Dependencies
-
To use this parameter, set the Geometry parameter to `URA'.
Array normal — the direction of the normal of the pass array:q[<br>] x for URA arrays or z for UCA arrays (default) | y
The normal direction of the array, specified as x, y, or z.
The elements of flat arrays lie in a plane orthogonal to the selected direction of the array normal. The directions of the angular coordinates of the elements are directed along the direction of the normal of the array.
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The 'x` elements of the array lie in the yz plane. The angular coordinate vectors of all elements are directed along the x-axis.
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The 'y` elements of the array lie in the zx plane. The angular coordinate vectors of all elements are directed along the y axis.
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The 'z` elements of the array lie in the xy plane. The angular coordinate vectors of all elements are directed along the z axis.
Dependencies
To use this parameter, set the Geometry parameter to URA or `UCA'.
Radius of UCA (m) — radius of the UCA pass array:q[<br>] 0.5 (default) | positive scalar
The radius of the UCA array, a positive scalar.
Dependencies
To use this parameter, set the Geometry parameter to UCA.
Element positions (m) — positions of elements of the conformal array
[0, 0, 0] ( by default) | a 3-by-N real matrix
The positions of the elements of the conformal array, given as a matrix of real values 3 on , where — 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 local coordinate system of the array. The origin of the local coordinate system is (0,0,0). The units of measurement are meters.
Dependencies
To use this parameter, set the Geometry parameter to `Conformal Array'.
Element normals (deg) — direction of the normal vectors of the elements of the conformal array
[0, 0] | ` column vector 2 by 1 | matrix 2 by N
The direction of the normal vectors of the elements of a conformal array, specified as a 2-by-1 column vector or a 2-by-1 matrix . means the number of elements in the array. For the matrix, each column specifies the direction of the normal of the corresponding element in the form of [azimuth,elevation] relative to the local coordinate system. In the local coordinate system, the positive x-axis coincides with the direction of the normal to the conformal array. If the parameter value is a 2-by-1 column vector, then the same pointing direction is used for all elements of the array.
Parameters of Element positions (m) and Element normals (deg) can be used to represent any arrangement in which pairs of elements differ from each other by certain transformations. These transformations can include translation, azimuth rotation, and elevation rotation. However, transformations that require rotation relative to the normal direction cannot be used.
Dependencies
To use this parameter, set the Geometry parameter to `Conformal Array'.
Taper — changing the radiation pattern of the elements of the antenna array
1 (default) | complex scalar | complex vector
The change in the radiation pattern of the antenna array elements is set as a complex scalar or a complex vector 1 by , where — the number of antenna array elements.
The coefficients that change the radiation pattern, also called element weights, multiply the responses of the antenna array elements. The coefficients change both the amplitude and the phase of the response to reduce the side lobes or the direction of the main axis of the response.
If the value of the Taper parameter is a scalar, then the same weight is applied to each element. If Taper is a vector, then a weight from the vector is applied to the corresponding element of the antenna array. The number of scales must correspond to the number of antenna array elements.
Learn more about generalized side lobe suppression
The Generalized Side Lobe Suppressor (GSC) is an efficient implementation of a linear minimum dispersion limiting (LCMV) beam shaper. The LCMV beamformer minimizes the output power of the array while maintaining power in one or more preset directions. This type of beam shaper is called a limited beam shaper. It is possible to calculate exact weights for a limited beamformer, but with a large number of elements, calculations will be costly. Calculations require the inversion of a large spatial covariance matrix. The GSC algorithm transforms the LCMV adaptive optimization problem with constraints into an adaptive problem without constraints, which simplifies its implementation.
In the GSC algorithm, the incoming sensor data is divided into two signal paths, as shown in the block diagram. The upper path is a conventional beam shaper. The lower path is an adaptive unlimited beamformer, the purpose of which is to minimize the output power of the GSC. The GSC algorithm consists of the following steps:
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Pre-alignment of the element sensor data by time shifting the incoming signals. Pre-alignment in time aligns all the signals of the sensor elements. The time shift depends on the angle of the incoming signal.
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Passing preprocessed signals through the upper path to a conventional beam shaper with fixed weights .
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Passing preprocessed signals through the lower path into the blocking matrix . The blocking matrix is orthogonal to the signal and removes the signal from the lower path.
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Filtering of lower path signals through a set of FIR filters. The Signal path FIR filter length parameter sets the length of the filters. Filter coefficients are the weights of adaptive filters. .
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Calculation of the difference between the upper and lower signal paths. This difference is the GSC output signal generated by the beam.
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Return of the formed output beam back to the filter. Adaptation of the filter weights using the least mean squares (LMS) method. The adaptive LMS step size is the value specified in the Adaptive filter step size parameter divided by the total signal power.
