EngeePhased.BackscatterRadarTarTarget
Backscatter radar target.
| Library |
EngeePhased |
| Block |
Description
The EngeePhased.BackscatterRadarTarget system object models the object’s backscatter diagram from the target.
Backscatter is a special case of radar target scattering when the angles of incidence and reflection are the same. This type of scattering is applicable to monostatic radar configurations. The radar backscatter pattern defines the response of the target to the incident signal as a reflected signal.
This system object allows you to define an angle-dependent backscatter pattern that covers a range of incident angles.
The EngeePhased.BackscatterRadarTarget system object creates a backscatter signal for polarised and unpolarised signals. Although EMR signals are always polarised, it is often possible to ignore polarisation in modelling and treat signals as scalar. To ignore polarisation, specify false for the EnablePolarization property. To use polarisation, set the EnablePolarization property to true.
For unpolarised signals, you specify backscatter as an array of values for the effective scattering area at individual points in azimuth and elevation. The system object interpolates the values of the angles of incidence between the points in the array.
For polarised signals, the radar scattering matrix is specified using three arrays defined at discrete points in azimuth and elevation. These three arrays correspond to the polarisation components HH, HV and VV. The VH component is calculated by usage of the conjugate symmetry property of the HV component.
For the unpolarised and polarised signal, one of four Drilling models can be used to create random fluctuations in the EPR scattering matrix. Select the model using the Model property. Then use the SeedSource and Seed properties to control the fluctuations.
EnablePolarisation property |
Use these properties |
|
RCSPattern |
|
ShhPattern, SvvPattern and ShvPattern |
To perform radar backscatter, follow the steps below:
-
Create an EngeePhased.BackscatterRadarTarTarget object and set its properties.
-
Call the object with arguments as if it were a function.
Syntax
Creation
You can call the system object constructor in the following ways:
-
object = EngeePhased.BackscatterRadarTarTargetcreates a backscatter radar target with property values by default. Example:target = EngeePhased.BackscatterRadarTarget -
object = EngeePhased.BackscatterRadarTarget(Name=Value)creates a target with the specified DOR with each specified property Name (name) set to the specified Value (value). You can specify additional arguments as a name-value pair in any order (Name1=Value1,…,NameN=ValueN). Example:target = EngeePhased.BackscatterRadarTarget(EnablePolarization=true, Model=Swerling2)
Usage
-
refl_sig = Function Name(sig,ang)returns the reflected signal (output argument refl_sig), from an incident unpolarised signal (input argument sig) arriving at the target at the angle specified in the argument ang. This syntax applies when the EnablePolarisation property is set tofalseand the Model property toNonfluctuating. In this case, the values specified in the RCSPattern property are used to calculate the EPR for the incident and reflected directions (ang argument). -
refl_sig = Function name(sig,ang,update)uses the update input argument to control the updating of the EPR values. This syntax is used when the EnablePolarisation property is set tofalseand the Model property is set to one of the fluctuating EPR models:Swerling1,Swerling2,Swerling3, orSwerling41. If the value of the update property istrue, a new EPR value is generated. If the value of the update property isfalse, the previous EPR value is used. -
refl_sig = Function Name(sig,ang,laxes)returns the reflected signal (output argument refl_sig), from the incident polarised signal (input argument sig). The input argument matrix laxes specifies the local coordinate system of the target. This syntax applies if the EnablePolarisation parameters are set totrueand the Model property is set toNonfluctuating. The values specified in the ShhPattern, SvvPattern and ShvPattern properties are used to calculate the scattering matrices for the incident and reflected directions (argument ang). -
refl_sig = Function Name(sig,ang,laxes,update)uses the update input argument to control the update of the scattering matrix values. This syntax is used when setting the EnablePolarisation property totrueand the Model property to one of the fluctuating EPR models:Swerling1,Swerling2,Swerling3orSwerling4. If the value of update istrue, a new EPR value is generated. If update isfalse, the previous EPR value is used.
Properties
EnablePolarisation -
Enable polarised signals
false (by default) | true
Details
The property that allows polarised signals to be processed is set as false or true.
Set this property to true to allow the target to simulate the reflection of polarised radiation.
Set this property to false to ignore polarisation.
*Example: true.
Data types: logical
AzimuthAngles -
azimuth angles
[-180:180] (By default) | ` vector of real rows 1 by P` | ` vector of real columns P by 1`
Details
Azimuthal angles given as a vector of length P. P must be at most two.
Used to define angular coordinates of each column of matrices specified in RCSPattern, ShhPattern, ShvPattern or SvvPattern properties.
The units of measurement are degrees.
Example: [-45:0,1:45]
Data types: Float64
ElevationAngles -
elevation angles
[-90:90] (by default) | ` vector of real rows 1 by Q` | ` vector of real columns Q by 1`
Details
Elevation angles given as a vector of length Q. Q must be greater than two.
Used to determine the angular coordinates of each row of matrices specified by RCSPattern, ShhPattern, ShvPattern or SvvPattern properties.
The units of measurement are degrees.
Example: [-30:0.1:30]
Data types: Float64
RCSPattern -
effective scattering area
ones(181,361) (By default) | real matrix Q on P | real array Q on P on M | real vector 1 on P | real matrix M on P
Details
The effective scattering area given as a real matrix Q on P or a real array Q on P on M.
Q is the length of the vector in the ElevationAngles property.
P is the length of the vector in the AzimuthAngles property.
M is the number of bodies defined by EPR.
The number of patterns corresponds to the number of signals in the sig argument passed to the function. However, it is possible to use one pattern to model several signals reflecting from one target.
You can also specify a pattern as a function of only the azimuth for a single elevation. In this case, specify the pattern as a vector 1 on P or a matrix M on P. Each row is a different body with its own EPR.
The units are m^2.
This property applies if the EnablePolarisation property is set to false.
*Example: [1,.5;.5,1]
Data types: Float64
ShhPattern -
radar scattering matrix of the HH-polarisation component
ones(181,361) (By default) | complex matrix Q on P | complex array Q on P on M | complex vector 1 on P | complex matrix M on P
Details
A radar scattering matrix with polarisation component HH, given as a complex matrix Q on P or a complex array Q on P on M.
Q is the length of the vector in the ElevationAngles property.
P is the length of the vector in the AzimuthAngles property.
M - number of target templates.
The number of templates corresponds to the number of signals in the sig argument passed to the function. However, you can use one template to model several signals reflecting from one target.
You can also set the template as a function of only the azimuth for a single elevation. Then specify the pattern as a vector 1 on P or a matrix M on P. Each row is a different body with its own EPR.
The units of measurement are m.
This property is applied if the EnablePolarisation property is set to true.
*Example: [1,1;1i,1i].
Data types: Float64
Support for complex numbers: Yes
SvvPattern -
radar scattering matrix of the VV polarisation component
ones(181,361) (By default) | complex matrix Q on P | complex array Q on P on M | complex vector 1 on P | complex matrix M on P
Details
The scattering matrix of a radar with polarisation component VV, given as a complex matrix Q on P or a complex array Q on P on M.
Q is the length of the vector in the ElevationAngles property.
P is the length of the vector in the AzimuthAngles property.
M - number of target templates.
The number of patterns corresponds to the number of signals in the sig argument passed to the function. However, you can use one pattern to model several signals reflecting from one target.
You can also set the pattern as a function of only the azimuth for a single elevation. In this case, specify the pattern as a vector 1 on P or a matrix M on P. Each row is a different body with its own EPR.
The units of measurement are m.
This property applies if the EnablePolarisation property is set to true.
*Example: [1,1;1i,1i].
Data types: Float64
Support for complex numbers: Yes
ShvPattern -
radar scattering matrix of the HV-polarisation component
ones(181,361) (By default) | complex matrix Q on P | complex array Q on P on M | complex vector 1 on P | complex matrix M on P
Details
The scattering matrix of a radar with polarisation component VV, given as a complex matrix Q on P or a complex array Q on P on M.
Q is the length of the vector in the ElevationAngles property.
P is the length of the vector in the AzimuthAngles property.
M - number of target patterns. The number of patterns corresponds to the number of signals in the aig argument passed to the function. However, you can use one pattern to model several signals reflecting from one target.
The number of patterns corresponds to the number of signals in the aig argument passed to the function. However, you can use one pattern to simulate multiple signals reflecting from the same target.
You can also specify a pattern as a function of only the azimuth for a single elevation. In this case, specify the pattern as a vector 1 on P or a matrix M on P. Each row is a different pattern.
The units of measure are m.
This property applies if the EnablePolarisation property is set to true.
*Example: [1,1;1i,1i].
Data types: Float64
Support for complex numbers: Yes
Model -
EPR fluctuation model
Nonfluctuating (by default) | Swerling1 | Swerling2 | Swerling3 | Swerling4
Details
A target fluctuating model specified as Nonfluctuating, Swerling1, Swerling2, Swerling3 or Swerling4.
If you set this property to a value other than Nonfluctuating, use the update input argument when calling the function.
*Example: Swerling3.
Data types: char
PropagationSpeed
propagation speed
physconst(LightSpeed) (by default) | positive scalar
Details
The propagation speed of the signal, specified as a positive scalar. By default, the propagation speed value returned by physconst(LightSpeed) is used.
The unit of measurement is m/s.
*Example: 3e8
Data types: Float64
OperatingFrequency -
operating frequency
300e6 (by default) | positive scalar
Details
Operating frequency specified as a positive scalar.
The unit of measurement is Hz.
*Example: 1e9
Data types: Float64
SeedSource -
setting the random number generator for the EPR fluctuation model
Auto (by default) | `Property `
Details
Source of the random number generator for the EPR fluctuation model, set as Auto or Property.
When this property is set to Auto, the EngeePhased.BackscatterRadarTarget system object generates random numbers using the default random number generator.
When you set this property to Property, you specify the initial value of the random number generator using the Seed property. This property is applied when you set the Model property to Swerling1, Swerling2, Swerling3, or Swerling4.
*Example: Property.
Data types: char
Seed -
initial random number generator
0 (by default) | ` integer non-negative number less than 2^32`
Details
Initial random number generator specified as a non-negative integer less than 2^32.
This property applies if the SeedSource property is set to Property.
*Example: 32301
Data types: Float64
Arguments
Input
sig -
narrowband signal
complex matrix N on M | complex array 1 on M
Details
A narrowband unpolarised signal given as a complex matrix N on M. The value N is the number of signal samples and M is the number of signals reflected from the target. Each column corresponds to an independent signal incident at a different reflection angle.
A narrowband polarised signal given as a 1 by M array of structures containing fields with complex values. Each struct element contains three N by 1 column vectors of electromagnetic field components (sig.X,sig.Y,sig.Z) representing the polarised signal reflected from the target.
For polarised fields, the struct element contains three N by 1 complex column vectors, sig.X, sig.Y and sig.Z. These vectors represent the Cartesian components x, y and z of the polarised signal.
The size of the first dimensionality of the matrix fields in the structure may be varied to simulate a varying signal length, such as a pulsed waveform with a variable pulse repetition rate.
*Example: [1,1;j,1;0.5,0]
Data types: Float64
Support for complex numbers: Yes
ang -
direction of incoming signal
vector-column 2 by 1 with positive real value | matrix-column 2 by M with positive real value
Details
The direction of the incident signal given as a 2-by-1 positive real column vector or a 2-by-M positive real column matrix.
Each column ang specifies the direction of the incident signal as a pair [AzimuthAngle;ElevationAngle].
The number of columns in ang must correspond to the number of independent signals in the argument sig.
The units of measurement are degrees.
*Example: [30;45]
Data types: Float64
update -
EPR update
false (by default) | true
Details
Allow updating of EPR values for fluctuation models, set as false or true.
If the update property is set to true, a new EPR value is generated each time the function is called.
If the update property is set to false, the EPR remains unchanged at each function call.
*Example: true.
Data types: logical
laxes -
local coordinate matrix
eye(3,3) (by default) | orthonormal matrix of 3 by 3 real values | array of 3 by 3 real values on M
Details
A matrix of a local coordinate system given as a 3-by-3 orthonormal real matrix or a 3-by-3 array of real values on M. The columns of the matrix specify the orthonormal axes x, y and z of the local coordinate system, respectively.
Each axis represents a vector of the form (x;y;z) with respect to the global coordinate system.
If the sig argument has only one signal, laxes is a 3 by 3 matrix.
If the sig argument has multiple signals, you can use a single 3 by 3 matrix for multiple signals in sig. In this case, all targets have the same local coordinate systems. When you specify laxes as a 3 by 3 by M array, each page (the third index) defines a 3 by 3 local coordinate matrix for the corresponding target.
*Example: [1,0,0;0,0.7071,-0.7071;0,0.7071,0.7071]
Data types: Float64
Output
refl_sig — narrowband reflected signal
complex matrix N on M | complex structural array 1 on M
Details
A narrowband unpolarised signal given as an N by M complex matrix. Each column contains an independent signal reflected from the target.
The value N is the number of signal samples and M is the number of signals reflected from the target. Each column corresponds to the reflection angle.
A narrowband polarised signal given as an array struct of size 1 by M containing complex values. Each element of struct contains three N by 1 columns of electromagnetic field component vectors (sig.X,sig.Y,sig.Z) representing the polarised signal reflected from the target.
For polarised fields, the struct element contains three N by 1 complex column vectors, sig.X, sig.Y and sig.Z. These vectors represent the x, y and z Cartesian components of the polarised signal.
The output signal refl_sig contains the signal samples arriving at the signal destination during the current input time slot. If the propagation time from source to destination exceeds the duration of the current time frame, the output does not contain all contributions from the current time frame input. The remaining output appears at the next function call.
Optional
*`Reverse backscattered radiation
For a narrowband unpolarised signal, the reflected signal, , is equal to:
where
-
- incoming signal.
-
- is the target gain, a dimensionless value defined as follows:
-
- effective scattering area of the target.
-
- the wavelength of the incoming signal.
The signal incident on the target is scaled by the square root of the gain.
For narrowband polarised waves, the unit scalar signal, , is replaced by a vector signal, , with horizontal and vertical components. The scattering matrix, , replaces the scalar cross section, . Using the scattering matrix, incident horizontally and vertically polarised signals are converted into reflected horizontally and vertically polarised signals.