Integration Gain | Radar Cross Section (RCS)

External Radar Files

The following sections describe external file formats used by STK Radar.

IntegrationGain file format

The following is a sample IntegrationGain file used in search/track radar:

GoalSNRPulseIntegrationMethod v1
Interpolate No
NumPoints 5
2     2.5
4     5.0
8     7.5
16   10.0
32   12.5

IntegrationGain File Keywords

Keyword Description
GoalSNRPulseIntegrationMethod v1 Indicates the data format and version of the file format.
This parameter is required and must be the first line in the file.
Interpolate Allows (does not allow) interpolation between the defined pulse numbers.
NumPoints The number of ordered (pulse, gain) pairs specified in the GainData section.

External RCS files

You can create an external Radar Cross Section (RCS) file with real-valued pattern data or complex-valued pattern data.

With Rho and Theta being the coordinates of a unit sphere, RCS data file requirements are:

  • For symmetric RCS data, specify only a single column of coordinates (represented in Rho space).
  • If the RCS data is non-symmetric, the matrix cannot have the dimensions (1 x n) or (m x 1) in (Rho, Theta) space. It must contain at least two columns and two rows of (Rho, Theta) coordinates such that the Rho and Theta ranges constitute a rectangular matrix.

For more information on real and complex data formats, see FullRealMatrix File Format or FullComplexScatterMatrix File Format.

For descriptions and detailed diagrams of the RCS Theta and Rho angles, click here.

Descriptions of the keywords used in an RCS file follow.

Starting with STK 9, the RCSPatternType <pattern type> keyword replaces the real pattern file types. Specifically, FullRealMatrix replaces RCS Full Pattern, MonostaticRealSparse replaces Monostatic Nearest Neighbor, and BistaticRealSparse replaces Bistatic Nearest Neighbor. Also, RealSymmetric replaces the IsSymmetric {yes | no} keyword.

Keyword Description
RCSValuesLinearScale Indicates that the RCS data is in linear scale and the units are meters squared. STK will convert as required. The RCS data can be in dBSm or in linear scale. The default unit setting for RCS data is dBSm and is compatible with previous versions.
RCSComplexValuesPolar Indicates that the RCS data is in the complex number polar format. STK accepts RCS complex values as a magnitude/phase pair and converts the data to a real/imaginary form for computations. See the sample file.
RCSPatternType <Pattern Type>

Specifies one of the following real or complex pattern types:

Real Pattern Types

  • RealSymmetric. Symmetric (around Rho angle) real valued RCS data. Each RCS data point is a single real value. RealSymmetric replaces the deprecated keyword IsSymmetric {yes | no}, which is still supported for backward compatibility.
  • FullRealMatrix. RCS data is a full pattern matrix with real valued data. Each point is defined by the Rho-Theta pair and contains a single data point. The matrix must be complete, and can contain zero valued elements.
  • MonostaticRealSparse. This follows the Monostatic Nearest Neighbor algorithms. The data matrix may be sparse. The RCS data values are real.
  • BistaticRealSparse. The bistatic format supports the bistatic radar operations. The incident and the reflected angles may not be the same. The matrix may be sparse and RCS data values are real.

Complex Pattern Types

  • FullComplexScatterMatrix. The RCS matrix is a full pattern block matrix. Yet, each data element of the matrix is a 2 x 2 polarization scattering matrix. Each element of the scattering matrix is complex valued data. Each RCS matrix point is defined by the Rho-Theta pair and contains a single scattering matrix.
  • MonoComplexScatterSparse. The RCS type is the monostatic complex scatter matrix with sparse data. The basic format is like the MonostaticRealSparse format, but extended for the complex polarization scatter matrix.
  • BiComplexScatterSparse. The RCS type is the bistatic complex scatter matrix with sparse data. The basic format is like the BistaticRealSparse format, but extended to accommodate complex polarization scatter matrix data.

The 2 x 2 RCS scatter matrix is valid for all three complex pattern types.

For more information on real and complex data formats, see FullRealMatrix File Format or FullComplexScatterMatrix File Format.

RCSComplexValuesEField

Explicitly declares the Complex RCS data type to be EField Scattering Matrix. (The default data type is RCS Scattering Matrix.) If an EField Scattering Matrix is provided then the RCS Scattering Matrix elements are computed by taking the square of the EField Matrix elements. The RCS data provider reports the interpolated Scattering Matrix complex elements.

If the input data represents the ComplexRCSMatrix then the data matrix elements 11, 12, 21, 22 reported by the RCS data provider are the interpolated values of the RCS matrix. RCS, RCSCrossPol, RCSOrthoCrossPol, and RCSOrthoPol are computed by STK and reported by the RCS data provider.

When the input data represents complex EField Scattering Matrix, the data matrix elements 11, 12, 21, 22 reported by the RCS data provider are the interpolated values of the Complex EField Scattering Matrix. (You are able to see the interpolated EField values computed from the input data.)

The interpolated EField values are converted to Complex RCS values and used to compute RCS, RCSCrossPol, RCSOrthoCrossPol, and RCSOrthoPol values. These are reported by the RCS data provider.
RCSScatterMatrixBasis <Orthogonal Basis>

Each RCS data point is the complex valued 2 x 2 polarization scattering matrix. This 2 x 2 RCS scatter matrix may be specified for linear or circular polarization.

<Orthogonal Basis> values are:

  • ComplexRCSMatrix. The RCS data is a complex valued matrix.
  • RHC_LHC_OrthogonalPair. The scattering matrix defines the LHC and RHC polarization orthogonal basis. The radar transmit signal polarizations are divided into LHC and RHC components. These complex vectors are multiplied by the polarization complex scattering matrix to get the reflected signal components. The reflected signal components are received by the respective orthogonal radar receiver pair.
  • Horizontal_Vertical_OrthogonalPair. The scattering matrix defines the vertical and horizontal polarization orthogonal basis. The radar transmit signal polarizations are divided into vertical and horizontal components. These complex vectors are multiplied by the polarization complex scattering matrix to get the reflected signal components. The reflected signal components are received by the respective orthogonal radar receiver pair.

Ansys HFSS RCS data in CSV file format

Ansys HFSS can compute Complex RCS for targets based on their geometry and material characteristics. It exports complex RCS data in the CSV file format.

Each run of HFSS produces results for one signal source polarization. For example, a signal source model with horizontal (H) polarization computes RCS returns for the H-H (H incident and H reflected signal polarization) combination and for V-H (H incident and V reflected signal polarization). V is the vertical polarization.

A second run produces data for V signal polarization and computes RCS returns for the V-V (V incident and V reflected signal polarization) combination and for H-V (V incident and H reflected signal polarization).

STK can use each data file independently when processing single polarization type. However, you can combine the exported files to produce a Complex Scattering RCS Matrix for [HH, HV, VH, VV] RCS Values.

STK reads the column headers in the CSV format files and parses the RCS data frequency value, the polarization scattering matrix element (H-H, V-H, H-V, V-V), Phi angle start value (degrees), and Phi angle stop value. It then computes the Phi angle step value.

The first column of the CSV file represents the theta angle values. Each row corresponds to the RCS data row in the scattering matrix. The starting, ending, and step size for the theta values are determined by reading the first column data.

The following conditions apply:

  • The scattering matrix data is expected to conform to a polar coordinate frame with uniform step size for Theta and Phi angles.
  • The RCS data reference axis is the X axis of the target body.
  • If you use two files to import the full scattering matrix, the matrix size and the Theta and Phi angles extents and the step sizes must be same for the two files.
  • The frequency values listed in the two RCS data files must be same.

You can view two example sample files for 2.8GHz, one for H_Incident and one for V_Incident. The first column represents the theta values. The column header row (first row of the CSV file) shows the polarization, the frequency values, and the Phi angle values. The data in column two and beyond are complex RCS data values in the format a + bi.

H_Incident sample

V_Incident sample

2 x 2 RCS Scatter Matrix definition

The 2x2 RCS scatter matrix is defined as:

RCS1 1 = RCS primary polarization channel.
RCS1 2 = RCS cross polarization leakage to orthogonal channel.
RCS2 1 = RCS orthogonal cross polarization leakage to primary channel.
RCS2 2 = RCS orthogonal polarization channel.

FullRealMatrix File Format

The following table defines the keywords for a FullRealMatrix external file. See the sample file for further information.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
IsSymmetric Legal value is yes or no. A symmetric RCS uses only the value to determine RCS.

The RealSymmetric RCSPatternType keyword has replaced the IsSymmetric keyword, which is still supported for backward compatibility.
RhoPoints The number of values in the following data.
ThetaPoints The number of values in the following data.
BEGIN (END) rcsdata

Signifies the beginning (end) of the aspect-dependent data. The data is entered in ordered triplets of (, , rcs) with and real numbers measured in degrees and rcs a real number in dBsm or Sm units.

 

The valid range for is 0.0 <= <= 180.0 and for is -180.0 <= <= 180.0. is measured around the axis in a counterclockwise direction with 0.0 deg being the parent Z axis (RhoFromX) or the parent X axis (RhoFromZ).

The following is a FullRealMatrix external file:

stk.v.9.0
BEGIN rcs
  RCSPatternType	FullRealMatrix
  RhoAxis     RhoFromZ
	RhoPoints	5
	ThetaPoints	5
	BEGIN rcsdata
		0		-180		-20
		0		-90		-10
		0		0		  0
		0		90		 10
		0		180		 20
		45		-180		-19
		45		-90		 -9
		45		0		  1
		45		90		 11
		45		180		 21
		90		-180		-18
		90		-90		 -8
		90		0		  2
		90		90		 12
		90		180		 22
		135		-180		-17
		135		-90		 -7
		135		0		  3
		135		90		 13
		135		180		 23
		180		-180		-16
		180		-90		 -6
		180		0		  4
		180		90		 14
		180		180		 24
	END rcsdata
END RCS

RealSymmetric file format

The following table defines the keywords for a RealSymmetric Pattern external file. See the sample file for further information.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
RhoPoints The number of values in the following data.
BEGIN (END) rcsdata

Signifies the beginning (end) of the aspect-dependent data. The data is entered in ordered pairs of (, rcs) with a real number measured in degrees and rcs a real number in dBsm or Sm units.

 

The valid range for is 0.0 <= <= 180.0.

MonostaticRealSparse file format

The following table defines the keywords for a MonostaticRealSparse external file. See the sample file for further information.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
NumPoints The number of (, , rcs) values in the following data.
BEGIN (END) rcsdata Signifies the beginning (end) of the aspect-dependent data. The data is entered in triplets of (, , rcs) with and real numbers measured in degrees and rcs a real number in dBsm or Sm units. The valid range for is 0.0 <= <= 180.0. and for is -180.0 <= <= 180.0.

BistaticRealSparse file format

The following table defines the keywords for a BistaticRealSparse external file. See the sample file for further information.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
NumPoints The number of (incident , incident , reflected , reflected , rcs) values in the following data.
BEGIN (END) rcsdata

Signifies the beginning (end) of the aspect-dependent data. The data is entered as (incident , incident , reflected , reflected , rcs) with and real numbers measured in degrees and rcs a real number in dBsm or Sm units.

 

The valid range for is 0.0 <= <= 180.0. and for is -180.0 <= <= 180.0. is measured around the axis in a counterclockwise direction with 0.0 deg being the parent Z axis (RhoFromX) or the parent X axis (RhoFromZ).

FullComplexScatterMatrix File Format

The following table defines the keywords for a FullComplexScatterMatrix external file. The RCS data matrix as well as the each of the polarization complex scattering matrixes must be complete, and may contain zero-valued elements.

The format follows the same pattern as the FullRealMatrix format, where each point is defined by Rho, Theta, and RCS values.

Note that the data values must be separated by at least one space and must not extend over multiple lines. Complex numbers must be specified completely with real and imaginary parts. Complex RCS is represented in the Polar format by specifying the RCSComplexValuesPolar keyword. The imaginary part of the number must not precede or follow any imaginary value indicators, such as “i” or “j”. Complex values with a zero real or imaginary part must be specified as such. A sample of the complex polarized scattering matrix data line follows:

Rho Theta rcs11Re rcs11Im rcs12Re rcs12Im rcs21Re rcs21Im rcs22Re rcs22Im
30  45    2.5     3.4     0.0     3.6     3.7     0.0     1.8     2.2

See the sample file for more information.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
RhoPoints The number of values in the following data.
ThetaPoints The number of values in the following data.
BEGIN (END) rcsdata Signifies the beginning (end) of the aspect-dependent data. The data is entered as (incident , incident , reflected , reflected , rcs) with and real numbers measured in degrees and rcs a real number in dBsm or Sm units.

 

The valid range for is 0.0 <= <= 180.0. and for is -180.0 <= <= 180.0. is measured around the axis in a counterclockwise direction with 0.0 deg being the parent Z axis (RhoFromX) or the parent X axis (RhoFromZ).

 

The FullComplexScatterMatrix format extends the basic pattern to contain full complex scattering matrix per line of the data file:

 

Rho Theta rcs11Re rcs11Im rcs12Re rcs12Im rcs21Re rcs21Im rcs22Re rcs22Im

The following is a FullComplexScatterMatrix external file:

stk.v.9.0
BEGIN rcs
	RCSPatternType   FullComplexScatterMatrix
  RhoAxis     RhoFromZ
	RCSValuesLinearScale
	RCSScatterMatrixBasis Horizontal_Vertical_OrthogonalPair
	RhoPoints	5
	ThetaPoints	5
	BEGIN rcsdata
	   0    -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	END rcsdata
END RCS

MonoComplexScatterSparse file format

The following table defines the keywords for a MonoComplexScatterSparse external file.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
NumPoints The number of (, , rcs) values in the following data.
BEGIN (END) rcsdata

Signifies the beginning (end) of the aspect-dependent data. The data is entered in ordered triplets of (, , rcs) with and real numbers measured in degrees and rcs a complex scattered matrix in dBsm or Sm units.

 

The valid range for is 0.0 <= <= 180.0 and for is -180.0 <= <= 180.0. is measured around the axis in a counterclockwise direction with 0.0 deg being the parent Z axis (RhoFromX) or the parent X axis (RhoFromZ).

 

The FullComplexScatterMatrix format extends the basic pattern to contain the full complex scattering matrix per line of the data file:

 

Rho Theta incident Rho Theta reflected rcs11Re rcs11Im rcs12Re rcs12Im rcs21Re rcs21Im rcs22Re rcs22Im

The following is a MonoComplexScatterSparse external file:

stk.v.9.0
BEGIN rcs
	RCSPatternType   MonoComplexScatterSparse
  RhoAxis     RhoFromZ
	RCSValuesLinearScale
	RCSScatterMatrixBasis Horizontal_Vertical_OrthogonalPair
	RhoPoints	5
	ThetaPoints	5
	BEGIN rcsdata
	   0    -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   0    180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   45   0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   90   180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  -180   0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   135  0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  -90    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  0      0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  90     0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	   180  180    0.2   0.0   0.0  0.1    0.0  0.1    0.70710  0.0
	END rcsdata
END RCS

BiComplexScatterSparse file format

The following table defines the keywords for a BiComplexScatterSparse external file.

Keyword Description
BEGIN (END) RCS Signifies the beginning (end) of the RCS data.
RhoAxis Determines the axis from which is measured. is the total angle between the axis and the target RCS aspect vector. Legal values for this parameter are RhoFromX and RhoFromZ, signifying that the axis is the parent object's X or Z axis, respectively.
NumPoints The number of (incident , incident , reflected , reflected , rcs) values in the following data.
BEGIN (END) rcsdata

Signifies the beginning (end) of the aspect-dependent data. The data is entered as (incident , incident , reflected , reflected , rcs) with and real numbers measured in degrees and rcs a complex scattered matrix in dBsm/Sm units.

 

The valid range for is 0.0 <= <= 180.0. and for is -180.0 <= <= 180.0. is measured around the axis in a counterclockwise direction with 0.0 deg being the parent Z axis (RhoFromX) or the parent X axis (RhoFromZ).

 

The bistatic complex scatter matrix format extends the basic pattern to contain bistatic complex scattering matrix per line of the data file:

 

Rho Theta rcs11Re rcs11Im rcs12Re rcs12Im rcs21Re rcs21Im rcs22Re rcs22Im