Radar Cross Section

Before setting up and constraining a radar system, STK Radar enables you to specify an important property of a potential radar target: its radar cross section (RCS). To design a radar system, it is essential to be able to describe the target's echo, which is a function of its size, shape, and orientation. RCS is the projected area of a metal sphere that would return the same echo signal as the target if it were substituted for the target. STK Radar provides the means to specify:

The RCS of all targets at the scenario level.
Set RCS individually for each target.

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

RCS options for scenario objects

The RF properties of the vehicle classes — Aircraft , Ground Vehicles, Launch Vehicle Properties, Missiles, Satellites, and Ships — and those for the Facility, Place, and Target classes include an RCS page.

The term "target", used in discussions of radar to refer to an object of interest to a radar system, should not be confused with the Target class, which is used in STK to represent locations on the Earth's surface.

To set the RCS properties for an object, open its RCS page, which is under the RF node in the properties tree.

RCS bands

The RCS table consists of a list of one or more bands in the range 3 MHz - 300 GHz, each with a specified RCS value. The following parameters appear for each band in the list:

Parameter	Description
MinFrequency	This is the minimum frequency in the range. If it is the first (lowest) or only band, the value of this parameter is 3 MHz.
MaxFrequency	This is the maximum frequency in the range. If it is the last (highest) or only band, the value of this parameter is 300 GHz.
ComputeType	Select one of the following: Constant Value: Enter a value in the constant RCS field. Ansys HFSS CSV File: Use this to load the aspect-dependent Ansys HFSS exported complex scattering RCS data files. STK can import one or two CSV files. Each file contains half of the complex scattering matrix RCS data. The primary file represents H-H and V-H elements, while the second file contains the orthogonal polarization data V-V and H-V elements. You must ensure that the two files have exactly the same number of data points (Rho, Theta, start/stop angle limits). When you update or change a file, STK will check that the number of data points in each file is the same. If you are loading two new files, you can ignore any error message from this check after the first file loads and just click Yes to continue. The check should pass without error after the second changed file loads. External File: To load the Aspect Dependent RCS file, enter its path and file name in the Filename field or click ( ... ) and browse for it. See External RCS Files for an example and format of an RCS file. Script Plugin: To load the script, enter its path and file name in the Script Filename field or click ... and browse for it. The plugin script is not automatically reloaded after you make changes to it. To reload the script, click Reload. For a list of required inputs and outputs, see Radar Cross Section Plugin Point. RCS COM plugin: If an RCS COM plugin exists on your machine and is properly registered, it will appear on the Compute Type selection list. For more information, see Plugin Points and Engine Plugin Registration.
SwerlingCase	Select one of five Swerling cases (0, I, II, III, IV). To account for RCS fluctuations, STK Radar uses a set of fluctuation models developed by P. Swerling. Swerling Case 0 assumes no fluctuation. Cases I and III assume that fluctuations are correlated during a scan but uncorrelated from one scan to the next. In Cases II and IV, fluctuations are more rapid and are assumed to be uncorrelated from pulse to pulse. Skolnik, Merrill I., Introduction to Radar Systems, 2nd ed., New York: McGraw-Hill (1980), pp. 46-52. On detection probability generally see the seminal article by Mitchell, R.L. and J.F. Walker, "Recursive Methods for Computing Detection Probabilities," IEEE Transactions on Aerospace Electronic Systems, Vol. 7, No. 4 (July 1971), pp. 671-676.

Editing the RCS band table

To insert a band, under Band Insert Parameters, enter the Min Frequency and Max Frequency that define the new band and click Insert.

To delete a band from the table, select it and click Delete.

To modify a band property, overwrite the value in the table or select the band and overwrite the value under Band Properties. If the selected band has a Min value of 300 MHz, MinFrequency is disabled; similarly, if the selected band has a Max value of 300 GHz, MaxFrequency is disabled.

You can also change the Swerling Case and ComputeType values for multiple bands. To do that, multi-select the bands, and change either or both of the Swerling Case and Compute Type values located under Band Properties.

To merge bands, click Merge. This causes neighboring bands with identical settings for the Swerling and Value parameters to merge into a single band with the cumulative frequency range of the affected bands prior to merger. Selecting one or more bands in the list is unnecessary and has no effect on the merging process.

Inheriting RCS settings

Instead of setting RCS properties for the individual object in question, you can opt to have it inherit the RCS settings that you made at the scenario level by clicking the appropriate textbox. If you select this option, it disables all fields on the RCS page.

Setting RCS at the scenario level

The scenario-level RCS page is the same for other objects except that it lacks the Inherit option. The advantage of being able to set RCS at the scenario level is that you can define certain minimum performance specifications that your radar system must satisfy, including the RCS of any potential target. This is less time consuming and less prone to error than setting the RCS for each potential target individually.