SAR Constraints

The following SAR property pages allow for the imposition of a variety of constraints on synthetic aperture (SAR) radar.

SAR. These parameters correspond to the main channel (SAR).
SAR w/Jamming. These parameters correspond to the main channel under jamming. For more information on the effects of jamming on constraints, see Constraints with Jamming.
SAR OrthoPol. These parameters are enabled when the receiver side orthogonal polarization is selected.
SAR OrthoPolJam. These parameters are enabled when the receiver side orthogonal polarization is selected. For more information on the effects of jamming on constraints, see Constraints with Jamming.

The STK Radar SAR computation and constraints can be extended with the Search/Track plug-in constraint. See SAR User Plugin.

Except for Sigma N (below), SAR constraints are available only if SAR mode is enabled in the radar's Basic properties (SAR page).

To constrain SAR performance, select minimum and/or maximum values for one or more of the following parameters:

Option	Description
SNR	Signal-to-noise ratio for the SAR radar. Enter Min and/or Max SNR.
CNR	Clutter-to-noise ratio for the SAR radar. Enter Min and/or Max CNR.
SCR	Signal-to-clutter ratio for the SAR radar. Enter Min and/or Max SCR.
Sigma N	Additive noise is commonly defined in terms of Sigma N, i.e. the effective backscatter coefficient of the additive noise. Enter Min and/or Max value.
PTCR	The point target-to-clutter ratio for the SAR radar. Enter Min and/or Max PTCR.
Integration Time	The fixed integration time or time to achieve the desired azimuth resolution, depending on the setting of the analysis mode when defining the radar. This constraint and the Azimuth Resolution constraint are mutually exclusive. Enter Min and/or Max integration time.
Azimuth Resolution	The fixed azimuth resolution or the resolution achievable within the desired integration time, depending on the setting of the analysis mode when defining the radar. This constraint and the Integration Time constraint are mutually exclusive. Enter Min and/or Max azimuth resolution.
Area Rate	The coverage rate of the SAR. Enter Min and/or Max area rate as the ratio of the selected distance unit squared to the selected time unit.
Image Area	The image area of the SAR. Enter Min and/or Max image area.

SAR User Plugin

The SAR User Plugin constraint extends STK Radar performance computations. You can create a SAR plugin script using MATLAB, VB, or PERL. STK interfaces with the script and provides updated object geometry, Vector Geometry Tool (VGT) data and radar performance data at each time step of the scenario execution. The script uses the STK-supplied data to compute a new parameter and return the value to STK. For more information, see Custom Plugins for Radar Search/Track and SAR Constraints.

Option	Description
File	Select Min to enable the plugin constraint option and browse to the plugin script file. A fully functional template (VB_RadarSARNIIRSConstraint.vbs) is provided for your use. All STK inputs to the script and the output from the script are already programmed in the template. A simple data model is programmed as an example. You can replace the template example model with your own model equations. The radar-target geometry data and VGT data is independent of the radar's operational mode and is supplied to the SAR plugin script.
Min/Max	If the constraint data needs to limit the access visibility intervals, enter the appropriate minimum and/or maximum values.
Exclude Time Intervals	Excludes the time intervals during which the constraint is satisfied.