clutter_model

clutter_model … end_clutter_model
clutter_model <derived-name> <base-name>
   ... Input for the clutter model ...
end_clutter_model

Overview

clutter_model can be used to create configured clutter models that can be referenced in the definition of a WSF_RADAR_SENSOR. <derived-name> is the name by which the user wishes to refer to the configured clutter model. <base-name> is one of the Available Clutter Models:

According to Skolnik, Introduction to Radar (3rd Ed.), “Clutter strength is defined to be \sigma^0F^4, where \sigma^0 is the clutter cross-section per unit area, and F is the propagation factor that sometimes appears in the radar equation to account for propagation effects such as multipath reflections, diffraction, and attenuation.” The default clutter strength tables, as found in Billingsley’s book Low Altitude Land Clutter, are functions of both land_cover and land_formation , as well as frequency and polarization.

Effective Use Of Clutter Models

A clutter model definition may be embedded directly in the definition of a radar. For example, assume you have a file called ‘ex_radar.txt’:

sensor EX_RADAR WSF_RADAR_SENSOR
   transmitter
      ... transmitter commands ...
   end_transmitter
   receiver
      ... receiver commands ...
   end_receiver
   clutter_model surface_clutter
      ... surface_clutter commands ...
   end_clutter_model
end_sensor

The problem with this method is that one must modify the radar definition to change or eliminate the clutter model. In many production uses this is undesirable or infeasible. What would be more desirable is to provide a ‘default’ clutter model definition that can be overridden.

The new ‘ex_radar.txt’ would now contain:

# Define the 'default' clutter model
clutter_model EX_RADAR_CLUTTER surface_clutter
   ... surface_clutter commands ...
end_clutter_model

sensor EX_RADAR WSF_RADAR_SENSOR
   transmitter
      ... transmitter commands ...
   end_transmitter
   receiver
      ... receiver commands ...
   end_receiver
   clutter_model EX_RADAR_CLUTTER    # References the clutter model symbolically
end_sensor

Then to override the clutter model:

#include ex_radar.txt

# Provide a new definition that overrides the existing definition.
# This example disables clutter calculations.

clutter_model EX_RADAR_CLUTTER none
end_clutter_model

The radar model will use the last definition of EX_RADAR_CLUTTER when it finally creates instances of the radar in the simulation.

Available Clutter Models

none

A ‘dummy’ clutter model that is the equivalent of no clutter.

clutter_model <derived-name> none
end_clutter_model

surface_clutter_table

surface_clutter_table represents clutter by a table, which is typically generated by sensor_plot. The table contains clutter data as a function of target altitude and target range. Additionally, if the table is site-specific it will also contain data as a function of target bearing.

Note

The number of ranges in each altitude block are independent. A minimum of 1 range is required for each altitude block.

A site-independent clutter table has the following form:

clutter_model <derived-name> WSF_SURFACE_CLUTTER_TABLE
   clutters
      altitude <length-value>
        range <length-value>  clutter <power-value>
        ...
        range <length-value>  clutter <power-value>
      altitude <length-value>
        range <length-value>  clutter <power-value>
        ...
        range <length-value>  clutter <power-value>
        ...
      altitude <length-value>
        range <length-value>  clutter <power-value>
        ...
        range <length-value>  clutter <power-value>
      ...
   end_clutters
end_clutter_model

A site-specific table is similar in form, except that bearing data are included for the set of ranges, as follows:

clutter_model <derived-name> WSF_SURFACE_CLUTTER_TABLE
   clutters
      altitude <length-value>
         bearing <angle-value>
           range <length-value>  clutter <power-value>
           ...
           range <length-value>  clutter <power-value>
           ...
         bearing <angle-value>
           // Full set of ranges:
           range <length-value>  clutter <power-value>
           ...
           range <length-value>  clutter <power-value>
           ...
         ...
      altitude <length-value>
         bearing <angle-value>
           range <length-value>  clutter <power-value>
           ...
           range <length-value>  clutter <power-value>
           ...
         ...
      ...
   end_clutters
end_clutter_model

alarm

The ALARM clutter model utilizes the high-fidelity model from the ALARM model.

surface_clutter

This is an algorithmic model that computes the clutter power. It uses the parameters from the global_environment for determining land formation, land coverage and sea state.

Important

For surface platforms, this clutter model is intended to be used in ships with antennas of significant height compared to wave height (as specified by sea_state). In the case of low antenna height, other geometrical conflicts occur, and may produce undesired results.

clutter_model <derived-name> surface_clutter
end_clutter_model
use_legacy_data <boolean-value>

Specified whether to use an older set of tables of clutter strength.

Default disabled