surfacegamma

Gamma value for different terrains

Syntax

G = surfacegamma(TerrainType)
G = surfacegamma(TerrainType,FREQ)
surfacegamma

Description

G = surfacegamma(TerrainType) returns the γ value for the specified terrain. The γ value is for an operating frequency of 10 GHz.

G = surfacegamma(TerrainType,FREQ) specifies the operating frequency of the system.

surfacegamma displays several terrain types and their corresponding γ values. These γ values are for an operating frequency of 10 GHz.

Input Arguments

TerrainType

String that describes type of terrain. Valid values are:

  • 'sea state 3'

  • 'sea state 5'

  • 'woods'

  • 'metropolitan'

  • 'rugged mountain'

  • 'farmland'

  • 'wooded hill'

  • 'flatland'

FREQ

Operating frequency of radar system in hertz. This value can be a scalar or vector.

Default: 10e9

Output Arguments

G

Value of γ in decibels, for constant γ clutter model.

Examples

Determine the γ value for a wooded area, and then simulate the clutter return from the area. Assume the radar system uses a single cosine pattern antenna element and an operating frequency of 300 MHz.

fc = 300e6;
g = surfacegamma('woods',fc);
hclutter = phased.ConstantGammaClutter('Gamma',g,...
    'Sensor',phased.CosineAntennaElement,...
    'OperatingFrequency',fc);
x = step(hclutter);
r = (0:numel(x)-1) / (2*hclutter.SampleRate) * ...
    hclutter.PropagationSpeed;
plot(r,abs(x));
xlabel('Range (m)'); ylabel('Clutter Magnitude (V)');
title('Clutter Return vs. Range');

More About

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Gamma

A frequently used model for clutter simulation is the constant gamma model. This model uses a parameter, γ, to describe clutter characteristics of different types of terrain. Values of γ are derived from measurements.

Algorithms

The γ values for the terrain types 'sea state 3', 'sea state 5', 'woods', 'metropolitan', and 'rugged mountain' are from [2].

The γ values for the terrain types 'farmland', 'wooded hill', and 'flatland' are from [3].

Measurements provide values of γ for a system operating at 10 GHz. The γ value for a system operating at frequency f is:

γ=γ0+5log(ff0)

where γ0 is the value at frequency f0 = 10 GHz.

References

[1] Barton, David. "Land Clutter Models for Radar Design and Analysis," Proceedings of the IEEE. Vol. 73, Number 2, February, 1985, pp. 198–204.

[2] Long, Maurice W. Radar Reflectivity of Land and Sea, 3rd Ed. Boston: Artech House, 2001.

[3] Nathanson, Fred E., J. Patrick Reilly, and Marvin N. Cohen. Radar Design Principles, 2nd Ed. Mendham, NJ: SciTech Publishing, 1999.

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