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surfacegamma

Gamma value for different terrains

Syntax

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

Description

`G = surfacegamma(TerrainType)` returns the $\gamma$ value for the specified terrain. The $\gamma$ 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 $\gamma$ values. These $\gamma$ values are for an operating frequency of 10 GHz.

Input Arguments

 `TerrainType` Character vectors that describe the terrain type. 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 $\gamma$ in decibels, for constant $\gamma$ clutter model.

Examples

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

```fc = 300e6; g = surfacegamma('woods',fc); clutter = phased.ConstantGammaClutter('Gamma',g,... 'Sensor',phased.CosineAntennaElement,... 'OperatingFrequency',fc); x = clutter(); r = (0:numel(x)-1)/(2*clutter.SampleRate) * ... clutter.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, $\gamma$, to describe clutter characteristics of different types of terrain. Values of $\gamma$ are derived from measurements.

Algorithms

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

The $\gamma$ values for the terrain types `'farmland'`, ```'wooded hill'```, and `'flatland'` are from [3].

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

`$\gamma ={\gamma }_{0}+5\mathrm{log}\left(\frac{f}{{f}_{0}}\right)$`

where ${\gamma }_{0}$ 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.

See Also

Introduced in R2011b

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