NRCS Value for landreflectivity function greater than 1 for mmWave band at grazing angle of 90 degreees

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I am trying to estimate the Normalized RCS of ground surface using the included code. The only model applicable in this frequency band is 'APL'. I read the cited reference in detail and tried to understand how the model is implemented in MATLAB. After verification, I reached the conclusion that the model is indeed implemented flawlessly. However, the value of NRCS greater than 1 does not make much sense to me.

I am getting very high values. Please guide me through this issue with an explanatio

clc

clear all

R=150;

az=60;

el=20;

freq=77.16e9;

graz=90;

nrcs_type(1)="LowRelief";

nrcs_type(2)="HighRelief";

nrcs_type(3)="Urban";

for i=1:1:3

nrcs(i) = landreflectivity(nrcs_type(i),graz,freq,'Model','APL');

rcs(i) = surfclutterrcs(nrcs(i),R,az,el,graz,1);

fprintf(nrcs_type(i));

fprintf('\nNRCS: %d\n',nrcs(i));

fprintf('RCS: %d \n',rcs(i));

end

Answer 1

[Saurav]

Hi @Maaz Ali,

I see that the estimation of the Normalized Radar Cross Section (NRCS) using the 'APL' model has resulted in values greater than 1.

The NRCS measures the radar energy scattered back by a surface, normalized by the surface area.

• Although NRCS is often interpreted as a probability or fraction, it can represent a power ratio that may exceed the 0-1 range, especially in radar applications involving complex terrains or structures.
• In radar applications, particularly at high frequencies and for complex surfaces, elevated NRCS values are possible.

To learn more about the exact calculations of NRCS values based on frequency and grazing angle, refer to Section A.5.3 of the reference paper [4] mentioned in the 'landreflectivity' documentation:

https://www.mathworks.com/help/radar/ref/landreflectivity.html#References

The NRCS is modified based on frequency and grazing angle, particularly across various terrain types. These adjustments can result in NRCS values exceeding 1 (or 0 dB), especially in urban areas or at high frequencies, which clarifies the elevated NRCS values observed in the simulation.

To explore further, try adjusting the grazing angle. This will demonstrate that elevated NRCS values are not always the case and depend on factors such as frequency, terrain type and grazing angles, as discussed above.

I hope this will help you to proceed ahead with your work!