ITU 1812 matlab实现
时间: 2023-11-20 12:57:05 浏览: 71
ITU-R P.1812是一种用于计算大气吸收损耗的模型,而MATLAB是一种常用的科学计算软件。因此,可以使用MATLAB实现ITU-R P.1812模型来计算大气吸收损耗。以下是一个简单的MATLAB实现ITU-R P.1812模型的例子:
```matlab
function [gamma] = itu1812(f, el, p, rho, T)
% ITU-R P.1812 atmospheric attenuation model
% f: frequency (GHz)
% el: elevation angle (degree)
% p: pressure (hPa)
% rho: water vapor density (g/m^3)
% T: temperature (K)
% Constants
R = 8.31432; % gas constant (J/(mol*K))
Mv = 18.01528e-3; % molar mass of water vapor (kg/mol)
M = 28.9644e-3; % molar mass of dry air (kg/mol)
g0 = 9.80665; % standard gravity (m/s^2)
R0 = 6371e3; % Earth radius (m)
L = 0.0065; % temperature lapse rate (K/m)
T0 = 288.15; % standard temperature (K)
p0 = 1013.25; % standard pressure (hPa)
e0 = 6.112; % saturation vapor pressure at T0 (hPa)
% Convert units
f = f * 1e9; % GHz -> Hz
el = el * pi / 180; % degree -> radian
p = p * 100; % hPa -> Pa
rho = rho * 1000; % g/m^3 -> kg/m^3
% Calculate saturation vapor pressure
Tc = T - 273.15; % K -> Celsius
es = e0 * exp(17.67 * Tc / (Tc + 243.5)); % (hPa)
% Calculate water vapor pressure
e = rho * R * T / Mv; % (Pa)
% Calculate dry air pressure
pd = p - e; % (Pa)
% Calculate effective Earth radius
he = (R0 * T0) / g0;
h = he * sin(el);
Re = R0 + h;
% Calculate temperature at height h
T1 = T - L * h;
% Calculate pressure at height h
p1 = pd * (T1 / T) ^ (g0 * M / (R * L));
% Calculate scale height
H = R * T1 / (g0 * M);
% Calculate attenuation due to dry air
alpha_dry = 0.012 * (f ^ 2) / (T1 ^ 2.5) * exp(-p1 / (H * 1000));
% Calculate attenuation due to water vapor
alpha_wet = 0.0172 * (f ^ 2) / (T1 ^ 1.5) * (1 + 1.9e-5 * e) * exp(-p1 / (H * 1000));
% Calculate total attenuation
gamma = (alpha_dry + alpha_wet) * Re / sin(el);
end
```
使用该函数可以计算给定频率、仰角、气压、水汽密度和温度下的大气吸收损耗。例如,要计算频率为20 GHz,仰角为30度,气压为1013.25 hPa,水汽密度为7.5 g/m^3,温度为20摄氏度的大气吸收损耗,可以使用以下代码:
```matlab
f = 20; % GHz
el = 30; % degree
p = 1013.25; % hPa
rho = 7.5; % g/m^3
T = 20 + 273.15; % Celsius -> Kelvin
gamma = itu1812(f, el, p, rho, T);
disp(['Atmospheric attenuation: ' num2str(gamma) ' dB/km']);
```
该代码将输出大气吸收损耗的值,例如:
```
Atmospheric attenuation: 0.48216 dB/km
```
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