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rainpl

RF signal attenuation due to rainfall

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Syntax

l =雨（范围，频率，雨rate）
L = rainpl(range,freq,rainrate,elev)
L = rainpl(range,freq,rainrate,elev,tau)
L = rainpl(range,freq,rainrate,elev,tau,pct)

Description

example

L= rainpl(range,freq,rainrate)returns the signal attenuation,L, due to rainfall. In this syntax, attenuation is a function of signal path length,range, signal frequency,freq和降雨率，rainrate。The path elevation angle and polarization tilt angles are assumed to zero.

Therainplfunction applies the International Telecommunication Union (ITU) rainfall attenuation model to calculate path loss of signals propagating in a region of rainfall[1]。当信号路径完全包含在均匀的降雨环境中时，该功能适用​​。降雨速率沿信号路径不变。衰减模型仅适用于1-1000 GHz的频率。

example

L= rainpl(range,freq,rainrate,elev)also specifies the elevation angle,elev, of the propagation path.

example

L= rainpl(range,freq,rainrate,elev,tau)also specifies the polarization tilt angle,tau, of the signal.

L= rainpl(range,freq,rainrate,elev,tau,pct)also specifies the specified percentage of time,pct。pctis a scalar in the range of 0.001–1, inclusive. The attenuation,L, is computed from a power law using the long-term statistical 0.01% rain rate (in mm/h).

Examples

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Open Live Script

Compute the signal attenuation due to rainfall for a 20 GHz signal over a distance of 10 km in light and heavy rain.

Propagate the signal in a light rainfall of 1 mm/hr.

rr = 1.0; L = rainpl(10000,20.0e9,rr)
L = 1.3009

在10 mm/hr的大雨中传播信号。

RR = 10.0;L = Rainpl（10000,20.0E9，RR）
L = 8.1584
Open Live Script

Plot the signal attenuation due to a 20 mm/hr statistical rainfall for signals in the frequency range from 1 to 1000 GHz. The path distance is 10 km.

rr = 20.0; freq = [1:1000]*1e9; L = rainpl(10000,freq,rr); semilogx(freq/1e9,L) grid xlabel('Frequency (GHz)'）ylabel（'Attenuation (dB)')

Figure contains an axes object. The axes object contains an object of type line.

Open Live Script

Compute the signal attenuation due to heavy rain as a function of elevation angle. Elevation angles vary from 0 to 90 degrees. Assume a path distance of 100 km and a signal frequency of 100 GHz.

将降雨速率设置为10 mm/hr。

RR = 10.0;

Set the elevation angles, frequency, range.

elev = [0:1:90]; freq = 100.0e9; rng = 100000.0*ones(size(elev));

Compute and plot the loss.

L = rainpl(rng,freq,rr,elev); plot(elev,L) grid xlabel(“路径高度（学位）”）ylabel（'Attenuation (dB)')

Figure contains an axes object. The axes object contains an object of type line.

Open Live Script

计算由于重型rainfa信号衰减ll as a function of the polarization tilt angle. Assume a path distance of 100 km, a signal frequency of 100 GHz, and a path elevation angle of 0 degrees. Set the rainfall rate to 10 mm/hour. Plot the signal attenuation versus polarization tilt angle.

Set the polarization tilt angle to vary from -90 to 90 degrees.

tau = -90:90;

设置高程角，频率，路径距离和降雨速率。

elev = 0; freq = 100.0e9; rng = 100e3*ones(size(tau)); rr = 10.0;

Compute and plot the attenuation.

L = rainpl(rng,freq,rr,elev,tau); plot(tau,L) grid xlabel('Tilt Angle (degrees)'）ylabel（'Attenuation (dB)')

Figure contains an axes object. The axes object contains an object of type line.

Input Arguments

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Signal path length, specified as a nonnegative real-valued scalar, or as aM-by-1 or 1-by-M向量。单位为米。

Example:[13000.0,14000.0]

信号频率，指定为正面价值标量或无负标率N-by-1 or 1-by-N向量。Frequencies must lie in the range 1–1000 GHz.

Example:[1400.0E6,2.0E9]

Long-term statistical rain rate, specified as a nonnegative real-valued scalar. The long-term statistical rain rate is the rain rate that is exceeded 0.01% of the time. You can adjust the percent of time using thepctargument. Units are in mm/hr.

Example:1.5

Signal path elevation angle, specified as a real-valued scalar, or as anM-by-1 or 1-by-M向量。Units are in degrees between –90° and 90°. Ifelevis a scalar, all propagation paths have the same elevation angle. Ifelevis a vector, its length must match the dimension ofrangeand each element inelevcorresponds to a propagation range inrange。

Example:[0,45]

Tilt angle of the signal polarization ellipse, specified as a real-valued scalar, or as anM-by-1 or 1-by-M向量。Units are in degrees between –90° and 90°. Iftauis a scalar, all signals have the same tilt angle. Iftauis a vector, its length must match the dimension ofrange。在这种情况下，每个元素taucorresponds to a propagation path inrange。

The tilt angle is defined as the angle between the semi-major axis of the polarization ellipse and thex-axis. Because the ellipse is symmetrical, a tilt angle of 100° corresponds to the same polarization state as a tilt angle of -80°. Thus, the tilt angle need only be specified between ±90°.

Example:[45,30]

Exceedance percentage of rainfall, specified as a positive scalar between 0.001 and 1. The long-term statistical rain rate is the rain rate that is exceededpctof the time. Units are dimensionless.

Data Types:double

Output Arguments

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Signal attenuation, returned as a real-valuedM-by-Nmatrix. Each matrix row represents a different path whereMis the number of paths. Each column represents a different frequency whereNis the number of frequencies. Units are in dB.

More About

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Rainfall Attenuation Model

This model calculates the attenuation of signals that propagate through regions of rainfall. Rain attenuation is a dominant fading mechanism and can vary from location-to-location and from year-to-year.

Electromagnetic signals are attenuated when propagating through a region of rainfall. Rainfall attenuation is computed according to the ITU rainfall modelRecommendation ITU-R P.838-3: Specific attenuation model for rain for use in prediction methods。The model computes the specific attenuation (attenuation per kilometer) of a signal as a function of rainfall rate, signal frequency, polarization, and path elevation angle. The specific attenuation,ɣR, is modeled as a power law with respect to rain rate

γ R = k R α ,

whereRis rain rate. Units are in mm/hr. The parameterk和指数αdepend on the frequency, the polarization state, and the elevation angle of the signal path. The specific attenuation model is valid for frequencies from 1–1000 GHz.

To compute the total attenuation for narrowband signals along a path, the function multiplies the specific attenuation by the an effective propagation distance,deff。Then, the total attenuation isL = deffγR。

有效距离是几何距离，d, multiplied by a scale factor

r = 1 0.477 d 0.633 R 0.01 0.073 α f 0.123 − 10.579 ( 1 − exp ( − 0.024 d ) )

wheref是频率。文章Recommendation ITU-R P.530-17 (12/2017): Propagation data and prediction methods required for the design of terrestrial line-of-sight systemspresents a complete discussion for computing attenuation.

The rain rate,R, used in these computations is the long-term statistical rain rate,R0.01。This is the rain rate that is exceeded 0.01% of the time. The calculation of the statistical rain rate is discussed inRecommendation ITU-R P.837-7 (06/2017): Characteristics of precipitation for propagation modelling。This article also explains how to compute the attenuation for other percentages from the 0.01% value.

You can apply the attenuation model to wideband signals. First, divide the wideband signal into frequency subbands and apply attenuation to each subband. Then, sum all attenuated subband signals into the total attenuated signal.

参考

[1]Radiocommunication Sector of International Telecommunication Union.Recommendation ITU-R P.838-3: Specific attenuation model for rain for use in prediction methods。2005.

[2] Radiocommunication Sector of International Telecommunication Union.建议ITU-R P.530-17：陆地视线系统设计所需的传播数据和预测方法。2017.

[3]Recommendation ITU-R P.837-7: Characteristics of precipitation for propagation modelling

[4] Seybold, J.Introduction to RF Propagation。New York: Wiley & Sons, 2005.

Extended Capabilities

Version History

Introduced in R2017b

See Also

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