Rain attenuation at 355.2 GHz in the terahertz wave range was measured with our new 355.2 GHz measuring system under rainfall intensities up to 25 mm/hr. Rain attenuation coefficients were also calculated using four raindrop-size distributions, e Marshall-Palmer (M-P), Best, Polyakova-Shifrin (P-S) and Weibull distributions, and using a specific rain attenuation model for prediction methods recommended by ITU-R. Measurements of a terahertz wave taken at 355.2 GHz were compared with our calculations. Results showed that the propagation experiment was in very good agreement with a calculation from a specific attenuation model for use in prediction method recommended by ITU-R.

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Measurement of Rain Attenuation in Terahertz Wave Range

In order to analyze the impairments of terahertz (THz) and infrared (IR) links caused by attenuation through rain, THz and IR free-space communication channels at 625 GHz and 1550 nm, respectively, with a maximum data rate of 2.5 Gb/s have been developed in our lab. These two links are spatially superimposed and propagate through the same weather conditions. The performance of both channels is analyzed by measuring the power and bit error rates (BERs) in each link. A weather emulating chamber is designed that can generate controllable rain. Under the same conditions, attenuation by rain exhibits higher but comparable performance degradation in the THz channel. Analysis of power attenuation and BERs performance for both links is presented. Numerical simulations of THz and IR attenuation under different rain conditions are conducted and compared with experimental results.

Experimental Comparison of Terahertz and Infrared Signaling in Laboratory-Controlled Rain

The frequency range that extends from 70 to 115 GHz presents low gaseous attenuation and offers the possibility of implementing radio links with capabilities of transporting more than 1 Gb/s over distances up to a few kilometers. A better knowledge of the propagation characteristics of the atmosphere at these frequencies can benefit future technological advances, providing better performance in terms of the use of radio resources. Unfortunately, the number of propagation results communicated for this band is very small. In this paper, propagation in this frequency range is analyzed on the basis of two-year experimental measurements carried out in Madrid, Spain, on a commercial link working at 75 and 85 GHz. Rain attenuation is the most relevant propagation effect in the W-band. Attenuation measurements are processed to remove wet antenna effects, leaving only the path attenuation time series. Statistics obtained from these time series are compared with a number of model predictions that use rain information of various types as input data, assessing in this way their precision and usefulness.

Attenuation Measurements and Propagation Modeling in the W-Band

We have conducted a millimeter wave propagation experiment at 103 GHz (2.9 mm) on a propagation path of 390 m. The results were compared with the rain attenuation calculations from the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size. It has been shown that the Weibull distribution has a good agreement with the experiments.

Rain Attenuation at 103 GHz in Millimeter Wave Ranges

Rain attenuation values were calculated using empirical raindrop-size distributions, which were, Marshall-Palmer (M-P), Best, Polyakova-Shifrin (P-S) and Weibull raindrop-size distributions, and also calculated using a specific rain attenuation model for prediction methods recommended by ITU-R. Measurements of Terahertz wave taken at 313 GHz (0.96 mm) were compared with our calculations. Results showed that the propagation experiment was in very good agreement with a calculation from the specific attenuation model for use in prediction methods by ITU-R.

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Rain Attenuation at Terahertz

The rain attenuation was calculated by using the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size. The results were compared with the recent measurements from 8 to 312.5 GHz at the rain rate R = 50mm/hr. Especially, the Weibull distribution has a good agreement with the measurements at 312.5 GHz (0.96 mm) in the submillimeter wavelength. Specific attenuation values from 1 to 1000 GHz were calculated for a rain temperature of −10°C, 0°C and 20°C by using the Weibull distribution.

M. Sekine

Papers

Rain Attenuation at Millimeter and Submillimeter Wavelengths