scholarly journals Attenuation and Dispersion on Terahertz Wireless Channels in Falling Rain

2021 ◽  
Author(s):  
Jianjun Ma ◽  
Peian Li ◽  
Liangbin Zhao ◽  
Jianchen Wang ◽  
Wenbo Liu ◽  
...  
Keyword(s):  
Wireless Channel ◽  
Water Vapor Absorption ◽  
Dispersion Effects ◽  
Communication Technique ◽  
Vapor Absorption ◽  
Terahertz Communication ◽  
Channel Performance ◽  
Spectrometer System ◽  
Attenuation And Dispersion ◽  
Temporal Dispersion

Abstract Investigations on wireless channel performance in adverse weathers could be helpful and important for the future applications of terahertz communication technique in outdoor scenarios. However, in most cases only amplitude performance has been studied by using a broadband-pulsed terahertz source or an amplitude modulated data stream, not including phase degradation (temporal dispersion). This limitation may mask important aspects of channel performance with phase modulation schemes, especially for wide bandwidth signals. In this work, we report the amplitude and phase characterizations of a terahertz channel in falling rain by a time-domain spectrometer system. We also demonstrate error rate performance by a 16 quadrature amplitude modulated (16-QAM) terahertz signal at a data rate of 5 gigabits per second. We observe that, besides strong water vapor absorption, the weak water absorption line could also lead to obvious dispersion effects. Our work highlights the importance of new frequency band boundaries for minimum temporal dispersion and optimized digital communications in the terahertz frequency range.

scholarly journals A Feasibility Study for Simultaneous Estimates of Water Vapor and Precipitation Parameters Using a Three-Frequency Radar

2005 ◽  
Vol 44 (10) ◽  
pp. 1511-1525 ◽  
Author(s):  
R. Meneghini ◽  
L. Liao ◽  
L. Tian
Keyword(s):  
Water Vapor ◽  
Rayleigh Scattering ◽  
Pulse Compression ◽  
Pulse Repetition Frequency ◽  
Center Frequency ◽  
Water Vapor Absorption ◽  
Single Antenna ◽  
Vapor Absorption ◽  
The Cost ◽  
Lower Frequencies

Abstract The radar return powers from a three-frequency radar, with center frequency at 22.235 GHz and upper and lower frequencies chosen with equal water vapor absorption coefficients, can be used to estimate water vapor density and parameters of the precipitation. A linear combination of differential measurements between the center and lower frequencies on one hand and the upper and lower frequencies on the other provide an estimate of differential water vapor absorption. The coupling between the precipitation and water vapor estimates is generally weak but increases with bandwidth and the amount of non-Rayleigh scattering of the hydrometeors. The coupling leads to biases in the estimates of water vapor absorption that depend primarily on the phase state and the median mass diameter of the hydrometeors. For a down-looking radar, path-averaged estimates of water vapor absorption are possible under rain-free as well as raining conditions by using the surface returns at the three frequencies. Simulations of the water vapor attenuation retrieval show that the largest source of error typically arises from the variance in the measured radar return powers. Although the error can be mitigated by a combination of a high pulse repetition frequency, pulse compression, and averaging in range and time, the radar receiver must be stable over the averaging period. For fractional bandwidths of 20% or less, the potential exists for simultaneous measurements at the three frequencies with a single antenna and transceiver, thereby significantly reducing the cost and mass of the system.

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