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The wavelength dependence of atmospheric absorption creates range cues in hyperspectral measurements that can be exploited for passive ranging using only thermal emissions. In this work, we present fundamental limits on absorption-based ranging under a model of known air temperature and wavelength-dependent attenuation coefficient, with object temperature and emissivity unknown; reflected solar and environmental radiance is omitted from our analysis. Fisher information computations illustrate how performance limits depend on atmospheric conditions such as air temperature and humidity; temperature contrast in the scene; spectral resolution of measurement; and distance. These results should prove valuable in sensor system design.
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Propagation of THz radiation in air over a broad range of atmospheric temperature and humidity conditions
Abstract As the need for higher data rates for communication increases, the terahertz (THz) band has drawn considerable attention. This spectral region promises a much wider bandwidth and the transmission of large amounts of data at high speeds. However, there are still challenges that need to be addressed before the THz telecommunications technology hits the consumer market. One of the recurring concerns is that THz radiation is greatly absorbed by atmospheric water-vapor. Although many studies have presented the attenuation of THz signals under different atmospheric conditions, these results analyze specific temperature or humidity values, leaving the need for a more comprehensive analysis over a wider range of climate conditions. In this work, we present the first study of the attenuation of THz radiation over a broad range of temperatures and humidity values. It is worth noticing that all of our measurements have been undertaken at atmospheric pressure unlike many previous studies where the pressure was not kept constant for various temperatures. Furthermore, we extend our analysis beyond the impact of absolute humidity on the bit error rate in THz communications. We also discuss the refractivity of the atmosphere, examining its variations across different temperatures and humidity levels. THz propagation is studied using two different measurement systems, a long-path THz time-domain spectrometer as well as a quasi-optic setup with vector network analyze. We also compare the results with the ITU-R P.676-13 propagation model. We conclude that the attenuation at the absorption peaks increases linearly with water content and has no dependence on the temperature, while the refractive index, away from absorption lines, namely at 300 GHz shows a sub-linear increase with humidity.
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- PAR ID:
- 10504125
- Publisher / Repository:
- .
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2045-2322
- Page Range / eLocation ID:
- 20782
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41598-023-47586-8
