FTS 21216, Руководство по эксплуатации

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700-SDI-RADAR-LX-80-Man Rev 1 08 Oct 2021 4 /49
2.3.2 RAIN AND WIND
The LX-80’s integrated internal software filters out effects of rain, fog and wind. However, these
filters have some limitations. The majority of measurement inaccuracies caused by environmental
factors can be solved by proper sensor installation (see Chapter 4).
Rain and snow fall reduce the reflectivity of the water surface thus reducing the SNR
2
. However, the
LX-80 is tested and calibrated to detect the surface even under heavy rainfall. For rain and snow
suppression, the most effective solution is to mount the radar so that it points directly at the surface
being measured.
Influence of the wind on the accuracy is negligible in most cases. The only exception is strong wind
as it will create surface waves and turbulence which can be detected as a shift in level. As mentioned
in Section 2.3, the length of the radar averaging filter can be increased so that it reports an average
measurement over a longer period of time to filter out turbulence.
2.3.3 INTERFERENCE AND MULTIPLE RADARS
The radar operates in the W-band from 77 GHz to 81 GHz with continuous linear frequency
modulation within the frequency range. Interference between two or more sensors will require
precise coordination of the central frequencies with a timing synchronization in a range of 25 ns
between each other. Such synchronization is very complex to achieve so the interference probability
between several radars on the same location is very small.
Some wideband radiation sources can introduce small impulse interference for a short period of
time, but this is very unlikely to affect measurements reported by the radar.
2.3.4 FOGGING AND EVAPORATION
Generally, LX-80s are not affected by fog or evaporation. However, heavy evaporation with high
water density in the atmosphere can affect measurement accuracy.
The best solution in most cases is to increase the average period of the averaging filter to get a
better average distance value. As evaporation is a naturally very turbulent event with a significant
difference in atmospheric water density over the surface area over time, averaging of the distance
measurement spectrum solves the accuracy problem.
2.3.5 REFLECTIONS
Water is very reflective medium for the radar waves and most of the power transmitted from the
radar transmitter will be reflected from the water surface. Reflections of the transmitted radar beam
follow the same physical laws as optics in that part of the power is reflected towards the radar, part
of the power is reflected away from the radar, and a small part of power is absorbed by the water.
2
Signal to noise ratio