Questions about Doppler shift and Doppler spread

Wang Kaining
Wang Kaining Altair Community Member
edited May 2022 in Community Q&A

Hello, I would like to ask how the Doppler spread in the exported ASCII file is calculated, why is the Doppler spread far smaller than the Doppler shift in the same receiving point

 
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  • mvogel
    mvogel
    Altair Employee
    edited May 2022

    The WinProp User guide explains how the Doppler spread is calculated and even provides the equations. You can search for the text Doppler Spread. Here is the beginning of the explanation:

    "Doppler spread is computed based on the power weighted mean Doppler shift and
    represents the square root of the Doppler variance for all ray contributions."

    In your example, the Doppler shift of the rays is mostly between 310 Hz and 340 Hz, with a couple of outliers well below 300 Hz. The spread, is not the distance between the smallest and the largest shift, but is a weighted expression of the variation in shifts. In your example, it comes out at 35 Hz, which seems reasonable.

     

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