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  1. #1
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    hfss radiation boundary clarification

    I have some questions about radiation boundary I want to clarify,

    1) How long should the radiation boundary extend?
    I have heard it should be 1/4 of wavelength.

    If so, which is the correct way to implement?

    Click image for larger version. 

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    1/4 wavelength height and start at position 0 (bottom, ground plane)

    This makes my radiation pattern like this:
    Click image for larger version. 

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    you can see that the bottom of the radiation pattern is cut off, I think due to the radiation boundary assignment..

    Click image for larger version. 

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    1/4 wavelength height above and below, start at position of -1/4 wavelength (i.e not from 0)
    I notice that this option makes the resonant frequency lower than option 1..

    2) Which sides of the radiation box to assign as radiation boundary?
    is it: all faces except the bottom (ground plane) or all faces (including the bottom) except the face the port is on?
    Last edited by Antenna (^.^); 18th September 2015 at 05:16.

    •   Alt18th September 2015, 04:57

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  2. #2
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    Re: hfss radiation boundary clarification

    Hi,

    lambda/4 distance should be applied to all sides of structure. this ensures absorption of signals at boundary with minimal reflection. you can always increase more than lambda/4 but simulation time increases as well.

    there's a change in resonant frequency as the E-field could be disturbed by reflections off the boundary, since the port is directly placed at the same plane as boundary.

    Increase all sides to at least lambda/4. Then try increasing further and there should be minimal or no change in resonant frequency.

    Best of luck


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