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Approximating a Lithium-polymer dielectric constant

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Koen:
Hello,

I would like to calculate something but the formula requires me to know the dielectric constant of a Lithium-polymer battery pack (cheap single cell Shenzhen type). I tried Google and a few material databases but found nothing. Would you have an idea ?

Thank you,
Koen

uncle_bob:
Hi

What are you trying to calculate? Put another way, is this an RF or microwave sort of number or an audio number that you are after?

Bob

Koen:
I've got another weird idea. I'd like to try an RF patch antenna with a Lithium-polymer battery for dielectric instead of FR4 or ceramic. I've got an okay one running by trial and error earlier and would now like to compute improved dimensions. I'm using this "tutorial" : http://orbanmicrowave.com/wp-content/uploads/2014/12/Orban-Patch-Antennas-2009-rev.pdf (page 3) :

--- Quote ---A good approximation for the resonant length is:
L = 0.49 * Lambda d = 0.49 * ( Lambda 0 / SquareRoot(Er) )

This formula includes a first order correction for the edge extension due to the fringing
fields, with:
• L = resonant length
• Lambda d = wavelength in PC board
• Lambda 0 = wavelength in free space
• Er = dielectric constant of the printed circuit board material
--- End quote ---

Thank you !

uncle_bob:

--- Quote from: Koen on June 12, 2016, 02:32:51 am ---I've got another weird idea. I'd like to try an RF patch antenna with a Lithium-polymer battery for dielectric instead of FR4 or ceramic. I've got an okay one running by trial and error earlier and would now like to compute improved dimensions. I'm using this "tutorial" : http://orbanmicrowave.com/wp-content/uploads/2014/12/Orban-Patch-Antennas-2009-rev.pdf (page 3) :

--- Quote ---A good approximation for the resonant length is:
L = 0.49 * Lambda d = 0.49 * ( Lambda 0 / SquareRoot(Er) )

This formula includes a first order correction for the edge extension due to the fringing
fields, with:
• L = resonant length
• Lambda d = wavelength in PC board
• Lambda 0 = wavelength in free space
• Er = dielectric constant of the printed circuit board material
--- End quote ---

Thank you !

--- End quote ---

Hi

You are talking about an organic so it's going to have all sorts of strange "fun" in it's dielectric characteristics vs frequency. Best guess: it's lossy as all get out at the frequencies you are talking about. Most organics are (think heating things in the microwave). There are exceptions (teflon) but they are all very good insulators.

Bob

Koen:
Do you expect it to be pure crap ? Or would it be impossible to reliably produce because of the battery variations ?

It's for a GNSS antenna (1.57-1.62 GHz). I currently have a correct linear polarisation omni but wanted to give a circular polarisation directional a try to avoid multipath problems. First try without any thinking yielded good enough results to pursue experimentation. I'll prepare A/B tests today.

I had something like the attachment in mind, with the battery between patch and ground plane because space is at a premium.

Thank you !

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