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PSoC™ 4 Forum Discussions

Anonymous
Not applicable

Hi there,

We're looking to improve the touch performance of our products by moving from PCB electrodes to a dedicated touch film. Can anyone provide any references to info on how 2.4GHz RF is impacted by touch film? Specifically I'm wondering how much a full ITO matrix will degrade RF performance, assuming the touch surface is the only window in the product for RF. An alternative would be dedicated buttons, or using silver electrodes, but again, I'd like some info on the impact they have.

Thanks,

Tom

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1 Solution
Anonymous
Not applicable

Either you will need a window for the signal to propagate, or polarize both the ITO and the antenna to get signal transmittance through the ITO. The RF will radiate through the ITO, but due to the conductive nature of the ITO, it will drastically reduce the RF signal strength, and thus the range to practically nothing.

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9 Replies
Anonymous
Not applicable

Are you asking how the touch film would be affected by the RF? Or how the touch film will affect the RF emissions through it?

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Anonymous
Not applicable

How the touch film will affect the RF emissions through it.

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Anonymous
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Ah; Then @user_34122993 (Odissey) answered that question well

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I see only way to optimize ITO screen transmission if screen is polarized, e.g. the ITO electrodes or conducting wires are made as a parallel stripes. Such glass will transmit RF which electric field vector E is perpendicular to the stripes/wires, and block wave which E-vector is parallel to the wires. By rotating the antenna perpendicular to wires it would be possible to optimize transmission.

/odissey1

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Anonymous
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I believe elliot.tomcypress_2818321​ is intending to use a wireless chip with the ITO screen as the only window for external wireless communication, and is worried about lowered range on the wireless transmission. But polarizing the ITo would work if he wanted a percentage transmittance.

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Anonymous
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So it sounds like I shouldn't rely on the RF radiating through the ITO, but instead the best solution might be to design the touch ITO to have an aperture in it for the antenna to radiate through?

Thanks,

Tom

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Anonymous
Not applicable

Either you will need a window for the signal to propagate, or polarize both the ITO and the antenna to get signal transmittance through the ITO. The RF will radiate through the ITO, but due to the conductive nature of the ITO, it will drastically reduce the RF signal strength, and thus the range to practically nothing.

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Anonymous
Not applicable

Thanks for the answer.

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odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

I believe that ITO is quite conductive (~100 oHm/cm), so it should attenuate 2.4GHz dramatically. As an example, microwave oven glass is occasionally made ITO-protected, but still transmits ~20mW of 2.4GHz radiation from 400W oven.

/odissey1