[SI-LIST] Re: inductance, Q-factor of antenna for RFID tag
- From: steve weir <weirsi@xxxxxxxxxx>
- To: axel stein <stein_axel@xxxxxxxxx>
- Date: Mon, 08 Jun 2009 07:44:44 -0700
Axel, how much do you need to increase the Q by?
Steve
axel stein wrote:
> Hi Steve,
> many thanks for your suggestions.
>
> For the first iteration of this project, we are fixed with the design / we
> can not move any lines. So the only parameters that I can change right now
> are:
> -line width, but keeping line-to-line (center-to-center) pitch constant, so
> spacing will move accordingly
> -copper thickness
> -material options, like your suggestion on adding a nickel ferrite or opening
> the soldermask
>
> By the way, the ratio of line width to copper thickness is close to 2:1.
>
>
> So considering the center-to-center spacing fixed and the relatively narrow
> trace (in comparison to the height), what options do I have?
>
>
> Thanks again for your valuable comments,
> axel
>
>
>
>
> ________________________________
> From: steve weir <weirsi@xxxxxxxxxx>
> To: axel stein <stein_axel@xxxxxxxxx>
> Cc: si-list@xxxxxxxxxxxxx
> Sent: Monday, June 8, 2009 1:07:36 PM
> Subject: Re: [SI-LIST] inductance, Q-factor of antenna for RFID tag
>
> axel, for a linear section of etch at frequencies commonly used by RFID tags,
> R and L track. R is skin limited, copper weight is not a factor until you
> get below 1/2oz. You should be able to increase Q by:
>
> Decrease R at operating frequency: Increasing line width while maintaining
> line to line spacing in the coil.
>
> Increase L: Decreasing line to line spacing while holding line width in the
> coil.
>
> Increase L: Redesign the coil for use with a material that has good Q at
> RFID frequencies on the backside of the circuit card, such as a high nickel
> ferrite.
>
> Depending on how many turns you already have, increasing the number will only
> have a limited effect on Q.
>
> You might get some gain by changing your surface finish and/or voiding solder
> mask in the antenna area.
>
> While a 3D tool will give an exact answer, a 2 or 2.5D tool can get you
> pretty close.
>
> Most of the RFID tag mfg's offer antenna design guidelines.
>
> Steve.
>
> axel stein wrote:
>
>> Hi all,
>> I am looking into increasing inductance and the Q factor of the antenna for
>> an RFID tag. The antenna is etched on a printed circuit board. The antenna
>> is a planar coil, the conductor is basically rectangular shape (some slight
>> taper at the edges) and the traces are wounded in a rectangular shape with
>> rounded edges.
>> For sure, increasing the number of windings will increase L. But how will L
>> and Q react, if I widen the lines (line-to-line pitch constant = reducing
>> spacing, keeping all other parameters constant, ) or if I increase the
>> copper thickness (perpendicular to the PCB surface).
>>
>> Unfortunately, I do not have a 3D solver that can help me answering these
>> questions. Anyone out there, that can give me some feedback?
>>
>> Thanks for your help,
>> axel
>>
>>
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>
>
> -- Steve Weir
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--
Steve Weir
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
California office
(866) 675-4630 Business
(707) 780-1951 Fax
Main office
(401) 284-1827 Business
(401) 284-1840 Fax
Oregon office
(503) 430-1065 Business
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http://www.teraspeed.com
This e-mail contains proprietary and confidential intellectual property of
Teraspeed Consulting Group LLC
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Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC
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