[SI-LIST] Re: inductance, Q-factor of antenna for RFID tag
- From: axel stein <stein_axel@xxxxxxxxx>
- To: steve weir <weirsi@xxxxxxxxxx>, si-list <si-list@xxxxxxxxxxxxx>
- Date: Mon, 8 Jun 2009 07:33:22 -0700 (PDT)
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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