I'm working on a design using an NXP PN7150 NFC chip with PCB antenna. My initial prototype used their online tool for the antenna design, to generate the values for the matching network, however this is strictly for rectangular configurations. I wish to move to a circular (spiral) design due to some other design requirements. Is it simply a case of creating a spiral with the same overall length as the rectangle, with the same track size, spacing etc, or is there a tool I can use for spiral designs?
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1\$\begingroup\$ Please link to the data sheet of the driver chip and show an image of your square antenna. \$\endgroup\$– Andy akaCommented Nov 17, 2023 at 9:36
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\$\begingroup\$ Also if you could give us more info, what frequencies are you interested in, what bandwidth? \$\endgroup\$– Christianidis VasilisCommented Nov 17, 2023 at 10:54
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\$\begingroup\$ How do you feel about tuning the design, do you have opportunity to add/remove capacitors or does it need to be right the first time? \$\endgroup\$– Tim WilliamsCommented Nov 17, 2023 at 16:42
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\$\begingroup\$ It's an NFC antenna, with an ideal frequency response at 13.56Mhz. The online tool to design the antenna is here: community.nxp.com/t5/NFC/bd-p/nfc . The datasheet is here (although it won't help with the antenna design, as it simply references the online tool for this) nxp.com/docs/en/data-sheet/PN7150.pdf . The existing rectangular design is working well. I have extra tuning capacitor pads (I use mainly 0402 passives, but add 0804 pads for tuning caps so I can reflow/remove them easily to test) but they were not required for the initial design. \$\endgroup\$– Scott PorterCommented Dec 6, 2023 at 14:20
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Is it simply a case of creating a spiral with the same overall length as the rectangle, with the same track size, spacing etc
No, it will be kind of luck if that manages to work out. You might get close to the frequencies you want to by using that way though.
is there a tool I can use for spiral designs?
Not a fan of non-open source/free software but you can use Matlab, the last years they implemented PCB antenna design tools, (watch tutorial here)
Under the "Antenna design" app they feature spiral antennas.
They are still updating their antenna design libraries so make sure u got the latest year's matlab. The good thing about Matlab PCB antenna design is that its fast(er) to design your antenna on the PCB. For example other software(s) usually ask you to configure the offset of the heights of each layer because you have 3 axes (X,Y,Z) on your design. In matlab no height position offset needed, the layers are already on top of each other as you dont have a third axes, only (X,Y).
I used the PCB antenna design (in this ongoing project here) and the simulations are pretty accurate!
answered Nov 17, 2023 at 10:50
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\$\begingroup\$ But.... not having the Z dimension would reduce the accuracy of the designed antenna, surely? \$\endgroup\$– HearthCommented Nov 17, 2023 at 15:31
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1\$\begingroup\$ This is not actually the same kind of antenna; they appear to be two-element (spiral dipole) antennas, resonant/wideband, not a compact (electrically short) loop for NFC at 13.56MHz. Alternately, they would be absolutely massive (several m across). \$\endgroup\$ Commented Nov 17, 2023 at 16:41
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\$\begingroup\$ Thank you for the link to the Matlab tool. The antenna in your design looks massive, by the way! Is that deliberate? \$\endgroup\$ Commented Dec 6, 2023 at 14:26
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\$\begingroup\$ @ScottPorter Yeah, making the antenna smaller it would have reduced power emission for the frequency I am after. Its possible to make it larger or smaller. Also in my simulations it seemed the larger the GND aria the better the performance. youtu.be/9fYPQSuUQXc?si=1JVDG7mb4Tv8n7VR&t=147 \$\endgroup\$ Commented Dec 6, 2023 at 21:44