I would like to have an NFC/RFID reader with a screen around 7", where one could tap the card anywhere on the screen to have it detected/read.
I do not need to know where the card was placed (contrary to this question for instance), just detect/read the card anywhere on the screen.
I understand there are such antennas for smaller screens, like Pulse Electronic's W7002, but it's only suitable for screens up to 5 x 7 cm (about 3 inches).
What are the possible issues with a larger antenna surrounding a 7" screen? It would be about 160 x 70 mm.
My understanding is that optimal communication between the reader and tag occur when the two antennas have roughly the same size. Here the target tag is a standard Mifare card, so the antenna is usually roughly 75 x 45 mm.
Some of the questions/answers such as this one focus on getting a larger range (distance between antenna and tag) by expanding the size of the antenna, but in my case, I'm more interesting in increasing the area rather than the distance.
Another issue I wonder about, is what would be the effect of the presence of the screen in the same plane as the antenna? Since this is going to be a touch screen, the screen should should be just below the touch panel glass, so the antenna will be in the same plane. Would having a ferrite "ring" around the screen (between the screen and the antenna) be useful?
Alternatives could be:
Placing the antenna behind the screen, but many (most?) screens have a metal shielding on the back, so this would probably be ineffective. Even without shielding, I believe backlights often have a reflective surface at the back to avoid "losing" any light, which is probably metallic as well?
Placing lots of small antennas all around the screen, though I'm not sure one would reach the center of the 7" screen this way, and opens up a lot of issues like switching between readers/antennas so only one at a time is running
Using Sharp's transparent antenna method, but this is probably a bit out of reach, not to mention patented, and Sharp's NFC-enabled screens to not seem to be on the market yet.
Any feedback or ideas welcome!
