NFC Patch kit sensitivity

[PiotrParticipant]

Hi,
i just received NFC Patch Kit. Envelope containded two identical NFC Patches and flat cable to connect them. Shouldn’t it contain one NFC Patch and one NFC Antenna? In this configuration sensivity of NFC is so weak, that i have to place one patch in exact place on tablet back, and NFC tag has to be place flat on second patch without any distance. The same tag is readed by the same tablet (without kit) from distance of approx. 15mm.
Cheers,
Piotr

[RichardKeymaster]

Hey Piotr, you received the correct items. The latest revision of the NFC Patch Kit product replaced the 32mm NFC Antenna with just another patch as the antenna. This decision was based on the customer feedback we got that suggested that the bigger antenna size (56mm x 64mm) was more compelling. It also helps us keep manufacturing costs down as we can now fabricate patches and antennas as the same. In an effort to improve product mounting options, we moved to a different PCB material. The rigidity of the FR-4 material used in the original design was pealing off in the field on some curved NFC devices. By moving to a polyimide flexible material we were able to solve this problem. Because of how flex PCBs are made, a less conductive trace material had to be used. This added 22ohms of resistance to the original NFC Patch Kit design. Based on our stress tests we didn’t observer much of a sensitivity or performance impact:

NFC Test Tag               Stock NFC Patch Kit                 NFC Patch Kit w/ 100 ohm
Yellow Wristband               2cm                                                      2cm
Flomio Wristband              2cm                                                      2cm
NFCtags.com FOB             2.25cm                                                 2.25cm
Sticker Label                       2cm                                                       2cm
Zapp Business Card           1.75cm                                                 1.75cm
Round Business Card        2.5cm                                                   2.25cm
UL NFC Card                      5cm                                                       4.5cm
Sticker Card                        3.25cm                                                  3cm
AdvanIDe                            3.25cm                                                  3cm
Clone Small                         2.25cm                                                  2cm
Clone Large                         3.25cm                                                  3cm
Blank Label                         3.25cm                                                  2.5cm
Yellow Key FOB                 2cm                                                        2cm

It’s worth noting that the NFC Patch Kit product isn’t able to perfectly couple with all NFC devices. It’s been designed to best match with the Nexus 7 (2013) but even so isn’t 100% in it’s sensitivity transfer. This is likely the reason you’re not experiencing the same performance with the NFC Patch Kit as without. I would suggest you try repositioning the patch on the NFC reader such that it’s perfectly centered with the NFC antenna on the device. This will optimize the inductive coupling the NFC Patch Kit will be able to achieve.

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