Enquiry of UHF tag antenna design

Hi all,

I'm now designing a UHF tag antenna with inductively coupling. For UHF band, the operating range of frequency is from 908MHz ~ 914MHz. However, from my simulation result of return loss - frequency, I found out that the minium point of return loss was left shifted (around 820MHz). How can I improve my design so that the whole curve of return loss can be re-located inside the UHF band?

Please help me~Thanks a lot.

Best Regards,
Guillaume

How about scaling the dimensions?

Hi FvM,

Thanks for your suggestion. I had made an improvement after adjusting the dimension of patch. However, the diagram of return loss had an undesirable peak at the RHS of the frequency. What should I do to eliminate this peak?

Best Regards,
Guillaume

I wonder how you get a positive dB return loss. Is your antenna generating energy?
I'm not familiar to HFSS, but something seems to be wrong in your simulation setup.

The setting of my tag antenna:

-Substrate:
40(X) x 50(Y) x 1.6(Z) mm; FR4_epoxy
(The antenna is located at the middle of the vacuum box)

-Vacuum Box:
80(X) x 80(Y) x 50(Z) mm; vacuum

-LumpPort:
16 + j380 {because my chip impedance is 16 - j380 (chip cannot be changed!)}

(Any others please check the attachments~)

Please HELP~~