Question about UHF RFID antenna S11 values

[Techi]

Hi, I am designing the UHF RFID tag antenna in HFSS but the S11 of the antenna is (-30dB) at the desired frequency 915Mhz. Should I proceed with this S11?
Please guide me what it represents with lower S11, I mean whats the difference between the S11=-7dB and in other case if S11=-30dB?

 

[venu.gongal]

Re: UHF RFID antenna S11

S11 indicates the return loss..

It gives how much power is reflected back to the input..

So, S11=0 dB refers to all power reflected back to the input ( no power is being transmitted ), likewise S11 = -10dB refers to 1/10th of the power is reflected back.. and So on..

At ur frequency of interest complete power has to be transmitted.

So, the better the S11 the better is ur power transmission or radiation..

Thanks
venu

 

[Techi]

Re: UHF RFID antenna S11

S11 indicates the return loss..

It gives how much power is reflected back to the input......

So, the better the S11 the better is ur power transmission or radiation..

Thanks
venu

Thanks Venu, I have read in the book that S11 should be between -10dB and -15dB so that antenna should not be sensitive to environmental noises. What you say about such concerns?