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Lumped Port Matching for UHF RFID Tag Antenna.

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sr2w

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I am using a lumped port.

To simulate RFID IC of impedance 27 - 200j,

I have set these values in the Full Port Impedance box for the lumped port.

Then I am checking the Z parameters and S11, the place where S11 is the least(approx -20 dB), I get the least value in the im(Z) plot.

Doesn't HFSS follow conjugate matching?

If yes where is my analysis going wrong?

Can someone please explain how the below plots

1.JPG

2.JPG

3.JPG

are correct?
 

What will be better : Perfect Matching or Conjugate matching for UHF RFID tag antenna

We want to increase the read range of the tag. Thus should we go for Perfect Matching or Conjugate Matching? The impedance of chip around 27 - 200j. Should we design the tag antenna to of input impedance 27 - 200j or 27 + 200j?
 

If you set the Characteristic Impedance as Input Impedance of the RFID IC in HFSS simulation set-up and you have found S11=-16dB, Antenna Impedance is approx. conjugate of Input Impedance of the RFIC IC.
What else you are expecting ??? Have I misunderstood something ??
 

BigBoss said:
If you set the Characteristic Impedance as Input Impedance of the RFID IC in HFSS simulation set-up and you have found S11=-16dB, Antenna Impedance is approx. conjugate of Input Impedance of the RFIC IC.
What else you are expecting ??? Have I misunderstood something ??
Click to expand...

When I go - Results -> Create Model Solution Data Report -> Rectangular Plot -> Z parameter -> re or im,
this plot shows the input impedance of the antenna right?

You can see the Im(Z) plot, there I don't see the Impedance to be conjugate of -200j i.e. 200j at the best S11 data, whereas the impedance that I see is near -200j, which isn't conjugate matching Zs=Zl*(max. power transfer), but perfect matching, where Zs=Zl(min. reflections).

One more question - Should I go for conjugate matching or perfect matching to get max. read range for passive rfid tag antenna?
 

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