Simulating an RFID tag

[badlok]

Hi Jian,

What is the conjugate matched gain ? For my antenna design, the chip's impedance is 16-j380, hence I make the antenna's input impedance is 16+j380 to match (max. power transfer)

I don't know how to calculate the gain base on ie3d provided gain. I have calculated but the result seems wrong.......

Best Regards

 

[jian]

Hi, Badlok:

Conjugate Match Gain is a gain implemented in IE3D/PATTERNVIEW Version 11 and later for RFID designers. We noticed that RFIDc always have complex output impedances. Some people tried to use s-parameters normalized to complex Zc for such cases. We consider using complex Zc normalized s-parameters is an incorrect concept. As it is mentioned in some other thread, complex Zc normalized s-parameters may create |S| > 1 even for a passive structure. This is the problem caused by using complex Zc. Instead, users can do either of the following way:

1. Use some C or L to correct the output impedance to make it as Zouput = R + j X and X = 0. Then, you can use the R value for s-parameter normalization.

2. On IE3D 11, we implemented the conjugate match gain. We assume the antenna impedance Zin = R - j X while the RFID impedance is Zoutput = R + j X. Then, we also remove the mis-match portion of the loss in calculating the gain. Basically, it is the best gain you can achieve for the RFID with given Zoutput. It is available on IE3D/PATTERNVIEW 11 or later.

Best regards,

 

[badlok]

Dear Jian,

Thx for your reply, I also have some question about ie3d.

My IE3D is ver. 11, I don't know how to set up the conjugate match gain. In simulation set up window, I click box of the Radiation Pattern File then see my attachement. Is it a method of conjugate match gain?

If yes, how to set the value? My RFID chip is 16-j380 and my anteena's input impedance is designed to 16+j380

Thank once again for your kindly reply

Best Regards

 

[jian]

Hi, Badlok:

There is no setup for it. On the IE3D simulation, you just check to do the pattern calculation. After the simulation, IE3D will do the pattern calculation save save the .pat file. Then, it will invoke PATTERNVIEW to display the pattern for you. You just select the .pat file in the Pattern List. Select EDIT->Pattern Properties and it will tell you the Conjugate Match Gain (CM Gain) at each frequency. We have not implemented the display of CM Gain in graph yet. It is a good idea to display it in graphs. At this time, you can only find the values in the Pattern Properties dialog.

best regards,

 

[virtaul]

HI!!

If I simualte the RFID tag in HFSS, set up the port whose impedance is R and reduce jX with RLC lumped boundary, I observer the gain of pattern.

Are the method I use and result correct??
Do I consider the S parameter of the simulation in HFSS?

ruey

 

[navuho]

I observer the gain of pattern.

Look to this topic :

 

[badlok]

Hi Jian,
My RFID chip is 16-j380 and my anteena's input impedance is designed to 16+j380. How to know IE3D the Conjugate Match Gain is reference to my chip ??

For examplem, if I don't set up anything, just let IE3D do the pattern calculation, what does the Conjugate Match Gain mean??

Thank you for your kindly reply

Best Regard

---------------------------------------------------------------------------------------------

Hi, Badlok:

There is no setup for it. On the IE3D simulation, you just check to do the pattern calculation. After the simulation, IE3D will do the pattern calculation save save the .pat file. Then, it will invoke PATTERNVIEW to display the pattern for you. You just select the .pat file in the Pattern List. Select EDIT->Pattern Properties and it will tell you the Conjugate Match Gain (CM Gain) at each frequency. We have not implemented the display of CM Gain in graph yet. It is a good idea to display it in graphs. At this time, you can only find the values in the Pattern Properties dialog.

best regards,

 

[jian]

Hi, Badlok:

I checked it and it is Conjugate Match Efficiency (not gain). Howver, it means the same thing. It is not referencing to your chip's internal impedance. It is referencing to the antenna's input impedance.

From what I see, if your chip's internal impedance is 16-j380. You should try to optimize your antenna's input impedance to 16+j380. Then, you simulate your structure again. You can just use 50-ohm for the Zc of your port.

You will get 3 efficiency values while you display the pattern properties:

1. Radiation Efficiency
2. Antenna Efficiency
3. Conjugate Match Efficiency.

Basically,

Radiation_Efficiency = Radiated_Power / Net_Input_Power
Antenna_Efficiency = Radiated_Power / Incident_Power_50_Ohms
Conjugate_Match_Efficiency = Radiated_Power / ( Net_Input_Power + Power_consumed_in_source)

where
Net_Input_Power = Incident_Power_50_ohms - Reflected_power_50_ohms
At conjugate match, Power_consumed_in_source = Net_Input_Power (assuming Z_source = Conj( Z_antenna)). Therefore, Conjugate_Match_Efficiency = 50% of Radiation Efficiency.

On PATTERNVIEW of IE3D, we provide GAIN value. If you want to know the best gain you can achieve on your antenna, you should calculate it as:

GAIN_CONJUGATE_MATCH = GAIN * CONJUGATE_MATCH_EFFICIENCY / ANTENNA_EFFICIENCY (everything is in linear scale, not dB).

Best regards,


Regards.

 

[3dandyw]

HI,

i was looking for similar ap.
i got answer reading his app notes

www.flomerics.com/news/news_details.jsp?newsId=335 -
Modeling An RFID Tag Antenna With MicroStripes

I was impressed about simulation speed !
AW

 

[andrewmorcos]

hello,
i am new to RFIDs
and my thesis is to do an positionning system using RFIDs.. i need to simulate this system on CST MWS...
Anyone can give me some hints? thnak u