ST25RU3993-HPEV sensitivity

[Fma.1]

Hi,

We tested the receiving sensitivity of the RFID reader evaluation kit ST25RU3993-HPEV, and the actual measurement is -66dBm, but the sensitivity given in each document is -77dBm.

The sensitivity given here(-77dBm) is the sensitivity of the ST25RU3993 chip or the reader evaluation kit?

Thanks in advance.

[Bart Herse]

Dear Fma.1,

best would be to check if the tag is responding to the reader commands at a distance >4m as mentioned in my previous post.

Btw. what are the dimensions of the anechoic chamber you are testing in?

Cheers,

B

[Fma.1]

Hi Bart,

When the RX gain is 3dB and the distance between the tag and the reader is about 3.5m, the tag will respond briefly for about ten seconds, but when the distance is greater than 4m, the GUI displays no response.

The dimensions of the microwave anechoic chamber is about 8m*3m*3m.

Thanks,

Ma

[Bart Herse · Accepted solution]

Dear Fma.1,

thanks, I thing I understand the situation your are facing.

What I am trying to explain is that you should check if the tag is responding at distances >4 m.

I acknowledge that I have assumed that the concept how to do this was clear and therefore did not explain it in detail.

So while the reader is scanning for tags, place the tag at a distance >4m.

At the same time you could check with a second antenna, that is for instance connected to a spectrum analyzer, if a tag response is present.

You could check this in the frequency or in the time (zero-span) domain.

• If you see a tag response happening then it would mean the reader's sensitivity is to low.
• If there is no tag response and you see only the reader's modulated spectrum then the tag has most probably insufficient power to turn ON.

Your observation that at 3.5m the tag can be detected only for ten seconds might be an indication that the tag has insufficient power.

A possible explanation is that when the reader starts to operate (and the reader is cold), TX power is the highest.

When the reader continues to operate is gets warm the TX power drops a little bit.

Maybe at 3.5m the tag is marginally powered and just a bit less TX power shuts the tag OFF.

You could also place the tag at 3.5m and slightly reduce the TX power in the reader settings. If the tag is then never responding at all it indicates that TX power is responsible.

I hope this explanation was helpful to you.

Cheers,

B