Use of balun in ST25RU3993-HPEV design

[TNgo.1]

I am referring to the 2:1 balun T6 (BD0810J50100AHF) that transforms the incoming tag response to a 100 differential signal that is fed into ST25RU3993 receiver section at pins MIX_INP (pin 4) & MIX_INN (pin 6).

Based on the datasheet of the balun, it is a 50/100Ohm conversion, with < 1 dB Insertion Loss and phase difference of 1deg. Currently this balun is out of stock from major distributors.

As a result, I am currently looking for alternative balun to replace the chip. There are several with the same form factors, but the phase difference is not around 1deg. One particular example is B0310J50100AHF that has phase difference of 38 deg.

Hence, may I check if the phase difference affects the tag reading function of the RFID reader? In other words, whether the introduction of the phase difference at the 2 received signals MIX_INP and MIX_INN affects the tag reading responsiveness?

Thank you very much for your kind support.

Best regards,

Ngo Tung

[Bart Herse · Accepted solution]

Dear TNgo.1,

here's the response from our application team:

The actual phase difference of B0310J50100AHF at the target frequency is below 10 degrees.

The mixer design of the ST25RU3993 device is not very sensitive to phase balance, but for other reason listed below we do not recommend to use baluns with larger phase imbalances.

• Effective mixer input signal is appropriate smaller, as part is in common mode.
• Linearity measures are somewhat worse and sensitivity due to elevated reflected power will be worse.

An alternative balun is: B0430J50100AHF 

Cheers,

B

[TNgo.1]

Dear Bart Herse,

Appreciate your kind comments and suggestion.

Regards,

Tung