Impedance and Sensitivity Measurement RFID IC

Hello everybody,

I′m measuring the impedance and the sensitivity of a RFID IC. First I was measuring the Impedance of the IC. After this step I was designing a matching network which transforms the 50 Ohms SMA-Connector to the Impedance of the IC.
The impedance matching of the IC with this matching network is great (measurement:s11<-30dB). Since the IC is fully passive and works with Energy Harvesting, the figure of merits is the sensitivity, how much input power is required for power up the IC.
Now the strange thing: The sensitivity is better with a matching network, which is not very well matched (s11 ~ -7dB). The difference is around 2dB.

Has anybody an idea, what could be a possible reason? I have really no idea.

Thanks a lot and best regards
Thorben

Do you mean the followings ?

Pin=A[dBm] for S11<-30dB
Pin=B[dBm] for S11~-7dB

B < A - 2dB

What condition do you apply in measuring S11 ?
If you use Vector Network Analyzer, what drive power do you set ?

S11 is dependent on input power to RFID IC.

So with Matching network B, the IC is starting with less output power coming from the Network Analyzer although the reflection factor is -7dB (not well matched)
With a theoretically better matching (s11 around -30dB) the required power level to start the IC is higher (around 2dB).

The IC is connected through a matching network (serial inductor, shunt capacitor) with an SMA connector to the network analyzer.
As output power for starting the IC -12 - 9 dBm are required.

Yes, the S11 depends at the working point, but the matching network is exactly designed for the starting point.

Thanks for your reply!

I can not understand what you want to mean at all.

What power level do you apply for measuring S11 ?

Consider steady state response not transient response.