S11 Measurement Results

Projects LimeSDR
1

Dear All,
I have made S11 measurements with a LIMESDR-USB.
The measurements were made on:
Rx1_L (with Easyfix2 applied)
TX1_1
in the frequency range of 10 -2000 MHz

This is the measurement taken on Rx1_L, I was on the impression thar Easyfix2 will also improve VSWR but clearly this is not the case. S11 at 70 MHz is a whopping -0.84 dB!!! (That means a loss above 7 dB)

rx_s11
rx_s112304×1120 527 KB

and here you see the measurement taken on Tx1_1. (Note there is a 70 MHz filter attached)

tx_s11
tx_s111329×865 369 KB

I would like to optimize the matching circuits for TX and RX under 100 MHz but the matching circuits are differential which I am not used to.
Which SW can you recommend for fine tuning the values in the matching circuit.

Thank you in advance.

2

If you display S11 as a Smith Chart, you can see the complex impedance at whatever frequency interests you. You then add whatever capacitance or inductance is necessary to bring it to R+j0.