Mini-circuit ADE-1 mixer S11 Reflection coefficient measurement

The mini-circuit ADE-1 mixer is a diode-ring type passive mixer. As a +7dBm mixer work best at +7dBm of local oscillator input, or at least +4dBm to make it start working. It sounds like a quite huge power, so may be impedance matching is needed to optimize the efficiency of driving this mixer.  

How to do impedance matching? ok, may be we need to know the impedance of this particular component. As not very obviously showing in the picture, the IF and RF port of the mixer is connected to 50 ohm resistor for proper termination.The LO port is connected to the network analyzer for reflection coefficient measurement. Through a 1nF (-16j ohm@10MHz to -1.6j ohm@100MHz) capacitor in series.

The network analyzer is set to 10MHz to 100MHz, in -10dBm low power level, it have a quite high impedance(313ohm@10MHz) and a bit of capacitive (-22j ohm@10MHz).

In -5dBm power level, it's impedance is lowered.

In 0dBm, it's impedance is quite close to 50ohm

In +4dBm, even lower.

In +7dBm, even lower

In +10dBm, Well, it's quite hard to drive because impedance is quite low.