VNA power source - any way to lower it?

Hi,

I am using the chip, RF2472, a LNA, and I am trying to determine its S-parameters. However, the problem that I am facing is that my S-parameter readings are extremely noisy. My guess is that it is being driven to saturation.

The company has mentioned that I should set my source power on my VNA to below -20dBm. However, the problem that I face now is that the only VNA(HP8510) I have access to in school can only go down to -10dBm, any lower and an warning message appears saying that "No IF can be found".

Is there any way around this?

Thanks in advance.

You can put an attenuator on the input of your amplifier and then back out the amplifier parameters from the measurements on the combination. This may cause some error, but your measurements taken now do you no good anyway.

HP8510 has internal attenuators at both ports. You can set
them at 10 dB and calibrate afterwards. That way your port
power will be -20 dBm, the VNA will be calibrated and the
extracted S parameters will be accurate.