Op 10-2-2021 om 17:15 schreef Jim Lux:
On 2/10/21 7:36 AM, email@example.com wrote:I would do it in a different way. Calibrate the analyzer. Terminate port 2 in 50 Ohm. The noise floor is the lowest level you can measure. To get the dynamic range you would need to know the maximum signal that can be applied. Therefore you would need an RF amplifier (input to port 1). Do not overload port 2, but to find the maximum usuable signal, you must find the level where it is no longer linear. You can find this level bij adding a know attenuator in series with the amplifier output. S21 should follow the attenuation.I made some small changes of my Nanovna-H.S21 - start putting attenuators in and seeing where it bottoms out (or where the displayed attenuation change doesn't match the actual attenuation change)
S11 dynamic range: calibrate the VNA and do the 50 Ohm load as the last one. Leave it connected. Apply the calibration. Make sure you tell the analyzer (or the PC software) that the load is a perfect load. Now the displayed value of s11 is the dynamic range since it sees a perfect load, perfect in the sense that it is exactly the same as the reference.
For noise floor, take the peak values and add a few dB for safety margin. For S11 a dynamic range of 30 to 40 dB is enough for all practical applications.
All values are frequency dependent.
Note that a 20 dB attenuator does *not* mean a 40 dB return loss. Most likely it is less in practice if the input is not exactly 50 Ohm (or better, exactly the same as your reference)