Hi,

The followed picture is in kesight free software uncertainty caculator, from my point of view it should only be one curve to describe the receiver's dynamic accuracy, which the x-axis is the input signal to the receiver, for example -10dBm is the actual signal, the corresponding y is the accuracy which is 0.1dB, so this means the receiver's measured data is -10dBm±0.1dB. However why there are four curves (-10dBm at 1GHz, -20dBm at 1GHz……what are these dBm mean?)?

And can I measure this kind of Dynamic accuracy mag/pha curve in my own E8363B?

Best Regards

The notation dBm means "decibels referred to a milliwatt" or "decibels relative to a milliwatt".

Also note that 1milliwatt = 0dBm. Its a standard definition in RF design/analysis. If you say you have a -10dBm signal then you have a signal that is 10dB lower than 1mW. Likewise, for a +30dBm signal, you have a signal 30dB above 1mW. It is important to use correct +/- in front of numbers denoted with units of dBm. Also, most assume Zo=50ohms here but there are similar tables for 75ohms, etc.

You are given several curves because -10dBm is a bigger signal than -40dBm. This is a matter of signal/noise ratio and you need to know how well the equipment can discern a measurement. The uncertainty curves give you an indication of how much error you could be measuring with the DUT. The smaller amplitude the test port signal the larger the error. The curve also gives a sweet point of port power where you will get best uncertainty.

I would doubt that you could measure the stated accuracy. If you had a better VNA then maybe you could deduce it from various comparison measurements.