Meaning and measurement methods of effective system data of network analyzer

The effective system data characterizes the residual measurement error of the vector network analyzer after calibration. The effective system data index and the network analyzer transmission reflection measurement accuracy are two ways of expressing the same index. If the measurement error and uncertainty of the transmission and reflection measurements obtained through metrological verification meet the network analyzer index, there is no need to measure the effective system data.

For academic research or other purposes, effective system data can be decomposed and calculated from the measurement uncertainty, or it can be measured and calculated using the method described below.

The accurate and effective system data analysis method requires the use of the network analyzer's time domain test mode, using the time gate to obtain the frequency domain value of the relevant reflection peak, and decomposing it to obtain the effective system data. If there is no time domain option and calculation tool software, the ripple method can also be used, which is a simple estimation method for system data.

System effective data definition

Time domain measurement method for system effective data

1/Directivity/Source Matching and Reflection Tracking

2/Load matching

The two ports are directly connected, and S11 and S22 are directly measured, corresponding to the effective load matching in the forward and reverse directions respectively.

3/Transmission tracking

The two ports are directly connected, S21 and S12 are measured, and the ripples are smoothed and removed, corresponding to the effective transmission tracking in the forward and reverse directions respectively.

4/Reflection Tracking

At the port to be tested, such as port 1, connect the calibration device short circuit and open circuit to test S11, reflection tracking

Tr = (S11_Open+S11_Short)/2

System effective data ripple method measurement

When the network analyzer under test does not have the above time domain function, use air line plus load to measure directivity, and use air line plus short circuit to measure source matching. The specific methods are as follows:

Connect the air line and the load (or 20dB mismatcher) to the calibrated port under test. The S11 LinMag curve is as shown in the following figure. Read the peak-to-peak value Mp at the point where the ripple fluctuation is the largest.

Effective directivity = Mpp/2

Connect the air line and the short-circuit breaker to the calibrated port under test. The S11LinMag curve is as shown in the following figure. Read the peak-to-peak value Mpp at the maximum ripple fluctuation.

Source Match = Mpp/(2·Γs)