VNA Dynamic Range And Linearity Accuracy

By Anritsu Company

Introduction

As Vector Network Analyzer (VNA) dynamic range requirements become more demanding, it becomes more important to better understand how receiver non-linear characteristics affect VNA calibrations and measurement accuracy. By identifying the problems and improving the understanding of receiver behavior while pushing the limits of dynamic range performance, one can better understand how to properly configure the system for maximum dynamic range while minimizing measurement uncertainty. At the heart of the discussion is the concept of receiver linearity and how it impacts calibration and measurement accuracy. While other papers describe in more detail the accuracy issues of non-linear calibration, this application note describes the practical aspects of configuring a VNA system for maximum dynamic range while limiting measurement uncertainty.

Defining Dynamic Range

System dynamic range of a VNA is defined as the difference between the measurement power available at the test port and the noise floor of the receiver. In situations where dynamic range is pushed to the limits, it is important to clearly understand the parameters of test port power and receiver capabilities. For example, test port power level is defined in a number of different ways. The power level is sometimes defined as the maximum power available from the source. It also is defined at the source test port power level when the receiver is at the 0.1 dB compression point. Furthermore, it may even be defined at some arbitrary value above the 0.1 dB compression point. And note that if the power level is defined for the maximum available power from the test set, there may be no assurance that the available power level is below the 0.1 dB compression point. Specifying at the 0.1 dB compression point is the most useful and practical method since it limits the linearity errors to a known value.