Users of Vector Network Analyzers (VNAs) often need to estimate and strive to optimize their instrument’s measurement speed. Many RF Engineers are interested in the tradeoffs between speed, accuracy and resolution in VNA measurements,especially those striving to achieve optimal automation of the instrument integrated in a larger measurement system or production environment. This application note details the determining factors for measurement cycle time in Copper Mountain Technologies VNAs.
Generally speaking, the measurement cycle for any VNA consists of three major components: the per-point tuning and settling time of the generator, the per point measurement time, and a per-sweep time needed to process and transfer results, switch the generator between output ports, and return the generator to the start frequency. An additional, user-programmable delay between points is available in CMT instruments, which may be useful for integration with external equipment or DUTs with settling times of their own.
As will be seen, some of the delay components are effectively fixed, while others depend upon the measurement parameters and thus may be optimized by the user.