Measurement of the ramp linearity of extremely linear frequency ramps using a fractional dual loop structure

A dual loop synthesizer concept based on fractional divider techniques for measuring highly linear analog frequency ramps is presented. Due to the excellent sensitivity of the measurement set-up, relative nonlinearities as low as 10^-9 are ascertainable. The measurements obtained with a prototype circuit are shown. They illustrate the expected high sensitivity. Furthermore, a vector network analyzer (VNA) based on this dual loop synthesizer is described which allows for very fast measurements