An improved coupling method for time domain load-pull measurements

This paper describes an efficient coupling method improving the nonlinear time domain large signal load-pull measurements of active devices. This approach consists in a small RF loop fixed near the blended line that takes place between the DUT and the tuner. We take benefit of two advantages: extremely low losses induced by the coupler, and measurements taken very close to the DUT plane. It is shown that this simple coupling solution offers an absolute directivity better than 13 dB (before calibration) along a wide RF band from 1 GHz to 17 GHz, and better than 10 dB between 17 GHz and 18 GHz. This solution is compared with the classical approach of a distributed coupler connected before and after the tuner. A LSNA has been performed, it exhibits an average directivity better than 35 dB.