A fully calibrated NVNA set-up for linearity characterization of RF power devices using Unequally Spaced Multi-Tone signal through IM3 & IM5 measurements

This paper presents an innovative experimental method and its associated test bench for assessing the in-band linearity degradation of radiofrequency and microwave power devices, suitable both for on-wafer and connectorized characterization. The Unequally Spaced Multi-Tone (USMT) signal is a tailored signal which presents flexible characteristics depending on the number of pilot tones (e.g. Peak to average radio, IQ enveloppe, and Radiofrequency bandwidth). It behaves like a complex modulation signal with particularity to have a complete separation of pilot tones, IM3 and IM5 and it was used for linearity measurements. The method has been used up to 28 MHz RF Bandwidth on a VNA with the spectrum option (PNA-L from Keysight Technologies). The USMT set-up enables very fast measurements. In only one acquisition, simultaneous criteria are evaluated, like output power, gain, Power Added Efficiency (PAE), in-band degradation such as Carrier to Intermodulation ratio (C/I) induced by the device, by measuring the USMT signal at the input and output ports of the DUT. This novel approach has been validated through the linearity characterization of a commercial power amplifier.