In this paper a novel AM/AM and AM/PM power amplifier characterization technique is presented, exploiting signals interference properties. Key features of the proposed measurement technique are the simplicity, requiring basic scalar power measurements only, and the low cost of the utilized set-up; moreover, it allows a power amplifier distortion characterisation in a very short time if compared with a more conventional method utilizing a Vector Network Analyzer. A description of the measurement set-up used to perform AM/AM and AM/PM characterisation is given. Lastly,in order to validate the measurement technique, comparisons with vector network analyzer measurements, for a 2W,2GHz power amplifier, are reported.