Measurement Technique to Emulate Signal Coupling Between Power Amplifiers

Abstract

A measurement technique to emulate coupling between power amplifiers (PAs) such as that in an antenna array is presented. The case that the technique aims to emulate is referred to as the target array. The technique provides emulation of the distorted output signal for each PA under the coupling effect without the requirement for constructing the target physical coupling network or antenna array. Furthermore, given that the target array contains identical elements or PAs, transmitting either identical or different signals, the technique merely requires one PA as the device-under-test (DUT) to produce all output signals. The technique has direct connection to active load–pull, and aims to present the output of the DUT with corresponding time-varying impedances of each transmission path in the target array. The emulated output signals can then be analyzed, for example, in terms of adjacent channel power ratio, error vector magnitude, and normalized mean square error. Such measurement technique provides insight into the distortion and the impairment generated in the target array without the requirement to realize an actual array, and can be used, as an example, during the design stage of an array. The technique is theoretically motivated. The procedure is thoroughly described. The technique is experimentally demonstrated and verified under various usage cases and scenarios. Subsequent comparison to conventional active load–pull is provided.