A Linearized Calibration Technique Using Modulated Signals for Wideband Dual-Input Doherty Characterization

A linearized calibration technique for wideband characterization of high-efficiency multiple-input transmitter architectures, such as Chireix, outphasing and dual-input Doherty power amplifiers is presented. The proposed three step calibration process, including digital predistortion, is demonstrated for a dual-input setup and 400MHz of signal bandwidth at 3.6 GHz. Simultaneous use of three receivers allows drifts of the measurement setup to be detected in-situ, increasing the reliability of results and protecting vulnerable devices under tests. Destructive interference of 20-MHz and 400-MHz modulated signals at the output of a quadrature hybrid is used to verify the calibrated measurement setup, achieving signal power levels of -37.6 and -23.1 dBc, respectively.