Abstract. In this paper, a new combined electro-optic and pulsed nonlinear vector network analyzer-based load-pull measurement system for distributed multi-harmonic electric field measurements is presented. The system uses an external electrooptic probe to measure cross-frequency phase-coherent multiharmonic vector E-fields with an 8 µm spatial resolution and 20 MHz– 20 GHz bandwidth. We demonstrate the performance of the distributed phase-coherent E-field measurements of Ex, Ey and Ez components with 3 harmonics above a commercially available large periphery, packaged, laterally diffused metaloxide-semiconductor (LDMOS) transistor. The transistor was measured at 2.2 GHz under pulsed conditions with 10 µs pulse and 10 % duty cycle, while outputting 55.1 dBm of power. The measured electric fields of the operating transistor are animated for the first time and reveal complex non-uniform operation at harmonic frequencies.

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