Fast Multi Harmonic Active Load-Pull

Övrigt konferensbidrag, 2012

A fast multi harmonic active load-pull setup is presented in this paper. The heart of the system is a large signal network analyzer (LSNA, Maury/NMDG MT4463). The LSNA measures the voltage and current time domain waveforms at the device terminals. The load reflection coefficient (ΓL(f)) is realized by injecting an amplitude and phase controlled signal at the wanted harmonic on the output of the transistor, according to: ΓL(f) = a2(f0)b2(f0)=A(VI, VQ)ej(ω0+θ(VI,VQ))b2(f0)(1) The speed of the system is significantly improved by using the LSNA in modulation mode. This allows for multiple impedance states to be presented during the measurement time of the LSNA. More than 180 impedance states can be measured within 21 ms. The sample clock of the LSNA and the vector modulators, controlling the load impedance, needs to be synchronized. A digital pattern generator (DPG) is therefore used in the setup to enable the synchronization, and also to trigger the start of the measurement. Furthermore, a new optimization algorithm is implemented to reduce the number of iterations needed to realize the desired load impedance. The optimization is based on the Newton-Raphson algorithm, and convergence is obtained within 3-5 iterations for one harmonic. The optimization is carried out simultaneously for all wanted harmonics, and multiple impedance states. This significantly reduce the total measurement time for multi harmonic load-pull measurements.