Analytical model and design of load modulated balanced amplifier
Aras, Yunus Erdem
Item Usage Stats
RF power ampliﬁers (PA) with high eﬃciency and linearity are in high demand for modern communication systems. Modulated signals having a high peakto-average power ratio (PAPR) require PA’s to maintain these features in the output-back-oﬀ (OBO) region. Since higher linearity always brings the trade-oﬀ in the form of lower eﬃciency, a PA having both high eﬃciency and linearity is challenging requirement for RF designers. Load modulation is one of the promising techniques oﬀering good eﬃciencylinearity trade-oﬀ under OBO conditions for conventional PAs. This work presents an analytical model for the load modulated balanced ampliﬁer (LMBA) using the recently introduced analytical non-linear model of a RF power transistor. We show that it is possible to predict the eﬃciency and nonlinearity of the LMBA reasonably well using this simple transistor model having only a small number of parameters. To test the performance of the analytical model, we designed an LMBA using three identical discrete RF transistors and 3-dB hybrid couplers. The model parameters of the 5-W GaAs PHEMT are determined from the I-V characteristics and load-pull measurements. LMBA works at 1.7 GHz with a peak output power of 37.5 dBm and with a peak eﬃciency of 53%. The eﬃciency is measured to be 47% at 6 dB output-back-oﬀ.
High-eﬃcient power ampliﬁer