METHOD FOR CALCULATING THE EFFICIENCY OF A PWM MODULATOR BASED ON GAN FET TRANSISTORS
S. E. Grychkin, A.M. Zakharov, Oleg V. Varlamov
Abstract
The task of creation a high efficiency powerful modulation path for Envelope Elimination and Restoration (EER) Power Amplifier does not lose its relevance due to the continuous increase in data rates and the associated expansion of the frequency bands used. Currently, it is promising to develop a modulation path suitable for use with a signal bandwidth of up to 100 kHz - 400 kHz. The currently actively developing digital radio broadcasting systems Digital Radio Mondiale DRM+ (100 kHz) and Real-time audio-visual information system RAVIS (100, 200 or 250 kHz) have such a signal bandwidth. The possibility of using signals with a frequency band of up to 100 kHz - 400 kHz in the HF range ionospheric channel is also being actively explored. This task at the power level of hundreds of watts can be solved using GaN FET transistors, which have begun to become commercially available. To design such devices, this article develops a method for calculating losses in a PWM modulator based on GaN FET transistors, its simulation is carried out and the analytical method of calculations is coordinated with the simulation results. It is shown that at a clock frequency of 1 MHz, the predominant loss component depends quadratically on the supply voltage. This makes it promising to use step switching of the supply voltage to increase the efficiency when amplifying signals with a large crest factor.