ENERGY EFFICIENCY OF THE POWER AMPLIFIER ACCORDING TO W. DOHERTY’S SCHEME WITH AUTOMATIC POWER ADJUSTMENT

Abstract

At present, in relation to the power amplifiers of digital television broadcast transmitters, the scheme proposed by engineer William Dougherty for the construction of broadcast transmitters with amplitude modulation is widely used. W. Dougherty’s method, today is practically the only solution for improving the energy efficiency of OFDM signal power amplifiers, as applied to terrestrial digital television transmitters, when the wide band of the envelope of such a signal does not allow the construction of a transmitter based on a polar architecture. Transmitters for digital terrestrial television broadcasting using linear power amplifiers built on the basis of the W. Doherty method are developed and produced. When building transmitters for terrestrial digital television broadcasting, the problem of ensuring an acceptable efficiency of a linear power amplifier is very acute. The main reason for the low efficiency of such amplifiers is the high OFDM crest factor of the digital television radio signal. The problem of increasing the linear power amplifiers average efficiency of digital broadcasting transmitters is considered. The joint application of two methods for constructing high-efficiency linear power amplifiers is discussed: the method of William Dougherty and method of automatic power mode control. Preliminary assessment results of the energy gain from the combined use of these two methods, obtained by computer circuit simulation, are presented.