A LOW DISTORTION AND HIGH-EFFICIENCY PARALLELED POWER-AMPLIFIER WITHOUT AN ISOLATOR IN WIDE-RANGE OF LOAD IMPEDANCES

Characteristics of a distortion, gain and efficiency of a power amplif ier grow worse extremely by different phases of the load reflection co efficient when load impedances of the power amplifier are far from 50 Omega. It was found that the value of the distortion, gain and efficie ncy showed the tradeoff behavior when the phase of the reflection coef ficient was different in 180 degrees. Therefore we have proposed new t wo- and four-parallel unit power amplifiers combined in 90 degree and 45 degree different phases each in order to accomplish low distortion and high efficiency in wide range of load impedances without an isolat or. We studied the power amplifiers by simulation based on experiments and realized an amplifier in that adjacent channel leakage power of p i/4-DQPSK modulation (for Japan's digital cellular system) is less tha n -45 dBc and efficiency is over 45% in range of load VSWR less than 3 .