The large signal RF power transmission characteristics of an advanced InGaP HBT in an RF power amplifier are investigated and analyzed experimentally.The realistic RF powers reflected by the transistor,transmitted from the transistor and reflected by the load are investigated at small signal and large signal levels.The RF power multiple frequency components at the input and output ports are investigated at small signal and large signal levels,including their effects on RF power gain compression and nonlinearity.The results show that the RF power reflections are different between the output and input ports.At the input port the reflected power is not always proportional to input power level; at large power levels the reflected power becomes more serious than that at small signal levels,and there is a knee point at large power levels.The results also show the effects of the power multiple frequency components on RF amplification. The large signal RF power transmission characteristics of an advanced InGaP HBT in an RF power amplifier were investigated and analyzed experimentally. The realistic RF powers reflected by the transistor, transmitted from the transistor and reflected by the load are investigated at small signal and large signal levels The RF power multiple frequency components at the input and output ports are investigated at small signal and large signal levels, including their effects on RF power gain compression and nonlinearity. The results show that the RF power reflections are different between the output and input ports .At the input port the reflected power is not always proportional to input power level; at large power levels the reflected power becomes more serious than that at small signal levels, and there is a knee point at large power levels. The results also show the effects of the power multiple frequency components on RF amplification.