Design Of Linear Power Amplifier Based On InGaP/GaAs HBT Process

In order to improve the channel capacity,transmission rate and reliability,modern wireless communication system adopts OFDM?MIMO-OFDM and other technologies with high frequency spectrum utilization and strong anti-interference ability.The high PAPR of these technologies also brings higher linearity requirements to RF power amplifiers in communication systems.In order to transmit within the strict linearity specifications,PAs are forced to operate in a less efficient back-off region.This as well shortens the standby time of mobile communication equipment.As a key component of wireless communication system,RF power amplifier with high linearity and high efficiency has always been a hot and difficult topic in RF field.In this paper,a high efficiency and high linearity RF power amplifier chip with operating frequency of 815?915MHz is designed for LTE communication system by using InGaP/GaAsHBT process.The power amplifier improves the thermal stability of HBT transistor through adaptive bias circuit,adopts two tone Load/Source Pull to determine the optimal load/source impedance,and uses off chip design method for output matching network,which is realized by high-Q lumped elements,bond alloy wires and transmission lines on PCB substrate.The power amplifier was taped by AWSC's 2um InGaP/GaAsHBT.The test results show that the power gain of the power amplifier is greater than 29d B and the S₁₁ is less than-14 d B in the frequency range of 815?915 MHz;Under 10 MHz LTE modulation signals,the PA shows an output power of 28 d Bm,an UATA_ACLR1 less than-38.1d Bc,and an UATA_ACLR2 less than-44.8 d Bc,a power added efficiency is 35%?36%.Based on the summary and analysis of the power amplifier of Taped out,a high efficiency and high linearity class-J power amplifier with working frequency of 715?915MHz is designed.The power amplifier changes the time-domain voltage waveform through the J-Class output matching network to reduce the overlapping loss of voltage and current,so as to improve the power added efficiency;the nonlinear distortion of the power amplifier is suppressed by adding a linear compensator to improve the linearity.The simulation results show that in the frequency range of 715?915MHz,the gain of the power amplifier is between 35?36.5d B,the input and output reflection coefficient is less than-10d B,the saturated output power is 33dbm,the P1d B is about 31.5d Bm,the highest PAE point is 55%,and the third-order intermodulation coefficient IMD3 is-41d Bc and PAE is about 40%when the output power pout is back to 28dbm.The improved power amplifier has a great improvement in bandwidth,gain and efficiency.