| In the wireless communication system, the base station power amplifier requirementsare increasing highly, the PA performance directly determines the performance of the basestation good or bad. This stage, the radio communication system in order to be able totransmit more data in a more narrow band and use complex modulation scheme, such asOFDM modulation scheme. The peak-to-average ratios in the envelope transform in thewireless communication system, the transmission signal (the LTE peak-to-average ratiois7.5), and the bandwidth occupied width of these modulation methods have a very strictrequirements on the linearity of the power amplifier, because the input signal using thesemodulation methods, have a wide input range. The LTE peak-to-average ratio are relativelylarge, the use of non-constant envelope modulation, obviously difficult to meet theefficiency requirements of the base station to the use of traditional power back-offapproach to designing a power amplifier. Power back-off is not only low efficiency, whichwill bring the base station cooling problem, the system will bring the hidden dangers ofinstability. Doherty power amplifier due to the high efficiency and good linearity becomemainstream communications equipment manufacturers design trend in recent years.This design input LTE signal used in the amplifier, adopt Freescale MRFE6S9060amplifier tube, structure design a Doherty power amplifier. The amplifier has theadvantages of high efficiency, high linearity. ADS simulation software in the design is used,in order to select the best amplifier tube to get load impedance value and source impedancevalue. Using load pull and source traction simulation. To match the impedance of thecircuit with the simulation software to optimize the matching circuit. Rational design ofgate voltage bias circuit,selecting suitable quiescent operating point for the Dohertyamplifier and matching the micro strip impedance line amplifier output network. Finally,the indicators of the power amplifier are tested, verify its excellent performance. |
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