High Efficiency Power Amplifier And Its Linear

The class E power amplifier is a high efficient power amplifier; designing a class E power amplifier using LDMOS transistor can save the cost. The class E power amplifier needs to overcome poor linearity for communication application. The polar transmitter makes use of drain linearity of the class E power amplifier properly. There are still two questions needed to be answered for LDMOS class E power amplifier's communication application: compensation for parasitic components of LDMOS transistors and using of drain linearity. Use a stepwise research approach: first discuss the features of ideal class E power amplifier, then investigate the method of approximating an ideal class E power amplifier using a LDMOS transistor, last study the question of improving linearity of a class E power amplifier by a polar transmitter. The main results are as follows:1. Performances of ideal class E power amplifier are investigated in detailed. Comparation of class E and linear power amplifier is made; the simulation of linearity of ideal class E power amplifier is performed.2. Parasitic components of LDMOS transistors are analyzed and calculated. A 1.5 GHz LDMOS power amplifier with parasitic compensation network is designed; it has 67.1% efficiency, good drain amplitude linearity and good approximation of the ideal class E power amplifier. So it's suitable for polar transmitters.3. Supply modulator is studied using simplified model, Mathematical analysis of the effect of delay on polar transmitter is made. Simulation platform of polar transmitter using ADS is built with the following results: A polar transmitter with a LDMOS class E power amplifier has 23 dB better ACLR than a single class E power amplifier, and has 9 dB worse ACLR than a polar transmitter with an ideal class E power amplifier. 11 delays make ACLR of a polar transmitter degenerate 19.9 dB, Supply modulator is 10 MHz limited bandwidth make ACLR of a polar transmitter 32.5 dB worse.