Design, Implementation, and Evaluation of a Current Mode Class-D Power Amplifier

Abstract

In this thesis, the current mode class-D (CMCD) power amplifier (PA) is discussed in detail. The theory and principles of operation of this class of switching mode power amplifier (SMPA) are presented. Moreover, the advantages and limitations of the CMCD PA over the other SMPAs for high power, high frequency applications are investigated. There are different parameters that affect the CMCD performance. The effects of these parameters are studied through simulations. Finally, two CMCD PAs based on laterally diffused metal-oxide-semiconductor transistors (LDMOS) are designed, implemented and measured. The measurement results are in a good agreement with simulation results; providing that the implemented designs are properly tuned. A drain efficiency of 71% was achieved with an output power of 20.3 W and a gain of 15.1 dB at 1 GHz. To our knowledge, this result represents the highest efficiency for the CMCD PA and the highest gain for all SMPAs that have been reported for high power applications (output power of more than 7 W), at frequencies above 800 MHz. Moreover, a wide-band lumped-component balun has been used for the CMCD PA which enables significant size reduction of this class of PA for L-band applications.