GALLIUM NITRIDE BASED CLASS-D SWITCH MODE POWER AMPLIFIER

Abstract

Power Amplifiers (PAs) are the essential components of any communication system. PAs are generally used in the communication system to amplify modulated signal at Radio Frequency (RF). It has been observed that there is rapid growth of advanced wireless communication in last decade and it sets new areas for RF circuit designers. Wide bandwidth, high linearity and high efficiency are the essential requirements of any wireless communication system. In general, to reduce the power consumption in any circuit the efficiency has to be improved. PAs are the most power consuming component of any communication system so if the efficiency of PA is less then, the overall efficiency of any system will also reduce. High power consumption in any system will directly reduce the lifetime of batteries in portable devices. To increase the efficiency of PA, it should drive in saturation but linearity of PA reduces. Design of high efficiency switch mode Class-D PA has been discussed in this thesis. In Class-D operation of PA the active device is operated as a switch and this will increase the efficiency of PA. Load-pull technique is used to calculate the load impedances at fundamental frequency and its harmonics. A proper harmonic termination is used to reduce the power loss and increase the efficiency of PAs. At intrinsic plane of device, voltage and current waveform corresponding to Class-D behavior are maintained during the entire PA design. In order to validate the analysis, a current mode Class-D PA in push-pull configuration at 2 GHz frequency has been designed and fabricated. The fabricated PA has a drain efficiency of 71.5%, power added efficiency of 65.5%, gain of 11.1 dB and output power of 42.54 dBm.