Study Of Class-E RF Power Amplifiers Employing SiC MESFETs

The rapid development of the wireless communication and microelectronic technologies demand higher performances of the radio frequency (RF) power amplifier (PA), including power, frequency, efficiency and temperature properties. As one type of the switching power amplifier, the ideal efficiency of Class-E power amplifier can reach 100%. The Metal-Semiconductor Field Effect Transistors (MESFET) fabricated with the third generation wide-band semiconductor materials of Silicon Carbide (SiC), is a perfect choice for designing Class-E power amplifiers due to its high breakdown voltage and low output capacitance.First, the large signal model of 4H-SiC MESFET is introduced in this paper. With the comparison of the measured results and simulated results, the accuracy of the modified Curtice-Cubic model is proved. By comparing the principles of classic power amplifier and switching power amplifier, it is concluded that the switching power amplifier has the advantage of higher efficiency. The principle and design parameters of Class-E power amplifier with parallel capacitance is discussed and analyzed. Then, by using techniques of unit elements, Kuroda's identity and Richard's transformation, a transmission-line Class-E power amplifier employing CRF24010 4H-SiC MESFET is designed. The proposed Class-E load network is composed of short-stub, which matches the optimum load resistance to the standard resistance and facilitates harmonic suppression of up to 5th order for maximum efficiency. The proposed power amplifier has been tested with Advanced Design System (ADS), the peak power added efficiency (PAE) of 70.5% with drain efficiency of 77.9%, output power of 42dBm and gain of 10dB are achieved at operating frequency 2.14GHz, drain bias voltage of 33V and gate bias voltage of -12.5V. Finally, based on analyzing the transistor parameters of 4H-SiC MESFET, such as on-state resistance, breakdown voltage, drain current fall time and drain-source capacitance, the power loss from SiC MESFET is analyzed, and it is proved that SiC MESFET is one of the best choice in Class-E mode.