Performance of SiC Microwave Transistors in Power Amplifiers
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1069-D10-05
Performance of SiC Microwave Transistors in Power Amplifiers S. Azam1, R. Jonsson2, E. Janzen1, and Q. Wahab1,2 1 Department of Physics, Chemistry and Biology (IFM), Linkaoping University, Linkaoping, 58183, Sweden 2 Swedish Defence Research Agency (FOI), Linkaoping, 58111, Sweden ABSTRACT The performance of SiC microwave power transistors is studied in fabricated class-AB power amplifiers and in physical simulations of class-C switching power amplifier using the physical structure of an enhanced version of previously fabricated and tested SiC MESFET. The results for pulse input in class-C at 1 GHz are; efficiency of 71.4 %, power density of 1.0 W/mm. The switching loss was 0.424 W/mm. The results for two class-AB power amplifiers are; the 30100 MHz amplifier showed 45.6 dBm (~ 36 W) output powers at P1dB, at 50 MHz. The power added efficiency (PAE) is 48 % together with 21 dB of power gain. The maximum output power at P1dB at 60 V drain bias and Vg= -8.5 V was 46.7 dBm (~47 W). The typical results obtained in 200-500 MHz amplifier are; at 60 V drain bias the P1dB is 43.85 dBm (24 W) except at 300 MHz where only 41.8 dBm was obtained. The maximum out put power was 44.15 dBm (26 W) at 500 MHz corresponding to a power density of 4.3 W/mm. The PAE @ P1dB [%] at 500 MHz is 66 %.
INTRODUCTION Due to superior physical properties of SiC such as high saturated carrier velocity, high thermal conductivity and high breakdown field, SiC transistors have the capability of high power density and due to high transistor impedance, making matching easier. These qualities have been applied in the development of different generations of power amplifiers for use in digital audio and video broadcasting [1], [2], aerospace and military systems [3], [4] and also in UHF broadband amplifiers [5], [6]. The high breakdown field makes them suited for higher operation voltage. SiC transistors offer high output impedance, while Si LDMOS and GaAs based devices offers lower output impedance, which is more complicated to match. An experiment analyzing memory effects in the IQ plane showed that SiC-MESFET has less to no memory effects compared to Si LDMOS devices [7]. In this paper we are presenting the performance of SiC microwave power transistors based on simulation and fabrication of class-AB power amplifiers using Advance Design System (ADS) Software. The switching response of an enhanced version of a physical structure of a previously fabricated and tested SiC MESFET [8] is studied using an active load-pull simulation technique [9] in TCAD. The performance of these amplifiers is comparable to other power amplifiers (PAs) reported in the recent literature [10], but we achieved with high power, PAE and gain for these particular frequency bands. The frequency range considered in this work is a part of our Power amplifier research work for EW-system.
RESULTS AND DISCUSSION A).
Measured results of fabricated 30-100 MHz class-AB power amplifier
This amplifier design is based on S-parameters of the transistor in ADS software. Power
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