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High efficiency digital GaN MMIC power amplifiers for future switch-mode based mobile communication systems

: Maroldt, S.; Haupt, C.; Kiefer, R.; Bronner, W.; Müller, S.; Benz, W.; Quay, R.; Ambacher, O.


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE Compound Semiconductor Integrated Circuit Symposium, CSICS 2009 : October 11-14, 2009, Greensboro, NC, USA
Piscataway/NJ: IEEE, 2009
ISBN: 978-1-4244-5260-6
ISBN: 978-1-4244-5191-3
Compound Semiconductor Integrated Circuit Symposium (CSICS) <31, 2009, Greensboro/NC>
Fraunhofer IAF ()
GaN; high electron mobility transistor; HEMT; monolithic microwave integrated circuit; MMIC; switchmode amplifier; class-D; class-S; mobile communication

A high efficiency digital MMIC amplifier for mobile communication switch-mode concepts was designed by utilizing a 0.25 µm GaN HEMT technology with fT of 32 GHz. A comparative investigation of two different driver concepts for a 1.2 mm GaN HEMT PA is shown. The MMICs were on-wafer evaluated for class-D and class-S operation. A drain efficiency of 70% for an output power of 4.4 W for a band pass delta-sigma (BPDS) class-S input signal at a bit rate of 3.6 Gbps equivalent to a 0.9 GHz fundamental was obtained. For the first time the operating mode up to 8 Gbps (2 GHz) is shown with an efficiency of 62%, demonstrating the prospect of future use of GaN HEMTs for switch mode amplifier concepts.