The high power and linearity performance of GaN-based HEMT for X-band application was achieved using the barrier layer of sandwich structure and Al0.05GaN back barrier. The AlGaN-sandwich-barrier can modulate polarization-graded field for more flat transconductance profile under the high drain bias. Only about 7.5% current collapse (CC) occurs for drain quiescent bias of 40 V. Due to the Al0.05GaN back barrier, the three-terminal off-state breakdown voltage (BVDS) of 260 V and a very small drain-induced barrier lowering (DIBL) of 2.7 mV V−1 is achieved. The AlGaN sandwich barrier combined with Al0.05GaN back barrier device exhibits a high current-gain cutoff frequency f  T of 42 GHz@V DS  =  10 V, and a high power-gain cutoff frequency f  MAX of 130 GHz@V DS  =  60 V. Load-pull measurement at 10 GHz revealed a saturated power density of 7.3 W mm−1 was achieved with an associated PAE of 29.2% and Gain of 10.6 dB. Two-tone measurement at 10 GHz showed an OIP3 of 38 dBm and a corresponding linearity figure-of-merit OIP3/P DC of 4.5 dB. These results demonstrate the great potential of AlGaN-sandwich -barrier/GaN/Al0.05GaN HEMTs as a very promising alternative to high power and high linearity X-band power amplifier.

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This paper presents the design procedure of a K-band 0.1 μm GaAs pseudomorphic high electron mobility transistors (pHEMT) monolithic microwave integrated circuit (MMIC) for satellite communication downlinks. The method focuses on the selection and design of the matching network (MN) by applying the Approximate Optimal Impedance Region (AOIR) approach which is a composition of simple mathematical constraints. The AOIR approach overcomes the drawbacks of traditional MN design method which cannot control the reflection coefficient trajectory of the MN precisely. The method formulates the constraints through symbolic-graphic combinations with integrated functions of computer-aided design (CAD) tools. The impedance transformation trajectory of MN is combined to reduce the mismatch and the insertion loss using equations with multiple mathematical constraints to realize the automatic selection of the MN's topology. The AOIR method fully considers the underutilized characteristics of power amplifier (PA) and to maximize its performance in a balanced manner. The MMIC, was designed using the proposed technique, operates in 18 GHz-23 GHz with a gain of 27 dB and has an average P −1 dB of 27 dBm and PAE of 38% under the continuous wave (CW) drive signal.

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