Millimeter-wave Broadband Amplifier using MHEMT

In this paper, millimeter-wave broadband cascode amplifiers were designed and fabricated. The 0.1 mum InGaAs/InAlAs/GaAs MHEMT (metamorphic high electron mobility transistor) was fabricated for the cascode amplifier. The DC characteristics of MHEMT are 670 mA/mm of drain current density, 688 mS/mm of maximum transconductance. The current gain cut-off frequency (f_T) is 139 GHz and the maximum oscillation frequency (f_max) is 266 GHz. To prevent oscillation of the designed cascode amplifiers, a parallel resistor and capacitor were connected to the drain of common gate device. By using the CPW (coplanar wave guide) transmission line, the cascode amplifier was designed and matched for the broadband characteristics. The designed amplifier was fabricated by the standard MHEMT MMIC (millimeter-wave monolithic IC) process that was developed through this research. As the results of measurement, the amplifier was obtained 3 dB bandwidth of 50.37 GHz from 20.76 to 71.13 GHz. Also, the amplifier represents the S₂₁ gain with the average 7.07 dB in bandwidth and the maximum gain of 10.3 dB at 30 GHz.