Fully Integrated GaAs HBT MMIC Power Amplifier Modules for 2.5/3.5-GHz-Band WiMAX Applications

This paper describes two GaAs HBT MMIC power amplifier modules (PAs) for 2.5-GHz- and 3.5-GHz-band WiMAX applications. Each amplifier module integrates a fully 50-Omega input/output matched three-stage amplifier, a 0/20-dB step attenuator, an attenuator controller, and an RF detector together with all bias circuits, featuring on-module full integration. The step attenuator operating with high power handling capability, low-distortion, and low-bias current is placed between the first and second stages, thereby suppressing the change of the input return loss between thru and attenuation modes. With the 4.5 mm x 4.5 mm small-size module, optimized circuit design approaches lead to the following good measurement results under the 6-V supply voltage and WiMAX modulation (64QAM) test condition. The 2.5-GHz-band PA is capable of delivering a high gain (G
_p
) of over 31.9 dB, EVM of less than 2.1%, and PAE of more than 13.4% at a 28-dBm high output power (P
_out
). For the 3.5-GHz-band PA, a high G
_p
of over 28.1 dB, EVM of less than 2.4%, and PAE of over 11% are achieved at a P
_out
, of 28 dBm.