A 5.7-6.4GHz GaAs HBT Power Amplifier with a Gain Enhanced Bias Circuit

This paper describes the design of a 5.7-6.4GHz GaAs Heterojunction bipolar transistor (HBT) power amplifier for broadband wireless application such as wireless metropolitan area networks. A bias circuit is proposed which enhances the power gain and provides a good linearity. Using the wideband matching network techniques with trap circuits embedded to filter the harmonics and the diode-based linearizing techniques, a broadband power amplifier module was obtained which exhibited a gain above 28dB. This is about 1dB improvement compared with those normal bias circuits at a supply voltage of 5V in the frequency range of 5.7-6.4GHz, measured with Continuous wave(CW) signals. The saturated output power was greater than 33dBm in 5.7-6.4GHz and the output 1dB compression point was greater than 31dBm. The phase deviation was less than 5 degrees when the output power below 33dBm. The second and third order harmonic components were also less than -45dBc and -50dBc.