Abstract
With the demands for high-speed data transmission, the millimeter-wave frequency band is developed because of its wider bandwidth. More and more applications are focused on this potential frequency band. In communication systems, modulation schemes are widely used for better data rates or other better performance. However, there is high peak-to-average ratio (PAPR) for modulated signal. So the output power back-off (OBO) is used to compensate linearity. In this operation mode, power-added-efficiency (PAE) is much more worse than before. It may shorten the lifetime of power amplifiers (PAs). In order to use PA more effectively, back-off PAE is the specification to be notify. Hence, Doherty PA has been developed till now. A 60 GHz Doherty PA with the combination of class AB PA and class C PA is purposed. The alternated structure of λ/4 transmission line is used to deal with load modulation for class AB PA and power combination for both PA. In order to achieve in-phase for combining path, phase compensation is also needed after the load modulation network and power combiner. Direct power divider is inserted for the input terminals of both PAs for equal power-division. The simulated 60 GHz Doherty PA achieves maximum PAE as 7.988 % at 8.674 dBm output power. 25.63 mW with DC consumption is needed to operate at this power level. At 4.988 dB back-off point, back-off PAE is 6.517 % with 13.79 mW DC consumption. From the measurement, the proposed 60 GHz Doherty PA shows an output back-off range of 2.5 dB. Back-off and peak PAE are 7.288 % and 7.89 %, respectively. PAE at 6 dB back-off is 3.64 %. P_L at peak PAE is 6.84 dBm.