A Quad-Band Doherty Power Amplifier Based on T-Section Coupled Lines

This letter proposes a new design technique for quad-band Doherty power amplifier (DPA) based on the T-section coupled lines network (TCLN). The TCLN allows for the design of a quad-band impedance inverter at three arbitrary frequencies and one associated frequency offering more flexibility in the design of quad-band DPAs than the state of the art. The ratio of the largest operating frequency to the smallest operating frequency is found in the range 1.95 to 7, as the ratio of the other two operating frequencies is located in the range of 1.3 to 2.76. A quad-band DPA is implemented with TCLN, operating at 0.73, 1.65, 2.67, and 3.57GHz. The measured results agree with the anticipation perfectly.