A Highly Efficient Combined Power Amplifier with Branch-line Couplers

In this work, a combined power amplifier (PA) using branch-line couplers is designed over 3.4-3.8GHz covering 11% fractional bandwidth. The proposed power amplifier consists of a 5dB input coupler for input power splitting, a 10W amplifier, a 25W amplifier and a 6dB output coupler for power combination. The input matching networks and output matching networks of two harmonic-tuned mode sub-PAs are designed by using stepped-impedance matching network topology. The measured combined power amplifier shows 65%-70% drain efficiency at 46.1-46.5 dBm saturated output power, and the small signal gain is more than 10dB.