Design of concurrent multiband biasing networks for multiband RF power amplifiers

In this paper, a new technique for designing concurrent multiband biasing networks for multiband RF power amplifiers is presented. The proposed design technique can theoretically be applied for a large number of frequency bands. The biasing network (BN) is composed of a transmission line and high impedance quaterwave open stubs (QWOS) that are located at appropriate positions along the transmission line. Two tri-band BNs for 1.49 GHz, 2.15 GHz and 2.65 GHz frequencies were designed, fabricated and display very good performance with regard to the input impedance seen looking toward the BNs from the active devices, such as FETs, are approximately open for all three bands. For demonstration, a 10 W Class-AB tri-band power amplifier (PA) using the proposed technique was implemented, characterized and exhibits high output power of more than 40 dBm and maximum power added efficiency (PAE) of over 50 % in all the three bands.