A Dual‐Band Continuous Class‐F Power Amplifier Using a Series Couple Lines Structure

ABSTRACT This paper presents an innovative method to design a dual‐band high‐efficiency power amplifier (PA). A novel series couple line structure that consists of a pair of open couple lines connected in series with two terminated transmission lines is proposed. The proposed structure has an input impedance that varies periodically with frequency. The combination of the impedance frequency periodic characteristics of the proposed structure and the continuous class‐F broadband characteristics generates a dual band with a certain bandwidth at each adjustable ratio of dual frequencies. In addition, the proposed theoretical strategy is modified to absorb the transistor's packaging parameters, which leads to more universal and practical solutions. Meanwhile, by appropriately setting the second harmonic impedance of the target frequency band, high efficiency is achieved in the dual‐band without the need for additional harmonic control. For validation, a dual‐band PA is designed and fabricated. Measurements exhibit an output power of 41.2–42.1 and 41.4–41.7 dBm in the frequency bands of 2.2–2.4 and 3.5–3.7 GHz, respectively. Meanwhile, the measured peak drain efficiency is 80.2% and 80.8% within the same frequency bands.