Improved Reactance-Compensation Technique for the Design of Wideband Suboptimum Class-E Power Amplifiers

Abstract

A reactance-compensation technique has been introduced recently for the design of wideband class-E power amplifiers (PAs). With this technique, the load resistance can be transformed to an optimal complex drain impedance in a broad frequency band. One potential problem of this technique is that an additional network is often needed to transform 50 $\Omega$ to the optimum load resistance, which is typically at a lower value. This paper proposes a method to improve the reactance compensation technique. By using the proposed method, the required low-value load resistance is up to four times the original value. This is achieved not by adding more components, but by simply changing the order and values of them. With the proposed method, the additional resistance matching network is no longer needed in many cases, or can be significantly simplified in other cases. To validate the theory, two broadband class-E amplifiers were designed using the original technique and the proposed method, respectively. The performances of the two amplifiers are compared. By using similar complexity of matching networks, the PA designed using the original method can achieve better than 70% power-added efficiency for a fractional bandwidth of 42%. The PA designed using the proposed method can achieve above 70% efficiency for a bandwidth of 51%. The proposed method can be used in the design of many other types of amplifiers.