I. Introduction
During the past decade, the continuous-mode (CM) technique has been one of the most popular research topics for power amplifier (PA) designs, meeting the development requirements from broadband wireless communication systems. Several different continuous modes have been proposed to extend the PA design space, such as continuous class-B/J and class-F/F−1 [1], [2], [3], which makes it much easier to realize broadband PAs while maintaining high efficiency performance at the same time. As such an effective technique for bandwidth extension, the CM technique was then quickly introduced into more practical PA architectures used in wireless communication systems.