Highly Efficient Broadband Continuous Inverse Class-F Power Amplifier Design Using Modified Elliptic Low-Pass Filtering Matching Network

This paper proposes a design approach for a broadband and high-efficiency continuous inverse Class-F (CCF-1) power amplifier (PA) based on a modified elliptic low-pass filtering (LPF) matching network (MN). From theoretical and practical perspectives, the importance of a swift impedance transition from the higher end of the fundamental frequency band to the lower end of the second harmonic band is discussed, when designing a broadband single-mode PA. After being compared with widely used Chebyshev LPF MNs, a modified elliptic LPF MN, which provides a sharp roll-off, is utilized to provide the required rapid transition. A step-by-step design procedure of the proposed modified elliptic LPF MN is presented. Experimental results show that a high-efficiency CCF-1 PA is realized from 1.35 to 2.5 GHz (fractional bandwidth = 60%) with measured drain efficiency of 68%-82% and output power of 41.1-42.5 dBm. When stimulated by a 20-MHz LTE signal with an average output power of approximately 34.5 dBm, the proposed PA, combined with digital pre-distortion, achieved adjacent channel leakage ratios (ACLRs) below -45 dBc, with average efficiency (AE) ranging from 37% to 45.8%. Similar performance is measured when the proposed PA is driven by a dual-band dual-mode modulated signal with a 100-MHz instantaneous bandwidth at a center frequency of 2.14 GHz.