# Ultra-Generalized Continuous Class F Power Amplifier with Finite Third-Harmonic Load Impedance
###### Abstract  
This paper proposes the ultra\(-\)generalized continuous class F (UCCF) mode, which combines the influences of the drain current conduction angle and overdriven transistor on the drain current waveform to achieve a broader finite third-harmonic load impedance space. The UCCF mode uses \(\alpha\) to describe the magnitude of the drain current conduction angle and \(pcr\) to describe the drain current peak-clipped ratio. An analysis of the effects of \(pcr\) and \(\alpha\) on the linearity and efficiency of the UCCF model is presented, establishing a robust theoretical foundation for achieving a balance between these two characteristics. Additionally, an examination of how \(pcr\) and \(\alpha\) influence the load impedance design space is conducted, demonstrating that the UCCF mode not only offers a broader finite third-harmonic load impedance space but also expands the fundamental and second-harmonic load impedance design space. For practical validation, a PA with frequency of 2.05-2.65 GHz is designed based on CGH40010F. The test results show that \(S_{11}\) is less than \(-\)15 dB, the drain efficiency is 67.0-73.2%, and the output power is 40.1-41.0 dBm. The linearity is tested using a 5G NR (New Radio) signal with a bandwidth of 100 MHz and a peak-to-average power ratio of 8 dB at 2.35 GHz. The worst adjacent channel power ratio (ACPR) is \(-\)34.8 dBc without digital predistortion (DPD), and \(-\)57.8 dBe with DPD. An average output power (\(P_{ave}\)) of around 32.4 dBm and an average DE (\(D_{Euc}\)) of 34.39% were obtained. broadband; continuous class F mode; efficiency; finite third-harmonic load impedance; harmonic tuned (HT); linearity; wireless communications 2024132284.12284.12284.12284.12284.12284.12284.12284.12284.12284.12284.12284.122284.12284.  
especially at higher frequencies. In order to solve this problem, the recently proposed generalized continuous class F (GCCF) [26; 27; 28; 29] mode and peak-clipped current continuous class F (PCC-CF\({}_{3}\)) mode [30] use relatively large finite third-harmonic load impedance as a substitute for infinite third-harmonic load impedance. As described in [26; 27; 28; 29], the GCCF mode extends the drain current conduction angle of the continuous class F current waveform, thereby broadening the third-harmonic load impedance range. However, this diminishes the ratio between the current's fundamental component and the DC component, leading to a substantial decrease in efficiency. In [30], the PCC-CF\({}_{3}\) mode with a peak-clipped current generated by an overdriven transistor is proposed. Compared with the GCCF mode, the PCC-CF\({}_{3}\) mode has a broader finite third-harmonic load impedance and reduced efficiency degradation. However, in the PCC-CF\({}_{3}\) mode, the transistor works in a saturated state and therefore has nonlinear characteristics. Thus, in order to leverage the benefits of the GCCF and PCC-CF\({}_{3}\) modes and strike a balance between linearity and efficiency, we propose the ultra-generalized continuous class F (UCCF) mode. In the UCCF mode, two parameters, the drain current peak-clipped ratio \(pcr\) and the drain current conduction angle \(\alpha\) are used to reshape the drain current waveform at the same time, which can achieve a broader finite third-harmonic load impedance space. The UCCF mode comprehensively analyzes the variations in the efficiency and linearity with different combinations of \(pcr\) and \(\alpha\). This shows the UCCF mode can balance efficiency and linearity based on the premise of realizing finite third-harmonic load impedance. In addition, the UCCF mode provides a broader fundamental and second harmonic load impedance design space, thereby expanding the PA design freedom. The rest of this paper is organized as follows: In Section 2, the analysis begins with the gate input voltage waveform in the UCCF mode. Then, it examines the drain current waveform and the trends in drain current components with \(pcr\) and \(\alpha\) in the UCCF mode.