# Ultra-Generalized Continuous Class F Power Amplifier with Finite Third-Harmonic Load Impedance
## 3 Fabrication and Measurement Result of the Proposed UCCF Mode PA  
The UCCF mode enables a broader finite third-harmonic load impedance space and a better balance between efficiency and linearity. To verify this theory, the PA was designed based on CREE's CGH40010F GaN HEMT with an output power of 10 W and an optimal impedance of 30 \(\Omega\). The key issue when implementing the UCCF mode is the correct selection of \(pcr\) and \(\alpha\). When choosing \(pcr\) and \(\alpha\), it is necessary to comprehensively consider the efficiency and linearity. In this design, \(pcr\) and \(\alpha\) were selected according to the conditions listed in (19),  
\[\left\{ \begin{array}{c}\rm{AM/AM_{U}-AM/AM_{F}}\geq 0\\ \\ DE/DE_{0}\geq 0.9\\ \\ P_{out}/P_{0}\geq 1\end{array} \right. \tag{20}\]  
In Figure 8, the blue region indicates AM/AM\({}_{\rm U}-\)AM/AM\({}_{\rm F}\geq 0\), while the green region indicates \(DE/DE_{0}\geq 0.9\). The gray line in Figure 8 represents the contour line of \(I_{3}\). From Figure 7a, it can be observed that \(P_{out}/P_{0}\) is greater than 1 throughout the entire plot. When choosing \(pcr\) and \(\alpha\), it is necessary to ensure that they fall in the overlapping area, called the operating space in Figure 8, to achieve a balance between efficiency and linearity. A schematic of the PA with the drain bias voltage set to \(V_{DD}=28\) V and the quiescent drain current set to 265 mA is shown in Figure 9. Since the theoretical analysis is conducted in the current source plane, parasitic parameter models [33] are required to transform the packaging plane into the current source plane. In this design, \(\alpha\) equals \(1.17\pi\) and \(pcr\) ranges from 1 to 1.2. The corresponding impedance space is shown in Figure 10. The working state used in this design has enhanced linearity and acceptable efficiency. The impedance trajectory of this design, shown in Figure 10a, aligns with the impedance space. In Figure 10b, the simulated voltage and current waveforms of the current source plane are depicted and are consistent with the theoretical design. As shown in Figure 11, the stability factor is close to 1 and greater than 1 in 2-2.6 GHz, and the stability factor is greater than 1 in the whole frequency band, which proves that the designed PA has good stability. Figure 8: Operating space in PA design. Figure 10: (a) Intrinsic load trajectories. (b) Simulated voltage and current waveforms on the PA’s current source plane. Figure 9: Complete schematic of the PA design. As shown in Figure 12, the measurement setup includes a signal generator (SMW200A), a spectrum analyzer (FSW-43), two power supplies (E3632A, DP832A), a driver amplifier (ZHL-16W-43-S+PA), a DUT, an attenuator, and a PC. The layout design of the PA is shown in Figure 13, and the circuit size is 8.8 cm x 8.6 cm. A Rogers 4350B with a thickness of 20 mils and a dielectric constant of 3.66 was used as the substrate. As shown in Figure 14, S-parameters were measured at 2.05-2.65 GHz using an Agilent N5230C vector network analyzer. Figure 11: The stability curve of the proposed design. Figure 12: Measurement settings. The test results indicate that S\({}_{21}\) is greater than 14 dB, S\({}_{11}\) is less than \(-\)14 dB and S\({}_{22}\) is less than \(-\)12 dB. Figure 15a depicts the variations in the drain efficiency and gain with theooutput power, and Figure 15b depicts the variations in the drain output power, efficiency, and gain with the frequency. The results show that the drain efficiency was 67.0-73.2%, the output power was 40.1-41.0 dBm, and the gain was 9-10.8 dB. The DPD test platform is shown in Figure 12, which includes te signal generator, spectrum analyzer, power supplies, driver amplifier, PA, attenuator, and PC. A 5G NR (New Radio) signal with a 100 MHz bandwidth (the peak average power ratio was 8 dB) was used to test the PA's output spectrum at 2.35 GHz. The DPD in this paper adopts the GMP model and utilizes the indirect structure.