Figure 3

Figure 3 Output matching network.

A precise model of the parasitic network for the widely used CGH40010F transistor has been derived and reported by Tasker and Benedikt.12 Based on this parasitic network model, the impedance trajectories in the Smith chart at I-gen and at the package plane of the output matching network are shown in Figure 4. The derived fundamental impedances at the current plane across the operating band from 0.5 to 2.3 GHz are in or near the theoretic region.

Figure 4

Figure 4 Fundamental and harmonic impedances at the I-gen and package planes.

The final design of the resistive-reactive SCFM PA is shown in Figure 5. Simulated and measured results with a CW input power of 29 dBm are shown in Figure 6. A drain efficiency of 59 to 79 percent and saturated output power of 39.4 to 41.6 dBm are achieved across the band from 0.5 to 2.3 GHz. The measured results are consistent with the simulations.

Figure 5

Figure 5 PA schematic (a) and prototype (b).

Figure 6

Figure 6 Simulated vs. measured output power, efficiency and gain.

Figure 7

Figure 7 Measured average drain efficiency and ACLR with 20 MHz LTE signal.

To characterize linearity, a 20 MHz LTE signal with a peak-to-average power ratio of about 7.5 dB was used to drive the PA at 0.8, 1, 1.6 and 2 GHz. As shown in Figure 7, the broadband PA exhibits good linearity at about 5 dB back-off power, where the adjacent channel leakage power ratio (ACLR) is lower than −30 dBc, with 34.1 to 49.1 percent average efficiency. Table 1 compares the performance of this PA with other similar state-of-the-art broadband PAs.

CONCLUSION

The resistive-reactive SCFM design space was extended by introducing the third harmonic impedance. Using this methodology, the overlap between the fundamental and harmonic impedances was effectively solved, and a broadband high efficiency PA was designed, built and tested. The agreement between simulation and measurement demonstrates the validity of this approach for a multi-octave, high efficiency PA. Driven by 20 MHz LTE signals, the ACLR of the proposed PA is lower than −30 dBc at approximately 35 dBm output power, with average drain efficiency higher than 34 percent.

Acknowledgments

This research was supported by the Natural Science Foundation of China under grant 61501455, Natural Science Foundation of Beijing Municipality under grant 4162068 and National Defense and Technology Innovation Foundation of Chinese Academy of Sciences under grant CXJJ-16M124.

Table 1

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