Design of High Efficiency Broadband Continuous Class-F Power Amplifier Using Real Frequency Technique With Finite Transmission Zero

Zhenxing Yang,Tian Li,Yao Yao,Mingyu Li,Zhongquan Liu,Zhijiang Dai

doi:10.1109/access.2018.2875010

Abstract

In this paper, a new methodology using a distributed ladder structure with finite transmission zero at finite frequencies is proposed for designing a broadband high-efficiency continuous Class-F (CCF) power amplifier (PA). The approach of realizing finite transmission zeros in Richard domain using Real Frequency Technique is first presented. By applying the proposed approach, the characteristics of the driving point impedance (DPI) of the proposed structure can be deduced and obtained in theory. Furthermore, the synthesis methods in Richard domain are extended to synthesize the DPI of the proposed structure. Four types of distributed elements are investigated to synthesize the DPI of the proposed structure. This proposed structure can improve the performance of the CCF PA when the bandwidth approaches an octave as the finite transmission zero can be used to control the second harmonic impedance of the lower frequency which is near the upper frequency of the operation band. To verify the validity of the proposed method, a broadband high-efficiency CCF PA working from 1.15 to 2.2 GHz is designed. Experimental results show that the fabricated PA achieves 11.3–13.7 dB power gain and 40.5–43.2 dBm output power in the operation band. And the PA has also achieved a high-efficiency characteristic of 70%–83% drain efficiency (DE) over the whole operation bandwidth.

Highlights

In modern wireless communication systems, power amplifiers (PAs) are the most energy consumption devices, and wider bandwidths and high-efficiency operation remains an important requirement for PAs
The results reveal that the PA has achieved greater than 70% drain efficiency (DE) with at least 40.5 dBm of output power over the 1.15–2.2GHz bandwidth
It should be noted that the operation frequency has a little deviation, which may be caused by the inaccurate model of the packaged transistors and the errors of fabrication

Summary

INTRODUCTION

In modern wireless communication systems, power amplifiers (PAs) are the most energy consumption devices, and wider bandwidths and high-efficiency operation remains an important requirement for PAs. A commensurate stepped-impedance transmission line was employed to design a broadband CCF PA in [26] and shunt stub elements optimized via RFT were employed for efficiency enhancement of PA in [27] and [28] In all these previous publications using RFT [17]–[29], only the method of impedance synthesis with transmission zeros at direct current (dc) and infinity are explored for the matching of the broadband PAs. In all these previous publications using RFT [17]–[29], only the method of impedance synthesis with transmission zeros at direct current (dc) and infinity are explored for the matching of the broadband PAs Such broadband matching technique run into difficulty when the bandwidth of interest approaches an octave, as the second harmonic impedance of lower frequency is close to the upper frequency of the band which is not easy to be properly treated.

LADDER NETWORK WITH TRANSMISSION ZEROS AT FINITE FREQUENCIES APPLYING RFT

REALIZATION OF BROADBAND TRANSFORMER

Findings

CONCLUSION