Design considerations on wideband envelope termination for high efficiency RF power amplifiers

• Published in: Electronics letters Vol. 52; no. 6; pp. 460 - 462
• Main Authors: Chung, S, Ma, R, Teo, K.H
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 17.03.2016
• Subjects: AC‐terminated third‐order LC filter; average power efficiency; Bandwidth; bandwidth 150 MHz; bandwidth 80 MHz; class‐A RF PA; class‐B PA; Design analysis; design approach; efficiency 24.0 percent; efficiency 33.4 percent; envelope impedance bandwidth; envelope power loss; Envelopes; high‐efficiency RF PA; high‐efficiency RF power amplifiers; Impedance; inductor quality factor; LC circuits; LCF‐ET; LCF‐ET prototype; Long Term Evolution; loss 1.75 dB; LTE envelope signals; LTE‐advanced transmission; Microwave technology; normalised root‐mean‐square error; optimum ET topology; PAS; peak‐to‐average power ratio; Power amplifiers; Power loss; Q‐factor; radiofrequency power amplifiers; transistor output impedance; Wideband; wideband envelope termination; wideband ET; Q-factor; efficiency 24.0 percent; efficiency 33.4 percent; loss 1.75 dB; LCF-ET; transistor output impedance; LC circuits; power loss; optimum ET topology; wideband envelope termination; AC-terminated third-order LC filter; Long Term Evolution; LCF-ET prototype; class-B PA; class-A RF PA; wideband ET; LTE envelope signals; envelope impedance bandwidth; peak-to-average power ratio; envelope power loss; normalised root-mean-square error; bandwidth 80 MHz; inductor quality factor; high-efficiency RF power amplifiers; radiofrequency power amplifiers; LTE-advanced transmission; high-efficiency RF PA; bandwidth 150 MHz; design approach; average power efficiency
• ISSN: 0013-5194; 1350-911X; 1350-911X
• DOI: 10.1049/el.2015.4328

Design approach of wideband envelope termination (ET) for high efficiency RF power amplifiers (PAs) is discussed, considering power loss subject to design constraints including envelope bandwidth, inductor quality factor, and transistor output impedance. Analysis shows that the optimum ET topology depends on the design constraints. For LTE-advanced transmission with 80 MHz channel bandwidth, a novel wideband ET is designed using an AC-terminated third-order LC filter (LCF-ET), providing 3 dB envelope impedance bandwidth of 150 MHz. Measured results demonstrate 1.75 dB envelope power loss and −39.2 dB normalised root-mean-square error with the LTE envelope signals. For the LTE signal with 10.3 dB peak-to-average power ratio, the average power efficiency of an ideal Class-A RF PA with the LCF-ET prototype is calculated as 33.4% from the measured 1.75 dB envelope power loss, which exceeds 4.7% and 24.0% average power efficiency of conventional Class-A and Class-B PAs without ET.