access icon free A 65% efficient envelope tracking radio-frequency power amplifier for orthogonal frequency division multiplex

A high-efficiency radio-frequency (RF) power amplifier (PA) is described for high peak-to-average power ratio (PAPR) orthogonal frequency division multiplexed signals. Envelope tracking is used, where the supply voltage of an RF amplifier is modulated in harmony with the envelope of the RF signal. The envelope modulator is a split-frequency design composed of a switched mode power supply (SMPS) for the low-frequency content, and a hybrid amplifier for the high-frequency part. The hybrid amplifier combines digital switching with a linear amplifier in a transformer coupled push-pull structure. For verification, a 7 dB PAPR 3 MHz bandwidth 3rd generation partnership project long-term evolution (LTE) signal is used. When amplifying the AC component of the LTE envelope signal, 56.2% efficiency is achieved by the hybrid amplifier at 4.6 W output power into a 10 Ω load. Combined with a 94.4% efficient SMPS, the modulator can produce 23.4 W at 83% efficiency. This is combined with an 80.3% efficient 300 MHz RF PA. Together they achieved 65.6% DC-to-RF efficiency at 18.2 W RF output power. The measured PAPR at the amplifier output was 6.5 dB.

Inspec keywords: 3G mobile communication; telecommunication power supplies; telecommunication switching; transformers; radiofrequency power amplifiers; Long Term Evolution; OFDM modulation

Other keywords: envelope tracking radio-frequency power amplifier; high-efficiency radio-frequency power amplifier; 3rd generation partnership project long-term evolution signal; envelope modulator; peak-to-average power ratio orthogonal frequency division multiplexed signals; frequency 300 MHz; supply voltage; digital switching; switched mode power supply; transformer coupled push-pull structure; orthogonal frequency division multiplex; low-frequency content; PAPR; DC-to-RF efficiency; LTE envelope signal; split-frequency design; linear amplifier; hybrid amplifier

Subjects: Telecommunication power supplies; Amplifiers; Modulation and coding methods; Mobile radio systems; Inductors and transformers; Communication switching; Microwave circuits and devices

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