Envelope Tracking Supply Modulator Research Articles

Design and Stability Analysis of the Variable-Sawtooth-Based PWM Controller for the AC-Coupled Envelope Tracking Supply Modulator

Design and Stability Analysis of the Variable-Sawtooth-Based PWM Controller for the AC-Coupled Envelope Tracking Supply Modulator

A 2.7 W AC-Coupled Hybrid Supply Modulator Achieving 200 MHz Envelope-Tracking Bandwidth for 5G New Radio Power Amplifier

Envelope tracking is an effective way to improve the efficiency of radio frequency power amplifiers (PAs). This paper presents a wideband hybrid envelope tracking supply modulator (ETSM) for 5G New Radio (NR) PAs. To reach a wide envelope tracking bandwidth of 200MHz while maintaining high power efficiency, this work utilized a linear amplifier (LA) with accurate frequency compensation and enhanced driving capability. The proposed low-pass sense and control (LPSC) circuit ensures that the switching power amplifier (SPM) only tracks the low-frequency components of the envelope to reduce the switching power loss. The proposed dual-path duty modulator regulates the voltage across the AC-coupling capacitor. This supply modulator circuit is designed and fabricated using 0.18μm BCD technology. When tracking 200MHz bandwidth envelope signals, the prototype ETSM achieves 78.5% efficiency at the output power of 2.7W when taking a realistic 4Ω//600pF load as the PA model.

Three-Level Hybrid Envelope Tracking Supply Modulator with High-Bandwidth Wide-Output-Swing

Envelope tracking is a dynamic supply modulation technique, which is mainly used to improve the efficiency of radio frequency power amplifier. For 5G NR mobile devices, this paper presents an envelope tracking supply modulator which is composed of a three-level switching converter and linear amplifier (LA) in parallel. The hysteresis control method is adopted in the supply modulator to improve the bandwidth of the switching converter and the loop response speed. At the same time, a rail-to-rail input-output class AB linear amplifier is designed to achieve a wide output swing and a super source follower is proposed to reduce the output impedance of LA. Designed with the 180 nm CMOS technology, the supply modulator operated at 5G NR 100 MHz envelope signal. The output power of the modulator reaches 1.5 W for a 6 Ω load resistor and the output swing is 4.3 V at 5.0 V supply, and the maximum efficiency reaches 85%.

An Energy Recycling Envelope Tracking Supply Modulator Assisted by Small Cap Replica With 89.7% Efficiency and 37% Reduced Linear Amplifier Current for 150 MHz Bandwidth 5G New Radio RF Applications

This article proposes an envelope tracking supply modulator (ETSM) that recycles the originally wasted energy in the linear amplifier (LA) to generate negative voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {NEG}}$ </tex-math></inline-formula> and achieve fast down tracking. With the insertion of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {NEG}}$ </tex-math></inline-formula> , the negative slope of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {BUCK}}$ </tex-math></inline-formula> becomes 25% larger. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {NEG}}$ </tex-math></inline-formula> is also used to boost the input voltage of buck converter from 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {BAT}}$ </tex-math></inline-formula> to 2.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {BAT}}$ </tex-math></inline-formula> and raise the positive slope of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {BUCK}}$ </tex-math></inline-formula> by 93%, which improves the transient response of buck converter and decreases <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert I_{\mathrm {LA}}\vert $ </tex-math></inline-formula> by 37%. With energy recycling and high-bandwidth LA replica, ETSM supports 150-MHz 5G new radio (5G NR) application and achieves 89.7% efficiency when output power is 3.7 W. In addition, the proposed differential feedforward technique controls the operation of energy recycling precisely with the calibration logic.

Envelope Tracking Supply Modulator with Trellis-Search-Based Switching and 160-MHz Capability

Envelope Tracking Supply Modulator with Trellis-Search-Based Switching and 160-MHz Capability

An Envelope Tracking Supply Modulator Utilizing a GaN-Based Integrated Four-Phase Switching Converter and Average Power Tracking-Based Switch Sizing With 85.7% Efficiency for 5G NR Power Amplifier

This article proposes a supply modulator (SM) that uses high switching frequency gallium-nitride (GaN) devices to achieve a four-phase fast step-down converter for the fast-tracking ability of the envelope tracking (ET). The ET signal is reshaped to generate an average power tracking (APT)-based signal to control the size of GaN switches to further increase light-load efficiency due to reduced switching loss. Moreover, a high-bandwidth and low-loss linear amplifier (LA) is used to supply the power amplifier (PA) to sufficiently provide fast-tracking speed for 5th generation (5G) NR ET. At a power of 3.5 W for 5G mobile phones, the peak efficiency that is tested with NR −130 MHz in the ET mode is as high as 85.7% over a wide load range.

A compact hybrid envelope tracking supply modulator with wide-band high-slew-rate linear amplifier

A compact hybrid envelope tracking supply modulator with wide-band high-slew-rate linear amplifier

2-Phase 3-Level ETSM With Mismatch-Free Duty Cycles Achieving 88.6% Peak Efficiency for a 20-MHz LTE RF Power Amplifier

This letter presents a 2-phase 3-level (2P3L) envelope tracking supply modulator (ETSM) for a long-term evolution 20 MHz (LTE20) radio frequency power amplifier as a solution for the ET system. This 2P3L ETSM that is composed of only switching converters achieves high efficiency, fast transient response, and a small output current ripple. To properly operate the proposed 2P3L ETSM, 4 pulse width modulatiop (PWM) signals with a 90° phase shift from each PWM signal are required without any mismatch between duty cycles. To remove the mismatch, a time-division multiplexing comparator and a duty-cycle calibrator are proposed. Thanks to the proposed techniques, the proposed ETSM fabricated in 0.18-μm CMOS achieved the highest peak dynamic efficiency of 88.6% with an LTE20 signal, which is superior to the state-of-the-art systems.

An asynchronous dual switch envelope tracking supply modulator with 86% efficiency

An asynchronous dual switch envelope tracking supply modulator with 86% efficiency

Wide-Bandwidth and High-Linearity Envelope- Tracking Front-End Module for LTE-A Carrier Aggregation Applications

The envelope-tracking front-end module (ETFEM) consisting of an envelope-tracking supply modulator (ETSM), a dual-power-mode power amplifier (PA), and a single-pole-double-throw (SPDT) switch is proposed for the Long-Term Evolution-Advanced (LTE-A) intraband carrier aggregation (CA) signal. The linear stage of ETSM is implemented by introducing the dual-path crossover current-reuse mechanism to obtain the measured efficiency 79.6%, 76.4%, 74%, and 72.8% for 7.4-, 9.6-, 11.2-, and 12.3-dB peak-to-average-power ratio (PAPR) 16-QAM LTE-A CA signals with $1 \times 20$ , $2 \times 20$ , $3 \times 20$ , and $4 \times 20$ MHz bandwidths, respectively. A SiGe BiCMOS dual-power-mode PA with two output power modes is realized and incorporated with ETSM to improve the adjacent channel leakage ratio (ACLR) by 11.7, 7.9, and 4.7 dB and the error vector magnitude (EVM) by 7.1%, 6.1%, and 4.1% at 26.8-, 24.3-, and 21.7-dBm output powers for the LTE-A 16-QAM signals with $1 \times 20$ , $2 \times 20$ , and $3 \times 20$ MHz bandwidths at 1.95 GHz, respectively. The SPDT switch integrated with ETSM provides 0.3-dB power loss reduction, 1.1-dB ACLR improvement, and 0.7% EVM enhancement at 12-dBm average input power. The ETFEM operated at 12.5-dB PAPR 64-QAM LTE-A CA signal with $4 \times 20$ MHz bandwidth demonstrates that the improvements of 1.3-dB ACLR and 1% EVM at 13.1-dBm output power are achieved for the wide-bandwidth and high-linearity FEM applications.

A High Slew-Rate Adaptive Biasing Hybrid Envelope Tracking Supply Modulator for LTE Applications

A linear-switch mode hybrid envelope tracking (ET) supply modulator utilizing adaptive biasing and gain enhanced current mirror operational transconductance amplifier (OTA) with class AB output stage in parallel with a switching regulator is presented. In comparison to a conventional OTA design with similar quiescent current consumption, proposed approach improves positive and negative slew rate from 50 to 93.4 V/ $\mu \text{s}$ and −87 to −152.5 V/ $\mu \text{s}$ , respectively, dc gain from 45 to 67 dB while consuming same amount of quiescent current. The proposed hybrid supply modulator achieves 83% peak efficiency, power-added efficiency (PAE) of 42.3% at 26.2 dBm for a 10-MHz 7.24-dB peak-to-average power ratio (PAPR) long-term evolution (LTE) signal and improves PAE by 8% at 6 dB back off from 26.2-dBm power amplifier (PA) output power with respect to fixed supply. With a 10-MHz 7.24-dB PAPR quadrature-phase shift keying LTE signal the ET PA system achieves adjacent channel leakage ratio (ACLR) of −37.7 dBc and error vector magnitude (EVM) of 4.5% at 26.2-dBm PA output power, while with a 10-MHz 8.15-dB PAPR 64QAM LTE signal the ET PA system achieves ACLR of −35.6 dBc and EVM of 6% at 26-dBm PA output power without digital predistortion. The proposed supply modulator core circuit occupies 1.1-mm2 die area, and is fabricated in a 0.18- $\mu \text{m}$ CMOS technology.

High-Performance CMOS Power Amplifier With Improved Envelope Tracking Supply Modulator

A differential cascode CMOS power amplifier (PA) with a supply modulator for envelope tracking (ET) has been implemented using 0.18- $\mu {\hbox{m}}$ RF CMOS technology. For maximizing the PA’s performance, the CMOS power cell has been optimized. The CMOS PA employs 2nd harmonic control circuits at the input, source, and output of the PA to improve efficiency and linearity at the same time. The CMOS PA utilizes an improved ET supply modulator, which is suitable for a CMOS PA with high knee voltage. By utilizing this modulator, we achieve not only higher linearity, but also higher efficiency in all power levels. For a long-term evolution signal at 1.70 GHz with a 10-MHz bandwidth and a 16-QAM 7.5-dB peak-to-average power ratio, the CMOS ET PA module achieves a power-added efficiency of 36.6%, an error vector magnitude of 3.0%, and an adjacent channel leakage ratio of $-{\hbox{35.6}}~{\hbox{dBc}}$ at an average output power of 28.5 dBm. The proposed ET operation reduces the total current consumption over the standalone PA, by 10% at the peak power and up to 56% at a low power.

Design of an Advanced CMOS Power Amplifier

The CMOS power amplifier (PA) is a promising solution for highly-integrated transmitters in a single chip. However, the implementation of PAs using the CMOS process is a major challenge because of the inferior characteristics of CMOS devices. This paper focuses on improvements to the efficiency and linearity of CMOS PAs for modern wireless communication systems incorporating high peak-to-average ratio signals. Additionally, an envelope tracking supply modulator is applied to the CMOS PA for further performance improvement. The first approach is enhancing the efficiency by waveform engineering. In the second approach, linearization using adaptive bias circuit and harmonic control for wideband signals is performed. In the third approach, a CMOS PA with dynamic auxiliary circuits is employed in an optimized envelope tracking (ET) operation. Using the proposed techniques, a fully integrated CMOS ET PA achieves competitive performance, suitable for employment in a real system.