Envelope Tracking RF Power Amplifiers Research Articles

A Digital Linear-Switching Hybrid Power Amplifier for Envelope Tracking Hybrid Supply Modulators

A novel envelope modulator for envelope tracking RF power amplifier (PA) is presented in this paper. The proposed modulator consists of a parallel combination of analog class AB and digitally controlled hybrid PAs. The analog and digital class AB PAs are effective in both reducing the clock frequency and also static power dissipation, thus improving the efficiency of the modulator. On the other hand, lower clock frequencies result in simpler and more power-efficient digital to analog converters required in the architecture. The modulator digital block is evaluated with a 45[Formula: see text]nm CMOS technology. The overall power consumption of the digital block is around 76[Formula: see text]mW at 800[Formula: see text]MHz clock frequency. As an application, the designed digital block is incorporated in a complete envelope modulator architecture. The overall efficiency of the modulator, including the digital block power consumption, is around 80.7% at an average 32[Formula: see text]dBm output power for a 5[Formula: see text]MHz input signal.

An All-Digital Fast Tracking Switching Converter with a Programmable Order Loop Controller for Envelope Tracking RF Power Amplifiers.

This paper presents a step down, switched mode power converter for use in multi-standard envelope tracking radio frequency power amplifiers (RFPA). The converter is based on a programmable order sigma delta modulator that can be configured to operate with either 1st, 2nd, 3rd or 4th order loop filters, eliminating the need for a bulky passive output filter. Output ripple, sideband noise and spectral emission requirements of different wireless standards can be met by configuring the modulator's filter order and converter's sampling frequency. The proposed converter is entirely digital and is implemented in 14nm bulk CMOS process for post layout verification. For an input voltage of 3.3V, the converter's output can be regulated to any voltage level from 0.5V to 2.5V, at a nominal switching frequency of 150MHz. It achieves a maximum efficiency of 94% at 1.5 W output power.

Ferrite toroidal core with a trifilar wound RF broadband transformer design for tracking generators in wideband code division multiple access envelope tracking RFPA systems

In this paper, the design of an RF broadband transformer for wideband code division multiple access (WCDMA) tracking generators to be used in envelope tracking RF power amplifiers systems is presented. A ferrite toroidal core with a trifilar wound RF broadband transformer has been chosen to satisfy the (WCDMA) bandwidth requirement and also the power amplifier performance criteria that include the efficiency, electrical isolation, size and power consumption. The design components investigated comprises ferrite materials, number of turns on core windings and size.

Envelope Tracking RF Power Amplifiers: Fundamentals, Design Challenges, and Unique Opportunities Offered by LEES-SMART InGaAs-on-CMOS Process

The RF power amplifier (PA) is often the most power dissipative block in a smartphone and it usually dissipates ∼50% of the total power. One major drawback of the envelop tracking (ET) PA is the limited (and insufficient) bandwidth of its supply modulator. The emerging LEES-SMART InGaAs-on-CMOS process offers a higher operation speed (due to the high speed InGaAs transistors) and the capability for complex signal processing. In this paper, we present the fundamentals and design challenges of ET PA, and how the emerging LEES-SMART InGaAs-on-CMOS process may be exploited for a high power-efficiency.

A Hysteretic Two-phase Supply Modulator for Envelope Tracking RF Power Amplifiers

In this paper a two-phase supply modulator suitable for envelope tracking power amplifier is presented. The designed supply modulator has the linear assisted switching architecture. Two-phase architecture is used in order to reduce the output switching ripples. The proposed architecture uses hysteretic control instead of pulse width modulation (PWM) which significantly reduces the circuit complexity. Moreover, fewer number of external R and C elements are used which leads to simpler architecture in comparison with reported two-phase PWM supply modulators. The proposed envelope modulator is evaluated with 0.18 µm CMOS technology. The results show that the designed two-phase modulator improves the output switching noise ripples and consequently enhances the overall linearity of the modulator compared to the single-phase case. The overall efficiency of the two-phase envelope modulator is 72.5% with 80 MHz switching frequency for a one-tone 5 MHz envelope signals at 27.4 dBm output power. The RMS output voltage ripples is less than 7.2 mV in a wide range of input signal amplitude while a SFDR of 50.4dB is achieved.

A Combined Series-Parallel Hybrid Envelope Amplifier for Envelope Tracking Mobile Terminal RF Power Amplifier Applications

An improved envelope amplifier architecture for envelope tracking RF power amplifiers is presented, consisting of two switching amplifiers and one linear amplifier. The first switching amplifier and the linear amplifier provide wideband and high-efficiency operation, while the second switching amplifier provides a reduced bandwidth variable supply to the linear amplifier to further reduce power loss. The first switching amplifier and the linear amplifier are fabricated together in a 150 nm CMOS process, while the second switching amplifier is external. Measurements show a maximum average efficiency of 82% for a 10 MHz LTE signal with a 6 dB PAPR at 29.7 dBm output power and an SFDR of 63 dBc for a single tone of 5 MHz driving an 8 Ω load.