Digital Doherty Amplifier With Adaptive Phase Alignment

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Solution Overview

Problem

Existing Doherty amplifier architectures, particularly two- and three-stage configurations, face inefficiencies due to complex gain fluctuations, power-dependent phase misalignment, and power loss in peaking paths, leading to degraded efficiency and imperfect load modulation.

Innovation Solution

A digital Doherty amplifier architecture that incorporates a baseband signal processing block with digital predistortion, adaptive digital signal distribution, and dynamic adaptive digital phase alignment, combined with an RF power amplification block featuring a carrier amplifier and peaking amplifiers, and an RF Doherty combining network with predefined topology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If digital predistortion and adaptive digital phase alignment are implemented, then linearity and power efficiency are improved, but device complexity increases

Engineering Contradiction:

ImprovelinearityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Digital predistortion is applied in advance to the baseband signal to pre-compensate for nonlinearities in the power amplifiers. This preliminary action corrects distortion before the signal enters the RF path, improving linearity without requiring complex linearization circuits in the RF stage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Analog phase alignment and amplitude balancing mechanisms are replaced with digital signal processing in the baseband domain. The adaptive digital phase alignment unit uses digital algorithms to compensate for phase differences and gain variations, substituting complex RF analog tuning circuits with programmable digital logic.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If peaking amplifiers are used to extend efficiency range, then power efficiency is improved, but power loss in peaking paths increases

Engineering Contradiction:

Improvepower efficiencyVSAvoidpower loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The signal distribution to peaking amplifiers is dynamically adjusted based on the instantaneous signal envelope. The adaptive digital signal distribution unit modulates the amplitude and phase of signals entering peaking amplifiers, ensuring they operate efficiently only when needed and minimizing power consumption when signal levels are low.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The operating parameters of peaking amplifiers are dynamically changed through digital predistortion and adaptive signal distribution. By adjusting the input signal characteristics to peaking amplifiers based on real-time conditions, the system optimizes their efficiency and minimizes power loss in the peaking paths.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If multiple peaking amplifiers are added to handle higher PAPR, then adaptability is improved, but device complexity and cost increase

Engineering Contradiction:

ImprovePAPR handling capabilityVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The digital signal processing units (predistortion, phase alignment, signal distribution) serve multiple functions simultaneously. These baseband processing blocks manage the operation of carrier and peaking amplifiers, coordinate their switching, and compensate for their combined nonlinearities, making the system adaptable to different PAPR conditions without proportionally increasing RF hardware complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12348190B2Digital Doherty transmitter

Publication Date: 2025.07.01 GHANNOUCHI FADHEL M

AI summary

A digital Doherty amplifier compromises a baseband signal processing block including a digital predistortion unit, a digital signal distribution unit and a digital phase alignment unit; a signal up-conversion block, an RF power amplification block, the RF power amplification block including the carrier amplifier and one or two peaking amplifiers; and a RF Doherty combining network. In another aspect, a digital Doherty amplifier compromises a baseband signal block including a digital predistortion unit, a digital signal distribution unit and an adaptive digital phase alignment unit; a signal up-conversion block; a signal up-conversion block, the signal up-conversion block including three digital-to-analog converters (DACs) and a tri-channel up-converter or three single-channel up-converters; a RF power amplification block, the RF power amplification block including the carrier amplifier and two peaking amplifiers; and an RF Doherty combining network which includes quarter wavelength impedance transformers.