Digital Doherty Transmitter Phase Alignment for Wider Bandwidth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Doherty amplifier architectures, particularly two- and three-stage designs, face inefficiencies due to complex gain fluctuations, power-dependent phase misalignment, and narrow bandwidth, leading to suboptimal power amplification and load modulation in wireless communication systems with high peak-to-average power ratio (PAPR) signals.
Innovation Solution
A digital Doherty transmitter architecture incorporating a baseband signal processing block with digital predistortion, adaptive signal distribution, and phase alignment units, along with an RF power amplification block featuring a carrier amplifier and peaking amplifiers, and an RF Doherty combining network with predefined topology, ensures quasi-ideal load modulation and linear operation across extended bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional two-stage or three-stage Doherty amplifier architectures are used, then power amplification efficiency is improved at specific back-off points, but bandwidth is limited and phase alignment becomes power-dependent
Solution Approach 1:
The patent implements dynamic phase alignment by continuously adjusting the phase of peaking amplifier signals based on real-time power levels and frequency conditions. This dynamic adjustment mechanism allows the system to maintain optimal phase relationships across varying operating conditions, thereby extending bandwidth while preserving power amplification efficiency at different back-off points.
Solution Approach 2:
The system changes multiple parameters simultaneously including phase shift values, signal distribution ratios, and amplifier bias conditions based on operating point detection. By adaptively modifying these parameters in response to power level and frequency variations, the amplifier maintains efficient operation across an extended bandwidth range rather than at fixed operating points.
2Adaptability or versatility
If digital predistortion and adaptive signal distribution are implemented, then linear operation across extended bandwidth is achieved, but device complexity increases
Solution Approach 1:
The digital signal processing system performs self-calibration and automatic adjustment by monitoring its own output and detecting operating conditions. The adaptive signal distribution unit automatically optimizes signal routing and phase alignment without external intervention, and the predistortion unit continuously compensates for nonlinearities based on real-time feedback, thereby managing complexity through self-regulation rather than requiring complex external control systems.
Solution Approach 2:
The system incorporates feedback loops where the output signal characteristics are monitored and used to adjust predistortion parameters and phase alignment in real-time. This feedback mechanism allows the complex digital processing functions to automatically adapt to changing conditions, maintaining linear operation across extended bandwidth while the system self-manages its own complexity through closed-loop control.
Data Source
AI summary
An extended bandwidth digital Doherty transmitter includes a baseband signal processing block including a digital predistortion unit. It also includes a digital signal distribution unit and a digital phase alignment unit, a signal up-conversion block, an RF power amplification block including the carrier amplifier and one or two peaking amplifiers; and an RF Doherty combining network. In another aspect, a digital Doherty transmitter includes a baseband signal block including a digital predistortion unit, a digital signal distribution unit and an adaptive digital phase alignment unit. In this aspect a signal up-conversion block includes three digital-to-analog converters (DACs) and a tri-channel up-converter or three single-channel up-converters. There is also an RF power amplification block including the carrier amplifier and two peaking amplifiers, and an RF Doherty combining network which includes quarter wavelength impedance transformers.