Three-Way Doherty Amplifier With Constant-Load Gate Width Ratios
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Solution Overview
Problem
Conventional Doherty amplifiers have limited bandwidth and are insufficient for modern communication devices that need to support multiple communication standards over a wide range of frequencies, leading to increased size, cost, and complexity due to the need for multiple power amplifier chains.
Innovation Solution
A three-way Doherty amplifier is designed with a power splitter that outputs signals with specific phase shifts, and includes multiple amplifier paths with carefully configured impedance loads and gate width ratios to maintain a constant load on the main amplifier, effectively cancelling load modulation and enhancing efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single Doherty amplifier is used, then the device is compact and cost-effective, but it cannot support multiple communication bands with disparate frequency ranges
Solution Approach 1:
The invention divides the single amplifier into three separate amplifier chains (main amplifier, first peak amplifier, second peak amplifier), each configured to handle specific frequency ranges. This segmentation allows each amplifier to be optimized for particular bands while collectively supporting multiple communication standards across disparate frequency ranges.
2Adaptability or versatility
If multiple power amplifier chains are employed to support multiple communication bands, then the frequency coverage is expanded, but the size, cost, and complexity of the communication device increases
Solution Approach 1:
The invention merges three amplifier chains into a single integrated Doherty amplifier architecture with a unified output. By combining the main amplifier and two peak amplifiers through a power combiner, the design achieves multi-band support while maintaining a compact form factor, avoiding the need for completely separate amplifier modules for different frequency ranges.
3Adaptability or versatility
If multiple power amplifier chains are employed to support multiple communication bands, then the frequency coverage is expanded, but the device cost increases
Solution Approach 1:
The Doherty amplifier architecture provides universal functionality by enabling a single device to support multiple communication standards (GSM, UMTS, LTE, WiMAX, 5G, 6G) across disparate frequency ranges. The main amplifier and peak amplifiers can be configured to cover different bands, allowing one amplifier to perform the work of multiple specialized amplifiers, thereby reducing overall device cost.
4Adaptability or versatility
If multiple power amplifier chains are employed to support multiple communication bands, then the frequency coverage is expanded, but the device complexity increases
Solution Approach 1:
The invention introduces a power combiner as an intermediary component that merges the outputs of the main amplifier and two peak amplifiers. This intermediary element simplifies the overall system architecture by providing a unified output interface, reducing the complexity associated with managing multiple separate amplifier chains and their individual outputs.
5Loss of energy
If conventional Doherty amplifier load modulation is used, then the amplifier operates efficiently at peak power, but load modulation causes non-linearity and distortion at lower power levels
Solution Approach 1:
The invention applies different impedance loading conditions to different amplifier paths based on local requirements. The main amplifier is loaded with a first impedance while the peak amplifiers are loaded with a second impedance, allowing each amplifier to operate in its optimal efficiency region. This local quality differentiation maintains signal linearity by preventing excessive load modulation while preserving peak power efficiency.
Data Source
AI summary
A three-way Doherty amplifier according to some embodiments includes a first ratio of a gate width of a main amplifier to a first gate width of a first peak amplifier and a second ratio of the gate width of the main amplifier to a second gate width of a second peak amplifier, respectively, are configured to provide a substantially constant load on the main amplifier.