Doherty Amplifier Trunk Thickness Tuning for Wideband RF Efficiency
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Solution Overview
Problem
Current Doherty amplifiers experience efficiency degradation when amplifying wideband modulated RF signals, such as 5G NR signals with 600 MHz bandwidth, due to limitations in trunk thickness settings that affect load impedances and power efficiency.
Innovation Solution
The Doherty amplifier is configured with specific trunk thickness settings for both the main and auxiliary amplifiers, optimizing voltage standing wave ratios (VSWR) to maintain high efficiency across a wide frequency band, by setting the trunk thicknesses such that VSWR between load impedances is minimized, ensuring maximum power efficiency and power delivery at target average and peak power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional trunk thickness settings are used in Doherty amplifiers, then the amplifier structure is simple and easy to manufacture, but the efficiency degrades when amplifying wideband modulated RF signals
Solution Approach 1:
The patent applies parameter changes by optimizing the trunk thickness values for both the main and auxiliary amplifiers to specific ranges. The main amplifier trunk thickness is set to 0.5-1.5 times the wavelength divided by 4, while the auxiliary amplifier trunk thickness is set to 0.3-0.7 times the wavelength divided by 4. These parameter adjustments transform the conventional fixed trunk thickness design into an optimized variable design that maintains high efficiency across wideband modulated RF signals while managing the complexity through systematic parameter selection
2Adaptability or versatility
If the Doherty amplifier is optimized for continuous wave or pulsed-CW signals, then high efficiency is achieved at specified average power, but the efficiency degrades when amplifying wideband modulated RF signals with high peak to average ratio
Solution Approach 1:
The patent applies dynamics by configuring the trunk thickness values to dynamically adapt to different signal conditions. The optimized trunk thickness allows the amplifier to maintain proper load impedance modulation across varying signal power levels, enabling the system to transition effectively between continuous wave, pulsed-CW, and wideband modulated signal modes while preserving efficiency at both average and peak power levels
Solution Approach 2:
The patent applies local quality by creating different trunk thickness characteristics for the main and auxiliary amplifiers. The main amplifier has a larger trunk thickness (0.5-1.5λ/4) optimized for continuous operation, while the auxiliary amplifier has a smaller trunk thickness (0.3-0.7λ/4) optimized for peak power supplementation. This localized differentiation allows each amplifier to perform its specific function optimally, improving overall adaptability to different signal types
3Power
If the trunk thickness is increased to improve power handling, then maximum output power is enhanced, but the voltage standing wave ratio increases and efficiency decreases
Solution Approach 1:
The patent applies asymmetry by setting different trunk thickness values for the main and auxiliary amplifiers rather than using identical dimensions. The main amplifier trunk thickness (0.5-1.5λ/4) is deliberately made larger than the auxiliary amplifier trunk thickness (0.3-0.7λ/4). This asymmetric configuration creates optimal load impedance modulation patterns that enable high power handling while maintaining stable voltage standing wave ratio, resolving the contradiction between power enhancement and stability
Data Source
AI summary
A Doherty amplifier is disclosed. In some embodiments, the Doherty amplifier includes: a main amplifier defining a first trunk thickness; an auxiliary amplifier defining a second trunk thickness. Impedances of the Doherty amplifier are set by selecting the first trunk thickness of the main amplifier and the second trunk thickness of the auxiliary amplifier. In this manner, the power efficiency of the Doherty amplifier is improved when amplifying a modulated signal.