Doherty Amplifier Impedance Tuning for Wideband Modulated RF
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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 600MHz bandwidth, due to limitations in impedance matching and power handling.
Innovation Solution
The Doherty amplifier is designed with specific trunk thickness settings for its main and auxiliary amplifiers, optimizing impedance matching by setting the voltage standing wave ratio (VSWR) within defined ranges to maintain high efficiency across a wide frequency band, particularly for modulated signals with peak-to-average ratios (PAR) of 6 to 12 dB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional Doherty amplifier designs are used, then the amplifier achieves high efficiency at specified average power with CW or pulsed-CW signals, but the efficiency degrades when amplifying wideband modulated RF signals
Solution Approach 1:
The patent applies local quality by setting different trunk thicknesses for the main amplifier and auxiliary amplifier. The main amplifier has a first trunk thickness optimized for its operating conditions, while the auxiliary amplifier has a second trunk thickness optimized for its peaking function. This localized optimization of structural parameters enables each amplifier to operate at peak efficiency for its specific role, resolving the contradiction between maintaining high efficiency and handling wideband modulated signals with varying power levels.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the trunk thickness dimensions of the amplifiers to specific ranges. The first trunk thickness is set between 700-1400 Angstroms and the second trunk thickness is set between 700-1400 Angstroms, with specific VSWR targets. These parameter modifications transform the amplifier's impedance characteristics to maintain efficiency across wide frequency bands and varying signal types, resolving the degradation issue with modulated signals.
2Use of energy by moving object
If the amplifier is optimized for high efficiency at average power, then it maintains good performance for continuous wave signals, but it cannot maintain high efficiency for modulated signals with high peak-to-average ratios over wide frequency bands
Solution Approach 1:
The patent implements local quality by creating distinct impedance environments for the main and auxiliary amplifiers through different trunk thicknesses. The main amplifier's first trunk thickness optimizes its load impedance for average power efficiency, while the auxiliary amplifier's second trunk thickness optimizes its impedance for peak power handling. This localized impedance optimization ensures reliable performance consistency across the entire frequency band and for all signal types.
Solution Approach 2:
The patent applies dynamics by enabling the amplifier system to adapt its effective impedance characteristics based on the operating signal conditions. The specific trunk thickness configuration creates dynamic impedance matching that automatically adjusts to maintain optimal efficiency whether operating with CW signals, pulsed-CW signals, or wideband modulated signals with high PAR, ensuring reliability across varying operating conditions.
3Ease of manufacture
If the amplifier uses standard trunk thickness dimensions, then the manufacturing is simpler, but the impedance matching is insufficient for wideband operation with modulated signals
Solution Approach 1:
The patent applies parameter changes by specifying precise trunk thickness ranges (700-1400 Angstroms) that optimize impedance matching for wideband operation. These parameter specifications transform the manufacturing process from using standard dimensions to using optimized dimensions that achieve the required VSWR performance. The well-defined parameter ranges maintain ease of manufacture while achieving the precision needed for wideband modulated signal amplification.
Data Source
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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.