Multi-Stage Doherty Amplifier With Time-Delayed Peaking Drive
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Solution Overview
Problem
Conventional power amplifiers face low average efficiency when amplifying signals with high peak-to-average power ratio due to inefficient DC current usage, especially in wideband Doherty amplifiers, which complicates input drive circuits and reduces bandwidth and transistor utilization.
Innovation Solution
The proposed solution involves an amplifier arrangement with multiple stages, including a main amplifier stage and peaking amplifier stages, where at least two peaking amplifiers are collectively driven with time-delayed versions of the same signal, and a transmission line with varying impedance to transform the load impedance to a higher impedance, optimizing load resistances and phase angles for consistent high efficiency across a wide bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-transistor power amplifier is used, then the circuit is simple, but the average efficiency is low when amplifying signals with high peak-to-average power ratio
Solution Approach 1:
The amplifier is divided into multiple independent amplifier stages, each handling different portions of the signal spectrum. This segmentation allows each stage to operate efficiently at different power levels, resolving the contradiction between circuit simplicity and average efficiency by distributing the amplification function across multiple specialized units.
Solution Approach 2:
The patent introduces a spectral dimension by processing different frequency components separately through multiple amplifier stages. This dimensional approach transforms the single-stage time-domain amplification into a multi-stage frequency-domain processing system, achieving high average efficiency while maintaining manageable circuit complexity through parallel processing.
2Use of energy by moving object
If wideband Doherty amplifiers are used to improve efficiency, then average efficiency increases, but the input drive circuits become complicated and bandwidth is reduced
Solution Approach 1:
The input drive circuit complexity is segmented and distributed across multiple amplifier stages, each with its own simplified drive circuit. Instead of one complex drive circuit for the entire wideband signal, each stage receives a narrower bandwidth signal that is easier to drive, reducing overall drive circuit complexity while maintaining high average efficiency through the multi-stage architecture.
Solution Approach 2:
The patent moves the complexity from the time-domain drive circuit to the frequency-domain signal distribution. By spectrally separating the input signal and routing different frequency components to different amplifier stages, the drive circuit complexity is managed through frequency-based routing rather than complex time-domain circuitry, simplifying the actual drive circuits while achieving wideband operation.
3Adaptability or versatility
If more peaking amplifiers are added to increase bandwidth, then the bandwidth of high efficiency increases, but the device complexity increases
Solution Approach 1:
The amplifier system is segmented into multiple stages with progressively narrower bandwidth responsibilities. Each stage handles a specific spectral portion, allowing the overall system to achieve wide bandwidth of high efficiency. The segmentation principle allows complexity to be distributed and managed modularly, where each stage can be designed and optimized independently.
Solution Approach 2:
Each amplifier stage is optimized for its specific local bandwidth requirement rather than designing one stage for the entire bandwidth. This local quality approach allows each stage to be simpler and more efficient at its designated frequency range, while the combination of stages achieves the overall wide bandwidth of high efficiency without proportionally increasing total device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves high efficiency and consistent performance over large bandwidths, simplifies static gain and bias settings, and allows for increased bandwidth by optimizing the number and size of peaking amplifiers, reducing transition point ripple and maintaining high efficiency across the design bandwidth.
Implementation Method 1
a transmission line comprising a varying impedance for transforming a load impedance to a higher impedance at the main amplifier stage
Data Source
AI summary
An amplifier arrangement comprises N amplifier stages comprising a main amplifier stage and a plurality of peaking amplifier stages. A transmission line comprises a varying impedance for transforming a load impedance to a higher impedance at the main amplifier stage, wherein the plurality of peaking amplifiers are coupled at intermediate locations to the transmission line. The amplifier arrangement is configured such that at least two of the peaking amplifiers are collectively driven with time delayed versions of substantially the same signal. The amplifier arrangement may be configured to operate with N−2 or fewer transition points in a Doherty mode of operation. As such, the amplifier arrangement may comprise more amplifier stages than are necessarily required in a Doherty amplifier arrangement having the same number of transition points.