Doherty Power Amplifier Phase Layout for Wider Back-Off Range
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Solution Overview
Problem
Conventional Doherty amplifiers face challenges in achieving high efficiency over a wide range of output power levels and size reduction, particularly for devices like cellular phones, due to limitations in back-off range and circuit size, especially for signals with high Peak to Average Power Ratio (PAPR).
Innovation Solution
A power amplifier configuration that includes a distributor to split the input signal into two paths with a phase difference of about 2ϕ degrees (45<ϕ<90), a carrier amplifier, a peak amplifier, phase shifters to adjust signal phases, and a combiner to combine the amplified signals, allowing the carrier amplifier to operate in a saturated state and improving efficiency across a wider power range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a λ/4 line is used in the Doherty amplifier, then the back-off range is widened and efficiency is improved, but the circuit size increases
Solution Approach 1:
The patent changes the electrical length parameter of the transmission line from the conventional λ/4 (90 degrees) to a shorter length range of 20 to 60 degrees. This parameter change allows the amplifier to achieve improved back-off range and efficiency while reducing the physical size of the circuit, as the transmission line length is directly proportional to its electrical length at a given frequency.
2Volume of moving object
If the transmission line length is reduced to decrease circuit size, then the back-off range is reduced and efficiency deteriorates
Solution Approach 1:
The patent identifies and optimizes specific parameter ranges for the transmission line electrical length (20 to 60 degrees) and impedance ratio (0.5 to 2.0) that simultaneously achieve both compact size and high efficiency. By carefully selecting these parameters, the invention breaks the traditional trade-off between size and performance.
Solution Approach 2:
The patent designs a Doherty amplifier that can effectively handle multiple signal types including both low PAPR and high PAPR signals, as well as various modulation schemes. The optimized transmission line configuration provides universal performance across different operating conditions, making the compact design applicable to diverse communication scenarios.
3Use of energy by moving object
If the Doherty amplifier is designed for high efficiency, then the back-off range is limited and cannot handle high PAPR signals effectively
Solution Approach 1:
The patent extends the effective back-off range by optimizing the transmission line electrical length to 20-60 degrees, which allows the amplifier to maintain high efficiency over a wider power range. This parameter optimization enables the amplifier to effectively handle high PAPR signals by maintaining efficient operation across more extreme power variations.
Data Source
AI summary
A power amplifier includes a distributor distributing an input first signal to a second signal and a third signal delayed by about 2ϕ degrees (45<ϕ<90) from the second signal, a first amplifier amplifying the second signal and outputting a fourth signal when a first-signal power level is not lower than a first level, a second amplifier amplifying the third signal and outputting a fifth signal when the first-signal power level is not lower than a second level that is greater than the first level, a first phase shifter receiving the fourth signal and outputting a sixth signal delayed by about ϕ degrees from the fourth signal, a second phase shifter receiving the fifth signal and outputting a seventh signal advanced by about ϕ degrees from the fifth signal, and a combiner combining the sixth and seventh signals and outputting an amplified signal of the first signal.