Power Amplifier Phase Topology for Wide Back-Off and Smaller Circuits
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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
1Loss of energy
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 specific range of 45-90 degrees. This parameter modification allows the amplifier to achieve both wide back-off range and high efficiency while reducing the physical size of the circuit, as the shorter electrical length corresponds to a smaller physical dimension.
Solution Approach 2:
The patent introduces a variable element (such as a variable capacitor or inductor) that can dynamically adjust the electrical length of the transmission line. This dynamic adjustment capability allows the amplifier to optimize performance for different operating conditions, achieving wide back-off range and high efficiency while maintaining a compact size through adaptive tuning.
2Volume of moving object
If the electrical length of the transmission line is reduced for size reduction, then the circuit size decreases, but the back-off range and efficiency are compromised
Solution Approach 1:
The patent identifies and applies the critical parameter range of 45-90 degrees for the transmission line electrical length. By operating within this specific parameter range, the system achieves an optimal balance where the electrical length is sufficiently short to reduce circuit size while remaining long enough to maintain the necessary back-off range and efficiency characteristics.
Solution Approach 2:
The patent incorporates feedback mechanisms that monitor the operating conditions and adjust the transmission line electrical length accordingly. This feedback control ensures that the amplifier maintains high efficiency and wide back-off range even when the physical size is reduced, by dynamically optimizing the electrical length based on real-time performance measurements.
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.