Doherty RF Amplifier Without Hybrid Coupler for Load Mismatch
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Solution Overview
Problem
RF amplifiers face efficiency and output power degradation due to impedance mismatches caused by varying load conditions, particularly in environments like solid-state cooking apparatuses and base stations, where impedance changes with food type or weather conditions.
Innovation Solution
The RF amplifier employs Doherty amplifiers with specific phase relationships between main and peak amplifiers, eliminating the need for a hybrid coupler by using different phase delays and impedance inverters to maintain consistent impedance at the output, thereby reducing sensitivity to load variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quadrature hybrid coupler is used to combine amplified RF signal parts, then impedance mismatch effects are mitigated, but device area increases and insertion loss increases
Solution Approach 1:
The patent extracts and removes the quadrature hybrid coupler from the amplifier system. Instead of using a hybrid coupler to combine signals and mitigate impedance mismatch, the invention uses two separate Doherty amplifiers with inherently different phase delays (0° and 90°) that directly output their amplified signals without requiring an additional coupling component. This eliminates the area and insertion loss penalties associated with the hybrid coupler while maintaining impedance mismatch mitigation through the phase-diverse amplifier architecture.
Solution Approach 2:
The Doherty amplifiers serve multiple functions simultaneously: they provide signal amplification, inherent phase shifting (0° and 90°), and impedance mismatch mitigation. By making the amplifiers multi-functional, the patent eliminates the need for separate phase-shifting and signal-combining components like hybrid couplers, thereby reducing device area and insertion loss while maintaining the desired impedance robustness.
2Reliability
If a quadrature hybrid coupler is used to combine amplified RF signal parts, then impedance mismatch effects are mitigated, but efficiency and maximum output power are degraded
Solution Approach 1:
The patent removes the quadrature hybrid coupler from the signal path, eliminating its associated insertion loss. The two Doherty amplifiers directly output their amplified signals with inherent phase differences, avoiding the energy losses that occur in the hybrid coupler's signal combining process. This extraction of the lossy component improves overall system efficiency and maximum output power while maintaining impedance mismatch mitigation.
Solution Approach 2:
The Doherty amplifiers self-generate the required phase shifts (0° and 90°) as part of their intrinsic operation, eliminating the need for external phase-shifting components that would introduce additional insertion loss. Each amplifier independently provides its designated phase shift, and their outputs are directly combined without requiring energy-dissipating coupling components, thereby improving efficiency.
3Device complexity
If multiple Doherty amplifiers with different phase delays are used, then hybrid coupler is eliminated, but phase delay precision must be maintained
Solution Approach 1:
The patent uses fixed, predetermined phase delay values (0° and 90°) for the two Doherty amplifiers, which simplifies the design and manufacturing process. By specifying discrete phase delay parameters rather than requiring continuous or adjustable phase control, the system reduces manufacturing precision requirements while maintaining the benefits of hybrid coupler elimination and reduced circuit complexity.
Data Source
AI summary
Example embodiments relate to radiofrequency, RF, amplifiers and electronic devices that include RF amplifiers. One example RF amplifier includes a splitter configured to split an RF input signal received at an input of the RF amplifier into a plurality of RF signal parts. The RF amplifier also includes a plurality of Doherty amplifiers, each Doherty amplifier having a main amplifier and a peak amplifier. Each Doherty amplifier is configured to amplify a respective RF signal part and output a respective amplified RF signal part. Additionally, the RF amplifier includes a combiner. The combiner is configured to combine the amplified RF signal parts from the plurality of Doherty amplifiers into an RF output signal and output the RE output signal. The combiner includes a plurality of inputs and an output. Each input of the combiner is connected to an output of a respective Doherty amplifier among the plurality of Doherty amplifiers.