Doherty RF Circuit Harmonic Reduction Without Fundamental Wave Loss
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Solution Overview
Problem
The existing power amplifier circuit struggles to reduce high-order harmonic waves without deteriorating the transmission characteristics of the fundamental wave, especially when both the first and second amplifiers are operating or not operating.
Innovation Solution
A radio frequency circuit design incorporating multiple amplification devices, transformers, and harmonic reduction circuits with specific inductor and capacitor configurations, including phase shift lines, to minimize harmonic waves while maintaining fundamental wave transmission quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If means for reducing high-order harmonic waves are added to improve linearity, then harmonic wave reduction is achieved, but the transmission characteristics of the fundamental wave are deteriorated
Solution Approach 1:
The patent divides the harmonic reduction function into separate circuits for each amplifier (first harmonic reduction circuit for first amplifier, second harmonic reduction circuit for second amplifier). Each circuit independently processes harmonic waves from its corresponding amplifier without affecting the fundamental wave transmission path, thus resolving the contradiction between harmonic reduction and fundamental wave transmission characteristics.
Solution Approach 2:
The patent introduces LC series resonance circuits as intermediary elements that selectively target harmonic frequencies. These resonance circuits act as mediators that capture and dissipate harmonic energy through controlled resonance at specific harmonic frequencies, while leaving the fundamental wave transmission path unaffected. The resonance circuits are connected in parallel with the amplifiers, allowing them to intercept harmonic waves without interfering with the main signal path.
2Reliability
If high-order harmonic wave reduction is implemented for both operating and non-operating states of amplifiers, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent designs the harmonic reduction circuits to serve multiple functions: they effectively reduce harmonic waves when both amplifiers are operating, and they also provide harmonic reduction when only one amplifier is operating. The same circuit structure handles both operational states without requiring additional components or complex switching mechanisms, thus improving linearity across all states without proportionally increasing device complexity.
3Object-generated harmful factors
If multiple amplification devices and transformers are used to reduce harmonic waves, then harmonic reduction is achieved, but the circuit structure becomes more complex
Solution Approach 1:
The patent applies harmonic reduction circuits locally at each amplifier output rather than using a single complex global solution. Each LC series resonance circuit is tailored to the specific harmonic frequencies generated by its corresponding amplifier, creating a localized solution that is simpler than a comprehensive global harmonic reduction system would be. This distributed approach reduces overall circuit complexity while maintaining effective harmonic suppression.
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
The proposed solution effectively reduces harmonic waves without impairing the transmission characteristics of the fundamental wave, ensuring efficient operation across various signal power levels.
Implementation Method 1
The first circuit has a first inductor and a first capacitor that are connected in series to each other. The first inductor and the first capacitor are disposed in series on a path connecting the ground and a point on a path connecting an output terminal of the first amplification device and an end of the input-side coil
Implementation Method 2
The second circuit has a second inductor, a second capacitor, and a third inductor, the second inductor and the second capacitor being connected in series to each other, the third inductor being connected in parallel to the second capacitor. The second inductor and the second capacitor are disposed in series on a path connecting the ground and a point on a path connecting the output terminal of the second amplification device and the other end of the input-side coil
Implementation Method 3
a transformer having an input-side coil and an output-side coil... An end of the input-side coil is connected to an output terminal of the first amplification device, and another end of the input-side coil is connected to an output terminal of the second amplification device
Data Source
AI summary
A radio frequency circuit includes a carrier amplifier, a peaking amplifier, an input-side coil, an output-side coil, harmonic reduction circuits, and a phase shift line. One end of the input-side coil is connected to the carrier amplifier, and the other end thereof is connected to the peaking amplifier. In the harmonic reduction circuit, an inductor and a capacitor that are connected in series are disposed in series on a path connecting the carrier amplifier and the ground. The harmonic reduction circuit has an inductor and a capacitor that are connected in series and an inductor connected in parallel to the capacitor. The inductor and the capacitor are disposed in series on a path connecting the peaking amplifier and the ground.