Doherty Amplifier Bandpass Synthesis for Broadband Efficiency
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Solution Overview
Problem
Doherty amplifiers experience a decrease in amplification efficiency due to parasitic capacitance influences when the amplification target signal frequency is outside the resonance frequency, affecting both the carrier and peak amplifiers.
Innovation Solution
Incorporating a bandpass filter circuit with parasitic capacitances at the output sides of the carrier and peak amplifiers within the synthesis circuit of the Doherty amplifier, which delays the phase of the signals by 90 degrees across the operating frequency band, rather than relying on resonance circuits that only resonate at specific frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If resonance circuits are used to reduce parasitic capacitance influence, then amplification efficiency is improved at resonance frequency, but amplification efficiency deteriorates at frequencies other than resonance frequency
Solution Approach 1:
The invention changes the operating parameters of the resonance circuits by adjusting the capacitance values (including parasitic capacitances) and inductance values to achieve resonance at different frequencies. This allows the amplifier to maintain high efficiency across a broader frequency range by retuning the resonance conditions.
Solution Approach 2:
The invention makes the resonance circuits serve multiple functions: they simultaneously act as impedance matching networks and as efficiency-enhancing resonant structures. By carefully designing the circuit topology, the same components that create resonance effects also provide broadband impedance transformation, thereby improving both efficiency and frequency adaptability.
2Reliability
If resonance circuits are used to compensate parasitic capacitance, then return loss is improved at resonance frequency, but return loss deteriorates at other frequencies
Solution Approach 1:
The invention adjusts the resonant parameters (capacitance and inductance values) of the output resonance circuits to achieve optimal return loss characteristics. By changing these parameters, the resonance frequency is tuned to compensate for parasitic capacitance effects while maintaining good impedance matching over a wider frequency range.
3Loss of energy
If resonance circuits are used to reduce parasitic capacitance impact, then backoff efficiency is improved at resonance frequency, but backoff efficiency deteriorates at other frequencies
Solution Approach 1:
The invention optimizes the resonance circuit parameters (capacitance and inductance values) to achieve resonance at frequencies that maximize backoff efficiency. By adjusting these parameters, the amplifier maintains high efficiency across a broader frequency range, not just at a single resonant frequency.
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 maintains amplification efficiency by reducing the impact of parasitic capacitance across the operating frequency band, providing wider band frequency characteristics for return loss and backoff efficiency compared to traditional resonance-based designs.
Implementation Method 1
a bandpass filter circuit that includes, as a capacitor, a parasitic capacitance at an output side of each of the carrier amplifier and the peak amplifier
Implementation Method 2
An output side of the carrier amplifier includes a parasitic capacitance (hereinafter, referred to as a 'first parasitic capacitance'), and an amplification factor of the carrier amplifier lowers more as the first parasitic capacitance is greater
Data Source
AI summary
A Doherty amplifier includes: a carrier amplifier that amplifies a first signal; a peak amplifier that amplifies a second signal; and a synthesis circuit that synthesizes the first signal amplified by the carrier amplifier and the second signal amplified by the peak amplifier, and the synthesis circuit includes a bandpass filter circuit that includes parasitic capacitances at respective output sides of the carrier amplifier and the peak amplifier as capacitors.