Doherty Power Amplifier Circuit Without Quarter-Wave Lines
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Solution Overview
Problem
Doherty amplifiers face challenges in achieving miniaturization and wideband characteristics without using quarter-wave lines, which can lead to reduced load modulation effects and efficiency issues.
Innovation Solution
A power amplifier circuit design that includes a carrier amplifier and peaking amplifiers with converters configured to adjust impedance, allowing the carrier amplifier to operate as a current source and the peaking amplifier as a voltage source, eliminating the need for quarter-wave lines while maintaining load modulation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If quarter-wave lines are used in the combiner, then wideband characteristics are achieved, but the device size increases and miniaturization is difficult
Solution Approach 1:
The patent extracts and removes the quarter-wave line from the combiner structure, replacing it with a transformer-based impedance transformation network. This extraction eliminates the space-consuming quarter-wave line while maintaining the essential function of impedance matching and signal combining, thereby achieving miniaturization without sacrificing wideband characteristics.
Solution Approach 2:
The patent substitutes the transmission line-based quarter-wave structure with a transformer-based electrical impedance transformation system. This substitution replaces the mechanical/physical quarter-wave line with an electrical equivalent that achieves the same impedance transformation function in a more compact form factor, enabling miniaturization while preserving wideband operation.
2Volume of moving object
If quarter-wave lines are removed from the combiner, then device miniaturization is achieved, but load modulation effect deteriorates
Solution Approach 1:
The patent changes the impedance transformation parameters by using transformers with specific turns ratios instead of quarter-wave lines. By carefully selecting the transformation ratios and configuring the impedance matching network, the patent maintains the load modulation effect that causes the carrier amplifier's load impedance to reduce by half during transition from back-off to saturation state, even without quarter-wave lines.
Solution Approach 2:
The patent introduces transformers as intermediary elements between the carrier amplifier and peaking amplifier outputs. These transformers serve as mediators that facilitate the load modulation effect by properly transforming impedances and enabling the carrier amplifier to experience the desired load impedance reduction, thereby maintaining reliability of the load modulation effect while achieving miniaturization.
3Device complexity
If transformers are used instead of quarter-wave lines, then device complexity increases, but miniaturization and wideband characteristics are achieved
Solution Approach 1:
The patent merges the functions of the combiner and impedance transformation network into a single integrated transformer-based structure. By combining multiple functions (signal combining, impedance matching, and load modulation) into one unified transformer network, the patent reduces overall device complexity compared to having separate quarter-wave lines and independent impedance matching circuits, while achieving both miniaturization and wideband characteristics.
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 design enables compact, wideband operation with high efficiency by appropriately modulating load impedance without quarter-wave lines, enhancing power amplifier performance.
Implementation Method 1
a first converter connected to an output side of the first amplifier and configured to convert an impedance on the output side of the first amplifier
Implementation Method 2
a first amplifier configured to, in a region where a power level of an input signal is not less than a first level, amplify a first signal split from the input signal and output a second signal
Data Source
AI summary
A power amplifier circuit includes a first amplifier that, in a region where an input signal level is a first level or higher, amplifies a signal split from an input signal and outputs an amplified signal; a first converter connected to an output side of the first amplifier and converts an impedance on the output side of the first amplifier; and at least one or more second amplifiers that, in a region where the input signal level is a second level or higher, amplify a signal split from the input signal and output an amplified signal. Output sides of the second amplifiers are connected in series with an output side of the first converter. The first converter makes an absolute value of the impedance on the output side of the first amplifier larger than absolute values of impedances on the output sides of the second amplifiers.