Power Amplifier Combining Circuit for Isolation and Real Impedance
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Solution Overview
Problem
Current power amplifier configurations, such as those described in Japanese Unexamined Patent Application Publication No. 2012-54874, face limitations in improving output power and linearity, especially with the advent of communication standards like LTE-Advanced that require simultaneous transmission of multiple frequency bands, due to impedance matching issues that result in a substantially imaginary impedance on the load side, hindering amplifier performance.
Innovation Solution
A power amplifier module design that includes a divider circuit, amplifiers, a combining circuit with inductors and capacitors for phase shifting, and a resistance element connected in parallel with a capacitor, which ensures isolation between amplifiers by canceling signal amplitudes in unbalanced modes and achieves real impedance on the load side, thereby enhancing linearity and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single passive element is used for impedance matching between amplifier elements and the load side, then the configuration is simple, but the impedance on the load side becomes substantially imaginary, limiting amplifier performance and linearity
Solution Approach 1:
The single passive impedance matching element is segmented into multiple elements: a first passive element connected in series between the amplifier element and combiner, and a second passive element connected in series between the combiner and load. This segmentation allows independent optimization of each element's impedance characteristics, enabling the overall system to achieve real impedance on the load side while maintaining simplicity.
Solution Approach 2:
The invention changes the impedance parameters by introducing phase shifters that adjust the phase of signals by specific amounts (e.g., 45 degrees) before combining them. This phase adjustment transforms the impedance characteristics, converting the substantially imaginary impedance into real impedance, thereby improving amplifier performance and linearity without significantly increasing system complexity.
2Device complexity
If amplifier elements are connected without isolation mechanisms, then the configuration is simple, but signals from one path enter the other path in unbalanced mode, reducing isolation between amplifier elements
Solution Approach 1:
An isolation resistor is introduced as an intermediary component electrically connecting the output terminals of the amplifier elements to each other. This resistor acts as a mediator that absorbs signals from one path entering the other path in unbalanced mode, thereby ensuring proper isolation between amplifier elements without requiring complex isolation mechanisms.
3Ease of manufacture
If the impedance on the load side is not optimized to be real, then the configuration allows for simpler design, but the performance of amplifier elements cannot be maximized and linearity improvement is difficult
Solution Approach 1:
The invention systematically changes impedance parameters through a combination of series passive elements and phase shifters. The phase shifters adjust signal phases by specific amounts (e.g., 45 degrees each), and the series passive elements are designed with specific impedance values to transform the load impedance into a real value, thereby maximizing amplifier element performance and improving linearity while maintaining design feasibility.
Solution Approach 2:
The invention introduces adjustable phase shifters that can dynamically adjust the phase of signals to optimize impedance matching. This dynamic adjustment capability allows the system to adapt to different operating conditions and maintain real impedance on the load side, thereby maximizing amplifier performance across various scenarios.
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 power amplifier module achieves high output power and linearity by ensuring isolation between amplifiers and optimizing impedance, allowing it to perform better than previous configurations, particularly in unbalanced modes and across various communication standards.
Implementation Method 1
A phase of the third signal from the output terminal of the first amplifier to the output terminal of the second amplifier through the first capacitor is advanced by about 90 degrees
Implementation Method 2
A phase of the third signal from the output terminal of the first amplifier to the output terminal of the second amplifier through the combiner is delayed by about 45 degrees in a first phase shifter including the first inductor and the second capacitor
Data Source
AI summary
A power amplifier module includes a combining circuit including a combiner. The combining circuit further includes a first inductor connected in series between an output terminal of a first amplifier and the combiner, a second inductor connected in series between an output terminal of a second amplifier and the combiner, and a second capacitor having an end connected to the combiner and another end grounded. A phase of a third signal from the output terminal of the first amplifier to the second amplifier through the combiner is delayed by about 45 degrees in the first inductor and the second capacitor, and is delayed by about 45 degrees in the second inductor and the second capacitor. A phase of the third signal from the output terminal of the first amplifier to the second amplifier through the first capacitor is advanced by about 90 degrees.