Load-Modulated Power Amplifier With Transformer Impedance Matching
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Solution Overview
Problem
The existing Load Modulated Balanced Amplifier (LMBA) configuration based on 50 Ω termination lacks an impedance matching circuit, resulting in a large difference in output voltage between the main and control amplifiers, which limits output efficiency and narrows the amplifier's bandwidth.
Innovation Solution
A power amplifier circuit is designed with a first power splitter, a pair of amplifiers connected in parallel, a control amplifier for load impedance control, and impedance matching units using transmission line transformers to match impedances between the control and main amplifiers, allowing for improved output efficiency and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an impedance matching circuit is provided between the control amplifier and the main amplifier to raise the output voltage of the control amplifier, then output efficiency is improved, but the band of the LMBA becomes narrow
Solution Approach 1:
A coupler is introduced as an intermediary component between the control amplifier and the main amplifier. The coupler combines the output signals while enabling impedance matching through its coupling structure, thereby improving output efficiency without restricting the bandwidth of the overall amplifier system
Solution Approach 2:
The invention changes the impedance parameters dynamically by using the coupler to adjust the load impedance seen by the control amplifier. This allows the control amplifier to operate at optimal impedance conditions across a wide frequency range, simultaneously improving output efficiency and maintaining broad bandwidth
2Device complexity
If no impedance matching circuit is provided in the LMBA based on 50 Ω termination, then the structure is simple, but there is a large difference in maximum output voltage between the main amplifier and the control amplifier
Solution Approach 1:
The coupler serves multiple functions simultaneously: it acts as a signal combiner for the parallel amplifiers, provides impedance matching for the control amplifier, and enables proper power combining. This multi-functionality improves output voltage balance without adding separate dedicated components for each function
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 solution effectively widens the bandwidth and enhances output efficiency by dynamically adjusting load impedance and utilizing transmission line transformers for impedance matching, reducing the size of the power amplifier module.
Implementation Method 1
a first impedance matching unit that is electrically connected in series between the amplifier circuit and the control amplifier and includes a transmission line transformer
Data Source
AI summary
A power amplifier circuit includes: a first power splitter that splits an input signal into a first input signal and a second input signal; an amplifier circuit that includes a pair of amplifiers electrically connected in parallel and that amplifies the first input signal and outputs an output signal to an output terminal; a control amplifier that amplifies the second input signal and outputs, to the amplifier circuit, a control signal for controlling load impedance of the amplifier circuit; and a first impedance matching unit that is electrically connected in series between the amplifier circuit and the control amplifier and includes a transmission line transformer.