Planar Balun Design for Power Amplifier Harmonic Reduction
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Solution Overview
Problem
Existing Balun designs, particularly coaxial Baluns, face challenges in mass production due to accuracy issues and high production costs, and lack phase adjustment mechanisms, making them unsuitable for high-frequency solid-state microwave generators and power amplifiers, which require precise phase control and spectral purity.
Innovation Solution
A planar Balun design using electromagnetically coupled metals in an up-and-down arrangement, with adjustable coupling line widths and lengths to achieve balanced signals, reducing electrical length to less than a quarter wavelength and incorporating impedance gradients for improved balance and phase adjustment, replacing traditional coaxial Baluns in power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coaxial Balun is used in power amplifier, then push-pull operation can be realized, but manufacturing accuracy is difficult to control and production cost is high
Solution Approach 1:
The patent replaces the mechanical coaxial Balun structure with a planar microstrip Balun design that can be fabricated using standard PCB manufacturing processes. The planar structure uses printed transmission lines instead of mechanically assembled coaxial components, eliminating the need for precision coaxial cutting and soldering while maintaining the push-pull operation capability through electromagnetic coupling between differential and single-ended lines.
Solution Approach 2:
The patent creates a planar copy of the traditional coaxial Balun functionality using printed circuit board traces. The microstrip transmission lines replicate the electromagnetic coupling and impedance transformation functions of the coaxial Balun but in a two-dimensional planar format that is suitable for mass production through standard PCB fabrication techniques.
2Reliability
If coaxial Balun is used in power amplifier, then push-pull operation can be realized, but production time is time-consuming due to soldering
Solution Approach 1:
The patent replaces the mechanical assembly and soldering process with a planar PCB-based implementation. The Balun structure is fabricated as part of the PCB itself using standard printing and etching processes, eliminating the time-consuming steps of coaxial component assembly, alignment, and soldering to the PCB board, thereby significantly improving mass production efficiency.
3Area of stationary object
If planar Balun with reduced electrical length is used, then area of power amplifier is reduced, but phase control precision must be maintained
Solution Approach 1:
The patent optimizes the electrical length parameters of the microstrip transmission lines to be less than a quarter wavelength while maintaining precise phase control. By carefully designing the length, width, and spacing of the planar transmission lines, the patent achieves compact size reduction while preserving the phase relationships necessary for accurate phase control in the power amplifier.
4Object-generated harmful factors
If planar Balun is used above 915 MHz, then spectral purity is improved, but design complexity increases
Solution Approach 1:
The patent designs a universal planar Balun structure that serves multiple functions: it provides impedance transformation, differential signal generation, and harmonic suppression above 915 MHz. The microstrip transmission line configuration with specific geometric parameters enables the single planar structure to achieve spectral purity improvement while maintaining circuit layout flexibility through standard PCB design practices.
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 planar Balun design significantly reduces the area and secondary harmonics of power amplifiers, enhances spectral purity, and simplifies amplifier design, enabling mass production with lower costs and improved performance at frequencies above 915 MHz, suitable for phase-controlled microwave heating systems and plasma systems.
Implementation Method 1
uses a first metal and a second metal electromagnetically coupled in an up-and-down arrangement for electromagnetic coupling to generate a balanced signal
Data Source
AI summary
The planar Balun of the present invention can be used in various hundred to and thousand-watt level push-pull power amplifiers, which can greatly reduce the area and the amount of second harmonics of the power amplifier, and improve the flexibility of circuit layout and spectral purity, especially at high frequencies, such as around 915 MHz, and can replace the widely used coaxial Balun to simplify amplifier design.