Filter Circuit Balun Signal Reflection Reduction
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Solution Overview
Problem
Existing filter and balun circuits do not effectively reduce signal reflection at frequencies of interest, which is a limitation in reducing phase noise and signal interference.
Innovation Solution
A filter circuit with a branch line coupler and balun circuits, where transmission lines are configured to have specific lengths and electromagnetic coupling, reducing signal reflection by creating a 180-degree phase difference between signal phases, thereby minimizing reflection coefficients at frequencies of interest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmission lines with specific lengths are used to reduce signal reflection, then signal quality improves, but circuit complexity increases
Solution Approach 1:
The transmission lines in the patent serve multiple functions: they provide impedance transformation, create 180-degree phase shifts for signal reflection reduction, and maintain signal transmission. The same quarter-wavelength lines that reduce signal reflection also contribute to the filtering function, making the circuit multi-functional without proportionally increasing complexity.
Solution Approach 2:
The circuit is segmented into distinct functional modules: the branch line coupler with its four terminals and the separate balun circuit with its input and output terminals. This segmentation allows each module to perform its specific function (signal splitting/coupling and impedance transformation) independently, making the overall circuit more manageable and easier to design despite the increased complexity.
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 configuration effectively reduces signal reflection across desired frequency bands, enhancing signal quality by absorbing or removing unwanted frequencies, thus improving the performance of filter and balun circuits.
Implementation Method 1
a fourth transmission line having one end connected to another end of the third transmission line and electromagnetically coupled to the first transmission line
Implementation Method 2
reducing signal reflection by creating a 180-degree phase difference between signal phases
Data Source
AI summary
A filter circuit includes a branch line coupler and a balun circuit having an input terminal connected to the branch line coupler to receive a signal, a first line connected to the input terminal and having a length comparable to a quarter of an electrical length of one wavelength at a frequency of the signal, a second line connected to the input terminal and having a length comparable to the quarter, a third line connected to the second line and having a length comparable to the quarter, and a fourth line connected to the third line and electromagnetically coupled to the first line, the fourth line having a length comparable to the quarter, wherein an end of the first line and an end of the fourth line are both connected to a ground or open-circuited, or are connected to two respective terminating resistors whose resistance values are equal.