Matrix Balun Circuit for Wideband 180° Phase-Balanced RF Output
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Solution Overview
Problem
Existing baluns face limitations in bandwidth and amplitude balance, with passive baluns being narrow-banded and lossy, and active baluns requiring RF-out signals to be below the input signal amplitude for amplitude balance.
Innovation Solution
A matrix balun with multiple transmission lines and amplifiers arranged in rows, allowing direct coupling between input and output lines, and adjustable impedance to achieve balanced RF-out signals with equal or greater amplitude and 180° phase difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive LC-lumped balun is used, then the structure is simple, but the bandwidth is limited and insertion loss exceeds 3 dB
Solution Approach 1:
The balun is divided into multiple lattice sections (first lattice section, second lattice section, etc.) connected in series. Each section contributes to the overall frequency response, creating a multi-section structure that extends bandwidth while maintaining amplitude balance. This segmentation allows the system to overcome the narrow bandwidth limitation of single-section passive baluns.
Solution Approach 2:
Multiple lattice sections are combined in series to form a multi-section balun. The combining of these sections creates a cumulative effect on the frequency response, achieving broader bandwidth and improved signal quality while maintaining the passive structure's simplicity.
2Reliability
If active balun with amplifiers is used, then bandwidth is improved, but RF-out signal amplitude must be below RF-in signal amplitude for amplitude balance
Solution Approach 1:
Different lattice sections have different characteristic impedances and electrical lengths optimized for specific frequency ranges. The first lattice section has different parameters than the second lattice section, allowing each to contribute optimally to different parts of the bandwidth, achieving broad bandwidth while maintaining amplitude balance without requiring RF-out below RF-in.
Solution Approach 2:
The characteristic impedances and electrical lengths of the lattice sections are specifically designed with varying parameters. By changing these parameters across different sections, the system achieves broad bandwidth operation while maintaining proper amplitude balance, eliminating the constraint that RF-out must be below RF-in.
3Device complexity
If wire-wound transformer balun is used, then the structure is simple, but losses are produced and bandwidth is narrow
Solution Approach 1:
The mechanical wire-wound transformer structure is replaced with an electrical lattice network using transmission lines with specific characteristic impedances. This substitution eliminates the core losses and winding resistances inherent in wire-wound transformers, reducing insertion loss while extending bandwidth, though the structure becomes slightly more complex.
Data Source
AI summary
An active input matrix balun and a method for the same. The matrix balun has one input transmission line with an RF-in terminal for receiving a single ended RF-in signal and a first output transmission line with a first RF-out terminal and an adjacent second output transmission line with a second RF-out terminal. Two balanced RF-out signals at the first and at the second RF-out terminal, where each RF-out signal has an amplitude level equal to or exceeding the amplitude level of the RF-in signal and where the RF-out signals have a mutual phase difference of 180° and are of equal amplitude levels.