Coupled Transmission-Line Impedance Transformer for Broadband Matching
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Solution Overview
Problem
High power broadband communication systems require impedance transformers that can match the input impedance of antennas with the transmitter or receiver impedance over a broad bandwidth, especially in military applications where secure spread spectrum communication is needed, and existing transmission-line-based impedance transformers have limitations in bandwidth and power handling.
Innovation Solution
The design incorporates coupled transmission-line sections with specific electrical lengths corresponding to odd-numbered multiples of a quarter wavelength, forming couplers with progressive characteristic impedances to effectively transform impedance between input and output ports, enhancing bandwidth and power handling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional transmission-line-based impedance transformers are used, then impedance transformation is achieved, but bandwidth is limited
Solution Approach 1:
The impedance transformer is divided into multiple quarter-wavelength transmission line sections with different characteristic impedances. Each section transforms impedance progressively, allowing the overall device to achieve broader bandwidth while maintaining reliable impedance matching at each stage. The segmentation enables independent optimization of each section's impedance value to cover a wider frequency range.
2Power
If conventional transmission-line-based impedance transformers are used, then impedance transformation is achieved, but power handling capability is insufficient
Solution Approach 1:
The characteristic impedance values of each transmission line section are specifically designed and optimized to progressively transform the antenna impedance to the transmitter impedance. By carefully selecting impedance parameters (e.g., 50Ω, 70Ω, 100Ω, 200Ω sections) and controlling physical dimensions (width, spacing, substrate properties), the transformer achieves both high power handling capability and low transmission loss across the operating bandwidth.
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 provides broadband impedance transformation with low losses, achieving broad bandwidth and efficient power transmission, suitable for high-power applications like military communication systems.
Implementation Method 1
The first and second signal conductors are electromagnetically closely coupled
Implementation Method 2
The third and fourth signal conductors are electromagnetically closely coupled
Data Source
AI summary
A transmission-line-based impedance transformer including first and second couplers, with each coupler including respective pairs of coupled signal conductors. The signal conductors are connected sequentially in series between an input port and an output port and may form a single spiral configuration. A signal conductor of one coupler may be connected in series between the two signal conductors of another coupler. The couplers have characteristic impedances between an input impedance and an output impedance. A signal conductor of a coupler may include first and second conductor portions disposed in respective spaced-apart parallel planes, with the other signal conductor of the coupler disposed physically directly between the conductor portions. A signal conductor in the spiral may be shielded from coupled signal conductors by ground conductors disposed in respective spaced-apart parallel planes on opposite sides of the shielded signal conductor. The first and second couplers may have a shared signal conductor.