Tunable Triaxial Cable Balun for RF Current Trapping
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Solution Overview
Problem
Conventional baluns are difficult to install once both ends of a cable are connectorized and soldered, and they lack the ability to be adjusted for frequency or installed on a cable from the side to block stray RF current on shield conductors of RF cables.
Innovation Solution
A tunable RF cable balun system that allows for adjustable parameters such as capacitance and inductance, using electrically controlled actuators like piezo-electrical motors or MEMS mechanical actuators, to connect the outer shield of a triaxial cable to its inner shield at a specific electrical distance, effectively trapping stray RF currents, even in high-field environments like those found in particle physics experiments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional baluns are installed after cable termination, then the cable can be connectorized and soldered first, but the balun becomes difficult or impossible to install
Solution Approach 1:
The balun is designed to be installed on the cable before termination, allowing the cable to be connectorized and soldered afterward without difficulty. This preliminary installation enables access to the cable surface for balun attachment while avoiding the constraints of post-termination installation.
Solution Approach 2:
Instead of the conventional approach of terminating the cable first and then attempting to install the balun, the invention inverts the sequence by installing the balun first on the unterminated cable, making the subsequent termination process straightforward and unobstructed.
2Reliability
If conventional baluns are used, then they can block RF current at a fixed frequency, but they lack the ability to be adjusted for different frequencies
Solution Approach 1:
The balun incorporates adjustable inductance and capacitance parameters that can be dynamically modified to change the resonant frequency. This dynamic adjustment capability allows the balun to adapt to different frequency requirements while maintaining effective RF current blocking through resonant circuit tuning.
Solution Approach 2:
The invention enables frequency adjustment by changing the electrical parameters (inductance L and capacitance C) of the resonant circuit within the balun. By modifying these parameters, the resonant frequency can be tuned to different values, providing versatility across multiple frequency ranges while preserving the blocking function.
3Ease of operation
If baluns are installed from the side of the cable, then they can be attached to installed cables, but the installation method becomes more complex
Solution Approach 1:
The balun is designed as a modular device that can be attached to the cable from the side rather than requiring end-access installation. This segmented approach allows the balun to be mounted on already-installed cables without disrupting existing connections, simplifying the overall installation process despite the side-attachment mechanism.
4Adaptability or versatility
If adjustable parameters are added to the balun, then frequency tuning capability is improved, but the device complexity increases
Solution Approach 1:
The adjustable inductance and capacitance elements are integrated within the compact balun structure, with tuning components nested inside the housing. This nested arrangement provides frequency adjustment capability while minimizing the increase in overall device complexity and maintaining a compact form factor.
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
Enables the adjustment of RF trap parameters to block stray signals effectively across a wide range of frequencies and environments, including high-field settings, without introducing extraneous capacitances or inductances, allowing for precise control of RF currents on shield conductors.
Implementation Method 1
an LC circuit having a resonance frequency equal to RF signals carried on the inner conductor
Implementation Method 2
using electrically controlled actuators like piezo-electrical motors or MEMS mechanical actuators
Data Source
AI summary
Apparatus and method for trapping RF on shields of a multiply shielded RF cable. In some embodiments, the RF trap shorts an outer conductor shield to an inner shield conductor of the cable successively at selected locations along an end length of the shield conductors. Some embodiments provide an RF-trap apparatus for blocking stray signals on a shielded RF cable that has two or more concentric peripheral shield conductors separated from one another by one or more electrically insulating layers, and at least one inner conductor for carrying RF signals. The RF trap apparatus includes: a first housing; and a plurality of projections configured be coupled to the first housing and to move to selectively electrically connect an outer shield conductor to an inner shield conductor by a pierce operation on the shielded RF cable.