Capacitive RF Rotary Switch for Low Passive Intermodulation
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Solution Overview
Problem
Existing RF coaxial switches face limitations in reducing passive intermodulation (PIM) due to mechanical contact force constraints and contact wear, leading to a limited lifetime and increased maintenance requirements.
Innovation Solution
A capacitive coupled RF switch design with rotatable and stationary pads that eliminate mechanical contacts, utilizing capacitive coupling for signal transmission, allowing for low PIM and extended switch lifetime with minimal maintenance, and incorporating a drive mechanism for precise positioning and improved coupling capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical contacts are used in RF switches to achieve signal transmission, then the switch can perform basic switching function, but passive intermodulation increases and lifetime is limited due to contact wear
Solution Approach 1:
The patent replaces mechanical contact-based signal transmission with a capacitive coupling mechanism. The signal is transmitted through electric field coupling between stationary and rotatable pads without direct mechanical contact, thereby eliminating contact wear and reducing passive intermodulation while maintaining switching functionality.
Solution Approach 2:
The patent introduces capacitive coupling as an intermediary mechanism between the stationary and rotatable pads. This intermediary allows signal transmission through electric field coupling without direct mechanical contact, solving the contradiction between maintaining signal transmission and eliminating contact wear.
2Object-generated harmful factors
If contact force is increased to reduce passive intermodulation in mechanical contact switches, then PIM decreases temporarily, but mechanical limits are reached and contacts wear faster
Solution Approach 1:
The patent eliminates the need for mechanical contact force by using capacitive coupling. The signal transmission relies on electric field coupling rather than mechanical pressure, allowing PIM reduction without increasing contact force and thereby extending component lifetime.
3Object-generated harmful factors
If capacitive coupling is used to eliminate mechanical contacts, then passive intermodulation is reduced and lifetime is extended, but precise pad alignment and coupling capacitance maintenance are required
Solution Approach 1:
The patent employs spring-loaded pads that automatically adjust and maintain optimal coupling capacitance through elastic force. This self-adjusting mechanism compensates for manufacturing tolerances and wear, maintaining precise alignment without requiring extremely high manufacturing precision.
Solution Approach 2:
The patent uses elastic materials with specific mechanical properties to create pads that can dynamically adjust their position and coupling capacitance. This allows the system to maintain optimal electrical characteristics despite variations in manufacturing precision or operational wear.
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 capacitive coupled RF switch effectively reduces passive intermodulation, extends the switch's operational lifetime, and minimizes maintenance needs by maintaining precise coupling capacitance and reproducible coupling characteristics through stiff material construction and precise pad alignment.
Implementation Method 1
The switching elements are rotated about a rotation axis and interact with stationary coupling elements, forming a capacitive coupled switch. The capacitive coupled switch does not have any mechanical or galvanic contacts and therefore does not generate any passive intermodulation of RF signals.
Data Source
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AI summary
A low passive intermodulation (PIM) RF rotary switch comprises a plurality of center conductors connected to stationary pads, at least two rotatable pads connected by a rotatable pad bridge. Depending on the switching state at least two stationary pads are in close proximity to at least two rotatable pads, thus generating a RF signal connection between the center conductors via the stationary and rotatable pads.