Active Inductor Power Over Coaxial Cable Signal Integrity
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Solution Overview
Problem
Providing power to remotely located cameras in video communication systems over coaxial cables is challenging due to interference and voltage transients caused by poorly regulated camera power supplies, which can lead to signal degradation and synchronization issues.
Innovation Solution
The use of active inductors and a current-compensation circuit to minimize voltage spikes and impedance mismatch, allowing for efficient power transmission over coaxial cables while maintaining optimal signal transfer, along with surge protection circuits to prevent damage from connection and disconnection-induced transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If power is transmitted over the coaxial cable to the remote camera, then the camera can be powered without a local power source, but voltage spikes and interference occur that degrade the video signal
Solution Approach 1:
The patent introduces an intermediary circuit at the camera end that includes a capacitor coupled between the center conductor and shield. This capacitor acts as a mediator that blocks high-frequency voltage spikes and interference from reaching the camera electronics, while allowing the lower-frequency power signal to pass through and charge the capacitor, thereby powering the camera without the harmful voltage transients
Solution Approach 2:
The patent extracts and removes the harmful voltage spike component from the power signal by using the capacitor to block high-frequency transients. The capacitor selectively filters out the harmful high-frequency interference while allowing the useful lower-frequency power transmission to continue, effectively separating the harmful aspect from the beneficial aspect of the power signal
2Ease of operation
If power is transmitted over the coaxial cable, then remote camera operation is enabled, but signal degradation occurs due to impedance mismatch
Solution Approach 1:
The patent changes the electrical parameters at the camera end by introducing a capacitor with specific capacitance value coupled between the center conductor and shield. This parameter change creates a frequency-dependent impedance that matches the coaxial cable's characteristic impedance for the operating frequency range, thereby reducing signal reflections and degradation while still allowing power transmission to occur
3Ease of operation
If active inductors are used to enable power transmission over coaxial cable, then power delivery is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex active inductor circuits with a simple passive capacitor component. Instead of using expensive and complex active inductors that require multiple active components and precise tuning, the invention uses a simple capacitor that is inexpensive, easy to implement, and provides the necessary impedance matching and voltage spike filtering functions with minimal circuit complexity
Data Source
AI summary
An image communication system includes a coaxial cable having first and second ends. A monitor station is coupled to the first end and a camera is coupled to the second end. The monitor station provides power to the camera through the cable, while the cable is also used to carry communication signals transmitted by the camera to the monitor station. The image communication system includes a first active inductor coupled to the first end and a second active inductor coupled to the second end. A current-compensation circuit may also be provided.