Resistive Wye Splitter for MoCA Band Isolation
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Solution Overview
Problem
Legacy splitters used in cable television (CATV) and multimedia over coax alliance (MoCA) networks, which rely on ferrite transformers, face issues with increased input-to-output losses and high output-to-output isolation when extending bandwidth or adding intermediate circuits, leading to signal loss and notches in the MoCA band.
Innovation Solution
A resistive Wye-type splitter design is introduced, featuring equal series resistance and impedance paths between inputs and outputs, with capacitors and resistors connected in series to manage bandwidth between 1125 MHz and 1675 MHz, reducing isolation and improving in-band signal quality without using ferrite materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ferrite transformers are used in legacy splitters, then broadband circuit with low input-to-output loss is achieved, but output-to-output isolation becomes excessively high causing signal loss and notches in the MoCA band
Solution Approach 1:
The patent removes ferrite transformers from the splitter circuitry and replaces them with a resistive Wye-type network. This extraction eliminates the source of high isolation and notching problems while maintaining the desired signal distribution function. The resistive network inherently provides lower isolation without creating the problematic frequency-dependent behavior of ferrite materials.
Solution Approach 2:
The patent changes the fundamental operating parameters by using pure resistive elements with specific resistance values (e.g., 75 ohms) instead of ferrite transformers. This parameter change transforms the isolation characteristic from excessively high and frequency-dependent to moderately low and flat across the MoCA band, eliminating signal loss and notches while maintaining acceptable input-to-output loss.
2Adaptability or versatility
If bandwidth is extended in ferrite core splitters, then broader frequency coverage is achieved, but input-to-output losses increase and isolation becomes excessively high
Solution Approach 1:
The patent substitutes the ferrite magnetic core system with a resistive electrical network. This replacement eliminates the frequency-dependent magnetic properties of ferrite that cause increasing losses and isolation with bandwidth extension. The resistive network maintains consistent performance across the MoCA band without the degradation seen in ferrite-based designs.
3Reliability
If intermediate circuits are added to ferrite splitters, then performance is improved, but device complexity increases and isolation becomes excessively high
Solution Approach 1:
Instead of adding intermediate circuits to improve ferrite splitter performance, the patent inverts the approach by using a simple resistive Wye-type network that inherently provides the desired performance characteristics. This inversion eliminates the need for complex intermediate circuits while achieving lower, more appropriate isolation levels and avoiding notches in the MoCA band.
Data Source
AI summary
A splitter for use in an in-home network includes an input and a plurality of outputs including at least a first output and a second output. A split point is between the input and the plurality of outputs. A first resistor and a first capacitor are connected in series between the input and the split point. A second resistor and a second capacitor are connected in series between the split point and the first output. A third resistor and a third capacitor are connected in series between the split point and the second output. The input, the first output, and the second output form a resistive Wye-type splitter. A first path exists between the input and the first output. A second path exists between the input and the second output. The first path and the second path have a substantially equal series resistance, series impedance, insertion loss, and isolation.