Common Mode Filter with Embedded Resistor Feedback Loop
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Solution Overview
Problem
Conventional common mode filters fail to effectively suppress common mode noise reflection at frequencies above 2 GHz, leading to inadequate noise removal in high-speed differential signal transmission systems, and existing solutions either deteriorate at low frequencies or lack sufficient absorption capabilities.
Innovation Solution
A common mode filter design featuring spirally formed signal coils and control coils in a multilayer dielectric structure, with embedded resistors forming feedback loop circuits to control magnetic coupling and absorb common mode noise, thereby suppressing noise reflection and ensuring effective noise removal up to 2 GHz or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional common mode choke coil is used to remove common mode noise, then the common mode noise is reflected and not propagated, but the noise reflection causes malfunction in ultra-high-speed differential signal transmission circuits
Solution Approach 1:
The patent converts the harmful noise reflection into beneficial noise absorption. By introducing resistors in parallel with the common mode choke coil, the reflected noise energy is dissipated as heat in the resistors rather than being reflected back into the circuit, thereby eliminating the harmful effect while maintaining the noise removal function
Solution Approach 2:
The patent introduces resistors as intermediary elements between the common mode choke coil and the circuit. These resistors act as mediators that absorb the noise energy and prevent it from causing circuit malfunction, while being invisible to the differential signal due to their high impedance at differential mode
2Object-affected harmful factors
If resistors are inserted between differential signal balance point and ground to absorb common mode noise, then noise absorption capability is improved, but the filter becomes ineffective at low frequencies (2 GHz or less)
Solution Approach 1:
The patent merges two different noise removal mechanisms: the common mode choke coil for reflecting noise and the resistors for absorbing noise. This combination allows the filter to effectively remove noise across a wide frequency range by leveraging the strengths of both mechanisms simultaneously
Solution Approach 2:
The patent creates a composite noise filtering structure by combining reactive elements (inductors in the choke coil) and resistive elements (the resistors). This composite approach enables the filter to maintain effectiveness across both high and low frequency ranges by utilizing different physical mechanisms for noise removal
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 proposed filter configuration effectively suppresses common mode noise reflection and removes noise of 2 GHz or less, maintaining excellent magnetic coupling and simplifying external connections, while improving noise absorption characteristics without compromising differential signal transmission.
Implementation Method 1
a first control coil spirally formed in the dielectric layer so as to be sandwiched between the first and second signal coils interposing the dielectric layer, and wound in the same direction as the first signal coil, and configured to control magnetic coupling between the first and second signal coils
Implementation Method 2
a first embedded resistor formed in the dielectric layer and connected to at least one of an outer peripheral end or an inner peripheral end of the first control coil, thus forming a first feedback loop circuit via the first control coil and the first embedded resistor
Data Source
AI summary
A common mode filter suppressing a reflection of a common mode noise and sufficiently removing the common mode noise of 2 GHz or less includes: a signal coil spirally formed in a dielectric layer of a multilayer structure, and serially inserted and connected to one of the differential signal lines; a signal coil inserted and connected to the other differential signal line and formed in the dielectric layer so as to face the signal coil through the dielectric layer; a control coil formed in the dielectric layer so as to be sandwiched between the first and second signal coils interposing the dielectric layer and wound in the same direction as the signal coil; and an embedded resistor connected to at least one of an outer peripheral end or an inner peripheral end of the control coil, thus forming a feedback loop circuit by the control coil and the embedded resistor.