A filter apparatus, which includes a feedback active common-mode filter and a feed-forward active common-mode filter, the feedback active common-mode filter includes a common-mode noise detection component and a first filter circuit, and the feed-forward active common-mode filter includes the common-mode noise detection component and a second filter circuit, where the first filter circuit is connected between the common-mode noise detection component and the device, and performs feedback filtering on a first common-mode noise signal, to obtain a second common-mode noise signal; the common-mode noise detection component is connected between the first filter circuit and the second filter circuit, detects the second common-mode noise signal, and provides the second filter circuit with the second common-mode noise signal; and the second filter circuit is connected between an external power source and the common-mode noise detection component, and performs feed-forward filtering on the second common-mode noise signal.

A coil component includes a body including coil patterns and a plurality of trenches; and external electrodes electrically connected to the coil patterns. The plurality of trenches include a magnetic material, and at least one edge of a trench disposed outside of an outermost coil pattern among the coil patterns has a same shape as an outside boundary portion of the outermost coil pattern adjacent thereto.

A filter for electromagnetic noise comprising: a printed circuit board (5) having conductor tracks, having a first side and having a second side opposite the first side; a first busbar (1), which is secured on the first side of the printed circuit board (5) and is electrically connected to at least one of the conductor tracks; and a second busbar (2), which is secured on the second side of the printed circuit board (5) and is electrically connected to at least one of the conductor tracks. The printed circuit board (5) is arranged between the first busbar (1) and the second busbar (2) for the insulation thereof.

A LAN filtering circuit is discloses. The LAN filtering circuit includes an isolation transformer and a common-mode chock. The isolation transformer includes a first winding and a second winding coupling to each other. The first winding has a first tap, a second tap, and a center tap. A distance between the first tap and the second tap is not only larger than a distance between the first tap and the center tap but also larger than a distance between the second tap and the center tap. The common-mode chock includes a first input port, a second input port, and an input port arranged in a sequence order, the first tap is electrically connected to the first input port, the second tap is electrically connected to the second input port, and the center tap is electrically connected to the input port.

Disclosed are a two-stage noise filter, in which two filters are integrated, and an electronic device including the same. The two-stage noise filter includes a core configured to include a primary side and a secondary side opposite to the primary side; a first filter configured to include a first coil wound on the primary side of the core and a second coil wound on the secondary side of the core; a second filter configured to include a third coil wound on the primary side of the core in series with the first coil and a fourth coil wound on the secondary side of the core in series with the second coil; and an impedance balancer configured to keep a balance of impedance between the first and second filters.

A common mode noise filter includes first to fourth insulator layers stacked in a stacking direction and first to third coils provided on the first to fourth insulator layers independently of one another. The first coil includes a first coil conductor provided on the first insulator layer and a second coil conductor provided on the fourth insulator layer and connected to the first coil conductor. The second coil is provided on the second insulator layer. The third coil is provided on the third insulator layer. The first coil conductor overlaps the second coil viewing from above. At least a part of the second coil overlaps at least a part of the third coil viewing from above. The second coil conductor overlaps the third coil viewing from above.

A differential transmission line includes a sheath, a first conductive structure, a second conductive structure, and a resistive layer. The first conductive structure is disposed along the differential transmission line and within the sheath, and contributes to formation of a three-dimensional electromagnetic field. The second conductive structure is disposed along the differential transmission line and within the sheath, and contributes to formation of the three-dimensional electromagnetic field. The resistive layer is aligned to be substantially perpendicular to an electric field component of a first mode of the three-dimensional electromagnetic field, and to provide absorption of an electric field component of a second mode of the three-dimensional electromagnetic field.

In a filter component with improved attenuation characteristics for common mode noise, an LC series resonance circuit disposed in each of a plurality of shunt circuits is connected at a first end to a first line and is grounded at a second end. The LC series resonance circuit disposed in each of the shunt circuits is grounded at a first end and is connected at a second end to a second line. With this configuration, the LC series resonance circuits resonate reliably so as to define attenuation poles. Accordingly, the resonant frequency of each of the LC series resonance circuits is set to be a frequency that effectively attenuates common mode noise.

In a communications system that conducts differential data via a pair of wires, AC common mode noise is undesirably coupled to the wires in a noisy environment. A hybrid common mode choke (HCMC) attenuates the AC common mode noise while passing the differential data to a PHY. The HCMC includes a CMC (windings with the same polarity) and a differential mode choke (windings with opposite polarities). The CMC attenuates the AC common mode noise, and the DMC passes the attenuated AC common mode noise to termination circuitry to eliminate it. Also disclosed is a technique for Kelvin sensing the DC voltage at the pair of wires, in a PoDL system, by detecting the voltage on wires that do not carry DC current, so as to provide a more accurate measurement.

Methods and apparatus for capacitively isolated first communication channels with common mode noise suppression. In embodiments, a driver on the first circuit transmits a data signal on the first communication channel to a receiver on the second circuit. A common mode suppression circuit on the second circuit is coupled to the receiver, output of the suppression circuit is coupled to a node between the first capacitor and the resistor network and an input is coupled to a ground of the first circuit via a second capacitor. The common mode suppression circuit is configured to detect a common mode movement signal due to a noise pulse to the second circuit on the input and generate a corresponding signal on the output to maintain a current level across the resistor network for suppressing common mode noise from the pulse.