# US 11,309,615 B2 · Dual slot common mode noise filter

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- Number: US 11,309,615 B2
- Document ID: US11309615B2
- Status: Granted
- Kind: B2
- Application number: 16/374,515
- Filed: 2019-04-03
- Published: 2020-10-08
- Granted: 2022-04-19
- Earliest claimed: 2019-04-03
- Assignees: Hewlett Packard Enterprise Development LP
- Applicants: Hewlett Packard Enterprise Development LP
- Inventors: David Kopp; James Stewart; Karl Bois; Elene Chobanyan
- Web page: https://patentgrep.com/patent/US11309615B2

## CPC

- H01P 1/20: Frequency-selective devices, e.g. filters
- H01P 3/026: {Coplanar striplines [CPS]}
- H01P 1/20372: {Hairpin resonators}
- H01P 3/08: Microstrips; Strip lines
- H01P 11/003: {Manufacturing lines with conductors on a substrate, e.g. strip lines, slot lines}
- H01P 11/007: {Manufacturing frequency-selective devices (resonators H01P11/008)}
- H03H 7/427: {Common-mode filters (H02J3/01 and H02M1/126 takes precedence)}
- H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B)
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

A multiple-layer circuit board has a signaling layer plane, an exterior layer plane, and a ground layer plane. A pair of differential signal lines implemented as strip-lines are within the signaling layer, and propagate electromagnetic interference (EMI) along the signaling layer. A dual slot common mode noise filter may be etched within the ground layer and may include a first U-shaped etching pair comprising a first U-shaped etching and a second U-shaped etching opposing the first U-shaped etching within the ground layer plane.

## Claims

### Claim 1

An apparatus comprising:
a multiple-layer circuit board having a signaling layer plane, an exterior layer plane, and a ground layer plane;
a pair of differential signal lines implemented as strip-lines within the signaling layer, which propagate electromagnetic interference (EMI) along the signaling layer; and
a dual slot common-mode noise filter etched into the ground layer, the dual slot common-mode noise filter including a first U-shaped etching pair comprising a first U-shaped etching and a second U-shaped etching opposing the first U-shaped etching within the ground layer plane, wherein the first U-shaped etching pair is positioned above the pair of differential signal lines.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein dimensions of the first U-shaped etching differ from those of the second U-shaped etching, including at least one of a different height H and a different arm length A.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the dual slot common mode noise filter further includes a second U-shaped etching pair comprising a third U-shaped etching and a fourth U-shaped etching opposing the third U-shaped etching, the second U-shaped etching pair positioned below the differential signal lines.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein the second U-shaped etching pair is symmetrical to the first U-shaped etching pair about an XY plane formed by the inner signaling layer.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the first U-shaped etching and the second U-shaped etching are loosely coupled.

### Claim 6 (depends on 5)

The apparatus of claim 5, wherein the first U-shaped etching and the second U-shaped etching are loosely coupled such that a spacing S between the first U-shaped etching and the second U-shaped etching is greater than a fifth of a height H of the first U-shaped etching.

### Claim 7 (depends on 5)

The apparatus of claim 5, wherein the first U-shaped etching and the second U-shaped etching are loosely coupled such that a spacing S between the first U-shaped etching and the second U-shaped etching is greater than a distance D between the differential signal lines.

### Claim 8 (depends on 1)

The apparatus of claim 1, wherein the first U-shaped etching is symmetrical to the second U-shaped etching about a Y-axis perpendicular to the differential signal lines.

### Claim 9

A circuit board comprising:
a signaling layer including a pair of parallel strip-lines that propagate electromagnetic interference (EMI);
a dual slot common-mode noise filter etched into the ground layer, the dual slot common-mode noise filter including a first bracket etching pair comprising a first bracket etching comprising a first edge and a second edge parallel to one another, and a third edge perpendicular to the first edge and the second edge and connecting corresponding ends of the first edge and the second edge, and a second bracket etching opposing the first bracket etching about a Y-axis perpendicular to the pair of strip-lines, wherein the first bracket etching pair is positioned above the pair of differential signal lines.

### Claim 10 (depends on 9)

The circuit board of claim 9, wherein the first edge and second edge are of equal length.

### Claim 11 (depends on 9)

The circuit board of claim 9, wherein the first bracket etching and second bracket etching are positioned such that the first bracket etching is symmetrical about an X-axis centered between the pair of strip-lines and the second bracket etching is symmetrical about an X-axis centered between the pair of strip-lines.

### Claim 12 (depends on 9)

The circuit board of claim 9, wherein the third edge is of a greater length than the first edge and second edge.

### Claim 13 (depends on 9)

The circuit board of claim 9, wherein the dual slot common-mode noise filter further includes a second bracket etching pair comprising a third bracket etching and a fourth bracket etching opposing the third bracket etching, the second bracket etching pair positioned below the differential signal lines.

### Claim 14 (depends on 13)

The circuit board of claim 13, wherein the second bracket etching pair is symmetrical to the first bracket etching pair about an XY plane formed by the inner signaling layer.

### Claim 15 (depends on 9)

The circuit board of claim 9, wherein the first bracket etching pair and the second bracket etching pair are loosely coupled.

### Claim 16 (depends on 15)

The circuit board of claim 15, wherein the first bracket etching and the second bracket etching are loosely coupled such that a spacing S between the first bracket etching and the second bracket etching is greater than a fifth of a height H of the first bracket etching.

### Claim 17

A method comprising:
fabricating an inner signaling layer of the circuit board to include a pair of differential signal lines that convey electromagnetic interference (EMI) along the inner signaling layer; and
fabricating a ground layer of a multiple-layer circuit board, including etching a dual slot common-mode noise filter into the ground layer, wherein etching the dual slot common-mode noise filter includes etching, within the ground plane, a first U-shaped etching pair comprising a first U-shaped etching and a second U-shaped etching opposing the first U-shaped etching, wherein the first U-shaped etching pair and the second U-shaped etching pair are positioned symmetrically about an XY-plane formed by the inner signaling layer.

### Claim 18 (depends on 17)

The method of claim 17, wherein etching the dual slot common-mode noise filter further includes etching, within the ground plane, a second U-shaped etching pair comprising a third U-shaped etching and a fourth U-shaped etching opposing the third U-shaped etching.