# US 10,122,057 B2 · Bandwidth increase method for differential passive elements

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- Number: US 10,122,057 B2
- Document ID: US10122057B2
- Status: Granted
- Kind: B2
- Application number: 15/275,399
- Filed: 2016-09-25
- Published: 2018-03-29
- Granted: 2018-11-06
- Earliest claimed: 2016-09-25
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Oded Katz; Run Levinger
- Web page: https://patentgrep.com/patent/US10122057B2

## CPC

- H01P 3/02: with two longitudinal conductors
- H01P 3/026: {Coplanar striplines [CPS]}
- H03H 7/42: Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns
- 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

This invention relates to assemblies and processes for increasing the bandwidth of differential passive elements. The use of a floating plane in differential transmission lines is disclosed. One such assembly is a broadband balun having high even mode effective impedance, thus degrading the even-mode propagation or matching, and maintaining the desired odd mode effective impedance. Other assemblies can include line couplers, hybrid couplers, RF chokes with back-to-back baluns, and other elements, such as balanced filters.

## Claims

### Claim 1

An apparatus comprising:
a first ground plane;
a set of signal lines comprising a positive signal line and a negative signal line; and
a first floating plane between the signal lines and the first ground plane, wherein the first floating plane is configured to provide an even mode impedance of the signal lines that is higher than an odd mode impedance of the signal lines.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the positive signal line, the negative signal line, and the first floating plane are configured to create a cross parasitic capacitance at an odd mode.

### Claim 3 (depends on 1)

The apparatus of claim 1, further comprising a grounded side shield line that is coplanar with the positive signal line.

### Claim 4 (depends on 1)

The apparatus of claim 1, further comprising a silicon substrate layer below the first ground plane.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the set of signal lines comprises copper.

### Claim 6 (depends on 1)

The apparatus of claim 1, further comprising a dielectric substrate between the first ground plane and the set of signal lines.

### Claim 7 (depends on 6)

The apparatus of claim 6, wherein the dielectric substrate is selected from the group consisting of ceramic, plastic, polymer, and synthetic fiber.

### Claim 8 (depends on 1)

The apparatus of claim 1, further comprising a second ground plane above the set of signal lines and a second floating plane between the set of signals line and the second ground plane.

### Claim 9

An apparatus comprising:
a differential transmission line comprising a positive signal line, a negative signal line, and a ground plane; and
a floating plane coplanar with the ground plane, wherein the floating plane is configured to provide an even mode impedance of the differential transmission line that is higher than an odd mode impedance of the differential transmission line.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein the positive signal line, the negative signal line, and the floating plane are configured to create a cross parasitic capacitance at an odd mode.

### Claim 11 (depends on 9)

The apparatus of claim 9, further comprising at least one side shield line that is coplanar with the positive signal line.

### Claim 12 (depends on 9)

The apparatus of claim 9, further comprising a silicon substrate layer below the ground plane.

### Claim 13

A balun comprising:
a substrate layer;
a ground plane formed on a first surface of the substrate layer;
a set of signal lines comprising a first signal line having a first end connected to a first port and second end connected to a second port, a second signal line having a third end connected to the ground plane a second port and a fourth end connected to the ground plane, and a third signal line having a fifth end connected to the ground plane and a sixth end connected to a third port; and
a floating plane located between the set of signal lines and the ground plane, wherein the floating plane is configured to provide an even mode impedance of the signal lines that is higher than an odd mode impedance of the signal lines.

### Claim 14 (depends on 13)

The balun of claim 13, wherein the second signal line and third signal line are substantially coplanar.

### Claim 15 (depends on 13)

The balun of claim 13, further comprising a silicon substrate layer below the ground plane.

### Claim 16 (depends on 13)

The balun of claim 13, wherein the set of signal lines comprises copper.

### Claim 17 (depends on 13)

The balun of claim 13, further comprising a dielectric substrate between the first ground plane and the set of signal lines.

### Claim 18 (depends on 13)

The balun of claim 13, wherein the dielectric substrate is selected from the group consisting of ceramic, plastic, polymer, and synthetic fiber.

### Claim 19 (depends on 13)

The balun of claim 13, wherein the set of signal lines and the floating plane are configured to create a cross parasitic capacitance at an odd mode.