Isolating differential transmission lines

Patent metadata

Field	Value
Publication number	US-9253875-B2
Application number	US-201313895101-A
Country	US
Kind code	B2
Filing date	May 15, 2013
Priority date	May 15, 2013
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

An apparatus includes a first differential transmission line and a second differential transmission line. The second differential transmission line is parallel to the first differential transmission line through an overlap region. The first differential transmission line includes a first line and a second line. The first differential transmission line includes N crossovers along the first differential transmission line through the overlap region at which the first line and the second line switch lanes with each other. N is equal to 1+INT {L/(λ/C)}, where L is a length of the overlap region, λ is a wavelength of a differential signal carried by the first or second differential transmission line, C is a constant, and INT {L/(λ/C)} is {L/(λ/C)} rounded down to the nearest integer.

First claim

What is claimed is:

1. An apparatus comprising:
a first differential transmission line configured to carry a first differential signal;
a second differential transmission line, parallel to the first differential transmission line to define an overlap region there between, and configured to carry a second differential signal;
wherein:
the first differential transmission line includes a first line and a second line;
the first differential transmission line includes N crossovers along the first differential transmission line through the overlap region at which the first line and the second line switch lanes with each other; and
N is equal to 1+INT {L/(λ/C)}, where L is a length of the overlap region, κ is a wavelength of the first differential signal or a wavelength of the second differential signal having the highest frequency of the first differential signal or the second differential signal, C is a number in a range from 10 to 20, and INT {L/(λ/C)} is {L/(λ/C)} rounded down to the nearest integer.

2. The apparatus of claim 1 , wherein:
the first differential transmission line has a length greater than one-tenth of the wavelength of the first differential signal; and
the second differential transmission line has a length greater than one-tenth of the wavelength of the second differential signal.

3. The apparatus of claim 2 , wherein the length of the first differential transmission line and the length of the second differential transmission line are each in a range from 1.3 millimeters to 22 millimeters.

4. The apparatus of claim 1 , wherein each of the first differential transmission line and the second differential transmission line is configured to carry a corresponding signal having a frequency in a range from about 900 Megahertz (MHz) to about 15 gigahertz (GHz).

5. The apparatus of claim 1 , wherein:
the second differential transmission line includes a first line and a second line;
the second differential transmission line includes N−1 crossovers at which the first line and the second line of the second differential transmission line switch lanes with each other.

6. The apparatus of claim 5 , wherein each of the N−1 crossovers of the second differential transmission line is located along the second differential transmission line at a corresponding location that is about equidistant between two of the N crossovers in a corresponding sequential pair of the N crossovers of the first differential transmission line.

7. The apparatus of claim 5 , wherein:
the lanes of first differential transmission line includes first and second lanes;
the second differential transmission line includes first and second lanes; and
the first and second lanes of the first differential transmission line and the first and second lanes of the second differential transmission line are parallel and arranged in order from the first lane of the first differential transmission line to the second lane of the first differential transmission line to the first lane of the second differential transmission line to the second lane of the second differential transmission line; and
the N−1 crossovers of the second differential transmission line mirror the N crossovers of the first differential transmission line such that:
if each of the N crossovers in the first differential transmission line includes a line in the first lane of the first differential transmission line crossing over a line in the second lane of the first differential transmission line, then each of the N−1 crossovers in the second differential transmission line includes a line in the second lane of the second differential transmission line crossing over a line in the first lane of the second differential transmission line; or
if each of the N crossovers in the first differential transmission line includes a line in the second lane of the first differential transmission line crossing over a line in the first lane of the first differential transmission line, then each of the N−1 crossovers in the second differential transmission line includes a line in the first lane of the second differential transmission line crossing over a line in the second lane of the second differential transmission line.

8. A method of operating a system having a plurality of differential transmission lines, the method comprising:
driving a first differential signal having a first component and a second component on a first differential transmission line including a first line and a second line, the first differential transmission line having N crossovers at which the first line and the second line of the first differential transmission line switch lanes with each other; and
driving a second differential signal having a first component and a second component on a second differential transmission line including a first line and a second line, wherein the second differential transmission line is parallel to the first differential transmission line through an overlap region;
wherein N is equal to 1+INT {L/(λ/C)}, where L is the length of the overlap region, λ is a wavelength of the first differential signal or a wavelength of the second differential signal having the highest frequency of the first differential signal or the second differential signal, C is a number in a range from 10 to 20, and INT {L/(λ/C)} is {L/(λ/C)} rounded down to the nearest integer.

9. The method of claim 8 , wherein each of the first differential signal and the second differential signal has a frequency in a range from about 900 Megahertz (MHz) to about 15 gigahertz (GHz).

10. The method of claim 8 , further comprising:
carrying the first component of the first differential signal on the first line of the first differential transmission line such that the first component of the first differential signal switches lanes from a first lane to a second lane or from the second lane to the first lane at each of the N crossovers; and
carrying the second component of the first differential signal on the second line of the first differential transmission line such that the second component of the first differential signal switches lanes from the second lane to the first lane or from the first lane to the second lane at each of the N crossovers.

11. The method of claim 8 , wherein the second differential transmission line has, in the overlap region, N−1 crossovers at which the first line and the second line of the second differential transmission line switch lanes with each other.

12. The method of claim 11 , wherein:
a first one of the N crossovers of the first differential transmission line is positioned along the first differential transmission line at a distance of about (L/N)/2 from an end of the overlap region;
the N crossovers of the first differential transmission line are spaced along the first differential transmission line at a spacing of about L/N beginning from the first one of the N crossovers;
a first one of the N−1 crossovers of the second differential transmission line is positioned along the second differential transmission line at a distance of about L/N from the end of the overlap region; and
the N−1 crossovers of the second differential transmission line are spaced along the second differential transmission line at a spacing of about L/N beginning from the first one of the N−1 crossovers.

13. The method of claim 11 , wherein:
the lanes of the first differential transmission line include a first lane and a second lane;
the lanes of the second differential transmission line include a first lane and a second lane;
within the overlap region, the lanes are parallel and arranged in order from the first lane of the first differential transmission l

Assignees

• Intel Ip Corp

Inventors

• Lent Lillian
• Tsai Chi-Taou

Classifications

• H10W44/223

  Differential pair signal lines · CPC title

• H10W44/20

  at high-frequency [HF] or radio frequency [RF] · CPC title

• H04B3/32 Primary

  Reducing cross-talk, e.g. by compensating · CPC title

• H01L2924/0002

  Electricity · mapped topic

• H01L2924/00

  Electricity · mapped topic