DIFFERENTIAL TRANSMISSION LINE

• US 20080266019A1
• Filed: 04/24/2008
• Published: 10/30/2008
• Est. Priority Date: 04/24/2007
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Hamada, Seiji, Fusayasu, Hirotsugu, Tanimoto, Shinichi, Matsubara, Ryo
• Granted Patent: US 7,741,876 B2
• Time in Patent Office: Days
• US Class Current: 333/12
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H04B 3/34 by systematic interconnection of lengths of cable during laying; by addition of balancing components to cable during laying
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H05K 1/0245 Lay-out of balanced signal pairs, e.g. differential lines or twisted lines
• CPC Class Codes: H05K 1/0248 Skew reduction or using delay lines
• CPC Class Codes: H05K 1/0298 Multilayer circuits
• CPC Class Codes: H05K 2201/09236 Parallel layout
• CPC Class Codes: H05K 2201/09672 Superposed layout, i.e. in different planes

Abstract

A differential transmission line that has three or more signal lines and with which there is little unwanted radiation noise is provided. The differential transmission line 2 is provided with three signal lines 2a, 2b, and 2c that transmit differential signals from a differential driver IC1 to a differential receiver IC3, and the majority of the signal lines 2a, 2b, and 2c is provided in conductor layers T2 and T3 of a printed circuit board 4. The signal lines 2a, 2b, and 2c are provided with a signal line parallel segment, a signal line route length adjustment segment that is on the differential driver IC1 side and that connects from differential signal output terminals 1Ea, 1Eb, and 1Ec in the differential driver IC1 to the signal line parallel segment, and a signal line route length adjustment segment that is on the differential receiver IC3 side and that connects from the signal line parallel segment to differential signal input terminals in the differential receiver IC3, wherein the signal lines 2a, 2b, and 2c are formed such that their signal line route length adjustment segments on the differential driver IC1 side are equal in length to one another.

Claims

1. A differential transmission line that is provided on a printed circuit board furnished with a plurality of laminated conductor layers, and that is furnished with at least three signal lines that transmit a differential signal from a driver unit on the printed circuit board to a receiver unit on the printed circuit board,

wherein the at least three signal lines are provided in at least two conductor layers of the plurality of conductor layers, and

wherein the signal lines comprise:

(a) a signal line parallel segment in which the signal lines run parallel;

(b) a first signal line route length adjustment segment, connecting from a differential signal output terminal in the driver unit to the signal line parallel segment, for adjusting the length of the signal line; and

(c) a second signal line route length adjustment segment, connecting from the signal line parallel segment to a differential signal input terminal in the receiver unit, for adjusting the length of the signal line; and

wherein the signal lines are formed such that they are equal in length to one another in the first signal line route length adjustment segment.

2. The differential transmission line according to claim 1,

wherein the signal lines are formed such that they are equal in length to one another in the second signal line route length adjustment segment.

3. The differential transmission line according to claim 1,

wherein the differential signal output terminals of the driver unit are disposed in the longitudinal direction of the signal lines such that the output terminal that is connected to the signal line that is provided in the conductor layer most removed from the driver unit is relatively closer from the receiver unit than the output terminals that are connected to the signal lines provided in other conductor layers.

4. The differential transmission line according to claim 3,

wherein the differential transmission line is provided with three signal lines;

wherein first and second signal lines of the three signal lines are provided in the first conductor layer of the plurality of conductor layers, separated from one another by a predetermined first distance; and

wherein a third signal line of the three signal lines is provided in the second conductor layer of the plurality of conductor layers, separated from the first signal line and the second signal line by a predetermined second distance.

5. The differential transmission line according to claim 3,

wherein the driver unit is provided with three output terminals for differential signals;

and

wherein the three output terminals are disposed parallel such that they are separated from one another by a predetermined same distance.

6. The differential transmission line according to claim 3,

wherein at least some of the three signal lines are disposed parallel such that they are separated from one another by a predetermined same distance.

7. The differential transmission line according to claim 1,

wherein the differential transmission line is provided with three signal lines;

wherein the driver unit is provided with three output terminals for differential signals;

wherein first and second signal lines of the three signal lines are provided in the first conductor layer of the plurality of conductor layers, separated from one another by a predetermined distance;

wherein a third signal line of the three signal lines is provided in the second conductor layer of the plurality of conductor layers, separated from the first signal line and the second signal line by the predetermined distance; and

wherein the three output terminals are disposed parallel such that the distance between the first and the second conductor layers is equal to the distance to a center point between the output terminal that is connected to the third signal line and the output terminals that are connected to the first and the second signal lines.

8. The differential transmission line according to claim 1,

wherein the conductor layers in which are formed the signal lines other than the signal line that is provided in the conductor layer that is farthest removed from the driver unit include signal line return portions for extending the length of the other signal lines.

9. The differential transmission line according to claim 1,

wherein the printed circuit board is provided with at least four laminated conductor layers, and

two of the conductor layers are formed as ground conductors;

wherein the signal lines are formed as pattern conductors in some of the at least two conductor layers that are not the ground conductors; and

wherein all of the signal lines are disposed sandwiched by the two ground conductors.

16. A differential transmission line according to claim 1, that is used in a multiple differential transmission system.

17. The differential transmission line according to claim 16,

wherein the multiple differential transmission system comprises a signal transmitter, and a signal receiver;

wherein

the signal transmitter;

is connected to the differential transmission line, which has first, second, and third signal lines; and

comprises;

a first differential driver that transmits a first output signal, and an inverted first output signal whose phase is inverted compared to the first output signal, in response to a first bit information signal;

a second differential driver that transmits a second output signal, and an inverted second output signal whose phase is inverted compared to the second output signal, in response to a second bit information signal; and

a third differential driver that transmits a third output signal, and an inverted third output signal whose phase is inverted compared to the third output signal, in response to a third bit information signal;

wherein the signal transmitter synthesizes the first output signal and the inverted third output signal and outputs the result to the first signal line, synthesizes the second output signal and the inverted first output signal and outputs the result to the second signal line, and synthesizes the third output signal and the inverted second output signal and outputs the result to the third signal line; and

wherein an absolute value of a binary signal voltage of the first output signal and an absolute value of a binary signal voltage of the second output signal are identical, and an absolute value of a binary signal voltage of the third output signal and the absolute value of the binary signal voltage of the first output signal are different; and

wherein

the signal receiver;

is connected to the differential transmission line, which has first, second, and third signal lines; and

comprises;

a first differential receiver that detects a polarity of a terminal voltage that occurs at a first terminal resistor that is connected between the first signal line and the second signal line, and outputs the result of this detection as the first bit information signal;

a second differential receiver that detects a polarity of a terminal voltage that occurs at a second terminal resistor that is connected between the second signal line and the third signal line, and outputs the result of this detection as the second bit information signal;

a third differential receiver that detects a polarity of a terminal voltage that occurs at a third terminal resistor that is connected between the third signal line and the first signal line, and outputs the result of this detection as the third bit information signal;

a comparison unit for determining whether or not the absolute value of the third terminal voltage that occurs at the third terminal resistor exceeds a predetermined threshold voltage; and

a control unit for outputting the first, second, and third bit information signals that are output from the first, second, and third differential receivers, when the absolute value of the third terminal voltage exceeds the predetermined threshold voltage, and outputs a 0 or 1 for all of the first, second, and third bit information signals, based on the third bit information signal that is output from the third differential receiver, when the absolute value of the third terminal voltage does not exceed the predetermined threshold voltage;

wherein the threshold voltage is set so that it is larger than the absolute value of the difference between the absolute value of the binary signal voltage of the first output signal and the absolute value of the binary signal voltage of the third output signal.

10. A differential transmission line that is provided on a printed circuit board, and that is furnished with at least three signal lines that transmit a differential signal from a driver unit to a receiver unit,

wherein the at least three signal lines are disposed parallel to one another;

and

wherein in a cross section that is perpendicular to a longitudinal direction of the differential transmission line, the at least three signal lines are disposed at a substantially equal spacing on a same circumference.

11. The differential transmission line according to claim 10,

wherein in a cross section that is perpendicular to the longitudinal direction of the differential transmission line, each pair of two adjacent signal lines, of the three signal lines, has a cross-sectional shape that is symmetrical with respect to a center line between that pair of signal lines.

12. The differential transmission line according to claim 11,

wherein each signal line has a circular cross-sectional shape.

13. The differential transmission line according to claim 11,

wherein the differential transmission line comprises three signal lines;

and

wherein each signal line has a substantially equilateral triangular cross-sectional shape.

14. The differential transmission line according to claim 10,

wherein the printed circuit board is a multilayer printed circuit board that includes at least four laminated conductor layers;

wherein two of the conductor layers serve as ground conductors;

wherein the signal lines are formed as pattern conductors in some of the at least two conductor layers that are not the ground conductors; and

wherein all of the signal lines are disposed sandwiched by the two ground conductors.

18. A differential transmission line according to claim 10, that is used in a multiple differential transmission system.

15. A differential transmission line that is provided on a double-sided printed circuit board, and that is furnished with at least three signal lines that transmit a differential signal from driver a unit to receiver a unit,

wherein one of the signal lines is formed as a strip conductor of a coplanar line in one of the conductor layers of the double-sided printed circuit board, and the other two signal lines are formed as strip conductors of a coplanar line in the other conductor layer of the double-sided printed circuit board;

wherein the three signal lines are disposed parallel to one another; and

wherein in a cross section that is perpendicular to the longitudinal direction of the differential transmission line, the three signal lines are disposed located substantially at the apexes of an equilateral triangle.

19. A differential transmission line according to claim 15, that is used in a multiple differential transmission system.