U.S. patent application number 09/400025 was filed with the patent office on 2002-01-31 for emc characteristics of a printed circuit board.
Invention is credited to HAILEY, JEFFERY C..
Application Number | 20020012240 09/400025 |
Document ID | / |
Family ID | 23581921 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012240 |
Kind Code |
A1 |
HAILEY, JEFFERY C. |
January 31, 2002 |
EMC CHARACTERISTICS OF A PRINTED CIRCUIT BOARD
Abstract
An apparatus for use with data processing systems. The apparatus
provides a split metallic conducting plane having a split formed by
a substantially-dielectric-filled moat spanning a width of a side
of a first metallic conducting part running substantially parallel
to a side of a second metallic conducting part, with the moat
structured such that the side of the first metallic part has at
least two indentations and such that the side of the second
metallic part has at least two indentations, and where a metallic
trace is located proximate to the split metallic conducting
plane.
Inventors: |
HAILEY, JEFFERY C.; (AUSTIN,
TX) |
Correspondence
Address: |
SKJERVEN MORRILL MACPHERSON LLP
25 METRO DRIVE
SUITE 700
SAN JOSE
CA
95110
US
|
Family ID: |
23581921 |
Appl. No.: |
09/400025 |
Filed: |
September 21, 1999 |
Current U.S.
Class: |
361/818 ; 333/12;
361/748; 361/760 |
Current CPC
Class: |
H05K 2201/09663
20130101; H05K 2201/09245 20130101; H05K 1/0216 20130101; H05K
2201/093 20130101 |
Class at
Publication: |
361/818 ; 333/12;
361/760; 361/748 |
International
Class: |
H05K 009/00; H04B
003/32 |
Claims
What is claimed is:
1. A printed circuit board comprising: a split metallic conducting
plane having a split formed by a substantially-dielectric-filled
moat spanning a width of a side of a first metallic conducting part
running substantially parallel to a side a second metallic
conducting part; the moat structured such that the side of the
first metallic part has at least two indentations and such that the
side of the second metallic part has at least two indentations; and
a metallic trace located proximate to said split metallic
conducting plane.
2. The printed circuit board of claim 1, wherein the moat
structured such that the side of the first metallic part has at
least two indentations and such that the side of the second
metallic part has at least two indentations further comprises: the
moat structured as a repeating rectangular structure.
3. The printed circuit board of claim 1, wherein the moat
structured such that the side of the first metallic part has at
least two indentations and such that the side of the second
metallic part has at least two indentations further comprises: the
moat structured as a repeating triangular structure.
4. The printed circuit board of claim 1, wherein the moat
structured such that the side of the first metallic part has at
least two indentations and such that the side of the second
metallic part has at least two indentations further comprises: the
moat structured as a repeating T-shaped structure.
5. The printed circuit board of claim 1, wherein the moat
structured such that the side of the first metallic part has at
least two indentations and such that the side of the second
metallic part has at least two indentations further comprises: the
moat structured as a repeating arrow-shaped structure.
6. The printed circuit board of claim 1, wherein said metallic
trace located proximate to said split metallic conducting plane
further comprises: said metallic trace located on a plane
substantially parallel to the split metallic conducting plane.
7. The printed circuit board of claim 1, wherein said metallic
trace located proximate to said split metallic conducting plane
further comprises: said metallic trace located substantially
coplanar with the split metallic conducting plane.
8. A computer system comprising: a microprocessor mounted on at
least one printed circuit board; the at least one printed circuit
board comprising a split metallic conducting plane having a split
formed by a substantially-dielectric-filled moat spanning a width
of a side of a first metallic conducting part running substantially
parallel to a side a second metallic conducting part; the moat
structured such that the side of the first metallic part has at
least two indentations and such that the side of the second
metallic part has at least two indentations; and a metallic trace
located proximate to said split metallic conducting plane.
9. The computer system of claim 8, wherein the moat structured such
that the side of the first metallic part has at least two
indentations and such that the side of the second metallic part has
at least two indentations further comprises: the moat structured as
a repeating rectangular structure.
10. The computer system of claim 8, wherein the moat structured
such that the side of the first metallic part has at least two
indentations and such that the side of the second metallic part has
at least two indentations further comprises: the moat structured as
a repeating triangular structure.
11. The computer system of claim 8, wherein the moat structured
such that the side of the first metallic part has at least two
indentations and such that the side of the second metallic part has
at least two indentations further comprises: the moat structured as
a repeating T-shaped structure.
12. The computer system of claim 8, wherein the moat structured
such that the side of the first metallic part has at least two
indentations and such that the side of the second metallic part has
at least two indentations further comprises: the moat structured as
a repeating arrow-shaped structure.
13. The computer system of claim 8, wherein said metallic trace
located proximate to said split metallic conducting plane further
comprises: said metallic trace located on a plane substantially
parallel to the split metallic conducting plane.
14. The computer system of claim 8, wherein said metallic trace
located proximate to said split metallic conducting plane further
comprises: said metallic trace located substantially coplanar with
the split conducting plane.
15. The computer system of claim 8, further comprising: an
accelerated graphics compatible northbridge mounted on the at least
one printed circuit board.
16. The computer system of claim 15, further comprising: a memory
mounted on the at least one printed circuit board.
17. The computer system of claim 15, further comprising: a data bus
integral with the at least one printed circuit board.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates, in general, to printed
circuit boards.
[0003] 2. Description of the Related Art
[0004] A printed circuit board is a board made of non-conducting
material, such as plastic, glass, ceramic, or some other dielectric
on which chips and other electronics are mounted. A multilayer
printed circuit board is a printed circuit board consisting of two
or more layers of board material. Each separate layer has its own
metallic tracings to provide electrical connections between various
electronic components and to provide connections to other layers.
The layers are laminated together to produce a single circuit board
to which the components, such as integrated circuits, resistors,
and capacitors are attached.
[0005] One common multilayer printed circuit board scenario is to
have alternating layers, where a first layer is composed in all or
part of conducting materials, a second layer is composed mostly of
insulating material, and a third layer is composed in all or part
of conducting materials, with portions of the conducting materials
in the first and third layer connected by conducting materials
interposed within channels within the second insulating layer. Such
first, second, and third layers typically form part or all of an
electric circuit. Many such alternating layers are often used to
construct a final circuit.
[0006] With reference now to FIG. 1, shown is a perspective view of
a grossly simplified example of alternating layers within an
multilayer printed circuit board which form equivalent electric
circuit 150. Depicted is that equivalent electric circuit 150 has a
current loop 152 from driver 102 to receiver 106. Current loop 152
travels an electrically conductive path provided by multilayer
printed circuit board structure 154. Multilayer printed circuit
board structure 154 depicts a first layer (not shown) having driver
102, metallic trace 104, and receiver 106 which are contained
within a first layer (not shown) of printed circuit board structure
154. Driver 102 is illustrated as electrically connected to
metallic trace 104 (e.g., a copper trace). Metallic trace 104 is
shown electrically connected to receiver 106. Receiver 106 is
depicted as electrically connected to metallic wire 112. Metallic
wire 112 is depicted as electrically connected at point 162 with
conducting plane 116. Conducting plane 116 is illustrated as
electrically connected at point 164 to metallic wire 118. Metallic
wire 112 and metallic wire 118 are depicted as contained within a
cylindrical channel hollowed out from a second insulating layer
(not shown) of printed circuit board structure 154. For sake of
illustration and coordination with equivalent electrical circuit
150, electrical current loop 152 is shown flowing from driver 102
to receiver 106 through metallic trace 104. Thereafter, electrical
current loop 152 is shown flowing through metallic wire 112,
metallic conducting plane 116, and metallic wire 118 back to driver
102.
[0007] Referring now to FIG. 2A, depicted is an isolated
perspective view of metallic conducting plane 116 and metallic
trace 104 of FIG. 1. As has been described, metallic wires 112, 118
(of FIG. 1A) respectively electrically connect with conducting
plane 116 at points 162, 164 on conducting plane 116 which are
shown relatively "in line" with metallic trace 104. Viewed from the
perspective of conducting plane 116, when relatively high frequency
alternating current (e.g., current with frequencies substantially
in excess of 10 kHz) is flowing in current loop 152 (of FIG. 1),
metallic wires 112, 118 (of FIG. 1A) are respectively sourcing and
sinking current into points 162, 164 on conducting plane 116.
Insofar as conducting plane 116 typically has relatively uniform
characteristics, return current 160, flowing between point 162 to
point 164, will tend to follow a path substantially underneath
metallic trace 104, since for relatively high frequency alternating
current the path underneath metallic trace 104 is the path of least
impedance for reasons well-known to those in the art. The magnitude
of return current 160 will be substantially the same as that of
source current 159, since together source current 159 and return
current 160 make up loop current 152. However, since conducting
plane 116 is of greater width physical width than metallic trace
104, although the majority of return current 160 will attempt to
flow under metallic trace 104, in actuality it will be distributed
across width 170 of conducting plane 116 in a fashion illustrated
by FIG. 2B.
[0008] With reference now to FIG. 2B, illustrated is an example of
distribution 161 of return current 160 (of FIGS. 1 and 2A).on
conducting plane 116. Shown is that the majority of return current
160 (of FIGS. 1 and 2A) is distributed, or flowing, through the
portion of conducting plane 116 which lies substantially directly
below metallic trace 104.
[0009] Referring again to FIG. 1, those skilled in the art will
recognize that it is not necessary for metallic wires 112, 118 to
be present in order for a return current to be present on
conducting plane 116. That is, the mere presence of an alternating
current in metallic trace 104 proximate to conducting plane 116 is
sufficient to induce a return current such as return current 160
(although metallic trace 104 is shown in a plane above conducting
layer 116, metallic trace 104 could be coplanar with conducting
plane 116, as will be demonstrated in the detailed description).
See e.g., M. Zahn, Electromagnetic Field Theory: A Problem Solving
Approach 361-363 (1979). Furthermore, in point of fact, in an
actual implementation it is likely that both current resulting from
metallic wires 112, 118 and from magnetic induction will be present
on conducting plane 116. However, for ease of description the
discussion herein focuses on the current resulting from the
presence of metallic wires 112, 118, although it is to be
understood that in addition to or in the alternative to such
current resulting from the presence of metallic wires connecting at
points 162, 164, a return current can be present arising solely
from the presence of alternating current within metallic trace 104,
when metallic trace 104 is located proximate to conducting plane
116. This fact is to be borne in mind whenever discussion is made
of any return current described in the present application.
[0010] Unfortunately, as printed circuit board densities have
increased, the structure illustrated in FIGS. 1, 2A, and 2B is
becoming less and less practicable. Instead, it is becoming common
within the art for conducting plane 116 to be split into two
pieces, for a variety of reasons. Splitting conducting plane 116
gives rise to a number of practical problems, a few of which will
now be described.
[0011] Referring now to FIG. 3, shown is a modified version of
multilayer printed circuit board structure 154, referred to as
multilayer printed circuit board structure 300, which is
structurally similar to printed circuit board structure 154 except
that a conducting plane is shown broken into first metallic
conducting part 302 and second metallic conducting part 304,
thereby forming split conducting plane 316. Depicted is that first
metallic conducting part 302 and second metallic conducting part
304 are separated by dielectric-filled moat 306 which is typically
composed of a dielectric material. Shown is that metallic wires
112, 118 respectively connect with split conducting plane 316 at
points 362, 364 on split conducting plane 316.
[0012] Those skilled in the art will recognize that even though
there is no contiguous return path from receiver 106 to driver 102
through split conducting plane 316, driver 102 and receiver 106
will still function because second metallic conducting part 304 and
first metallic conducting part 302 function as a sort of
"parallel-plate" capacitor. This fact is illustrated by loop
current 352 in equivalent electric circuit 350, wherein first
metallic conducting part 302 and second metallic conducting part
304 separated by dielectric-filled moat 306 is represented by
capacitor 353. Further shown is that loop current 352 can be viewed
as composed of a source current 359 and a return current 360, each
having substantially equal magnitude (since they make up loop
current 352) but different distributions within their respective
current flow paths.
[0013] Those skilled in the art will recognize that there are
government (e.g., the Federal Communications Commission in the
United States) and industry electromagnetic compatibility (EMC)
standards which set limits on the amount of electromagnetic
radiation which may emanate from electrical systems having
integrated circuits. As will be described in the detailed
description, it has been discovered that split conducting plane 316
composed of first metallic conducting part 302, and
dielectric-filled moat 306, and second metallic conducting part 304
of multilayer printed circuit board structure 300 tends to radiate
a substantial amount of electromagnetic energy above and beyond
that radiated by metallic conducing layer 116 of multilayer printed
circuit board structure 300 (which for all practical purposes
amounts to almost zero radiated electromagnetic energy compared to
that radiated by the foregoing described structure of multilayer
printed circuit board structure 300). Insofar as the government and
industry standards are aggregative, it is desirable that each
printed circuit board component radiate as little electromagnetic
energy as possible, because the smallest increase in radiated
energy can often make the difference between passing and failing
compliance standards.
[0014] It is therefore apparent that a need exists to decrease the
electromagnetic energy radiated from split metallic conductors
carrying electrical energy, such as split conducting plane 316
composed of first metallic conducting part 302, dielectric-filled
moat 306, and second metallic conducting part 304 of multilayer
printed circuit board structure 300.
SUMMARY OF THE INVENTION
[0015] It has been discovered that an apparatus can be produced
which will substantially decrease radiated emissions from split
metallic conductors carrying electrical energy. The apparatus
provides a split metallic conducting plane having a split formed by
a dielectric-filled moat spanning a width of a side of a first
metallic conducting part running substantially parallel to a side
of a second metallic conducting part, with the moat structured such
that the side of the first metallic part has at least two
indentations and such that the side of the second metallic part has
at least two indentations, and where a metallic trace is located
proximate to the split metallic conducting plane.
[0016] The foregoing is a summary and thus contains, by necessity,
simplifications, generalizations and omissions of detail;
consequently, those skilled in the art will appreciate that the
summary is illustrative only and is not intended to be in any way
limiting. Other aspects, inventive features, and advantages of the
present invention, as defined solely by the claims, will become
apparent in the non-limiting detailed description set forth
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The present invention may be better understood, and its
numerous objects, features, and advantages made apparent to those
skilled in the art by referencing the accompanying drawings.
[0018] FIG. 1 shows a perspective view of a grossly simplified
example of alternating layers within an multilayer printed circuit
which forms equivalent electric circuit 150.
[0019] FIG. 2A depicts an isolated perspective view of metallic
conducting plane 116 and metallic trace 104.
[0020] FIG. 2B illustrates an example of distribution 161 of return
current 160 on conducting plane 116.
[0021] FIG. 3 shows a modified version of multilayer printed
circuit board structure 154, referred to as multilayer printed
circuit board structure 300, wherein conducting plane 116 is shown
broken into first metallic conducting part 302 and second metallic
conducting part 304, thereby forming split conducting plane
316.
[0022] FIG. 4A depicts an isolated perspective view of first
metallic conducting part 302 separated from second metallic
conducting part 304 by dielectric-filled moat 306.
[0023] FIG. 4B illustrates an example of distribution 401 of return
current 360 on first metallic conducting part 302 and second
metallic conducting part 304 at dielectric-filled moat 306.
[0024] FIG. 5A depicts split conducting plane 516 wherein the split
is depicted as repeating rectangular structure dielectric-filled
moat 500 which substantially minimizes an impedance encountered by
return current 360 and which substantially minimizes the flow of
current at or near peripheries 404, 406 of split conducting plane
516 such as multilayer printed circuit board structure 300.
[0025] FIG. 5B illustrates an example of distribution 501 of return
current 360 on first metallic conducting part 502 having a
repeating rectangular structure 504 and a second metallic
conducting part 506 having a repeating rectangular structure
508.
[0026] FIG. 5C depicts a split conducting plane 516 wherein the
split is shown as a "tighter" repeating rectangular structure
dielectric-filled moat 500 such that multiple rectangular
structures exist under metallic trace 104.
[0027] FIG. 6 depicts split conducting plane 616 wherein the split
is depicted as repeating triangular structure dielectric-filled
moat 600.
[0028] FIG. 7 depicts split conducting plane 716 wherein the split
is illustrated as repeating T-shaped structure dielectric-filled
moat 700.
[0029] FIG. 8 depicts split conducting plane 816 wherein the split
is shown as repeating arrow-shaped structure dielectric-filled moat
800.
[0030] FIG. 9A depicts split conducting plane 516 wherein the split
is depicted as repeating rectangular structure dielectric-filled
moat 500, and wherein metallic trace 904 is shown alongside, or
relatively coplanar with, split conducting plane 516.
[0031] FIG. 9B illustrates an example of distribution 901 of return
current 960 on side having repeating rectangular structure 504 of
first metallic conducting part 502, and side having repeating
rectangular structure 508 of second metallic conducting part
506.
[0032] FIG. 10 depicts a pictorial representation of a
data-processing system in which printed circuit boards are
utilized.
[0033] FIG. 11 illustrates selected components which may be present
within an implementation of network server computer 1020.
[0034] FIG. 12 illustrates are selected components which may be
present within an implementation of network server computer
1020.
[0035] The use of the same reference symbols in different drawings
indicates similar or identical items.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0036] The following sets forth a detailed description of the best
contemplated mode for carrying out the independent invention(s)
described herein. The description is intended to be illustrative
and should not be taken to be limiting.
[0037] With reference now to FIG. 4A, depicted is an isolated
perspective view of first metallic conducting part 302 separated
from second metallic conducting part 304 by dielectric-filled moat
306 of FIG. 3. Because there is no longer a physically contiguous
path such as in metallic conducting plane 116 (of FIG. 1), return
current 360, seeking the path of least impedance will tend to
spread out and follow fan-shaped current flow path 400 (where the
flow path has current distribution 401 shown in FIG. 4B, below)
from point 162 to point 164. Those skilled in the art will
recognize that there are a multitude of ways in which this current
behavior can be described, but one grossly-simplified way would be
to recognize that for a parallel plate capacitor, the capacitance
in farads is roughly given by the equation
"C=(.epsilon..times.A).div.d"--where .epsilon. is the permittivity
in farads/meter of the dielectric separating the conducting plates,
A is the area in meters of the plates, and d is the distance in
meters separating the plates, and that the impedance Z of a
capacitor is roughly given by relation "Z=1/(j.omega.C)," where
.omega. is angular frequency in radians/second, and C is
capacitance in farads; consequently, the current spreads out across
width 470 since this will tend to substantially maximize the
capacitance C which will tend to minimize the substantially
impedance Z which return current 360 will experience traversing
split conducting plane 316.
[0038] Even though return current 360 will tend to flow in a fan
shaped pattern, the magnitude of return current 360 will tend to be
substantially the same as that of source current 359, since
together source current 359 and return current 360 make up loop
current 352 (of FIG. 3). (In addition, note that return current 360
would also be roughly equal to source current 359 even if return
current 360 were magnetically induced by relatively high frequency
source current 359.).
[0039] Referring now to FIG. 4B, illustrated is an example of
distribution 401 of return current 360 (of FIGS. 3 and 4A) on first
metallic conducting part 302 (of FIGS. 3 and 4A) and second
metallic conducting part 304 at dielectric-filled moat 306 (of
FIGS. 3 and 4A). Shown is that at dielectric-filled moat 306 return
current 360 is distributed widely across width 470 of first
metallic conducting part 302 and second metallic conducting part
304 in the manner expected in view of fan-shaped current flow path
400 (of FIG. 4A). Even though it might appear from the illustration
that current distribution drops to zero at some point interior to
peripheral edge 404 and peripheral edge 406, it is to be understood
that such is not the case, and that in fact some current is in fact
flowing up to and adjacent with the peripheral edge 404 and
peripheral edge 406 as is illustrated by fan-shaped current flow
400 (of FIG. 4A).
[0040] Referring again to FIG. 4A, because return current 360
follows fan-shaped current flow path 400, or equivalently has
distribution 401, the impedance encountered by return current 360
between points 362 and 364 is substantially greater than the
impedance encountered by return current 160 between points 162 and
164 described in relation to FIGS. 1, 2A, and 2B, above.
Consequently, return current 360 will give rise to a greater
voltage across the impedance existing between points 362 and 364
than that caused by return current 160 across the impedance
existing 20 between points 162 and 164 described in relation to
FIGS. 1, 2A, and 2B. This greater voltage drop tends to create
radiated electromagnetic emissions from split conducting plane 316
greater than those of conducting plane 116 (of FIG. 1).
[0041] Those skilled in the art will recognize that EMC standards
are usually specified as a function of some distance (illustrated
as "test distance d" in FIG. 4A) from an edge of a printed circuit
board component. It has been discovered that the strength of
radiated emissions detected at a given distance from a split
conducting plane will be reduced if the impedance encountered by a
return current traversing the split conducting plane is reduced. It
has also been discovered that the strength of radiated emissions
detected at a given distance from a split conducting plane will be
reduced if the voltage generated by a return current traversing the
split conducting plane is concentrated away from the periphery of
the board. Restated, it has been found advantageous to
substantially minimize the impedance encountered by a return
current traversing a split conducting plane and to substantially
minimize the flow of the return current at or near the peripheries
of the split conducting plane which the return current is
traversing.
[0042] With reference now to FIG. 5A, depicted is split conducting
plane 516 which is structurally similar to split conducting plane
316 except that the split is depicted as repeating rectangular
structure dielectric-filled moat 500. Replacing split conducting
plane 316 in multilayer printed circuit board structure 300 (of
FIG. 3) with split conducting plane 516 substantially minimizes an
impedance encountered by return current 360 between points 362 and
364 and substantially minimizes the flow of current at or near
peripheries 404, 406 of split conducting plane 516. Specifically,
depicted is a side having repeating rectangular structure 504 of
first metallic conducting part 502 and side having repeating
rectangular structure 508 of second metallic conducting part 506.
Sides having repeating rectangular structures 504 and 508 are
constructed so that they interdigitate as shown. Sides having
repeating rectangular structures 504 and 508 are separated by
repeating rectangular structure dielectric-filled moat 500. Notice
that, the effective length of the faces of a "parallel-plate-like"
capacitor formed by side having repeating rectangular structure 504
of first metallic conducting part 502 and side having repeating
rectangular structure 508 of second metallic conducting part 506
has been substantially increased by sides having repeating
rectangular structures 504 and 508. Consequently, the impedance
encountered by return current 360 will be decreased and thus the
voltage drop from point 362 to 364 will be decreased, which will
decrease radiated emissions. In addition, the decreased impedance
will allow more current to flow in the lower resistance path under
metallic trace 104, which will correspondingly decrease current
flow near the peripheries 404, 406 of split conducting plane 516,
which will also decrease radiated emissions.
[0043] Referring now to FIG. 5B, illustrated is an example of
distribution 501 of return current 360 (of FIG. 5A) on side having
repeating rectangular structure 504 (of FIG. 5A) of first metallic
conducting part 502 (of FIG. 5A) and side having repeating
rectangular structure 508 (of FIG. 5A) of second metallic
conducting part 506 (of FIG. 5A). Shown is that at
dielectric-filled moat 510 (of FIG. 5A) return current 360 (of FIG.
5A) is distributed across first metallic conducting part 502 (of
FIG. 5A) having a repeating rectangular structure 504 (of FIG. 5A)
and a second metallic conducting part 506 (of FIG. 5A) having a
repeating rectangular structure 508 (of FIG. 5A) in a manner such
that the majority of the return current is concentrated near the
interior of the board. Further shown in expanded view 550 of
periphery region 552 of split conducting plane 516 is that side
having repeating rectangular structure 504 (of FIG. 5A) of first
metallic conducting part 502 (of FIG. 5A) and side having repeating
rectangular structure 508 (of FIG. 5A) of second metallic
conducting part 506 (of FIG. 5A) shifts distribution of current
away from periphery 406 (of FIG. 5A) of split conducting plane 516,
which also reduces measured electromagnetic emissions at some
distance d from the board.
[0044] With reference now to FIG. 5C, depicted is a split
conducting plane 516 wherein the split is shown as a "tighter"
repeating rectangular structure dielectric-filled moat 500 such
that multiple rectangular structures exist under metallic trace
104. Since there are even more interdigitated rectangular shapes
spanning split conducting plane 516, this allows even greater
concentration of the distribution of current on the interior of
split conducting plane 516 than that possible with the structure
shown in FIG. 5A. Consequently, the structure shown in FIG. 5C will
allow an even greater reduction in radiated emissions over that
shown in FIG. 5A.
[0045] Referring now to FIG. 6, depicted is split conducting plane
616 wherein the split is depicted as repeating triangular structure
dielectric-filled moat 600. Specifically, depicted is side having a
repeating triangular structure 604 of first metallic conducting
part 602, and having a repeating triangular structure 608 of second
metallic conducting part 606. Sides having repeating triangular
structures 604 and 608 are constructed so that they interdigitate
as shown. Sides having repeating triangular structures 604 and 608
are separated by dielectric-filled moat 600. Dielectric-filled
repeating triangular structure moat 600 reduces radiated emissions
in a manner analogous to repeating rectangular structure
dielectric-filled moat 500.
[0046] With reference now to FIG. 7, depicted is split conducting
plane 716 wherein the split is illustrated as repeating T-shaped
structure dielectric-filled moat 700. Specifically, depicted is
side having repeating T-shaped structure 704 of first metallic
conducting part 702 and side having repeating T-shaped structure
708 of second metallic conducting part 706. Sides having repeating
T-shaped structures 704 and 708 are constructed so that they
interdigitate as shown. Sides having repeating T-shaped structures
704 and 708 are separated by repeating T-shaped structure
dielectric-filled moat 700. Dielectric-filled repeating T-shaped
structure moat 700 reduces radiated emissions in a manner analogous
to repeating rectangular structure dielectric-filled moat 500.
[0047] Referring now to FIG. 8, depicted is split conducting plane
816 wherein the split is shown as repeating arrow-shaped structure
dielectric-filled moat 800. Specifically, depicted is side having
repeating arrow-shaped structure 804 of first metallic conducting
part 802, and side having a repeating arrow-shaped structure 808 of
second metallic conducting part 806. Sides having repeating
arrow-shaped structures 804 and 808 are constructed so that they
interdigitate as shown. Sides having repeating arrow-shaped
structures 804 and 808 are separated by repeating arrow-shaped
dielectric-filled moat 800. Repeating arrow-shaped
dielectric-filled moat 800 reduces radiated emissions in a manner
analogous to repeating rectangular structure dielectric-filled moat
500.
[0048] With reference now to FIG. 9A, depicted is split conducting
plane 516 wherein the split is depicted as repeating rectangular
structure dielectric-filled moat 500, and wherein metallic trace
904 is shown alongside, or relatively coplanar with, split
conducting plane 516. Specifically, illustrated is that metallic
trace 904 carries source current 959 from a driver (not shown) and
that split conducting plane 516 carries return current 960, equal
in magnitude to source current, from a receiver (not shown).
Depicted is side having repeating rectangular structure 504 of
first metallic conducting part 502, and side having repeating
rectangular structure 508 of second metallic conducting part 506.
Sides having repeating rectangular structures 504 and 508 are
constructed so that they interdigitate as shown. Sides having
repeating rectangular structures 504 and 508 are separated by
repeating rectangular structure dielectric-filled moat 500.
Repeating rectangular structure dielectric-filled moat 500 reduces
radiated emissions in a manner analogous to that described in
relation to FIG. 5A, such that the radiated emissions from
periphery 406 of split conducting plane 516 is substantially
reduced. The situation shown in FIG. 9A is that where return
current 960 is induced magnetically (it is to be assumed that split
conducting plane 516 is part of a larger circuit which functions to
form a continuous loop). However, it is also to be understood that
return current 960 could also be generated by an actual physically
connected circuit between metallic trace 904 and split conducting
plane 516 analogous to the circuit illustrated in FIG. 3.
[0049] Referring now to FIG. 9B, illustrated is an example of
distribution 901 of return current 960 on side having repeating
rectangular structure 504 (of FIG. 9A) of first metallic conducting
part 502 (of FIG. 9A) and side having repeating rectangular
structure 508 (of FIG. 9A) of second metallic conducting part 506
(of FIG. 9A). Shown is that return current 960 has distribution 901
across side having repeating rectangular structure 504 (of FIG. 9A)
of first metallic conducting part 502 (of FIG. 9A) and side having
repeating rectangular structure 508 (of FIG. 9A) of second metallic
conducting part 506 (of FIG. 9A) in a manner such that the majority
of return current 960 is concentrated near the edge of the board
nearest metallic trace 904, which reduces measured electromagnetic
emissions at some distance d from opposite board edge. Further
shown are current distribution 903 where the metallic conducting
plane a continuous plane, and current distribution 905 where the
metallic conducting plane is a split plane. It is to be understood
that although split conducting plane 516 (of FIG. 9A) was discussed
above in relation to FIGS. 9A and 9B, previously discussed
conducting planes 616, 716, and 816 could likewise be utilized in
the same way that split conducting plane 516 (of FIG. 9A) is
utilized in FIGS. 9A and 9B. Further shown in expanded view 950 of
periphery region 552 (of FIG. 9A) of split conducting plane 516 (of
FIG. 9A) is that side having repeating rectangular structure 504
(of FIG. 9A) of first metallic conducting part 502 (of FIG. 9A) and
side having repeating rectangular structure 508 (of FIG. 9A) of
second metallic conducting part 506 (of FIG. 9A) shifts
distribution of current away from periphery 406 (of FIG. 9A) of
split conducting plane 516, which also reduces measured
electromagnetic emissions at some distance d from the board.
[0050] With reference now to FIG. 10, depicted is a pictorial
representation of a data-processing system in which printed circuit
boards are utilized. A network server computer 1020 is depicted.
Shown present and associated with network server computer 1020 are
system unit 1022, video display device 1024, keyboard 1026, mouse
1028, and microphone 1048. Network server computer 1020 may be
implemented utilizing any suitable network server computer such as
the Dell PowerEdge network server computer. ("Dell" and "PowerEdge"
are trademarks of Dell Computer Corporation, located in Round Rock,
Texas). Those skilled in the art will recognize that various
implementations of network server computer 1020 can have many
different components, such as those components illustrated below in
FIG. 11 and FIG. 12. It will be understood by those in the arts the
majority of components illustrated in FIG. 11 and FIG. 12 will be
interconnected via the use of printed circuit boards. Accordingly,
the above described structures of FIGS. 5A-9B will be particularly
useful with such printed circuit boards when a metallic trace, such
as metallic trace 1004, appears proximate to a split metallic
conducting plane within the printed circuit board.
[0051] Referring now to FIG. 11, illustrated is selected components
which may be present within an implementation of network server
computer 1020. Network server computer 1020 includes a Central
Processing Unit ("CPU") 1131, which is intended to be
representative of either a conventional microprocessor, or more
modern multiprocessors, and a number of other units interconnected
via system bus 1132. Network server computer 1020 includes
random-access memory ("RAM") 1134, read-only memory ("ROM") 1136,
display adapter 1137 for connecting system bus 1132 to video
display device 1024, and I/O adapter 1139 for connecting peripheral
devices (e.g., disk and tape drives 1133) to system bus 1132. Video
display device 1024 is the visual output of computer 1020, which
can be a CRT-based video display well-known in the art of computer
hardware. However, video display device 1024 can also be an
LCD-based or a gas plasma-based flat-panel display. Network server
computer 1020 further includes user interface adapter 1140 for
connecting keyboard 1026, mouse 1028, speaker 1046, microphone
1048, digital camera and/or other user interface devices (not
shown), such as a touch screen device (not shown), to system bus
1132 through I/O adapter 1139. Communications adapter 1149 connects
network server computer 1020 to a data-processing network. Shown
for sake of illustration is that printed circuit board 1155
interconnects a number of the foregoing described components.
[0052] Any suitable machine-readable media may retain the graphical
user interface, such as RAM 1134, ROM 1136, a magnetic diskette,
magnetic tape, or optical disk (the last three being located in
disk and tape drives 1133). Any suitable operating system and/or
associated graphical user interface (e.g., Microsoft Windows) may
direct CPU 1131. Other technologies can also be utilized in
conjunction with CPU 1131, such as touch-screen technology or human
voice control. In addition, network server computer 1020 includes a
control program 1151 which resides within computer storage
1150.
[0053] Those skilled in the art will appreciate that the hardware
depicted in FIG. 11 may vary for specific applications. For
example, other peripheral devices such as optical disk media, audio
adapters, or programmable devices, such as PAL or EPROM programming
devices well-known in the art of computer hardware, and the like
may be utilized in addition to or in place of the hardware already
depicted.
[0054] Those skilled in the art will recognize that network server
computer 1020 can be described in relation to other network server
computers which perform essentially the same functionalities,
irrespective of architectures.
[0055] With reference now to FIG. 12, illustrated is are selected
components which may be present within an implementation of network
server computer 1020. Shown are AGP-enabled graphics controller
1200, AGP interconnect 1202 (a data bus), and AGP-enabled
Northbridge 1204. Not shown, but deemed present is an AGP-enabled
operating system. The term AGP-enabled is intended to mean that the
so-referenced components are engineered such that they interface
and function under the standards defined within the AGP interface
specification (Intel Corporation, Accelerated Graphics Port
Interface Specification, Revision 1.0 (Jul. 31 1996)). Further
depicted are video display device 1024, local frame buffer 1212,
Central Processing Unit (CPU) 1131 (wherein are depicted
microprocessor 1209, L1 Cache 1211, and L2 Cache 1213), CPU bus
1215, system memory 1216, Peripheral Component Interconnect (PCI)
bus 1218, various PCI Input-Output (I/O) devices 1250, 1252, and
1254, Southbridge 1222, 1394 Device 1225, and network card 1227.
Shown for sake of illustration is that printed circuit board 1155
interconnects a number of the foregoing described components.
[0056] The foregoing components and devices are used herein as
examples for sake of conceptual clarity. As for (non-exclusive)
example, CPU 1131 is utilized as an exemplar of any general
processing unit, including but not limited to multiprocessor units;
CPU bus 1215 is utilized as an exemplar of any processing bus,
including but not limited to multiprocessor buses; PCI devices
1250-1254 attached to PCI bus 1218 are utilized as an exemplar of
any input-output devices attached to any I/O bus; AGP Interconnect
1202 is utilized as an exemplar of any graphics bus; AGP-enabled
graphics controller 1200 is utilized as an exemplar of any graphics
controller; Northbridge 1204 and Southbridge 1222 are utilized as
exemplars of any type of bridge; 1394 device 1225 is utilized as an
exemplar of any type of isochronous source; and network card 1227,
even though the term "network" is used, is intended to serve as an
exemplar of any type of synchronous or asynchronous input-output
cards. Consequently, as used herein these specific exemplars are
intended to be representative of their more general classes.
Furthermore, in general, use of any specific exemplar herein is
also intended to be representative of its class and the
non-inclusion of such specific devices in the foregoing list should
not be taken as indicating that limitation is desired.
[0057] Generally, each bus utilizes an independent set of protocols
(or rules) to conduct data (e.g., the PCI local bus specification
and the AGP interface specification). These protocols are designed
into a bus directly and such protocols are commonly referred to as
the "architecture" of the bus. In a data transfer between different
bus architectures, data being transferred from the first bus
architecture may not be in a form that is usable or intelligible by
the receiving second bus architecture. Accordingly, communication
problems may occur when data must be transferred between different
types of buses, such as transferring data from a PCI device on a
PCI bus to a CPU on a CPU bus. Thus, a mechanism is developed for
"translating" data that are required to be transferred from one bus
architecture to another. This translation mechanism is normally
contained in a hardware device in the form of a bus-to-bus bridge
(or interface) through which the two different types of buses are
connected. This is one of the functions of AGP-enabled Northbridge
1204, Southbridge 1222, and other bridges shown in that it is to be
understood that such can translate and coordinate between various
data buses and/or devices which communicate through the
bridges.
Other Embodiments
[0058] Several various embodiments have been described above, and
it will be obvious to those skilled in the art that, based upon the
teachings herein, changes and modifications may be made without
departing from this invention and its broader aspects. That is, all
examples set forth herein are intended to be exemplary and
non-limiting.
[0059] As an example of the forgoing-referenced changes and
modifications, each straight-line segment in a structure, such as
the repeating rectangular structures discussed above, could itself
be replaced by a structure which increases effective length (e.g.,
a specific side of the rectangular structure could itself be
replaced by a repeating triangular structure across that specific
side). As another example of the foregoing-referenced changes and
modifications, a non-repetitive pattern could be utilized to span
the width of a split conducting plane rather than a repeating
structure (e.g., a rectangular structure, followed by a circular
structure, followed by a triangular structure, followed by a
star-shaped structure, etc.). Accordingly, the above-described
architectures are not intended to be limiting.
[0060] Other embodiments are within the following claims.
[0061] While particular embodiments of the present invention have
been shown and described, it will be obvious to those skilled in
the art that, based upon the teachings herein, changes and
modifications may be made without departing from this invention and
its broader aspects and, therefore, the appended claims are to
encompass within their scope all such changes and modifications as
are within the true spirit and scope of this invention.
Furthermore, it is to be understood that the invention is solely
defined by the appended claims. It will be understood by those
within the art that if a specific number of an introduced claim
element is intended, such an intent will be explicitly recited in
the claim, and in the absence of such recitation no such limitation
is present. For example, as an aid to understanding, the following
appended claims may contain usage of the phrases "at least one" or
"one or more," or the indefinite articles "a" or "an," to introduce
claim elements. However, the use of such phrases should not be
construed to imply that the introduction of a claim element by the
indefinite articles "a" or "an" limits any particular claim
containing such introduced claim element to inventions containing
only one such element, even when the same claim includes the
introductory phrases "one or more" or "at least one" and indefinite
articles such as "a" or "an"; the same holds true for the use of
definite articles used to introduce claim elements.
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