U.S. patent application number 09/740611 was filed with the patent office on 2001-07-26 for low impedance hinge for notebook computer.
Invention is credited to Carlson, Russell W..
Application Number | 20010009499 09/740611 |
Document ID | / |
Family ID | 23323635 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009499 |
Kind Code |
A1 |
Carlson, Russell W. |
July 26, 2001 |
Low impedance hinge for notebook computer
Abstract
A capacitor is formed at a hinge between a display compartment
and a microcomputer compartment to reduce EMI emissions caused by
the display/microcomputer interface. A plane structure is formed
along the length of the display compartment, and another plane
structure is formed along the length of the microcomputer
compartment. The display compartment's plane structure serves as
the ground connection for the display device. It connects to the
plane structure of the microcomputer compartment through a
capacitative structure. The two plane structures and the
capacitative structure form the return path for coupling the
display device to a common, system ground. The hinge has as one
circular structure concentrically surrounding and in close
proximity to another circular structure. The capacitor is formed by
the arc area where the two circular structures overlap
concentrically, having low impedance at high frequencies (e.g., 30
MHz and above).
Inventors: |
Carlson, Russell W.;
(Loomis, CA) |
Correspondence
Address: |
HEWLETT-PACKARD COMPANY
Intellectual Property Administration
P.O. Box 272400
Fort Collins
CO
80527-2400
US
|
Family ID: |
23323635 |
Appl. No.: |
09/740611 |
Filed: |
December 18, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09740611 |
Dec 18, 2000 |
|
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09338157 |
Jun 22, 1999 |
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Current U.S.
Class: |
361/679.28 |
Current CPC
Class: |
Y10T 292/1025 20150401;
G06F 1/1656 20130101; G09G 5/006 20130101; G06F 1/1681 20130101;
G06F 1/1616 20130101; G06F 1/1683 20130101 |
Class at
Publication: |
361/683 ;
361/680; 361/681 |
International
Class: |
G06F 001/16; H05K
005/00 |
Claims
What is claimed is:
1. A portable computing apparatus, comprising: a microcomputer
compartment having a microcomputer, a first conductive path, a
system ground and a first interface; a display compartment attached
to the microcomputer compartment, the display compartment having a
display panel, a second conductive path, a ground path and a second
interface; and a hinge coupling the display compartment to the
microcomputer compartment, the hinge enabling the display
compartment to rotate relative to the microcomputer compartment,
the hinge comprising a capacitative structure of low impedance over
a frequency range between 30 MHz and 1 GHz; wherein the first
interface and the second interface are connected to the
capacitative structure; the first conductive path is electrically
coupled to the second conductive path; and the ground path is
electrically coupled to the system ground through the second
interface, capacitative structure and first interface.
2. The apparatus of claim 1, in which the hinge comprises: a first,
generally cylindrical structure and a second generally cylindrical
structure, the first generally cylindrical structure concentrically
surrounding the second generally cylindrical structure over at
least a portion of a circumference of the second cylindrical
structure to form an overlapping arc, said overlapping arc defining
a capacitative structure.
3. The portable computing apparatus of claim 2, in which the
capacitative structure further comprises a dielectric between the
first generally cylindrical structure and a second generally
cylindrical structure.
4. A method for reducing electromagnetic interference emissions
attributable to an interface between a display compartment and a
microcomputer compartment of a portable computing apparatus, the
microcomputer compartment having a microcomputer, a first
conductive path, a system ground and a first interface, the display
compartment attached to the microcomputer compartment, the display
compartment having a display panel, a second conductive path, a
ground path and a second interface, the display compartment being
attached to the microcomputer compartment by a hinge, the hinge
enabling the display compartment to rotate relative to the
microcomputer compartment between an open position and a closed
position, the method comprising: opening the display compartment
relative to the microcomputer compartment, wherein at least while
the display compartment is open, the hinge defines a capacitative
structure of low impedance over a frequency range between 30 MHz
and 1 GHz, and the first interface and the second interface are
connected to the capacitative structure; transmitting a display
signal from the first conductive path to the second conductive
path, wherein the first conductive path is electrically coupled to
the second conductive path; and forming a return-to-ground path for
the display signal to reduce electromagnetic interference
emissions, the return-to-ground path formed between the ground path
and the system ground through the second interface, capacitative
structure and first interface.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to display-hinged portable
computers, such as notebook computers and hand-held computers, and
more particularly, to hinge devices for attaching a display
compartment to a microcomputer compartment.
[0002] A portable computer is a popular computer configuration
enabling increased mobility for a user. Typically, a processor
board, display and keyboard are integrated into a case having one
or more compartments. A notebook computer typically includes a
display compartment and a microcomputer compartment permanently
attached in a hinged relationship. A flat panel display is mounted
within the display compartment. A keyboard, microcomputer, data
storage unit(s), expansion slot(s), and I/O ports are mounted in
the microcomputer compartment. Modular peripheral units such as a
floppy drive, hard drive, CD-ROM drive and modem or other PC card
are readily installed and removed from the microcomputer
compartment.
[0003] Electromagnetic interference is electromagnetic energy
emitted from electronic devices which, either directly or
indirectly, contributes to a degradation in performance of an
electronic receiver or other electronic system. Poorly shielded
electronic devices, for example, degrade radio and television
signals resulting in audible or visible static at receivers picking
up such signals, or cause other malfunctions of electronic
equipment. Governments typically regulate EMI emissions to enhance
public use of the radio wave spectrum and other electromagnetic
wave spectrums. In the United States, for example, the Federal
Communications Commission requires testing of devices and rates the
devices by class according to their emissions. The Federal
Communication Commission rates EMI emissions over a 120 kilohertz
bandwidth. The 120 kHz bandwidth corresponds to the typical
bandwidth of a conventional communication receiver, such as an FM
receiver. Reduced EMI emissions within such bandwidth reduce the
interference output perceived by a listener or viewer as, for
example, static, white noise, or "ghosts."
[0004] Typical precautions taken by electronic manufacturers are to
provide shielding of electronic devices to minimize EMI emissions.
Computer manufacturers, for example, typically use shielded cables
and shielded housings to minimize EMI emissions.
[0005] In a display-hinged portable computer there are conductive
paths from the microcomputer compartment to the display compartment
and a return path from the display compartment to the microcomputer
compartment. The conductive paths are to carry power and data to or
from the display device. The return path is to couple the display
to a system ground, rather than have a display ground which is
floating relative to the system ground. To leave the display
"floating" could result in a larger voltage differential and more
electromagnetic radiation. By coupling the display to a common
electrical ground plane with the microcomputer and other computer
modules, EMI emissions are reduced.
[0006] Conventionally, a ground wire or wire braid is used to form
a return path for a display compartment. Such wires have had
limited success in reducing EMI emissions. In particular, the wires
form a non-zero impedance electrical connection between the display
and system ground. The resulting voltage drop at high frequencies
across such non-zero impedance causes undesirable EMI emissions.
Such voltage drop acts as a voltage source which drives the display
relative to the microcomputer, much like two elements in a dipole
antenna. The result, for example, can be a vertically polarized EMI
emission that fails to comply with regulatory emissions standards.
Accordingly, complying with standards for EMI emissions in notebook
computers is a continuing challenge.
SUMMARY OF THE INVENTION
[0007] According to the invention, a capacitor is formed at a hinge
between a display compartment and a microcomputer compartment to
reduce electromagnetic interference (EMI) emissions attributable to
the display/microcomputer interface.
[0008] One advantage of the invention is that a low impedance
return path is provided between a display compartment and a
microcomputer compartment at high frequencies (e.g., 30 MHz and
above). The result is reduced EMI emissions at pertinent
frequencies. The invention will be better understood by reference
to the following detailed description taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a portable computer having a
low impedance hinge according to an embodiment of this
invention;
[0010] FIG. 2 is a perspective view of the portable computer of
FIG. 1 with the display compartment in a closed position;
[0011] FIG. 3 is an exploded view of the portable computer of FIG.
1;
[0012] FIG. 4 is a partial block diagram of the computer of FIG. 1
showing the system ground connection for the microcomputer and low
impedance hinge;
[0013] FIG. 5 is a diagram of the electrical connections to the low
impedance hinge of FIG. 1;
[0014] FIG. 6 is a diagram of the capacitative structure formed by
the hinge; and
[0015] FIG. 7 is a diagram of another embodiment of the
capacitative structure formed by the hinge.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0016] In one embodiment a plane structure is formed along the
length of the display compartment. Another plane structure is
formed along the length of the microcomputer compartment. The
display compartment is referred to herein as having a length, a
height and a thickness. The microcomputer compartment is referred
to as having a length, a width and a thickness. The length
typically is the longest dimension.
[0017] The display compartment's plane structure serves as the
ground connection for the display device. It connects to the plane
structure of the microcomputer compartment through a capacitative
structure. The two plane structures and the capacitative structure
form the return path for coupling the display device to a common,
system ground.
[0018] The capacitative structure is of a cylindrical shape
extending the length of the display and microcomputer compartments.
The cylinder has a diameter which is approximately the combined
thickness of the display compartment and microcomputer compartment.
Smaller diameters also may be used. Further, the capacitative
structure has very low impedance at high frequencies of interest,
(e.g., 30 MHz and above).
[0019] The capacitor is formed by the hinge between the display
compartment and the microcomputer compartment. In cross section the
hinge appears as one circular structure concentrically surrounding
and in close proximity to another circular structure. Contact
between the two circular structures is allowed, but not necessary.
Even where contact is allowed, the structure serves as a shorted
capacitor. Further, at the high frequencies, the structure has low
impedance. Where contact is not prescribed, an air gap or another
dielectric material is situated between the two circular
structures.
[0020] To open the display compartment one circular structure
rotates relative to the other circular structure. In doing so, the
two circular structures are concentric for only a portion (i.e.,
arc) of the circumference of the respective circular structures.
The capacitor occurs in the arc area where the two circular
structures overlap concentrically.
[0021] Referring to FIGS. 1 and 2, a portable notebook computer 10
according to an embodiment of this invention includes a display
compartment 12 hinged to a microcomputer compartment 14. The
display compartment 12 houses a display panel 24. The microcomputer
compartment houses a microcomputer 16, a keyboard 18, pointing
device 20, clicking device 22 and various modular components. The
microcomputer 16 includes a main processing unit and memory, and
receives inputs from the keyboard 18, pointing device 20, clicking
device 22, and a network interface or another input device or input
port. The microcomputer 16 generates outputs to the display panel
24, the modular components, and various peripheral devices or other
computers through a system of busses and various interfaces and
ports.
[0022] The modular components and peripherals may include a
non-volatile storage medium (e.g., hard disk drive), a
transportable storage media drive, (e.g., a floppy disk drive,
CD-ROM drive, zip drive, bernoulli drive or other magnetic, optical
or other storage media), and a communication or network interface
(e.g., modem; ethernet adapter). In addition one or more PC cards
embodying a modem or other peripheral device conforming to the
Personal Computer Memory Card International Association standards
are included in some embodiments.
[0023] A hinge 30 connects the display compartment 12 and
microcomputer compartment 14. FIG. 1 shows the hinge 30 in an open
position exposing the display panel 24 for viewing. FIG. 2 shows
the hinge 30 in a closed position, in which the display compartment
12 typically is locked to the microcomputer compartment 14. In a
preferred embodiment the hinge 30 is formed by concentric
cylindrical bodies 32, 34. A first generally cylindrical body 32
concentrically surrounds the second generally cylindrical body 34.
In one embodiment the first cylindrical body 32 is integral to the
microcomputer compartment 14 and the second cylindrical body 34 is
integral to the display compartment. In other embodiments either of
both of the cylindrical bodies 32, 34 are separately formed and
attached to the respective compartments 14, 12. Although, the body
34 attached to the display compartment 12 is shown to be inner to
the other cylindrical body 32, in other embodiments the body 34
attached to the display compartment 12 may concentrically surround
the body 34 attached to the microcomputer compartment 14.
[0024] In a preferred embodiment the first cylindrical body 32 is a
conductive sheet fitted to the microcomputer compartment 14
housing. Thus, the body 32 generally is not exposed to the user's
touch. Further, the second cylindrical body 34 also is a conductive
sheet fitted to a cylindrical edge of the display compartment 12.
Although a sheet of conductive material is preferred (due to the
more desirable electrical qualities obtained) the conductive
material may be otherwise applied to the housing, such as by a
plating or coating process.
[0025] The circumferential arc of the first cylindrical body 32
generally is less than 360.degree. and serves as a stop for the
display compartment. As the display compartment 12 is moved to
manipulate the computer 10 into an open position, the display
compartment 12 is rotated at the hinge 30 relative to the
microcomputer compartment 14. In doing so, the second cylindrical
body rotates relative to the first cylindrical body 32. At some
point during the rotation the further rotation is stopped as the
display compartment 12 bumps into the first cylindrical body 32.
Such position corresponds to the open-most position of the display
compartment 12. Preferably there is sufficient friction between the
first cylindrical body 32 and the second cylindrical body 34 to
allow relative rotation, yet also allow the display compartment 12
to be held in an open position which is less open than the
open-most position. In other embodiments a clutch mechanism or
other device is included to hold the display compartment 12 in any
of various open positions relative to the microcomputer compartment
14.
[0026] Referring to FIG. 3, an exploded view reveals a wire ribbon
connection 36 between the microcomputer 16 and display panel 24.
Such wire ribbon connection forms a conductive path 38 (see FIG. 4)
for carrying electrical signals between the microcomputer 16 and
display panel 24. Carried from the microcomputer 16 to the display
panel 24 are a power signal and one or more data and control
signals. Carried back from the display panel 24 to the
microcomputer 16 are one or more data and control signals. The
second cylindrical body 34 includes an opening 40 which spans a
portion of the body 34 length sufficient to fit the wire ribbon
connection 36. The opening extends along a portion of the
circumferential arc of the second cylindrical body 34. The extent
of the arc opening 40 is sufficient to allow the display
compartment 12 and second cylindrical body 34 to rotate relative to
the microcomputer compartment 14 and first cylindrical body 32 by
an amount sufficient to open and close the display without sheering
the wire ribbon connection 36. In a specific embodiment the opening
extends an arc of approximately 130.degree. (e.g., the angle that
the display compartment 12 forms relative to the microcomputer
compartment 14 in the open-most position.) Preferably, the opening
40 occurs toward the center of the cylindrical body 34 relative to
the length of such body 34, although the opening instead may occur
at other positions along the length of body 34.
[0027] In addition to the conductive paths 38 formed by the wire
ribbon connection 36 there also is a return path which couples the
display panel ground to a common system ground 41. More
specifically the display panel 24 is grounded to the same ground
plane (i.e., electrical plane) as the microcomputer 16. The display
panel 24 ground path is coupled to a planar structure 42 (FIG. 5),
which preferably extends the length of the second cylindrical body
34. In one embodiment the planar structure 42 is integrally formed
with the second cylindrical body 34. In some embodiments the planar
structure 42 is a part of the display compartment 12 housing. A
ground contact 25 of the display panel 24 defines the display
ground path and connects to the planar structure 42. The ground
contact includes in various embodiments either many point contacts
or elongated along the length of the display panel, or one
generally continuous contact extending approximately the length of
the display panel 24 and planar structure 42.
[0028] The planar structure 42 is in physical communication with
the second cylindrical body 34. The second cylindrical body 34 is
in electrical communication with the first cylindrical body 32,
either by direct contact or across an air gap or other dielectric
material. In either case, the first cylindrical body 32 and second
cylindrical body 34 together define a capacitative structure. Even
when in direct contact, at the frequencies being considered, the
inability to have a precise fully continuous contact between two
surface means that the structure will act as a capacitor as the
frequency range of interest, (e.g., 30 MHz and up). The upper limit
of the frequency range at which the structure operates as a
capacitor is related to the contacts and connections occurring
along the return path, (e.g., from display panel 24 to planar
structure 42; from planar structure 42 to cylindrical body 34; from
cylindrical body 34 to cylindrical body 32; from cylindrical body
32 to planar structure 44 (see FIG. 4), and from planar structure
44 to the system ground plane.)
[0029] Referring to FIG. 4, the planar structure 44 extends from
the first cylindrical body 32 at the microcomputer compartment 14.
In one embodiment the planar structure 44 is integrally formed with
the first cylindrical body 32. In some embodiments the planar
structure 44 is an integral part of the microcomputer compartment
14 housing (e.g., applied as a sheet or a coating or plating). A
conductive path 46 electrically interfaces the planar structure 44
to the common system ground 41. Preferably a connection is made
along substantially the full length of the planar structure 44,
such as by intimate contact with the ground plane of the pc board
of the microcomputer 16. Alternatively multiple point connections
or elongated connections may be used to form conductive path 46. As
discussed above the better the connection between the planar
structure 44 and the system ground 41, the lower the impedance of
the display/microcomputer interface. In particular, the better the
connection, the higher the frequency before the interface exhibits
inductance qualities and thus higher impedance. In a preferred
embodiment, connections are established of a quality sufficient to
provide a low impedance interface from 30 MHz up to at least 1 GHz.
(Generally, these frequencies are the limits set in the United
States corresponding to a certain standard for radiated
electromagnetic interference emissions). Although the specific
desired impedance will vary based upon physical dimensions and
materials, an impedance less than 1 ohm is preferred throughout the
frequency range. Specifically, the connection is to act like a
capacitor and decrease as frequency increases within the desired
frequency range. In one specific embodiment a connection having an
impedance of 0.7 ohms at 30 MHz is achieved. In such example, such
impedance decreases to 0.02 ohms at 1 GHz. Contrast this low
impedance connection to a conventional wire connection used for a
return path. The conventional wire return acts as an inductor and
typically increases in impedance over the frequency range of
interest (e.g., 30 MHz to 1 GHz).
[0030] The return path for the display goes from the display panel
24 through the planar structure 42, the capacitative structure, the
planar structure 44, and along the conductive path 48 to the system
ground 41.
[0031] FIG. 6 shows the capacitative structure 50 formed by the
hinge 30. More specifically the capacitative structure 50 is formed
by the overlapping portions of the first cylindrical body 32 and
second cylindrical body 34. Preferably the overlapping arc 52 is at
least 135.degree.. In a best mode embodiment at least a portion of
the capacitative structure 50 extends the length of the first
cylindrical body 32 and second cylindrical body 34. Preferably the
capacitative structure 50 is formed over at least one-third the
length of the first cylindrical body 32 and second cylindrical body
34.
[0032] In one embodiment the first generally cylindrical body 32
and second generally cylindrical body 34 are formed to be in close
contact. In such embodiment the bodies 32, 34 preferably are formed
by conventional electronic contact materials, such as a beryllium
copper alloy or an alloy including nickel, copper or silver. Such
materials are selected not only for their electrical properties,
but also for their wear, as they shall be moving relative to each
other during the opening and the closing of the display compartment
12. If at the atomic level the cylindrical bodies 32, 34 were in
contact over their entire surface, the friction would be too great
to open and close the display. Instead there are areas of point
contact and other areas of non-contact. However, over the frequency
range of interest (e.g., 30 MHz to 1 Ghz), the capacitative
structure 50 has low impedance.
[0033] FIG. 7 shows an alternative embodiment a dielectric material
50 occurs between the two conductive bodies 32, 34. In one
embodiment the dielectric material is an air gap. In such
embodiment a clutch mechanism also is included for holding the
display compartment in place at various open positions. In another
embodiment a solid material, such as mylar is included as the
dielectric. Other conventional dielectric materials also may be
used. In such embodiments, any conductive material may be used for
the cylindrical bodies 32, 34. The dielectric and conductive
materials should also be selected to resist corrosion as they may
be exposed to moisture (e.g., from the touch of the user).
[0034] Meritorious and Advantageous Effects
[0035] One advantage of the invention is that a low impedance
return path is provided between a display compartment and a
microcomputer compartment at high frequencies (e.g., 30 MHz and
above). The result is reduced EMI emissions at pertinent
frequencies.
[0036] Although a preferred embodiment of the invention has been
illustrated and described, various alternatives, modifications and
equivalents may be used. Therefore, the foregoing description
should not be taken as limiting the scope of the inventions which
are defined by the appended claims.
* * * * *