U.S. patent application number 17/088306 was filed with the patent office on 2022-05-05 for systems and methods for varying an impedance of a cable.
This patent application is currently assigned to Dell Products L.P.. The applicant listed for this patent is Dell Products L.P.. Invention is credited to Sandor FARKAS, Bhyrav M. MUTNURY.
Application Number | 20220140819 17/088306 |
Document ID | / |
Family ID | 1000005236538 |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220140819 |
Kind Code |
A1 |
FARKAS; Sandor ; et
al. |
May 5, 2022 |
SYSTEMS AND METHODS FOR VARYING AN IMPEDANCE OF A CABLE
Abstract
A system may include a transmitter, a receiver, a cable coupled
between the transmitter and the receiver and having two wires for
communicating a differential signal from the transmitter to the
receiver, and a direct-current (DC) voltage source coupled to a
first wire of the two wires of the cable and configured to apply a
variable DC offset voltage to the first wire in order to vary an
impedance of the cable as a function of the variable DC offset
voltage.
Inventors: |
FARKAS; Sandor; (Round Rock,
TX) ; MUTNURY; Bhyrav M.; (Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dell Products L.P. |
Round Rock |
TX |
US |
|
|
Assignee: |
Dell Products L.P.
Round Rock
TX
|
Family ID: |
1000005236538 |
Appl. No.: |
17/088306 |
Filed: |
November 3, 2020 |
Current U.S.
Class: |
327/306 |
Current CPC
Class: |
H03K 3/017 20130101;
H04B 3/548 20130101; H04B 3/542 20130101; H04L 25/026 20130101;
H03H 7/06 20130101 |
International
Class: |
H03K 3/017 20060101
H03K003/017; H03H 7/06 20060101 H03H007/06 |
Claims
1. A system, comprising: a transmitter; a receiver; a cable coupled
between the transmitter and the receiver and having two wires for
communicating a differential signal from the transmitter to the
receiver; and a direct-current (DC) voltage source coupled to a
first wire of the two wires of the cable and configured to apply a
variable DC offset voltage to the first wire in order to vary an
impedance of the cable as a function of the variable DC offset
voltage, wherein the DC voltage source comprises a pulse-width
modulation signal generator in combination with a
resistive-capacitive filter configured to generate the variable DC
offset voltage as a function of a duty cycle of a pulse-width
modulation signal generated by the pulse-width modulation signal
generator.
2. (canceled)
3. The system of claim 1, wherein the DC voltage source further
comprises an inductor coupled between the first wire and the
pulse-width modulation signal generator in combination with the
resistive-capacitive filter.
4. The system of claim 1, further comprising an alternating current
(AC) coupling capacitor coupled between a first terminal of the
receiver and the first wire.
5. The system of claim 4, further comprising a second AC coupling
capacitor coupled between a second terminal of the receiver and a
second wire of the two wires of the cable.
6. A method, comprising: coupling a cable between a transmitter and
a receiver, the cable having two wires for communicating a
differential signal from the transmitter to the receiver; applying
a variable direct-current (DC) offset voltage to a first wire of
the two wires of the cable in order to vary an impedance of the
cable as a function of the variable DC offset voltage; and
generating the variable DC offset voltage as a function of a duty
cycle of a pulse-width modulation signal generated by a pulse-width
modulation signal generator in combination with a
resistive-capacitive filter.
7. (canceled)
8. The method of claim 6, further comprising coupling an inductor
between the first wire and the pulse-width modulation signal
generator in combination with the resistive-capacitive filter.
9. The method of claim 6, further coupling an alternating current
(AC) coupling capacitor between a first terminal of the receiver
and the first wire.
10. The method of claim 9, further comprising coupling a second AC
coupling capacitor between a second terminal of the receiver and a
second wire of the two wires of the cable.
Description
TECHNICAL FIELD
[0001] The present disclosure relates in general to information
handling systems, and more particularly to systems and methods for
varying an impedance of a cable.
BACKGROUND
[0002] As the value and use of information continues to increase,
individuals and businesses seek additional ways to process and
store information. One option available to users is information
handling systems. An information handling system generally
processes, compiles, stores, and/or communicates information or
data for business, personal, or other purposes thereby allowing
users to take advantage of the value of the information. Because
technology and information handling needs and requirements vary
between different users or applications, information handling
systems may also vary regarding what information is handled, how
the information is handled, how much information is processed,
stored, or communicated, and how quickly and efficiently the
information may be processed, stored, or communicated. The
variations in information handling systems allow for information
handling systems to be general or configured for a specific user or
specific use such as financial transaction processing, airline
reservations, enterprise data storage, or global communications. In
addition, information handling systems may include a variety of
hardware and software components that may be configured to process,
store, and communicate information and may include one or more
computer systems, data storage systems, and networking systems.
[0003] In many applications, one or multiple information handling
servers may be installed within a single chassis, housing,
enclosure, or rack. Communication between or within servers and/or
between enclosures may often be accomplished via cables, and many
communications standards and protocols employ a copper cable
implementation for differential signaling.
[0004] One challenge in using cables in information handling
systems is that not all communications fabrics are optimized for
the same impedance. For example, Peripheral Component Interconnect
Express (PCIe) may be optimized with 85-ohm cables, while Serial
Attached Small Computer System Interface (SAS) may be optimized
with 100-ohm cables. Another challenge is the sheer number of
assemblies and part numbers needed to optimize interfaces with
varying impedance requirements. Accordingly, there exists a chance
of error of building an information handling system with the wrong
cable.
[0005] With the advent of more complicated and advanced
communication interfaces, it is becoming more difficult to satisfy
requirements of multiple interfaces that require different
impedances. For example, a flexible input/output (I/O) port may be
configured for PCIe or Serial Advanced Technology Attachment
(SATA), but the cable type may limit to one or the other. One
existing solution is to use a cable with 92 ohms of impedance,
which is the approximate mean of 85 ohms and 100 ohms. However,
this solution is often less than desirable, as use of such
impedance may still lead to signal integrity issues and impedance
discontinuities.
SUMMARY
[0006] In accordance with the teachings of the present disclosure,
the disadvantages and problems associated with traditional
approaches to use of cables in an information handling system may
be substantially reduced or eliminated.
[0007] In accordance with embodiments of the present disclosure, a
system may include a transmitter, a receiver, a cable coupled
between the transmitter and the receiver and having two wires for
communicating a differential signal from the transmitter to the
receiver, and a direct-current (DC) voltage source coupled to a
first wire of the two wires of the cable and configured to apply a
variable DC offset voltage to the first wire in order to vary an
impedance of the cable as a function of the variable DC offset
voltage.
[0008] In accordance with these and other embodiments of the
present disclosure, a method may include coupling a cable between a
transmitter and a receiver, the cable having two wires for
communicating a differential signal from the transmitter to the
receiver and applying a variable direct-current (DC) offset voltage
to a first wire of the two wires of the cable in order to vary an
impedance of the cable as a function of the variable DC offset
voltage.
[0009] Technical advantages of the present disclosure may be
readily apparent to one skilled in the art from the figures,
description and claims included herein. The objects and advantages
of the embodiments will be realized and achieved at least by the
elements, features, and combinations particularly pointed out in
the claims.
[0010] It is to be understood that both the foregoing general
description and the following detailed description are examples and
explanatory and are not restrictive of the claims set forth in this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings, in
which like reference numbers indicate like features, and
wherein:
[0012] FIG. 1 illustrates a system comprising a plurality of
chassis, each chassis comprising at least one information handling
system, in accordance with embodiments of the present
disclosure;
[0013] FIG. 2 illustrates a system for varying impedance of a
cable, in accordance with embodiments of the present disclosure;
and
[0014] FIG. 3 illustrates an example graph depicting relative
permittivity versus direct-current bias voltage in a cable, in
accordance with embodiments of the present disclosure.
DETAILED DESCRIPTION
[0015] Preferred embodiments and their advantages are best
understood by reference to FIGS. 1 through 3, wherein like numbers
are used to indicate like and corresponding parts.
[0016] For purposes of this disclosure, an information handling
system may include any instrumentality or aggregate of
instrumentalities operable to compute, classify, process, transmit,
receive, retrieve, originate, switch, store, display, manifest,
detect, record, reproduce, handle, or utilize any form of
information, intelligence, or data for business, scientific,
control, or other purposes. For example, an information handling
system may be a personal computer, a network storage device, or any
other suitable device and may vary in size, shape, performance,
functionality, and price. The information handling system may
include random access memory (RAM), one or more processing
resources such as a central processing unit (CPU) or hardware or
software control logic, ROM, and/or other types of nonvolatile
memory. Additional components of the information handling system
may include one or more disk drives, one or more network ports for
communicating with external devices as well as various input and
output (I/O) devices, such as a keyboard, a mouse, and a video
display. The information handling system may also include one or
more buses operable to transmit communications between the various
hardware components.
[0017] For the purposes of this disclosure, information handling
resources may broadly refer to any component system, device or
apparatus of an information handling system, including without
limitation processors, service processors, basic input/output
systems, buses, memories, I/O devices and/or interfaces, storage
resources, network interfaces, motherboards, air movers, sensors,
power supplies, and/or any other components and/or elements of an
information handling system.
[0018] FIG. 1 illustrates a system 100 comprising a plurality of
chassis 101, each chassis 101 comprising at least one information
handling system 102, in accordance with embodiments of the present
disclosure. Each chassis 101 may be an enclosure that serves as a
container for various information handling systems 102 and
information handling resources 104, and may be constructed from
steel, aluminum, plastic, and/or any other suitable material.
Although the term "chassis" is used, a chassis 101 may also be
referred to as a case, cabinet, tower, box, enclosure, and/or
housing. In certain embodiments, a chassis 101 may be configured to
hold and/or provide power to one or more information handling
systems 102 and/or information handling resources 104.
[0019] In some embodiments, one or more of information handling
systems 102 may comprise servers. For example, in some embodiments,
information handling systems 102 may comprise rack servers and each
chassis 101 may comprise a rack configured to house such rack
servers. As shown in FIG. 1, each information handling system 102
may include one or more information handling resources 104. An
information handling resource 104 may include any component system,
device or apparatus of an information handling system 102,
including without limitation processors, service processors, basic
input/output systems, buses, memories, I/O devices and/or
interfaces, storage resources, network interfaces, motherboards,
air movers, sensors, power supplies, and/or any other components
and/or elements of an information handling system. For example, in
some embodiments, an information handling resource 104 of an
information handling system 102 may comprise a processor. Such
processor may include any system, device, or apparatus configured
to interpret and/or execute program instructions and/or process
data, and may include, without limitation, a microprocessor,
microcontroller, digital signal processor (DSP), application
specific integrated circuit (ASIC), or any other digital or analog
circuitry configured to interpret and/or execute program
instructions and/or process data. In some embodiments, a processor
may interpret and/or execute program instructions and/or process
data stored in a memory and/or another information handling
resource of an information handling system 102.
[0020] In these and other embodiments, an information handling
resource 104 of an information handling system 102 may comprise a
memory. Such a memory may be communicatively coupled to an
associated processor and may include any system, device, or
apparatus configured to retain program instructions and/or data for
a period of time (e.g., computer-readable media). A memory may
include RAM, EEPROM, a PCMCIA card, flash memory, magnetic storage,
opto-magnetic storage, or any suitable selection and/or array of
volatile or non-volatile memory that retains data after power to an
associated information handling system 102 is turned off.
[0021] In addition to a processor and/or a memory, an information
handling system 102 may include one or more other information
handling resources.
[0022] As shown in FIG. 1, information handling resources 104 may
be communicatively coupled to each other via a cable 106, whether
such information handling resources 104 are within different
information handling systems 102 in the same chassis 101, or are in
different chassis 101. A cable 106 may include any suitable
assembly of two or more electrically-conductive wires running side
by side to carry one or more signals between information handling
resources. In some embodiments, cable 106 may comprise a cable with
a varying impedance controlled by a direct-current (DC) voltage
source, as described in greater detail below.
[0023] FIG. 2 illustrates a system 200 for varying impedance of a
cable 106, in accordance with embodiments of the present
disclosure. As shown in FIG. 2, system 200 may include a
transmitter information handling resource 104A, a receiver
information handling resource 104B, a cable 106 coupled between
transmitter information handling resource 104A and receiver
information handling resource 104B, and a DC voltage source 202
configured to control the impedance of cable 106.
[0024] As shown in FIG. 2, transmitter information handling
resource 104A may include a driver 204 configured to drive a signal
onto cable 106. Transmitter information handling resource 104A may
also include alternating current (AC) coupling capacitors 206, each
AC coupling capacitor 206 coupled between a respective wire of
cable 106 and a respective terminal of driver 204.
[0025] As also shown in FIG. 2, receiver information handling
resource 104B may also include a receiver 208 configured to receive
a signal communicated over cable 106. Receiver information handling
resource 104B may also include AC coupling capacitors 210, each AC
coupling capacitor 210 coupled between a respective wire of cable
106 and a respective terminal of receiver 208. The AC coupling
capacitor 210 coupled to the wire of cable 106 to which DC voltage
source 202 is coupled may serve to remove DC offset voltage
V.sub.DC applied by DC voltage source 202 from the signal
communicated over cable 106. The other AC coupling capacitor 210,
which may be absent in some embodiments, may be used to maintain
balance in the differential communications channel implemented by
cable 106.
[0026] DC voltage source 202 may include any suitable system,
device, or apparatus configured to generate a variable DC voltage
offset V.sub.DC between the wires of cable 106. Although any
suitable architecture for DC voltage source 202 may be used in
accordance with this disclosure, an example architecture is shown
in FIG. 2 which includes a source block 212 including pulse-width
modulation (PWM) signal generator and resistive-capacitive (RC)
filter which may control variable DC voltage offset V.sub.DC by
varying a duty cycle of the PWM signal generated by the PWM signal
generator. In the example depicted in FIG. 2, DC voltage source 202
may also include an inductor 214 coupled between source block 212
and a wire of cable 106. Inductor 214 may enable injection of
variable DC voltage offset V.sub.DC without loading the
communications channel implemented by cable 106.
[0027] Varying variable DC voltage offset V.sub.DC may vary an
impedance of cable 106 due to the fact that a relative permittivity
D.sub.k of dielectric material of cable 106 may decrease with
increasing variable DC voltage offset V.sub.DC, as shown in FIG. 3.
FIG. 3 illustrates an example graph depicting relative permittivity
D.sub.k (in terms of a percent change in absolute permittivity) of
dielectric material of cable 106 versus variable DC voltage offset
V.sub.DC applied to cable 106, in accordance with embodiments of
the present disclosure. Thus, as variable DC voltage offset
V.sub.DC increases, the dielectric constant of the dielectric
material of cable 106 may decrease.
[0028] To explain this phenomenon, a dielectric constant of a
material may be defined by:
D k = E E - E in ##EQU00001##
[0029] Where E represents an electric field applied to material and
E.sub.in represents an induced electric field.
[0030] When the molecules of a dielectric material are polarized by
applying electric field E, the polarization generates a dipole
moment. Due to dipole moment of molecules, induced electric field
E.sub.in may be formed inside the dielectric material. The
polarization vector per unit volume may be given by dipole moment
P:
P=N.alpha..sub.eE.sub.in
where N represents a number of molecules per unit volume, which
contributes to dipole moment, and where .alpha..sub.e is a
polarizability. Corresponding to the dipole moment, a charge
density p, may be given by:
.rho.=P{circumflex over (n)}
where {circumflex over (n)} represents a unit vector.
[0031] When an applied voltage creates induced electric field
E.sub.in, then the polarization of the molecules may decrease as
they are aligned in the same direction. When the polarization
decreases, induced electric field E.sub.in may decrease. As shown
by the equation above for dielectric constant D.sub.k, when induced
electric field E.sub.in decreases, dielectric constant D.sub.k may
also decrease.
[0032] Impedance of cable 106 may be proportional to 1/ {square
root over (D.sub.k)} and thus, increasing variable DC voltage
offset V.sub.DC may increase impedance of cable 106. Thus, starting
with a nominal cable impedance of 85 ohms for cable 106, a suitable
variable DC voltage offset V.sub.DC may be applied to cable 106 to
increase its impedance to 92 ohms or 100 ohms in applications in
which such increased impedance is desired.
[0033] As used herein, when two or more elements are referred to as
"coupled" to one another, such term indicates that such two or more
elements are in electronic communication or mechanical
communication, as applicable, whether connected indirectly or
directly, with or without intervening elements.
[0034] This disclosure encompasses all changes, substitutions,
variations, alterations, and modifications to the example
embodiments herein that a person having ordinary skill in the art
would comprehend. Similarly, where appropriate, the appended claims
encompass all changes, substitutions, variations, alterations, and
modifications to the example embodiments herein that a person
having ordinary skill in the art would comprehend. Moreover,
reference in the appended claims to an apparatus or system or a
component of an apparatus or system being adapted to, arranged to,
capable of, configured to, enabled to, operable to, or operative to
perform a particular function encompasses that apparatus, system,
or component, whether or not it or that particular function is
activated, turned on, or unlocked, as long as that apparatus,
system, or component is so adapted, arranged, capable, configured,
enabled, operable, or operative. Accordingly, modifications,
additions, or omissions may be made to the systems, apparatuses,
and methods described herein without departing from the scope of
the disclosure. For example, the components of the systems and
apparatuses may be integrated or separated. Moreover, the
operations of the systems and apparatuses disclosed herein may be
performed by more, fewer, or other components and the methods
described may include more, fewer, or other steps. Additionally,
steps may be performed in any suitable order. As used in this
document, "each" refers to each member of a set or each member of a
subset of a set.
[0035] Although exemplary embodiments are illustrated in the
figures and described below, the principles of the present
disclosure may be implemented using any number of techniques,
whether currently known or not. The present disclosure should in no
way be limited to the exemplary implementations and techniques
illustrated in the drawings and described above.
[0036] Unless otherwise specifically noted, articles depicted in
the drawings are not necessarily drawn to scale.
[0037] All examples and conditional language recited herein are
intended for pedagogical objects to aid the reader in understanding
the disclosure and the concepts contributed by the inventor to
furthering the art, and are construed as being without limitation
to such specifically recited examples and conditions. Although
embodiments of the present disclosure have been described in
detail, it should be understood that various changes,
substitutions, and alterations could be made hereto without
departing from the spirit and scope of the disclosure.
[0038] Although specific advantages have been enumerated above,
various embodiments may include some, none, or all of the
enumerated advantages. Additionally, other technical advantages may
become readily apparent to one of ordinary skill in the art after
review of the foregoing figures and description.
[0039] To aid the Patent Office and any readers of any patent
issued on this application in interpreting the claims appended
hereto, applicants wish to note that they do not intend any of the
appended claims or claim elements to invoke 35 U.S.C. .sctn. 112(f)
unless the words "means for" or "step for" are explicitly used in
the particular claim.
* * * * *