U.S. patent application number 12/459740 was filed with the patent office on 2010-02-04 for versatile system for multimode, wireless communication receiver with zif and near-zif operations.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Michael L. Brobston, Seong Eun Kim, Steven Loh, Weon Ki Yoon.
Application Number | 20100029324 12/459740 |
Document ID | / |
Family ID | 36971684 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100029324 |
Kind Code |
A1 |
Brobston; Michael L. ; et
al. |
February 4, 2010 |
Versatile system for multimode, wireless communication receiver
with ZIF and near-ZIF operations
Abstract
An architecture for a receiver component in a wireless
communications system is disclosed--one that supports both zero
intermediate frequency (ZIF) and near-zero intermediate frequency
(NZIF) operation. The architecture provides a down-conversion
segment, and a local oscillator segment operatively associated with
the down-conversion segment. An analog-to-digital conversion (ADC)
segment is adapted to receive signals from the down-conversion
segment and introduce the signals into a digital intermediate
frequency (DIF) construct. The DIF construct performs a DC offset
compensation or DC residue filtering on NZIF-based signals, and
droop or mismatch compensation. Image removal is performed on
NZIF-based signals, and DC offset compensation is performed on
ZIF-based signals. Compensated signals are amplified to some
nominal or desired level, and interpolation filtering of the
amplified signals is performed prior to transmission thereof.
Inventors: |
Brobston; Michael L.;
(Allen, TX) ; Loh; Steven; (Plano, TX) ;
Kim; Seong Eun; (Plano, TX) ; Yoon; Weon Ki;
(Hillsboro, OR) |
Correspondence
Address: |
DOCKET CLERK
P.O. DRAWER 800889
DALLAS
TX
75380
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-city
KR
|
Family ID: |
36971684 |
Appl. No.: |
12/459740 |
Filed: |
July 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11326124 |
Jan 5, 2006 |
7558550 |
|
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12459740 |
|
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|
|
60653780 |
Feb 17, 2005 |
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Current U.S.
Class: |
455/552.1 ;
455/232.1; 455/323 |
Current CPC
Class: |
H04B 1/30 20130101 |
Class at
Publication: |
455/552.1 ;
455/323; 455/232.1 |
International
Class: |
H04M 1/00 20060101
H04M001/00; H04B 1/26 20060101 H04B001/26 |
Claims
1. A wireless communications device, supporting both zero
intermediate frequency (ZIF) and near-zero intermediate frequency
(NZIF) operation, the device comprising: a down-conversion segment;
a programmable synthesizer component operatively associated with a
local oscillator segment; the local oscillator segment operatively
associated with the down-conversion segment; an analog-to-digital
conversion (ADC) segment adapted to receive signals from the
down-conversion segment; a digital intermediate frequency construct
adapted to receive digital signals from the ADC segment; and a
digital to analog segment adapted to receive digital signals from
the digital intermediate frequency construct.
2. The device of claim 1, wherein the wireless communications
device supports Wideband Code Division Multiple Access (WCDMA)
operation mode.
3. The device of claim 1, wherein the wireless communications
device supports Global System for Mobile communications (GSM)
operation mode.
4. The device of claim 1, wherein the wireless communications
device supports both Wideband Code Division Multiple Access (WCDMA)
and Global System for Mobile communications (GSM) operation
modes.
5. The device of claim 1, wherein the down conversion segment
comprises a demodulation element having the local oscillator
segment operatively associated therewith.
6. The device of claim 1, wherein the reconfigurable digital
intermediate frequency construct comprises: an analog DC offset
compensation element; a digital mixer element; a channel filtering
element; a digital DC offset compensation element; and a variable
gain amplification element.
7. The device of claim 6, wherein the digital mixer element is
driven by an oscillator element.
8. The device of claim 6, wherein the digital mixer element is
bypassed or disabled during ZIF operation.
9-19. (canceled)
20. A receiver for use in a wireless communications device,
supporting both zero intermediate frequency (ZIF) and near-zero
intermediate frequency (NZIF) operation, the receiver comprising:
an RF front-end segment including a down-conversion segment; a
programmable synthesizer component operatively associated with a
local oscillator segment; the local oscillator segment operatively
associated with the down-conversion segment; an analog-to-digital
conversion (ADC) segment adapted to receive signals from the
down-conversion segment; a digital intermediate frequency construct
adapted to receive digital signals from the ADC segment; and a
digital to analog segment adapted to receive digital signals from
the digital intermediate frequency construct.
21. The receiver of claim 20, wherein the wireless communications
device supports Wideband Code Division Multiple Access (WCDMA)
operation mode.
22. The receiver of claim 20, wherein the wireless communications
device supports Global System for Mobile communications (GSM)
operation mode.
23. The receiver of claim 20, wherein the wireless communications
device supports both Wideband Code Division Multiple Access (WCDMA)
and Global System for Mobile communications (GSM) operation
modes.
24. The receiver of claim 20, wherein the down conversion segment
comprises a demodulation element having the local oscillator
segment operatively associated therewith.
25. The receiver of claim 20, wherein the reconfigurable digital
intermediate frequency construct comprises: an analog DC offset
compensation element; a digital mixer element; a channel filtering
element; a digital DC offset compensation element; and a variable
gain amplification element.
26. The receiver of claim 25, wherein the digital mixer element is
driven by an oscillator element.
27. The receiver of claim 25, wherein the digital mixer element is
bypassed or disabled during ZIF operation.
28. The receiver of claim 25, wherein the RF front-end segment
further includes a low noise amplifier segment.
29. A for processing a signal in a receiver for use in a wireless
communications device, supporting both zero intermediate frequency
(ZIF) and near-zero intermediate frequency (NZIF) operation, the
method comprising: receiving a plurality of signals; converting the
received signals into a digital form; processing the received
signals along at least two paths; performing mismatch compensation
on the received signals; performing coarse gain adjustment on the
received signals; amplifying the adjusted signals to a specified
level; and performing interpolation filtering of the amplified
signals.
30. The method of claim 29, further comprising: performing DC
offset compensation on NZIF-based signals; and performing at least
one of droop compensation and cascaded integrator-comb filtering on
the received signals.
31. The method of claim 29, further comprising performing image
rejection on NZIF-based signals.
Description
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY
[0001] The present application is related to U.S. Provisional
Patent No. 60/653,780, filed Feb. 17, 2005, entitled "Mobile
Terminal Multi-Mode Common Core Receiver with Configurable Direct
Downconversion and Near-ZIF Architecture". U.S. Provisional Patent
No. 60/653,780 is assigned to the assignee of the present
application and is hereby incorporated by reference into the
present disclosure as if fully set forth herein. The present
application hereby claims priority under 35 U.S.C. .sctn.119(e) to
U.S. Provisional Patent No. 60/653,780.
TECHNICAL FIELD OF THE INVENTION
[0002] The present application relates generally to the field of
wireless communications technologies and, more particularly, to
apparatus and methods for providing a single receiver that supports
both zero intermediate frequency (ZIF) and Near-ZIF operational
modes.
BACKGROUND OF THE INVENTION
[0003] Increasing demand for more powerful and convenient data and
information communication has spawned a number of advancements in
communications technologies, particularly in wireless communication
technologies. A number of technologies have been developed to
provide the convenience of wireless communication in a variety of
applications, in various locations. This proliferation of wireless
communication has given rise to a number of manufacturing and
operational considerations.
[0004] There are an increasing number of fixed and portable
wireless applications that require, or can benefit from, operation
in accordance with a plurality of communications standards or
operational protocols. This is commonly referred to as multi-mode
operation. Multi-mode capabilities in wireless communication
products allow end-users to purchase a single product that may be
used in a variety of locations for reasonable length of
time--despite any proliferation of or changes in new technologies
or standards. Multi-mode capabilities across wireless networks
allow providers to offer new, advanced services to a broader range
of customers, while fulfilling the needs of their legacy customer
base. Thus, wireless base stations and mobile devices need to
support portions of emerging standards, as well as revenue
producing existing standards for backward compatibility.
[0005] Although multi-mode support can be very desirable, it also
presents a number of challenges when designing a multimode
product--particularly when attempting to address the needs of
disparate or competing communications standards or technologies.
Commonly, the particular standard or technology associated with
each "mode" of a multi-mode device requires substantially unique
componentry or circuitry. As such, wireless system designers very
rarely--if ever--provide a truly universal, single multi-mode
device. Usually, conventional multi-mode systems comprise several
devices--each designed to address one particular communications
standard or technology--that are packaged together as a single
multi-mode product.
[0006] Consider, for example, two such technologies which are
continuously growing in usage and deployment and, as such, are
increasingly targeted for inclusion in multi-mode devices. Wideband
Code Division Multiple Access (WCDMA) is a third-generation (3G),
wideband, spread-spectrum mobile telecommunication air interface
that utilizes code division multiple access multiplexing (CDMA).
GSM (Global System for Mobile communications) is currently one of
the most popular standards for mobile phones in the world. Although
GSM continues to evolve, it is widely regarded as a narrow-band,
second generation (2G) technology. Various improvements nonetheless
seek to keep GSM viable--such as higher speed data transmission
introduced with Enhanced Data rates for GSM Evolution (EDGE)
technology.
[0007] WCDMA has a much more complex physical layer structure and
operation than GSM--due, at least in part, to its much wider signal
band. Along with additional complexity come a number of additional
specifications and requirements. For example, WCDMA systems
commonly utilize a ZIF (zero intermediate frequency) based
architecture--due to their wideband operation--whereas GSM systems
typically rely upon near-ZIF (NZIF) architectures compatible with
their relatively narrow band operations.
[0008] In order to design a multi-mode product that conforms to
both architecture and operational schemes, conventional devices and
systems usually combine many different components and modules, each
targeted to support operation and processing in either a ZIF or
NZIF protocol. Most such conventional components and modules are
designed to function only in one operational context--either the
wideband (ZIF) or the narrow band (NZIF)--not in both. As a result,
a large number of inefficiencies are introduced to the production
and operation of conventional multi-mode devices, which increase
device and system costs and introduce a greater potential for
system reliability and performance problems.
[0009] As a result, there is a need for a system that provides a
single receiver or transceiver architecture that efficiently
supports both wideband and narrow band operational modes (i.e., ZIF
and NZIF)--obviating the need for multiple, specialized components
within a single multi-mode device--while providing efficient and
dependable wireless communications, in an easy and cost-effective
manner.
SUMMARY OF THE INVENTION
[0010] A versatile system, comprising various apparatus and
methods, is provided for a single receiver or transceiver
architecture that efficiently supports both wideband and narrow
band operational modes--particularly ZIF and near-ZIF (NZIF). The
system of the present disclosure provides a reconfigurable digital
IF (DIF) construct, within a multi-mode receiver architecture. The
DIF construct provides an optimal receiver down conversion
technique for operations in a given mode. The system of the present
disclosure provides for the optimization of performance for various
modes, while at the same time easing receiver processing functions.
The system of the present disclosure thus provides a single,
common-core receiver that performs equivalent to multiple,
dedicated receivers, with no compromise in signal processing
quality.
[0011] Specifically, an architecture for a receiver component in a
wireless communications system is disclosed--one that supports both
zero intermediate frequency (ZIF) and near-zero intermediate
frequency (NZIF) operation. The architecture provides a
down-conversion segment, and a local oscillator segment operatively
associated with the down-conversion segment. An analog-to-digital
conversion (ADC) segment is adapted to receive signals from the
down-conversion segment and introduce the signals into a digital
intermediate frequency (DIF) construct. The DIF construct performs
DC offset compensation or DC residue filtering on NZIF-based
signals--as well as droop or mismatch compensation. Image filtering
is performed on NZIF-based signals, and DC offset compensation is
performed on ZIF-based signals. Compensated signals are amplified
to some nominal, or desired level, and interpolation filtering of
the amplified signals is performed prior to transmission
thereof.
[0012] Before undertaking the DETAILED DESCRIPTION OF THE INVENTION
below, it may be advantageous to set forth definitions of certain
words and phrases used throughout this patent document: the terms
"include" and "comprise," as well as derivatives thereof, mean
inclusion without limitation; the term "or," is inclusive, meaning
and/or; the phrases "associated with" and "associated therewith,"
as well as derivatives thereof, may mean to include, be included
within, interconnect with, contain, be contained within, connect to
or with, couple to or with, be communicable with, cooperate with,
interleave, juxtapose, be proximate to, be bound to or with, have,
have a property of, or the like; and the terms "construct",
"element" or "component" mean any device, system or part thereof
that control or perform at least one operation, and may be
implemented in hardware, firmware or software, or some combination
of at least two of the same. It should be noted that the
functionality associated with any particular construct or element
may be centralized or distributed, whether locally or remotely.
Definitions for certain words and phrases are provided throughout
this patent document, those of ordinary skill in the art should
understand that in many, if not most instances, such definitions
apply to prior, as well as future uses of such defined words and
phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals represent like parts:
[0014] FIG. 1 illustrates one embodiment of wireless communications
receiver system in accordance with the present disclosure; and
[0015] FIG. 2 illustrates an embodiment of a multi-mode signal
processing segment in accordance with the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIGS. 1 and 2, discussed below, and the various embodiments
used to describe the principles of the present disclosure in this
patent document are by way of illustration only and should not be
construed in any way to limit the scope of the disclosure. Those
skilled in the art will understand that the principles of the
present disclosure may be implemented in any suitably arranged
receiver structure, whether such structure relies upon ZIF, NZIF or
some other desired operational protocols.
[0017] The following discloses a versatile system, comprising
various architectures, apparatus and methods for providing a single
multimode receiver--whether as a stand-alone receiver, or as part
of a transceiver device. This multimode architecture efficiently
supports both wideband and narrow band operational
modes--especially where such operations are based upon ZIF and NZIF
protocols.
[0018] The system of the present disclosure provides a
reconfigurable digital IF (DIF) construct, implemented within a
multi-mode receiver. The DIF construct provides--regardless of
whether a ZIF or NZIF based operational mode is active--an optimal
receiver down conversion for efficient signal processing. Utilizing
the DIF construct of the present disclosure, a single, common-core
receiver performs equivalent to multiple, dedicated receivers, with
no compromise in signal processing quality. The architecture of the
present disclosure provides for optimization of performance for
various modes and, at the same time, reduces the volume of receiver
processing functions needed to realize such optimization. This
invention thus provides a single common core receiver that
functions as effectively, and more efficiently, than multiple
receiver multi-mode systems--with no compromise in signal
processing quality. This greatly reduces system costs and
inefficiencies while improving operational reliability.
[0019] The system of the present disclosure provides a mobile
terminal receiver architecture that can be conveniently
reconfigured by software to perform either a direct down
conversion--commonly preferred for wide band systems and referred
to as ZIF--or a near-ZIF (NZIF) down conversion, having certain
advantages for narrow band systems. The system of the present
disclosure recognizes that the selection of a one down conversion
technique over another is based upon a wide variety of
factors--particularly any receiver test specifications required by
an applicable standard.
[0020] According to the present disclosure, and as illustrated now
in reference to FIG. 1, a multimode receiver component 100
comprises an analog RF front-end segment 102, having a low noise
amplifier segment 104 and a down-conversion segment 106. In order
for segment 106 to successfully accommodate two or more different
down-conversion schemes, a local oscillator (LO) for down-converter
segment 106 needs to be highly versatile and adaptable.
[0021] In response, the system of the present disclosure provides a
programmable synthesizer component 108 (e.g., a phase-locked loop
(PLL) based device, either fractional or integer based) in
conjunction with a widely tunable oscillator element 110. Element
110 then feeds a mixer/demodulation element 112. Element 112 may be
somewhat more complex than a comparable function in conventional
single mode system, however, the present system recognizes that
since the difference in ZIF and NZIF operation is usually
relatively small (e.g., about 100 kHz.about.200 kHz), this is not
an inhibiting design challenge for such an element.
[0022] The rest of analog segment 102 comprises an analog variable
gain amplifier (VGA) block 114, and an analog-to-digital converter
(ADC) block 116 to digitize signals being processed. Programmable
low-pass filters 118 (LPFs) are implemented at the output portion
of both the down converter block 106 and VGA block 114, to provide
blocking and anti-aliasing functions. From these segments, signals
pass to the DIF construct 120, which processes those signals in
digital domain (as described hereinafter) before outputting the
signals to a baseband modem (not shown) via digital to analog
converter (DAC) elements 122.
[0023] Referring now to FIG. 2, one illustrative embodiment of a
DIF construct 200 in accord with the present system is depicted.
Construct 200 may be provided, for example, for multimode
utilization with WCDMA ZIF and GSM/EDGE NZIF based systems.
Construct 200 may be provided such that it uses the same data bus
and width for both ZIF and NZIF modes. Depending upon the
communication and processing technologies of a given application,
construct 200 may comprise separate but parallel paths for
processing different signal components. For example, in the
embodiment depicted in FIG. 2, construct 200 illustratively
comprises signal processing paths 202 and 204 for parallel
processing of quadrature components (I) and (Q), respectively.
[0024] Construct 200 further comprises an IF to baseband digital
mixer element 206. Mixer element 206 is utilized for NZIF
operation, as driven by a numerically controlled oscillator (NCO)
208, and is bypassed or disabled for ZIF operation. Mixer 206
provides complex down-conversion necessary for image filtering when
operating at NZIF frequency.
[0025] A DC offset correction element 210 is also provided. DC
offset correction 210 is utilized in NZIF operation but may not be
needed at an IF frequency of 170 kHz or above. ZIF operation will
utilize a DC residual correction element 212--provided at some
point after processing by FIR filters 218, 222 and 226.
[0026] As signals are introduced to construct 200 via inputs 214, a
signal may first be processed by a first filtering element 216,
prior to any offset compensation performed by element 210. As
depicted in FIG. 2, filtering element 216 comprises a cascaded
integrator-comb (CIC) type of filter. The specific topology and
magnitude of element 216 may be varied to match design-requirements
of a given application. As depicted in FIG. 2, element 216
comprises a 5-stage CIC filter. Filter 216 has a programmable
decimation rate (M) that may be provided or determined based on the
incoming ADC rate.
[0027] From element 216, signal proceeds through offset
compensation 210, and may then be filtered again by second
filtering element 218 before proceeding to a mismatch compensation
element 220. As depicted in FIG. 2, element 218 comprises a
symmetric finite impulse response (FIR) type filter, providing
droop compensation of prior analog LPFs 118 or CIC filter 216.
After compensation by element 218, signal proceeds through mismatch
compensation 200 to mixer element 206. After processing by element
206, signal may then proceed through a channel filtering element
222 before processing by a gain adjust element 224. As depicted in
FIG. 2, element 222 comprises a symmetric FIR type filter.
[0028] Element 224 provides a coarse gain adjustment (i.e.,
switchable step gain), from which signal may then proceed through
another channel filtering element 226, before proceeding to
variable gain amplification (VGA) element 228. As depicted in FIG.
2, element 226 also comprises a symmetric FIR type filter. Once
signal has been processed through VGA element 228, it may then
proceed through one or more forms of interpolation filter elements
230, 232, before being output 234 from construct 200. As depicted
in FIG. 2, element 230 comprises a symmetric FIR type interpolation
filter, while element 232 comprises a 5-stage CIC interpolation
component. Element 232 has a programmable interpolation rate (N)
that may be determined or provided based upon the rate of a DAC to
which signals are output 234.
[0029] VGA element 228 may be provided to maintain some nominal
signal level into a baseband modem from output 234. Digital channel
filtering elements 222 and 226 may be provided in a programmable
format or configuration--enabling those elements to be
reconfigurable or optimizable for signals in different modes with
various bandwidths. The FIR filters of those elements may be
designed to attenuate close-in blockers--including adjacent channel
interferers, in GSM/EDGE, as well as any up-converted residual DC
spurious noise from use of an NCO. These filters may also be
designed or configured to perform amplitude equalization on
frequency responses from, for example, analog low pass filters at
the output of down-converter and VGA 228 output--to address any
amplitude droop effect on a signal from being at a non-zero IF
frequency.
[0030] In most embodiments, both ZIF and NZIF configurations are
provided without any image rejection filtering. As such, image
rejection is of particular concern in NZIF operation. For example,
a minimum of about 35 dB of image rejection may be required when
operating in GSM/EDGE mode, with an NZIF configuration. Given
certain tolerances in I/Q mismatch, complex filtering in the
digital domain is a preferable approach, and more deterministic in
image reduction, which would otherwise be very challenging to
provide in the analog domain.
[0031] Given the versatility of the present system, a number of
application-specific or general-purpose-adaptations may be readily
implemented. For example, a receiver synthesizer may be exploited
to adopt an NZIF configuration at greater than 110 kHz for
GSM/EDGE--providing room for the FIR filters of construct 200 to
block out any upcoverted DC spurs that may occur at 110 kHz, since
baseband require signal bandwidth for EDGE processing may be
greater than 100 kHz. In some instances, it may be possible that
analog filter bandwidth may be constrained by amplitude droop or
group delay effects on a signal, while at the same time maintaining
selectivity. Advantageously, NZIF arrangement of construct 200 is
not required to perform any digital DC correction if the IF is high
enough (e.g., 170 kHz or above)--since any upcoverted residual DC
component may be sufficiently filtered out, and digital functional
blocks can be conceptualized as being perfectly linear.
[0032] Another advantage of an NZIF arrangement of the present
invention is that--in a narrowband system like GSM/EDGE--a
high-pass transfer function of an analog DC correction loop will
induce little to no degradation of a signal, especially if an IF of
greater than 135 kHz is used. This provides more accurate
corrections with the receiver fully turned on and the dynamics of
high signals and blockers, allowing for IM2 product reduction
during active burst for better AM suppression. In certain ZIF
operation instance, such as a broadband system like WCDMA, any
high-pass effect on a signal is relatively insignificant.
Primarily, a wider overall bandwidth, in conjunction with
specifications that require close-in blockers that can become
challenging to reduce using analog filters with high cut-off
corners, prohibit WCDMA from operating in an NZIF mode.
[0033] It should now be easily appreciated by one of skill in the
art that the system of the present disclosure provides and
comprehends a wide array of variations and combinations easily
adapted to a number of multi-mode, ZIF/NZIF applications. The
relative arrangement and orientations of certain filtering or
compensation elements may be provided in any manner suitable for a
particular application. All such variations and modifications are
hereby comprehended. It should also be appreciated that the system
of the present disclosure may be readily implemented in any desired
design or fabrication processes. The constituent members or
components of this system may be produced or provided using any
suitable hardware, software, or combination of hardware and
software.
[0034] The embodiments and examples set forth herein are therefore
presented to best explain the present invention and its practical
application, and to thereby enable those skilled in the art to make
and utilize the system of the present disclosure. The description
as set forth herein is therefore not intended to be exhaustive or
to limit any invention to a precise form disclosed. As stated
throughout, many modifications and variations are possible in light
of the above teaching without departing from the spirit and scope
of the following claims.
* * * * *