(12)
`
`United States Patent
`Jin et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,693,974 B2
`*Feb. 17, 2004
`
`USOO6693974B2
`
`(54) ADAPTIVE DIGITAL PRE-DISTORTION
`CIRCUIT USING ADJACENT CHANNEL
`POWER PROFILE AND METHOD OF
`OPERATION
`(75) Inventors: Hang Jin, Plano, TX (US); Joseph R.
`Cleveland, Richardson, TX (US)
`
`(*) Notice:
`
`(73) Assignee: Samsung Electronics Co., Ltd., Suwon
`(KR)
`This patent issued on a continued pros
`ecution application filed under 37 CFR
`1.53(d), and is Subject to the twenty year
`pass" provisions of 35 U.S.C.
`
`Z.
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/368,895
`(22) Filed:
`Aug. 5, 1999
`(65)
`Prior Publication Data
`
`US 2003/0076894 A1 Apr. 24, 2003
`(51) Int. Cl." ................................................ H04L 25/49
`(52) U.S. Cl. ................
`... 375/297; 330/149; 455/114.3
`(58) Field of Search ................................. 375/296,297;
`330/149, 151; 455/114.2, 114.3
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`5,489,879 A * 2/1996 English ...................... 332/103
`
`5,892,397 A * 4/1999 Belcher et al. ............. 330/149
`5,905,760 A 5/1999 Schnablet al. ............. 375/296
`5,949.283 A * 9/1999 Proctor et al. .............. 370/149
`6,111,462 A
`8/2000 Mucenieks et al. ......... 330/149
`6,236,837 B1 * 5/2001 Midya ........................ 330/149
`6,275,685 B1 * 8/2001 Wessel et al. ............... 455/126
`6,449,466 B1
`9/2002 Jin et al. .................... 455/127
`6,600,792 B2 * 7/2003 Antonio et al. ............. 375/297
`
`* cited by examiner
`
`Primary Examiner Mohammad H. Ghayour
`Assistant Examiner Kevin M Burd
`(57)
`ABSTRACT
`
`There is disclosed a pre-distortion adjustment circuit for use
`in an RF transmitter that adjusts the actual adjacent channel
`power (ACP) noise profile of an RF power amplifier to fully
`use the ACP profile allowed under the applicable RF com
`munication Standard. The pre-distortion adjustment circuit
`pre-distorts Selected components of the input Signal to the
`RF power amplifier so that the actual output ACP profile
`appears Similar to, if not the same as, the ACP profile under
`the Standard. The distortion required is determined based on
`information extracted from the input signal, the output
`signal, and the standard ACP profile. The pre-distortion
`adjustment circuit allows significant overdrive of the RF
`power amplifier while maintaining the ACP noise in the RF
`output below the levels allowed under the standard.
`
`20 Claims, 5 Drawing Sheets
`
`O
`ANTENNA
`ARRAY 255
`
`300
`
`
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`INPUT
`DAA
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`
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`305
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`PRE-DISTORTER
`CRC
`
`Prof.
`DATA
`
`355
`S
`PROCESSOR
`
`
`
`SYNC. 8, DATA
`ACCUSITION
`CONTROLLER
`
`SYNC. & DATA
`ACOUSITION
`CONTROLER
`
`SYSTEM
`CLOCK
`
`PETITIONERS EXHIBIT 1004
`Page 1 of 13
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`

`

`U.S. Patent
`
`Feb. 17, 2004
`
`Sheet 1 of 5
`
`US 6,693,974 B2
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`140
`
`M
`
`TO PUBLC
`ELEPHONE
`SYSTEM
`
`
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`PETITIONERS EXHIBIT 1004
`Page 2 of 13
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`

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`U.S. Patent
`
`Feb. 17, 2004
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`Sheet 2 of 5
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`US 6,693,974 B2
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`07||
`SOSW O L
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`TENNY/HO
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`No. TTOM_LNO O S18
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`PETITIONERS EXHIBIT 1004
`Page 3 of 13
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`U.S. Patent
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`Feb. 17, 2004
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`Sheet 3 of 5
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`US 6,693,974 B2
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`PETITIONERS EXHIBIT 1004
`Page 4 of 13
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`PETITIONERS EXHIBIT 1004
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`U.S. Patent
`
`Feb. 17, 2004
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`Sheet 4 of 5
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`US 6,693,974 B2
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`NPUT BASEBAND SIGNAL OR
`BASEBAND OUTPUT SIGNAL
`
`345
`350
`
`
`
`DAA
`PROCESSOR
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`SYSTEM
`COCK
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`ACOURED
`DATA
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`F.G. 4
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`PETITIONERS EXHIBIT 1004
`Page 5 of 13
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`

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`U.S. Patent
`
`Feb. 17, 2004
`
`Sheet 5 of 5
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`US 6,693,974 B2
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`
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`502
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`
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`
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`503
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`RECEIVE AND SAMPLE DIGAL
`BASEBAND INPUT SiGNAL AND MAKE
`PREDISTORTION ADJUSTMENT, F NEEDED
`
`CONVERT ADJUSTED DiGTAL BASEBAND
`SIGNAL TO ANALOG BASEBAND SIGNAL;
`MODUATE ANALOG BASEBAND AND
`AMPLFY IN RF POWER AMPLEFERTO
`GE RF OUTPUT SIGNAL
`
`SAMPLE AND DEMODULATE RF OUTPUT
`SiGNATO GET ANALOG BASEBAND
`OUTPUT SIGNAL CONVERT TO DIGITAL
`BASEBAND OUTPUT SIGNAL
`
`
`
`
`
`504
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`
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`
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`ALIGN, COMPARE AND SCALE DIGITAL
`BASEBAND INPUT SIGNA SAMPLES AND DIGITAL
`BASEBAND OUTPUT SIGNALSAMPLES;
`GENERATE NEW ADJUSTMENT PARAMETERS
`
`PETITIONERS EXHIBIT 1004
`Page 6 of 13
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`

`US 6,693,974 B2
`
`1
`ADAPTIVE DIGITAL PRE-DISTORTION
`CIRCUIT USINGADJACENT CHANNEL
`POWER PROFILE AND METHOD OF
`OPERATION
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`The present application is a related to that disclosed in
`co-pending U.S. patent application Ser. No. 09/224,193 for
`“ADAPTIVE DIGITAL PRE-DISTORTION CORREC
`TION CIRCUIT FOR USE IN A TRANSMITTER IN A
`DIGITAL COMMUNICATION SYSTEMAND METHOD
`OF OPERATION," filed on Dec. 30, 1998. U.S. patent
`application Ser. No. 09/224,193 is hereby incorporated by
`reference in the present disclosure as if fully Set forth herein.
`
`15
`
`TECHNICAL FIELD OF THE INVENTION
`The present invention is directed, in general, to wireleSS
`networks and, more Specifically, to an adaptive digital
`pre-distortion correction circuit for use in an RF transmitter.
`
`2
`generated from a CDMA Signal appear like white noise: the
`power density does not change significantly with frequency.
`However, the ACP profile defined in, for example, the IS95
`CDMA System Standard does not require a constant Spurious
`power density over different frequencies. The whole fre
`quency Spectrum is divided into a few blocks and the
`Standard ACP profile changes significantly from one block to
`the next.
`This may lead to situations in which the power amplifier
`output power level is dictated by the ACP noise at few
`frequency points where the Standard ACP profile appears the
`most Stringent. However, there may still be relatively large
`ACP noise margins at many other frequencies. In a Sense, the
`power amplifier ACP noise is not optimized to make full
`usage of the ACP profile under the applicable standard. The
`exceSS ACP noise margin at most frequencies S not utilized.
`There is therefore a need in the art for improved wireless
`networks that use more efficient RE power amplifiers. In
`particular, there is a need for improved RE power amplifiers
`that can operate more closely to full power in Systems
`having high peak-to-mean digital Signal ratios. More
`particularly, there is a need for RF power controllers that
`make RF power amplifiers more efficient by utilizing the
`available ACP noise margins under the applicable Standard
`ACP profile.
`SUMMARY OF THE INVENTION
`To address the above-discussed deficiencies of the prior
`art, it is a primary object of the present invention to provide
`a pre-distortion adjustment circuit for use in an RF trans
`mitter that optimizes the ACP profile of an RF power
`amplifier to fully use the ACP profile under the applicable
`RF communication Standard. The present invention pre
`distorts the RF signal so that the actual output ACP profile
`appears Similar to, if not the same as, the ACP profile under
`the Standard. The pre-distortion required is determined
`based on information extracted from the input signal, the
`output signal, and the Standard ACP profile. Thus, the
`present invention allows Significant Overdrive of the power
`amplifier while still maintaining its ACP noise under the
`standard ACP profile.
`Accordingly, in an exemplary embodiment of the present
`invention, there is provided, for use in an RF transmitter
`having an RF power amplifier required to transmit an RF
`output signal within Selected limits of an adjacent channel
`power (ACP) profile specified for the RF transmitter, a
`pre-distortion adjustment circuit comprising: 1) input Sam
`pling means, coupled to an input of a transmit path of the RF
`transmitter, capable of capturing input Samples from a
`digital input baseband Signal, the input Samples comprising
`a first input sample of amplitude X; 2) output sampling
`means, coupled to an output of the transmit path, capable of
`capturing output Samples of a digital output baseband Signal
`derived from the RF output signal, wherein a first output
`Sample corresponds to the first input sample, and 3) pro
`cessing means capable of determining from the first input
`Sample and the first output Sample a pre-distortion adjust
`ment value capable of adjusting an amplitude of the digital
`input baseband Signal prior to amplification by the RF power
`amplifier without causing the RF output Signal to exceed the
`selected limits of the ACP profile.
`According to one embodiment of the present invention,
`the specified limits of the ACP profile are stored in a memory
`asSociated with the processing means.
`According to another embodiment of the present
`invention, the Specified limits are specified at discrete fre
`quency points.
`
`25
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`BACKGROUND OF THE INVENTION
`Every wireless network base station has a RF power
`amplifier for transmitting voice and/or data Signals to mobile
`units (i.e., cell phones, portable computers equipped with
`cellular modems, pagers, and the like) and a receiver for
`receiving voice and/or data Signals from the mobile units.
`The design of an RF power amplifier (PA) for digital radio
`systems is controlled by two overriding criteria: 1) The RF
`power amplifier should transmit sufficient RF output power
`to serve the cell site of the base station in which it is
`installed, but should also use the minimum amount of DC
`power in doing So; and 2) The adjacent channel power
`35
`(ACP) noise (distortion) should be under certain limits
`(mask), that are usually defined in a standard (i.e., ACP
`profile).
`In most cases, these two criteria are contradictory. ACP
`noise results from no-linear effects, Such as over-driving the
`40
`power amplifier into its nonlinear region (clipping). Spuri
`ous Spectral components are introduced when a signal peak
`is Sufficiently large to Saturate an RF amplifier in the
`transmitter. In order to meet the ACP profile, the RF trans
`mitters in wireleSS networks in which digital Signals have
`high peak-to-mean ratios, Such as CDMA and multi-carrier
`systems, are frequently “backed off” from full power (or
`peak power) to avoid operating the transmitter in non-linear
`conditions. In these digital Systems that have high peak-to
`mean Signal ratios, the RF power amplifier thus needs a
`considerable amount of power "headroom' to accommodate
`the peak power. For example, RF power amplifiers in Some
`CDMA systems need more than 10 dB of headroom space to
`protect the peak CDMA signal power from clipping.
`Unfortunately, leaving this much overhead significantly
`reduces the power efficiency of the RF power amplifier. This
`increases the DC power consumption, the base transceiver
`Station cooling requirements, the overall System Volume,
`weight, and cost.
`For a particular digital radio System, Such as cellular
`CDMA or TDMA, the transmitter ACP profile is defined in
`the System Standard. Generally Speaking, the actual ACP
`profile of an RF power amplifier is not the same as the ACP
`profile required by the standard. The power amplifier ACP
`profile is determined more or less by the power amplifier
`65
`device characteristics, operating modes, and Signal behav
`iors. For example, the out-of-band Spurious components
`
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`PETITIONERS EXHIBIT 1004
`Page 7 of 13
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`US 6,693,974 B2
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`3
`According to Still another embodiment of the present
`invention, the processing means applies the pre-distortion
`adjustment value to a Subsequently received input Sample of
`amplitude X.
`According to yet another embodiment of the present
`invention, the processing means is capable of determining if
`the amplitude X is Sufficiently Small to ensure that an
`amplification distortion caused by the RF power amplifier is
`negligibly Small and, in response to the determination, is
`capable of determining a Scaling factor for the output
`Samples.
`According to a further embodiment of the present
`invention, the processing means Scales Subsequently
`received input Samples of the digital input baseband Signal
`according to a value of the Scaling factor.
`According to a Still further embodiment of the present
`invention, the processing means adjusting an amplitude of
`the Scaled digital input baseband Signal.
`According to a yet further embodiment of the present
`invention, the processing means modifies a Selected Subse
`quently received input Sample according to a value of the
`Scaling factor without regard to an amplitude of the Selected
`Subsequently received input Sample.
`The foregoing has outlined rather broadly the features and
`technical advantages of the present invention So that those
`skilled in the art may better understand the detailed descrip
`tion of the invention that follows. Additional features and
`advantages of the invention will be described hereinafter
`that form the subject of the claims of the invention. Those
`skilled in the art should appreciate that they may readily use
`the conception and the Specific embodiment disclosed as a
`basis for modifying or designing other structures for carry
`ing out the Same purposes of the present invention. Those
`skilled in the art should also realize that Such equivalent
`constructions do not depart from the Spirit and Scope of the
`invention in its broadest form.
`Before undertaking the DETAILED DESCRIPTION, 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 term “controller” means
`any device, System or part thereof that controls at least one
`operation, Such a device 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 controller 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 defini
`tions apply to prior, as well as future uses of Such defined
`words and phrases.
`BRIEF DESCRIPTION OF THE DRAWINGS
`For a more complete understanding of the present
`invention, and the advantages thereof, reference is now
`made to the following descriptions taken in conjunction with
`the accompanying drawings, wherein like numbers desig
`nate like objects, and in which:
`
`1O
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`4
`FIG. 1 illustrates an exemplary wireleSS network accord
`ing to one embodiment of the present invention;
`FIG. 2 illustrates in greater detail an exemplary base
`Station in accordance with one embodiment of the present
`invention;
`FIG. 3 illustrates an exemplary RF transmitter for use in
`the RF transceiver unit in FIG. 2 in accordance with one
`embodiment of the present invention;
`FIG. 4 illustrates exemplary input and output Synchroni
`Zation and data acquisition controllers in accordance with
`one embodiment of the present invention; and
`FIG. 5 is a flow diagram illustrating the operation of the
`exemplary RF transmitter in accordance with one embodi
`ment of the present invention.
`
`DETAILED DESCRIPTION
`FIGS. 1 through 5, discussed below, and the various
`embodiments used to describe the principles of the present
`invention in this patent document are by way of illustration
`only and should not be construed in any way to limit the
`scope of the invention. Those skilled in the art will under
`Stand that the principles of the present invention may be
`implemented in any Suitably arranged wireleSS network.
`FIG. 1 illustrates exemplary wireless network 100 accord
`ing to one embodiment of the present invention. The wire
`less telephone network 100 comprises a plurality of cell sites
`121-123, each containing one of the base stations, BS 101,
`BS 102, or BS 103. Base stations 101-103 are operable to
`communicate with a plurality of mobile stations (MS)
`111-114. Mobile stations 111-114 may be any suitable
`cellular devices, including conventional cellular telephones,
`PCS handset devices, portable computers, metering devices,
`and the like.
`Dotted lines show the approximate boundaries of the cells
`sites 121-123 in which base stations 101-103 are located.
`The cell Sites are shown approximately circular for the
`purposes of illustration and explanation only. It should be
`clearly understood that the cell Sites may have other irregu
`lar shapes, depending on the cell configuration Selected and
`natural and man-made obstructions.
`In one embodiment of the present invention, BS 101, BS
`102, and BS 103 may comprise a base station controller
`(BSC) and a base transceiver station (BTS). Base station
`controllers and base transceiver Stations are well known to
`those skilled in the art. A base Station controller is a device
`that manages wireleSS communications resources, including
`the base transceiver Station, for Specified cells within a
`wireleSS communications network. A base transceiver Sta
`tion comprises the RF transceivers, antennas, and other
`electrical equipment located in each cell Site. This equip
`ment may include air conditioning units, heating units,
`electrical Supplies, telephone line interfaces, and RF trans
`mitters and RF receivers. For the purpose of simplicity and
`clarity in explaining the operation of the present invention,
`the base transceiverstation in each of cells 121, 122, and 123
`and the base Station controller associated with each base
`transceiver station are collectively represented by BS 101,
`BS 102 and BS 103, respectively.
`BS 101, BS 102 and BS 103 transfer voice and data
`Signals between each other and the public telephone System
`(not shown) via communications line 131 and mobile
`switching center (MSC) 140. Mobile switching center 140 is
`well known to those skilled in the art. Mobile Switching
`center 140 is a Switching device that provides Services and
`coordination between the Subscribers in a wireleSS network
`
`PETITIONERS EXHIBIT 1004
`Page 8 of 13
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`US 6,693,974 B2
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`and external networks, Such as the public telephone System.
`Communications line 131 may be any Suitable connection
`means, including a T1 line, a T3 line, a fiber optic link, a
`network backbone connection, and the like. In Some
`embodiments of the present invention, communications line
`131 may be several different data links, where each data link
`couples one of BS 101, BS 102, or BS 103 to MSC 140.
`In the exemplary wireless network 100, MS 111 is located
`in cell site 121 and is in communication with BS 101, MS
`113 is located in cell site 122 and is in communication with
`BS 102, and MS 114 is located in cell site 123 and is in
`communication with BS 103. The MS 112 is also located in
`cell site 121, close to the edge of cell site 123. The direction
`arrow proximate MS 112 indicates the movement of MS 112
`towards cell site 123. At some point, as MS 112 moves into
`cell site 123 and out of cell site 121, a “handoff will occur.
`As is well know, the “handoff procedure transfers control
`of a call from a first cell to a second cell. For example, if MS
`112 is in communication with BS 101 and senses that the
`signal from BS 101 is becoming unacceptably weak, MS 112
`may then Switch to a BS that has a stronger Signal, Such as
`the signal transmitted by BS 103. MS 112 and BS 103
`establish a new communication link and a signal is Sent to
`BS 101 and the public telephone network to transfer the
`on-going voice, data, or control Signals through BS 103. The
`call is thereby seamlessly transferred from BS 101 to BS
`103. An "idle' handoff is a handoff between cells of a mobile
`device that is communicating in the control or paging
`channel, rather than transmitting voice and/or data Signals in
`the regular traffic channels.
`FIG. 2 illustrates in greater detail exemplary base Station
`101 in accordance with one embodiment of the present
`invention. Base station 101 comprises base station controller
`(BSC) 210 and base transceiver station (BTS) 220. Base
`Station controllers and base transceiver Stations were
`described previously in connection with FIG. 1. BSC 210
`manages the resources in cell site 121, including BTS 220.
`BTS 120 comprises BTS controller 225, channel controller
`235, which contains one or more representative channel
`elements 240, transceiver interface (IF) 245, RF transceiver
`unit 250, antenna array 255, and channel monitor 260.
`BTS controller 225 comprises processing circuitry and
`memory capable of executing an operating program that
`controls the overall operation of BTS 220 and communicates
`with BSC 210. Under normal conditions, BTS controller 225
`directs the operation of channel controller 235, which con
`tains a number of channel elements, including channel
`element 240, that perform bi-directional communications in
`the forward channel and the reverse channel. A "forward”
`channel refers to outbound Signals from the base Station to
`the mobile station and a “reverse' channel refers to inbound
`Signals from the mobile Station to the base Station. Trans
`ceiver IF 245 transfers the bi-directional channel signals
`between channel controller 240 and RF transceiver unit 250.
`Antenna array 255 transmits forward channel Signals
`received from RF transceiver unit 250 to mobile stations in
`the coverage area of BS 101. Antenna array 255 also sends
`to transceiver 250 reverse channel signals received from
`mobile stations in the coverage area of BS 101. In a
`preferred embodiment of the present invention, antenna
`array 255 is multi-Sector antenna, Such as a three Sector
`antenna in which each antenna Sector is responsible for
`transmitting and receiving in a 120 arc of coverage area.
`Additionally, transceiver 250 may contain an antenna Selec
`tion unit to Select among different antennas in antenna array
`255 during both transmit and receive operations. In one
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`6
`embodiment of the present invention, antenna array 255 may
`comprise an adaptive antenna array or “Smart' antenna
`array.
`To increase the efficiency of the RF transmitters in RF
`transceiver 250, the present invention implements an adap
`tive digital pre-distorter (ADPD) circuit that samples the RF
`transmitter input and output Signals, and Synchronizes and
`compares the Samples to each other and to the ACP profile
`of an applicable Standard. The present invention then deter
`mines the pre-distortion adjustment required to overdrive the
`power amplifier, while maintaining ACP noise below the
`ACP profile of the standard. The pre-distortion adjustment is
`then added to Subsequent input Samples. The present inven
`tion may be implemented in any type of digital modulation
`scheme, including TDMA, CDMA, GSM, NCDMA, multi
`carrier Signals, and even modems.
`FIG.3 illustrates exemplary RF transmitter 300 for use in
`RF transceiver unit 250 in accordance with one embodiment
`of the present invention. RF transmitter 300 contains a
`transmit path that receives input data and generates an RF
`output signal that is Sent to antenna array 255. The transmit
`path elements in RF transmitter 300 comprise pre-distorter
`circuit 305, digital-to-analog converter (DAC) 310, RF
`modulator 315, local oscillator 320, RF power amplifier
`(PA) 325, and RF coupler (RFC) 330.
`RF transmitter 300 also contains a pre-distortion adjust
`ment feedback loop that Samples the input data Signal and a
`corresponding part of the RF Output signal, compares the
`Samples to each other and to the accepted ACP profile, and
`generates a pre-distortion adjustment Signal that is added to
`Subsequent Samples of the input signal data. The pre
`distortion correction feedback loop elements in RF trans
`mitter 300 comprise RF demodulator 335, local oscillator
`320, analog-to-digital converter (ADC) 340, input synchro
`nization and data acquisition controller 345, output Synchro
`nization and data acquisition controller 350, processor 355,
`and memory 360, which stores ACP profile data 365. The
`ACP profile data 365 varies according to the communica
`tions standard to which wireless network 101 must conform.
`For example, the ACP profile data 365 may comprise the
`ACP noise limitations (ACP “mask') under the IS95 CDMA
`System Standard.
`A digital baseband signal, referred to as “INPUT DATA'
`in FIG. 3, is received by pre-distorter circuit 305, which may
`optionally add a pre-distortion error correction retrieved
`from LUT 306 before sending the INPUT DATA signal to
`DAC 310. DAC 310 converts the digital signal to an analog
`signal that forms the baseband input to RF modulator 315.
`The other input to RF modulator is a reference RF carrier
`signal from local oscillator 320. The output of RF modulator
`315 is an RF signal modulated by the baseband signal. Next,
`the modulated RF signal is amplified by RF power amplifier
`325 to a power level suitable for transmission. The amplified
`modulated RF output signal is then sent to antenna array 255
`via RFC 330.
`Those skilled in the art will recognize that the above
`described modulation and amplification Steps are common
`operations in conventional RF transmitters. If the amplitude
`of the INPUT DATA signal is relatively low, RF power
`amplifier 325 operates well within the linear region and little
`or no distortion is introduced in the RF Output signal Sent to
`antenna array 255. However, when operating in the linear
`region, RF power amplifier 325 is very inefficient in terms
`of power consumption.
`As the amplitude of the INPUT DATA signal rises, RF
`power amplifier 325 begins to Saturate (i.e., operates in a
`
`PETITIONERS EXHIBIT 1004
`Page 9 of 13
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`

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`25
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`7
`non-linear manner) and distortion is introduced in the RF
`output Signal Sent to antenna array 255. This distortion
`includes adjacent channel power (ACP) noise that must be
`limited, at the frequencies of interest, to an amount less than
`the ACP profile (i.e., “mask') specified in the applicable
`System Standard.
`The pre-distortion adjustment signal is determined by the
`operation of input Synchronization and data acquisition
`controller 345, output Synchronization and data acquisition
`controller 350 and processor 355. RFC 330 sends a copy of
`the RF output signal to RF demodulator 335. The other input
`to RF demodulator 335 is the same carrier reference signal
`from local oscillator 320 that was used by RF modulator 315
`to produce the original RF modulated Signal. The output of
`RF demodulator 335 is a scaled version of the original
`analog baseband Signal generated by DAC 310, plus pos
`Sible distortion components. The Scaled, distorted analog
`baseband is converted by ADC 340 to digital values that are
`read by output Synchronization and data acquisition control
`er 350.
`FIG. 4 illustrates exemplary input Synchronization and
`data acquisition controller (ISDAC) 345 and output syn
`chronization and data acquisition controller (OSDAC) 350
`in accordance with one embodiment of the present inven
`tion. The operations of ISDAC 345 and OSDAC 350 are
`quite Similar, as explained below in greater detail.
`ISDAC 345 comprises data processor 401, interface (I/F)
`and control circuit 402, and RAM 403. A system clock
`provides a reference for clocking the input digital baseband
`signal (i.e., INPUT DATA) into data processor 401 and
`clocking the acquired data out of interface and control
`circuit 402. The INPUT DATA signal samples are stored in
`RAM 403. Data processor 401 comprises a signal correlator
`that analyzes the bits in the INPUT DATA signal to deter
`mine the start and stop of N-bit data samples, where “N” is
`a known System parameter that varies depending on the type
`of system wireless network 100 is (i.e., CDMA, GSM,
`TDMA, WCDMA, etc.). The N-bit samples begin with a
`recognizable marker that denotes the start of the N-bit
`sample. When an entire N-bit sample has been detected and
`captured (acquired), data processor 401 sends a signal to
`interface and control circuit 402 which transfers the acquired
`data to processor 355.
`Similarly, OSDAC 350 comprises data processor 401,
`45
`interface (I/F) and control circuit 402, and RAM 403. A
`System clock provides a reference for clocking the distorted
`output digital baseband Signal into data processor 401 and
`clocking the acquired data out of interface and control
`circuit 402. The output digital baseband Signal Samples are
`stored in RAM 403. Data processor 401 comprises a signal
`correlator that analyzes the bits in the distorted output digital
`baseband signal to determine the start and stop of the N-bit
`data samples. The N-bit samples are the same N-bit samples
`that are contained in the INPUT DATA signal. Even though
`the output digital baseband Signal may be distorted, enough
`of the bits remain unchanged to enable the Signal correlator
`in data processor 401 to recognize the marker that denotes
`the start of the N-bit sample. When an entire N-bit sample
`has been detected and captured (acquired), data processor
`401 sends a signal to interface and control circuit 402 which
`transfers the acquired data to processor 355.
`Processor 355 comprises comparison circuitry for com
`paring the acquired data received from ISDAC 345 and
`OSDAC 350 with each other and with ACP profile data 365
`stored in memory 360 and for calculating a pre-distortion
`adjustment value that is used by pre-distorter circuit 305.
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`ACP profile data 365 specifies the required ACP mask at a
`Set of discrete frequency points, A(Z). Its time domain
`counterpart, {a,(n), n=1,2,3,...}, can be obtained by using
`a fast Fourier transform (FFT):
`Equation 1:
`a(n)=FFT'(A(z)).
`Pre-distorter circuit 305 comprises a series combination
`of: 1) a nonlinear distorter, and 2) a post digital filter. The
`nonlinear distorter is characterized by its transfer function
`f(. . . ). If INPUT DATA samples are defined as a(n),
`n=1,2,3,... }, then f(. . . ) is defined by the nonlinear
`output-input relationship:
`
`Equation 2:
`a (n)=f(ao(n)); n=1,2,3,. . .
`The transfer function f (...) of the nonlinear distorter
`can be written in a generic function form that contains
`adjustable parameters {di}, i=1,2,3, .
`.
`. . The transfer
`function f(. . . ) is then denoted as f{di}. The Z-domain,
`A (Z), of a(n) is given by:
`Equation 3:
`A, (z)=FFT(a(n))
`The output of the non-linear distorter is received by the
`post digital filter portion of pre-distorter circuit 305, and is
`characterized by its transfer function F. The output A(Z) of
`the post digital filter is related to the input A (Z) received
`from the non-linear distorter by:
`Equation 4:
`A2(z)=A(z):F(z)
`F(. . . ) can be written in a generic function form with
`adjustable parameters {fi}, i=1,2,3,..., denoted as Ffi}.
`By using an inverse FFT, the output of the post digital
`filter (and pre-distorter circuit 305) is given by:
`Equation 5:
`a (n)=FFT'(A2(z))
`The output, a(n), of pre-distorter circuit 305 is received
`by RF power amplifier 325 (after conversion in DAC 310
`and modulation in RF modulator 315). RF power amplifier
`325 can be modeled as a nonlinear device and characterized
`by a nonlinear function, f, as follows:
`Equation 6:
`a(n)=f(a(n)); n=1,2,3,...
`The value a is the output signal of RF power amplifier
`325 and the value a is its input Signal. The nonlinear
`function, f, can be written in a generic function form that
`contains a set of adjustable parameters {p}, i=1,2,3, . . . .
`Function f is then denoted as f{p}. The parameter {p} can
`be obtained from the measured input signal ao(n) and output
`signal a(n) using Equations 3 through Equation 6 if the
`parameters {d} of the distorter and {f} of the post digital
`filter are given.
`Equation 6 can also be written in its inverse form:
`Equation 7:
`where f(. . . ) is the inverse function of f(. . . ).
`The data processing procedure used to determine the
`distortion adjustment parameter may be Summarized as
`follows:
`1) For given input data, ao(n), and given output data,
`a(n), processor 355 calculates the Scaling value, k.
`ASSuming Signals w