IPR2021-00990
`U.S. Patent No. 7,110,444
`Patent Owner’s Response
`
`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`____________________________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`____________________________
`
`TCL Industries Holdings Co., Ltd. and Hisense Co., Ltd.,
`
`Petitioners
`
`v.
`
`ParkerVision, Inc.
`
`Patent Owner
`
`U.S. Patent No. 7,110,444
`
`Issue Date: September 19, 2006
`Title: WIRELESS LOCAL AREA NETWORK
`(WLAN) USING UNIVERSAL FREQUENCY
`TRANSLATION TECHNOLOGY INCLUDING
`MULTI-PHASE EMBODIMENTS AND
`CIRCUIT IMPLEMENTATIONS
`__________________________________________________________________
`
`Inter Partes Review No. IPR2021-00990
`
`__________________________________________________________________
`
`DECLARATION OF DR. MICHAEL STEER
`
`

`

`Table of Contents
`
`Page
`
`BACKGROUND .......................................................................................... 1
`I.
`PROFESSIONAL QUALIFICATIONS ........................................................ 1
`II.
`III. MATERIAL CONSIDERED ........................................................................ 3
`IV. LEGAL STANDARDS ................................................................................ 5
`A. Obviousness. ....................................................................................... 5
`B.
`“Means-plus-function” claim elements. .............................................. 7
`LEVEL OF ORDINARY SKILL IN THE ART ........................................... 8
`V.
`VI. GENERAL OVERVIEW OF THE TECHONOLOGY ................................. 9
`A. Wired communications. ...................................................................... 9
`B. Wireless communications. ................................................................ 10
`C.
`Frequency. ........................................................................................ 11
`D. Up-conversion. ................................................................................. 12
`E.
`Down-conversion. ............................................................................. 13
`VII. DETAILED TECHNOLOGY BACKGROUND ........................................ 13
`A.
`Radio frequency. ............................................................................... 13
`B.
`Basic circuit concepts. ...................................................................... 16
`C.
`Integrated circuits. ............................................................................ 20
`D.
`Circuit diagrams................................................................................ 23
`E.
`Circuit components. .......................................................................... 24
`1.
`Transistors .............................................................................. 24
`2.
`Capacitor. ............................................................................... 25
`
`i
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`

`

`F.
`G.
`
`Resistor. .................................................................................. 28
`3.
`Differential amplifier. ............................................................. 29
`4.
`Electrical load, high impedance loads and low impedance loads. ...... 30
`Signals; time domain and frequency domain representations of a
`signal. ............................................................................................... 31
`Baseband signals, carrier signals, modulation and up-conversion. .... 34
`H.
`I/Q Modulation. ................................................................................ 36
`I.
`Demodulation. .................................................................................. 38
`J.
`Transceiver. ...................................................................................... 38
`K.
`Direct conversion and intermediate frequencies. ............................... 40
`L.
`M. History of RF receivers. .................................................................... 42
`1.
`Heterodyne receivers. ............................................................. 43
`2. Mixers..................................................................................... 45
`3.
`Sample-and-hold (a type of voltage sampling). ....................... 49
`4.
`Energy Sampling. ................................................................... 56
`VIII. ENERGY SAMPLING V. VOLTAGE SAMPLING .................................. 63
`IX. U.S. PATENT NO. 7,110,444 ..................................................................... 64
`A. Overview .......................................................................................... 64
`B.
`The patent discloses two fundamental different and competing
`systems for down-conversion. ........................................................... 72
`1.
`Energy transfer (energy sampling). ......................................... 74
`2.
`Sample-and-hold (a type of voltage sampling). ....................... 79
`Prosecution history of the ’444 patent. .............................................. 83
`C.
`CLAIM CONSTRUCTION ........................................................................ 86
`
`X.
`
`ii
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`

`

`“storage element” (claim 3) .............................................................. 86
`A.
`“[a] wireless modem apparatus”........................................................ 87
`B.
`“frequency down-conversion module” (claim 3) ............................... 88
`C.
`“subtractor module” (claim 3) ........................................................... 89
`D.
`XI. SECONDARY CONSIDERATIONS ......................................................... 89
`A.
`Long-felt need. .................................................................................. 89
`B.
`Others tried and failed. ...................................................................... 90
`C.
`Unexpected results. ........................................................................... 91
`D.
`Praise by others. ................................................................................ 94
`E.
`Copying and commercial success. ..................................................... 94
`XII. CITED REFERENCES ............................................................................... 95
`A. U.S. Patent No. 6,230,000 to Tayloe (“Tayloe”). .............................. 95
`B.
`Texas Instruments Datasheet for SN74CBT3253 DUAL 1-OF-4 FET
`MULTIPLEXER/DEMULTIPLEXER (“TI Datasheet”) ................ 113
`U.S. Patent No. 5, 937, 013 to Lam et al. (“Lam”) .......................... 113
`Circuit Techniques for Reducing the Effects of Op-Amp
`Imperfections: Autozeroing, Correlated Double Sampling, and
`Chopper Stabilization, Proceedings of the IEEE, Vol.84, No.11,
`November 1996 (“Enz”) ................................................................. 117
`XIII. VALIDITY OF THE ’444 PATENT ........................................................ 119
`A. GROUND 1: Claims 2-3 – Tayloe in View of the TI Datasheet. ..... 119
`B.
`Tayloe Capacitors Hold Negligible Amounts of Energy ................. 119
`1.
`Energy in a Tayloe Capacitor. ............................................... 123
`a)
`STEP 1: Calculating available energy. ........................ 123
`b)
`STEP 2: Calculating energy in capacitor. .................... 127
`
`C.
`D.
`
`iii
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`

`

`2.
`
`C.
`D.
`E.
`F.
`
`STEP 3: Percentage of available energy. ..................... 128
`c)
`Energy in ParkerVision’s storage element............................. 129
`a)
`STEP 1: Calculating available energy. ........................ 129
`b)
`STEP 2: Energy stored on storage element. ................ 130
`c)
`STEP 3: Percentage of available energy. ..................... 131
`Tayloe capacitors are not elements of an energy transfer system..... 131
`Tayloe does not disclose a “wireless modem apparatus.” ................ 136
`TI Datasheet does not cure deficiencies of Tayloe .......................... 139
`GROUND 2: Claim 2, 3 and 4 – Lam in View of Enz and Tayloe .. 139
`1.
`Lam and Enz Capacitors Hold Negligible Amounts Of Energy.
`.............................................................................................. 140
`Lam/Enz capacitors are not elements of an energy transfer
`system. .................................................................................. 141
`Enz does not disclose a first/second “frequency down-
`conversion module to down-convert [the/said] input signal.” 142
`Lam does not disclose a “wireless modem apparatus”. ......... 144
`4.
`Claim 4 is not obvious in view of Lam/Enz. ......................... 144
`5.
`There is no motivation to combine Lam and Enz. ................. 145
`6.
`XIV. SUPPLEMENTATION ............................................................................ 147
`
`
`2.
`
`3.
`
`
`
`iv
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`

`

`I have personal knowledge of the facts set forth in this declaration and, if
`
`called to testify as a witness, would testify under oath as follows:
`
`I.
`
`BACKGROUND
`I have been retained as an expert on behalf of ParkerVision, Inc.
`1.
`
`(“ParkerVision”) in the above-captioned matter (IPR2021-00990).
`
`2.
`
`I have been asked by ParkerVision to provide my expert opinion
`
`regarding the validity of claims 2-4 of U.S. Patent No. 7,110,444 (“the ’444 patent”).
`
`For the reasons set forth below, it is my opinion that claims 2-4 of the ’444 patent
`
`are valid.
`
`II.
`
`PROFESSIONAL QUALIFICATIONS
`I am currently the Lampe Distinguished Professor Emeritus of
`3.
`
`Electrical and Computer Engineering at North Carolina State University.
`
`4.
`
`I received my Bachelor of Engineering with Honors (B.E. Hons) and
`
`Ph.D. in Electrical Engineering from the University of Queensland, Brisbane,
`
`Australia, in 1976 and 1983 respectively.
`
`5.
`
`I was a pioneer in the modeling and simulation of nonlinear radio
`
`frequency and microwave circuits. To put this in perspective, the first commercial
`
`cellular phone became available in 1983, and in that same year, I began teaching
`
`classes in radio frequency circuit design. Specifically, I joined the Electrical
`
`Engineering Department at North Carolina State University, Raleigh, North
`
`1
`
`

`

`Carolina, as a Visiting Assistant Professor in August 1983. I became an Assistant
`
`Professor in 1986 when the department was renamed the Department of Electrical
`
`and Computer Engineering. I have been promoted throughout the years, first
`
`becoming an Associate Professor in 1991, a Professor in 1996, a Named Professor
`
`in 2005, and a Distinguished Professor in 2010. I retired in June 2021 and was
`
`appointed as Lampe Distinguished Professor Emeritus in July 2021.
`
`6.
`
`During the 1990s, I began working very closely with the U.S.
`
`Department of Defense, and in particular with the U.S. Army, on radio frequency
`
`communications and advanced radio frequency circuits. Between 1996 and 1998, I
`
`also worked as a consultant for Zeevo, Inc., a Silicon Valley-based provider of
`
`semiconductor and software solutions for wireless communications.
`
`7.
`
`In 1999, I moved to the United Kingdom to become Professor and
`
`Director of the Institute of Microwaves and Photonics at the University of Leeds,
`
`one of the largest university-based academic radio frequency research groups in
`
`Europe. I held the Chair in Microwave and Millimetrewave Electronics. I also
`
`continued my work with the U.S. Army and worked with the European Office of the
`
`U.S. Army Research Office. I returned to the United States in 2000, resuming the
`
`position of Professor of Electrical and Computer Engineering at North Carolina State
`
`University.
`
`2
`
`

`

`8.
`
`Further details on various aspects of my professional experience and
`
`qualifications can be found in my curriculum vitae, which is attached hereto as
`
`Appendix A.
`
`9.
`
`Based on my experience in the wireless communications industry, I
`
`have a detailed understanding of radio frequency circuit design, including the radio
`
`frequency front end of cellular phones.
`
`III. MATERIAL CONSIDERED
`In preparing this declaration, I have reviewed the specification, claims
`10.
`
`and prosecution history of the ’444 patent.
`
`11.
`
`I understand that the ’444 patent (a) issued on Sept. 19, 2006, (b) is a
`
`continuation-in-part of application No. 09/525,615 (now U.S. Patent No. 6,853,690),
`
`filed on Mar. 14, 2000, (c) is a continuation-in-part of application No. 09/526,041
`
`(now U.S. Patent No. 6,879,817), filed on Mar. 14, 2000, and (d) claims priority to
`
`provisional application No. 60/147,129, filed on Aug. 4, 1999.
`
`12.
`
`I have reviewed and understand the following documents.
`
`1001
`1002
`
`Exhibit Description
`
`Petition for Inter Partes Review of U.S. Patent No. 7,110,444
`Challenging Claims 2-4 (“Petition”)
`U.S. Patent No. 7,110,444 (“the ’444 patent”)
`Declaration of Dr. Matthew B. Shoemake Regarding U.S. Patent No.
`7,110,444
`’444 patent File History
`U.S. Patent No. 6,230,000 (“Tayloe”)
`SN74CBT3253D Dual 1-of-4 FET Multiplexer/Demultiplexer (rev. ed.
`May 1998) (“TI Datasheet”)
`
`1003
`1004
`1005
`
`3
`
`

`

`1006
`1007
`
`1008
`
`1014
`1015
`2016
`
`2017
`
`2018
`
`2019
`
`2020
`
`2021
`
`2022
`2023
`2024
`2025
`2026
`
`2027
`
`2028
`
`2029
`2030
`
`2031
`2032
`2033
`2034
`
`U.S. Patent No. 5,937,013 (“Lam”)
`Circuit Techniques for Reducing the Effects of Op-Amp Imperfections:
`Autozeroing, Correlated Double Sampling, and Chopper Stabilization,
`Proceedings of the IEEE, Vol.84, No.11, November 1996 (“Enz”)
`Haque et al, A Two Chip PCM Voice CODEC With Filters, IEEE
`Journal of Solid-State Circuits, Vol. 4, SC-14, No. 6, Dec. 1979
`(“Haque”)
`U.S. Patent No. 5,764,693 (“Taylor”)
`U.S. Patent No. 5,742,641 (“Dingsor”)
`Final Written Decision, Intel Corp. v. ParkerVision, Inc., IPR2020-
`01265 (Jan. 21, 2022)
`Claim Construction Order, ParkerVision, Inc. v. Intel Corp., No. 6:20-
`cv-00108-ADA (W.D. Tex.)
`Claim Construction Order, ParkerVision, Inc. v. Intel Corp., No. 6:20-
`cv-00562-ADA (W.D. Tex.)
`Amended Claim Construction Order, ParkerVision, Inc. v. Intel Corp.,
`No. 6:20-cv-00562-ADA (W.D. Tex.)
`Special Master’s Recommended Claim Constructions, ParkerVision,
`Inc. v. Hisense Co., Ltd. et al., No. 6:20-cv-00870-ADA (W.D. Tex.)
`Special Master’s Recommended Claim Constructions, ParkerVision,
`Inc. v. TCL Industries Holdings Co., No. 6:20-cv-00945-ADA
`“Transistor,” The American Heritage College Dictionary (3rd ed. 1997)
`Donald Christiansen, Electronics Engineers’ Handbook (4th ed. 1996)
`Richard C. Jaeger, Microelectronic Circuit Design (1997)
`Rudolf Graf, Modern Dictionary of Electronics (7th ed. 1999)
`J. Crols, “A 1.5 GHz Highly Linear CMOS Downconversion Mixer,
`IEEE J. Solid-State Circuits, Vol. 30, No.7, pp. 736-742, July 1995
`A. Rofougaran, J. Chang, M. Rofougaran, and A. Abidi, “A 1 GHz
`CMOS RF Front-End IC for a Direct-Conversion Wireless Receiver,”
`IEEE J. Solid-State Circuits, Vol. 31, No. 7, pp. 880-889, July 1996
`B. Razavi, “Challenges in Portable RF Transceiver Design,” IEEE
`Circuits and Devices, Vol. 12, No. 5, pp. 12-25, Sept. 1996
`U.S. Patent No. 6,061,551
`B. Razavi, “CMOS RF receiver design for wireless LAN applications,”
`IEEE Radio and Wireless Conference, pp. 275-280, Aug. 1999
`Qualcomm Email dated Aug. 11, 1998
`Qualcomm Email dated Feb. 2, 1999
`Qualcomm Email dated Oct. 7, 1998
`Qualcomm Email dated Feb. 4, 1999
`
`4
`
`

`

`2035
`2036
`
`2037
`
`2039
`
`Thomas L. Floyd, Principles of Electric Circuits (5th ed. 1997)
`Martin Hartley Jones, A practical introduction to electronic circuits (3rd
`ed. 1995)
`“General Purpose Single
`SGS-THOMSON Microelectronics,
`Operational Amplifier UA741” (October 1997)
`Kevin McClaning, Wireless Receiver Design
`Communications (SciTech Publishing 2012)
`
`for Digital
`
`
`IV. LEGAL STANDARDS
`I am not an attorney and I have not independently researched the law.
`13.
`
`ParkerVision’s counsel has explained certain legal principles to me that I have relied
`
`on in forming my opinions set forth in this declaration. I have applied these legal
`
`principles in arriving at my opinions expressed in this declaration.
`
`A. Obviousness.
`I have been informed and understand that an invention cannot be
`14.
`
`patented if the subject matter as a whole would have been obvious to a person of
`
`ordinary skill in the art at the time of the invention. Also, I understand that while the
`
`prior art is compared to each claim on an element-by-element basis, the claimed
`
`invention as a whole must have been obvious to one of ordinary skill in order for a
`
`claim to be invalid.
`
`15.
`
`I understand that the fundamental question in analyzing obviousness is
`
`whether, at the time of the invention, the subject matter of the claimed invention as
`
`a whole would have been obvious to a person of ordinary skill in the art to which the
`
`subject matter pertains, taking into account: (a) the scope and content of the prior
`
`5
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`

`art; (b) the differences between the prior art and the claims at issue; (c) the level of
`
`ordinary skill in the art; and (d) any objective indicia of non-obviousness referred to
`
`as secondary considerations.
`
`16.
`
`It is my understanding that objective indicia of non-obviousness
`
`(secondary considerations) include industry praise, commercial success, long-felt
`
`but unresolved need, copying, failure of others, and/or unexpected results. I also
`
`understand that there should be a nexus between the objective indicia and the
`
`claimed invention.
`
`17.
`
`I understand that multiple references can be combined, with one another
`
`and/or with the knowledge of a person of ordinary skill in the art, in rendering a
`
`claim obvious. I also understand, however, that obviousness cannot be established
`
`by simply demonstrating that each element was independently known in the prior
`
`art. Rather, it may be necessary to identify a reason, such as a teaching, suggestion,
`
`or motivation, that would have prompted a person of ordinary skill in the art to
`
`combine the elements in the way the claimed invention does.
`
`18.
`
`I also understand that obviousness cannot be established through
`
`hindsight. I understand this to mean that the claimed invention cannot be used as a
`
`roadmap to combine elements from different pieces of prior art, or different
`
`embodiments of a single prior art reference, to create the claimed invention. I
`
`understand that the claimed invention as a whole must be compared to the prior art
`
`6
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`

`

`as a whole, and one must avoid aggregating pieces of prior art through hindsight that
`
`would not have been combined absent the patent inventor’s insight.
`
`B.
`19.
`
`“Means-plus-function” claim elements.
`I have been informed and understand that a claim term using the word
`
`“means” is presumed to be a “means-plus-function” term. I also have been informed
`
`that a term used as a substitute for “means” (referred to as a “nonce” word) (e.g., the
`
`term “element” or “module” used by itself) that fails to connote structure (from the
`
`point of view of a person of ordinary skill in the art at the time of the invention) to
`
`perform the claimed function(s) is also a means-plus-function term.
`
`20.
`
`I understand that a means-plus-function term is limited to the function
`
`recited in the claim and the specific structure disclosed in the patent’s specification
`
`for performing that function and structures that are equivalent to the disclosed
`
`structures. As such, it is my understanding that if a term is a means-plus-function
`
`term, the term is defined by its function (as set forth in the claim) and the specific
`
`structure disclosed in the patent’s specification for performing that function and
`
`structures that are equivalent to the disclosed structures.
`
`21.
`
`I also understand that a claim term that does not use the word “means”
`
`is presumed not to be a “means-plus-function” term. I understand that in order for a
`
`term that does not use the word “means” to be deemed a “means-plus-function” term,
`
`the term must not connote structure to a person of ordinary skill in the art at the time
`
`7
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`

`of the invention. In other words, if the term connotes structure, it is not deemed to
`
`be a “mean-plus-function” term.
`
`22.
`
`I have been informed and understand that for a means-plus-function
`
`term, a prior art reference or combination of references must disclose the identical
`
`function set forth in the claim and must disclose a structure that performs the
`
`function that is either identical to or the equivalent of the structure in the
`
`specification of the challenged patent that performs the claimed function. I
`
`understand that a structure disclosed in a prior art reference can be equivalent if (a)
`
`the prior art element performs the identical function specified in the claim in
`
`substantially the same way, and produces substantially the same result as the
`
`corresponding element disclosed in the specification, (b) a person of ordinary skill
`
`in the art would have recognized the interchangeability of the element shown in the
`
`prior art for the corresponding element disclosed in the specification, or (c) there are
`
`insubstantial differences between the prior art element and the corresponding
`
`element disclosed in the specification.
`
`V. LEVEL OF ORDINARY SKILL IN THE ART
`I have been informed and understand that claims are construed from the
`23.
`
`perspective of a person of ordinary skill in the art (“POSITA”) at the time of the
`
`claimed invention.
`
`8
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`

`

`24.
`
`In my opinion, a POSITA with respect to the ’444 patent would have
`
`(a) a Bachelor of Science degree in electrical or computer engineering (or a related
`
`academic field), and at least two (2) additional years of work experience in the design
`
`and development of radio frequency circuits and/or systems, or (b) at least five (5)
`
`years of work experience and training in the design and development of radio
`
`frequency circuits and/or systems.
`
`25.
`
`In view of my qualifications, experience, and understanding of the
`
`subject matter of the claimed invention, I believe that I meet the above-mentioned
`
`criteria and consider myself a person with at least ordinary skill in the art pertaining
`
`to the ’444 patent.
`
`VI. GENERAL OVERVIEW OF THE TECHONOLOGY
`26. The ’444 patent relates to wireless communication and, more
`
`particularly, to frequency up-conversion and down-conversion of electromagnetic
`
`(EM) signals.
`
`A. Wired communications.
`27. Traditional wired communications networks transmit audio signals
`
`over wire lines by converting audio signals to electrical signals and back to audio
`
`signals.
`
`9
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`
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`28. When Bob speaks into a phone, Bob’s phone converts his voice (low
`
`frequency audio signals) into electrical signals. Electrical signals are transmitted
`
`over wires to Alice’s phone, which converts the electrical signals back into audio
`
`signals so that Alice can hear Bob’s voice.
`
`B. Wireless communications.
`29. Similar to wired communications, in wireless communications, low
`
`frequency audio signals are converted into electrical signals. In wireless
`
`communications, instead of travelling through wires, the signals are transmitted
`
`through air as radio waves (electromagnetic (EM) waves).
`
`
`
`30. As shown above, wireless devices use high radio frequency (RF)
`
`signals (e.g., above 300 MHz (red)) because high frequency signals can carry more
`
`information and because high frequency antennas can physically fit within small
`
`10
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`

`

`devices such as cellular phones.
`
`
`
`31.
`
`In a wireless communication, when Bob speaks into his cell phone,
`
`Bob’s cell phone converts his voice (low frequency audio signal) into a high
`
`frequency RF signal. The RF signal is transmitted over the air to Alice’s cell phone.
`
`Alice’s cell phone then converts the RF signal back into a low frequency audio signal
`
`and Alice can hear Bob’s voice.
`
`Frequency.
`C.
`32. Frequency is the number of cycles of a wave per unit time (second).
`
`33. As shown above, a high frequency signal has more cycles of a wave per
`
`second than a low frequency signal. Notably, the frequency of an audio wave can be
`
`
`
`11
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`

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`one thousand cycles per second whereas the frequency of a radio wave can be one
`
`billion cycles per second.
`
`D. Up-conversion.
`In order to transmit an audio signal over air, a wireless device must
`34.
`
`transform the audio signal to an RF signal. Since the RF signal is used to carry the
`
`information in the audio signal, the RF signal is referred to as a “carrier signal.” And
`
`since audio waves are at a low frequency, they are referred to as “baseband,” a
`
`“baseband signal” or at a “baseband frequency.”
`
`
`
`35.
`
`In order to transport the baseband (audio) signal, the transmitting
`
`wireless device (e.g., Bob’s cell phone) modifies the carrier signal. As shown above,
`
`the baseband signal is impressed upon the carrier signal (above left), thereby
`
`modulating/changing the shape of the carrier signal to approximate the shape of the
`
`baseband (audio) signal (above right).1 The modified signal is referred to as a
`
`“modulated carrier signal.” The process is referred to as “up-conversion” because
`
`
`1 This type of modification is referred to as amplitude modulation. Modulation can
`
`occur by modifying other properties of the carrier signal such as frequency or phase.
`
`12
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`

`

`the low frequency signal is being up-converted to a high frequency signal.
`
`E. Down-conversion.
`In order for the receiving wireless device (e.g., Alice’s cell phone) to
`36.
`
`recover the baseband (audio) signal from the modulated carrier signal, the receiving
`
`wireless device must transform the modulated carrier signal back to an audio signal.
`
`This process is referred to as “down-conversion” because a high frequency signal is
`
`being down-converted to a low frequency signal.
`
`37. As shown above, “down-conversion” is the process by which the
`
`baseband (audio) signal is recovered from the carrier signal. Down-conversion is the
`
`
`
`subject of claims 2-4 of the ’444 patent.2
`
`VII. DETAILED TECHNOLOGY BACKGROUND
`A. Radio frequency.
`
`
`2 While Section VI provides an overview of the technology using voice/audio
`
`signals, this is for illustrative purposes only. The technology of the ’444 patent can
`
`be used to up-convert or down-convert any type of electromagnetic signal that
`
`carries information, such as video, web, and other types of data.
`
`13
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`

`

`38. The term “radio frequency” or “RF” refers to the frequency at which a
`
`radio transmits an electromagnetic (EM) signal over the air. While “radio frequency”
`
`is abbreviated as RF, RF itself is used as a term which acquires specific meaning in
`
`context. For example, if the context is referring to a signal, then “RF” means “radio
`
`frequency signal.” If, however, the context is referring to a circuit, then “RF” means
`
`“radio frequency circuit.” RF as a modifier always is referring to an element that
`
`exists at a frequency of a radio signal that is transmitted or received as a wireless
`
`electromagnetic signal.
`
`
`
`39. As shown above, the RF signal transmitted over the air is a sinusoidal
`
`wave. As discussed in Section VII.H below, in order to transmit information (e.g.,
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`voice, data) in the wave, certain characteristics (amplitude, frequency and/or phase)
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`of the wave are varied (modulated).
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`40. The RF spectrum is part of the electromagnetic (EM) spectrum. A broad
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`categorization of the EM spectrum is shown in the table below.
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`41. RF signals and RF circuits are identified by the frequencies at which
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`information is coherently generated, radiated by a transmit antenna, propagated
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`through air, and collected by a receiver antenna. Today, the RF spectrum is
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`recognized as being between 3 hertz (Hz) and 300 gigahertz (GHz). For example,
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`radios operating at very low frequencies of a few hertz are used for submarine and
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`underground mine communication since electromagnetic waves at these frequencies
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`can penetrate water and earth. As another example, radios at 10s and 100s of
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`gigahertz (GHz) are used for radar and very high data rate, almost beam-like
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`communications. Cellular phones, for example, mostly operate at frequencies from
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`300 MHz to 6 GHz.
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`42. The frequency of an RF signal determines the size of the antenna
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`needed to transmit the signal and the amount of information that can be transmitted
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`in the signal. High frequencies, such as the frequencies used by cellular phones, are
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`ideal for mobile communications. The higher the frequency, the smaller the size of
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`an antenna and the greater the capacity to carry information. At frequencies between
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`300 MHz and 6 GHz, the size of the antenna can fit within the physical confines of
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`a mobile device and the radio waves can bend around objects (e.g., buildings)
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`(known as diffraction) and pass through walls. Frequencies above 6 GHz can also
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`be used e.g., for 5G mobile devices, but there are trade-offs. For example,
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`frequencies above 6 GHz allow for high data rates, but these signals cannot penetrate
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`buildings and do not bend around buildings as well as the lower cellular frequencies.
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`Basic circuit concepts.
`B.
`43. RF signals are created using electronic circuits. To understand circuits,
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`it is important to understand the concepts of charge, voltage, current, energy, power,
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`resistance and impedance.3
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`44. Charge: In a circuit, there are two physical types of charge – positive
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`charge and negative charge. Protons have a positive charge (+), and electrons have
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`a negative charge (–).
`
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`3 In circuits, information can be conveyed either as charge, voltage, or current.
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`
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`45. As shown above, protons and electrons are components of an atom.
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`Protons are fixed in position in the center of an atom (in the atom’s nucleus).
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`Electrons orbit the nucleus. Atoms are locked into a conductor’s (such as a
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`wire/metal) crystal lattice. Generally, the number of electrons balances the number
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`of protons so that the overall charge on an atom is neutral.
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`46.
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`In an electrical conductor, while most electrons are bound to an atom,
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`some of the electrons are free to roam/move through the conductor. These so-called
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`free electrons can be forced to move by the application of an electric field. If a
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`number of free electrons bunch together in a region of a material, then that region is
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`said to have a net negative charge. If free electrons are forced out of a region, then
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`that region is said to have a net positive charge as the number of electrons in the
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`region will be less than the number of protons.
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`47. Circuits operate based on the movement of electrons and the movement
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`of charge transfers energy. An electron has potential energy, also called electric
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`potential energy or just electrical energy. When charges move, the potential energy
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`can be maintained or some of it can be converted to another form such as thermal
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`energy. Charge may build up to establish a voltage signal. Here, a voltage signal
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`refers to information that is almost entirely conveyed as a voltage. Alternatively, the
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`movement of charge, the rate of which is current, may itself be the signal. Most
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`circuits convey information, i.e., present signals, as a voltage or as a current.
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`48. Voltage: Voltage is the difference in an electron’s potential energy, per
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`unit charge, between two points. In other words, voltage is the amount of potential
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`(electrical) energy available, per unit charge. Negative charges (electrons) are pulled
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`towards higher voltages, while positive charges (protons) are pulled towards lower
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`voltages. Since protons are fixed in position, the negative charges (electrons) are
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`pushed away from lower voltages.
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`49. Electric current: An electric current is the movement/flow of charge in
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`a circuit (in a conductor or into, out of, or through an electrical component). As
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`shown by the arrows below, current (the net rate of movement of positive charges)
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`flows from positive voltage to negative voltage. I note that a battery and wire have
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`residual resistance.
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`50. Electric energy: Electric energy is energy that results from the
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`
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`movement of a charge in a circuit. The faster the charges move and the more charges
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`that move, the more energy they carry. The only way to transfer energy is by
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`transferring charge. So, movement of a charge indicates movement of energy.
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`51.
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`I will explain energy in the context of a resistor (see Section VII.E.3 for
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`discussion of resistors). As electrons travel through a resistor, some of the potential
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`energy of the electrons is converted to thermal energy and the resistor heats up. The
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`difference in the potential energy of the electrons before and after passage through
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`the resistor is the voltage V. It is the passage of electrons through the resistor that
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`forms the v