111111111111111111111111111111M11111111111111111111111111111111
`
`United States Patent [19]
`Taylor et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,764,693
`Jun. 9, 1998
`
`[54] WIRELESS RADIO MODEM WITH
`MINIMAL INTER-DEVICE RF
`INTERFERENCE
`
`[75]
`
`Inventors: Bryan Taylor; Mihal Lazaridis, both
`of Waterloo; Peter Edmonson,
`Hamilton; Perry Jarmuszewski.
`Guelph; Lizhong Zhu, Waterloo;
`Steven Carkner, Waterloo; Matthias
`Wandel, Waterloo, all of Canada
`
`[73] Assignee: Research In Motion Limited,
`Waterloo, Canada
`
`[21] Appl. No.: 488,695
`
`[22] Filed:
`
`Jun. 8, 1995
`
`Related U.S. Application Data
`
`[63] Continuation-in-part of Ser. No. 337,841, Nov. 14, 1994,
`Pat. No. 5,619,531.
`[51] hit. C1.6
` HO4L 5/16; HO4L 27/10
` 375/222; 375/274; 455/73
`[52] U.S. Cl.
`[58] Field of Search
` 375/222, 295,
`375/298, 308, 261, 219, 316, 340, 274,
`336, 305, 329, 279; 379/93.01; 455/73,
`88. 86; 332/103, 100; 329/300. 304
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5/1978
`11/1983
`12/1985
`12/1986
`2/1987
`5/1987
`
`Rogers, Jr. .
`Guyton .
`Futakuchi.
`Smith .
`Backof, Jr. et al. .
`Kirchner et al. .
`
`4,087,756
`4,418,320
`4,562,404
`4,630,314
`4,646,326
`4,665,519
`
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`0416423
`3/1991 European Pat. Off.
`0494696
`7/1992 European Pat. Off. .
`0531100
`3/1993 European Pat. Off. .
`0584872
`3/1994 European Pat. Off. .
`
`0599632
`6/1994 European Pat. Off. .
`0631398 12/1994 European Pat. Off. .
`
`(List continued on next page.)
`
`OTHER PUBLICATIONS
`
`Electronic Design. vol. 41. No. 16, 5 Aug. 1993 pp. 45-50,
`Leonard `PCMCIA—sized radio links portable WLan termi-
`nals' see figure 2.
`IEICE Transactions On Communications, vol. E76—B. No.
`8, Aug. 1993 pp. 990-995, Takehara `A SAW—based spread
`spectrum wireless LAN system'see figures 2. 3. 7.
`IEEE Transactions On Vehicular Technology, vol. 43, No. 4.
`1 Nov. 1994 pp. 863-869, Mitsutaka Hikita et al `A wide-
`band SAW resonator and its application to a VCO for movile
`radio transceivers' see abstract.
`"Surface Transverse Wave Based FM Modulator/Demodu-
`lator", Reprinted from Electronics Letters 15th Mar. 1990
`vol. 26 No. 6 pp. 364-365.
`"A Surface Transverse Wave—Based MSK System", Ivan D.
`Avramov, P.J. Edmonson, Member, IEEE. Peter M. Smith,
`Member, JEFF JEFF Transactions On Ultrasonics. Ferro-
`electrics, And Frequency Control Vol. 38, No. 3. May 1991.
`Product Note 11729B-1 Phase Noise Characterization Of
`Microwave Oscillators Phase Detector Method Hewlett
`Packard, Aug. 1983.
`
`Primary Examiner—Tesfaldet Bocure
`Attorney, Agent, or Firm Jones. Day. Reavis & Pogue;
`Charles B. Meyer
`
`[57]
`
`ABSTRACT
`
`A wireless radio modem that may be incorporated into a host
`system or connected through a PCMCIA or similar port to a
`host system includes radio frequency modulation/
`demodulation circuitry employing electronic device ele-
`ments that operate in a frequency range that minimizes the
`RF interference between the radio modem and the host
`system. Radio modem power conservation is maximized by
`1) simplifying signal modulation processing by use of a
`two-point waveform transition table, thereby reducing pro-
`cessing requirements; and 2)incorporating a "sleep mode"
`feature in which all non-timer circuitry is powered-down
`when not in use.
`
`12 Claims, 8 Drawing Sheets
`
`1014 Ue
`
`SCC
`
`T I ER
`
`25
`RA
`
`OS^
`
`26
`
`VF
`
`1
`
`01mODUL A ToR
`RNA% SHIFTER
`
`H
`
`, r PTTR LNA
`
`rifILIE[P
`
`5084
`CONvERTE
`
`12
`I,
`IF
`CHANNEL SWIM NOISE
`FILTER
`AMP
`FILTER
`
`LIM
`
`LPF OP AMP LPF
`
`A/0
`
`4
`
`5,
`
`9
`
`" 'la
`
`I I
`
``•-• 3
`
`.1'14
`
`RSS I
`
`52
`
`50
`
`R,
`
`T/R CONTROL
`
`SMI
`
`306
`SPL I 1 TER
`
`ISOLATION
`AMP
`
`40816 600
`AK,
`FILTER
`
`EAC 1 TER
`AMP
`
`56
`
`LO
`
`42
`
`3
`
`13S
`
`34
`
`90°
`
`40
`
`132
`
`AIRES' 0161 TAI
`OUAORATURE MODULATOR
`
`16 ` 17
`LPF DPW LPF
`
`IR
`
`-.19
`A/0
`
`\
`
`LOS
`
`a
`
`PP
`
`0/2
`
`28
`
`30
`0/4
`
`LPF
`
`29
`
`LG Ex. 1014
`LG Electronics Inc. v. ParkerVision, Inc.
`IPR2022-00245
`Page 00001
`
`

`

`5,764,693
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`7/1987 Somer .
`4,682,344
`6/1989 Crowle
`4,843,613
`1/1990 Eastmond et al. .
`4,893,347
`4,962,510 10/1990 McDavid et al.
`5,020,093
`5/1991 Pireh .
`5230,094
`7/1993 Kitching et al. .
`7/1993 Deguchi .
`5,231,647
`5,313,211
`5/1994 Tokuda .
`
`375/295
`
`375/308
`
`5/1994 Wallace .
`5,317,707
`9/1994 Moura et al. .
`5,347,304
`5,548,253 8/1996 Durant
`
`375/296
`
`FOREIGN PATENT DOCUMENTS
`
`Japan .
`62-292005 12/1987
`930577
`5/1982 U.S .S .R. .
`8/1983 United Kingdom .
`2114392
`2261345 5/1993 United Kingdom .
`
`IPR2022-00245 Page 00002
`
`

`

`8 JO I ;nags
`
`ao
`
`=
`
`limed °S.il
`
`A/D
`
`LPF OPAMP LPF
`
`15
`
` FILTER AMP FILTER LIM
`
`MEM TIMER
`
`SCC
`
`27L
`
`DATA I/O
`
`12-'
`
`PHASE SHIFTER
`DEMODULATOR
`
`IF
`
`IF
`
`DOWN
`
`IMAGE CONVERTER CHANNEL GAIN NOISE
`
`FILTER LNA FILTER
`BANO
`
`pP
`
`24-) 25) H
`
`;RAM
`
`23
`
`22
`
`21
`
`20
`
`RSS I
`
`52S-
`
`26
`
`DSP
`
`19
`
`A/D
`
`18
`
`LPF OPAMP LPF
`
`17
`
`16
`
`14
`
`13
`
`11
`
`10
`
`S1 9
`
`T
`
`5)6 718
`
`4
`
`3
`
`Id
`
`29
`
`31
`
`L54
`
`0
`
`0/A
`
`LPF
`
`3P 28
`
`53
`
`D/A
`
`LPF
`
`36
`
`LO1
`
`34
`
`35
`
`33
`
`9
`
`DIRECT DIGITAL
`
`MODULATOR
`QUADRATURE
`
`Fig. I a
`
`55
`
`37
`
`38
`
`57
`
`40
`
`42 41
`
`FILTER
`56 BAND
`
`'2-39
`
`POWER BAND EXCITER
`
`AMP
`
`AMP FILTER
`
`SPLITTER
`
`3dB
`
`T/R CONTROL
`
`50-\_,
`
`SWITCH
`
`El7Tx/Rx
`
`2
`
`IPR2022-00245 Page 00003
`
`

`

`waled °S'fl
`
`8 JO Z ;aaiS
`
`29
`
`31
`
`D/A
`
`LPF
`
`28
`
`30
`
`D/A
`
`LPF
`
`54
`
`53
`
`(
`
`\12—
`
`t
`
`20 21
`
`QUADRATURE MODULATOR
`
`DIRECT DIGITAL
`
`34
`0 S 35
`
`33
`
`I
`
`Fig. 1 b
`
`40
`
`42 41
`
`AMP FILTER
`POWER BAND EXCITER
`
`AMP
`
`ISOLATION 7/7
`
`AMP
`
`L.-43
`LO
`
` 56
`
`RSSI
`
`52-C-
`
`SPLITTER
`
`3dB
`
`50-\_„
`
`iiTx/Rx . T/R CONTROL
`
`SWITCH
`
`2
`
`26
`
`11
`
`OSP
`
`19
`
`A/D
`
`18
`
`LPF OPAMP LPF
`
`17
`
`16
`
`14
`
`13
`
`11
`
`10
`
`51 9
`
`4 5 6 7J 8
`
`3
`
`MEM TIMER
`
`-) 252 H
`
`:RAM
`
`24
`
`SCC
`11
`
`27-L.
`
`DATA I/O
`
`A/D
`
`LPF OPAMP LPF
`
`15
`
` FILTER AMP FILTER LIM
`
`PHASE SHIFTER 1
`
`/
`
`DEMODULATOR
`
`12S--
`
`IF
`
`IF
`
`DOWN
`
`IMAGE CONVERTER CHANNEL GAIN NOISE
`
`FILTER LNA FILTER
`BAND
`
`
`di
`
`7:
`
`l
`
`IPR2022-00245 Page 00004
`
`

`

`V.7
`01
`
`g jo £ ;aaqS
`
`oo
`vo
`
`=
`
`lualnd °S11
`
`26
`
`NP
`
`DSP
`
`8
`
`:RAM
`
`24)25 2 t--1
`
`MEN TIMER
`
`SCC
`
`277._
`
`DATA I/O
`
`8
`
`29
`
`31
`
`D/A
`
`LPF
`
`SYNTH CONTROL
`
`8
`
`28
`
`30
`
`0/A
`
`LPF
`
`23
`
`22
`
`20 21
`
`A/0
`18 19
`
`LPF OPAMP LPF
`
`16 17
`
`A/0
`
`LPF OPAMP LPF
`14
`15
`
`PHASE SHIFTER
`DEMODULATOR
`
`T- 208
`
`LOCAL OSCILLATOR
`
`MODULATION
`
`‘./.`
`
`209
`
`REF
`
`LPF
`
`SYNTH
`
`CONTROL
`
`MODULATION
`202
`
`VCO
`
`VCTCXO
`
`201
`
`Fig. 2
`
`210
`
`211
`
`212
`
`40
`
`42 4 1
`
`(2
`111111---
`
`SPLITTER
`
`3dB
`
`AMP FILTER EXCITER
`
`POWER BAND
`
`SWITCH
`Tx/Rx 4 T/R CONTROL
`
`RSS[
`
`13
`
`52
`
`11
`
`10
`
`9
`
`213 ti
`
`6 7 8
`
`4
`
`3
`
`FILTER GAIN FILTER LIM
`CHANNEL IF
`
`NOISE
`12
`
`IF
`
`CONVERTER
`
`DOWN
`
`FILTER LNA FILTER
`IMAGE
`BAND
`
`IPR2022-00245 Page 00005
`
`

`

`S JO r PaqS
`
`00
`
`'Iowa °S71
`
`23
`
`22
`
`21
`
`.11•••••
`
`.1=.1
`
`DSP
`
`8
`
`:RAM
`)
`
`24 25
`
`HOST
`
`200z,
`
`A/D
`18 19
`
`LPF OPAMP LPF
`
`17
`
`A/D
`
`LPF
`
`LPF OPAMP
`14
`15
`
`PHASE SHIFTER 1
`
`DEMODULATOR
`
` FILTER GAIN FILTER LIM
`
`NOISE
`
`CHANNEL IF
`
`12S-
`
`IF
`
`DOWN
`
`CONVERTER
`
`FILTER LNA FILTER
`BAND
`
`IMAGE
`
`-1
`
`0;
`
`8
`
`29
`
`-71-208
`
`31
`
`LOCAL OSCILLATOR
`
`VCICX0
`
`201
`
`D/A
`
`LPF
`
`SYNTH CONTROL
`
`MODULATION
`
`209
`
`REF
`
`8
`
`28
`
`30
`
`D/A
`
`LPF
`
`LPF
`
`SYNTH
`
`CONTROL
`
`MODULATION
`202
`
`VCO
`
`20
`
`RSSI
`
`52S—
`
`(3 16
`
`11
`
`10
`
`9
`
`Fig, 3
`
`210
`
`211
`
`212
`
`40
`
`42 41
`
`SPLITTER
`
`3dB
`
`AMP FILTER EXCITER
`
`POWER BAND
`
`SWITCH
`Tx/Rx ... T/R CONTROL
`2
`213-\
`
`:::
`
`7 8
`
`4
`
`3
`
`IPR2022-00245 Page 00006
`
`

`

`U.S. Patent
`
`Jun. 9, 1998
`
`Sheet 5 of 8
`
`5,764,693
`
`r400
`
`NO
`
`IS TASK LIST ft
`EMPTY ?
`
`YES
`
`401
`
`SET SERIAL CONTROLLER TO GENERATE
`INTERRUPT ON HOST DATA RECEIVED.
`SET UP TIMER TO GENERATE INTERRUPT
`AFTER DESIRED TIMEOUT PERIOD.
`
`402 -I
`
`UNMASK THE
` NMI TO THE
`PROCESSOR
`
`V
`
`HALT
`PROCESSOR
`
`404
`
`UNEXPECTED NMI
`
` j) FORCE SOFTWARE TO
`
`CONTINUE FROM NEW
`LOCATION IN CODE
`
`EXPECTED NMI
`
`•-•-• 403
`
`Fig. 4
`
`IPR2022-00245 Page 00007
`
`

`

`8 JO 9 ;aaQS
`
`00
`‘.1
`
`Juar641 *S'Il
`
`Fig, 5
`
`GND
`
`1,44_ GND
`
`vcc
`
`1
`
`L T11 2 1 ACS8
`-5
`SHON GNO
`GNO
`GNO —LI-004
`OUT
`U301 502 V,SC
`
`200K
`R301
`
`IN
`T 8
`VBATT VBATT
`
`TURNONI
`
`10K TURNONI
`R305
`
`WV'
`
` '
`
`20K
` R307 GNO
`MARK
`IN
`I MB T3904
` 0303
`B01
`GND
`ARK
`IN
`I MB T3904
`0301
`
` )
`
`1M
`'7
`
`
`
`IVVVL—•--
`
`MARK
`IN
`IMBD4148
`302DON I
`0
`B03
`
`501
`ON I
`
`ON I
`
`GND
`ILMARK
`IN
`I MB T 3904
`B02
`0302
`CO2
`100K
`100K
`R303
`200K R302
`R304
`500 IMBD4148
`VBATT
`SHDN
`
`100K
`R306
`MARK IN
`0301
`
`TURNON TURNON
`
`IPR2022-00245 Page 00008
`
`

`

`limed °S11
`
`8 JO L pagS
`
`600
`
`OFF
`POWER
`
`DOWN
`POWER
`CONTROL
`
`'.............'--..
`
`F19. 6
`
`NORMAL OPERATING MODE
`
`BOOTS
`POWER SYSTEM
`
`ON
`
`
`
` 1
`
`(ACTIVE HIGH)
`POWER SUPPLY
`
`(ACTIVE LOW)
`ON INDICATION (ONI)
`
`601
`
`HOST (ACTIVE HIGH)
`TURNON SIGNAL FROM
`
`IGNORED
`GLITCHES
`
`ONI
`
`u
`
`07---SIGNAL
`TURNOFF
`VALID
`
`IGNORED---\
`GLITCH
`TURNOFF
`
`SIGNAL —\
`TURNON
`VALID
`
`IPR2022-00245 Page 00009
`
`

`

`U.S. Patent
`
`Jun. 9, 1998
`
`Sheet 8 of 8
`
`5,764,693
`
`ONE
`BIT TIME
`
`0
`
`0
`
`1
`
`0
`
`0
`
`700 -5-
`
`d
`
`e
`
`701 -)
`
`702 -5
`Fig. 7a
`
`ONE
`BIT TIME
`
`0
`
`0
`
`0
`
`0
`
`704
`
`703 -5
`
`S
`706-)
`705 3
`Fig. 7b
`
`IPR2022-00245 Page 00010
`
`

`

`5,764,693
`
`1
`WIRELESS RADIO MODEM WITH
`MINIMAL INTER-DEVICE RF
`INTERFERENCE
`
`2
`ing performance predominately as a result of radio fre-
`quency interference caused by electrical noise generated by
`the host unit.
`
`5
`
`SUMMARY OF THE INVENTION
`
`This application is a continuation-in-part of U.S. patent
`application Ser. No. 08/337.841. filed Nov. 14, 1994 entitled
`"Wireless Radio Modem With Minimal Interdevice RF
`Interference", now issued as U.S. Pat. No. 5,619,531 on Apr.
`8. 1997.
`
`COPYRIGHT NOTICE
`
`10
`
`Portions of the disclosure of this patent document, includ-
`ing the appendices, contain material that is subject to copy-
`right protection. The copyright owner has no objection to the
`5
`facsimile reproduction by anyone of the patent document or 1
`the patent disclosure as it appears in the Patent and Trade-
`mark Office patent file or records, but otherwise reserves all
`copyright rights whatsoever.
`
`20
`
`25
`
`30
`
`TECHNICAL FIELD OF THE INVENTION
`This invention relates generally to data communication at
`radio frequencies in a wireless environment and, in
`particular, to a method of wireless data communication and
`to a device that can be imbedded within a host data pro-
`cessing or communications unit (such as a PC, a laptop. a
`workstation, a personal digital assistant (PDA), a two-way
`pager or other equipment for data communications or
`processing) or attached directly through an external data
`interface, such as one that is constructed and controlled in a
`manner that meets the standards set forth in two documents
`entitled "PC Card Standard," Release 2.0, and "Socket
`Services Interface Specification." Release 1.01, both pub-
`lished by the Personal Computer Memory Card International
`Association (PCMCIA), in September 1991. As will be
`appreciated by reference to the specification that follows,
`although communication through a PCMCIA interface is
`preferable, the invention is not restricted to a particular
`communication interface and may be connected in any
`manner to a host data processing or communications unit
`(either, a "host unit"), or integrated into such a unit. The
`method and device enables a host unit to transmit data to and
`receive data from a communication network wirelessly so
`that the RF interference between the host unit and the radio
`modem is minimized and power consumption is at a reduced
`level. It is envisioned that in its preferred use, the invention
`will be used to communicate between a host unit and a
`remote data processing or communications device, either
`directly or via a network through a data transmission/
`reception network station.
`
`BACKGROUND OF THE INVENTION
`
`Wireless radio modems are used to permit remotely
`located computers and other data communications equip-
`ment to communicate with one or more other computers or
`equipment for data communications, usually as part of a
`computer network. Over the past several years, a number of
`efforts have been undertaken to reduce the size, weight,
`power consumption and portability of radio modems in
`order to increase their attractiveness to both the technical
`community and the consuming public. In spite of advances
`in technology, most state of the art radio modem designs
`usually involve a flexible cable connection to the host unit
`and a bulky external battery pack to supply the necessary
`power. Previous attempts to incorporate a radio modem
`within a host unit or to connect a radio modem through a
`PCMCIA interface have resulted in extremely poor operat-
`
`The present invention has utility in allowing a host unit to
`communicate with a wireless network. The present inven-
`tion is a wireless radio modem that is designed to be located
`within a host unit, or connected to a host unit through an
`external port. such as a PCMCIA interface, so that the host
`unit can communicate with other units for data processing or
`communication via a wireless data network. In its preferred
`embodiment, the radio modem is designed to operate in a
`wireless data network that uses packet-switched communi-
`cation such as a network that uses the MobitexTM network
`protocol, the ArdisTM network protocol or the Celluar Digital
`Packet Data (CDPD) wireless network protocol. The radio
`modem design allows different network protocols to be
`supported by software changes only (i.e.. with no substan-
`tive hardware modifications), so the scope of the invention
`is not limited to any specific protocol. For the preferred
`embodiments, however, reference is made to the MobitexTM
`standard, which is a published communications standard for
`the MobitexTM wireless network. The references herein to
`the standard shall mean the Mobitex Interface Specification,
`Rev. 3A, published September 1994 and available from
`RAM Mobile Data. 10 Woodbridge Center Drive.
`Woodbridge, N.J. 07095.
`The radio modem is preferably designed to be built into
`a host unit (the OEM version) or to be directly connected to
`a host unit through a PCMCIA interface (the PCMCIA
`version), although the design may be incorporated into a
`stand-alone modem separate from the host unit. Both the
`35 size and performance of the present invention represent a
`significant improvement over the state of the art.
`The radio modem hardware and software of both the
`OEM version and the PCMCIA version are carefully
`designed to minimize power consumption. In the preferred
`ao embodiments. each version can be configured in one of two
`forms: (i) with an on-board microprocessor that provides
`overall control of the operation of the various subsystems of
`the radio modem (the "on-board processor form") or (ii)
`without an on-board processor, whereby the essential control
`45 functions that are performed by the microprocessor in the
`on-board processor form are performed by the host unit
`microprocessor (the "microprocessor-less form"). To reduce
`power consumption significantly in each version. the key
`power-consuming components are placed into lower power
`50 modes when they are not needed and are placed in a higher
`power mode only when data that the radio modem is to
`process are detected or when a predetermined period time
`has elapsed from the point the components have been put
`into a lower power or a "sleep" mode. As one of ordinary
`55 skill in the art of digital communications equipment design
`will appreciate, the microprocessor is one of the key power-
`consuming components in the on-board processor form. In
`addition to the power management circuitry. the method of
`operation of each version of the radio modem was optimized
`60 to reduce power consumption using low-power components
`and power-efficient design where possible.
`Operational performance is also enhanced over the state
`of the art because both versions of the radio modem are
`designed to operate in the high electrical noise environment
`65 present within. or immediately proximate to a host unit. The
`major electrical noise immunity strategy employed is the use
`of circuitry designed to operate outside the electrically noisy
`
`IPR2022-00245 Page 00011
`
`

`

`5,764.693
`
`3
`frequency bands that are present within an operating data
`processing unit. Among the features that enable the modem
`to avoid the RF interference of its host data processing unit
`is the implementation of frequency discrimination at an
`intermediate frequency (at or above 10.7 MHz) that is well
`above the noise frequencies emanating from the operation of
`a host unit.
`In order to generate the intermediate frequency at which
`discrimination takes place, the receiver circuitry uses a
`single intermediate frequency down conversion step. In the
`preferred embodiment, the intermediate frequency is 45
`MHz. After down conversion the signal is channel filtered
`and then demodulated and digitized. The resulting digitized
`signal is then conveyed to a digital signal processor ("DSP")
`where the data is recovered and conveyed to the host unit.
`On the transmission side, the transmitter circuitry accepts
`data from the host unit, via the DSP, in a pre-modulated
`form. In the preferred embodiment, the data received by the
`transmitter is modulated using either quadrature modulation
`or baseband modulation, although one of ordinary skill in
`the art will appreciate that various modulation techniques
`could be applied to modulate the signal received from the
`DSP.
`Quadrature Modulation
`In the implementation in which the data are quadrature
`modulated, the DSP presents the signal to the modulation
`circuitry in in-phase and quadrature phase components. The
`signal is then modulated directly, using quadrature
`modulation, and is filtered, amplified, upconverted, filtered
`and then amplified again before being conveyed, via a
`transmit/receive switch, to an antenna for propagation.
`Baseband Modulation
`In the implementation in which the data is baseband
`modulated, the DSP presents the signal to the modulation
`circuitry in the form of two modulation voltage signals for
`the Voltage Controlled Temperature Compensated Crystal
`Oscillator (VCICX0) and Voltage Controlled Oscillator
`(VCO). The signal is then frequency modulated, using
`baseband modulation and is filtered and then amplified
`before being conveyed, via a transmit/receive switch, to an
`antenna for propagation.
`Modulation Lookup Tables
`The modulation scheme, in the preferred embodiment.
`relies upon pre-calculated wave segments that are pieced
`together at run time to produce smooth Gaussian Minimum
`Shift Keyed (GMSK) or GMSK Inphase (I) and Quadature
`Phase (Q) modulated waveforms. For efficiency purposes
`and to reduce the processing time required to modulate the
`signal (and thus the processing power required), a look-up
`table stored preferably in DSP memory is employed as a part
`of the modulation process.
`In the case of quadrature modulation, the look-up table
`provides precalculated waveform segments that are pieced
`together, taking into account the interrelationship of a digital
`four bit transmission stream on the waveform shape asso-
`ciated with the second bit of the four bit stream. Simple
`transforms are used to phase shift this signal by steps of 90
`degrees, to compensate for the different phases that the I and
`Q channels may be in at the start of the segment.
`In the case of baseband modulation, instead of using the
`I and Q channels, baseband signals are encoded. Thus, it is
`only necessary to have one channel instead of two, as both
`channels are either the same, or related by a constant
`multiple. The need to shift the signal by 90 degrees is no
`longer necessary in baseband, as there is no need to use
`accumulated phase from previous bits.
`
`to
`
`4
`The modulation tables, in the preferred embodiment, were
`generated by a program called MODTAB. MODTAB.C, the
`main c source file found in Appendix A, contains the
`mathematics to generate the modulation tables. The formu-
`5 las in this code implement the modulation scheme in a
`simplified form and the source code is structured in such a
`manner that certain of its modules can be used to generate
`tables for quadrature phase modulation and not used when
`baseband modulation tables are desired.
`For both types of modulation, the GMSK wave form is
`first calculated and used to generate a baseband modulated
`wave form. To FM modulate the baseband GMSK signal
`into I and Q signals for quadrature phase modulation, a
`phase accumulator is used. Because frequency is a rate of
`15 phase change, the baseband values from the GMSK wave
`form represent the rate of change of the phase accumulator.
`The Sine and COSINE of value in the phase accumulator is
`then used to calculate the I and Q signals. Optionally, the
`effect of an RC filter on the I and Q signals can be
`20 compensated for by applying the inverse function of an RC
`filter to the I and Q signals. Thus, the output of the RC filter
`can be forced to correspond with the desired wave form. The
`math is performed in a laborious manner, using floating
`point evaluation. For each possible combination of four bits,
`25 all the shapes for all four bits are generated. To build the
`tables, the interval between the centers of bits 2 and 3 is then
`bracketed, extracted and placed in the table.
`When generating tables for baseband code, the phase
`accumulator and SINE/COSINE calculation steps are
`30 skipped. and the baseband wave forms are placed in the
`tables directly. There is also no need to compensate for RC
`filter effects in the development of the baseband table. When
`the tables are generated and stored, modulation can be
`accomplished through application of the table data.
`The object of the demodulation scheme is to provide a
`nearly optimal method for decoding bits accurately, while
`using as little processing power and additional hardware as
`possible, in order to keep power consumption and cost to a
`minimum. In order to eliminate the need for sophisticated
`4o hardware filters, the incoming signal is sampled at a rate that
`is a multiple of the bit rate. In the preferred embodiment, the
`sampling rate is six times the GMSK bit rate. A Finite
`Impulse Response (FIR) filter is applied to the signal every
`n samples. where n is the number of analog to digital
`45 converter (A/D) samples per GMSK bit. This implements a
`decimating filter, producing output samples at a rate equal to
`the bit rate. The FIR filter cuts off sharply after a frequency
`equal to half the bit rate, thus keeping to a minimum the
`amount of aliasing resulting from the decimation. This
`5o technique takes advantage of the Nyquist sampling theorem,
`fully capturing a bandwidth of half the sampling rate by
`taking periodic samples.
`Even though the effective sampling rate is equal to the bit
`rate, repetitious patterns of seemingly lower bit rates, such
`55 as a GMSK Bitsync of the pattern 110011001100, can
`nevertheless be recognized, as such a pattern produces a
`wave form similar to a sinusoid at a frequency of one fourth
`the bit rate. A series of increasingly stringent criteria is used
`to determine whether the received signal is a bit sync
`60 pattern. When all the criteria are satisfied, preferably 12
`samples of the bit sync are correlated to SINE and COSINE
`functions. Because 12 samples represent three complete
`periods of the sinusoid, compensating for different direct
`current (DC) levels is not necessary. Because the SINE and
`65 COSINE functions need only be evaluated at 90 degree
`intervals, this process is trivial. The SINE function, for
`example, takes on values of 0,1,0,-1.0,1,0,-1,0 . . . etc.. The
`
`35
`
`IPR2022-00245 Page 00012
`
`

`

`5,764,693
`
`5
`two resulting correlations of the SINE and COSINE func-
`tions are then combined to form a Cartesian vector and
`mathematically transformed through rotations of 90 degrees
`to be within an angle of +/-45 degrees. A cubic function of
`the slope of this vector is then used to approximate the
`arctangent of the resultant vector. The difference between
`the resultant angle and 45 degrees (or —45 degrees, which-
`ever is closer), divided by 90 degrees is the fraction of a bit
`by which the sampling point in the decimation filter must be
`adjusted to be coincident with the center of the GMSK bit. 10
`In the preferred embodiment, for ease of implementation,
`the adjustment is rounded to the nearest A/D sample. As one
`of ordinary skill in the art will appreciate, however,
`enhanced accuracy can be obtained by varying the shape of
`the FIR filter to accomplish shifts of less than one A/D
`sample. When the adjustment is performed, samples coin-
`cide with the centers of bits, so bit decoding can be done
`using a threshold that is a function of a DC level calculated
`from the 12 samples used for bit synchronization, as well as
`the value of the previous bit.
`
`6
`FIG. 2 is a block diagram of the hardware layout for the
`on-board processor form of the radio modem using baseband
`modulation.
`FIG. 3 is a block diagram of the hardware layout for the
`5 microprocessor-less version of the radio modem using base-
`band modulation and an external interface to the host unit.
`such as a PCMCIA interface.
`FIG. 4 is a block diagram of the operation of the interrupt
`handler for the power management hardware.
`FIG. 5 is a schematic of circuitry that provides a "soft
`turn-on".
`FIG. 6 is timing diagram for the soft turn-on function.
`FIGS. 7a and 7b relate to the operation of the pre-
`15 modulated waveform segment lookup table.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`OBJECTS OF THE INVENTION
`
`Accordingly, it is an object of the invention to provide a
`radio modem with modulation/ demodulation means that
`incorporates circuit elements that operate at frequencies
`outside the frequency range of the RF noise associated with
`the host unit in which the radio modem is installed.
`It is a another object of the invention to provide a radio
`modem in which frequency discrimination occurs at a data
`discrimination frequency of 10.7 MHz or higher.
`It is a further object of the invention to perform FM
`frequency discrimination through the use of one or more
`piezoelectric phase-shift devices, such as surface acoustic
`wave ("SAW") filters, surface transverse wave ("STW")
`filters, surface skimming bulk wave ("SSBW") filters, leaky
`SAW filters or crystal filters such that the frequency dis-
`crimination takes place outside the RF noise frequencies
`generated by the host unit associated with the radio modem.
`It is a yet further object of the invention to provide a
`stored waveform transition table as part of the digital signal
`processing circuitry to minimize processing time and power
`consumption during the digital signal processing phase of
`the operation of the radio modem.
`It is another object of the invention to provide circuitry for
`minimizing power consumption in a radio modem that
`permits the major power-consuming components of the
`radio modem to enter into an inactive or lower-powered state
`and to be later activated or repowered by the detection of
`data communications or by the expiration of a predeter-
`mined period of time, whichever occurs first.
`These objects as well as others appreciated by those of
`ordinary skill in the art will become apparent from the
`detailed description and in reference to the drawings that
`follow. The specific examples that are set forth in the
`detailed description of the preferred embodiment should be
`understood to be given for illustrative purposes only and are
`not intended to limit the spirit and scope of the invention.
`
`BRIEF DESCRIPTION OF FIGURES
`FIG. la is a block diagram of the hardware layout for the
`on-board processor form of the radio modem using quadra-
`ture modulation and two local oscillators.
`FIG. lb is a block diagram of the hardware layout for an
`alternative embodiment of the on-board processor form of
`the radio modem using quadrature modulation and a single
`local oscillator.
`
`25
`
`ao
`
`60
`
`The preferred embodiments of the present invention are
`20 radio modems that can be built into the host unit or attached
`to a host unit through a PCMCIA or similar port. Each radio
`modem generally comprises transmission/reception means
`and a modulation/demodulation means.
`With reference to FIG. la, the received signal is conveyed
`from an antenna (1) via a transmit/receive switch (2) to a
`bandpass filter (3), which is preferably an electronically-
`coupled piezoelectric device such as an acoustic wave
`device and more specifically a SAW, an STW filter. an
`30 SSBW filter or what has been commonly referred to a leaky
`SAW filter. The filtered signal is conveyed to a low-noise
`amplifier (4) and image filter (5), and to the downconverter
`(6). In the preferred embodiments, bandpass filters (3) and
`(5) are SAW filters. Within the downconverter, the signal
`35 amplified by a linear amplifier (7) is mixed with a signal (50)
`from a local oscillator (39) at the mixer (8) to produce a
`signal (51) at an intermediate frequency greater than or
`equal to 10.7 Mhz. Signal (51) is conditioned by the inter-
`mediati- frequency (IF) channel filter (9) and is amplified by
`the IF gain block (10) then conditioned by a noise filter (11).
`The resulting intermediate frequency signal is demodulated
`within the demodulator (12). In the preferred embodiment.
`the intermediate frequency is 45 MHz.
`The demodulator consists of a limiting amplifier (13) to
`45 produce a signal having constant amplitude. This signal is
`split into two parts which are mixed in a mixer (14). with one
`of the parts shifted in phase relative to the other. The phase
`shift element (15) is preferably an electronically-coupled
`piezoelectric device such as surface acoustic wave filter or
`50 a crystal filter. The demodulated signal is conditioned and
`converted to a digital representation before being conveyed
`to a digital signal processor (DSP) (24). The digital signal
`processor (24) is preferably an ADSP-2171KST-133 com-
`mercially available from Analog Devices. Inc., Norwood,
`55 Mass. The conditioning and conversion to a digital repre-
`sentation is performed by low pass filter (16), amplified by
`operational amplifier (17), conditioned by anti-aliasing filter
`(18) and converted to a digital representation by analog to
`digital converter (19).
`The limiting amplifier (13) produces a second signal (52)
`with a DC voltage proportional to the received signal
`strength at the input of the limiter. This signal is referred to
`as the Received Signal Strength Indicator (RSSI) and is
`conditioned by low pass filter (20), amplified by operational
`65 amplifier (21), conditioned by anti-aliasing filter (22) and
`converted to a digital representation by analog to digital
`converter (23).
`
`IPR2022-00245 Page 00013
`
`

`

`5,764.693
`
`7
`In the on-board processor version, the digital data is
`conveyed to the host unit via the microprocessor (uP) (26),
`preferably an Intel SB80L188EB-8 (available from Intel
`Corporation. Santa Clara, Calif.), and a serial communica-
`tions controller ("SCC") (27), preferably a Phillips SCC
`9291 (available from Phillips Electronics North America
`Corporation. Sunnyvale, Calif.). In the microprocessor-less
`version, as seen on FIG. 3, the modem utilizes the micro-
`processor of the host (200), and thus there is no need to have
`a microprocessor resident within the externally connected
`modem, i.e. within the PCMCIA form factor. Additionally,
`because of the physical connection in the preferred embodi-
`ment through the PCMCIA port. the need for an SCC is also
`eliminated. One of ordinary skill in the art will appreciate
`that each of the aforementioned components for which
`particular part numbers are not referenced are well known in
`the art,
`When the radio modem is transmitting, the data to be sent
`is conveyed from a host data processing unit, via the serial
`communications controller (27) and the microprocessor (26)
`to the digital signal processor (24). In the case of quadrature
`phase modulation, the digital signal processor (24) generates
`the appropriate in-phase and quadrature-phase modulated
`waveform segments, which are based on the current and
`previous bits to be sent, from a precalculated look-up table
`stored in the associated random-access memory (25). The
`digital signals are converted to analog signals by two
`digital-to-analog converters (28) (29). conditioned by two
`low pass filters (30) (31) and are conveyed to the quadrature
`modulator (32). Within the quadrature modulator