United States Patent
`US 6,728,520 B2
`(10) Patent No.:
`(12)
`Apr. 27, 2004
`(45) Date of Patent:
`Coanet al.
`
`US006728520B2
`
`(54) SYSTEM AND METHOD FOR CONSTANT
`LOOP GAIN IN A CLOSED LOOP CIRCUIT
`
`(75)
`
`Inventors: Phil Coan, San Diego, CA (US);
`.
`Seng-Woon Chen, San Diego, CA (US)
`:
`:
`(73) Assignee: Qualcomm Incorporated, San Diego,
`CA (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/387,137
`(22)
`Filed:
`Aug. 31, 1999
`(65)
`Prior Publication Data
`
`US 2003/0040342 A1 Feb. 27, 2003
`7
`Int. Ch.cece H04Q 11/12
`(51)
`(32) US.CI
`455/126; 455/115.3; 455/127.2:
`et ees
`,
`455/522: 455B45
`58)
`Field of S
`455 16 271
`h
`Field
`o
`wASSI1DT2.BTIL,69.26 1 Oe > 101
`(8)
`13 4 ot : 95. 100 ; {07 i5 1 115 3 109.
`52. 57) 57.4 575 545:3703.IL 3]6.
`“— 30 342 AAT: 330/129 137 389
`oe a
`moe?
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`4,901,307 A
`5,033,109 A *
`5,109,541 A *
`5,267,262 A
`
`2/1990 Gilhousenetal.
`7/1991 Kawanoetal. ............. 455/127
`AJ1992 Park 20... ccccceeecee seen 455/127
`11/1993 Wheatley, III
`
`1/1995 Wheatley, III et al.
`5,383,219 A
`3/1995 Padovanictal.
`5,396,516 A
`......... 455/126
`5,574,993 A * 11/1996 Kobayashi et al.
`ceeeeeeeeee 455/69
`oon ‘ * tito97 Gunousen “ AL.
`691,
`ehaviet al.
`5.724.645 A *
`3/1998 Na ceccccccccccccceeeseens 455/67.
`5,809,420 A *
`9/1998 Ichi
`ietal. wu... 455/12.1
`6,230,031 B1 *
`5/2001 Babeesee ass127
`
`7/2001 Moerder et al.
`.......0.. 455/115
`6,256,483 Bl *
`
`* cited by examiner
`
`Primary Examiner—Quochien B. Vuong
`(74) Attorney, Agent, or Firm—Philip R. Wadsworth;
`Gregory D. Ogrod; Jae-Hee Choi
`67)
`ABSTRACT
`A system and method for controlling transmitted output
`power of outdoor antenna units coupled to hand held wire-
`less devices. When the antenna unit
`is operating with
`wireless network technology
`it may
`also be referred to as an
`sy
`y
`outdoor unit. Transmit power level of an information signal
`is controlled in the outdoor unit by obtaining a control
`voltage from the hand held unit. The control voltage is used
`by the outdoor unit,
`to adjust
`the power
`level of the
`transmitted information signal. The transmit power level is
`adjusted by the outdoor unit performing the following steps:
`(1) detecting the transmit powerlevel of the antennaunit, (2)
`determining whether the transmit powerlevel is equal to a
`control voltage, and (3) adjusting the transmit powerlevel
`based on the control voltageif the transmit powerlevel is not
`equal to the control voltage. The adjustment of the transmit
`power level is accomplished by a closed loop circuit that
`maintains a constant loop gain.
`
`8 Claims, 6 Drawing Sheets
`
`ODU ANTENNA114
`
`CAR KIT 104
`
`-HH
`TRANSMIT
`
`.
`
`RECEIVE
`COMPONENTS
`
`COMPONENTS IDUPLEXER
`
`TO VEHICLE
`BATTERY
`
`SAMSUNG 1066
`SAMSUNG 1066
`SAMSUNG v. SMART MOBILE
`SAMSUNGv. SMART MOBILE
`IPR2022-01004
`IPR2022-01004
`
`CABLE111
`
`1
`
`POWER
`
`DUPLEXER
`
`328
`
`HAND HELD (HH)
`POWER
`RECEIVE
`COMPONENTS|ELEMENTS POWER
`
`INTERFACE
`_ SUPPLY
`INTERFACE
`
`OUTDOORUNIT (ODU)
`
`DETCTOR \
`
`1
`
`

`

`U.S. Patent
`
`Apr.27, 2004
`
`Sheet 1 of 6
`
`US 6,728,520 B2
`
`FLITISLVS
`
`VNNHLINV
`
`8zI
`
`SSATHSIM
`
`SNOILLVOINNININOD
`
`WYOMLAN
`
` OdI
`
`avo
`
`in
`
`HOA
`
`
`
`ZOLWALSASANOHdYTAOWN
`dOVASALNI
`LNdIdIona
`ALITTALVS
`POT|LINNHOOGLNG
`
`QTSHHGNVH
`VNNALNVdO
`
`AYMALV9Fel901
`
`
`
`MINITTVLISIG
`
`/INLSd
`
`dAH.LO
`
`SHUOMLAN
`SMYOM.LAN
`
`HOIAdG
`
`2
`
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Apr. 27, 2004
`
`Sheet 2 of 6
`
`US6,728,520 B2
`
`PIN
`FIG. 2A
`
`fH
`5
`2
`
`2
`
`>
`
`PIN
`FIG. 2B
`
`be
`_
`=
`
`5
`2
`
`PIN
`FIG. 2C
`
`PIN
`FIG. 2D
`
`fH
`a)
`Oo
`>
`
`PIN
`
`3
`
`

`

`U.S. Patent
`
`Apr. 27, 2004
`
`Sheet 3 of 6
`
`US 6,728,520 B2
`
`LINSNVUL
`
`HH
`
`SLNINOdWOO
`
`
`
`(HH)(TSHGNVH
`
`HH
`
`SLNYNOdNOD
`
`HATHORa
`wWaXaTdNnad
`
`LINSNVUL
`
`SINANOdNOO
`
`YaXaTdnad
`
`XTddns
`
`AIOIHSAOL
`
`¢OIA
`
`p01LITUV
`
`WAMOd
`
`WOLOLIG
`
`AOVASALNI(NdO)LINNYOoaLNO
`
`
`AUTLLVEIllATa@VO
`
`aMOdAOVAUAINI
`
`\pllVNN&LNYVNdo
`KlddnsSLNAUWNATA|SLNENOdNOO
`
`HALLOVSATHORN
`
`4
`
`
`

`

`U.S. Patent
`
`Apr. 27, 2004
`
`Sheet 4 of 6
`
`US 6,728,520 B2
`
`
`
`DETERMINE THE
`
`TYPE/RATE OF DATA TO
`
`BE TRANSMITTED
`
`FOR THE PARTICULAR TYPE
`OF DATA TO BE
`TRANSMITTED, DETERMINE
`THE REQUIRED TRANSMIT
`POWER LEVEL OF THE
`INFORMATIONSIGNAL
`
`
`
`
`
`
`
`
`
`SEND THE REQUIRED
`TRANSMIT POWER LEVEL
`
`408
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ODU ADJUSTS THE TRANSMIT
`POWER LEVEL OF ITS
`INFORMATION SIGNAL
`
`TRANSMIT COMPONENTS IN
`ODU TRANSMIT THE
`INFORMATIONSIGNAL AT
`THE APPROPRIATE TRANSMIT
`
`POWER LEVEL
`
`5
`
`

`

`U.S. Patent
`
`Apr.27, 2004
`
`Sheet 5 of6
`
`US 6,728,520 B2
`
`
`
`504
`
`
`
`
`508
`CONTROL VOLTAGE AMPLIFIER RECEIVES
`LOG AMPLIFIER OUTPUT (dBm) AND HAND
`HELD DEVICE CONTROL VOLTAGE(dBm)
`
`510
`
`POWER DETECTOR DETERMINES THE
`CURRENT TRANSMIT POWER LEVEL
`
`
`(VOLTAGE)
`506
`
`
`LOG AMPLIFIER RECEIVES POWER
`CONVERTSIT TO dBm
`
`DETECTOR OUTPUT (VOLTAGE) AND
`
`
`
`
`
`
`
`AMPLIFIER OUTPUT
`=
`
`EQUAL TO HAND HELD DEVICE
`CONTROL VOLTAGE
`
` NO
`
`514
`CONTROL VOLTAGE AMPLIFIER CONVERTS
`LOG AMPLIFIER OUTPUT (dBm) TO VOLTAGE
`516
`
`
`GAIN CONTROL AMPLIFIER RECEIVES
`
`
`CONTROL VOLTAGE AMPLIFIER OUTPUT
`
`
`(VOLTAGE), ADJUSTSIT, AND CONVERTS
`
`IT TO dBm
`
`
`518
`
`FILTER RECEIVES GAIN CONTROL
`AMPLIFIER OUTPUT(dBm)
`
`POWER AMPLIFIER RECEIVES FILTER OUTPUT
`(dBm) AND CONVERTSIT TO VOLTAGE
`
`520
`
`
`
`
`
`
`POWER DETECTOR RECEIVES POWER
`AMPLIFIER OUTPUT (VOLTAGE)
`
`POWER DETECTORSETSITS OUTPUT TO
`POWER AMPLIFIER OUTPUT
`
`522
`
`524
`
`FIG. 5
`
`
`
`6
`
`

`

`U.S. Patent
`
`Apr. 27, 2004
`
`Sheet 6 of 6
`
`US6,728,520 B2
`
`
`
`
` VOLTAGE AMPLIFIER
`OUTPUT LESS THAN
`
`
`
`
`
`
`DECREASE TRANSMIT
`POWER LEVEL
`
`INCREASE TRANSMIT
`POWER LEVEL
`
`FIG. 6
`
`7
`
`

`

`US 6,728,520 B2
`
`1
`SYSTEM AND METHOD FOR CONSTANT
`LOOP GAIN IN A CLOSED LOOP CIRCUIT
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is related to commonly-owned
`applications, filed concurrently herewith, entitled “Power
`Output Control Of A Car Kit By A Coupled Wireless
`Device” having application Ser. No. 09/387,143; “System
`And Method For Temperature Compensation Of Wireless
`Antenna Units” having application Ser. No. 09/387,138; and
`“System And Method For Power Measurement In Outdoor
`Antenna Units” having application Ser. No. 09/387,139,
`which are incorporated herein by reference.
`
`10
`
`15
`
`BACKGROUND OF THE INVENTION
`
`I. Field of the Invention
`
`The present invention relates generally to mobile tele-
`phone systems, and more particularly to a system and
`method for control of the output power for an outdoor unit
`coupled to a wireless device transferring an information
`signal, through the use of a closed loop circuit. The present
`invention is most applicable to wireless communications
`devices used in communication systems using code division
`multiple access (CDMA) modulation techniques, where
`output power controlis critical.
`II. Related Art
`
`Mobile telephone systems allow customers to establish
`communication links or place telephone calls from wireless
`devices such as portable or hand held mobile phones. Calls
`initiated or
`received by wireless devices used in such
`systems are processed by a wireless network. One type of
`wireless network is a terrestrial cellular communication
`system communicating via a series of base stations and
`ground-based antennas that operate in the 800-1900 MHz
`range. Cellular communication systems limit the user to
`communication within a cell, which comprises a geographi-
`cal service area to which the base station antennas can
`transmit. Users can move from cell to cell through known
`hand-off procedures that transfer calls from one cell
`to
`another. Ilowever, if no base station is within range of the
`mobile transmitter, such as in a rural area, a user cannot use
`the mobile telephone service.
`Developments in mobile telephone system technology
`have led to wireless communication systems or networks
`that can transfer signals using a Low Earth Orbit (LEO)
`satellite system. The satellite systems can transmit and
`receive signals in rural areas as well as cities through the
`beamsthey project, and a user does not need to be within
`close range of a ground-based antenna. As a result, satellite
`communication systemsare not limited to majorcities as are
`cellular networks. In addition, each LEOsatellite is capable
`of carrying a large number of user transmissions simulta-
`neously. Various satellite access schemes such as time
`division multiple access (TDMA)and codedivision multiple
`acecss (CDMA)allow concurrent access to LEOsatcllitcs
`by a large numberofusers.
`The number of users that can be serviced by a wireless
`communication system, the system capacity, increases if the
`poweroutput from each user’s wireless device is decreased
`to the minimum powerneeded for quality transmission, and
`overhead or oon-traffic messages or channel activity is
`reduced. This is the result of decreasing mutual interference
`between users, which is especially important
`in limited
`power environments such as CDMA type communication
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`systems. However, if the power of a user’s signal becomes
`too low, the quality of service for that user becomes unac-
`ceptable. So, there is a desire to maintain as high a power
`level as possible to have higher quality service.
`Thus, the numberof users that may be provided serviceis
`increased by maintaining overhead power levels and each
`individual user’s signals at the minimum levels needed for
`optimum performance. Therefore, the power output of wirc-
`less device transmissions are generally controlled using one
`or more powercontrol methods to minimize interference and
`maximize communication link quality. Techniques for
`powercontrol are discussed for example in U.S. Pat. No.
`5,383,219, entitled “Fast Forward Link Power Control In A
`Code Division Multiple Access System,” issued Jan. 17,
`1995; U.S. Pat. No. 5,396,516, entilled “Method And Sys-
`tem For The Dynamic Modification Of Control Parameters
`In A Transmitter Power Control System,” issued Mar. 7,
`1995; and US. Pat. No. 5,267,262, entitled “Transmitter
`Power Control System,” issued Nov. 30, 1993, which are
`incorporated herein by reference. In addition, also see U.S.
`patent application Ser. No. 09/164,384 filed Sep. 30, 1998
`entitled “System And Method For Optimized Power Con-
`trol”; and Ser. No. 08/908,528, filed Aug. 7, 1997, entitled
`“Method And Apparatus or Adaptive Closed Loop Power
`Using Open Loop Measurements,” which are incorporated
`herein by reference. The result is the communication system
`efficiently carries the substantially maximum number of
`individual user transmissions simultaneously.
`Wireless devices, also referred to as user terminals, in
`current wireless communications systems may be any of
`several different types. One type is the portable unit, which
`is a hand held device carried by the user and requires no
`external power source or antcnna system. Another type is the
`mobile unit or station, which is typically fixed in a vehicle
`and operates like a desk type phone. A mobile unit has a
`separate unit (or “box”) that is mounted in the vehicle and
`contains most of the transmitting and receiving circuits or
`hardware. A hand held unit such as a phone handset,
`containing a keypad, speaker and microphone,is connected
`by one or more cables, conductors, or connectors to the box.
`Acradle is provided for supporting the handset unit whenit
`is not in operation or is being used in a “hands free” mode.
`The box in turn is connected by a cable to an externally
`mounted “outdoor” antenna unit, which transmits and
`receives signals via a satellite or terrestrial cellular commu-
`nications system or a base station or gateway.
`A third type of user terminal combinesthe features of both
`a portable unit and a mobile unit. This type uses a hand held
`device that can be used as a standalone unit away from the
`vehicle, and can be connected to a vehicle mounted assem-
`bly sometimes called a “car kit,” for use in the vehicle. The
`car kit uses an external or outdoor unit (ODU) with an
`outdoor antenna to accommodate communications for the
`wireless device. A primary advantage of this combination
`unit or arrangement is that when the wireless device is used
`in the vehicle it can utilize additional power provided bythe
`vehicle mounted electronics to establish a better and stron-
`
`ger communications link with satellite transceivers. It also
`allows conservation of internal battery power, drawing on
`vehicle provided power instead.
`Satellite telephone systems are particularly sensitive to
`outdoor or external antenna unit matching at the mobile unit
`due to potential path losses and a resulting difficulty in
`powercontrol. For optimumperformance, the power output
`of the outdoor unit must be calibrated against, or configured
`with, specific phone transmission circuits in mind. At
`present, a given car-kit is designed in the factory to function
`
`8
`
`

`

`US 6,728,520 B2
`
`3
`with certain characteristics for phones with whichit is to be
`connected. Once this designing or matching takes place, the
`autonomous nature of phones and car kits is diminished
`because the phone is limited to being used with certain car
`kits or outdoor antenna units, such as specific models or
`manufacturers, having closely matched characteristics.
`This clearly sets certain constraints for mobile units or
`hand held phones used with car kits in order to provide a
`closer match between the poweroutput desired by the phone
`powercontrol systems or methods, and the poweractually
`being delivered by the outdoor unit. Yet,
`in the actual
`marketplace it is not uncommonthat a user may have more
`than one portable phone or have one that can be used both
`as a standalone unit and as a mobile phone whenplaced in
`a cradle mounted in a vehicle. Also, a user may commonly
`upgrade his or her phone as new models come on the market.
`Therefore, the mobile unit employed with a car kit may
`change permanently or on a transient basis, creating poten-
`tial undesirable power matching problems.
`One goal of the present invention is to allow a variety of
`hand held wireless devices to be used with a given vehicle
`mounted outdoor antenna unit or car-kit, while maintaining
`a desired level of accuracy for the power output by the
`outdoor unit. Here, a given outdoor antenna unit is not
`calibrated against specific hand held device characteristics,
`but allowed to adjust in response to changing characteristics
`or power requirements for a device to whichit is coupled.
`For improved or optimum performance, the outdoor antenna
`unit and the hand held wireless device connectedto it need
`to communicate transmit power levels and requirements.
`Whatis needed is a system and methodfor the hand held
`device to inform the outdoor unit of the transmit powerlevel
`to produce or use in transferring signals, using a control
`voltage or signal. Further, what is needed is a system and
`method for allowing the outdoor unit to adjust its transmit
`powerlevel based on the control voltage.
`SUMMARYOF THE INVENTION
`
`The present invention is a system and method for con-
`trolling transmit powerlevel of an information signal trans-
`mitted by an outdoor antenna unit which is used with a
`cradle or receptacle for coupling to a hand held, or holdable
`(portable), wireless communication device originating the
`information signal being controlled. With the present
`invention, transmit powerlevel is controlled by transmitting
`a control voltage from a hand held device to the outdoor
`antenna unit (also referred to as an outdoor unit, or ODU)
`and then allowing the outdoor unit to adjust its transmit
`powerlevel via a closed loop circuit. Because the hand held
`device informs the outdoor unit of the transmit powerlevel
`to produce, the present invention allows a varicty of hand
`held wireless devices to work with manydifferent outdoor
`units while maintaining appropriate power output levels.
`The system of the present invention includes a logic unit
`in the hand held device for determining an appropriate
`transmit power for transmission of the information signal
`and for producing a control voltage, a closed loop circuit in
`the outdoor unit for receiving the control voltage from the
`logic unit and for adjusting the transmit powerlevel of the
`information signal based on the control voltage using a
`substantially constant loop gain. The logic unit determines
`the control voltage based on the data rate for the signal being
`transmitted.
`
`The closed loop circuit of the present invention includes
`a powerdetector for detecting the transmit powerlevel of the
`outdoor unit, a log amplifier that converts the output of the
`
`10
`
`15
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`power detector to a digital format, a control voltage ampli-
`fier that determines whetherthe log amplifier output is equal
`to the control voltage and then,if necessary, converts the log
`amplifier output to a voltage format, a gain control amplifier
`that adjusts the output of the control voltage amplifier and
`converts it to a digital format, a filter that filters the output
`of the gain control amplifier, and a power amplificr that
`converts the output of the filter to a voltage format to
`produce the new input for the power detector. The present
`invention also provides for a ROM look-up table that
`replaces the log amplifier. The closed loop circuit of the
`present invention maintains a substantially constant loop
`gain.
`The method of the present invention includes detecting
`the transmit power level of the outdoor unit, determining
`whether the transmit power level is equal to the control
`voltage, and adjusting the transmit powerlevel based on the
`control voltage if the transmit powerlevelis not equal to the
`control voltage.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The features, objects and advantages of the present inven-
`tion will become more apparent from the detailed descrip-
`tion set forth below when taken in conjunction with the
`drawings in which like reference characters identify corre-
`spondingly throughout and wherein:
`FIG. 1 is a block diagram of a mobile phone system
`according to a preferred embodiment of the present inven-
`tion;
`FIGS. 2a, 2b, and 2c are graphs of power versus voltage
`illustrating the output function for a power detector, a log
`amplifier, and a resulting combined linear function;
`FIGS. 2d and 2e are graphs of power versus voltage
`illustrating loop stability at lower and higher powerlevels,
`respectively;
`FIG. 3 is a block diagram of a car kit according to a
`preferred embodiment of the present invention;
`FIG. 4 is a flowchart illustrating the use of a car kit for
`transferring signals according to a preferred embodiment of
`the present invention;
`FIG. 5 is a flowchartillustrating the operation of a closed
`loop circuit of an ODUto adjust transmission powerlevels
`according to a preferred embodiment of the present inven-
`tion; and
`FIG. 6 is a flowchart illustrating the operation of a gain
`control amplifier to adjust the ODU transmit power level
`according to a preferred embodiment of the present inven-
`tion.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`With the system and method of the present invention, a
`hand held wireless device informs an external or outdoor
`antenna unit of the transmit power level to produce. This
`information is passed from the hand held device to the
`antenna unit by a constant output of control voltage. Based
`on the current control voltage level, the outdoor antenna unit
`adjusts its transmit power level used for transfer of an
`information signal through the use of a closed loop circuit.
`One embodiment of the present invention is in a car kit
`that comprises an external antenna unit, also referred to as
`an outdoor unit or ODU, that mounts to the exterior of a
`vehicle, such as the trunk or roof of a car or truck and a
`cradle. A hand held device interfaces with the car kit to make
`and receive calls or establish communication links. The car
`
`9
`
`

`

`US 6,728,520 B2
`
`10
`
`15
`
`5
`kit operates in a wireless satellite communications system,
`preferably one that uses Low Earth Orbit (LEO)satellites.
`However, it would be apparent to one skilled in the relevant
`arts that other satellite systems, such as ones using Medium
`Earth Orbit (MEO) satellites, or geosynchronous (GEO)
`satellites, could also be used with this invention. The inven-
`tion may also prove uscful in someterrestrial communica-
`tion systems where car kit power losses or differences
`unacceptably effect the control of output power.
`FIG. 1 is a block diagram of an exemplary wireless
`mobile phone system 102, in which the present invention
`may be used. Such communication systemsare discussed in
`U.S. Pat. No. 4,901,307,
`issued Feb. 13, 1990, entitled
`“Spread Spectrum Multiple Access Communication System
`Using Satellite or Terrestrial Repeaters;” U.S. Pat. No.
`5,691,974, which issued Nov. 25, 1997, entitled “Method
`and Apparatus for Using Full Spectrum Transmitted Power
`in a Spread Spectrum Communication System for Tracking
`Individual Recipient Phase Time and Energy;” and USS.
`patent application Ser. No. 09/120,859 filed Jul. 21, 1998,
`entitled “System And Method For Reducing Call Dropping
`Rates In A Multi-Beam Communication System,” all of
`which are assigned to the assignee of the present invention,
`and are incorporated herein by reference.
`Mobile phone system 102 comprises one or more hand
`held wireless devices 110 communicating with a wireless
`communications system or network 128 comprising equip-
`ment related to wireless communication service. Wireless
`
`device 110 is mountedin or coupled to a car kit 104. Car kit
`104 is mounted in a vehicle, such as an automobile or truck,
`106, although other locations are possible. Car kit 104
`includes a cradle 108, a cable 111, an outdoor unit (ODU)
`112, and an ODU antenna 114. Hand held device 110 can
`rest in or be removed fromcradle 108. It is anticipated and
`will be readily understood by those skilledin the art, that the
`“car kit” and ODUrepresent elements that can be used in
`non-vehicular arrangements as well, such asforfixed remote
`communication applications in or around structures where
`unit mobility is occasionally exploited or increased poweris
`sometimes desired.
`
`Hand held device 110 has two modes of operation, as a
`standalone unit and as a hand set plugged into cradle 108.
`When hand held device 110 operates as a standaloneunit, it
`transmits and receivesvia satellite 116 using an antenna(not
`shown)built into or manufactured as part of the hand held
`device. When hand held device 110 is used within vehicle
`106 and is connected to cradle 108, it transmits and receives
`via ODU 112.
`Connection of the elements of car kit 104 will next be
`illustrated. Cradle 108 is connected to ODU 112 bycable
`111. ODU 112 mountsto an exterior surface of vehicle 106.
`
`40
`
`45
`
`50
`
`60
`
`65
`
`6
`transmits to and receives signals from an antenna 118
`connected to a ground base station, hub, or gateway 120 via
`satellite 116 providing service for an area wireless device
`110 is located in, in a manner knownto persons skilled in the
`relevant arts, and disclosed in the patents referenced above.
`A gateway provides communication links for connecting a
`wircless devicc, also referred to as a user terminal, to other
`user terminals or users of other communication systems,
`such as a public switched telephone network.
`Hand held device 110 constantly, or on a pre-selected
`periodic basis, adjusts the powerlevel of transmitted signals
`during a call or communication link depending on a number
`of know factors, one of which is the data rate. Data rate can
`change depending on the type or amountof data beingsent,
`for example, data transmitted via personal computers, digi-
`lized representation of a voice,
`facsimile data, etc.
`(connected to or forming part of wireless device 110) may
`use different rates. In addition, variable rate vocoders are
`typically used for voice communications creating different
`rates within a given communication signal. Different data
`rates require different power for transmission of that data.
`In order to allow a variety of hand held devices 110 to
`workefficiently with a variety of ODUs 112 when hand held
`device 110 is connected to cradle 108, hand held device 110
`sends information to ODU 112 indicating the required
`transmit power level ODU 112 must produce. This provides
`the ability to obtain the appropriate power output, as dis-
`cussed above,
`to maintain a quality communication link
`without excessive interference with other wireless devices
`using the communication system, and allows greater flex-
`ibility in pairing hand held devices 110 and ODU 112
`independent of the model and vendor.
`In some embodiments the initial output power for hand
`held device 110 is set arbitrarily low, such that no other
`receiver is expected to receive the signal, this assures that
`the ODUis not overpowered by the output signal, noris the
`emissions level too high. The process of the invention then
`operates to achieve an important function of setting the
`output powerto a desired (more useful) level as quickly as
`possible while conforming to any system constraints such as
`emission levels set by government agencies, or desired
`interference levels in the communication system. It is gen-
`erally undesirable to have hand held device 110 or ODU 112
`simply start at a very high power level even if that is
`ultimately what is chosen.
`With wireless device 110 in cradle 104, a call can be
`initiated by entering digits into a keypad specifying a
`particular destination number, also referred to as a telephone
`number, and then entering a send command using the
`keypad. Information is then transmitted to gateway 120
`including information used to establish, process, or termi-
`nate the call. Alternatively, a call or request for communi-
`Antenna 114 is attached to the top of ODU 112. Hand held
`cation can originate with another system user, the commu-
`device 110 may rest within cradle 108, whereby it
`is
`55
`
`clectrically connected to ODU 112 through cradle 108 nication system itsclf, or a connected network. Duringacall,
`directly, by inductive coupling, or via a wire connection in
`operation of mobile phone system 102 generally includes
`a well known manner. When a wire connection is used, hand
`sending information signals between hand held device 110,
`held device 110 may be removed from its resting position
`gateway 120, and another signal recipient, such as over a
`within cradle 108 by a userto initiate or receive a call and
`connected network through network interface device 126,
`still remain electrically connected to car kit 104. In addition,
`using the components within the wireless communications
`network 128 (as described in reference to FIG. 1 above).
`hand held device 110 may be unplugged from cradle 108 and
`taken outside vehicle 106, or other structure, for stand-alone
`The signals being transferred follow one or more stan-
`dards for communication such as the well known IS-95
`use. In that event, hand held device 110 is electrically
`disconnected from car kit 104 and does not utilize any
`features that are incorporated in car kit 104.
`Cradle 108 remains within vehicle 106 and ODU 112
`
`remains fixed to vehicle 106. Mobile phone system 102
`
`10
`
`standard for wireless communication. The gateway inter-
`prets information signals in accordance with such standards
`and respondsto the call, or switches it to other components
`within the wireless communications system. The destination
`
`10
`
`

`

`US 6,728,520 B2
`
`7
`oumber received by gateway 120 determines the switching
`that is needed to complete the call to the intended recipient,
`by the gateway or another connected network. Finally, the
`call proceeds until one of the parties terminates the call.
`Whether hand held device 110 originates or responds to a
`call, during the call, hand held device 110 adjusts the
`transmit power level of the information signals as the data
`rate changes or as the path loss or signal attenuation
`changes, in accordance with known power control tech-
`niques or algorithms, as discussed above. In addition, hand
`Powerdetector 316 detects the power within ODU 112. In
`held device 110 adjusts the transmit power level to com-
`an embodimentof the present invention, powerdetector 316
`pensate for car kit 104 losses. Because the signal must
`is implemented with a full-wave zero bias Schottky diode
`transmit through cable 111 and ODU 112 before transmitting
`via ODU antenna 114, losses result in a difference between
`detector (ZBS) such as model number HSMS2852, manu-
`factured by Hewlett Packard. Power detector 316 design
`the powerof the initial transmit signal and the power output
`from ODU 112. Hand held device 110 communicates with
`specifications include providing at
`least 25 db dynamic
`
`ODU112viaacontrol voltage indicating the transmit power range, having power estimation errors of +0.5 db from
`level wireless device 110 desires to have transmitted and,
`27-35 dBm, a power estimation time of 1 millisecond, and
`operating at temperatures of -20° C. to +60° C. ambient.
`therefore, the ODU 112 needs to generate.
`
`FIG.3is a block diagram of an exemplary car kit 104. Car The connection between the components of ODU 112 will
`kit 104 comprises componcnts used to transmit and reccive
`be described next. Duplexer 330 is connected to transmit
`via satellite 116 in order to communicate with gateway 120.
`components 326 and receive components 328 within ODU
`Car kit 104 interfaces with a hand held device 110 connected
`112. The output of transmit components 326 is connected to
`to cradle 108, which is connected to outdoor unit 112 by
`ODU antenna 114. Similar to duplexer 308 of cradle 108,
`cable 111. ODU 112transfers signals, transmit and receive
`duplexer 330 permits the connection of the ODU transmit
`through ODU antenna 114 connected to ODU 112.
`components 326 and ODU receive components 328 to a
`common antenna.
`Handheld device 110 comprises receive components 306
`and transmit components 304, also referred to as hand held
`receive and transmit components. In addition, hand held
`device 110 comprises a logic unit 302 that generates a
`substantially constant control voltage output to send to ODU
`112. Logic unit 302 comprises one or more processors that
`may have the capability of processing computer software in
`the form of lines of executable code of a computer program-
`ming languageresiding in storage medium. Processors may
`actually constitute processing capability dispersed among
`one or more processing chips, application specific integrated
`circuits (ASICs), or any other hardware capable of process-
`ing computer software. It is well known that control pro-
`cessors form part of hand held wireless devices as discussed
`in the above-referenced patents. In addition, logic unit 302
`includes or uses an associated storage medium.
`In one
`embodiment, logic unit 302 is implemented with an Intel
`386 microcomputer. The Intel 386 microcomputeris capable
`of processing many tasks whichis necessary for operation of
`hand held device 110.
`
`8
`ODU 112 comprises transmit components 326, receive
`components 328, duplexer 330, and a closed loop circuit.
`The transmit and receive components are also referred to as
`ODU transmit and receive components. The closed loop
`circuit of ODU 112 comprises a powerdetector 316, a log
`amplifier 314, control voltage amplifier 312, a gain control
`amplifier (AGC) 324,a filter 322 and a power amplificr 320.
`The closed loop circuit maintains a substantially constant
`loop gain. The components of a closed loop circuit are well
`known in the art.
`
`In the closed loop circuit of ODU 112, the output of power
`detector 316 is connected to log amplifier 314. The output
`(or voltage) of power detector 316 varies in a logarithmic
`manner or according to a logarithmic function. The loga-
`rithmic function of a power detector output is shown in FIG.
`2a which graphically depicts powerin (P,,,) versus voltage
`out (V,,,,). However,
`the function of the output of log
`amplifier 314is the inverse of the logarithmic function. The
`inverse logarithmic function of log amplifier output is shown
`in FIG. 2b which graphically depicts power in (P,,,) versus
`voltage out (V.,,,).
`A goal of the present invention is to generate a tempera-
`ture stable power detector 316 and log amplifier 314. ‘This is
`accomplished when the output of power detector 316 is
`supplied to log amplifier 314 and multiplied together. The
`result is that log amplifier 314 effectively undoes the loga-
`rithmic function of power detector 316 and producesa linear
`function, which indicates a more stable output. The lincar
`function of this multiplication process is shown in FIG. 2c
`which graphically depicts powerin (P,,,) versus voltage out
`Vout .
`Log amplifier 314 provides a dBm output level for a
`voltage input
`level. The output of log amplifier 314 is
`connected to control voltage amplifier 312, which provides
`a voltage level output in response to a dBm input. Control
`voltage amplifier 312 receives the control voltage from hand
`held device 110. The output of control voltage amplifier 312
`is connected to gain contr