United States Patent
`
`(12)
`(10) Patent N0.:
`US 7,289,775 B1
`
`King et a].
`(45) Date of Patent:
`Oct. 30, 2007
`
`US007289775B1
`
`(54) METHOD FOR TRANSMIT POWER
`CONTROL
`
`(75)
`
`Inventors: Eric J. King, Greensboro, NC (US);
`.
`.
`1:51;?“ Benedm’ Jamesmwn’ NC
`.
`,
`.
`(73) Ass1gnee. RF Micro Dev1ces, Inc., Greensboro,
`NC 023)
`.
`.
`.
`.
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 583 days.
`
`.
`( * ) Notice:
`
`(21) APP1~N0-310/382s827
`
`(22)
`
`Filed:
`
`Mar. 6 2003
`,
`
`(51)
`
`Int- 0-
`(2006.01)
`H04Q 11/12
`.
`.
`,
`.
`(200601)
`H043 ”04
`(52) US. Cl.
`..................... 455/126, 455/83, 455/127.1,
`455/115~1
`(58) Field of Classification Search .................. 455/69,
`455/522 126 517 123 127.1 95.102 108
`’
`’
`‘
`’
`’
`,
`’
`’
`455/572, 129, 127.2, 115.1,115.2, 115.3,
`455/115.4, 83, 78
`See application file for complete search history.
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`5,608,353 A
`5,629,648 A
`6,038,432 A *
`6,130,579 A
`651915656 Bl
`672297395 B1
`6’236’840 131*
`6,265,943 B1
`6,271,727 Bi
`6,285,239 B1
`6,307,364 B1
`
`3/1997 Pratt
`.......................... 330/295
`5/ 1997 Pratt
`..... 330/289
`
`3/2000 Onoda ..................... 455/127.2
`10/2000 Iyer et 31'
`------------------- 330/285
`-~ 330/288
`2’:2001 Nadler
`~~~~~
`
`" 330/252
`52001 Kay """""
`5/2001 Amara et al'
`455/83
`
`7/2001 Dening et a1.
`. 330/296
`/2001 Schmukler
`.. 330/284
`/2001 lyer et al,
`................... 327/531
`10/2001 Augustine .................... 324/95
`
`11/2001 Dening et a1.
`.............. 330/276
`6,313,705 B1
`12/2001 Dening et a1.
`.
`..... 324/95
`6,329,809 B1
`
`12/2001 Dening ....................... 330/296
`6,333,677 B1
`4302382
`153126915 ettali
`~~~~~~~~~~~~~~~ gggggg
`2,363,652 3;
`eninge a.
`.
`,
`,
`4/2002 Dening et a1.
`.
`330/296
`6,369,657 B2
`5/2002 Alexanian .....
`330/254
`6,392,487 B1
`6/2002 Dening et a1.
`.
`330/296
`6,404,287 B2
`2/2003 Dening et a].
`.
`330/298
`6,525,611 B1
`3/2003 Augustine .................... 324/95
`6,528,983 B1
`5/2003 Yan et a1.
`................... 330/311
`6,566,963 B1
`9/2004 Vakilian et a1,
`455/522
`6,795,712 B1 *
`6,801,784 B1* 10/2004 Rozenblit et a1.
`455/522
`6,868,279 B2*
`3/2005 Sahlman et al.
`455/522
`7,116,945 B2* 10/2006 Moloudi et al,
`..... 455/78
`
`
`
`.
`..
`..
`
`
`
`455/572
`.
`4/2004 Epperson et al.
`2004/0072597 A1*
`2004/0198257 A1* 10/2004 Takano et a].
`........... 455/127.1
`
`2004/0248528 A1* 12/2004 Rozenblit et a1.
`2006/0028277 A1 *
`2/2006 Yainashita et a1.
`
`........... 455/126
`.......... 330/285
`
`OTHER PUBLICATIONS
`.
`IIC.,
`0 1.1 10115,
`CIO
`.
`ll'e CSS
`ev1ces,
`2002
`l
`LAN S l t'
`” RF Mi
`D '
`“802 11b \V 1
`“RF2948B 2.4 GHz Spread-Spectrum Transceiver,” RF Micro
`Devices, lnc., Jun. 2002
`“11135117 3v, 1.8 GHz to 2.8 GHz Linear Power Amplifier,” RF
`Micro Devices, Inc., Sep. 2002.
`4
`~
`~
`c1tedb examiner
`y
`Primary ExamineriEdward F. Urban
`Assistant Examinerilohn J. Lee
`74 Altar/1e 1, A @722, 0r Firmiwithrow & Terranova.
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`(57)
`
`ABSTRACT
`
`A transceiver has power control circuitry integrated therein.
`In particular, the power control circuitry receives a signal
`indicative of the transmit power level and adjusts the gain on
`a variable gain amplifier within the transceiver such that the
`output of the transceiver is at a level from which the power
`am lifier will am 1if
`the si nal to the desired transmit
`p
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`7 Claims, 5 Drawing Sheets
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`58
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`

`U.S. Patent
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`Oct. 30, 2007
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`US 7,289,775 B1
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`U.S. Patent
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`Oct. 30, 2007
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`U.S. Patent
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`Oct. 30, 2007
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`U.S. Patent
`
`Oct. 30, 2007
`
`Sheet 5 0f 5
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`US 7,289,775 B1
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`
`
`M.0m
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`

`

`
`
`1
`METHOD FOR TRANSMIT POWER
`CONTROL
`
`FIELD OF THE INVENTION
`
`The present invention is related to controlling the output
`power of a transmitter and controlling power consumption
`associated with the transmitter at the same time.
`
`BACKGROUND OF THE INVENTION
`
`
`
`The Institute for Electrical and Electronics Engineers
`
`(IEEE) has sanctioned a wireless standard for Ethernet
`access know as 802.11. The most common application for
`this standard is in wireless modems, a though certainly other
`transmitter applications do exist. In most typical applica-
`tions, the tra 1smitter includes an antenna and transceiver
`combination that transmits at a power level that varies as a
`function of t e process and temperature. In most operating
`environments, this variation does not matter. However, in
`instances where the 802.11 transmitter is a wireless modem
`
`incorporated 'nto a laptop computer, or is otherwise battery
`powered, power consumption becomes an issue. There are
`times when applying a power control algorithm to the device
`could result i1 lower power consumption and thus prolong
`battery life. The concept of power control being applied to
`802.11 is not 16W, but has not been successfully deployed to
`date.
`
`the concept of power
`In the cel ular phone industry,
`control has seen a more robust development. Specifically,
`some standards, such as Code Division Multiple Access
`(CDMA), rely extensively on the fact that each transmitter
`
`in a cell may vary output power such that the system may
`
`
`
`operate with greater e “iciency and lower interference.
`To date, power control algorithms have been implemented
`in the integrated circuit (IC) dedicated to the baseband
`processor. The baseband processor IC is distinct from the
`transceiver IC and the power amplifier IC. To give the
`designer the most flexibility in circuit design, the three ICs
`must work in harmony. Many circuit designers do not like to
`be restricted to choosing ICs from a single vendor or
`manufacturer. As a result, for best power control options, ICs
`from multiple vendors must work in harmony. All too often,
`for competition reasons, the ICs from multiple vendors do
`not work well
`together. As a result,
`the designer may
`incorporate components external to the ICs onto the circuit
`board to facilitate cooperation between the different ICs. The
`use of external components takes up precious space on the
`circuit board, increases component counts, and otherwise
`increases costs associated with the transmitter.
`
`Thus, there remains a need for a power control mecha-
`
`nism that allows transmitter designers to simplify board
`
`
`
`
`designs while simultaneously being well suited for IE 4 4
`802.11.
`
`SUMMARY OF THE INVENTION
`
`The present invention is well suited for incorporation into
`the transmitter of a wireless modem that operates according
`to the IEEE 802.11 standard, although uses in other devices
`are also possible. Specifically, the present invention allows
`such a device to have the device’s transmit power levels
`controlled so as to increase efficiencies through reduced
`current consumption. Likewise, the present invention sim-
`plifies circuit design for the circuit designers. The circuit
`design simplification is achieved by moving the power
`control circuitry from the integrated circuit for the baseband
`
`60
`
`65
`
`US 7,289,775 B1
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`10
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`15
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`20
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`25
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`2
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`processor to the integrated circuit for the transceiver. Fur-
`ther, the present invention eliminates the need for power
`sense circuitry in the power amplifier of the transmitter. The
`placement of the power control circuitry in the transceiver
`and the elimination of the need for power sense circuitry in
`the power amplifier reduces the need for multiple compo-
`nents to work in harmony and reduces the need for extra
`components that previously helped integrated circuits work
`together.
`The present invention is positioned in a transmitter of a
`wireless device. A baseband signal passes from a baseband
`integrated circuit chip to a transceiver integrated circuit chip
`for conversion to a radio frequency signal and pre-amplifi-
`cation. The radio frequency signal passes from the trans-
`ceiver integrated circuit chip to a power amplifier which
`boosts the power level of the signal for transmission. The
`signal passes from the power amplifier to a transmit/receive
`switch and then to the antenna for transmission. The trans-
`mit/receive switch has
`some finite isolation between
`
`switches resulting in the transmitted signal leaking into the
`receiver, termed “leakage signal.” This leakage signal is
`present at the receive input of the transceiver integrated
`circuit.
`
`The transceiver integrated circuit takes the leakage signal
`present at the receive input and provides the leakage signal
`to the power control circuitry embedded in the integrated
`circuit chip of the transceiver. The power control circuitry
`analyzes the leakage signal and compares the transmitted
`power level embodied by the leakage signal to a desired
`transmit power level. The desired transmit power level may
`be provided by a local controller or by a remote base station.
`The power control circuitry then outputs a signal
`that
`controls a variable amplifier in the transmit path of the
`transceiver integrated circuit so as to control the signal that
`is presented to the input of the power amplifier. The deter-
`mination of the control signal may be made through a look
`up table or the like based on the results of the comparison.
`The change in the amount of amplification at the variable
`amplifier in turn affects the power level at the output of the
`power amplifier and thus the power level that is present at
`the switch to create the leakage signal. This feedback loop
`enables the power level being transmitted from the antenna
`to be controlled by the transceiver integrated circuit rather
`than the baseband processor integrated circuit.
`In an alternate embodiment, the power control circuitry
`produces a bias signal that is provided to a bias control input
`of the power amplifier. This further controls the power level
`at the output of the power amplifier. However, not every
`power amplifier has this bias control input, so this is an
`optional feature.
`In a second alternate embodiment, the transceiver inte-
`grated circuit receives the transmitted power level from the
`power sense circuitry of the power amplifier. Because not
`every power amplifier includes the power sense circuitry and
`because not every manufacturer’s power sense circuitry
`works the same, this is an optional feature.
`Those skilled in the art will appreciate the scope of the
`present invention and realize additional aspects thereof after
`reading the following detailed description of the preferred
`embodiments in association with the accompanying drawing
`figures.
`
`
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The accompanying drawing figures incorporated in and
`forming a part of this specification illustrate several aspects
`
`

`

`US 7,289,775 B1
`
`3
`of the invention, and together with the description serve to
`explain the principles of the invention.
`FIG. 1 illustrates a conventional laptop computer con-
`nected to the Internet via a 802.11 connection;
`FIG. 2 illustrates a schematic diagram of a conventional
`transmitter associated with a wireless device;
`FIG. 3 illustrates a schematic drawing of one embodiment
`of the power amplifier and transceiver interrelation;
`FIG. 4 illustrates a schematic drawing of an embodiment
`of the internal circuitry of the transceiver integrated circuit;
`and
`
`FIG. 5 illustrates a block diagram of a portion of the
`functions of the digital circtitry that may be used with the
`present invention.
`
`
`DETAII a D D a SCRIPTION OF TH:
`
`
`
`PR 4 F A RRED a MBODIMENTS
`
`
`
`
`5
`
`10
`
`15
`
`LU
`
`
`
`The embodiments set forth below represent t e necessary
`information to enable those skilled in the art to practice the 20
`invention and illustrate the best mode of practicing the
`invention. Upon reading the following description in light of
`the accompanying drawing figures, those skilled in the art
`will understand the concepts of the invention and will
`recognize applications of these concepts not particularly 25
`addressed herein. It should be understood that these con-
`
`
`
`cepts and applications fall within the scope of the disclosure
`and the accompanying claims.
`Laptop computers such as laptop 10 in FIG. 1 are becom-
`ing more prevalent with each passing day. Laptop 10 may 30
`have a keyboard 12, a display 14, a disk drive 16, and other
`input/output devices as is well understood. An exemplary
`laptop 10 may be the T23 THINKPAD solc by IBM. The
`T23 and other laptops include wireless moc ems that have
`antennas 18 that communicate wirelessly to a wirebased 35
`
`
`
`modem 20 through such standards as 1% 4 802.11. The
`wirebased modem 20 may be a cable modem or the like and
`may incorporate a hub (not shown) with an antenna 22 that
`receives the wireless signals from the laptop 10. The wire-
`based modein 20 comiects to the Internet 24 as is well 40
`understood. By providing the laptop 10 with the wireless
`modem and antenna 18, the designers allow users of the
`laptop 10 to improve the mobility and versatility of the
`laptop 10.
`The laptop 10 contains a transmitter 26 that culminates in 45
`antenna 18 as illustrated in FIG. 2. Laptop 10 also has a
`control system 28, which may be a microprocessor and
`associated operating system and the like as is well under-
`stood. Control system 28 is associated with an I/O interface
`30 to receive inputs from a user and generate outputs for the 50
`user. For example, the I/O interface 30 may cooperate with
`the keyboard 12 and the display 14 as is well understood.
`Transmitter 26 includes baseband processor integrated
`circuit 32, transceiver integrated circuit 34, power amplifier
`36, switch 38, and the antenna 18. During operation, the 55
`laptop 10 may generate a signal to be transmitted. This
`signal may be an internet protocol (IP) packet, a voice
`signal, or the like. The signal is generated typically by the
`control system 28 which passes the signal to the baseband
`processor integrated circuit 32 for initial processing. This 60
`initial processing may encode the signal for transmission.
`The baseband processor integrated circuit 32 manipulates
`the signal at baseband frequencies and passes the signal to
`the transceiver integrated circuit 34. The transceiver inte-
`grated circuit 34 converts the signal to a radio frequency 65
`(RF) signal and may perform initial amplification. After
`frequency conversion,
`the signal
`is passed to the power
`
`4
`
`amplifier 36 which boosts the power level of the signal to a
`desired level suitable for transmission. The boosted signal is
`passed through the switch 38 to the antenna 18 where the
`signal
`is transmitted to the antenna 22 of the wirebased
`modem 20 or other device.
`
`It should be appreciated that the transmitter 26 may also
`share components with the receiver (not shown explicitly).
`Specifically, an incoming signal may be received by the
`antenna 18 and pass through the switch 38 to the transceiver
`integrated circuit 34. The transceiver integrated circuit 34
`converts the incoming radio frequency signal to a baseband
`signal and passes the baseband signal
`to the baseband
`processor integrated circuit 32 for further processing.
`In this typical arrangement of the transmitter 26, power
`control circuitry 40 is integrated into the baseband processor
`integrated circuit 32. The power control circuitry 40 controls
`the power level of the signal provided to the transceiver
`integrated circuit 34 and potentially controls a bias signal
`that is applied to the power amplifier 36. In return, the power
`amplifier 36 may send a power sensed signal to the baseband
`processor integrated circuit 32. The power sensed signal is
`standard on the RF 5117, sold by RF Micro Devices, Inc. of
`Greensboro, NC, and generally understood in the art.
`It should further be appreciated that the baseband proces-
`sor integrated circuit 32 and the transceiver integrated circuit
`34 are separate integrated circuit chips. As such, they may be
`positioned on the same circuit board, but are distinct entities
`within the laptop 10. It is also worth noting that the power
`control circuitry 40 may receive instructions on how to
`control the power from the control system 28. These instruc-
`tions may be generated by the control system 28 or received
`from a remote location such as a cellular base station. For
`
`the base stations provide
`in a CDMA system,
`example,
`instructions to the cellular phones with precise power levels
`at which the cellular phones are to transmit. The instructions
`are embedded in the communications from the base station
`
`as is well understood in the industry.
`The present invention takes a wireless device such as the
`transmitter 26 in the lap op 10, a cellular phone, a personal
`
`digital assistant with a wire ess transmitter, or similar device
`operating according to I4 A 4 802.11, CDMA, or other com-
`munication protocol and provides a technique to provide
`power control thereto in such a manner that circuit design is
`simplified and power efficiencies are achieved. Collectively
`such devices are termec
`erein “mobile terminals.” In the
`
`
`
`
`
`
`exemplary embodiment, the wireless device will continue to
`
`be a wireless modem in a laptop 10 operating according to
`
`IE A A 802.1], but the teachings of the present invention are
`
`no limited to this standard or such a device. Those of
`in the art will recognize that alternative
`ordi ary skill
`devices and protocols may also benefit from the use of the
`present invention.
`T e present invention achieves design simplification and
`power control efficiencies by moving the power control
`circuitry 40 from the baseband processor integrated circuit
`32 to the transceiver integrated circuit 34. This is illustrated
`schematically in FIG. 3. Specifically, a transceiver inte-
`grated circuit 34A contains, within the integrated circuit
`chip, transmit circuitry 42, receive circuitry 44, and power
`control circuitry 46. The transceiver integrated circuit 34A
`further includes outputs such as RFOUT 48 and PABIAS 50
`as well as a receive input RFIN 52 and a baseband input LFIN
`54. The inputs and outputs may be pins or contact pads as is
`conventional in the integrated circuit industry.
`The input LFIN 54 receives the baseband signal from the
`baseband processor integrated circuit 32 and provides the
`signal to the transmit circuitry 42 for frequency conversion
`
`

`

`US 7,289,775 B1
`
`5
`
`5
`and amplification. The power control circuitry 46 controls
`how much amplification is provided to the signal. Once
`converted and amplified, the signal, depicted as signal 56, is
`output at RF OUT 48. Signal 58 may also be generated by the
`power circuitry 46 as a bias control signal and is output at
`the output PABIAS 50. The signal 56 and the signal 58
`together are provided to the power amplifier 36. Note that
`signal 58 and the output PABIAS 50 of the transceiver
`integrated circuit 34A are optional features and need not be
`included for the present invention to work. A more detailed 10
`explanation of controlling the bias circuitry of a power
`amplifier to control current consumption can be found in
`commonly owned US. Pat. No. 6,333,677, which is hereby
`incorporated by reference.
`Signals 56 and 58 are presented to inputs 60 and 62,
`respectively, of the power amplifier 36. Input 60 receives an
`RF signal and thus is also labeled RF1N input 60. Input 62
`receives a bias control signal and may not be present on
`every power amplifier 36. The power amplifier 36 amplifies
`the signal 56. The amplified signal, labeled 64 in FIG. 3, is 20
`output at RFOUT output 66. Signal 64 is passed to the switch
`38 and then to the antenna 18. Some portion of the signal 64
`leaks from the transmit path to the receive path in the switch
`38 because there is limited isolation between the elements of
`
`15
`
`6
`desired power level may be generated by the control system
`28 or from a base station or other location as is well
`
`
`
`
`understood. An offset may additionally be stored in an 0 “set
`memory device 78. This offset may be applied to the desired
`signal level or the digitized version of leakage signal 68 as
`needed or desired. The offset may compensate for attenua-
`tion at the switch 38 or other factors that cause leakage
`signal 68 to be changed from the actual power level trans-
`mitted by the antenna 18.
`Based on the comparison of the digitized leakage signal
`68 and the desired transmit power level, as affected by the
`offset stored in ofiset memory device 78 (if any), one or
`more control signals may be generated. These control sig-
`nals may be determined by reference to a look up table or the
`like based on the comparison. The primary control signal is
`designed to control the gain of a variable gain amplifier 80.
`The secondary control signal is optional and is the bias
`signal 58 (FIG. 3).
`to
`is directed to a digital
`The primary control signal
`analog (D/A) converter 82 and then used to control the
`variable gain amplifier 80. The secondary control signal is
`also directed to a second D/A converter 84 before being
`output at PABIAS 50.
`The signal that comes from the baseband processor inte-
`grated circuit 32 arrives at the input LFIN 54 (FIG. 3) and is
`directed to the variable gain amplifier 80, where the signal
`is amplified according to the settings of the variable gain
`amplifier 80. The amplified signal
`is then passed to an
`upconverting mixer 86 to modulate the signal onto a radio
`frequency (RF) signal as is well understood. The RF signal
`is then amplified again by a preamplifier 88 and output at
`RFOUT 48 as signal 56 (FIG. 3).
`Note that the order of upconverting the mixer 86, the
`variable gain amplifier 80, and the preamplifier 88 may be
`rearranged without departing from the present invention.
`By controlling the variable gain amplifier 80, the power
`control circuitry 46 controls the power level of the signal 56.
`By controlling the power level of the signal 56 before
`introduction into the power amplifier 36, the signal gener-
`ated by the power amplifier 36 is controlled and thus the
`power level of the transmitted signal
`is controlled. This
`feedback loop effectively brings the transmitted power level
`to the desired transmit power level.
`For power amplifiers 36 that have a bias signal input, such
`as the aforementioned RF 5117, the control may be further
`refined by using the bias signal 58. However, not every
`power amplifier 36 has a bias input, and thus, the use of the
`bias signal 58 is optional. Where there is a bias input on the
`power amplifier 36, current consumption may be reduced,
`prolonging battery life if needed or desired.
`In an alternate embodiment, not
`illustrated, a signal
`indicative of the transmitted power may be provided directly
`by the power amplifier 36. For example, the RF 5117 has a
`power sense output pin that provides a signal indicative of
`the output power of the power amplifier 36. If this power
`sense signal
`is present,
`the power sense signal may be
`provided to the power control circuitry 46 without the need
`for rectification. However, not every power amplifier 36 has
`this sort of output, so such a technique for conveying the
`output power level transmitted is optional. Further, because
`not every manufacturer provides the same sort of power
`sense signal,
`it may be easier for the circuit designer to
`ignore the existence of such a signal and rely on the leakage
`signal 68. Reliance on the leakage signal 68 in fact elimi-
`nates the need for the power sense output from the power
`
`the switch 38. This leakage is labeled leakage signal 68.
`Leakage signal 68 is thus an indication of the power level
`transmitted by the antenna 18. Leakage signal 68 may not
`exactly reflect the power level transmitted by the antenna 18
`due to attenuation caused by the leaking at the switch 38 or
`other factors, but will be proportional to the transmitted 30
`power level.
`The leakage signal 68 is made available to the RFIN input
`52 on the transceiver integrated circuit 34A. Nomlally,
`signals that are present at RF1N input 52 would be presented
`to the receive circuitry 44, but when the transmitter is in the 35
`transmit mode, any signal present at RFIN input 52 is
`presented to the power control circuitry 46. This may be
`accomplished by a switch 70 (FIG. 4) within the transceiver
`integrated circuit 34A or other conventional signal routing
`technique.
`Greater details about the workings of the transceiver
`integrated circuit 34A are illustrated in FIG. 4. As noted
`above, a switch 70 or other signal routing device determines
`which way signals present at RFIN input 52 are routed. The
`switch 70 may direct a signal at RFby input 52 to the receive 45
`circuitry 44 if the transmitter 26 is in the receive mode. The
`‘eceive circuitry 44 downconverts the received signal to a
`lower frequency and digitizes the signal before passing the
`‘eceived signal to the baseband processor integrated circui
`32. The baseband processor integrated circuit 32 processes 50
`he digitized received signal to extract the information 0‘
`data bits conveyed in the received signal. This processing
`ypically comprises demodulation, decoding, and error cor
`‘ection operations.
`Altematively, and more importantly for the purposes 0
`he present invention, the switch 70 may direct the leakage
`signal 68 to the power control circuitry 46. Within the powe ‘
`control circuitry 46, the leakage signal 68 is initially rectified
`3y a rectifier 72. Note that a filter (not shown) may be used
`in conjunction with the rectifier if needed or desired. Othe‘ 6O
`‘ectifying circuitry is usable, and the term “rectifier” is used
`erein to cover analogous circuits. The rectified signal is
`oassed to an analog to digital
`(A/D) converter 74 f0‘
`conversion to a digital signal. The digital signal is passed
`from the A/D converter 74 to digital circuitry 76. The digital
`circuitry 76 compares the signal from the A/D converter 74
`o a predetermined desired power level. This predetermined
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`US 7,289,775 B1
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`amplifier 36 and thus allows circuit designers to eliminate
`the power sense circuitry from the power amplifier 36 if
`needed or desired.
`
`While the present invention is well suited to provide a
`feedback loop passing through the transceiver integrated
`circuit 34A rather than the baseband processor integrated
`circuit 32, an initial setting on the variable gain amplifier 80
`must also be chosen to start the process. This is accom-
`plished by using the look up table when the transceiver
`integrated circuit 34A switches from receive mode to trans-
`mit mode. At the time of the switch, the control system 28
`sends a signal to the digital circuitry 76 with the desired
`output power level. The digital circuitry 76 uses the look up
`table to determine an appropriate setting for the variable
`gain amplifier 80 to achieve an output proximate the desired
`value. Specifically, the look up table may provide a value for
`a control signal. This control signal is sent to the variable
`gain amplifier 80 immediately prior to the arrival of the
`signal to be transmitted, and processing continues as indi-
`cated above.
`
`The look up table may be derived from empirical testing
`or other calibration routine as needed or desired. Alterna-
`
`tively, the initial condition can be based on past measure-
`ments of the desired power and the last output gain setting
`that achieved that desired power. Thus, if the new desired
`power corresponds to the last used desired power, the table
`may have stored the setting that achieved that desired power.
`FIG. 5 illustrates the internal workings of a portion of the
`digital circuitry 76. The output of the A/D converter 74 is
`subtracted from the desired value by an adder 90. The
`subtraction value tells the digital circuitry 76 how far the
`desired transmit power is removed from the actual transmit
`power. This value is sent through a gain block 92 to add or
`subtract to the current setting. Additionally, the output of the
`gain block 92 is sent through an integrator 94. It should be
`appreciated that there are many ways that this series of
`functions could be implemented, and the present invention
`is not restricted to a particular format thereof
`Those skilled in the art will recognize improvements and
`modifications to the preferred embodiments of the present
`invention. All such improvements and modifications are
`considered within the scope of the concepts disclosed herein
`and the claims that follow.
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`What is claimed is:
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`1. A method of controlling power transmitted from an
`antenna, comprising:
`sensing the power transmitted from the antenna, wherein
`sensing the power transmitted from the antenna com-
`prises sensing a power level in a leakage signal from a
`switch;
`determining a desired level for the power transmitted
`from the antenna;
`comparing, in digital circuitry incorporated into a trans-
`ceiver integrated circuit, the power transmitted from
`the antemla to the desired level;
`generating, in the digital circuitry, a control signal; and
`controlling a variable gain amplifier within the transceiver
`integrated circuit with the control signal, wherein the
`variable gain amplifier amplifies a transmit signal
`within the transceiver integrated circuit, such that the
`power transmitted from the antenna approaches the
`desired level.
`
`2. The method of claim 1 wherein sensing the power
`transmitted from the antenna comprises rectifying a signal
`indicative of the power transmitted from the antenna to
`create an analog rectified signal.
`3. The method of claim 1 wherein sensing the power
`transmitted from the antenna further comprises converting
`the analog rectified signal to a digital signal.
`in the
`4. The method of claim 1 wherein generating,
`digital circuitry, a control signal comprises generating a
`digital control signal.
`5. The method of claim 4 further comprising converting
`the digital control signal to an analog signal to control the
`variable gain amplifier within the transceiver integrated
`circuit.
`
`6. The method of claim 1 fiirther comprising generating,
`in the digital circuitry, a bias signal to control a bias level of
`a power amplifier.
`7. The method of claim 1 comprising forwarding the
`transmit signal to a power amplifier associated with the
`antenna, wherein the power amplifier is distinct from the
`transceiver integrated circuit.
`
`