US 6,717,981 B1
`(10) Patent N0.:
`(12) United States Patent
`
`Mohindra Apr. 6, 2004 (45) Date of Patent:
`
`
`USOO6717981B1
`
`(54) TRANSMITTER IMAGE SUPPRESSION IN
`TDD TRANSCEIVERS
`
`OTHER PUBLICATIONS
`
`.
`.
`_
`_
`_
`Inventor: Rishi M0hindra, Milpitas, CA (US)
`(75)
`(73) Assignee: Koninklijke Philips Electronics N.V.,
`Eindhoven (NL)
`
`Patent Abstract of Japan Publication No.: 10242765A, Date
`of Publication Sep. 11, 1998.
`.
`.
`* Cited by examiner
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/460,929
`(22)
`Filed:
`Dec. 14, 1999
`
`Int. Cl.7 .................................................. H04B 1/38
`(51)
`
`(52) US, Cl,
`......
`375/219; 455/78; 455/83;
`455/69
`(58) Field of Search ................................. 375/219, 221,
`375/222, 259, 377, 279, 280, 281, 283;
`455/76, 78, 83, 88, 24, 69; 370/278, 280,
`282, 294
`
`(56)
`
`References Cited
`U. S. PATENT DOCUMENTS
`
`5,423,076 A
`.......... 455/86
`6/1995 Westergren et a1.
`5,446,422 A *
`8/1995 Mattila et a1.
`.............. 332/103
`
`57896562 A *
`4/1999 Heiflonen """"""" 455/76
`6’009’124 A * 12/1999 smlth et al’ ”
`375/267
`
`6,163,708 A * 12/2000 Groe ...................
`.. 455/522
`8/2001 Cummins et a1.
`ttttt 455/73
`6,278,864 B1 *
`
`6,553,018 B1 *
`4/2002 Ichihara ...............
`370/342
`................. 331/37
`6,404,293 B1 *
`6/2002 Darabi et al.
`FOREIGN PATENT DOCUMENTS
`
`.
`.
`..
`PrLmary Exammer—Young T' T56.
`(74) Attorney, Agent, or Firm—Dicran Halajian
`(57)
`ABSTRACT
`
`In a transceiver comprising a time-division-duplex (TDD) of
`transmit and receive functions,
`the characteristics of
`unwanted image signal energy being transmitted from the
`transceiver are determined, and thereafter feedback is pro-
`vided to the transmitter to reduce this unwanted image signal
`energy. The image signal energy is measured by the receiver
`component of the transceiver and fed back to the transmitter
`component of the transceiver. The transmitter component
`uses the fed back information to adjust the gain and or phase
`relationship between the quadrature signals that are subse-
`quently quadrature-phase modulated and transmitted. Avari-
`ety of techniques can be employed to allow the image signal
`energy to be measured directly by the receiver component.
`The phase modulation signals at
`the transmitter can be
`interchanged, so that the unwanted image signal energy is
`transmitted in the sideband of the intended signal.
`Alternatively the phase modulation signals at the receiver
`.
`’
`.
`,
`.
`can be interchanged, so that the receiver 5 operating fre-
`qhehcy 15 Shlhed from the frequency 0f the hahsmlher’s
`intended signal sideband t0 the frequency of the transmit-
`ter’s unwanted image signal sideband.
`
`EP
`
`0624004 A1
`
`11/1994
`
`............ H04B/1/40
`
`23 Claims, 4 Drawing Sheets
`
`
`RECEIVER
`
`’02
`
`
`LOCAL
`
`OSCILLATOR
`
`
`
`
`
`340
`
`QUADRATUHE
`SWITCH
`
`Ph GAIN
`
`TRANSMITIER
`
`
`
`‘01
`
`Page 1 of 10
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`SAMSUNG EXHIBIT 1007
`
`SAMSUNG EXHIBIT 1007
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`Page 1 of 10
`
`

`

`US. Patent
`
`Apr. 6, 2004
`
`Sheet 1 014
`
`US 6,717,981 B1
`
`
`RECEIVER
`
`102
`
`
`
`
`
` LOCAL
`OSCILLATOR
`1_2_Q
`
`TRANSMITTER
`
`PRIOR ART
`
` 210
`
`220
`
`I
`I
`I
`I
`Fc+lF
`
`230
`
`I
`I
`FM:
`
`I
`1
`Fc
`
`FIG.2
`PRIOR ART
`
`Page 2 of 10
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`Page 2 of 10
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`

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`US. Patent
`
`Apr. 6, 2004
`
`Sheet 2 0f4
`
`US 6,717,981 B1
`
`172
`
`173
`
`
`RECEIVER
`
`3111
`
`
`
`102
`
`
`
`OSCILLATOR
`
`CALIBRATE
`
`340
`
`
` g
`
`
` QUADRATURE
` Ph GAIN
`
`FEEDBACK
`DEVICE
`
`
`
`TRANSMHTER
`
`‘01
`
`Page 3 of 10
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`Page 3 of 10
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`

`

`US. Patent
`
`Apr. 6, 2004
`
`Sheet 3 0f4
`
`US 6,717,981 B1
`
`102 311
`
`
`
`
`
` LOCAL
`OSCILLATOR
`
`325
`R
`CALIBRATE
`
`0
`
`
`
`Page 4 of 10
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`Page 4 of 10
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`

`

`US. Patent
`
`Apr. 6, 2004
`
`Sheet 4 0f4
`
`US 6,717,981 B1
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`101
`
`RECEIVER
`
`319
`
`311
`
`Page 5 of 10
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`Page 5 of 10
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`

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`US 6,717,981 B1
`
`1
`TRANSMITTER IMAGE SUPPRESSION IN
`TDD TRANSCEIVERS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to the field of communications, and
`in particular to time-division-duplex (TDD) transceivers
`with a common transmit and receive frequency.
`2. Description of Related Art
`Time-division-duplex (TDD) transceivers are commonly
`used to provide two-way communications using a single
`carrier signal frequency. FIG. 1 illustrates an example block
`diagram of a conventional time-division-duplex transceiver
`100 that utilizes quadrature modulation. The transceiver 100
`includes a transmitter 130 that transforms an input data
`signal into quadrature signals TI 131 and TQ 132. A local
`oscillator 120 provides an in-phase oscillation signal 121,
`and a phase shifter 125 provides a quadrature-phase oscil-
`lation signal 122 that is 90 degrees out of phase with the
`in-phase oscillation signal 121. The quadrature signal TI 131
`is modulated, at 142, by the in-phase oscillation signal 121,
`and the quadrature signal TQ 132 is modulated, at 144, by
`the quadrature-phase oscillation signal 122. The adder 150
`combines these modulated signals to produce a composite
`signal 151.
`The transmit/receive switch 160 alternately selects the
`composite signal 151 for transmission, via an antenna 165.
`On the alternate cycle,
`the transmit/receive switch 160
`provides an input signal 161 from the antenna 165. Although
`an antenna 165 is illustrated in FIG. 1 (and FIG. 3), the use
`of other communications media, such as a wire, or cable, is
`also common in the art.
`
`The input signal 161 is a composite signal that is segre-
`gated into corresponding quadrature signals RI 173 and RQ
`175 by demodulators 172 and 174, respectively. Common in
`the art, the local oscillator 120 that is used to modulate the
`transmit quadrature signals TI and TQ is used to demodulate
`the received input signal 161 into receive quadrature signals
`RI and RQ. A number of advantages are achieved by using
`a common local oscillator 120.
`In particular,
`the local
`oscillator 120 is typically a phase-locked oscillator, and
`using the same oscillator 120 during both phases of the
`transmit/receive switch 160 eliminates the need to re-phase
`or re-synchronize the oscillator 120 with each transition.
`Additionally, the use of the same local oscillator 120 pro-
`vides a material cost savings compared to the use of a
`separate oscillator for each of the transmit and receive
`operations. The receiver 110 processes the quadrature sig-
`nals RI 173 and RQ 175 to provide an output signal 102.
`As is common in the art, the transmitter 130 provides the
`transmit quadrature signals TI 131 and TQ 132 at a prede-
`termined intermediate frequency (IF). In like manner, the
`quadrature signals RI 173 and RQ 175, being produced by
`a distant transmitter that is similar to the transmitter 130, are
`also produced at the predetermined intermediate frequency.
`The modulation 142, 144 of the quadrature signals TI 131,
`TQ 132 at
`the intermediate frequency IF with the local
`oscillation signals 121, 122 at a carrier frequency Fc results
`in two sidebands of modulation, one at Fc+IF, and the other
`at Fc—IF. Ideally, the quadrature signals TI 131 and TQ 132
`are structured such that one of the sidebands, the intended
`sideband, contains maximum power, while the other
`sideband, the “image” sideband contains minimum power.
`Due to component variations and other factors, however,
`a difference in phase or amplitude from the ideal relationship
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`between the quadrature signals TI 131 and TQ 132 can result
`in an image sideband having a considerable power content.
`FIG. 2 illustrates an example spectral power density plot of
`a convention transmitter 130 having a less-than-ideal rela-
`tionship of amplitude or phase between the quadrature
`signals TI and TQ. As illustrated, a majority of power is
`located at the intended sideband at Fc+IF, at 220, but a
`considerable amount of power is illustrated at the carrier
`frequency FC, at 210, and at the image sideband at Fc—IF, at
`230. To minimize the distortion of the demodulated intended
`signal, the transmitter or a distant receiver must filter this
`unintended and undesirable carrier and image signal power.
`As is known in the art, the cost and complexity of a filter
`process is highly dependent upon the degree of “roll-off”
`required of the filter. The selective filtering of two signals
`that are close in frequency requires a very steep roll-off, and
`therefore is more costly and complex than the selective filter
`of two signals that are widely separated in frequency. By
`implication, then, the preferred intermediate frequency IF
`should be large, because the separation between the intended
`220 and unwanted 230 signals is twice the intermediate
`frequency. However, a high intermediate frequency intro-
`duces additional costs and complexities to the components
`utilized within the transmitter 130 and receiver 110 com-
`pared to a lower intermediate frequency. Preferably,
`the
`transmitter 130 should be designed to conform as close to
`the ideal as possible, so that the degree of required filtering
`at the transmitter or distant receiver can be minimized, and
`so that a lower intermediate frequency can be utilized. The
`use of precision components and robust design techniques
`that provide for
`this idealized transmitter performance,
`however, is also a costly and complex approach.
`BRIEF SUMMARY OF THE INVENTION
`
`It is an object of this invention to provide a method and
`apparatus that minimizes the transmission of unwanted
`image frequency signals from a transceiver. It is a further
`object of this invention to provide a method and apparatus
`that minimizes the transmission of unwanted image fre-
`quency signals from a transceiver that does not require the
`use of precision components in the transceiver. It is a further
`object of this invention to provide a method and apparatus
`that minimizes the transmission of unwanted image fre-
`quency signals from a transceiver that allows for a dynamic
`adjustment of the transceiver performance to compensate for
`component variations and environmental changes.
`These objects and others are achieved by providing a
`method and apparatus for determining the characteristics of
`the image signal energy being transmitted from a transceiver
`and thereafter providing feedback to the transmitter to
`reduce this image signal energy. The image signal energy is
`measured by the receiver component of the transceiver and
`fed back to the transmitter component of the transceiver. The
`transmitter component uses the fed back information to
`adjust
`the gain and or phase relationship between the
`quadrature signals that are subsequently quadrature-phase
`modulated and transmitted. A variety of techniques can be
`employed to allow the image signal energy to be measured
`directly by the receiver component. The phase modulation
`signals at the transmitter can be interchanged, so that the
`image signal energy is transmitted in the sideband of the
`intended signal. Alternatively, the phase modulation signals
`at the receiver can be interchanged, so that the receiver’s
`operating frequency is shifted from the frequency of the
`transmitter’s intended signal sideband to the frequency of
`the transmitter’s image signal sideband.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention is explained in further detail, and by way of
`example, with reference to the accompanying drawings
`wherein:
`
`Page 6 of 10
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`Page 6 of 10
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`

`US 6,717,981 B1
`
`3
`FIG. 1 illustrates an example block diagram of a prior art
`time-division-duplex transceiver having a common local
`oscillator.
`
`FIG. 2 illustrates an example spectral diagram of a prior
`art quadrature-phase transmitter with a non-ideal relation-
`ship between quadrature signals.
`FIG. 3 illustrates an example block diagram of a time-
`division-duplex transceiver in accordance with this inven-
`tion.
`
`FIG. 4 illustrates an example spectral diagram of a
`quadrature-phase transmitter in accordance with this inven-
`tion.
`
`10
`
`FIG. 5 illustrates an example block diagram of an alter-
`native time-division-duplex transceiver in accordance with
`this invention.
`
`15
`
`FIG. 6 illustrates an example block diagram of a double
`quadrature module for use in a transceiver in accordance
`with this invention.
`
`Throughout the drawings, same reference numerals indi-
`cate similar or corresponding features or functions.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`FIG. 3 illustrates an example block diagram of a time-
`division-duplex transceiver 300 in accordance with this
`invention. The transceiver 300 is configured to allow for the
`receiver 310 of the transceiver 300 to receive the composite
`transmit signal 151 from the transmitter 330 of the trans-
`ceiver 300. A switch 320 effects the coupling of the com-
`posite signal 151 to the demodulators 172, 174 when a
`calibrate signal 325 is asserted. Also illustrated is an optional
`attenuation device 360 that attenuates the switched compos-
`ite signal 151 to form an attenuated composite signal 361 at
`a signal strength corresponding to the signal strength of the
`typical received composite signal 161 from the antenna 165.
`While in the calibrate mode, the receive/transmit switch 160
`decouples the received composite signal 161 from the
`receive signal path. The receiver 310 provides a character-
`ization signal 311, such as a signal strength indication at one
`or more select frequencies, that is fed back to the transmitter
`330, typically via a feedback device 340. In accordance with
`this invention, the transmitter 330 includes means for con-
`trolling the phase and/or the gain of one or both of the
`quadrature signals TI 131 and TO 132, and/or the relative
`phase of the local oscillation signals 121, 122. Such phase
`and gain controlling means are common in the art and
`include voltage or switch controlled phase shifters and
`variable gain amplifiers and filters. The feedback device 340
`is configured to effect the transformation,
`if any, of the
`characterization signal 311 to provide the appropriate con-
`trol signals 341, 342 to effect the change of phase and/or
`gain in the transmitter 330, and/or the relative phase of the
`local oscillation signals 121, 122, as determined by the
`particular characteristics of the selected means for effecting
`this control.
`
`the characterization
`In accordance with this invention,
`signal 311 provides a characterization of the unwanted
`image signal component, component 230 in FIG. 2, that is
`contained within the transmitted composite signal 151.
`When placed in the calibrate mode,
`the transmitter 330
`applies the control signals 341, 342 corresponding to this
`unwanted image signal component to reduce the magnitude
`of this unwanted signal component. Conventional closed-
`loop feedback techniques are embodied in a preferred
`embodiment of this invention to minimize the magnitude of
`this unwanted signal component in response to the charac-
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`4
`terization signal 311. By minimizing the magnitude of the
`unwanted image signal component in the composite signal
`151, the degree of filtering required at the transmitter 130 or
`a distant receiver (not shown) to provide an undistorted
`representation of the originally input information 201 can be
`substantially reduced. In like manner, by minimizing the
`magnitude of the unwanted image signal component in the
`composite signal 151, the intermediate frequency used by
`the transmitter 330 and receiver 310 can be low. These and
`
`other advantages of a suppression of the unwanted image
`signal component in a transmitted composite signal will be
`evident to one of ordinary skill in the art.
`Note that, to achieve these advantages, the characteriza-
`tion signal 311 must correspond substantially to a charac-
`terization of the unwanted signal component, and the sen-
`sitivity of the receiver must be sufficient
`to detect
`the
`relatively low amplitude unwanted image signal component.
`A number of techniques can be utilized to provide the
`appropriate characterization signal 311. Two such tech-
`niques are particularly well suited for an embodiment of this
`invention in a transceiver that utilizes a common set of
`
`quadrature oscillation signals for modulation and demodu-
`lation.
`
`Illustrated in FIG. 3 is an example block diagram of a
`system that can be configured to provide the unwanted
`signal component (230 in FIG. 2) in the sideband that
`typically contains the wanted signal component (220 in FIG.
`2). The switch 320 in this preferred embodiment is config-
`ured to interchange the in-phase oscillation signal 121 with
`the quadrature-phase oscillation signal 122. In this manner,
`because the oscillation signals 321 and 322 used to modulate
`the transmit quadrature signals TI 131 and TO 132 are
`interchanged relative to the oscillation signals 121 and 122
`used to demodulate the receive quadrature signals RI 173
`and RQ 175, the resultant sidebands are also interchanged in
`the frequency domain. By providing the formerly unwanted
`signal component 230 in the conventional sideband of the
`wanted signal component, the characterization signal 311
`from the receiver 310 can be easily derived from signals that
`are present
`in a conventional receiver. For example, a
`conventional receiver typically contains an internal gain-
`control signal, commonly termed an Automatic Gain Con-
`trol (AGC) signal, or a Received Signal Strength Indicator
`(RSSI) signal,
`that
`is used to compensate for different
`composite signal 161 strengths from the antenna 165. This
`conventionally provided signal strength indicator is struc-
`tured to provide a measure of the signal strength of the
`intended signal component, 220 of FIG. 2. By switching the
`unwanted signal component 230 into the sideband that
`conventionally contains the intended signal component 220,
`this conventionally provided signal strength indicator in the
`receiver 310 can be utilized as the characterization signal
`311. As will be evident to one of ordinary skill in the art in
`view of this invention, other methods of effecting this
`sideband switching is also feasible, for example, the receive
`signals RI 173 and RQ 175 can be interchanged relative to
`the oscillation signals 121 and 122.
`FIG. 4 illustrates an example spectral diagram of the
`quadrature-phase transmitter 300 in accordance with this
`invention. FIG. 4 includes the spectral response 210, 220,
`230 (dashed line) corresponding to a conventional
`transmission, when the calibrate signal 325 of FIG. 3 is not
`asserted, as well as the spectral response 410, 420, 430 (solid
`line) corresponding to the calibrate signal 325 being
`asserted. Because the oscillation frequencies 321, 322 are
`opposite the, conventional oscillation frequencies 121, 122,
`the resultant spectral
`response 410, 420, 430 is,
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`US 6,717,981 B1
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`5
`substantially, a mirror image of the conventional spectral
`response 210, 220, 230. The component 430 corresponds to
`the conventional unwanted signal component 230, except
`that it is located in the sideband at Fc+IF that conventionally
`contains the intended signal component 220. Because the
`switch 320 of FIG. 3 connects the composite output 151
`corresponding to the spectral response 410, 420, 430 to the
`receiving demodulators 172, 174 when the calibrate control
`signal 325 is asserted,
`the conventional circuitry in the
`receiver 310 of FIG. 3 processes the unwanted signal
`component 430 as if it were the intended signal component
`220, and in so doing, provides indications of the unwanted
`signal component 430 that are used to provide the charac-
`terization signal 311 that is used to effect a reduction in this
`unwanted signal component 430.
`FIG. 5 illustrates an example block diagram of an alter-
`native time-division-duplex transceiver 500 in accordance
`with this invention. In contrast to the transceiver 300 of FIG.
`
`3, a switch 520 is used to interchange the in-phase 121 and
`quadrature-phase 122 oscillation signals used by the receive
`demodulators 172, 174 when the calibration control signal
`325 is asserted. The interchange of the in-phase 121 and
`quadrature-phase 122 oscillation signals to form oscillation
`signals 521 and 522 that are opposite the conventional
`relationship with the oscillation signals 121, 122 used to
`modulate the quadrature signals TI 131 and 132 has the
`effect of switching the center frequency of the receiver 310
`to coincide with the sideband FC—IF that conventionally
`contains the unwanted signal component 230 of FIG. 2.
`Similar to the case of the transceiver 300, when the calibrate
`control signal 325 is asserted and the receiver center fre-
`quency is shifted, the conventional circuitry in the receiver
`310 of FIG. 5 processes the unwanted signal component 230
`as if it were the intended signal component 220, and in so
`doing, provides indications of the unwanted signal compo-
`nent 230 that are used to provide the characterization signal
`311 that is used to effect a reduction in this unwanted signal
`component 230.
`As noted above, the magnitude of the unwanted image
`signal component
`is relatively low, and,
`in a preferred
`embodiment, the receiver is configured to be sensitive to
`such low magnitude signals, and relatively insensitive to
`signals beyond the bandwidth of the supplied image, com-
`ponent 361 from the transmitter 330. FIG. 6 illustrates an
`example block diagram of a double quadrature module 600
`for use in a transceiver 300, 500 in accordance with this
`invention. The double quadrature module, conventional in
`the art, provides a higher image rejection at the receiver, and
`a higher sensitivity to the unwanted image signal
`component, when the transceiver 300, 500 is placed in the
`calibrate mode. Other techniques for improving the perfor-
`mance and sensitivity of the transceiver would be evident to
`one of ordinary skill in the art in view, of this disclosure.
`In particular, FIG. 6 shows an RF input 661 which is
`similar to the RF input provided to the demodulators 172,
`174 shown in FIG. 3. However, instead of being provided
`directly to the demodulators 172, 174, the RF input 661 is
`provided to a phase shifter 610 whose output is provided to
`four demodulators 612, 614, 616, 618 that also receive
`oscillating signals 121, 122 from the local oscillator 120 in
`combination with the phase shifter 125. The outputs of the
`demodulators 612, 614, 616, 618 are selectively provides to
`adders 620, 630, whose outputs are filtered by a polyphase
`filter 640 and provided to the receiver 310 as the I and Q
`receive signals RI 173, RQ 175, as also shown in FIG. 3.
`The foregoing merely illustrates the principles of the
`invention. It will thus be appreciated that those skilled in the
`
`6
`art will be able to devise various arrangements which,
`although not explicitly described or shown herein, embody
`the principles of the invention and are thus within the spirit
`and scope of the following claims.
`I claim:
`
`1. A transceiver comprising:
`a transmitter that is configured to receive an input signal
`and produces therefrom an in-phase transmit signal and
`a quadrature-phase transmit signal,
`a modulator that is configured to modulate the in-phase
`transmit signal and the quadrature-phase transmit sig-
`nal and to produce therefrom a composite signal that
`includes an intended signal component and an
`unwanted signal component,
`a demodulator that is selectively configured to demodu-
`late the composite signal and to produce therefrom an
`in-phase receive signal and a quadrature-phase receive
`signal, and
`is configured to receive the in-phase
`a receiver that
`receive signal and the quadrature-phase receive signal,
`and to produce therefrom a characterization signal that
`is correlated substantially to the unwanted signal com-
`ponent of the composite signal,
`wherein
`
`the transceiver is configured to adjust at least one of a
`phase and an amplitude of at least one of the in-phase
`transmit signal and the quadrature-phase transmit
`signal, based on the characterization signal.
`2. The transceiver of claim 1, further including
`a local oscillator that
`is configured to provide a first
`oscillation signal and a second oscillation signal, and
`wherein
`
`the phase of the least one of the in-phase transmit signal
`and the quadrature-phase transmit signal is adjusted
`by modifying a phase relationship between the first
`oscillation signal and the second oscillation signal.
`3. The transceiver of claim 2, further comprising a switch
`which is configured to interchange said first oscillation
`signal and said second oscillation signal to form a first
`interchanged oscillation signal and a second interchanged
`oscillation signal; wherein said modulator produces said
`composite signal in response to one of said first oscillation
`signal and said second oscillation signal and said first
`interchanged oscillation signal and said second interchanged
`oscillation signal, and said demodulator demodulates said
`composite signal in response to another of said first oscil-
`lation signal and said second oscillation signal and said first
`interchanged oscillation signal and said second interchanged
`oscillation signal.
`4. The transceiver of claim 1, further comprising:
`a double quadrature module that provides a high image
`rejection at
`the receiver,
`thereby providing a high
`sensitivity to the characterization signal.
`5. The transceiver of claim 1, wherein
`the intended signal component is located at a first side-
`band frequency,
`the unwanted signal component is located at a second
`sideband frequency, and
`the transceiver further includes a switch that is configured
`to effect a frequency change at the receiver such that the
`receiver is centered at the second sideband frequency.
`6. The transceiver of claim 5, further including
`a local oscillator that is configured to provide an in-phase
`oscillation signal and a quadrature-phase oscillation
`signal, and
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`US 6,717,981 B1
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`7
`
`wherein
`the demodulator is configured to demodulate the com-
`posite signal based on the in-phase oscillation signal
`and the quadrature-phase oscillation signal, and
`the switch is configured to effect the tuning frequency
`change by interchanging the in-phase oscillation
`signal and the quadrature-phase oscillation signal.
`7. The transceiver of claim 1, wherein
`the receiver is further configured to produce the charac-
`terization signal based on a receiver tuning frequency,
`and
`
`the transceiver further includes a switch that is configured
`to effect a change in the modulator so that the unwanted
`signal component is produced at the receiver tuning
`frequency.
`8. The transceiver of claim 7, further including
`a local oscillator that is configured to provide an in-phase
`oscillation signal and a quadrature-phase oscillation
`signal, and
`wherein
`the modulator is configured to produce the composite
`signal based on the in-phase oscillation signal and
`the quadrature-phase oscillation signal, and
`the switch is configured to effect the change in the
`modulator to produce the unwanted signal compo-
`nent at the receiver tuning frequency by interchang-
`ing the in-phase oscillation signal and the
`quadrature-phase oscillation signal.
`9. The transceiver of claim 1, further comprising an
`oscillator that is configured to form a first oscillating signal
`and a second oscillating signal; and a switch which is
`configured to interchange said first oscillating signal and
`said second oscillating signal to form a first interchanged
`oscillating signal and a second interchanged oscillating
`signal; said modulator being configured to receive one of
`said first oscillating signal and said second oscillating signal
`and said first interchanged oscillating signal and said second
`interchanged oscillating signal, and said demodulator being
`configured to receive another of said first oscillating signal
`and said second oscillating signal and said first interchanged
`oscillating signal and said second interchanged oscillating
`signal.
`10. A method of suppressing an unwanted signal compo-
`nent
`from a transmission of a transceiver,
`the method
`comprising:
`receiving an input signal and producing therefrom an
`in-phase transmit signal and a quadrature-phase trans-
`mit signal,
`modulating the in-phase transmit signal and the
`quadrature-phase transmit signal and producing there-
`from a composite signal
`that
`includes an intended
`signal component and the unwanted signal component,
`demodulating the composite signal and producing there-
`from an in-phase receive signal and a quadrature-phase
`receive signal,
`receiving the in-phase receive signal and the quadrature-
`phase receive signal, and producing therefrom a char-
`acterization signal that is correlated substantially to the
`unwanted signal component of the composite signal,
`and adjusting at least one of a phase and an amplitude of
`at least one of the in-phase transmit signal and the
`quadrature-phase transmit signal, based on the charac-
`terization signal, to suppress the unwanted signal com-
`ponent.
`11. The method of claim 10, wherein
`the intended signal component is located at a first side-
`band frequency,
`
`5
`
`10
`
`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`8
`the unwanted signal component is located at a second
`sideband frequency, and
`the method further includes
`the
`changing a receiver center frequency such that
`characterization signal is based on a measure of a
`signal that is received at the second sideband fre-
`quency.
`12. The method of claim 11, further including
`providing an in-phase oscillation signal and a quadrature-
`phase oscillation signal, and
`wherein
`
`the demodulating of the composite signal includes
`demodulating the composite,signal based on the
`in-phase oscillation signal and the quadrature-
`phase oscillation signal, and
`the changing of the receiver center frequency
`includes
`
`is based on the
`
`interchanging the in-phase oscillation signal and
`the quadrature-phase oscillation signal.
`13. The method of claim 11, wherein
`producing the characterization signal
`receiver center frequency, and
`modulating the in-phase transmit signal and the
`quadrature-phase transmit signal is effected so as to
`provide the unwanted signal component at the receiver
`center frequency.
`14. The method of claim 13, further including
`providing an in-phase oscillation signal and a quadrature-
`phase oscillation signal, and
`wherein
`
`modulating the in-phase transmit signal and the
`quadrature-phase transmit signal
`to provide the
`unwanted signal component at the receiver center
`frequency is effected by interchanging the in-phase
`oscillation signal and the quadrature-phase oscilla-
`tion signal.
`15. The method of claim 10, wherein
`adjusting the phase of at least one of the in-phase transmit
`signal and the quadrature-phase transmit signal
`includes adjusting the relative phase of a first oscilla-
`tion signal and a second oscillation signal that are used
`to effect at least one of modulating the in-phase trans-
`mit signal and the quadrature-phase transmit signal and
`demodulating the composite signal.
`16. A transceiver comprising:
`a receiver that is configured to receive first information
`signals,
`a transmitter that is configured to transmit second infor-
`mation signals, and
`a switch that is configured to couple the transmitter and
`the receiver so that
`the first
`information signals
`received by the receiver correspond to the second
`information signals that are transmitted from the trans-
`mitter during a calibration mode,
`wherein
`
`the transceiver is configured to provide for an adjust-
`ment of at least one of a phase and a gain of the
`second information signals in dependence upon the
`first information signals that are received during the
`calibration mode,
`wherein said switch is further configured to interchange
`an I transmit signal and a Q transmit signal from a
`local oscillator to form a Q receive signal from said
`I transmit signal and an I receive signal from said Q
`transmit signal, said Q receive signal and said I
`receive signal being provided to said receiver.
`
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`Page 9 of 10
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`US 6,717,981 B1
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`9
`17. A method of calibrating a transmitter in a transceiver
`that includes a receiver comprising:
`transmitting a first signal via the transmitter,
`interchanging an I transmit signal and a Q transmit signal
`from a local oscillator to form a Q receive signal from
`said I transmit signal and an I receive signal from said
`Q transmit signal,
`receiving the first signal, said Q receive signal, and said
`I receive signal via the receiver to provide a charac-
`.
`.
`.
`terization s1gnal, and
`adjusting the transmitter in dependence upon the charac-
`terization signal.
`18. The method of claim 17, wherein
`adjusting the transmitter includes adjusting at least one of 15
`a phase or a gain of the transmitter to facilitate reduc-
`tion of unwanted signals.
`19. The method of claim 17, wherein
`adjusting the transmitter includes adjusting a phase of one
`or more oscillation signals provided to said transmitter
`to facilitate rejection of unwanted signals.
`20. A transceiver comprising:
`a transmitter that is configured to transmit a first signal;
`