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`US005649308A
`5,649,308
`[111 Patent Number:
`[45] Date of Patent:
`Jul. 15, 1997
`
`United States Patent c191
`Andrews
`
`[54] MULTIFORMAT AUTO-BANDOFF
`COMMUNICATIONS HANDSET
`
`[75]
`
`Inventor: Scott Andrews, Long Beach, Calif.
`
`[73] Assignee: TRW Inc., Redondo Beach, Calif.
`
`[21] Appl. No.: 556,863
`Nov. 2, 1995
`
`[22] Filed:
`
`[63]
`
`[51]
`[52]
`[58]
`
`[56]
`
`Related U.S. Application Data
`
`Continuation of Ser. No. 48,045,Apr. 12, 1993, abandoned.
`Int. CI. 6 ....................................................... H04B 1/38
`U.S. CI ................................................ 370/334; 455/84
`Field of Search .................................. 455/33.2, 33.3,
`455/33.4, 34.1, 34.2, 54.1, 56.1, 89, 84;
`379/60
`
`References Cited
`
`U.S. PATENf DOCUMENTS
`
`4,901,307
`4,972,455
`5,020,092
`5,020,093
`5,101,501
`5,127,042
`
`211990 Gilhousen et al ........................ 370118
`11/1990 Phillips et al ............................. 455n6
`511991 Phillips et al ............................. 455n7
`511991 Pireh ......................................... 455n7
`311992 Gilhousen et al. . ................... 455/33.2
`611992 Gillig et al. . ............................. 379159
`
`30
`
`5,252,979 1011993 Nysen ....................................... 455n3
`5,295,152
`311994 Gudmundson et al. .. .............. 375/205
`5,323,446
`6/1994 Kojima et al .......................... 455/33.2
`5,329,635
`711994 Wadin et al ........................... 455/33.2
`2/1995 Komaki ..................................... 455189
`5,392,462
`6/1995 Kobayashi ................................ 455189
`5,428,664
`811995 Durlcer et al ............................. 455n4
`5,438,683
`5,509,035
`411996 Teidemann, Jr. et al .............. 455/33.2
`
`Primary Examiner-Edward F. Urban
`Attorney, Agent, or Finn-Michael S. Yatsko
`ABSTRACT
`
`[57]
`
`Disclosed is an apparatus and method for supporting com(cid:173)
`munications and handoffs between multiple signal formats at
`multiple carrier frequencies. Antenna circuitry which
`includes a linearly polarized antenna and a circularly polar(cid:173)
`ized antenna is utilized to receive and transmit the multiple
`signal formats at the multiple carrier frequencies simulta(cid:173)
`neously. A pair of RF signal paths each including RF
`transmit circuitry, RF receive circuitry and RF processing
`capabilities are utilized to support simultaneous communi(cid:173)
`cations between two signal formats. A multisystem control(cid:173)
`ler in communications with each RF signal path initiates and
`completes handoffs between the multiple signal formats
`utilizing both RF signal paths to achieve uninterrupted
`communications across a large service coverage area.
`
`39 Claims, 4 Drawing Sheets
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`Ex.1022
`APPLE INC. / Page 3 of 14
`
`

`

`U.S. Patent
`
`Jul. 15, 1997
`
`Sheet 3 of 4
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`5,649,308
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`Ex.1022
`APPLE INC. / Page 4 of 14
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`

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`U.S. Patent
`
`Jul. 15, 1997
`
`Sheet 4 of 4
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`5,649,308
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`Ex.1022
`APPLE INC. / Page 5 of 14
`
`

`

`5,649,308
`
`1
`MULTIFORMAT AUTO-HANDOFF
`COMMUNICATIONS HANDSET
`
`This application is a continuation of U.S. patent appli(cid:173)
`cation Ser. No. 08/048,045, filed Apr 12, 1993, now aban- 5
`doned.
`
`2
`tiple signal formats at multiple carrier frequencies; elimi(cid:173)
`nating multiple RF hardware strings; operating over a
`broadband and extending the service coverage area by
`communicating over both terrestrial and satellite base sta(cid:173)
`tions. It is therefore an object of the present invention to
`provide such a device.
`
`SUMMARY OF THE INVENTION
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates generally to a communications
`handset and, more particularly, to a multiformat auto(cid:173)
`handoff communications handset to support communica(cid:173)
`tions and handoffs between multiple signal formats at mul(cid:173)
`tiple carrier frequencies.
`2. Discussion of the Related Art
`Mobile and cellular communication systems currently
`utilize several types of signal formats and carrier frequen(cid:173)
`cies. For example, some of the various cellular standards
`used today include AMPS (Analog Modulation Phone
`Service), IS-54 (North American Digital Cellular), PCN
`(Personal Communications Network), DECT (European
`Digital Cordless Telephone Standard) and GSM (Groupe
`Speciale Mobile). These signal formats typically operate
`around 800 MHz to 900 MHz or around 1.70 GHz to 1.90
`GHz and utilize a network of terrestrial base stations.
`In addition, with the immense growth in the mobile and
`cellular communications industry, many new and planned
`signal formats and carrier frequencies will be utilized to
`increase the number of possible users and the service
`coverage areas. These new and planned signal formats
`include FDM (Frequency Division Multiplex), TDMA
`(rime Division Multiple Access), CDMA (Code Division
`Multiple Access) and many others. The new and planned
`signal formats will operate between 800 MHz to about 2.40
`GHz and utilize both terrestrial base stations and satellite
`base stations.
`Today, the currently utilized communications handsets
`(telephone) are each specifically designed to support a
`particular signal format and a particular carrier frequency.
`Therefore, each communications handset is quite limited in
`its capabilities to support multiple signal formats at multiple
`carrier frequencies. The current approaches to making the
`communications handsets more compatible with various
`signal formats and also various carrier frequencies is essen(cid:173)
`tially to build multiple RF (radio frequency) hardware
`strings, such that each RF hardware string is capable of
`supporting a particular signal format at a particular carrier
`frequency. Another approach is to use add-on circuitry to
`convert the communications handset from one signal format
`to another or from one carrier frequency to another. Yet
`another extreme approach is to maintain multiple commu(cid:173)
`nications handsets so that when the user exits one service
`coverage area, the user would utilize another communica(cid:173)
`tions handset to initiate a new call in the particular service
`coverage area
`However, these current approaches are very poor and not
`cost effective since they easily double the RF hardware
`required and waste precious RF output power generated by
`the communications handset This directly impacts on the
`size and the weight of the communications handset as well
`as the battery operating time. In addition, the multiple
`circuits and the add-on circuitry adds a significant additional
`cost to the communications handset.
`What is needed then is a multiformat auto-handoff com(cid:173)
`munications handset which is capable of: supporting mul-
`
`30
`
`35
`
`In accordance with the present invention, a multiformat
`10 auto-handoff communications handset is utilized to support
`communications and handoffs between multiple signal for(cid:173)
`mats at multiple carrier frequencies. This is basically
`achieved by utilizing a first and a second RF signal path each
`capable of supporting the multiple signal formats at the
`15 multiple carrier frequencies and a multisystem controller.
`This essentially allows the first RF signal path to be utilized
`during normal communications until the user begins to exit
`the service coverage area of that signal format. Once this is
`detected by the multisystem controller, the multisystem
`20 controller will initiate a handoff utilizing the second RF
`signal path to establish communications with another signal
`format in another service coverage area. After the connec(cid:173)
`tion is established on the second RF signal path, the com(cid:173)
`munications occurring in the first RF signal path is termi-
`25 nated. This allows the user of the communications handset
`to maintain an uninterrupted call beyond the service cover(cid:173)
`age area of one signal format
`In one preferred embodiment, antenna circuitry receives
`and transmits the multiple signal formats at the multiple
`carrier frequencies. The antenna circuitry is capable of
`simultaneously receiving a first RF receive signal and a
`second RF receive signal as well as being capable of
`simultaneously transmitting a first RF transmit signal and a
`second RF transmit signal. The first RF receive signal
`received by the antenna circuitry is down converted into a
`first IF (intermediate frequency) receive signal by a first
`broadband RF receive system and the second RF receive
`signal is down converted into a second IF receive signal by
`a second broadband RF receive system. The first IF receive
`40 signal is then demodulated in a first digital/IF baseband
`processor controller while the second IF receive signal is
`demodulated in a second digital/IF baseband processor
`controller.
`The first IF/baseband processor controller modulates a
`first IF transmit signal and the second digital/IF baseband
`processor controller modulates a second IF transmit signal.
`The first IF transmit signal is up converted into the first RF
`transmit signal by a first broadband RF transmit system and
`50 the second IF transmit signal is up converted into the second
`RF transmit signal by a second broadband RF transmit
`system. The first RF transmit signal and the second RF
`transmit signal are then transmitted by the antenna circuitry.
`In addition, the multisystem controller is utilized for initi-
`55 ating and completing handoffs between the multiple signal
`formats at the multiple carrier frequencies.
`Use of the present invention results in supporting multiple
`signal formats at multiple carrier frequencies by employing
`a multiformat auto-handoff communications handset. As a
`60 result, the aforementioned problems associated with the
`current approaches have been substantially eliminated.
`
`45
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`Still other advantages of the present invention will
`65 become apparent to those skilled in the art after reading the
`following specification and by reference to the drawings in
`which:
`
`Ex.1022
`APPLE INC. / Page 6 of 14
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`

`

`5,649,308
`
`3
`FIG. 1 is a schematic/block diagram of one preferred
`embodiment of the present invention;
`FIG. 2 is a schematic/block diagram of another preferred
`embodiment of the present invention;
`FIG. 3 is a detailed schematic/block diagram of an RF
`receive system, an RF transmit system and a digital
`W/baseband processor controller of the present invention;
`FIG. 4 is a detailed schematic/block diagram of a dual
`ortho broadband image reject mixer of the present invention;
`FIG. 5 is a detailed schematic/block diagram of a broad(cid:173)
`band single sideband modulator of the present invention;
`FIG. 6 is a detailed schematic/block diagram of a quadra(cid:173)
`ture LO (local oscillator) generator of the present invention;
`and
`FIG. 7 is a waveform diagram of the output of the
`quadrature LO generator of FIG. 6.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The following description of a multiformat auto-handoff
`communications handset to support communications and
`handoffs between multiple signal formats at multiple carrier
`frequencies is merely exemplary in nature and is in no way
`intended to limit the invention or its application or uses.
`Referring to FIG. 1, a schematic/block diagram of one
`preferred embodiment of a multiformat auto-handoff com(cid:173)
`munications handset 10 to support communications and
`handoffs between multiple signal formats at multiple carrier
`frequencies, is shown. The multiformat auto-handoff com(cid:173)
`munications handset 10 preferably includes a linearly polar(cid:173)
`ized L-band antenna 12 and a circularly polarized LC-band
`antenna 14. The linearly polarized L-band antenna 12 pref(cid:173)
`erably operates in the range of 800 MHz to 950 MHz and is
`typically utilized for transmitting and receiving RF signals
`from terrestrial base stations (not shown). The circularly
`polarized LC-band antenna 14 preferably operates in the
`range of 1.5 GHz to 2.4 GHz and is typically utilized for
`transmitting and receiving RF signals from satellite mounted 40
`transponders (not shown). A first RF receive signal and a
`second RF receive signal received from the linearly polar(cid:173)
`ized L-band antenna 12 and the circularly polarized
`LC-band antenna 14 are applied to a bi-directional broad(cid:173)
`band duplexor/multiplexor 16. The bidirectional broadband 45
`duplexor/multiplexor 16 combines the first RF receive signal
`and the second RF receive signal and applies the combined
`RF receive signal to a broadband low noise pre-amp 18. The
`broadband low noise pre-amp 18 operates over a one and a
`half octave bandwidth (800 MHz to 2.4 GHz) and amplifies
`the combined RF receive signal from the bidirectional
`broadband duplexor/multiplexor 16 while adding only a
`minimal amount of noise. The broadband low noise pre-amp
`18 applies the combined amplified RF receive signal to a
`power divider 20 which splits the power of the combined
`amplified RF receive signal to apply substantially identical
`images of the first RF receive signal and the second RF
`receive signal to a RF receive system 22 and a RF receive
`system 24.
`Assuming the RF receive system 22 is operating at the
`first RF receive signal format and frequency, the RF receive
`system 22 will accept the first RF receive signal and down
`convert it into a first IF receive signal which is applied to a
`digital W/baseband processor controller 26. Making the
`same assumption for the RF receive system 24, the RF
`receive system 24 will down convert the second RF receive
`signal into a second IF receive signal which is applied to a
`
`4
`digital IF/baseband processor controller 28. The IF receive
`signals have a bandwidth of a few hundred KHz and vary
`depending on the particular signal format used. The digital
`IF/baseband processor controllers 26 and 28 are preferably
`5 silicon monolithic integrated circuits which are capable of
`demodulating the IF receive signals to extract voice and/or
`operating data which is provided either to the user of the
`multiformat auto-handoff communications handset 10 or
`utilized internally. These digital IF/baseband processor con-
`10 trollers 26 and 28 are preferably constructed from a chip set
`consisting of a Motorola DSP 56000, two 64K PROMs, two
`8K RAMs, and a CODEC chip to do baseband voice coding.
`However, one skilled in the art will readily recognize that
`Application Specific Integrated Circuits (ASICs) can also be
`15 utilized that incorporate the functions of the above(cid:173)
`mentioned chip set
`Voice data from the user and/or operating data is modu(cid:173)
`lated in the digital IF/baseband processor controllers 26 and
`28 to create a first IF transmit signal and a second IF transmit
`20 signal. The first IF transmit signal is applied to a RF transmit
`system 30 and the second IF' transmit signal is applied to a
`RF transmit system 32. The RF transmit system 30 up
`converts the first IF transmit signal into a first RF transmit
`signal at the appropriate carrier frequency and the RF
`25 transmit system 32 up converts the second IF' transmit signal
`into a second RF transmit signal at the appropriate carrier
`frequency.
`The first RF transmit signal and the second RF transmit
`signal are applied to a power combiner 34 which combines
`30 the first RF transmit signal and the second RF transmit signal
`and applies the combined RF transmit signal to a broadband
`power amp 36. The broadband power amp 36 is preferably
`a broadband linear power amplifier which amplifies the
`combined RF transmit signal and applies the combined
`35 amplified RF transmit signal to the bidirectional broadband
`duplexor/multiplexor 16. The bidirectional broadband
`duplexor/multiplexor 16 splits the combined RF transmit
`signal and applies the first RF transmit signal and the second
`RF transmit signal to either the linearly polarized L-band
`antenna 12 or the circularly polarized LC-band antenna 14,
`depending on the signal format and frequency.
`In another preferred embodiment, shown clearly in FIG.
`2, the first RF transmit signal is applied to a broadband
`power amp 38 and the second RF transmit signal is applied
`to a broadband power amp 40. The broadband power amp 38
`amplifies the first RF transmit signal and applies it to the
`bidirectional broadband duplexor/multiplexor 16 and the
`broadband power amp 40 amplifies the second RF transmit
`signal and also applies it to the bidirectional broadband
`50 duplexor/multiplexor 16. The bidirectional broadband
`duplexor/multiplexor 16 applies the first RF transmit signal
`and the second RF transmit signal to either the linearly
`polarized L-band antenna 12 or the circularly polarized
`LC-band antenna 14 depending on the signal format and
`55 frequency. This embodiment essentially eliminates the
`power combiner 34 and utilizes the pair of broadband power
`amps 38 and 40 to amplify the separate RF transmit signals.
`Returning to FIG. 1, in operation, the multiformat auto(cid:173)
`handoff communications handset 10 typically utilizes only a
`60 single RF signal path consisting of either the RF receive
`system 22, the digital W/baseband processor controller 26
`and the RF transmit system 30 or the RF receive system 24,
`the digital IF/baseband processor controller 28 and the RF
`transmit system 32. However, when a handoff is required
`65 between different signal formats, the multiformat auto(cid:173)
`handoff communications handset 10 utilizes both RF signal
`paths. For example, if the user is first communicating with
`
`Ex.1022
`APPLE INC. / Page 7 of 14
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`

`

`5,649,308
`
`5
`another user through a terrestrial base station (not shown), a
`first RF receive signal will be received by the linearly
`polarized L-band antenna 12, routed through the bidirec(cid:173)
`tional broadband duplexor/multiplexor 16 and applied to the
`broadband low noise pre-amp 18. The broadband low noise 5
`pre-amp 18 will amplify the first RF receive signal and apply
`it to the power divider 20. The power divider 20 will split the
`power of the first RF receive signal and apply it to the RF
`receive system 22 and the RF receive system 24. Assuming
`the RF receive system 22 is the RF signal path currently 10
`being utilized, the RF receive system 22 will down convert
`the first RF receive signal into an appropriate first IF receive
`signal and apply it to the digital IF/baseband processor
`controller 26. The digital IF/baseband processor controller
`26 will demodulate the first IF receive signal to extract the 15
`voice and/or operating data to pass it to the user and/or use
`it internally.
`The digital IF/baseband processor controller 26 will also
`modulate voice and/or operating data into a first IF transmit
`signal which is applied to the RF transmit system 30. The RF 20
`transmit system 30 will up convert the first IF transmit signal
`into a first RF transmit signal and apply it through the power
`combiner 34 to the broadband power amp 36. The broad(cid:173)
`band power amp 36 will amplify the first RF transmit signal
`and apply it to the bidirectional broadband duplexor/ 25
`multiplexor 16. The bidirectional broadband duplexor/
`multiplexor 16 will apply the amplified first RF transmit
`signal to the linearly polarized L-band antenna 12.
`As the communications are occurring between the users,
`a multisystem controller 42 monitors the power level and the 30
`operating data of the first RF receive signal applied to the RF
`receive system 22. The multisystem controller 42 is prefer(cid:173)
`ably a 16 bit microprocessor programmed to perform the
`various control functions. Moreover, one skilled in the art
`would recognize that the multisystem controller 42 can 35
`consist of an 8 bit microprocessor or be incorporated into the
`digital IF/baseband processor controllers 26 and 28. H the
`multisystem controller 42 detects that the signal level
`received from the terrestrial bas« station is too low, or that
`the terrestrial base station cannot handoff within the service 40
`coverage area of the signal format being used, the multisys(cid:173)
`tem controller 42 will initiate its handoff sequence to con(cid:173)
`nect the user to another signal format in order to insure an
`uninterrupted call. This condition typically occurs when the
`user enters into an outer fringe area of that particular service 45
`coverage area of that signal formal The multisystem con(cid:173)
`troller 42 internally contains a hierarchy of signal formats
`programmed into it such that the multisystem controller 42
`will attempt to connect the user to various signal formats
`until a successful connection is reached.
`When the multisystem controller 42 initiates its handoff
`sequence, the multisystem controller 42 will issue an order
`wire (similar to what occurs when a user picks up a phone)
`through the currently idle RF transmit system 32. The
`multisystem controller 42 will transmit operating data such 55
`as the user ID number and the type of signal format to be
`used to the digital IF/baseband processor controller 28. The
`digital IF/baseband processor controller 28 modulates this
`operating data into an appropriate second IF transmit signal
`which is applied to the RF transmit system 32. The RF 60
`transmit system 32 will up convert the second IF transmit
`signal into a second RF transmit signal (order wire) at the
`appropriate carrier frequency and apply it to the power
`combiner 34. The power combiner 34 combines the second
`RF transmit signal with the first RF transmit signal and 65
`applies the combined RF transmit signal to the broadband
`power amp 36. The broadband power amp 36 amplifies the
`
`6
`combined RF transmit signal and applies it to the bidirec(cid:173)
`tional broadband duplexor/multiplexor 16. The bidirectional
`broadband duplexor/multiplexor 16 will separate the com-
`bined RF transmit signal and apply the first RF transmit
`signal to the linearly polarized L-band antenna 12, while
`also applying the second RF transmit signal ( order wire) to
`the circularly polarized LC-band antenna 14, assuming the
`multisystem controller 42 is attempting a link with a satellite
`system (not shown).
`H the user is in the operating area of the satellite system,
`the satellite system will issue a return order wire (similar to
`receiving a dial tone on a phone). This return order wire will
`be received by the circularly polarized LC-band antenna 14,
`routed through the bidirectional broadband duplexor/
`multiplexor 16, amplified in the broadband low noise pre(cid:173)
`amp 18, divided through the power divider 20 and applied
`to the RF receive system 24 to complete the connection.
`Once this connection is made, the multisystem controller 42
`will direct the IF/baseband processor controller 26 to cease
`communicating with the terrestrial base station and direct
`the digital IF/baseband processor controller 28 to take over
`the call through the satellite system.
`Turning to FIG. 3, the RF signal path consisting of the RF
`receive system 22, the digital IF/baseband processor con(cid:173)
`troller 26 and the RF transmit system 30, is shown in more
`detail. It should be noted that this RF signal path is sub-
`stantially identical to the RF signal path consisting of the RF
`receive system 24, the digital IF/baseband processor con(cid:173)
`troller 28 and the RF transmit system 32. The RF receive
`system 22 includes a dual ortho broadband image reject
`mixer 44, a quadrature LO generator 46, a phase lock loop
`48, and a set of switchable bandpass filters 50. The phase
`lock loop 48 is adjusted by the digital IF/baseband processor
`controller 26 through a RX Tune port 52 which essentially
`adjusts the frequency of the quadrature LO generator 46.
`The quadrature LO generator 46 produces a pair of quadra-
`ture signals which are substantially 90° out of phase of each
`other over a broad frequency range. The pair of quadrature
`signals consist of an in phase signal (!Lo) and a quadrature
`signal (Qr..,) which are mixed with the RF receive signal in
`the dual ortho broadband image reject mixer 44. The dual
`ortho broadband image reject mixer 44, which will be
`discussed in more detail shortly, essentially down converts
`the RF receive signal into an appropriate IF receive signal
`while also rejecting an image signal. The IF receive signal
`is applied to the set of switchable bandpass filters 50, which
`is set to a particular bandpass filter from a Data Format port
`54 in the digital IF/baseband processor controller 26 based
`on the type of signal format being utilized. Thus, the set of
`50 switchable bandpass filters 50 essentially band limits the IF
`receive signal applied to a RX1F port 56 in the digital
`IF/baseband processor controller 26. In order to optimize the
`amplitude rejection of the image reject mixer 44, a pair of
`variable resistors 58 and 60 are utilized. The variable
`resistors 58 and 60 are adjusted during the manufacturing of
`the multiformat auto-handoff communications handset 10 to
`insure proper amplitude matching. In addition, in order to
`maintain a constant IF receive signal level into the digital
`IF/baseband processor controller 26, a RX Level port 62 in
`the digital IF/baseband processor controller 26 is used to
`adjust the signal strength of the IF receive signal through the
`dual ortho broadband image reject mixer 44.
`The RF transmit system 30 includes a phase lock loop 64,
`a quadrature LO generator 66, a bandpass filter 68, a
`broadband single sideband modulator 70 and a set of swit(cid:173)
`chable bandpass filters 72. To transmit an RF transmit signal,
`the digital IF/baseband processor controller 26 modulates
`
`Ex.1022
`APPLE INC. / Page 8 of 14
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`5,649,308
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`8
`7
`resultant signal in the upper image branch 106 is amplified
`voice and/or operating data into an IF transmit signal which
`by a variable in phase amp 114. The variable quadrature amp
`is applied from a TX1F port 74 to the bandpass filter 68. The
`112 is adjusted by the variable resistor 80 and the variable
`bandpass filter 68 band limits the IF transmit signal applied
`in phase amp 114 is adjusted by the variable resistor 82 to
`to the broadband single sideband modulator 70. The broad-
`band single sideband modulator 70, which will also be 5 ensure optimal amplitude matching. In addition, the variable
`quadrature amp 112 and the variable in phase amp 114 are
`discussed in more detail shortly, mixes the IF transmit signal
`with a pair of quadrature signals (lz.o and Qz.o) from the
`also adjusted by the TX Level port 84 in the digital
`quadrature LO generator 66. The pair of quadrature signals
`IF/baseband processor controller 26. The resultant signals in
`{Iz.o and Qz.o) are tuned by the phase lock loop 64 which is
`the lower image branch 104 and the upper image branch 106
`adjusted by a TX Tune port 76 in the digital IF/baseband 10 are both applied to a 0° power combiner 116 which essen-
`processor controller 26. This causes the broadband single
`tially sums the resultant signals from the lower image branch
`sideband modulator 70 to up convert the IF transmit signal
`104 and the upper image branch 106. This results in sup-
`into an appropriate RF transmit signal while also rejecting
`pressing a lower image signal thereby leaving an upper
`an image signal. The RF transmit signal is then applied to the
`image signal as the RF transmit signal.
`set of switchable bandpass filters 72. The switchable band- 15
`Turning to FIG. 6, the quadrature LO generator 46, which
`pass filters 72 are switched by a Mode port 78 to band limit
`is substantially identical to the quadrature LO generator 66,
`the RF transmit signal in order to eliminate transmitting
`includes a divide by one/divide by two circuit 118 which is
`harmonics (noise) of the RF transmit signal. In order to
`connected to a quadrature branch 120 and an in phase branch
`122. The quadrature branch 120 includes an inverter 124 and
`optimize the amplitude rejection of the broadband single
`sideband modulator 70, a pair of variable resistors 80 and 82 20 a divide by two circuit 126 and the in phase branch 122
`are adjusted during manufacturing to insure proper ampli-
`includes a divide by two circuit 128. A tuning signal from the
`tude matching. In addition, a TX Level port 84 in the digital
`phase lock loop 48 which is used to adjust the frequency of
`IF/baseband processor controller 26 is utilized to adjust the
`the quadrature pair signals (Qz.o and lz.o) is applied to the
`divide by one/divide by two circuit 118. A mode signal from
`output power level of the RF transmit signal. This is done in
`order to increase the power of the RF transmit signal when 25 the Mode port 78 in the digital IF/baseband process con-
`troller 26 is also applied to the divide by one/divide by two
`the user is distant from the base station and to lower the
`power when the user is nearer the base station.
`circuit 118 which causes the divide by one/divide by two
`When the RF receive signal is applied to the dual ortho
`circuit 118 to either divide the tuning signal by one or by
`broadband image reject mixer 44, shown clearly in FIG. 4,
`two. The resultant tuning signal is then applied to the
`a 0° power divider 86 splits the power of the RF receive 30 quadrature branch 120 and the in phase branch 122. The
`signal in the quadrature branch 120 is inverted in the inverter
`signal and applies substantially identical images of the RF
`receive signal to a lower image branch 88 and an upper
`124 and divided by two in the divide by two circuit 126 to
`image branch 90. The RF receive signal applied to the lower
`produce the quadrature signal ( Qz.o). The signal applied to
`image branch 88 is mixed in a mixer 92 with the quadrature
`the in phase branch 122 is divided by two in the divide by
`signal (Qz.o) from the quadrat