United States Patent 19
`Messerschmitt et al.
`
`USOO5267244A
`11) Patent Number:
`(45) Date of Patent:
`
`5,267,244
`Nov. 30, 1993
`
`54 METHOD AND AN APPARATUS FOR
`Attorney, Agent, or Firm-Limbach & Limbach
`ESTABLISHING THE FUNCTIONAL
`CAPABILITES FOR WIRELESS
`57
`ABSTRACT
`COMMUNICATIONS BETWEEN A BASE
`In a wireless communication system between a base unit
`UNT AND A REMOTE UNIT
`and a remote unit, the base unit transmits periodically a
`75 Inventors: David G. Messerschmitt, Moraga;
`sync signal in a first selected time period in a selected
`s Christopher Flores Oakland.
`s
`frequency channel. The remote unit scans the frequency
`Hulhung Lu, Danvie, all of Calif.
`channels to detect the sync signal. The remote unit
`As
`0.
`transmits a response signal in the selected frequency
`73) Assignee: Teknekron Communications Systems,
`channel. The response signal is transmitted in a second
`Inc., Berkeley, Calif.
`selected time period different from the first selected
`21 Appl. No.: 789,348
`time period. In addition, the remote unit transmits a first
`control signal encoded by a first code in the selected
`22 Filed:
`Nov. 8, 1991
`frequency channel in a third selected time period, differ
`51) int. Cl. ............................................. H04B 7/212
`ent from the first and second selected time periods,
`52 U.S.C. ..................................... 370/95.3; 370/29;
`containing a set of functional capabilities of the remote
`370/105.2; 370/107; 370/18; 370/110.1;
`unit. The base unit receives and decodes the first con
`379/63; 455/32.1455/342; 37.5/115
`trol signal to derive the set of functional capabilities of
`58) Field of Search ............... 370/18, 50, 95.3, 105.2,
`the remote unit and compares it to its own set of func
`370/107, 110.1, 29,379/63; 37.5/115; 455/32,
`tional capabilities to determine a common set of func
`34.2
`tional capabilities. The base unit transmits a second
`References Cited
`control signal encoded by the first code in the same
`U.S. PATENT DOCUMENTS
`selected frequency channel in a fourth selected time
`period containing the common set of functional capabil
`4,688,210 8/1987 Eizenhöfer et al................... 370/18
`ities. Thereafter, communication between the base unit
`5,020,094 5/1991 Rash et al. ........................ 379/63 X and the remote unit is based upon a functional capability
`5,031,207 7/1991 Hesdahl et al. .............. 370/10. X selected from the common set.
`Primary Examiner-Douglas W. Olms
`Assistant Examiner-Russell W. Blum
`
`13 Claims, 7 Drawing Sheets
`
`56)
`
`
`
`XMIT BY BASE 10
`
`XMIT BY EACH REMOTE 40
`
`USC-B
`SYNC
`-N- -N-
`%
`%
`2
`SW 1 SW 2
`CCM DATA
`UBC-B
`N-N- N-H'
`CSC-B
`UC-B
`CSC-R
`UC-R
`-N- -N-
`PACS-R ZPA2 USC-R UBC-R 2
`2
`%
`
`IPR2020-00038
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`

`

`U.S. Patent
`
`Nov.30, 1993
`
`Sheet 1 of 7
`
`5,267,244
`
`
`
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`
`
`
`
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`

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`U.S. Patent
`
`Noy. 30, 1993
`
`Sheet 2 of 7
`
`5,267,244
`
`NOLLVOISIYSA
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`IPR2020-00038
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`U.S. Patent
`
`Nov. 30, 1993
`
`Sheet 3 of 7
`
`5,267,244
`
`
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`Sheet 4 of 7
`
`5,267,244
`
`Nov. 30, 1993
`
`q8S
`
`U.S. Patent
`
`oOoOSoPnoOnosES
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`U.S. Patent
`
`Nov. 30, 1993
`
`Sheet 5 of 7
`
`5,267,244
`
`1240
`
`1260
`
`
`
`146b
`
`152
`
`
`
`
`
`I/Q CODED DATA
`(TO RRC FILTER)
`FIC 5c
`
`BINARY
`DATA
`
`160
`
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`U.S. Patent
`
`Nov. 30, 1993
`
`Sheet 6 of 7
`
`5,267,244
`
`INTERFACE AND MULTIPLEXER
`
`MULTIPLEXER
`
`SWITCH MATRIX
`
`N/ VDP
`PSTM/ISDM
`DATA TERM S-EARER-H /N VDP
`
`
`
`PHONE
`TERMINAL
`
`CONTROL UNIT
`
`APPLICATIONS
`CONTROLLER
`
`FIG. 6
`
`
`
`
`
`PANEL 'E
`
`
`
`190
`
`
`
`INTERFACE
`AND
`MULTIPLEXER
`
`PROTOCOL AND
`CONTROL UNIT
`
`FIC 7
`
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`U.S. Patent
`
`Nov.30, 1993
`
`Sheet 7 of 7
`
`5,267,244
`
`.5 MHz
`
`902 MHZ
`
`
`
`928 MHz
`
`XMIT BY EACH REMOTE 40
`XMIT BY BASE 10
`FIC 9
`
`USC-B
`SYNC
`-N- -N-
`
`N-- N--
`CSC-B
`UC-B
`
`FIC 10
`
`UC-R
`CSC-R
`-N- -N-
`2 PACS-R ZPA2 USC-R UBC-R 2
`F.C. ft.
`
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`

`

`1.
`
`METHOD AND AN APPARATUS FOR
`ESTABLISHING THE FUNCTIONAL
`CAPABILITIES FOR WIRELESS
`COMMUNICATIONS BETWEEN A BASE UNIT
`AND A REMOTE UNIT
`
`5
`
`15
`
`30
`
`5,267,244
`2
`posed of the measuring time, the transmission time and
`the application time results in large degradation. Also,
`the amount of message rate that needs to be allocated
`for power control is sometimes large which results in a
`loss of capacity.
`SUMMARY OF THE INVENTION
`In the present invention a method and apparatus for
`establishing a wireless communication link between a
`base unit and a remote unit is disclosed. The base unit
`has a first set of functional capabilities. The remote unit
`has a second set of functional capabilities. The method
`comprises the steps of transmitting periodically a sync
`signal in a first selected time period in a selected fre
`quency channel by the base unit. The remote unit scans
`to detect the clock signal. The remote unit transmits a
`response signal in the select frequency channel in re
`sponse to the detection of the sync signal, in a second
`selected time period, different from the first selected
`time period. A first control signal encoded by a first
`code is transmitted by the remote unit in the selected
`frequency channel, in a third selected time period differ
`ent from the first and second selected time periods. The
`first control signal contains the set of functional capabil
`ities of the remote unit. The first control signal is re
`ceived by the base unit. The first control signal is de
`coded by the base unit to derive the functional capabili
`ties of the remote unit. The functional capabilities of the
`remote unit is compared to the functional capabilities of
`the base unit, by the base unit, to determine a common
`set of functional capabilities. A second control signal is
`transmitted by the base unit in the selected frequency
`channel, encoded by the first code, in a fourth selected
`time period, different from the first, second and third
`selected time periods. The second control signal con
`tains the common set of functional capabilities. Commu
`nication between the base unit and the remote unit is
`thereafter based upon a functional capability from the
`COO Set.
`The present invention also discloses an apparatus for
`establishing the wireless communication link between
`the base unit and the remote unit.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block level diagram of a base unit of the
`present invention.
`FIG. 2 is a block level diagram of a remote unit of the
`present invention.
`FIG. 3 is a detailed block level diagram of the RF/IF
`analog portion of the base unit shown in FIG. 1.
`FIG. 4 is a detailed block level diagram of the RF/IF
`analog portion of the remote unit shown in FIG. 2.
`FIGS. 5(a-c) are portions of the block level diagram
`of the standby and sync unit of the remote unit shown in
`FIG. 2 and the base unit shown in FIG. 1.
`FIG. 6 is a detailed block level diagram of the inter
`face and multiplexer portion of the remote unit shown
`in FIG. 2 and of the base unit shown in FIG. 1.
`FIG. 7 is a detailed block level diagram of the appli
`cation controller portion of the remote unit shown in
`FIG. 2 and of the base unit shown in FIG. 1.
`FIG. 8 is a schematic diagram of the frequency spec
`trum in which the preferred embodiment of the commu
`nication system of the present invention is intended to
`operate.
`FIG. 9 is a timing diagram of the protocol of commu
`nication between the base unit and the remote unit.
`
`TECHNICAL FIELD
`The present invention relates to a method and an
`10
`apparatus to establish a wireless communication link
`between a base unit having a first set of functional capa
`bilities and one or more remote units having a second
`set of functional capabilities. More particularly, the
`present invention relates to a digital cordless phone for
`communication between a base unit thereof and one or
`more of its associated remote units.
`BACKGROUND OF THE INVENTION
`Wireless communication between a base unit and one
`20
`or more remote units is well known in the art. One well
`known method is Frequency Division Multiple Access
`(FDMA). In FDMA, the available electromagnetic
`communication spectrum is divided into a plurality of
`frequency channels. Communication between the base
`unit and one of the remote units is effected over one of 25
`the frequency channels. Communication between the
`base unit and a different remote unit is effected over a
`different frequency channel.
`Time Division Multiple Access (TDMA) is also well
`known in the art. In TDMA communication, transmis
`sion between the base unit and a first remote unit is
`effected over a first "slice' in time. Transmission be
`tween the base unit and a second remote unit is effected
`over a second "slice' of time, different from the first
`"slice'.
`35
`Finally, in Code Division Multiple Access (CDMA)
`the communication between a base unit and one or more
`remote units is accomplished through spread spectrum
`transmission over a frequency range wherein a unique
`Pseudo Noise (PN) code distinguishes the communica
`tion between a base unit and a first remote unit and a
`different code distinguishes the communication be
`tween the base unit and a different remote unit. There
`are several types of CDMA systems such as Direct
`Sequence, Frequency Hopping, and Time-Hopping.
`45
`Direct Sequence spread spectrum systems encode a low
`rate data stream into a high rate data stream at the trans
`mitter. At the receiver the high rate data stream is de
`coded back into the low rate data stream.
`Establishment of protocol between a remote unit and
`50
`a base unit prior to the communication session is well
`known in the modem communication art. Thus, for
`example, in packet communications, prior to the com
`munication session in accordance with the X.25 proto
`col the remote unit and the base unit negotiate the
`55
`packet size. In addition, in the modem communication
`art, modems having different transmission rate capabili
`ties determine, prior to the communication session, the
`fastest speed at which both units can accommodate one
`another.
`In the prior art, it is known that the transmit power
`can be adjusted based on a priori knowledge of the
`transmitted power and the expected received power by
`the other side. However, this prior art is normally lim
`ited in that it assumes a fixed channel attenuation.
`65
`In the prior art, it is also known to command adjust
`the dynamic power control by using a feedback loop.
`However, for a TDMA system, the delay that is com
`
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`O
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`15
`
`5,267,244
`3
`4.
`at least one combination of voice/data processor 38a
`FIG. 10 is a detailed timing diagram of FIG. 9, show
`and its associated base band processing unit 28a. In the
`ing the portion transmitted by the base unit.
`FIG. 11 is a detailed timing diagram of FIG.9, show
`base unit 10, there are as many voice/data processors
`ing the portion transmitted by the remote unit.
`38a and its associated base band processing unit 28a as
`there are the number of remote units 40 which is or are
`DETAILED DESCRIPTION OF THE
`served simultaneously by the base unit 10. Thus, if the
`DRAWINGS
`base unit 10 is adapted to service three (3) remote units
`Referring to FIG. 1 there is shown a block level
`40 simultaneously, then within the transceiver 30 are
`diagram of a base unit 10. The base unit 10 is adapted to
`three voice/data processors 38 each with its associated
`base band processing unit 28.
`communicate with one or more remote units 40 shown
`in FIG.2. In the preferred embodiment, collectively the
`Each of the voice/data processors 38 is connected
`base unit 10 and the remote unit 40 comprise a digital
`with its associated base band unit 28. The voice data
`cordless phone 8. Thus, the base unit 10 has an interface
`processor 38 is also connected to the interface and mul
`12 for connection with a public switch telephone net
`tiplexer 18 and with the protocol and control unit 32.
`The base band processing unit 28 is connected to the
`work (PSTN) such as an RJII jack or an ISDN inter
`RF/IF analog unit 36 and with the protocol and control
`face.
`The pSTN portion of the interface 12 handles PSTN
`unit 32.
`telephone actions, such as on/off hook, multi-tone gen
`The RF analog unit 36 is connected to the standby
`eration etc. The signals received by the interface 12 are
`and sync unit 34. In addition, the RF/IF unit 36 is con
`sent to the interface and multiplexer 18 and to the appli
`nected to a pair of antenna 26a, and 26b, with each of
`the antennas 26a and 26b serving to both transmit and
`cation controller 22.
`The ISDN portion of the interface 12 translates
`receive.
`ISDN messages into corresponding signals such as on/-
`Finally, the protocol and control unit 32 is connected
`to the application controller 22.
`off hook echo, DTMF tone echo, dial tone or signaling
`messages such as ringing.
`The remote unit 40 is shown in block diagram form in
`FIG. 2. The remote unit 40 comprises a phone/terminal
`The base unit 10 is hardwired to communicate with
`the telephone switching network and communicates
`42 which comprises a handset and an interface terminal
`wirelessly with one or more remote units 40. The base
`to receive data. The phone terminal 42 is connected to
`unit 10 also comprises a speaker phone terminal 14.
`an interface and multiplexer 44 which is similar to the
`Thus, with a speaker phone terminal 14, the base unit 10
`interface and multiplexer 18 of the base unit. The re
`mote unit also comprises a handset panel 46. The hand
`can also be used to communicate directly with the tele
`phone network through the PSTN/ISDN interface 12
`set panel 46 has lights and switches. The handset panel
`or wirelessly with one or more remote units 40. In addi
`46 communicates with an application controller 22
`tion, the base unit 10 comprises a data terminal interface
`which is similar to the application controller 22 in the
`16 for receiving digital data for communication to the
`base unit 10, Similar to the base unit 10, the application
`telephone network over the PSTN/ISDN interface 12
`control 22 is connected to the interface and multiplexer
`or wirelessly with one or more remote units 40. Thus,
`44.
`for example, data from sources such as a computer, can
`The remote unit 40 also comprises a remote unit
`be supplied to the base unit 10 at the data terminal inter
`transceiver 50. The remote unit transceiver 50, similar
`to the base unit transceiver 30, comprises a protocol and
`face 16 for transmission and reception over the tele
`40
`phone network through the PSTN/ISDN interface 12
`control unit 52 which is similar to the protocol and
`or wirelessly with one or more remote units 40.
`control unit 32 of the base unit 10.
`The PSTN/ISDN interface 12, the speaker phone
`The remote unit transceiver 50 also comprises a
`standby and sync unit 34, which is same as the standby
`terminal 14 and the data terminal interface 16 are all
`connected to an interface and multiplexer 18. The inter
`and sync unit 34 of the base unit 10. The remote unit
`face and multiplexer 18, shown in greater detail in FIG.
`transceiver 50 also comprises an RF/IF analog unit 56,
`6, serves to interface the various signals received from
`which is similar to the RF/IF analog 36 of the base unit
`the speaker phone terminal 14 and the data terminal 16
`transceiver 30, and is connected to a transmitting and
`and places them on the telephone network through the
`receiving antenna 58a and a receiving antenna 58b.
`The remote unit transceiver 50 also comprises a sin
`PSTN/ISDN interface 12 or to be transmitted to one or
`gle voice data processor 38a and its associated base
`more of the remote units 40.
`The base unit 10 also comprises a panel 20 comprising
`band processing unit 28a. The voice/data processor 38
`of lights and switches, and a keypad. The signals from
`and its associated base band processing unit 28a are
`the panel 20 are supplied to an application controller 22
`same as the voice/data processor 38a and its associated
`and the signals from the application controller are sup
`base band processing unit 28a of the base unit trans
`55
`plied to the panel 20. The application controller 22 is
`ceiver 30.
`The remote unit transceiver 50 thus comprises a pro
`shown in greater detail in FIG. 7.
`The application controller 22 interfaces with the
`tocol and control unit 52, a standby and sync unit 34, an
`interface and multiplexer 18. The function of the appli
`RF/IF analog unit 56, a voice/data processor 38a and a
`base band processing unit 28a. The connection of these
`cation controller 22 is to interface with the user of the
`system 8, to interpret the user commands, entered from
`units is identical to the connection for the components
`the panel 20, and to provide responses from the system
`of the base unit transceiver 30. The protocol and con
`trol unit 52 is connected to the application controller 22
`8 to the user.
`The interface and multiplexer 18 and the application
`and to the voice/data processor 38a and the base band
`unit 28a, and to the standby and sync unit 34. The voi
`controller 22 communicate with the base unit trans
`65
`ceiver 30. The base unit transceiver 30 comprises a
`ce/data processor 38a is connected to the base band
`processing unit 28a and to the interface and multiplexer
`system clock 35, a protocol and control unit 32, a
`standby and sync unit 34, an RF/IF analog unit 36, and
`44. The base band processing unit 28a is connected to
`
`50
`
`25
`
`35
`
`45
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`5,267,244
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`6
`the RF/IF analog unit 56. The RF/IF analog unit 56 is
`signal supplied from the temperature compensated crys
`connected to the standby and sync unit 34 and to the
`tal oscillator 82. The output of the IFI/Q demodulator
`78b is supplied to the RRC MF circuit 80b.
`antennas 58a and b,
`Referring to FIG. 3 there is shown a detailed block
`In the transmission phase, the t1 binary signals cor
`diagram of the RF/IF analog unit 36 of the base unit
`responding to the in-phase and quadrature-phase con
`ponents of the "spread' data signal (to be described in
`transceiver 30. The function of the RF/IF analog unit
`36 is to convert the frequency of the transmitted or
`greater detail hereinafter) are supplied to the RRC filter
`received signal by the antenna 26a and 26b from radio
`84. The RRC 84 serves to generate a positive or nega
`frequency to an intermediate frequency. In addition, the
`tive root raised cosine signal if the input signal is a +1
`unit 36 has power control capability to control the
`or -1 respectively. The output of the RRC filter 84 is
`transmission power of the transmitted signal. Finally,
`supplied to an RFI/Q modulator 86. The RFI/Q mod
`the unit 36 modulates and demodulates the in-phase and
`ulator 86 takes the root raised cosine signal and directly
`quadrature-phase components of the base band signal.
`converts it into a radio frequency modulated signal for
`transmission. The output of the frequency synthesizer
`The unit 36 is shown as comprising two sets of anten
`nas 26a and 26b both for transmitting and for receiving.
`74 which determines the selected radio frequency signal
`15
`The use of two antennas 26(a and b) and two sets of
`to be modulated and the output of the TCXO 82 which
`matching circuits is to insure that in case one antenna is
`determines the RF frequency of the modulation are
`located in a "dead spot' that the other antenna would
`both supplied to a mixer 88. The output of the mixer 88
`receive and transmit the requisite signals to the remote
`is then supplied to the RF I/O modulator 86 and is
`unit 40. The signal received by one of the antennas 26a
`modulated by the output of the RRC filter 84.
`20
`is supplied to an RF filter and low noise amplifier
`The output of the RFI/Q modulator 86 is then sup
`plied to an RF filter and amplifier 90, whose amplifica
`(LNA) 70a, which functions to filter and amplify the
`signal received from the antenna 26a. The output of the
`tion portion has a gain which is controlled by the gain
`control signal. The output of the RF filter and amplifier
`RF filter and LNA 70a is supplied to an RF-to-IF down
`90 is supplied to the RF linear amplifier 92a for trans
`converter 72a. The function of the RF-to-F down
`25
`converter 72a is to convert the received RF signal into
`mission over the antenna 26b. In addition, the output of
`an intermediate frequency signal. The conversion from
`the RF filter and amplifier 90 is supplied after a delay of
`RF-to-IF is dependent upon the difference frequency
`"chip' time Tc, by a delay 94, to a second RF linear
`supplied to the RF-to-IF down converter 72a. This
`amplifier 92b for transmission over the antenna 26a.
`difference frequency is generated by a frequency syn
`Since two signals are produced (one delayed from the
`30
`thesizer 74 based upon a frequency select input signal.
`other), the signals can be received by the remote unit 40
`From the RF-to-IF down converter 72a, the interme
`and combined. Further, since the two signals are de
`diate frequency is then supplied to an IF filter and am
`layed, this permits the remote unit 40 to receive both
`signals using only a single antenna.
`plifier 76a. The function of the IF filter and amplifier
`76a is to filter the received IF signal and to amplify that
`The frequency synthesizer 74 generates a difference
`35
`signal. In addition the IF filter and amplifier 76a in
`frequency between the RF and IF frequencies. The
`difference frequency varies depending upon the fre
`creases the gain of the filtered signal based upon a gain
`control signal supplied thereto.
`quency select signal supplied to the synthesizer 74.
`The amplified and filtered IF signal is then supplied
`Thus, the frequency synthesizer 74 covers all frequency
`bands. In the event the synthesizer 74 can generate both
`to an I/O demodulator 78a. The I/O demodulator 78a is
`an in-phase and quadrature-phase demodulator and
`the difference frequency (supplied to the RF to IF con
`generates as its output thereof a base band frequency
`verter 72) and the selected RF frequency for transmis
`signal. The demodulation of the input signal is based
`sion, and is able to switch rapidly between those signals,
`upon a IF frequency signal supplied from a temperature
`then the mixer 88 is not required. In that event, the
`compensated crystal oscillator 82. The base band fre
`selected RF frequency output of the synthesizer 74 can
`45
`quency signal is then supplied to an RRC MF 80a. The
`be supplied directly to the RFI/Q modulator 86.
`RRC MF 80a is a root raised cosine signal matched
`Referring to FIG. 4, there is shown in detailed block
`filter whose output, in the absence of carrier phase
`level diagram the RF/IF analog unit 56 of the remote
`error, is a positive or a negative impulse signal for each
`transceiver unit 50. Similar to the RF/IF analog unit 36,
`of the in-phase and quadrature-phase components of the
`the RF/IF analog unit 56 comprises an antenna 58a or
`50
`signal. The in-phase and quadrature-phase components
`58b for receiving the incoming signal. The received
`comprises a complex signal.
`signal is supplied to an RF filter and low noise amplifier
`Similarly, the signal from the antenna 26b is supplied
`70 which serves to filter and amplify the received RF
`along a second identical circuit. First, the signal from
`signal. From the RF filter and LNA circuit 70, the
`the antenna 26b is supplied to an RF filter and a LNA
`signal is . supplied to a RF-to-IF down converter 72.
`55
`circuit 70b. The output of the RF filter and LNA circuit
`The RF-to-IF down converter 72 converts the received
`70b is supplied to an RF-to
`RF signal into an intermediate frequency signal based
`upon the difference frequency signal generated by the
`IF down converter 72b. The difference frequency
`generated by the frequency synthesizer 74 is supplied to
`frequency synthesizer 74. The difference frequency
`signal generated by the frequency synthesizer 74 can be
`the RF-to-IF down converter 72b. The output of the
`selected by a frequency select signal. From the RF-to
`RF-to-IF down converter 72b is supplied to an IF filter
`and amplifier 76b, whose gain is also controlled by the
`IF down converter 72, the IF signal generated thereby
`same gain control signal, supplied to the IF filter and
`is supplied to an IF filter and amplifier 76, whose gain is
`amplifier 76a.
`controlled by again control signal. The output of the IF
`The signal from the IF filter and amplifier 76b is then
`filter and amplifier 76 is then supplied to an IF I/Q
`65
`in-phase and quadrature-phase denodulated by the IF
`demodulator 78.
`I/Q demodulator 78b. The in-phase and quadrature
`The IF I/O demodulator 78 also receives a IF fre
`quency signal generated by the temperature compen
`phase demodulation is based upon the IF frequency
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`IPR2020-00038
`MM EX1023, Page 11
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`5,267,244
`7
`8
`which is earlier in phase, by half a "chip" time Tc, than
`sated crystal oscillator 82. The demodulated in-phase
`and quadrature-phase signals from the IFI/Q demodu
`the code selected by the code select signal and is Sup
`plied to a first complex multiplier 122a. The PN code
`lator 78 are then supplied to an RRC matched filter 80.
`The output of the RRC matched filter 80, in the absence
`generator 134 also generates a code which is later in
`of carrier phase error, are positive or negative impulses 5
`phase, by half a "chip' time Tc, than the one selected by
`representing a til binary signal for each of the in-phase
`the code select signal and is supplied to the second
`and quadrature-phase components of the signal.
`complex multiplier 122b.
`The transmission portion of the RF/IF analog unit 56
`The output of the RRC matched filter circuit 80 is
`receives the "spread” signal from the base band process
`supplied to the first and second complex multipliers
`ing unit 28a. The signal is supplied to the RRC filter 84, 10
`122a and 122b respectively. The outputs of the complex
`The output of the RRC filter 84 which is generated in
`multipliers 122a and 122b are supplied to low pass filters
`response is a positive or negative root raised cosine
`124a and 124b respectively. The outputs of the low pass
`signal to a til binary in-phase or quadrature-phase
`filters 124a and 124b are supplied to energy detection
`component of the "spread" signal. The output signal of
`circuits 126a and 126b respectively. The low pass filter
`the RRC filter 84 is supplied to an RF I/Q modulator 15
`and the energy detection circuit 126 (a and b) function
`86. The output of the oscillator 82 and of the frequency
`to obtain the signal magnitude from the in-phase and
`synthesizer 74 are both supplied to a mixer 88 which
`quadrature-phase components. The output of the en
`generates the requisite RF modulation signal which is
`ergy detection circuits 126a and 12.6b are supplied to a
`supplied to the RFI/Q modulator 86. Thus, the output
`comparator 128. The output of the comparator 128 is a
`of the RFI/Q modulator 86 is an RF modulated signal
`difference signal and is supplied to a loop filter 130. The
`which is supplied to an RF filter and amplifier 90. The
`enable signal from the verification unit 100 is also sup
`RF filter and amplifier 90 has a amplifier whose gain is
`plied to the loop filter 130. The loop filter is activated
`controlled by the gain control signal. The output of the
`when the enable signal is high. The output of the loop
`RF filter and amplifier 90 is supplied to the RF linear
`filter 130 is supplied to a controlled clock 132 which is
`amplifier 92 which is then supplied to a transmitting 25
`then supplied back to the PN code generator 134. In this
`antenna 58b for transmission.
`manner, the PN code generator 134 is maintained in a
`Referring to FIGS. 5(a-c) there is shown detailed
`synchronized state by a delay locked loop. The low pass
`schematic block level diagram of the standby and sync
`filters 124 (a and b) have a bandwidth around the bit
`unit 34. The standby and sync unit 34 comprises a por
`rate and may be implemented as an integrate and dump
`tion which acquires and verifies the signal (FIG. 5a) 30
`circuit. An integrate and dump circuit is a simple imple
`synchronizes the signal (FIG.5b) and detects the signal
`mentation of a low pass filter. The controlled clock 132
`(FIG. 5c).
`also drives a system clock 35.
`Referring to FIG. 5a there is shown the acquisition
`Referring to FIG. 5c there is shown a modulating and
`and verification portion 100 of the standby and synchro
`demodulating portion 140 of the standby and sync unit
`nization unit 34. The acquisition and verification unit 35
`34. The modulator and demodulator portion 140 re
`100 comprises a preamble matched filter 102 which
`ceives the signal from the RRC matched filter circuit
`receives as its input thereof, the output of the RRC MF
`80. The signal is supplied to a first complex multiplier
`circuit 80. The function of the preamble matched filter
`142a. The output of the PN code generator 134 is also
`circuit 102 is to detect the preamble portion of SYNC
`supplied to the first complex multiplier 142a. The out
`signal generated by the base unit 34 or the preamble 40
`put of the first complex multiplier 142a is supplied to a
`portion of the PA1 signal generated by the remote unit
`first low pass filter 144a. From the first low pass filter
`(discussed in greater detail hereinafter). The output of
`144a, the signal is supplied to a first one bit delay 146a.
`the preamble matched filter circuit 102 is supplied to an
`The output of the first one bit delay 146a is supplied to
`energy detection circuit 104. The energy detection cir
`a first conjugate multiplier 148a to which the output of
`cuit 104 serves to obtain the signal magnitude from the 45
`the first low pass filter 144a is also supplied. The output
`in-phase and quadrature-phase components. The output
`of the first conjugate multiplier 148a is supplied to a
`of the energy detection circuit 104 is supplied to a
`multipath combiner 150. From the multipath combiner
`threshold detection circuit 106. The threshold detection
`150, the signal is supplied to a threshold detector 152
`circuit 106 serves to detect the presence or absence of
`which generates the binary data signal.
`the preamble signal. Typically the threshold is first high 50
`The signal from the RRC MF circuit 80 is also sup
`to prevent false detection and then lowered to increase
`plied to a second path comprising of a second complex
`the probability of detection. The output of the threshold
`multiplier 142b which is also supplied with the output of
`detection circuit 106 is supplied to a verification counter
`the PN code generator 134. The output of the second
`108. The verification counter 108 can optionally be fed
`complex multiplier 142b is supplied to a second low pass
`back to the threshold detection circuit to control the 55
`filter 144b. The output of the second low pass filter 144b
`threshold detection circuit in a feedback loop. The out
`is supplied to a second one bit delay 146b. The output of
`put of the verification counter 108 is an enable signal,
`the one bit delay 146b is supplied to a second conjugate
`which is used in the other components of the stand-by
`multiplier 148b to which the output of the second low
`and sync unit 34. In the event the signal received by the
`pass filter 144b is also supplied. The output of the sec
`RF/IF analog unit 36 or 56 is the correct signal, the 60
`ond conjugate multiplier 148b is supplied to the multi
`enable signal would be high.
`Referring to FIG. 5b there is shown the synchroniza
`path combiner 150. In the case where the standby and
`tion portion 120 of the standby and synchronization unit
`sync unit 34 is used with the RF/IF analog unit 36 of
`34. The synchronization portion 120 compr