United States Patent
`Su et al.
`
`[19]
`
`-
`
`llllllllllllllllllllllIlllllllllIIIIIIIIIIIllllllllllllllllllllllllllllllll
`U5005258995A
`
`[11] Patent Number:
`
`[45] Date of Patent:
`
`5,258,995
`NOV. 2, 1993
`
`[54] WIRELESS COMMUNICATION SYSTEM
`
`[75]
`
`Inventors: Chun-Meng Su, Lafayette; Saman
`Behtash, Berkeley; Keith Jarett,
`Oakland; Huihung Lu, Danville;
`Christopher Flores, Oakland; David
`G. Messerschmitt, Moraga, all of
`Calif.
`
`[73] Assignee:
`
`Teknekron Communications Systems,
`Inc., Berkeley, Calif.
`
`[21] Appl. No.: 789,292
`
`[22] Filed:
`
`Nov. 8, 1991
`
`[51]
`Int. Cl.5 .................................... H04K 1/00
`
`[52] US. Cl. ........................... 375/1
`[58] Field of Search ...........................
`375/1; 380/34
`[56]
`References Cited
`U.S. PATENT DOCUMENTS
`
`...................... 375/1
`
`6/1981 Goodman et al.
`4,271,524
`4,644,560 2/1987 Torre et al-.
`.
`........................ 375/1
`4,703,474 10/ 1987 Foschini et al.
`4,783,844 11/1988 Higashiyma et al.
`.
`4,905,221
`2/1990 Ichiyoshi
`.
`............................ 375/1
`5,099,493 3/1992 Zeger et al.
`5,103,459 4/1992 Gilhousen et al.
`.
`375/1
`
`5,128,959
`7/1992 Bruckert
`2375/]
`
`5,136,612
`8/1992 Bi
`...........
`375/1
`
`5,150,377 9/1992 Vannucci
`375/1
`5,151,919
`9/1992 Dent ...........
`375/1
`
`5,161,168 11/1992 Schilling
`375/1
`5,164,958 11/1992 Omura ............
`375/1
`
`5,193,101
`3/1993 McDonald et al.
`.................... 375/1
`
`OTHER PUBLICATIONS
`
`38th IEEE Vehicular Technology Conference, Jun.
`1988, “Variable—Rate Sub—Band Speech Coding and
`Matched Channel Coding for Mobile Radio Channels”,
`
`by J. Hagensuer, N. Seshandri C-E. W. Sundberg, pp.
`139—146.
`
`IEEE Transactions on Communications, vol. 38, No. 7,
`Jul. 1990, “The Performance of Rate—Compatible Punc-
`tured Convolutional Codes for Digital Mobile Radio”,
`C.-—E. W. Sundberg, J. Hagenauer, N. Seshandri, pp.
`966-980.
`
`IEEE Transactions on Communications, vol. COM-32,
`No. 3, Mar. 1934, “High—Rate Punctured Convolu-
`tional Codes for Soft Decision Viterbi Decoding”, Y.
`Yasuda, K. Kashiki, Y. Hirata, pp. 315—319.
`IEEE Transactions on Communications, vol. 36, No. 4,
`Apr. 1988, “Rate-Compatible Punctured Convolutional
`Codes (RCPC Codes) and their Applications”,
`.1.
`Hagenauer, pp. 389—400.
`
`Primary Examiner—Salvatore Cangialosi
`Attorney, Agent, or Firm—Limbach & Limbach
`
`[57]
`
`ABSTRACT
`
`In the present invention a wireless communication sys-
`tem is disclosed. A base unit communicates with a re-
`mote unit. The system comprises means for transmit-
`ting, using CDMA, between the base unit and the re-
`mote unit, in one of a plurality of frequencies channels
`selected. In one period of time, the base unit transmits
`and in another period of time, different from the one
`period, the remote unit transmits. Further, the system
`comprises means for changing the one frequency chan-
`nel selected to another frequency channel, different
`from the one frequency channel, in response to interfer-
`ence in the one frequency channel. Thus, communica-
`tion between the base unit and the remote unit is then
`affected over the another frequency channel.
`
`20 Claims, 7 Drawing Sheets
`
`VOICE/DATA
`PROCESSOR
`
`BASEBAND
`PROCESSING
`
`UNIT (BPU)
`
`ANALOG
`UNIT
`
`VOICE/DATA
`PROCESSOR
`
`UNIT (PCU)
`
`PSTN/ISDN
`INTERFACE
`
`SPEAKER
`PHONE
`TERMINAL
`
`INTERFACE
`AND
`MULTIPLEXER
`
`..1
`APPLICATION
`CONTROLLER
`
`GAIN
`FREQ. CODE
`SEL
`SEL CONTROL
`_J
`l
`__J_
`TR
`
`PROTOCOL AND CON
`
`01
`
`STAND—BY
`AND
`SYNC. UNIT
`
`34
`
`Page 1 of 19
`
`SAMSUNG EXHIBIT 1015
`
`Page 1 of 19
`
`SAMSUNG EXHIBIT 1015
`
`

`

`US. Patent
`
`Nov. 2, 1993
`
`Sheet 1 of 7
`
`5,258,995
`
`
`
`ozamaoE$5329,
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`Page 2 of 19
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`Page 2 of 19
`
`
`

`

`US. Patent
`
`Nov. 2, 1993
`
`Sheet 2 of 7
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`5,258,995
`
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`Page 3 of 19
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`Page 3 of 19
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`
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`
`
`
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`
`

`

`US. Patent
`
`Nov. 2, 1993
`
`Sheet 3 or 7
`
`5,258,995
`
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`Page 4 of 19
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`Page 4 of 19
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`5,258,995
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`
`Page 5 of 19
`
`Page 5 of 19
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Nov. 2, 1993
`
`Sheet 5 of 7
`
`5,258,995
`
`1240
`
`1260
`
`
`
`1/0 (30050 DATA
`(T0 RRC FILTER)
`
`FIG. 50
`
`DATA
`
`
`ENARY
`
`160
`
`Page 6 of 19
`
`Page 6 of 19
`
`

`

`US. Patent
`
`Nov. 2, 1993
`
`Sheet 6 Of 7
`
`5,258,995
`
`INTERFACE AND MULTTPLEXER
`
`MULTTPLEXER
`
`SWITCH MATRIX
`
`
`
`
`PSTM/ISDM
`
`DATA TERM
`
`SPEAKER
`
`PHONE
`
`TERMINAL
`
`
`
`I. V I
`
`-—
`
`”DP
`
`
`
`
`
`
`
`APPLICATTONS
`CONTROLLER
`
`FIG. 6
`
`
`APPUCATIONS -
`
`' PROCESSOR
`
`
`
`
`INTERFACE
`
`AND
`
`‘
`
`MULTTPLEXER
`
`PROTOCOL AND
`CONTROL UNIT
`
`FIG. 7
`
`PANEL
`
`Page 7 of 19
`
`Page 7 of 19
`
`

`

`US. Patent
`
`Nov. 2, 1993
`
`'
`
`Sheet 7 of7
`
`5,258,995
`
`.3 MHz
`
`I
`
`I
`
`902 MHz
`
`I
`
`I
`
`. . .
`
`I
`
`l
`
`928 MHz
`
`
`
`XMIT BY BASE 10 m BY EACH REMOTE 4o
`
`'
`
`FIG. 9
`
`SYNC
`
`USC—B
`
`r—-—~——-\
`
`F—k"
`
`I/2
`u____~______2
`
`
`CSC—B
`
`UC-B
`
`FIG. 10
`
`UC-R
`CSC—R
`W f—__'—’~__‘\
`
`2-_2.---2
`
`FIG.
`
`11
`
`Page 8 of 19
`
`Page 8 of 19
`
`

`

`1
`
`5,258,995
`
`2
`
`WIRELESS COMMUNICATION SYSTEM
`
`SUMMARY OF THE INVENTION
`
`TECHNICAL FIELD
`
`The present invention relates to a wireless communi-
`cation system for communicating between a base unit
`and a remote unit, and more particularly to a wireless
`communication system for communication between a
`base unit portion and a remote unit portion of a digital
`cordless phone.
`
`BACKGROUND OF THE INVENTION
`Wireless communication between a base unit and one
`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
`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”.
`
`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.
`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
`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 X25 proto-
`col the remote unit and the base unit negotiate the
`packet size. In addition, in the modern 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.
`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-
`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.
`
`5
`
`IO
`
`15
`
`A wireless communication system for communica-
`tion between a base unit and one or more remote units
`is disclosed. The system comprises means for transmit-
`ting, using CDMA, between the base unit and the re-
`mote unit in one of a plurality of frequency channels
`selected, wherein in one period of time the base unit
`transmits and in another period of time different from
`the one period, the remote unit transmits. The system
`also comprises means for changing the one frequency
`channel selected to another frequency channel, differ-
`ent from the one frequency channel,
`in response to
`interference in the one frequency channel, whereby the
`communication between the base unit and the remote
`unit is then affected over the another frequency chan-
`nel.
`
`The present invention also relates to a wireless com-
`munication method for communicating between a base
`unit and one or more remote units.
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`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.
`FIG. 10 is a detailed timing diagram of FIG. 9, show-
`ing the portion transmitted by the base unit.
`FIG. 11 is a detailed timing diagram of FIG. 9, show-
`ing the portion transmitted by the remote unit.
`DETAILED DESCRIPTION OF THE
`DRAWINGS
`
`Referring to FIG. 1 there is shown a block level
`diagram of a base unit 10. The base unit 10 is adapted to
`communicate with one or more remote units 40 shown
`in FIG. 2. In the preferred embodiment, collectively the
`base unit 10 and the remote unit 40 comprise a digital
`cordless phone 8. Thus, the base unit 10 has an interface
`12 for connection with a public switch telephone net-
`work (PSTN) such as an R111 jack or an ISDN inter-
`face.
`The PSTN portion of the interface 12 handles PSTN
`telephone actions, such as on/off hook, multi-tone gen-
`eration etc. The signals received by the interface 12 are
`sent to the interface and multiplexer 18 and to the appli—
`cation controller 22.
`The ISDN portion of the interface 12 translates
`ISDN messages into corresponding signals such as on/-
`
`Page 9 of 19
`
`Page 9 of 19
`
`

`

`3
`off hook echo, DTMF tone echo, dial tone or signaling
`messages such as ringing.
`The base unit 10 is hardwired to communicate with -
`the telephone switching network and communicates
`wirelessly with one or more remote units 40. The base
`unit 10 also comprises a speaker phone terminal 14.
`Thus, with a speaker phone terminal 14, the base unit 10
`can also be used to communicate directly with the tele-
`phone network through the PSTN/ISDN interface 12
`or wirelessly with one or more remote units 40. In addi-
`tion, the base unit 10 comprises a data terminal interface
`16 for receiving digital data for communication to the
`telephone network over the PSTN/ISDN interface 12
`or wirelessly with one or more remote units 40. Thus,
`for example, data from sources such as a computer, can
`be supplied to the base unit 10 at the data terminal inter-
`face 16 for transmission and reception over the tele-
`phone network through the PSTN/ISDN interface 12
`or wirelessly with one or more remote units 40.
`The PSTN/ISDN interface 12, the speaker phone
`terminal 14 and the data terminal interface 16 are all
`connected to an interface and multiplexer 18. The inter-
`face and multiplexer 18, shown in greater detail in FIG.
`6, serves to interface the various signals received from
`the speaker phone terminal 14 and the data terminal 16
`and places them on the telephone network through the
`. PSTN/ISDN interface 12 or to be transmitted to one or
`more of the remote units 40.
`
`10
`
`15
`
`20
`
`25
`
`5,258,995
`
`4
`Finally, the protocol and control unit 32 is connected
`to the application controller 22.
`The remote unit 40 is shown in block diagram form in
`FIG. 2. The remote unit 40 comprises a phone/terminal
`42 which comprises a handset and an interface terminal
`to receive data. The phone terminal 42 is connected to
`an interface and multiplexer 44 which is similar to the
`interface and multiplexer 18 of the base unit. The re-
`mote unit also comprises a handset panel 46. The hand-
`set panel 46 has lights and switches. The handset panel
`46 communicates with an application controller 22
`which is similar to the application controller 22 in the
`base unit 10. Similar to the base unit 10, the application
`control 22 is connected to the interface and multiplexer
`44.
`
`The remote unit 40 also comprises a remote unit
`transceiver 50. The remote unit transceiver 50, similar
`to the base unit transceiVer 30, comprises a protocol and
`control unit 52 which is similar to the protocol and
`control unit 32 of the base unit 10.
`The remote unit
`transceiver 50 also comprises a
`standby and sync unit 34, which is same as the standby
`and sync unit 34 of the base unit 10. The remote unit
`transceiver 50 also comprises an RF/IF analog unit 56,
`which is similar to the RF/IF analog 36 of the base unit
`transceiver 30, and is connected to a transmitting and
`receiving antenna 580 and a receiving antenna 58b.
`The remote unit transceiver 50 also comprises a sin—
`gle voice data processor 380 and its associated base
`band processing unit 28a. The voice/data processor 38
`and its associated base band processing unit 2811 are
`same as the voice/data processor 38a and its associated
`base band processing unit 28a of the base unit trans-
`ceiver 30.
`
`The remote unit transceiver 50 thus comprises a pro-
`tocol and control unit 52, a standby and sync unit 34, an
`RF/IF analog unit 56, a voice/data processor 380 and a
`base band processing unit 28a. The connection of these
`units is identical to the connection for the components
`of the base unit transceiver 30. The protocol and con-
`trol unit 52 is connected to the application controller 22
`and to the voice/data processor 38a and the base band
`unit 28a, and to the standby and sync unit 34. The voi-
`ce/data processor 38a is connected to the base band
`processing unit 28:: and to the interface and multiplexer
`44. The base band processing unit 28a is connected to
`the RF/IF analog unit 56. The RF/IF analog unit 56.is
`connected to the standby and sync unit 34 and to the
`antennas 58a and b.
`Referring to FIG. 3 there is shown a detailed block
`diagram of the RF/IF analog unit 36 of the base unit
`transceiver 30. The function of the RF/IF analog unit
`36 is to convert the frequency of the transmitted or
`received signal by the antenna 260 and 26b from radio
`frequency to an intermediate frequency. In addition, the
`unit 36 has power control capability to control the
`transmission power of the transmitted signal. Finally,
`the unit 36 modulates and demodulates the in-phase and
`quadrature-phase components of the base band signal.
`The unit 36 is shown as comprising two sets of anten-
`nas 26a and 2617 both for transmitting and for receiving.
`The use of two antennas 26(a and b) and two sets of
`matching circuits is to insure that in case one antenna is
`located in a "dead spot” that the other antenna would
`receive and transmit the requisite signals to'the remote
`unit 40. The signal received by one of the antennas 26a
`is supplied to an RF filter and low noise amplifier
`(LNA) 70a, which functions to filter and amplify the
`
`3O
`
`35
`
`45
`
`50
`
`55
`
`The base unit 10 also comprises a panel 20 comprising
`of lights and switches, and a keypad. The signals from
`the panel 20 are supplied to an application controller 22
`and the signals from the application controller are sup-
`plied to the panel 20. The application controller 22 is
`shown in greater detail in FIG. 7.
`The application controller 22 interfaces with the
`interface and multiplexer 18. The function of the appli-
`cation controller 22 is to interface with the user of the
`system 8, to interpret the user commands, entered from
`the panel 20, and to provide responses from the system
`8 to the user.
`
`The interface and multiplexer 18 and the application
`controller 22 communicate with the base unit trans-
`ceiver 30. The base unit transceiver 30 comprises a
`system clock 35, a protocol and control unit 32, a
`standby and sync unit 34, an RF/IF analog unit 36, and
`at least one combination of voice/data processor 3811
`and its associated base band processing unit 28a. In the
`base unit 10, there are as many voice/data processors
`38a and its associated base band processing unit 280 as
`there are the number of remote units 40 which is or are
`served simultaneously by the base unit 10. Thus, if the
`base unit 10 is adapted to service three (3) remote units
`40 simultaneously, then within the transceiver 30 are
`three voice/data processors 38 each with its associated
`base band processing unit 28.
`Each of the voice/data processors 38 is connected
`with its associated base band unit 28. The voice data
`processor 38 is also connected to the interface and mul-
`tiplexer 18 and with the protocol and control unit 32.
`The base band processing unit 28 is connected to the
`RF/IF analog unit 36 and with the protocol and control
`unit 32.
`
`The RF analog unit 36 is connected to the standby
`and sync unit 34. In addition, the RF/IF unit 36 is con-
`nected to a pair of antenna 26a, and 26b, with each of
`the antennas 26a and 2617 serving to both transmit and
`receive.
`
`65
`
`Page 10 of 19
`
`Page 10 of 19
`
`

`

`5
`signal received from the antenna 26a. The output of the
`RF filter and LNA 70a is supplied to an RF-to-IF down
`converter 72a. The function of the RF~to-IF down
`converter 72a is to convert the received RF signal into
`an intermediate frequency signal. The conversion from
`RF-to-IF is dependent upon the difference frequency
`supplied to the RF-to-IF down converter 720. This
`difference frequency is generated by a frequency syn-
`thesizer 74 based upon a frequency select input signal.
`From the RF-to-IF down converter 72a, the interme-
`diate frequency is then supplied to an IF filter and am-
`plifier 76a. The function of the IF filter and amplifier
`76a is to filter the received IF signal and to amplify that
`signal. In addition the IF filter and amplifier 76a in-
`creases the gain of the filtered signal based upon a gain
`control signal supplied thereto.
`The amplified and filtered IF signal is then supplied
`to an I/Q demodulator 78a. The I/Q demodulator 78a is
`an in-phase and quadrature-phase demodulator and
`generates as its output thereof a base band frequency
`signal. The demodulation of the input signal is based
`upon a IF frequency signal supplied from a temperature
`compensated crystal oscillator 82. The base band fre-
`quency signal is then supplied to an RRC MF 80:1. The
`RRC MF 80a is a root raised cosine signal matched
`filter whose output,
`in the absence of carrier phase
`error, is a positive or a negative impulse signal for each
`of the in-phase and quadrature-phase components of the
`signal. The in-phase and quadrature-phase components
`comprises a complex signal.
`Similarly, the signal from the antenna 26b is supplied
`along a second identical circuit. First, the signal from
`the antenna 26b is supplied to an RF filter and a LNA
`circuit 70b. The output of the RF filter and LNA circuit
`70b is supplied to an RF-to-IF down converter 72b. The
`difference frequency generated by the frequency syn-
`thesizer 74 is supplied to the RF-to-IF down converter
`72b. The output of the RF-to-IF down converter 72b is
`supplied to an IF filter and amplifier 76b, whose gain is
`also to the IF filter and amplifier 76a.
`The signal from the IF filter and amplifier 76b is then
`in-phase and quadrature—phase demodulated by the IF
`I/Q demodulator 78b. The in-phase and quadrature-
`phase demodulation is based upon the IF frequency
`signal supplied from the temperature compensated crys-
`tal oscillator 82. The output of the IF I/Q demodulator
`78b is supplied to the RRC MF circuit 80b.
`In the transmission phase, the i1 binary signals cor-
`responding to the in-phase and quadrature-phase com-
`ponents of the “spread" data signal (to be described in
`greater detail hereinafter) are supplied to the RRC filter
`84. The RRC 84 serves to generate a positive or nega—
`tive root raised cosine signal if the input signal is a +1
`or —1 respectively. The output of the RRC filter 84 is
`supplied to an RF I/Q modulator 86. The RF I/Q mod-
`ulator 86 takes the root raised cosine signal and directly
`converts it into a radio frequency modulated signal for
`transmission. The output of the frequency synthesizer
`74 which determines the selected radio frequency signal
`to be modulated and the output of the TCXO 82 which
`determines the RF frequency of the modulation are
`both supplied to a mixer 88. The output of the mixer 88
`is then supplied to the RF I/Q modulator 86 and is
`modulated by the output of the RRC filter 84.
`The output of the RF I/Q modulator 86 is then sup-
`plied to an RF filter and amplifier 90, whose amplifica-
`tion portion has a gain which is controlled by the gain
`control signal. The output of the RF filter and amplifier
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`10
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`5,258,995
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`90 is supplied to the RF linear amplifier 92a for trans-
`mission over the antenna 26b. In addition, the output of
`the RF filter and amplifier 90 is supplied after a delay of
`“chip” time Tc, by a delay 94, to a second RF linear
`amplifier 92b for transmission over the antenna 26a.
`Since two signals are produced (one delayed from the
`other), the signals can be received by the remote unit 40
`and combined. Further, since the two signals are de-
`layed, this permits the remote unit 40 to receive both
`signals using only a single antenna.
`The frequency synthesizer 74 generates a difference
`frequency between the RF and IF frequencies. The
`difference frequency varies depending upon the fre-
`quency select signal supplied to the synthesizer 74.
`Thus, the frequency synthesizer 74 covers all frequency
`bands. In the event the synthesizer 74 can generate both
`the difference frequency (supplied to the RF to IF con-
`verter 72) and the selected RF frequency for transmis-
`sion, and is able to switch rapidly between those signals,
`then the mixer 88 is not required. In that event, the
`selected RF frequency output of the synthesizer 74 can
`be supplied directly to the RF I/Q modulator 86.
`Referring to FIG. 4, there is shown in detailed block
`level diagram the RF/IF analog unit 56 of the remote
`transceiver unit 50. Similar to the RF/IF analog unit 36,
`the RF/IF analog unit 56 comprises an antenna 580 or
`58b for receiving the incoming signal. The received
`signal is supplied to an RF filter and low noise amplifier
`70 which serves to filter and amplify the received RF
`signal. From the RF filter and LNA circuit 70, the
`signal is supplied to a RF-to-IF down converter 72. The
`RF-to-IF down converter 72 converts the received RF
`signal into an intermediate frequency signal based upon
`the difference frequency signal generated by the fre-
`quency synthesizer 74. The difference frequency signal
`generated by the frequency synthesizer 74 can be se-
`lected by a frequency select signal. From the RF-to—IF
`down converter 72, the IF signal generated thereby is
`supplied to an IF filter and amplifier 76, whose gain is
`controlled by a gain control signal. The output of the IF
`filter and amplifier 76 is then supplied to an IF I/Q
`demodulator 78.
`The IF I/Q demodulator 78 also receives a IF fre-
`quency signal generated by the temperature compen-
`sated crystal oscillator 82. The demodulated in-phase
`and quadrature-phase signals from the IF I/Q demodu-
`lator 78 are then supplied to an RRC matched filter 80.
`The output of the RRC matched filter 80, in the absence
`of carrier phase error, are positive or negative impulses
`representing a 1'1 binary signal for each of the in—phase
`and quadrature-phase components of the signal.
`The transmission portion of the RF/IF analog unit 56
`receives the “spread” signal from the base band process-
`ing unit 28a. The signal is supplied to the RRC filter 84.
`The output of the RRC filter 84 is a positive or negative
`root raised cosine signal which is generated in response
`to a :1 binary in-phase or quadrature-phase component
`of the “spread” signal. The output signal of the RRC
`filter 84 is supplied to an RF I/Q modulator 86. The
`output of the oscillator 82 and of the frequency synthe-
`sizer 74 are both supplied to a mixer 88 which generates
`the requisite RF modulation signal which is supplied to
`the RF I/Q modulator 86. Thus, the output of the RF
`I/Q modulator 86 is an RF modulated signal which is
`supplied to an RF filter and amplifier 90. The RF filter
`and amplifier 90 has a amplifier whose gain is controlled
`by the gain control signal. The output of the RF filter
`and amplifier 90 is supplied to the RF linear amplifier 92
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`5,258,995
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`then supplied back to the PN code generator 134. In this
`manner, the PN code generator 134 is maintained in a
`synchronized state by a delay locked loop. The low pass
`filters 124 (a and b) have a bandwidth around the bit
`rate and may be implemented as an integrate and dump
`circuit. An integrate and dump circuit is a simple imple-
`mentation of a low pass filter. The controlled clock 132
`also drives a system clock 35.
`.
`Referring to FIG. 5c there is shown a modulating and
`demodulating portion 140 of the standby and sync unit
`34. The modulator and demodulator portion 140 re-
`ceives the signal from the RRC matched filter circuit
`80. The signal is supplied to a first complex multiplier
`142a. The output of the PN code generator 134 is also
`supplied to the first complex multiplier 142a. The out-
`put of the first complex multiplier 142a is supplied to a
`first low pass filter 144a. From the first low pass filter
`144a, the signal is supplied to a first one bit delay 146a.
`The output of the first one bit delay 146a is supplied to
`a first conjugate multiplier 1480 to which the output of
`the first low pass filter 144a is also supplied. The output
`of the first conjugate multiplier 148a is supplied to a
`multipath combiner 150. From the multipath combiner
`150, the signal is supplied to a threshold detector 152
`which generates the binary data signal.
`The signal from the RRC MF circuit 80 is also sup-
`plied to a second path comprising of a second complex
`multiplier 142b which is also supplied with the output of
`the PN code generator 134. The output of the second
`complex multiplier 142b is supplied to a second low pass
`filter 14412. The output of the second low pass filter 144b
`is supplied to a second one bit delay 146b. The output of
`the one bit delay 146b is supplied to a second conjugate
`multiplier 14817 to which the output of the second low
`pass filter 144b is also supplied. The output of the sec-
`ond conjugate multiplier 14817 is supplied to the multi-
`path combiner 150. In the case where the standby and
`sync unit 34 is used with the RF/IF analog unit 36 of
`the base unit transceiver 30, two paths for the signals
`from the two RRC MF circuits 8011 and 8017 are pro-
`vided. In the event the standby and sync unit 34 is used
`with the RF/IF analog unit 56 of the remote unit trans-
`ceiver 50, the multipath combiner 150 would be used if
`the base unit 10 transmitted two signals delayed from
`one another by a single chip.
`The data detection portion 140 also comprises a dif-
`ferential encoder 160 which receives the binary data
`from the base band processing unit 28a. The output of
`the differential encoder 160 is supplied to a complex
`multiplier 162 to which the PN code generator 134 is
`also supplied. The output of the complex multiplier 162
`is the “spread” signal which is supplied to the RRC
`filter 84 for transmission by the RF/IF analog unit 36 or
`56.
`
`The base band processing unit 28 is similar to the
`standby and sync unit 34 in that it comprises an acquisi-
`tion and verification unit (shown in FIG. 50), a synchro-
`nization unit (shown in FIG. 5b) and a data detection
`unit 140 shown in FIG. 5c. The difference, as will be
`explained hereinafter, is that the base band processing
`unit is operational during the time when the remote unit
`40 is in communication with the base unit 10. In con-
`trast, the standby and sync unit 34 is operational only
`when the remote unit 40 is in the standby mode. Be-
`cause various components of the base band processing
`unit 280 are similar if not identical to the standby and
`sync unit 34, the base band processing unit 28a and the
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`5
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`which is then supplied to a transmitting antenna 58b for
`transmission.
`.
`Referring to FIGS. 5(a-c) there is shown detailed
`schematic block level diagram of the standby and sync
`unit 34. The standby and sync unit 34 comprises a por-
`tion which acquires and verifies the signal (FIG. 5a)
`synchronizes the signal (FIG. 5b) and detects the signal
`(FIG. 5c).
`Referring to FIG. Sa there is shown the acquisition
`and verification portion 100 of the standby and synchro- 10
`nization unit 34. The acquisition and verification unit
`100 comprises a preamble matched filter 102 which
`receives as its input thereof, the output of the RRC MF
`circuit 80. The function of the preamble matched filter
`circuit 102 is to detect the preamble portion of SYNC 15
`signal generated by the base unit 34 or the preamble
`portion of the PA] signal generated by the remote unit
`(discussed in greater detail hereinafter). The output of
`the preamble matched filter circuit 102 is supplied to an
`energy detection circuit 104. The energy detection cir- 20
`cuit 104 serves to obtain the signal magnitude from the
`in-phase and quadrature-phase components. The output
`of the energy detection circuit 104 is supplied to a
`threshold detection circuit 106. The threshold detection
`circuit 106 serves to detect the presence or absence of 25
`the preamble signal. Typically the threshold is first high
`to prevent false detection and then lowered to increase
`the probability of detection. The output of the threshold
`detection circuit 106 is supplied to a verification counter
`108. The verification counter 108 can optionally be fed 30
`back to the threshold detection circuit to control the
`threshold detection circuit in a feedback loop. The out-
`put of the verification counter 108 is an enable signal,
`which is used in the other components of the stand-by
`and sync unit 34. In the event the signal received by the 35
`RF/IF analog unit 36 or 56 is the correct signal, the
`enable signal would be high.
`Referring to FIG. 5b there is shown the synchroniza-
`tion portion 120 of the standby and synchronization unit
`34. The synchronization portion 120 comprises
`a 40
`Pseudo Noise (PN) code generator 134, which receives
`as its input thereof, a code select signal. The PN code
`generator 134 generates a PN code which is determined
`by the code select signal. In addition, it generates a code
`which is earlier in phase, by half a “chip" time Tc, than 45
`the code selected by the code select signal and is sup-
`plied to a first complex multiplier 1220. The PN code
`generator 134 also generates a code which is later in
`phase, by half a “chip” time Tc, than the one selected by
`the code select signal and is supplied to the second so
`complex multiplier 122b.
`The output of the RRC matched filter circuit 80 is
`supplied to the first