US007317894B2
`
`a2) United States Patent
`US 7,317,894 B2
`(10) Patent No.:
`(45) Date of Patent:
`Jan. 8, 2008
`Hirose
`
`
`(54) SATELLITE DIGITAL RADIO BROADCAST
`RECEIVER
`
`(75)
`
`Inventor: Koji Hirose, Setagaya-ku (JP)
`
`(73) Assignee: Kabushiki Kaisha Kenwood, Tokyo
`(JP)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 288 days.
`
`(21)
`
`Appl. No.: 10/781,726
`
`6,301,313 BL* 10/2001 Gevargiz et al. ............ 375/340
`6,484,042 B1* 11/2002 Loke .............
`. 455/234.1
`
`....
`we 455/245 .2
`6,498,927 B2* 12/2002 Kang et al.
`1/2003 Marko et al... 455/428
`6,510,317 B1*
`4/2003 Titlebaum et al.
`.......... 455/427
`6,549,774 B1*
`
`4/2003 Szymansky...........
`. 455/13.1
`6,557,029 B2*
`........... 455/82
`6,584,090 B1*
`6/2003 Abdelganyet al.
`6,735,416 Bl*
`5/2004 Marko et al.
`......
`. 455/3.02
`2001/0022821 A1l*™
`9/2001.
`Ichihara .........
`375/345
`2001/0041532 AL™ 11/2001 Tomasz etal.
`............ 455/3.02
`2002/0025792 A1*
`2/2002 Isoda ............
`455/234.1
`2004/0229583 AL™ 11/2004 Ogino oes 455/3.01
`2005/0124289 Al*
`6/2005 Coffin, III .................. 455/3.02
`2007/0004351 Al*
`1/2007 Dekker .................0.. 455/127.1
`
`
`
`
`(22)
`
`(65)
`
`(30)
`
`Filed:
`
`Feb. 20, 2004
`
`* cited by examiner
`
`Prior Publication Data
`
`US 2004/0168193 Al
`
`Aug. 26, 2004
`
`Primary Examiner—Lana Le
`(74) Attorney, Agent, or Firm—Eric J. Robinson; Robinson
`Intellectual Property LawOffice, P.C.
`
`Foreign Application Priority Data
`
`(57)
`
`ABSTRACT
`
`Feb. 26, 2003
`
`(TP)
`
`eeeeeeeeeeeceeeesereeeees 2003-048572
`
`(51)
`
`(52)
`(58)
`
`(56)
`
`Int. Cl.
`
`(2006.01)
`HO4H 1/00
`US. Ch oe 455/3.02; 455/234.1; 455/250.1
`Field of Classification Search...... 455/3.01-3.02,
`455/234.1, 232.1, 272, 277.1, 277.2, 226.1,
`455/226.2, 67.11, 67.12, 133, 136; 725/68-71,
`725/63—64
`See application file for complete search history.
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,095,533
`5,301,352
`5,319,673
`5,794,138
`5,966,186
`6,078,796
`6,091,931
`
`rrrrprpr> 7
`
`*
`*
`*
`
`3/1992
`4/1994
`6/1994
`8/1998
`* 10/1999
`*
`6/2000
`*
`7/2000
`
`Loper et al. ... 455/249.1
`Nakagawa et al.
`........... 725/71
`
`Briskman ...........
`. 4$5/13.1
`Briskman
`oo... 455/344
`
`
`Shigihara et al.
`.......... 348/570
`Ling... eee
`- 455/234.1
`Ben-Efraim etal. ....... 455/302
`
`A satellite digital radio broadcast receiver has an integrated
`circuit including a first reception series for processing a
`satellite wave signal froma satellite and a second reception
`series for processing a ground wavesignal from a repeater
`in order to receive both the satellite wave signal and the
`ground wavesignal having the same broadcast contents and
`different modulation methods. The receiver has an automatic
`
`gain control unit for amplifying a signal from a single
`antenna at a variable gain amplifier, and in accordance with
`the level of a signal outputted from the variable gain
`amplifier,
`for controlling the gain of the variable gain
`amplifier, and a two-way distributor for distributing an
`output of the automatic control unit
`to two distribution
`outputs, wherein one distribution output of the two-way
`distributor is supplied to the first reception series of the
`integrated circuit and the other distribution output is sup-
`plied to the second reception series of the integrated circuit.
`
`2 Claims, 8 Drawing Sheets
`
`31
`
`
`
`DETECTION
`
`INTERMEDIATE FREQUENCY
`—* DEMODULATION STAGE
`(FOR GROUND WAVE)
`
` WAVE
`
`
` WAVE
`
`DETECTION
`
`WAVE
`DETECTION
`
`36”
`
`i
`
`INTERMEDIATE FREQUENCY
`DEMODULATION STAGE
`{FOR SATELLITE WAVE}
`
`———_——
`1c
`
`INTEL 1224
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 1 of 8
`
`US 7,317,894 B2
`
`SLITMSLVSeT\ANVNOILWLSsoytHTTaLYSLiSHO
`
`SHNOD8AYNDI4V
`
`
`
`
`
`tOla
`
`r
`
`SLIMTALVS
`
`OSSAVBaNAOUS\alivTalvs§aNvM
`
`C
`
`Ya1VadaH=JOHLNOD
`GNNOYDZGNNOYD
`
`zNOILVLS
`
`NOILVLS
`
`=,
`
`JIGOW
`
`OlanLs
`
`
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 2 of 8
`
`US 7,317,894 B2
`
`FIG. 2
`
`
`
` GROUND
`
`WAVE
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 3 of 8
`
`US 7,317,894 B2
`
`
`
`ADNINOSHSSLVIGSWHSINI
`
`
`
`JOVISNOILYINGOWSA
`
`(AVMGNNOWDO34)
`
`€ea
`
`
`
`AONSNOSYSSLYIGSWY3INI
`
`
`
`JOvVISNOILYINGOWSA
`
`
`
`(GAVMSLIMSLVSHOS)
`
`8¢
`
`le
`
`ra LYVYOlWd
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 4 of 8
`
`US 7,317,894 B2
`
`FIG. 4
`
`LEVEL
`
`TIME
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 5 of 8
`
`US 7,317,894 B2
`
`
`
` 7SIGNALLEVELOFDISTURBANCEWAVE(dBm)
`
`
`
`
`
`FIG. 5
`
`
`
`Lyy
`
`RECEIVED SIGNAL LEVEL OF GROUND WAVE (dBm)
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 6 of 8
`
`US 7,317,894 B2
`
`
`
`XONANOAYSJLVIGSWYSLNI
`
`JOVLSNOVINGOWAG
`
`(AVMSLITISLYS403)
`
`8
`N
`
`Le
`
`NOILO3134d
`
`AVM
`
`TOYLNOO
`
`LINDHIO
`
`9€
`
`8—_—
`
`TOWLNOO
`
`LINDO
`
`Zi
`
`NOILO3130
`
`JAVM
`
`
`
`AONSNOSYSSLVIGSWHSINI
`
`
`
`JOVISNOLVINGOWSC
`
`
`
`(3AVMGNNOYDHOS)
`
`Xx
`
`NOISIAIG
`
`of
`
`Bw———!
`
`Le
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 7 of 8
`
`US 7,317,894 B2
`
`
`
`
`
`SIGNALLEVELOFDISTURBANCEWAVE(dBm)
`
`FIG. 7
`
`RECEIVED SIGNAL LEVEL OF GROUND WAVE (dBm)
`
`

`

`U.S. Patent
`
`Jan. 8, 2008
`
`Sheet 8 of 8
`
`US 7,317,894 B2
`
`FIG. 8
`
`~-.
`a-
`
`TIME
`
`

`

`US 7,317,894 B2
`
`1
`SATELLITE DIGITAL RADIO BROADCAST
`RECEIVER
`
`BACKGROUNDOF THE INVENTION
`
`1, Field of the Invention
`‘The present invention relates to a satellite digital radio
`broadcast receiver for receiving a broadcast program having
`the same contents but different modulation methods.
`
`2. Related Background Art
`Satellite digital radio broadcasting from a plurality of
`elliptical orbit satellites moving along a so-called figure 8
`orbit is presented, for example, by US SIRIUS Satellite
`Radio Incorporated. The outline of the whole system of
`satellite broadcast is shown in FIG. 1. This broadcast system
`uses one Geostationary satellite and three elliptical orbit
`satellites (not stationary satellite) each moving along a figure
`8 orbit. Since the service area is the North America, if a Geo
`stationary satellite only is used, the elevation angle of an
`antennais low sothat this is not suitable for mobile stations.
`
`An elliptical orbit satellite moves along the figure 8 orbit so
`that it does not always locate overhead. Therefore, a radio
`broadcast receiver sequentially and alternately receives a
`signal from any twosatellites amongthe three elliptical orbit
`satellites.
`In an area whereit is difficult to receive a radio wave from
`an elliptical orbit satellite or in an urban area where it is
`difficult to receive a satellite broadcast radio wave, a radio
`broadcast receiver receives in some cases a radio wave
`(ground wave) from a ground repeater which is controlled
`by a Geostationaryorbit satellite. Therefore, the satellite
`radio broadcast receiver receives three radio wavesintotal,
`two satellite waves and one ground wave, at the same time
`at its wide band RI’ amplifier. IG. 2 shows the spectrumof
`radio waves to be received by the receiver. The center
`frequency of this spectrum is approximately 2.3 GHz, and
`the satellite wave and ground wave have both the band width
`of about 4 MHz. Although the satellite wave #1 and the
`ground waveare received at the same timing, thesatellite
`wave #2 is received at
`the timing delayed by several
`seconds, and sotime diversity is presented. Ofthree satellite
`wavesfromthe elliptical orbits, the satellite wave #1 or #2
`is used depending upontheir orbits so that the control for the
`timediversity andalso fine frequencytuning are carried out.
`In the receiver, a band-pass filter built in the tuner unit
`separates each band, and the received signals are demodu-
`lated, combined and thereafter synthesized through synchro-
`nization.
`
`The features of this satellite digital radio broadcast system
`are summarized as in the following:
`1) Features of Radio Waves
`Since a ground wavehas a propagation path different from
`that of a satellite wave, the way howthe level fluctuates and
`the like are different from those of the satellite wave.
`Since the satellite wave is transmitted froma satellite on
`the elliptical orbit, it is received by the receiver at a high
`elevation angle. Since the propagation path does not change
`largely, the satellite wave can be receivedreliably unless the
`mobile station enters a tunnel or passes under a high way.
`2) Features of Reception System
`The receiver receives three waves containing the same
`contents. However, each radio wave has different frequency
`and propagation path, and a different time period while the
`same data is received. These radio waves are synthesized
`and demodulated so that the effects of frequency diversity,
`space diversity and time diversity can be obtained.
`
`10
`
`15
`
`25
`
`30
`
`35
`
`45
`
`60
`
`65
`
`2
`FIG. 3 shows the structure of a tuner unit of a satellite
`digital broadcast receiver 20 of the current system.
`In the tuner having the structure shown in FIG. 3, an
`antenna 11 receives a radio wave signal from a ground
`repeater, 1.e., a ground signal, the antenna having the direc-
`tional characteristics matching the ground signal. ‘he band
`of the received signal is limited by a band-passfilter 12, and
`an output of the band-pass filter 12 is selectively supplied
`eitherto a high frequencyamplifier 13 or an attenuator 14 to
`be amplified or attenuated. An antenna 21 receives a radio
`wave signal
`from a satellite,
`ie., a satellite signal,
`the
`antenna having the directional characteristics matching the
`satellite signal. The band of the received signalis limited by
`a band-passfilter 22.
`Anoutput signal from the high frequency amplifier 13 or
`an output signal from the attenuator 14 is amplified by a
`variable gain amplifier 15, and an output of this amplifier is
`supplied to a mixer 16 whereat
`it
`is converted into an
`intermediate frequency easy to be processed. An output of
`the mixer 16 is detected bya detector 17 to obtain a detection
`voltage corresponding to the input signal level. ‘This detec-
`tion voltage is supplied to a control circuit 18 which deter-
`mines a gain of the variable gain amplifier 15 in accordance
`with the supplied detection voltage, to thereby perform an
`automatic gain control (AGC). An output of the mixer 16 is
`also sent as a ground signal to an intermediate frequency
`stage to be subjected to an intermediate frequency process.
`An output of the intermediate frequency stage is supplied to
`a demodulation stage to be subjected to a demodulation
`process. If the input signal level is judged small from the
`detection voltage, the high frequencyamplifier 13 is selected
`byswitches 19a and 194, whereasif the input signal level is
`large, the attenuator 14 is selected by the switches 19a and
`19d.
`An output signal from the band-passfilter 22 is amplified
`ata variable gain amplifier 25, and an output of this amplifier
`is supplied to a mixer 26 whereat it is converted into an
`intermediate frequency easy to be processed. An output of
`the mixer 26 is detected by a detector 27 to obtain a detection
`voltage corresponding to the input signal level. This detec-
`tion voltage is supplied to a control circuit 28 which deter-
`mines a gain of the variable gain amplifier 25 in accordance
`with the supplied detection voltage,
`to thereby perform
`AGC. An output of the mixer 26 is also sent as a satellite
`signal to an intermediate frequency stage to be subjected to
`an intermediate frequency process. An output of the inter-
`mediate frequency stage is supplied to a demodulationstage
`to be subjected to a demodulation process.
`The variable gain amplifiers 15 and 25, mixers 16 and 26,
`detectors 17 and 27 and control circuits 18 and 28 are
`fabricated in an integrated circuit IC. There are two series,
`a ground wave signal series including the variable gain
`amplifier 15, mixer 16, detector 17 and control circuit 18,
`and a satellite wave signal series including the variable gain
`amplifier 25, mixer 26, detector 27 and control circuit 28.
`The reason ofdivision into twoseries is that although the
`broadcast contents are the same, the modulation methods are
`different between the ground wave signal of an OFDM
`modulation and the satellite wave signal of a QPSK modu-
`lation, the bands at the succeeding intermediate frequency
`stages are different and the gain distributions are different.
`In the satellite digital radio broadcast receiver described
`above, the frequency ofa received satellite wave signal is
`adjacent to that of a received ground wavesignal. These two
`signals, the satellite wave reception signal and ground wave
`reception signal, are input to the two series of the tuner.
`Since different gain settings are performed inthe integrated
`
`

`

`US 7,317,894 B2
`
`3
`circuit IC of the tuner because of different levels of the
`satellite wave reception signal and ground wavereception
`signals and the like, the tuner is divided into the two series
`in the integrated circuit IC.
`‘The tuner of the satellite digital radio broadcast receiver
`20 receives an adjacent disturbance wave signal b such as
`shown in FIG.4. In order to process this disturbance signal,
`the switching circuit for switching between the high fre-
`quency amplifier 13 and attenuator 14 is provided at the
`front stage of the integrated circuit IC in the ground wave
`signal reception series. This switching circuit operates in
`response to the output level of the detector 17 provided in
`the integrated circuit IC to thereby control the level of an
`input signal to the integrated circuit IC. In FIG.4, reference
`character a represents the level of a desired receptionsignal.
`A digital AGC method is known as disclosed,
`for
`example,
`in Japanese Patent Laid-open Gazette No.
`10-56343. With this method, in accordance with anelectric
`field intensity detected from an output of an intermediate
`frequency signal,
`the gain of a variable gain amplifier is
`controlled, and an output of the variable gain amplifier is
`orthogonally detected, and in accordance with a difference
`between the orthogonally detected IQ output signal ampli-
`tudes and desired IQ output signal amplitudes, the gain of
`the variable gain amplifier is finely adjusted.
`With the conventional
`tuner structure of the satellite
`digital radio broadcast receiver described above,it is, how-
`ever, necessary to set a hysteresis to the switching circuit in
`order to prevent the switching betweenthe high frequency
`amplifier 13 and attenuator 14 frombeing fluttered due to a
`reception signal
`level. A satellite digital radio broadcast
`receiver has as its one objective using it mounted on a
`vehicle. The reception condition during vehicle running is
`influenced by a multi-path and the like so that the signal
`level may change abruptly by 15 dB or more.
`It is therefore necessary that the switching hysteresis is 15
`dB or larger. Further, since a digital modulation method is
`incorporated for the satellite digital radio broadcast, if the
`reception signal is once intercepted, there is someidle time
`before sounds can be reproduced, because data synchroni-
`zation and the like are necessary. A complicated control
`process is therefore required such as matching the switching
`timing for signal level control to the data transition period
`and fixing the synchronization circuit and the like during
`such period.
`From these reasons, the level adjustment of a ground
`wave signal input to the integrated circuit IC is something
`intermittent. FIG. 5 shows the disturbance wave elimination
`
`characteristics actually measured. As shown, the character-
`istics are stepwise and there are an input signal level having
`the bad disturbance wave elimination characteristics and an
`input signal level having the good disturbance wave elimi-
`nation characteristics. Thereis a difference of 10 dB or more
`between these signal levels. If a signal cannot be received
`once because of the switching hysteresis control, even if the
`disturbance signal level lowers somewhat, it is not so fast
`until the reception is recovered. The hatched area in FIG. 5
`indicates a reception enabled range.
`
`SUMMARY OF THEINVENTION
`
`is an objective of the present invention to provide a
`It
`satellite digital radio broadcast receiver capable of eliminat-
`ing the above-described disadvantages and improving the
`disturbance wave elimination characteristics with a simple
`structure.
`
`25
`
`35
`
`40
`
`45
`
`a an
`
`60
`
`4
`According to one aspect of the present invention, there is
`provided a satellite digital radio broadcast receiver having
`an integrated circuit including a first reception series for
`performing a reception processing ofa satellite wave signal
`from a satellite and a second receptionseries for performing
`a reception processing of a ground wave signal from a
`repeater in orderto receive both the satellite wave signal and
`the ground wavesignal having the same broadcast contents
`and different modulation methods, thesatellite digital radio
`broadcast
`receiver comprising: automatic gain control
`means for amplifying a signal from a single antenna at a
`variable gain amplifier, and in accordance with a level of a
`signal outputted from the variable gain amplifier, for con-
`trolling a gain ofthe variable gain amplifier to contro] the
`level of the signal outputted from the variable gain amplifier;
`and a two-waydistributor for distributing an output of the
`automatic control means
`to two distribution outputs,
`wherein one distribution output from the two-waydistribu-
`tor is supplied to the integrated circuit as an input signal to
`the first reception series, and the other distribution output
`from the two-way distributor is supplied to the integrated
`circuit as an input signal to the second reception series.
`Accordingto the satellite digital radio broadcast receiver,
`the input signals to the first and second reception series of
`the integrated circuit have the levels controlled by the
`automatic gain control means. Therefore, the input signal
`level can be maintained generally constant evenif there is a
`sharp change in a disturbance signal level.
`Asabove, accordingto the satellite digital radio broadcast
`receiver ofthis invention, only oneseries can suffice for the
`input signals to the integrated circuit so that the receiver can
`be made compact and the cost can be reduced.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a diagram showing the outline of a satellite
`digital radio broadcast system.
`FIG,2 is a diagram showing the spectrumof radio waves
`to be received bya satellite digital radio broadcast receiver.
`FIG. 3 is a block diagram showingthestructure of a tuner
`unit of a conventional satellite digital
`radio broadcast
`receiver.
`FIG. 4 is the characteristic diagram explaining the dis-
`turbance signal elimination characteristics of a conventional
`satellite digital radio broadcast receiver.
`FIG. 5 is a schematic diagram explaining a disturbance
`radio wave to be received by a conventionalsatellite digital
`radio broadcast receiver.
`FIG. 6 is a block diagram showingthestructure of a tuber
`unit ofa satellite digital radio broadcastreceiver according
`to an embodimentofthe invention.
`
`FIG. 7 is the characteristic diagram explaining the dis-
`turbance signal elimination characteristics of the satellite
`digital radio broadcast receiver of the embodiment.
`FIG. 8 is a schematic diagram explaining a disturbance
`radio wave to be received by the satellite digital radio
`broadcast receivers of the embodiment andthe priorart.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`Description will be made on a satellite digital radio
`broadcast receiver according to an embodimentofthe inven-
`tion.
`
`FIG. 6 is a block diagram showing thestructure of a tuner
`unit of a satellite digital radio broadcast receiver according
`to the embodiment of the invention.
`
`

`

`US 7,317,894 B2
`
`10
`
`15
`
`6
`5
`muting state of an audio signal when the level of an input
`In the satellite digital radio broadcast receiver 30 of the
`signal to the integratedcircuit IC is controlled by the voltage
`embodiment, an antenna 31 receives a satellite wave signal
`control type variable gain amplifier 33 upon reception of the
`and a ground wavesignal. The band ofthe received signal
`disturbance wave a. The highlevelline indicates the period
`is limited by a band-pass filter 32, and an output ofthe
`while the muting state is removed and an audio signal is
`band-pass filter 32 is supplied to and amplified at a voltage
`obtained, and the lowlevel line indicates the period while
`control type variable gain amplifier 33. An output signal
`the muting state is effected and an audio signal cannot be
`from the voltage control type variable gain amplifier 33 is
`obtained.
`supplied to a two-waydistributor 34 which inputs two-way
`Asapparent from the comparison between the lines c and
`distributed output signals to variable gain amplifiers 15 an
`d in FIG. 8, as compared to the satellite digital radio
`25 of an integrated circuit IC, respectively. The integrated
`broadcast receiver 20, the satellite digital radio broadcast
`circuit IC has the samestructure as the integrated circuit IC
`receiver 30 has a shorter sound interception period and a
`shown in FIG. 3, and so the description of the structure and
`shorter reception stop period.
`operation thereof is omitted.
`Since the satellite digital radio broadcast receiver 30 has
`type variable gain
`An output of the voltage control
`only oneseries as the front end of the integrated circuit IC,
`amplifier 33 is detected by a detector 35 to obtain a detection
`it can be made compact and the cost can be reduced.
`voltage corresponding to the input signal level. This detec-
`tion voltage is supplied to a control circuit 36 which converts
`Asdescribed so far, accordingto thesatellite digital radio
`it into an AGC control voltage. The AGC control voltage is
`broadcast receiver, only one series is used as the front end
`supplied as a gain control voltage to the voltage control type
`of the integrated circuit, and the level of an input signal to
`variable gain amplifier 33 to perform AGC and control the
`the integrated circuit is controlled by AGC. Accordingly, the
`level of an input signal to the integrated circuit IC. The
`satellite digital radio broadcast receiver has a shorter sound
`antenna 31 is either an antenna for receivingasatellite wave
`interception period and a shorter reception stop period.
`signal or an antenna for receiving a ground wavesignal.
`Furthermore,
`since the satellite digital radio broadcast
`The two-waydistributor 34 distributes an input at a
`receiver 30 has only one series as the front end of the
`distribution ratio suitable for gains of two series in the
`integrated circuit IC, it can be made compact and the cost
`can be reduced.
`integrated circuit IC and supplies the distributed signals to
`the variable gain amplifiers 15 and 25, respectively. A better
`one of the demodulation signals of the twoseries is selected
`and output, similar to conventional techniques.
`Asdescribed above, in the tuner unit of the satellite digital
`radio broadcastreceiver 30, the level of an input signal to the
`integrated circuit IC is controlled by AGC, and signals
`having AGC controlled levels are distributed to the two
`series of the integrated circuit IC. Therefore, the level of an
`input signal to the integrated circuit IC is controlled con-
`tinuously in an analog fashion, so that the input signal level
`is not switched intermittently as in the case of conventional
`techniques. As indicated at b in FIG. 7, the disturbance
`signal elimination characteristics will not be degraded
`abruptly so that even a sharp changeina disturbance signal
`level can be followed smoothly. In addition, even if the
`receiver is mounted on a vehicle, broadcast reception is
`hardly broken. The disturbance signal elimination charac-
`teristics indicated at a in FIG. 7 are the same as those shown
`in FIG.5.
`
`25
`
`30
`
`35
`
`40
`
`45
`
`FIG. 8 is a schematic diagram showing actual measure-
`ments by the satellite digital radio broadcast receiver 30 of
`the embodiment and the conventional receiver 20, both
`mounted on a vehicle running through the New Yorkcity.
`The level of a disturbance wave is indicated at a in FIG.8.
`A line indicated at b in FIG. 8 showsthe selection state
`between the high frequency amplifier 13 and attenuator 14.
`The high level
`line indicates a selection of the high fre-
`quency amplifier 13, and the low level
`line indicates a
`selection of the attenuator 14. A line indicated at ¢ in FIG.
`8 schematically illustrates a muting state of an audio output
`when the level of an input signal to the integrated circuit IC
`is controlled by switching between the high frequency
`amplifier 13 and attenuator 14 uponreception of the distur-
`bance wave a. The high level line indicates the period while
`the muting state is removed and an audio signalis obtained,
`and the low level line indicates the period while the muting
`state is effected and an audio signal cannot be obtained. A
`line indicated at d in I'IG. 8 schematically illustrates a
`
`a an
`
`aD0
`
`What is claimedis:
`
`1. A satellite digital radio broadcast receiver having an
`integrated circuit including a first reception series for per-
`forming a reception processing of a satellite wave signal
`from a satellite and a second reception series for performing
`a reception processing of a ground wave signal from a
`repeater in order to receive boththe satellite wave signal and
`the groundwavesignal having the same broadcast contents
`and different modulation methods, a total gain through the
`first reception series being different from a total gain through
`the second reception series, the satellite digital radio broad-
`cast receiver comprising:
`automatic gain control means for amplifying a signal from
`a single antenna at a variable gain amplifier, and in
`accordance with a level of a signal outputted fromthe
`variable gain amplifier, for controlling a gain of the
`variable gain amplifier to control the level ofthe signal
`outputted from the variable gain amplifier; and
`a two-way distributor for distributing an output of the
`automatic gain control means to two distribution out-
`puts,
`wherein one of the two distribution outputs from the
`two-way distributor is supplied to said integrated cir-
`cuit as an input signal to the first reception series, and
`the other of the two distribution outputs from the
`two-waydistributor is supplied to the integrated circuit
`as an input signal to the second reception series, and
`wherein the two-waydistributor operates to distribute an
`input at a distribution ratio according to the difference
`betweenthe total gain through the first receptionseries
`and the total gain through the second receptionseries.
`2. The satellite digital radio broadcast receiver according
`to claim 1, wherein the antenna is either an antenna for
`receiving the satellite wave signal or an antenna for receiv-
`ing the ground wavesignal.
`
`