US005381444A
`United States Patent 1
`5,381,444
`[11] Patent Number:
`Tajima
`
`[45] Date of Patent: Jan. 10, 1995
`
`AAAIAAA
`
`[54] RADIO ENVIRONMENT MEASURING
`SYSTEM
`
`Inventor: Masami Tajima, Kawasaki, Japan
`[75]
`[73] Assignee:
`Fujitsu Limited, Kawasaki, Japan
`[21] Appl. No.: 969,460
`[22] Filed:
`Oct. 30, 1992
`[30]
`Foreign Application Priority Data
`Oct. 31, 1991 [JP]
`Japan...scsssscssssesseseencens 3-286213
`Fun. 30, 1992 [JP]
`Japan ..cssessssscsssscssccsseessesesees 4-172993
`([S1]
`Int. CLS wees HO4L 27/30; GO1S 13/46
`[52]
`UWS. C1. woeeccessessecesnessessesenstesveneees 375/1; 380/34;
`342/118; 342/125; 379/58; 379/59; 455/33.1;
`455/53.1; 455/54.1; 455/67.1; 455/67.6
`[58] Field of Search...............5.. 455/52.3, 54.1, 54.2,
`455/56.1, 65, 67.1, 67.3, 67.4, 67.6, 33.1, 53.1;
`3735/1, 11-14; 380/38, 34; 342/118, 125;
`379/58, 59
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,315,257 4/1967 Sauberlich .......esscseeseee 342/125
`342/125 X
`3,714,650
`1/1973 Fuller et al.
`...
`
`wee 342/125
`3,790,940 2/1974 Becker.........
`4,593,273 6/1986 Narcisse ........scccerseesee 342/125 X
`4,667,202 5/1987 Kammerlanderetal. .... 455/54.2 X
`4,907,290 3/1990 Crompton ......cccseesececrees 455/56.1
`5,208,756 5/1993 Song oon..ccecscsssssrsceesesees 455/54.1 X
`
`FOREIGN PATENT DOCUMENTS
`
`8/1988 Japan .
`63-501981
`9/1989 Japan .
`1-223371
`1-292277 11/1989 Japan .
`4-15584
`1/1992 Japan .
`
`Primary Examiner—Bernarr E. Gregory
`Attorney, Agent, or Firm—Armstrong, Westerman,
`Hattori, Mcleland & Naughton
`
`ABSTRACT
`[57]
`A radio environment measuring system for measuring a
`propagation state of radio waves includes:a fixed radio
`apparatus provided in a base station; a mobile radio
`apparatus operatively connected to the fixed radio ap-
`paratus through the radio waves; the mobile radio appa-
`ratus having a repeater unit for receiving a transmission
`signal from the fixed radio apparatus and sending a
`returned signal to the fixed radio apparatus; and the
`fixed radio apparatus having a transmission/reception
`unit for sending the transmission signal to the mobile
`radio apparatus and receiving the returned signal from
`the mobile radio apparatus, and a measuring unit for
`measuring the propagation state of the radio waves, for
`example, a propagation distance, direction and recep-
`tion intensity of the radio waves betweenthe fixed radio
`apparatus and the mobile radio apparatus based on the
`transmission signal and the returned signal.
`
`12 Claims, 12 Drawing Sheets
`
`INTENSITY
`
`
`TRANSMISSION /
`RECEPTION
`UNIT
`
`MEASURING
`UNIT
`
`DISTANCE
`DIRECTION
`
`FIXED RADIO
`APPARATUS
`
`TRANSMISSION /
`RECEPTION
`UNIT
`
`RETURNING
`TRANSMISSION
`
`_ MOBILE RADIO
`APPARATUS
`
`APPLE 1006
`
`APPLE 1006
`
`1
`
`

`

`U.S. Patent
`
`Jan, 10, 1995
`
`Sheet 1 of 12
`
`5,381,444
`
`Fig,
`
`|
`
`REFLECTED
`
`
`~~ RADIO WAVE
`
`
`
`
`
`
`FIXED
`MOBILE
`
`
`RADIO
`RADIO
`
`
`APPARATUS
`
`APPARATUS
`
`
`DIRECT RADIO WAVE
`
`2
`
`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 2 of 12
`
`5,381,444
`
`Fig. 2
`
`DIRECT
`WAVE
`
`REFLECTED
`WAVE 1
`
`
`REFLECTED
`WAVE 2
`
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`O.
`
`—Q
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`e>© L
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`u
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`MOBILE
`RADIO
`
`APPARATUS
`
`i
`.
`PROPAGATION DISTANCE (TIM
`OF RADIO WAVE
`(TIME)
`
`™
`
`3
`
`

`

`U.S. Patent
`
`‘Sheet 3 of 12
`
`5,381,444
`
`
`
`TRANSMISSION /
`RECEPTION
`UNIT
`
`RETURNING
`TRANSMISSION
`
`MOBILE RADIO
`APPARATUS
`
`TRANSMISSION/
`RECEPTION
`UNIT
`
`MEASURING
`UNIT
`
`DISTANCE
`DIRECTION
`
`INTENSITY
`
`FIXED RADIO
`APPARATUS
`
`4
`
`

`

`U.S. Patent
`
`Jan, 10, 1995
`
`Sheet 4 of 12
`
`5,381,444
`
`Fig. 4
`
`1
`
`‘“\
`
`18
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`NON—DIRECTIONAL
`DIRECTIONAL
`ANTENNA
`12 ANTENNA
`11
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`16
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`Be) Bd)
`
`DET ep
`
`
`Oem OR ft
`CE
`40
`(x) 38 | MEASURING UNIT
`|
`Fig
`. Td
`
`
`
`5
`
`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 5 of 12
`
`5,381,444
`
`Fig. 5
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`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 6 of 12
`
`5,381,444
`
`
`
`7
`
`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 7 of 12
`
`5,381,444
`
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`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 8 of 12
`
`5,381,444
`
`DEMODULATION
`
`OF PN CODE
`
`PSFUDO NOISE GENERATOR
`(PN
`CODE)
`__|
`
` j
`
`80
`
`
`
`|
`
`9
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`

`

`U.S. Patent
`
`Jan, 10, 1995
`
`Sheet 9 of 12
`
`5,381,444
`
`Fig. 9
`
`
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`efefefeme
`
`10
`
`10
`
`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 10 of 12
`
`5,381,444
`
` 514
`
`RADAR SIGNAL
`
`DISPLAY
`
`11
`
`SYSTEM
`
`
`
`
`
`CONTROLLER eee | CONTROLLER
`
`11
`
`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 11 of 12
`
`5,381,444
`
`Fig, 11
`
`NON—DIRECTIONAL
`
`ANTENNA
`
`12
`
`12
`
`

`

`U.S. Patent
`
`Jan. 10, 1995
`
`Sheet 12 of 12
`
`5,381,444
`
`Fig. 2B
`
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`

`

`1
`
`5,381,444
`
`RADIO ENVIRONMENT MEASURING SYSTEM
`
`2
`radio apparatus also includes a repeater unit for sending
`the returned signal to the fixed radio apparatus, and
`further, the transmission/reception of the transmission
`BACKGROUND OF THE INVENTION
`and returned signals are performed for predetermined
`1. Field of the Invention
`times between the fixed radio apparatus and the mobile
`radio apparatus.
`The present invention relates to a radio environment
`In another preferred embodiment, the measuring unit
`measuring system, moreparticularly,it relates to a radio
`measures the propagationstate of the radio waves based
`environment measuring system for measuring a propa-
`on the first transmission signal and the returned signal
`gation state of radio waves, for example, propagation
`after transmission/reception for predetermined times.
`distance, propagation direction, and reception intensity
`of the radio waves, and improving the characteristics of
`In still another embodiment, the fixed radio apparatus
`further include a non-directional antenna and a direc-
`a propagation path of the radio waves.
`tional antenna.
`2. Description of the Related Art
`Recently, various mobile radio communication sys-
`In still another embodiment, the transmission/recep-
`tems, such as a land mobile radio telephone and a porta-
`tion unit of the fixed radio apparatus further includes a
`ble radio telephone, have been developedin the field of
`side lobe compression unit for deciding on a reception
`mobile radio communication systems. Further, as the
`signal based on a main lobe when the reception level of
`structure of the system becomes more complex,it is
`the directional antennais larger than that of the non-
`directional antenna.
`necessary to obtain a propagation state of the radio
`waves between the radio apparatuses in the environ-
`In still another embodiment, the transmission/recep-
`ment in which the radio waves are used.In this case, by
`tion unit of the fixed radio apparatus further includes a
`investigating the relationship between the location of a
`sweep unit for switching the frequency of the transmis- —
`radio base station includingafixed radio apparatus) and
`sion signal and sweeping the frequency, and the measur-
`the propagation state of the radio waves within the
`ing unit measures the propagation state of the radio
`service zone thereof, it is possible to provide the radio
`waves based on the change of the phase difference be-
`base station at an optimum location.
`tween the transmission signal and the returned signal.
`In various radio waves, for example, a radio wave
`In still another embodiment, the transmission/recep-
`directly propagated between radio apparatuses, a radio
`tion unit of the fixed radio apparatus further includes a
`wave reflected from the wall of a building, etc, and
`transmission unit for sending a transmission signal mod-
`other radio waves incoming from an external environ-
`ulated by codes having relatively large auto-correla-
`ment, to know howthese radio waves are propagated is
`tion, and the measuring unit measures the propagation
`the most important element in obtaining an optimum
`state based on the auto-correlation for the demodulated
`radio environment. Accordingly, it is desired to realize
`coded which are obtained by the returned signal from
`a measuring method to easily and precisely obtain the
`the mobile radio apparatus.
`propagation state of the radio waves.
`In still another embodiment, the transmission/recep-
`SUMMARY OF THE INVENTION
`tion unit of the mobile radio apparatus further includes
`a delay circuit for delaying the returned signal based on
`the instruction from the fixed radio apparatus.
`In still another embodiment, the measuring unit of the
`fixed radio apparatus further includes a square-composi-
`tion unit for obtaining the phase difference between the
`returned signal and the reference carrier having 90
`degrees of phase difference, and squaring the phase
`difference signal to obtain the composition signal.
`In still another embodiment, the transmission/recep-
`tion unit of the fixed radio apparatus further includes a
`dispersive delay line and a pulse oscillator for generat-
`ing linear frequency modulated pulses in the transmis-
`sion unit, and a limit amplifier LIM and a dispersive
`delay line for demodulating in the reception unit; fur-
`ther, the mobile radio apparatus further includes a fre-
`quency converter and the limit amplifier.
`In still another embodiment;
`the fixed radio apparatus generates a transmission
`signal similar to a radar radio wave from the pulse oscil-
`lator, performs the linear frequency modulation to ob-
`tain a spectrum-spread pulse for the time axis by the
`dispersive delay line, and sends the spectrum-spread
`pulse to the mobile radio apparatus;
`the mobile radio apparatus performs the spectrum
`inversion based on the frequency-converted reception
`signal, and sends the returned signal to the fixed radio
`apparatus;
`the fixed radio apparatus performs the frequency
`conversion to obtain the linear-frequency modulated
`pulse having the opposite characteristic to the transmis-
`sion signal, suppresses the modulated pulse based on the
`
`The object of the present invention is. to provide a
`radio environment measuring system enabling precise
`measurement of the propagation state of radio waves,
`for example, the propagation distance, direction and
`reception intensity of the radio waves.
`In accordance with the present invention, there is
`provided a radio environment measuring system for
`measuring the propagation state of radio waves includ-
`ing:
`a fixed radio apparatus provided in a base station;
`a mobile radio apparatus operatively connected to the
`fixed radio apparatus through the radio waves;
`the mobile radio apparatus having a transmission/-
`reception unit for receiving a transmission signal
`from the fixed radio apparatus and sending a return
`signal to the fixed radio apparatus; and
`the fixed radio apparatus having a transmission/-
`reception unit for sending the transmission signal to
`the mobile radio apparatus and receiving the re-
`turned signal from the mobile radio apparatus, and
`a measuring unit for measuring the propagation
`state of the radio waves, for example, a propaga-
`tion distance, direction and reception intensity of
`the radio waves between the fixed radio apparatus
`and the mobile radio apparatus based on the trans-
`mission signal and the returned signal.
`In one preferred embodiment,
`the transmission/-
`reception unit of the fixed radio apparatus includes a
`repeater unit for receiving the returned signal and again
`sending the returned signal to the mobile radio appara-
`tus, and the transmission/reception unit of the mobile
`
`10
`
`35
`
`60
`
`65
`
`14
`
`14
`
`

`

`3
`function of the pulse compression radar to concentrate
`the reflection energy spread for the time and frequency,
`and measures the propagation state of radio waves for
`every delay time from the start of the transmission of
`the radio waves from the fixed radio apparatus.
`In still another embodiment, each ofthe limit amplifi-
`ers in the fixed and mobile radio apparatuses has the
`function of suppressing the amplitude of the strong
`interference wave, and the above amplitude-limited
`interference waves are spread by the pulse compression
`function for the time and frequency.
`BRIEF DESCRIPTION OF THE DRAWINGS
`In the drawings:
`FIG.1is an explanatory view of propagation of radio
`wave between a fixed radio apparatus and a mobile
`radio apparatus;
`FIG. 2 is an explanatory view of the relationship
`betweenthe correlative output at a reception side of the
`radio wave and the propagation distance (propagation
`time) of the radio wave;
`FIG.3 is a principal structural view of the present
`invention;
`FIG, 4 is a block diagram of a transmission/reception
`unit of the fixed radio apparatus according to a first
`embodimentof the present invention;
`FIG.5 is a block diagram of a measuring unit of the
`fixed radio apparatus accordingto the first embodiment
`of the present invention;
`FIG.6 is a block diagram of the mobile radio appara-
`tus according to the first embodiment of the present
`invention;
`FIGS. 7A and 7B are explanatory viewsof the rela-
`tionship between the wavelength and the frequency;
`FIG.8 is an essential block diagram of a demodula-
`tion circuit for a signal extracting operation according
`to the first embodiment of the present invention;
`FIG.9 is a view for explaining a demodulating opera-
`tion for the Barker code used in the demodulation cir-
`cuit shown in FIG.8;
`FIG.10 is a block diagram ofthe fixed radio appara-
`tus according to a second embodiment of the present
`invention;
`FIG.11is a block diagram of the mobile radio appa-
`ratus according to the second embodimentofthepres-
`ent invention; and
`FIG. 12A-12H are an explanatory view of a pulse
`compression radar used in the second embodiment of
`the present invention,
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Before describing the preferred embodiment of the
`present invention, a conventional art and its problems
`are explained in detail below.
`FIG. 1 is an explanatory view of propagation of a
`radio wave between a fixed radio apparatus and a mo-
`bile radio apparatus. As shown in FIG. 1, as one path,
`the radio waveis directly propagated from the fixed
`radio apparatus 1 to the mobile radio apparatus, and as
`another path, the radio waveis reflectingly propagated
`by the wall ofa building. In general, the formeris called
`a “direct radio wave”, and the latter is called a “re-
`flected radio wave”.
`FIG. 2 is an explanatory view of the relationship
`betweenthe correlative output at a reception side of the
`radio wave and the propagation distance (propagation
`time) of the radio wave. In FIG.2, the correlative out-
`
`15
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`5,381,444
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`4
`put denotes an intensity of the reception signal of the
`radio waveat the fixed radio apparatus, and the inten-
`sity of the reception signal becomes weaker in accor-
`dance with the propagation distance of the radio wave.
`In the drawing, reference letters Ro, Ri and R2 denote
`the propagation distance of the radio wave which cor-
`respond to the time elapsed from the radiation of the
`tadio waves. Thatis, first, the direct radio wave reach
`the fixed radio apparatus, second, the reflected radio
`wave reach one,and third, anotherreflected radio wave
`reaches to one. Accordingly, it is possible to measure
`not only the propagation distance (propagation time) of
`the direct radio wave, but also that of the reflected
`tadio wave in the fixed radio apparatus. This example
`corresponds to the “A-scope” of a radar system.
`In a conventional measuring method of a radio envi-
`ronment, a fixed radio apparatus (provided in the radio
`base station) radiates radio waves through a non-direc-
`tional antenna, and a mobile radio apparatus receives
`the radio waves to measure the propagation state, ie.,
`the propagation distance and the intensity of the radio
`waves. In this case, the radio wave measurement is
`one-way.
`Further, in an urban district in which there are many
`high buildings, since such high buildings constitute
`teflective bodies against the radio waves, it is very
`difficult for the mobile radio apparatus to distinguish
`whether received radio waveis direct or reflected radio
`wave. Accordingly, it is very difficult to precisely mea-
`sure the propagation distance/time of the radio wave.
`To solve the above problem,the following methodis
`proposedin this field. That is, the fixed radio apparatus
`sends a carrier wave modulated by PN (pseudonoise)
`codes having large auto-correlation to the mobile radio
`apparatus, and the mobile radio apparatus distinguishes
`whetherit receives a direct radio wave or a reflected
`radio wave based on the maximum autocorrelation.
`Further, another structure is proposed in which the
`modulation speedis set to a higher value, for example,
`10 MHz so as to distinguish the reflected radio wave.
`According to this method,it is possible to improve the
`accuracy of measurementof the distance and the propa-
`gation path, and improve the resolution for measure-
`ment of the intensity of the radio wave.
`However, some problems remain in the conventional
`method in which the mobile radio apparatus receives a
`radio wave from thefixed radio apparatus and measures
`the reception level and direction. Oneis interference of
`the radio waves due to multi-path reflections caused by
`buildings. In this case, it is very difficult to measure the
`propagation state becauseof the fluctuation of the radio
`wave caused by the interference.
`Another is a range cell representing the minimum
`resolution distance.
`In this case,
`it
`is necessary to
`shorten the range cell and to narrow the pulse width to
`raise the resolution for the propagation distance. Since
`this requires a higher modulation speed, the necessary
`range of the radio wave becomes broader. However,
`since the usable range of the radio waveis limited,it is
`impossible to employ means to broaden the necessary
`range. Accordingly,it is impossible to raise the modula-
`tion speed of the carrier so that it is very difficult to
`improve the resolution for measuring the propagation
`distance.
`Further,since the mobile radio apparatus uses a non-
`directional antenna to receive the radio wave from the
`fixed radio apparatus, it is impossible to measure the
`incoming direction of the radio wave. Further, in the
`
`5
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`5
`the direction of the
`case of the directional antenna,
`side-lobe becomes incorrect for the direction of the
`main-lobe so thatit is impossible to measure the incom-
`ing direction of the radio wave.
`FIG.3 is a principal structural view ofthe present
`invention. As shown in FIG. 3, the radio environment
`measuring system according to the present invention
`has the fixed radio apparatus 1 and the mobile radio
`apparatus 2. The mobile radio apparatus 2 has the trans-
`mission/reception unit 3 having repeater means for
`receiving the signal from the fixed radio apparatus 1 and
`sending a return signal to the fixed radio apparatus 1.
`Thefixed radio apparatus1 has the transmission/recep-
`tion unit 4 and the measuring unit 5 for measuring the
`propagation distance, the direction and the reception
`intensity (level) of the radio wave based onthe signal
`returned from the mobile radio apparatus 2.
`In the first embodimentof the present invention, the
`transmission/reception unit 4 of the fixed radio appara-
`tus 1 has the repeater means which receives the re-
`turned signal from the mobile radio apparatus 2 and
`again transmits thereto. The measuring unit 5 has the
`measuring means which measures the propagation dis-
`tance, direction and reception level of the radio wave
`based on the reception signal after transmission/recep-
`tion for predetermined times, and thefirst transmission
`signal.
`Further, the fixed radio apparatus 1 has the non-
`directional antenna and the directional antenna,
`the
`transmission/reception unit 4 has the side lobe suppres-
`sion means which decides the reception signal based on
`the main lobe when the reception level of the direc-
`tional antennais higher than that of the non-directional
`antenna.
`Further,the transmission/reception unit 4 ofthe fixed
`radio apparatus has sweep means which sweeps and
`switches the transmission signal. The measuring unit 5
`has the measuring means which measures the propaga-
`tion distance, distance and the reception intensity based
`on the change of the phase difference between the re-
`turned signal from the mobile radio apparatus and the
`first transmission signal.
`Further, the transmission/reception 4 has the trans-
`mission means which transmits the signal modulated by
`the code having large auto-correlation, and the measur-
`ing unit 5 has the measuring means which measures the
`propagation distance, direction and the reception level
`based on the auto-correlation of the code demodulated
`from the signal returned from the mobile radio appara-
`tus 2. The transmission/reception unit 3 has the delay
`circuit which controls the delay time of the reception
`signal based on the instruction from the fixed radio
`apparatus 1. The measuring unit 5 has the square-com-
`position means which squares and composes the phase
`difference signal obtained from the phase difference
`between the returned signal from the mobile radio appa-
`ratus 2 and the base carriers each having the phase
`difference of 90 degrees.
`The measuring unit 5 measure the propagation dis-
`tance (or time) both ways (.e., going and returning).
`Accordingly, since a double distance is used for the
`measurement, it is possible to improve the measuring
`resolution of the propagation distance. Further, since
`only a propagation wave that passes through the re-
`peater is amplified in the mobile radio apparatus so that
`gain of the transmission/reception unit 3 is previously
`obtained, it is possible to easily correct the reception
`level of the fixed radio apparatus.
`
`40
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`5,381,444
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`10
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`6
`the transmission/reception unit 4 has the
`Further,
`same repeater (signal-returning means) as the mobile
`radio apparatus 2 so thatit is possible to return transmis-
`sion/reception for predetermined times between the
`fixed and mobile apparatuses. Accordingly, after repeti-
`tion of transmission/reception for several times, since
`the propagation distance of the direct and reflected
`radio waves appears to be longer, it is possible to im-
`prove the measuring resolution of the distance and to
`raise the precision of the measurement. This is very
`effective when the distance between the mobile radio
`apparatus and the fixed radio apparatus is very small.
`The non-directional antenna 11 of the fixed radio
`apparatus 1 has the same gain for any horizontal direc-
`tion in 360 degrees. The directional antenna 12 has a
`larger gain than the non-directional antenna 11 for the
`direction of the main lobe and has a smaller gain than
`the non-directional antenna 11 for the direction of the
`side lobe. Accordingly, the measuring unit 5 compares
`the reception level of the non-directional antenna with
`that of the directional antenna so that is possible to
`perform the reception based on the side lobe suppres-
`sion and to precisely measure the direction of the mo-
`bile radio apparatus 2 based on the main lobe of the
`directional antenna 12.
`Further, the sweep meansof the transmission/recep-
`tion unit 4 sweeps or changes the frequencyofthe trans-
`mission signal. Since the phase difference between the
`transmission signal and the reception signal in the mea-
`suring unit 5 changes in accordance with the slight
`change of the frequency, it is possible to obtain the
`propagation distance based on the ratio of the number
`of radio waves within the propagation distance of the
`tadio wave.
`FIG.4 is a detailed block diagram ofa transmission/-
`reception unit of the fixed radio apparatus according to
`the first embodimentof the present invention. In FIG.
`4, reference number 11 denotes a non-directional an-
`tenna; 12 a directional antenna; 13, 14, 22 and 26 direc-
`tional couplers (DC); 15, 28 and 35 switches (SW); 16 a.
`detection circuit (DC) for reception wave; 17 a side
`lobe suppression circuit (SLS); 18 a control circuit
`(CNT); 19 a circulator (CIR); 20, 29, 31 and 36 filters
`(FL); 21 and 32 amplifiers (AMP); 23 a phase shifter
`(PS); 24, 30 and 38 mixers (MIX); 25 a variable fre-
`quency oscillator (OSC) having high stabilized fre-
`quency; 27 a modulator (MOD); 33 a modulation con-
`trol unit (MCNT) for controlling the modulator 27 in
`accordance with a CW (continuous wave) mode, a
`radar mode and a hopping mode; 34 a code generator
`(CG) for generating a Barker code and PN code; 37 a
`terminal connected to a spectrum analyzer for measur-
`ing reception intensity; and 40 a measuring unit.
`In the first embodiment of the present invention, the
`fixed radio apparatus is fixedly provided only when
`measuring the propagation state of the radio wave, and
`it may be moved to an optional location if necessary.
`The switches 15, 28 and 35 are controlled by the
`control circuit 18. The switch 15 connects between the
`circulator 19 and the directional coupler 13 or 14 so that
`it is possible to switch between the non-directional an-
`tenna 11 and the directional antenna 12.
`Whenthe transmission frequency is “ft” and the fre-
`quency returned from the mobile radio apparatus 2 is
`65 <.
`r”’, the switch 35 is switched as follows. That is, when
`Measuring the signal of
`the returned frequency
`fr=(ft-+ fi) (here, “fi” is an intermediate frequency), the
`oscillator 25 generates the signal of the frequency ft and
`
`16
`
`

`

`5,381,444
`
`15
`
`20
`
`25
`
`45
`
`7
`sendsit to the mixer 24 throughthedirectional coupler
`26 and the switch 35. When measuring the reflected
`radio wave having the frequency ft, the oscillator 25
`generates the frequency ft and sendsit to the mixer 38
`through the directional coupler 26, and the mixer 38
`mixes the frequency ft with the frequency fig and out-
`puts the frequency (ft+ fig) to the mixer 24 through the
`filter 36.
`Accordingly, the measuring unit 40 receives the in-
`termediate frequency fi mixed by the mixer 24.In this
`embodiment, ft=3000 MHz, and fi=fip=10 MHz. The
`filter 20 has a pass-band of the frequency ft and
`fr=ft-+ fi, and the filters 29 and 31 have the passband of
`the frequencyft.
`In FIG.4, the radio wave returned from the mobile
`radio apparatus 2 is received by the non-directional
`antenna 11 and the directional antenna 12, and the re-
`ception signals divided by the directional couplers 13
`and 14 are added to the detection circuit 16. The side
`lobe suppression circuit 17 compares the reception level
`of the non-directional antenna 11 and thatof the direc-
`tional antenna 12.In this case, the gain of the non-direc-
`tional antenna 12 is set to a gain smaller than that of the -
`main lobe ofthe directional antenna12,and set to a gain
`larger than that of the side lobe.
`Accordingly, when the reception level of the direc-
`tional antenna 12 is smaller than that of the non-direc-
`tional antenna 11, the suppression circuit 17 detects that
`the reception signal is based on the side lobe. On the
`contrary, when the reception level of the directional
`antenna 12 is larger than that of the non-directional
`antenna 11, the suppression circuit 17 detects that the
`reception signal is based on the main lobe of the direc-
`tional antenna 12. Accordingly,it is possible to elimi-
`nate the influence of the side lobe of the directional
`antenna 12 and to precisely detect the direction of the
`mobile radio apparatus 2 based on the main lobe and the
`reception level of the non-directional antenna 11.
`FIG.5 is a block diagram of the measuring unit of the
`fixed radio apparatus accordingto the first embodiment
`ofthe present invention. In FIG.5, reference number 41
`denotes a filter (FL), 42 an amplifier (AMP), 43 and 44
`phase detectors (PD), 45 an oscillator (OSC), 46 a direc-
`tional coupler (DC), 47 a phase shifter (OSC) of 2, 48
`and 49 square-composition circuits, 50 a register unit, 51
`a correlation unit, 52 a signal processor, 53 a display
`controller, 54 a cathode-ray tube (CRT), 55 a compara-
`tor (COM), 56 a register, 57 a counter, and 58 a distance
`display unit.
`The oscillator 45 generates the signal of the fre-
`quency fig having a very highly stabilized phase. The
`frequency fip is transmitted to the mixers 30 and 38
`through the directional coupler 26, and transmitted to
`the phase detector 43 and 44 through the directional
`coupler 26. Further, the signal of the frequency fi from
`the mixer 24 is added to the phase detectors 43 and 44
`through the amplifier 42. In the CW made,the distance
`measured by the measuring means (comparator 55, reg-
`ister 56 and counter 57) is displayed on the distance
`display unit 58. In the radar hopping modes, the dis-
`tance is measured by the square-composition units 48
`and 49, register unit 50, the correlation unit 51, and the
`signal processor 52. The measured distanceis displayed
`on the display unit 54 through the display control unit
`53.
`FIG.6 is a block diagram of a mobile radio apparatus
`according to a first embodiment of the present inven-
`tion. In FIG. 6, reference number 61 denotes a non-
`
`8
`directional antenna; 62 a circulator (CIR); 63, 71 and 73
`filters (FL); 64 and 72 amplifiers (AMP) having a limit-
`ing function; 65 an attenuator (ATT); 66 a delaycircuit
`(DLY); 67 a decoder (DEC); 68 a switch; 69 an oscilla-
`tor; and 70 a mixer.
`When the non-directional antenna 61 receives the
`signal of the frequency ft (=3000 MHz) from the fixed
`radio apparatus 1, the reception signal is transferred to
`the mixer 70 throughthecirculator 62,the filter 63, the
`amplifier 64, the attenuator 65, and the switch 68. The
`mixer 70 mixes the reception signal with the signal of
`the frequency fi (=10 MHz) generated by the oscillator
`69. The mixer 70 generates the mixed signal fr=ft+fi
`(=3010 MHz) and sendsit the antenna 61 through the
`filter 71r the amplifier 72, the filter 73 and the circulator
`62. This mixed signal is called the returned signal. That
`is, the fixed radio apparatus 1 generates the radio wave
`of the frequency ft to the mobile radio apparatus 2, and
`the mobile radio apparatus returns the signal of the
`frequency fr (=ft+fi) to the fixed radio apparatus 1 as.
`the returned signal to measure the propagation distance.
`The decoder 67 decodes a control code from the
`fixed radio apparatus 1 to change the switch unit 68 so
`as to connect the delay circuit 66. Accordingly, a de-
`layed signal is added to the mixer 70 through the switch
`68. The delay circuit 66 is used to delay the returned
`signal to apparently lengthen the propagation distance
`between the fixed radio apparatus 1 and the mobile
`radio apparatus 2.
`In the CW modeof FIG.4, the frequency ft gener-
`ated by the oscillator 25 is transmitted from the anten-
`nas 11 and 12 through the directional coupler 26, the
`modulator 27, the switch 28, the filter 29, the circulator
`19 and the switch 15. As explained above, the returned
`signal of the frequency fr from the mobile radio appara-
`tus 2 is received by the antennas 11 and 12, and transmit-
`ted to the lobe suppression circuit 17 through the detec-
`tion circuit 16. The side lobe suppression circuit 17
`compares the reception level of the non-directional
`antenna 11 with that of the directional antenna 12, and
`detects the direction of the incoming radio wave based
`on the direction of the main lobe when the reception
`level of the directional antenna 12 is larger than that of
`the non-directional antenna 11.
`In the measuring unit 40, the outputsignal fi mixed by
`the mixer 24 is added to the phase detectors 43 and 44
`throughthefilter 4[and the amplifier 42. The frequency
`fi is directly phase-detected by the frequencyfig in the
`phase detector 43, or phase-detected by the phase dif-
`ference signal of 7/2 in the phase detector 44. When
`two phase detectors 43 and 44 are provided as shown in
`the drawing, a phase blind state does not occurin the
`phase-detected output. However,if either one of phase
`detectors 43 or 44 is eliminated, a phase blind state
`occurs in the phase-detected output. In this case, it is
`possible to measure the propagation distance byutiliz-
`ing this phase blindstate even if only one phase detector
`is provided.
`The measuring means, which does not utilize the
`phase blind state, is formed by two phase detectors 43
`and 44, the square-composition circuits 48 and 49, regis-
`ter 50, and the signal processor 52. Since the phase
`detectors 43 and 44 perform phase detection based on a
`phase reference wave having phase difference of 7/2,
`one output of the phase detection becomes A sin @, the
`other becomes A cos @ (where, 9 denotes the phase
`difference between the reception wave and the phase
`reference signal). Each of square-composition circuits
`
`55
`
`60
`
`65
`
`17
`
`17
`
`

`

`5,381,444
`
`N=(R/Aj)—(R/A2)=(R/AD)—(R/A+. AAD)
`
`9
`10
`48 and 49 converts the phase detection signal into a
`from the generator 25. The transmission signal ft is
`digital value, and the digital value is squared therein.
`transmitted to the mobile radio apparatus 2 through the
`The register 50 composes the above squared value so
`filter 31, the amplifier 32, the switch 28, the filter 29, the
`that the following