Multiband mobile unit communication apparatus

A multiband mobile unit communication apparatus is disclosed which comprises: an antenna for receiving L FRQ bands of M radio wave SIGs modulated by N modulating methods, M>L, M>N, N.gtoreq.L; a frequency synthesizer for generating a LO SIG; an IF SIG generation CKT for generating M IF SIGs using the LO SIG, the FRQ synthesizer generating the LO SIG such that the M IF SIGs have the same intermediate FRQ; a SW CKT for selectively outputting N IF SIGs modulated by the N modulating methods respectively out of the M IF SIGs; N filters for filtering outputs of N IF SIGs from the SW CKT and outputting N filtered IF SIGs respectively; a SW responsive to a SW CONT signal for selectively outputting one of the N filtered IF SIGs; and a quadrature demodulator for quadrature-demodulating one of N filtered IF SIGs and outputting baseband SIG. Different frequency bands of received signals are converted into IF SIGs having the same intermediate frequency. Moreover, different frequency bands of received signals which are modulated by the same method are filtered by the same IF filter.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a multiband mobile unit communication apparatus.
 2. Description of the Prior Art
 A mobile unit communication apparatus for communicating with a third party
 through a base station and a network is known.
 Such a mobile unit communication apparatus is disclosed in Japanese patent
 application provisional publication No. 6-132849 as RADIO EQUIPMENT AND
 PORTABLE TELEPHONE SET. FIG. 3 is a block diagram of this prior art mobile
 unit communication apparatus. In this prior art mobile unit communication
 apparatus, a smaller number of local oscillators are used. To provide
 transmission and reception through different frequencies respectively, a
 local oscillator 11 capable of directly or indirectly oscillating a
 fundamental wave and its multiple wave is used, and a local oscillator 6
 is used for transmission and reception commonly.
 SUMMARY OF THE INVENTION
 The aim of the present invention is to provide an improved multiband mobile
 unit communication apparatus.
 According to the present invention, a first multiband mobile unit
 communication apparatus is provided, which comprises: an antenna for
 receiving first and second frequency bands of radio wave signals modulated
 by the same modulating method; a local oscillation signal generation
 circuit for generating a local oscillation signal; a first mixer for
 mixing the received first frequency band of radio wave signal with the
 local oscillation signal; a second mixer for mixing the received second
 frequency band of radio wave signal with the local oscillation signal; a
 switch for supplying an output from the first mixer in a first mode and
 supplying an output from the second mixer in a second mode; and a filter
 for filtering an output of the switch and outputting a first intermediate
 frequency signal in the first mode and a second intermediate frequency
 signal in the second mode, the local oscillation signal generation circuit
 generating the local oscillation signal such that the first intermediate
 frequency signal has the same frequency as the second intermediate
 frequency signal.
 According to the present invention, a second multiband mobile unit
 communication apparatus is provided which comprises: an antenna for
 receiving L frequency bands of M radio wave signals modulated by N
 modulating methods, L, M, and N being natural numbers, M&gt;L, M&gt;N,
 N.gtoreq.2; a frequency synthesizer for generating a local oscillation
 signal; an intermediate frequency signal generation circuit for generating
 M intermediate frequency signals using the local oscillation signal, the
 frequency synthesizer generating the local oscillation signal such that
 the M intermediate frequency signals have the same intermediate frequency;
 a switching circuit for selectively outputting N intermediate frequency
 signals modulated by the N modulating methods respectively out of the M
 intermediate frequency signals; and N filters for filtering outputs of N
 intermediate frequency signals from the switching circuit and outputting N
 filtered intermediate frequency signals respectively.
 The second multiband mobile unit communication apparatus may further
 comprise a switching circuit responsive to a switching control signal for
 selectively outputting one of the N filtered intermediate frequency
 signals and a quadrature demodulator for quadrature-demodulating one of N
 filtered intermediate frequency signals and outputting baseband signal.
 According to the present invention, a third multiband mobile unit
 communication apparatus is provided which comprises: an antenna for
 receiving L frequency bands of M radio wave signals modulated by N
 modulating methods, L, M, and N being natural numbers, M&gt;L, M&gt;N,
 N.gtoreq.L; a frequency synthesizer for generating a local oscillation
 signal; an intermediate frequency signal generation circuit for generating
 M intermediate frequency signals using the local oscillation signal, the
 frequency synthesizer generating the local oscillation signal such that
 the M intermediate frequency signals have the same intermediate frequency;
 a switching circuit for selectively outputting N intermediate frequency
 signals modulated by the N modulating methods respectively out of the M
 intermediate frequency signals; N filters for filtering outputs of N
 intermediate frequency signals from the switching circuit and outputting N
 filtered intermediate frequency signals respectively; a switching circuit
 responsive to a switching control signal for selectively outputting one of
 the N filtered intermediate frequency signals; and a quadrature
 demodulator for quadrature-demodulating one of N filtered intermediate
 frequency signals and outputting baseband signal.

The same or corresponding elements or parts are designated with like
 references throughout the drawings.
 DETAILED DESCRIPTION OF THE INVENTION
 Hereinbelow will be described a first embodiment of this invention.
 FIG. 1 is a block diagram of a multiband mobile unit communication
 apparatus of the first embodiment.
 The multiband mobile unit communication apparatus of the first embodiment
 operates in a mobile unit communication system X using a radio frequency
 band A through a communication method .alpha., a mobile communication
 system Y using the radio wave frequency band A through a communication
 method .beta., and a mobile unit communication system Z using a radio wave
 frequency band B through through communication method .beta..
 The multiband mobile unit communication apparatus of the first embodiment
 comprises a transmission portion, a receiving portion, duplexers 2 and 3
 for providing separation between the transmission portion and the
 receiving portion, and an antenna 1 for transmission and receiving radio
 wave signals.
 The transmission portion includes: low pass filters 14 and 15 for removing
 unnecessary components in transmission I and Q signals, a quadrature
 modulator 13 for quadrature-modulating the transmission I and Q signals
 from the low pass filters 14 and 15 with a local oscillation signal from a
 frequency synthesizer 34 responsive to a frequency control signal 53, a
 variable gain amplifier 12 for amplifying an output of the quadrature
 modulator 13 with its gain controlled, a low pass filter 11 for removing
 unnecessary components in an output of the variable gain amplifier 12, a
 transmission mixer 10 for up-converting the transmission signal from the
 low pass filter 11 into a first or second high frequency transmission
 signal using an oscillation signal from a frequency synthesizer 18, a
 variable gain amplifier 9 for amplifying the high frequency transmission
 signal from the mixer 10 with its gain controlled, power amplifiers 6 and
 7, a switch 8 for outputting either the first high frequency transmission
 signal to the power amplifier 6 or the second high frequency transmission
 signals to the power amplifier 7, and isolators 4 and 5 for isolating
 duplexers 2 and 3 from the power amplifiers 6 and 7.
 The duplexers 2 and 3 provide simultaneous transmission and receiving
 operations. The antenna 1 transmits either of the transmission signals
 TRDX, TRDY, TRDZ from either of the duplexer 2 or 3 and receives reception
 radio wave signals RRDX, RRDY, and/or RRDZ. The reception signal from the
 antenna 1 is supplied to the duplexers 2 and 3.
 The receiving portion includes a low noise amplifier 19 for amplifying the
 reception radio wave signal RRDX or RRDY from the duplexer 2, a low noise
 amplifier 20 for amplifying the reception radio wave signal signal RRDZ
 from the duplexer 3, a receiving mixer 21 for mixing a local oscillation
 signal from the frequency synthesizer 18 with an output signal from the
 low noise amplifier 19 to generate an intermediate frequency signal IFX
 corresponding to the reception radio wave signal RRDX, a receiving mixer
 22 for mixing the local oscillation signal from the frequency synthesizer
 18 with the output signal from the low noise amplifier 19 to generate an
 intermediate frequency IFY signal corresponding to the reception radio
 wave signal RRDY, a receiving mixer 23 for mixing the local oscillation
 signal from the frequency synthesizer 18 with an output signal from the
 low noise amplifier 20 to generate an intermediate frequency signal IFZ
 corresponding to the reception radio wave signal RRDZ, an intermediate
 frequency switch 36 for outputting either of the intermediate frequency
 signal IFY or IFZ, band pass filters 24 and 25 for removing unnecessary
 components in the intermediate frequency signals IFX and and an output of
 the intermediate frequency switch 36 (IFY or IFZ) respectively, an
 intermediate frequency switch 26 for outputting either of outputs of the
 band pass filters 24 or 25, a variable gain amplifier 27 for amplifying an
 output of the intermediate frequency switch 26 with its gain controlled, a
 frequency synthesizer 35 for generating a local oscillation signal, a
 quadrature demodulation circuit 28 for quadrature-demodulating an output
 of the variable gain amplifier 27 with the local oscillation signal from
 the frequency synthesizer 35 and outputting I and Q baseband signals, low
 pass filters 29 and 30 for removing unnecessary components in the I and Q
 base band signals. Either of the I and Q base band signal from the
 quadrature demodulator 28 is also used for frequency modulation reception.
 That is, the Q base band signal from the quadrature demodulator 28 is
 supplied to a band pass filter 38 for FM demodulating the Q base band
 signal, and a limiting amplifier 39 for limiting an amplitude of the FM
 signal from the band bass filter 38.
 In this multiband mobile unit communication apparatus, the same
 intermediate frequency filter 25 is commonly used for receiving the radio
 wave signals subjected to the same modulation method .beta. but having
 different frequency bands A and B. That is, the intermediate frequency
 filter 25 is provided for generating the intermediate frequency signal
 from the reception radio wave signal RRDY or RRDZ subjected to the same
 modulation method .alpha.. In other words, the number of the intermediate
 frequency filters 24 and 25 corresponds to that of the modulation methods
 .alpha. and .beta. of the reception signals. The frequency synthesizer 18
 generates the local oscillation signal, that is, controls the local
 oscillation frequency, such that the intermediate frequency signals from
 the receiving mixers 21, 22, and 23 have the same frequency. The
 intermediate frequency switch 36 responsive to a switching control signal
 A/B outputs the intermediate frequency signal corresponding to the mobile
 unit communication system Y from the receiving mixer 22 when the reception
 radio wave signal RRDY is received and the intermediate frequency signal
 corresponding to the mobile unit communication system Z from the receiving
 mixer 23 when the reception radio wave signal RRDZ is received. The
 intermediate frequency switch 26 responsive to a switching control signal
 .alpha./.beta. outputs the intermediate frequency signal corresponding to
 the mobile unit communication system X using the modulation method .alpha.
 from the receiving mixer 22 when the reception radio wave signal RRDX is
 received and the intermediate frequency signal subjected to the modulation
 method .beta. from the receiving mixer 23.
 The I and Q transmission baseband signals from input terminals 16 and 17
 are modulated by the quadrature modulator 13, and up-converted by the
 transmission mixer 10, gain-adjusted by the variable gain amplifier 9, and
 is supplied to the power amplifiers 6 and 7 via the high frequency switch
 8. More specifically, the power amplifier 6 is used for transmitting the
 transmission signal toward the mobile unit communication systems X and Y
 using the same frequency band A and the power amplifier 7 is used for
 transmitting the transmission signal toward the mobile unit communication
 system Z using the frequency band B. The antenna 1 transmits the
 transmission signal from the power amplifier 6 or 7 via the isolator 4 or
 5 and the duplexer 2 or 3 to a base station.
 On the other hand, a portion of or all of the reception signals RRDX, RRDY
 RRDZ are received by the antenna 1. The reception signals RRDX and RRDY
 are supplied to the low noise amplifier 19 through the duplexer 2 and the
 reception signal RRDZ from the antenna 1 is supplied to the low noise
 amplifier through the duplexer 3. The low noise amplifier 19 has a
 frequency characteristic corresponding to the frequency band A and the low
 noise amplifier 20 has a frequency characteristic corresponding to the
 frequency band B. The receiving mixers 21 to 23 convert the reception
 signals RRDX, RRDY, and RRDZ from the low noise amplifiers 19 and 20 into
 the intermediate frequency signals every frequency bands and every
 modulation method.
 The frequency synthesizer 18 generates the local oscillation signal 18a,
 that is, controls the local oscillation frequency, such that the
 intermediate frequency signals from the receiving mixers 21, 22, and 23
 have the same frequency. The receiving mixer 21 is used for receiving the
 reception radio wave signal RRDX from the mobile unit communication system
 X, the receiving mixer 22 is used for receiving the reception radio wave
 signal RRDY from the mobile unit communication system Y, and the mixer 23
 is used for receiving the reception radio wave signal RRDZ from the mobile
 unit communication system Z.
 The intermediate frequency filters 24 and 25 are provided in accordance
 with the number of the modulation methods. More specifically, the
 intermediate frequency filter 24 corresponds to the mobile unit
 communication system X using the modulation method .alpha., the
 intermediate frequency filter 25 corresponds to the mobile unit
 communication system Y or Z using the modulation method .beta..
 The intermediate frequency switch 36 outputs the output of the receiving
 mixer 22 when this mobile unit communication apparatus receives the
 reception radio wave signal RRDY from the mobile unit communication system
 Y and outputs the output of the receiving mixer 23 when this mobile unit
 communication apparatus receives the reception radio wave signal RRDZ from
 the mobile unit communication system Z.
 The intermediate frequency switch 26 selects the output of the intermediate
 frequency filter 24 when the modulation method of the mobile unit
 communication system is a and selects the output of the intermediate
 frequency filter 25 when the modulation method of the mobile unit
 communication system is .beta.. The output of the intermediate frequency
 switch 26 is gain-adjusted by the variable gain amplifier 27, and then, is
 converted into I and Q demodulation signals by the quadrature demodulator
 28.
 If the received signal is the FM signal, the quadrature demodulator 28 is
 used as a receiving second mixer to convert it into a second FM
 intermediate frequency signal and the Q signal from the quadrature
 demodulator 28 is demodulated by the bandpass filter 38 for FM signals and
 the limiter amplifier 39 and outputted as FM intermediate frequency
 signal. In this case, the second local oscillator 35 has a synthesizer
 structure to operate for the I and Q demodulation and the FM intermediate
 frequency demodulation.
 In this mobile unit communication apparatus, it is assumed that:
 transmission and receiving center frequencies in the mobile unit
 communication system X using the radio frequency band A and the
 communication method .alpha. are 835 MHz and 880 MHz respectively;
 transmission and receiving center frequencies in the mobile unit
 communication system Y using the radio frequency band A and the
 communication method .beta. are 835 MHz and 880 MHz respectively; and
 transmission and receiving center frequencies in the mobile unit
 communication system Z using the radio frequency band B and the
 communication method .beta. are 1880 MHz and 1960 MHz respectively.
 The intermediate frequencies among the respective systems are equalized by
 providing a frequency relation as shown in table 1 with respect to the
 center frequency fL1 of the first local oscillator 18 corresponding to
 respective radio wave frequency bands, the receiving intermediate
 frequency fIF, and the local oscillation frequency fmod for transmission.
 Actually, an oscillation frequency of the voltage controlled oscillator 34
 is twice fmod because the quadrature modulator 13 includes a 1/2-frequency
 divider. Moreover, it is assumed that the modulation method .alpha. is a
 narrow band modulation method such as the FM modulation method and the
 communication method .beta. is a broad band modulation method such as the
 spread spectrum communication method.
 TABLE 1
 COM FRQ fL1 fIF fmod
 METHOD BAND (MHz) (MHz) (MHz)
 MOBILE .alpha. A 1090 210 255
 COM SYS
 X
 MOBILE .beta. A 1090 210 255
 COM SYS
 Y
 MOBILE .beta. B 1750 210 130
 COM SYS
 Z
 Then, the following relation provides an equalized receiving intermediate
 frequencies.
EQU ftxX=fL1(X)-fmod(X)=ftxY
EQU frxX=fL1(x)-fIF(X)=frxY
EQU ftxZ=fL1(Z)+fmod(Z)
EQU frxZ=fL1(Z)+fIF(Z) (1)
 This frequency relation is an example and it is sufficient to determine the
 fl1 and fmod such that ftx=fL1.+-.fmod, frx=fL1.+-.fIF, and fIFs become
 the same among respect communication methods.
 As mentioned, the multiband mobile unit communication apparatus of the
 first embodiment comprises: the antenna 1 for receiving L frequency bands
 of M radio wave signals modulated by N modulating methods, L, M, and N
 being natural numbers, M&gt;L, M&gt;N, N.gtoreq.L; the frequency synthesizer 18
 for generating the local oscillation signal 18a; an intermediate frequency
 signal generation circuit 51 including the low noise amplifiers 19 and 20,
 and the receiving mixers 21 to 23 for generating M intermediate frequency
 signals using the local oscillation signal 18a, the frequency synthesizer
 18 generating the local oscillation signal 18a such that the M
 intermediate frequency signals have the same intermediate frequency; the
 switching circuit 52 including the line 21a between the receiving mixer 21
 and the intermediate frequency filter 24 and the intermediate frequency
 switch 36 for selectively outputting N intermediate frequency signals
 modulated by the N modulating methods respectively out of the M
 intermediate frequency signals; the N filters 24 and 25 for filtering
 outputs of N intermediate frequency signals from the switching circuit 52
 and outputting N filtered intermediate frequency signals respectively; the
 intermediate frequency switch 26 responsive to a switching control signal
 .alpha./.beta. for selectively outputting one of the N filtered
 intermediate frequency signals; and the quadrature demodulator 28 for
 quadrature-demodulating one of N filtered intermediate frequency signals
 and outputting baseband signal.
 As mentioned, different frequency bands of received signals are converted
 into the intermediate frequency signals having the same intermediate
 frequency. Moreover, different frequency bands of received signals which
 are modulated by the same method are filtered by the same intermediate
 frequency filter 25.
 A second embodiment will be described.
 FIG. 2 is a block diagram of a multiband mobile unit communication
 apparatus of the second embodiment.
 The multiband mobile unit communication apparatus of the second embodiment
 has substantially the same structure as that of the first embodiment. The
 difference is that an FM demodulator 33 replaces the band pass filter 38
 and the limiter 39 and a local oscillator 37 having a fixed local
 oscillation frequency replaces the frequency synthesizer 35.
 The FM demodulator 33 comprises a differentiator 33a for differentiating
 the output of a mixer 28a, that is, the I signal, and a divider 33b for
 dividing an output of the output of the differentiator 33a by an output of
 the mixer 28b, that is, the Q signal to output a frequency demodulated
 baseband signal.
 The differentiator 33a differentiates the output of the mixer 28a, that is,
 the I signal. The divider 33b divides the output of the output of the
 differentiator 33a by the Q signal and outputs the frequency demodulated
 baseband signal.
 In this embodiment, the frequency of a reference signal for the quadrature
 demodulator 28 can be fixed though the demodulation method is changed.