JP2001345727A - Synthesizer and transmitting/receiving circuit comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure isolation between transmission and reception while enhancing the value and reducing the size of a circuit and power consumption by decreasing the number of high frequency VCOs and intermediate frequency VCOs. SOLUTION: In the synthesizer circuit of a dual mode transmitting/receiving circuit communicating in two different radio frequency bands, an IF local signal is generated by dividing the frequency of oscillation signal of a VCO2 for IF individually for transmission and reception. With regard to an RF local signal corresponding to a high frequency side system (W-CDMA), oscillation signal of a VCO1 for RF is utilized as it is. With regard to an RF local signal corresponding to a low frequency side system (DCS-1800), frequency of oscillation signal of the VCO2 for IF is divided by N3 through a frequency divider 9 to produce a signal having a frequency corresponding to the frequency shift width which is then mixed and shifted to generate the oscillation signal of the VCO1 for RF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication terminal device such as a portable telephone, and more particularly to a synthesizer provided in a mobile communication terminal device adapted to a plurality of mobile communication systems using different frequency bands or wireless communication systems. And a transmission / reception circuit including the synthesizer.

[0002]

2. Description of the Related Art In recent years, in a mobile communication system, traffic has become extremely high in some service areas due to the rapid spread of mobile communication terminals, and a problem has arisen that a communication channel cannot be secured.

[0003] Therefore, a so-called multi-band or multi-mode mobile radio terminal capable of commonly accessing a plurality of systems using different frequency bands or radio communication systems has been proposed. However, this type of conventionally considered mobile communication terminal has a wireless unit provided with a plurality of sets of circuits corresponding to different use frequency bands of each system. For this reason, the circuit configuration of the radio unit is large and heavy, the power consumption is large, and the terminal is expensive, which does not meet the needs of the market.

Therefore, recently, among circuit components provided for each system, large components such as a voltage controlled oscillator (VCO), a PLL, and a filter, which constitute a synthesizer, are commonly used, so that a radio section can be used. Various attempts have been made to reduce the size and power consumption.

For example, GSM (Global System for Mobi)
le Communication) system and DCS-1800 (Di
gital Cellular System at 1800 MHz).
As disclosed in U.S. Pat. No. 4,131,132, a first local signal corresponding to band A of one system is generated by a synthesizer, and a second local signal corresponding to band B of the other system is generated using the second local signal. It is generated by mixing one local signal with another local signal and up-converting it. With this configuration, the number of synthesizers can be reduced to one, and the circuit configuration can be reduced in size and power consumption can be reduced accordingly.

However, in such a circuit configuration, the frequency of the intermediate frequency (IF) signal is common to transmission and reception. For this reason, for example, CDMA (Code Division Multiple Acces)
s) In a terminal that performs transmission and reception at the same time, such as a mobile communication terminal used in a system adopting the system, there is a problem that isolation between transmission and reception cannot be obtained and performance deteriorates. Also,
The local signal of one system is generated by mixing an oscillation signal of the VCO in the radio frequency (RF) band and a signal obtained by multiplying the oscillation signal of the VCO in the intermediate frequency (IF) band by an integer. It is necessary to set the oscillation frequency (IF signal frequency) of the VCO to be low, and the frequency configuration of the circuit is limited. Therefore, it cannot be applied to a multi-band / multi-mode transmission / reception circuit including a communication system that performs transmission / reception simultaneously.

On the other hand, mobile communication terminals commonly used in a plurality of systems including a system for simultaneous transmission and reception include, for example, a multi-band radio apparatus described in JP-T-10-507044 and JP-A-11-112382. As in the dual-band wireless communication device described in
A plurality of band VCOs and a plurality of IF band VCOs are provided.

However, in mobile communication terminals such as mobile phones, further miniaturization, lower power consumption, and lower prices are required in the future. Correspondingly, it is necessary to configure a circuit without providing individual circuit components, and it is particularly desired to share large and expensive components.

[0009]

As described above, the conventional circuit is considered to be applied to a plurality of communication systems including a system that simultaneously performs transmission and reception.
There is a problem that isolation between transmission and reception cannot be ensured, and a plurality of VCOs are required, resulting in an increase in circuit configuration, an increase in power consumption, an increase in cost, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mobile communication terminal commonly used for a plurality of systems including a communication system for performing transmission and reception at the same time. Synthesizer for reducing the number of VCOs and VCOs for intermediate frequency, miniaturizing the circuit, reducing power consumption, and reducing the price, while ensuring isolation between transmission and reception, and a transmission / reception circuit equipped with this synthesizer Is to provide.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a first communication system in which different communication bands are allocated and these communication bands do not become integral multiples of each other.
And a synthesizer for generating first and second radio frequency local oscillation signals and intermediate frequency local oscillation signals corresponding to the first and second radio communication systems, respectively, using PLL means. First radio frequency local oscillation means for generating a local oscillation signal; intermediate frequency local oscillation means for generating the first and second intermediate frequency local oscillation signals using PLL means; Means of P
A shift width for generating a signal representing a frequency shift width by dividing a signal generated by the LL circuit by a frequency division number set based on a frequency difference of a communication band between the first and second systems. Generating means, mixing the first local oscillation signal for radio frequency generated by the first local oscillation means for radio frequency with the signal generated by the shift width generating means, and And second radio frequency local oscillation means for generating a radio frequency local oscillation signal.

That is, the synthesizer according to the present invention uses one RF VCO for the first local oscillator for radio frequency and one VCO for the IF for the intermediate frequency local oscillator.
The RF VCO generates a radio frequency local signal for the first communication system. On the other hand, the radio frequency local signal for the second communication system is generated by a frequency divider and a mixer as frequency shift width generating means. That is, the oscillation signal of the IF VCO is frequency-divided by a frequency divider to generate a signal representing a frequency shift width, and this signal is mixed with the oscillation signal of the RF VCO and converted upward or downward, whereby A radio frequency local signal for the second communication system is generated.

In the means for generating an IF local signal, the oscillation frequency of the IF VCO is set to an integral multiple of the IF local signal frequency of a system that performs simultaneous transmission and reception.
A signal obtained by dividing the oscillation signal of the IF VCO is configured to be a transmission / reception IF local signal. At this time, I
The frequency difference of the F local signal is set to the transmission / reception interval of the radio communication frequency of the simultaneous transmission / reception communication system.

For example, in a dual mode mobile communication terminal that performs communication using two different communication systems, the radio frequency bands between the two communication systems are not far apart, and one is a simultaneous transmission / reception communication and the other is a simultaneous transmission / reception. In the case of transmission / reception time division communication, the frequency difference between the transmission / reception IF local signal is set to be the frequency interval between the transmission / reception radio frequencies of the simultaneous transmission / reception communication system, and the RF local signal frequency is made common to make the RF VCO The oscillation signal is used as it is as an RF local signal. At this time, the IF local signal frequency is set to be an integer multiple of the IF local signal frequency.
An oscillation signal of the F VCO is generated by dividing the frequency by an integer.

In another transmission / reception time division communication system, an IF
The oscillation signal of the VCO for RF is divided and mixed with the oscillation signal of the VCO for RF, and the output signal of the up-conversion and / or the down-conversion or both of them is transmitted or received, respectively.
Used as a local signal. At this time, the IF local signal is common to the case of the simultaneous transmission and reception communication system.

In a dual mode mobile communication terminal that communicates with two communication systems, when the radio frequency bands of the two communication systems are far apart, one is simultaneous transmission and reception and the other is transmission / reception time division. In the case of communication, as in the system described above, one of the RF local signals is a signal obtained by dividing the oscillation signal of the IF VCO and the RF VCO.
Generated by mixing with the CO oscillation signal,
The other RF local signal is generated without mixing.
However, one of the two local signals is greatly shifted after mixing or by the RF VCO output by integer division or multiple. In other words, the local signal frequency is largely shifted to generate two modes of RF local signals whose radio frequencies are far apart.

Further, in a multimode terminal that performs communication by a plurality of systems, even when a plurality of simultaneous transmission and reception systems are included, an RF local signal is generated in the same manner as the above-described means. In the frequency configuration of the IF local signal, the frequency difference between the transmitted and received IF local signals is set to the transmission and reception frequency interval of the system that performs the simultaneous transmission and reception, and the oscillation frequency of the IF VCO is set to an integral multiple of the IF local signal frequency. And an IF local signal is generated by dividing the oscillation signal of the IF VCO.

Further, the frequency division ratio is set so that the oscillation frequency of the IF VCO in each system becomes closer,
Thereby, each IF local signal frequency can be generated by one IF VCO. At this time, since IF filters are prepared for systems having different channel bandwidths, it is not necessary to match the IF local signal frequencies in each system.

Therefore, according to the synthesizer of the present invention, even in a multi-band / multi-mode portable terminal including a simultaneous transmission / reception communication system, one synthesizer circuit is provided.
Since it can be configured with one RF VCO and one IF VCO, it is possible to provide a synthesizer circuit and a transmission / reception circuit suitable for a mobile communication terminal that are compact, lightweight, have low power consumption, and are inexpensive without deteriorating performance. .

[0020]

(First Embodiment) FIG. 1 is a circuit block diagram showing a first embodiment of a synthesizer according to the present invention. This synthesizer has a first and a second
VCOs 1 and 2, a reference oscillator 3, a PLL circuit 4,
Loop filters 5 and 6 and frequency dividing phase shifters 7 and 8 are provided.

The reference oscillator 3 comprises, for example, a temperature controlled crystal oscillator (TCXO), outputs a reference oscillation signal having a predetermined frequency, and supplies it to the PLL circuit 4.

The PLL circuit 4 compares the phase of the oscillation output of the first and second VCOs 1 and 2 with the reference oscillation signal output from the reference oscillator 3, and compares the comparison output with the loop filters 5 and 6, respectively. Output to

FIG. 2 is a circuit block diagram showing the configuration of the PLL circuit. The PLL circuit 4 includes first and second PLLs having the same configuration. First PLL
Are a signal obtained by dividing the reference oscillation signal output from the reference oscillator 3 by 1 / M1 by the frequency divider 11, and a signal obtained by dividing the oscillation output of the first VCO 1 by 1 / M3 by the frequency divider 17. Are compared by a phase comparator (PD) 13 and a first VCO is charged by a charge pump circuit (CP) 15 based on the phase comparison signal.
1 to generate a control signal for controlling the oscillation frequency.

The second PLL outputs a signal obtained by dividing the reference oscillation signal output from the reference oscillator 3 to 1 / M 2 by the frequency divider 12 and an oscillation output of the second VCO 2 by the frequency divider 18. M
4 is compared by a phase comparator (PD) 14 with a control signal for controlling the oscillation frequency of the second VCO 2 by a charge pump circuit (CP) 16 based on the phase comparison signal. Generate

The loop filters 5 and 6 respectively smooth the control signals output from the first PLL and the second PLL, and apply the smoothed control signals to the first VCO 1.
And to the second VCO 2.

The first VCO 1 is a dual mode transmission / reception circuit for generating a radio frequency (RF) local signal corresponding to one of the two modes. The first VCO 1 controls the loop filter 5 from the first PLL. A local signal for RF having a frequency corresponding to the control signal supplied via the RF signal is generated. This local signal for RF converts a received RF signal into a received intermediate frequency (IF) signal,
Used to up-convert a transmission IF signal to a transmission RF signal.

The second VCO 2 generates a local signal for an intermediate frequency (IF) having a frequency corresponding to a control signal supplied from the second PLL via the loop filter 6. The local signal for this IF is, for example, a reception IF
It is used for down-converting a signal to a reception baseband (BB) signal and for up-converting a transmission BB signal to a transmission IF signal.

The frequency dividing phase shifter 7 is provided with a second V for the IF band.
After dividing the local signal generated from CO2 by 1 / N1, an IF local signal having a phase difference of 90 degrees is generated. This IF local signal is used, for example, as an IF local signal of a receiving system.

The frequency dividing phase shifter 8 divides the local signal generated from the second VCO 2 for the IF band into 1 / N2, and then, as in the case of the frequency dividing phase shifter 7 described above, makes a 90-degree difference from each other. Is generated. This IF local signal is used, for example, as an IF local signal of a transmission system.

By the way, the synthesizer of this embodiment is
A dual-mode transmission / reception circuit includes a frequency divider 9 and a mixer 10 for generating an RF local signal corresponding to the other mode.

The frequency divider 9 divides the local signal generated from the IF VCO 2 by 1 / N3. Mixer 10
Mixes the RF local signal generated from the RF VCO 1 with the frequency-divided signal output from the frequency divider 9 to reduce the frequency of the RF local signal to the frequency-divided signal. Shift by the frequency of Then, a signal generated by this frequency shift is output as an RF local signal corresponding to the other mode.

Next, the operation of the synthesizer configured as described above will be described. Here, W-CDMA (R
x = 2110 to 2170 MHz, Tx = 1920 to 198
0 MHz) and DCS-1800 (Rx = 1805-18
(80 MHz, Tx = 1710 to 1785 MHz) will be described as an example.

Now, suppose that the signal frequency of each unit is
Signal frequency = RxRF, transmission RF signal frequency = TxR
F, reception IF signal frequency = RxIF, transmission IF signal frequency = TxIF, reception RF local signal frequency = RxRF
Lo, transmission RF local signal frequency = TxRFLo, reception IF local signal frequency = RxIFLo, transmission IF local signal frequency = TxIFLo.

The interval between transmission and reception of the W-CDMA radio channel frequency is 190 MHz, and the interval between transmission and reception of the DCS-1800 radio channel frequency is 95 MHz. Therefore,
If the oscillation frequency of the IF VCO 2 is set to a multiple of the frequency of the transmission / reception interval, an IF local signal can be generated for both transmission and reception by dividing the output signal of the IF VCO 2.

Here, the oscillation frequency of the IF VCO 2 is set to 7
60 MHz, the reception IF signal frequency is 190 MHz,
When the F signal frequency is set to 380 MHz, the frequency division ratio N1 of the reception frequency division phase shifter 7 is set to 4, and the frequency division ratio N2 of the transmission frequency division phase shifter 8 is set to 2. Then, the reception I
The F local signal frequency RxIFLo and the transmission IF local signal frequency TxIFLo are respectively RxIFLo = 760 MHz / 4 = 190 MHz TxIFLo = 760 MHz / 2 = 380 MHz.

When the transmitting and receiving RF local signal frequency is set to be higher than the radio channel frequency, the RF local signal is represented by (W-CDMA) RxRFLo = RxRF + RxIF = 2300 to 236
0MHz TxRFLo = TxRF + TxIF = 2300-236
0MHz (DCS-1800) RxRFLo = RxRF + RxIF = 1995-207
0MHz TxRFLo = TxRF + TxIF = 2090-216
5 MHz.

The W-CDMA RF local signal frequency RxRFLo is used as the oscillation frequency of the RF VCO 1 as it is, and the DCS-1800 RF local signal frequency Rx
RFLo is the output of the mixer 10. Here, the frequency divider 9
If the frequency division ratio N3 is 4 at reception and 8 at transmission, and each of the transmission and reception is a local down-converted frequency component of the mixer 10, the RF-VCO oscillation frequency of the DCS-1800 is as follows: at reception = RxRFLo + (760 MHz / 4 ) = 2185
２２2260 MHz When transmitting = TxRFLo + (760 MHz / 8) = 2185
２２2260 MHz.

Therefore, the oscillation frequency range of the RF VCO 1 is 2185 to 2360 MHz, and the center frequency is 227
2.5MHz, oscillation frequency width is 175MHz (about 7.7%)
Becomes It is generally said that the oscillation frequency width of the VCO is up to about 10% of the center frequency, which is a range that can be sufficiently realized.

As described above, in the first embodiment, in the synthesizer of the dual mode transmitting / receiving circuit that communicates in two different radio frequency bands, the IF local signal is generated by separately dividing the oscillation signal of the IF VCO 2 for transmission and reception. are doing. The RF local signal corresponding to the high-frequency system (W-CDMA) uses the oscillation signal of the RF VCO 1 as it is, and the low-frequency system (DCS-180).
0) corresponds to the IF VCO 2
Is divided by the frequency divider 9 into 1 / N3 to generate a signal frequency corresponding to the frequency shift width.
Is generated by mixing the above oscillation signal with this signal frequency and shifting it.

Accordingly, one RF VCO 1 and one RF VCO 1
A local signal for communication in a plurality of radio channel frequency bands can be generated only by using a plurality of IF VCOs 2, and a synthesizer that is smaller, lighter, less expensive, and consumes less power than conventional synthesizers is provided. be able to.

(Second Embodiment) The second embodiment of the present invention relates to the W-CDMA and DCS described in the first embodiment.
For example, when the radio channel frequency between the systems is not close as in the dual mode of -1800, for example, W-CDM
A (Rx = 2110-2170 MHz, Tx = 1920-
1980 MHz) and GSM (Rx = 925-960 MHz, T
x = 880-915 MHz) like the dual mode,
FIG. 2 shows an example of a synthesizer that can be used when the radio channel frequencies between systems are far apart to some extent.

FIG. 3 is a circuit block diagram showing the configuration of the synthesizer according to the second embodiment. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted.

At the subsequent stage of the mixer 10, a frequency divider 21 is further provided.
Is provided. The frequency divider 21 divides the signal frequency output from the mixer 10 by 1 / N4, so that the frequency is higher than the RF local signal frequency output from the RF VCO 1 corresponding to the high-frequency side system. Generate an RF local signal frequency corresponding to the remote lower frequency system.

Here, the configuration will be briefly described taking a dual mode of W-CDMA and GSM as an example. The IF system has the same configuration as that of FIG. That is, IF
The oscillation frequency of the VCO 2 for use is 760 MHz, the dividing ratio N1 of the dividing phase shifter 7 is 4, and the dividing ratio N2 of the dividing phase shifter 8 is 2
Set to each. A circuit for generating a W-CDMA RF local signal has the same configuration as that of the embodiment shown in FIG. On the other hand, a circuit for generating a GSM RF local signal, when the frequency is set above the radio channel frequency, is as follows: (GSM) RxRFLo = RxRF + RxIF = 1115 to 115
0 MHz TxRFLo = TxRF + TxIF = 1260-129
It looks like 5MHz.

The signal frequency output from the mixer 10 is as follows: RxRFLo × 2 = 2230-2300 MHz TxRFLo × 2 = 2520-2590 MHz

This signal frequency is converted to an RF VC
The frequency is the sum of the oscillation frequency of O1 and the output signal of the frequency divider 9 (upward conversion), and the difference between the oscillation frequency of the RF VCO 1 and the output signal of the frequency divider 9 (downward conversion) during transmission. Assuming that the frequency division ratio N3 of the frequency divider 9 is 8 when receiving and 4 when transmitting, the RF VCO in the GSM mode
The oscillation frequency of 1 is as follows: at reception = (2230-2300) + 760/8 = 232
When transmitting 5 to 2395 MHz = (2520 to 2590)-760/4 = 233
0 to 2400 MHz.

The oscillation frequency range of the RF VCO 1 during W-CDMA is 2300 to 2360 MHz,
The oscillation frequency range for both modes of CO1 is 2300
It becomes 2400 MHz. At this time, the frequency variable width of the RF VCO 1 is 100 MHz (about 4.3%), which is a width that can be sufficiently realized.

As described above, even in a transmission / reception circuit used in a dual mode system in which the radio channel frequency is relatively large between the systems, one RF VCO 1
And one IF VCO 2 can generate a local signal corresponding to each system. Therefore, as in the first embodiment, a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit can be provided.

(Third Embodiment) A third embodiment of the present invention is a modification of the second embodiment, and is a transmission / reception circuit of a dual mode system in which radio channel frequencies between systems are relatively far apart. In the synthesizer used, a frequency divider is provided on a path of the RF local signal frequency from the RF VCO 1 to the mixer 10 in order to generate an RF local signal frequency corresponding to a low-frequency side system.

FIG. 4 is a circuit block diagram showing a configuration of a synthesizer according to the third embodiment.
The same reference numerals are given to the same parts as those described above, and the detailed description is omitted.

Between the VCO 1 for RF and the mixer 10,
A frequency divider 22 is interposed. The frequency divider 22 converts the RF local signal frequency generated by the RF VCO 1 to 1 / N4
And supplied to the mixer 10. The mixer 10 mixes the RF local signal frequency-divided by the frequency divider 22 with the frequency-divided signal output from the frequency shift width setting frequency divider 9 to thereby provide a low-frequency system. Is generated.

Therefore, in this embodiment, similarly to the second embodiment, in the transmitting / receiving circuit used in the dual mode system in which the radio channel frequency is relatively large between the systems, one RF VCO 1 and one RF VCO 1 are used. It is possible to generate a local signal corresponding to each system with one IF VCO 2. Therefore, it is possible to provide a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit.

(Fourth Embodiment) The fourth embodiment of the present invention is another modification of the second embodiment, and is a modification of the dual mode system in which the radio channel frequencies between the systems are relatively large. In a synthesizer used in a transmitting / receiving circuit, in order to generate an RF local signal frequency corresponding to a system on a low frequency side, a frequency divider 2 is provided on an output path of an RF local signal frequency generated by an RF VCO 1.
3 is provided.

FIG. 5 is a circuit block diagram showing a configuration of a synthesizer according to the fourth embodiment.
The same reference numerals are given to the same parts as those described above, and the detailed description is omitted.

A frequency divider 23 is inserted in the output path of the RF local signal frequency generated by the RF VCO 1.
This frequency divider 23 outputs the RF output from the RF VCO 1
The local signal frequency is divided by 1 / N4, and the divided signal is output as a local signal for RF corresponding to the system on the low frequency side. Note that the signal output from the mixer 10 is used as the RF local signal corresponding to the high-frequency side system.

Therefore, in this embodiment, similarly to the second embodiment, in the transmitting / receiving circuit used in the dual mode system in which the radio channel frequency is relatively large between the systems, one RF VCO 1 and one RF VCO 1 are used. It is possible to generate a local signal corresponding to each system with one IF VCO 2. Therefore, it is possible to provide a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit.

(Fifth Embodiment) A fifth embodiment of the present invention is a modification of the first embodiment, and is a modification of the first embodiment.
By providing the frequency divider 24 at the subsequent stage of the CO2, the common frequency division ratio of the frequency dividing phase shifters 7 and 8 and the frequency divider 9 for setting the frequency shift width is reduced.

FIG. 6 is a circuit block diagram showing the configuration of the synthesizer according to the fifth embodiment.
The same reference numerals are given to the same parts as. VCO2 for IF
A frequency divider 24 is interposed in the output path of. This frequency divider 24 divides the local signal output from the IF VCO 2 by 1 / N5, and
The signals are input to a frequency dividing phase shifter 7 for generating an F local signal and a frequency divider 9 for setting a frequency shift width. Note that PL
The local signal output from the IF VCO 2 is directly input to the L4 and the frequency dividing phase shifter 8 for generating the transmission IF local signal.

With such a configuration, the frequency dividing phase shifter 7
It is possible to generate a desired reception IF local signal and a frequency shift width without forcibly setting the frequency division ratio of the frequency divider 9 to a large value. Even in the case where the wireless channel interval is larger, it can be easily handled.

(Sixth Embodiment) A sixth embodiment of the present invention is directed to a synthesizer used in a transmission / reception circuit of a dual mode system in which a radio channel frequency between systems is relatively large apart from each other. A multiplier is arranged on the output side of a mixer for generating a signal, and the output signal frequency of the mixer is multiplied by the multiplier to generate an RF local signal corresponding to a system on a high frequency side.

FIG. 7 is a circuit block diagram showing a configuration of a synthesizer according to the sixth embodiment.
The same reference numerals are given to the same parts as in FIG.

A multiplier 25 is provided downstream of the mixer 10. The frequency multiplier 25 multiplies the signal frequency output from the mixer 10 by N4 times, so that the RF VCO 1
The RF local signal frequency corresponding to the system on the high frequency side, which is higher than the RF local signal frequency corresponding to the system on the low frequency side, which is output from.

With such a configuration, even when applied to a transmission / reception circuit used in a dual mode system in which the radio channel frequency is relatively large between the systems, one RF VCO1 and one IF It is possible to generate a local signal corresponding to each system with the VCO 2. Therefore, as in the first embodiment, a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit can be provided.

(Seventh Embodiment) A seventh embodiment of the present invention is a modification of the sixth embodiment, and is a transmission / reception circuit of a dual mode system in which the radio channel frequencies between the systems are relatively large. In the synthesizer used, a multiplier is provided on a path of the RF local signal frequency from the RF VCO 1 to the mixer 10 in order to generate an RF local signal frequency corresponding to a high-frequency system.

FIG. 8 is a circuit block diagram showing a configuration of a synthesizer according to the seventh embodiment.
The same reference numerals are given to the same parts as those described above, and the detailed description is omitted.

Between the VCO 1 for RF and the mixer 10,
A multiplier 26 is interposed. The frequency divider 25 multiplies the RF local signal frequency generated by the RF VCO 1 by N4 times and supplies the frequency to the mixer 10. The mixer 10 mixes the RF local signal multiplied by the multiplier 26 with a frequency-divided signal output from the frequency shift width setting frequency divider 9 to support a high-frequency system. Generate a local signal for RF.

Therefore, in this embodiment, similarly to the sixth embodiment, in a transmitting / receiving circuit used in a dual mode system in which the radio channel frequency is relatively large between the systems, one RF VCO1 and one RF VCO1 are used. It is possible to generate a local signal corresponding to each system with one IF VCO 2. Therefore, it is possible to provide a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit.

(Eighth Embodiment) An eighth embodiment of the present invention is another modification of the sixth embodiment, and is a dual mode system in which the radio channel frequencies between the systems are relatively large. In a synthesizer used in a transmitting / receiving circuit, in order to generate a higher RF local signal frequency corresponding to a system on a higher frequency side, an RF V
A multiplier 27 is provided on the output path of the RF local signal frequency generated by CO1.

FIG. 9 is a circuit block diagram showing the configuration of a synthesizer according to the eighth embodiment.
The same reference numerals are given to the same parts as those described above, and the detailed description is omitted.

A multiplier 27 is provided on the output path of the RF local signal frequency generated by the RF VCO 1. The multiplier 27 multiplies the RF local signal frequency output from the RF VCO 1 by N4 times, and outputs the multiplied signal as an RF local signal corresponding to a system on the high frequency side. In addition, R corresponding to the low frequency side system
The signal output from the mixer 10 is used as it is as the F local signal.

Therefore, in this embodiment, similarly to the second embodiment, in the transmitting / receiving circuit used in the dual mode system in which the radio channel frequency is relatively large between the systems, one RF VCO 1 and one RF VCO 1 are used. It is possible to generate a local signal corresponding to each system with one IF VCO 2. Therefore, it is possible to provide a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit.

(Ninth Embodiment) In a ninth embodiment of the present invention, a selection circuit is provided after a mixer that generates an RF local signal corresponding to one of the systems, and the selection circuit outputs a signal from the mixer. By selecting and outputting a frequency, selection and demultiplexing are performed for each system, or selection and demultiplexing between transmission and reception are performed.

FIG. 10 is a circuit block diagram showing the configuration of a synthesizer according to the ninth embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted.

A selection circuit 28 is provided on the output side of the mixer 10. The selection circuit 28 includes, for example, a plurality of filters for selecting a frequency, and selectively operates these filters by a control signal (not shown) to output an RF local signal of a required frequency.

For example, by selectively operating a high-pass filter, an up-converted signal is selectively output, and by selectively operating a low-pass filter, a down-converted signal is selectively output. In addition, both a high-pass filter and a low-pass filter are provided, and a high-pass filter is selectively operated to selectively output an RF local signal corresponding to one system or selectively output a received RF local signal. On the other hand, when the low-pass filter is selectively operated, an RF local signal corresponding to the other system is selected and output, or a transmission RF local signal is selected and output.

With such a configuration, the filter in the selection circuit 28 is selectively operated to provide one RF VC.
An RF local signal corresponding to each system can be arbitrarily generated only by using O1 and one IF VCO2. Therefore, it is possible to provide a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit.

(Tenth Embodiment) In a tenth embodiment of the present invention, a selection circuit is provided downstream of a mixer that generates an RF local signal corresponding to one system, and the selection circuit outputs a signal from the mixer. A required frequency is selected and output from a plurality of frequencies.

FIG. 11 is a circuit block diagram showing the structure of a synthesizer according to the tenth embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals. Mixer 10
Is provided with a selection circuit 29 on the output side of. The selection circuit 29 includes, for example, a plurality of filters for selecting a frequency, and selectively operates these filters by a control signal (not shown) to output RF local signals of a plurality of required frequencies.

Even with such a configuration, it is possible to arbitrarily generate an RF local signal corresponding to each system only by using one RF VCO 1 and one IF VCO 2. Therefore, it is possible to provide a synthesizer that is smaller, lighter, less expensive, and consumes less power than a conventional synthesizer circuit.

(Eleventh Embodiment) In an eleventh embodiment of the present invention, the synthesizer described in the first embodiment is provided in a transmission / reception circuit of a W-CDMA and DCS-1800 dual mode portable terminal. Things.

FIG. 12 is a circuit block diagram showing the configuration of the transmission / reception circuit according to the eleventh embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals.

In the synthesizer SYN1, the RF V
RF local signal for W-CDMA generated by CO1, and DC generated by distributor 9 and mixer 10
The RF local signal for S-1800 is distributed to reception and transmission by distributors 31 and 32, respectively, and then input to selection circuits 102 and 112.
2 and 112, which are respectively selected and used for the reception system RF down-conversion mixer 101 and the transmission system RF
It is supplied to the up-conversion mixer 111. That is, the W-CDMA radio channel frequency pair and DCS-1
Since the 800 wireless channel frequency band is close to each other, the RF down-conversion mixer 101 of the reception system and the RF up-conversion mixer 111 of the transmission system are shared by both systems.

On the other hand, in the synthesizer SYN1, the IF local signal of the receiving system and the IF local signal of the transmitting system generated by the frequency dividing phase shifters 7 and 8 are mixed with the quadrature demodulator mixers 109a and 109b and the quadrature modulator mixer 119a, respectively. , 119b. That is, the W-CDM is also used for the quadrature demodulator mixers 109a and 109b and the quadrature modulator mixers 119a and 119b.
Shared by both A and DCS-1800 systems.

With such a configuration, first, in the receiving system, a received RF signal received by an antenna (not shown) and amplified with low noise is supplied from the synthesizer SYN1 to the RF down-converting mixer 101.
The signal is mixed with the F local signal and down-converted into a received IF signal. Then, the received IF signal is received by the divider 103 into receiving intermediate frequency filters 104 and 105.
After the unnecessary intermediate frequency components are removed by the reception intermediate frequency filters 104 and 105, the signals are input to the selection circuit 106.

When the W-CDMA system is selected, the selection circuit 106 selects the reception IF signal that has passed through the reception intermediate frequency filter 104 for W-CDMA, and
The signal is input to the GC circuit 107, and when the DCS-1800 system is selected, the reception IF signal that has passed through the reception intermediate frequency filter 105 for the DCS-1800 is selected and input to the AGC amplifier 107.

The AGC amplifier 107 amplifies the received IF signal so that the amplitude becomes constant, and the received IF signal output from the AGC circuit 107 is distributed by the distributor 108 to be used as a quadrature demodulator mixer 109a, 109b
Is input to Quadrature demodulator mixers 109a, 109b
Then, the received IF signal is mixed with the received IF local signal supplied from the synthesizer SYN1 to perform quadrature demodulation, and the demodulated received baseband signal is input to a received signal processing unit (not shown).

That is, in the receiving system, the AGC amplifier 107 together with the RF down-conversion mixer 101 and the quadrature demodulator mixers 109a and 109b described above.
Is shared between W-CDMA and DCS-1800.

On the other hand, in the transmission system, the transmission signal output from the transmission signal processing section (not shown) is first mixed in the quadrature modulator mixers 119a and 119b with the transmission IF local signal supplied from the synthesizer SYN1 to perform quadrature modulation. Is done. Then, the orthogonally modulated transmission IF signal is synthesized by the synthesizer 118, and then amplified by the transmission IF amplifier 117.
Through the transmission intermediate frequency filters 114 and 115, respectively.

When W-CDMA is selected, the transmission I that has passed through the transmission intermediate frequency filter 114
The F signal is selected by the selection circuit 113 and input to the RF up-conversion mixer 111. And this R
In the F up-conversion mixer 111, the transmission RF local signal for W-CDMA supplied from the synthesizer SYN1 is mixed and up-converted into a transmission RF signal for W-CDMA, and then amplified by a transmission power amplifier (not shown). After that, it is transmitted from the antenna.

On the other hand, when DCS-1800 is selected, the transmission IF signal that has passed through transmission intermediate frequency filter 115 is selected by selection circuit 113 and input to RF up-conversion mixer 111. And
In the RF up-conversion mixer 111, the DCS-180 supplied from the synthesizer SYN1 is used.
0 and mixed with the transmit RF local signal for DCS
The signal is up-converted to a transmission RF signal corresponding to -1800, and then amplified by a transmission power amplifier (not shown) and transmitted from an antenna.

That is, in the transmission system, the intermediate frequency amplifier 117, together with the quadrature modulator mixers 119a and 119b and the RF up-conversion mixer 111, are connected to the W
-Shared between CDMA and DCS-1800.

As described above, in the eleventh embodiment,
As described in the first embodiment, the synthesizer SYN
1, it is not necessary to provide a VCO for each of the W-CDMA and DCS-1800 systems, and one RF VCO 1 and one IF VC
A synthesizer can be constituted by O2. In addition, in both the receiving system and the transmitting system, as described above, the mixer 101 for RF down-conversion and the mixer 111 for RF up-conversion,
The quadrature demodulator mixers 109a and 109b and quadrature modulator mixers 119a and 119b, and the AGC amplifier 107 and the transmission intermediate frequency amplifier 117 are provided by W-CDMA and DCS-
1800.

For this reason, W-CDMA and DCS-18
The transmission / reception circuit can be configured without providing a synthesizer and two sets of reception and transmission circuits, respectively, corresponding to 00, thereby enabling transmission / reception for a small-sized, light-weight, low-power and low-cost dual-mode portable terminal. Circuit can be provided.

(Twelfth Embodiment) In a twelfth embodiment of the present invention, the synthesizer described in the second embodiment is different from the W-CDMA and the GSM in which the communication channel band between the systems is relatively far apart. Of the dual mode portable terminal.

FIG. 13 is a circuit block diagram showing a configuration of the transmission / reception circuit according to the twelfth embodiment. In addition,
In this figure, the same parts as those in FIGS. 3 and 12 are denoted by the same reference numerals, and detailed description is omitted.

The transmitting / receiving circuit of this embodiment is provided with the synthesizer SYN2 shown in FIG. 3 described in the second embodiment as a synthesizer. That is, the frequency divider 9
A GSM-compatible RF local signal obtained by further dividing the local signal frequency generated by the mixer 10 to 1 / N4 by the frequency divider 21 is distributed to the receiving system and the transmitting system by the distributor 32, and transmitted through the selection circuit 102. To the receiving RF down-converting mixer 101 and the transmitting RF up-converting mixer 111.

Now, suppose that the frequency configuration is the same as that of the dual mode of W-CDMA and GSM described in the second embodiment, that is, reception IF = 190 MHz transmission IF = 380 MHz W-CDMA reception RF local signal frequency = 2300 to 2300
2360 MHz W-CDMA transmission RF local signal frequency = 2300-
2360 MHz GSM reception RF local signal frequency = 1115 to 115
0 MHz GSM reception RF local signal frequency = 1260 to 129
5 MHz, frequency division ratio of frequency divider 21 = frequency division ratio of frequency divider 9 (at reception) = frequency division ratio of frequency divider 9 (at transmission) = frequency division of frequency dividing phase shifter 7 Ratio = 4 The frequency division ratio of the frequency divider / phase shifter 8 = 2.

Then, the VC for RF in the GSM mode
The oscillation frequency of O1 is: at reception = (2230 to 2300) + 760/8 = 232
When transmitting from 5 to 2360 MHz = (2520-2590)-760/4 = 233
0 to 2400 MHz.

The oscillation frequency range of the RF VCO 1 in the W-CDMA mode is 2300 to 2360 MHz.
The oscillation frequency range for both modes of the VCO 1 for F is 2
It becomes 300 to 2400 MHz. VCO for RF at this time
The frequency variable width of 1 is 100 MHz (about 4.3%),
It is a sufficiently feasible width.

As described above, even in the transmission / reception circuit corresponding to the dual mode / dual band in which the radio channel frequency is largely separated, one RF VCO 1 and one IF VCO 1 are used.
It is possible to generate a local signal corresponding to each system with CO2, and as in the embodiment of FIG. Can be provided.

(Thirteenth Embodiment) According to a thirteenth embodiment of the present invention, two reception mixers for RF down-conversion and two transmission mixers for RF up-conversion are provided in association with the system. For example, GSM and D
As in the case of the dual mode of the CS-1800, the wireless channel frequency bands between the systems are far apart and the mobile terminal for a dual-band system having the same channel bandwidth can be supported.

FIG. 14 is a circuit block diagram showing the configuration of the transmission / reception circuit according to the thirteenth embodiment. In addition,
In this figure, the same parts as those in FIGS.

The transmitting / receiving circuit of this embodiment is provided with the synthesizer SYN3 shown in FIG. 11 described in the tenth embodiment as a synthesizer. Also, the receiving system has two reception Rs corresponding to DCS-1800 and GSM.
F down-conversion mixers 201 and 202 are provided, and two transmission RF up-conversion mixers 211 and 212 corresponding to DCS-1800 and GSM are provided in the transmission system.
Is provided. Further, the intermediate frequency filters 206 and 21
6 has only one receiving system and one transmitting system, and the single intermediate frequency filters 206 and 216 are connected to the DCS-1.
Shared by both 800 and GSM systems.

With such a configuration, the local signal generated by the mixer 10 of the synthesizer SYN3 is divided by the selection circuit 29 into two local signals having different frequency bands. Is distributed to the receiving system and the transmitting system by
The received RF down-convert mixer 201 and the transmit RF up-convert mixer 212 are supplied as RF local signals corresponding to S-1800. On the other hand, the other of the two local signals output from the selection circuit 29 is divided by the frequency divider 21 into 1 / N4, and then divided by the divider 203 to the reception system and the transmission system. As a GSM-compatible RF local signal,
The signals are supplied to the down-converting mixer 202 and the transmission RF up-converting mixer 211, respectively.

Therefore, when DCS-1800 is selected, the received RF signal is down-converted to an IF signal by mixer 201, and the transmitted IF signal is up-converted to a transmitted RF signal by mixer 212 and transmitted. On the other hand, when GSM is selected, the reception RF
The signal is down-converted to an IF signal by mixer 202, and the transmission IF signal is up-converted to a transmission RF signal by mixer 211 and transmitted. That is, DCS-1
For 800 and GSM, frequency conversion is performed using separate mixers.

Now, suppose that the frequency of the IF system is set to be the same as that of FIG. 1 and the means for generating an RF local signal corresponding to DCS-1800 has the same configuration as that of FIG. Also, R for GSM
Setting the F-local signal above the radio channel frequency;
The frequency division ratio N4 of the frequency divider 21 is set to 2. Also, the frequency division ratio N3 of the frequency divider 9 is set to 8 at the time of reception and 2 at the time of transmission, and the mixer 10 performs down conversion (difference frequency component) for both transmission and reception. Then,
The oscillation frequency of the RF VCO 1 at this time is (GSM) reception time = (RxRF + 190) × 2−760 / 8 = 21
At the time of transmission from 35 to 2205 MHz = (TxRF + 380) × 2-760 / 2 = 21
40 to 2210 MHz.

At this time, since the oscillation frequency range of the RF VCO 1 corresponding to DCS-1800 is 2185 to 2260 MHz, the oscillation frequency range of the RF VCO 1 in both systems is 2135 to 2260 MHz. At this time, the variable width of the RF VCO 1 becomes 125 MHz (about 5.7%),
This is within a sufficiently feasible range.

As described above, the RF VCOs 1 and I
GSM and DCS- without increasing the number of F VCO2
It is possible to support a 1800 dual-band system, and as a result, it is possible to provide a transmission / reception circuit applicable to a small-sized, lightweight, low-power-consumption, and low-cost dual-band portable terminal without increasing large-sized components.

(Fourteenth Embodiment) A fourteenth embodiment of the present invention relates to a transmission / reception circuit having a transmission system in a loop configuration.
This shows a case where the synthesizer described in the eleventh embodiment of the present invention is applied.

FIG. 15 is a circuit block diagram showing a configuration of a transmission / reception circuit according to the fourteenth embodiment. In this figure, the same parts as those in FIGS. 10 and 14 are denoted by the same reference numerals, and detailed description is omitted.

The transmitting system is provided with two VCOs 304 and 305, and the oscillation outputs of these VCOs 304 and 305 are selected by the distributor 306 and input to the mixer 302. In the mixer 302, the VCOs 304, 305
Is mixed with the transmission RF local signal output from the synthesizer SYN3, and the mixed output is fed back to the phase comparator 310 via the band-pass filter.

On the other hand, the phase comparator 310 has the transmission I output from the quadrature modulation mixers 119a and 119b.
The composite signal of the F signal is input, and the phase comparator 310 outputs a phase difference signal between the transmission IF signal and the feedback signal. Then, a control signal is generated in the charge pump circuit 309 based on the phase difference signal, and the control signal is smoothed by the loop filter 308 and then distributed.
7 are input to the VCOs 304 and 305, respectively.

As described above, the synthesizer of the present invention can be applied to a transmission system having a loop configuration, thereby providing a low-cost transmission / reception circuit that is small, lightweight, consumes little power.

[0114] The transmission system configured by a loop includes a modulation loop, a modulation loop, a transmission loop, and a system called an offset PLL or a translation loop. The synthesizer of the present invention is applicable and can achieve the same effect.

(Other Embodiments) The present invention is not limited to each of the above embodiments, and a transmission / reception circuit can be formed by selectively combining the circuits described in each embodiment. In this case, the same effect can be obtained.

In addition, the type of each system constituting the multi-mode / multi-band system and its use frequency band, the type and configuration of the mobile communication terminal used in this system, the specific circuit configuration of the synthesizer and the transmission / reception circuit, etc. Various modifications can be made without departing from the scope of the present invention.

[0117]

As described in detail above, according to the present invention, the PL
In addition to the first local oscillator for radio frequency and the local oscillator for intermediate frequency using the L unit, a frequency shift width generating unit using a frequency divider, and the second local oscillator for radio frequency using a mixer Are provided. In the frequency shift width generating means, the PLL of the intermediate frequency local oscillation means is used.
The signal generated by the means is frequency-divided by a predetermined frequency division number to generate a signal representing a frequency shift width, and the first radio frequency local oscillation generated by the first radio frequency local oscillation means is generated. A second radio frequency local oscillation signal is generated by mixing the signal with the signal generated by the shift width generating means.

Therefore, according to the present invention, in a mobile communication terminal commonly used for a plurality of systems including a communication system that performs transmission and reception simultaneously, the number of high-frequency VCOs and intermediate-frequency VCOs is reduced to reduce the circuit size. It is possible to provide a synthesizer capable of securing isolation between transmission and reception while reducing the cost, power consumption, and cost, and a transmission / reception circuit including the synthesizer.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of a synthesizer according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a PLL circuit of the synthesizer shown in FIG.

FIG. 3 is a circuit block diagram showing a second embodiment of the synthesizer according to the present invention.

FIG. 4 is a circuit block diagram showing a third embodiment of the synthesizer according to the present invention.

FIG. 5 is a circuit block diagram showing a fourth embodiment of the synthesizer according to the present invention.

FIG. 6 is a circuit block diagram showing a fifth embodiment of the synthesizer according to the present invention.

FIG. 7 is a circuit block diagram showing a sixth embodiment of the synthesizer according to the present invention.

FIG. 8 is a circuit block diagram showing a seventh embodiment of the synthesizer according to the present invention.

FIG. 9 is a circuit block diagram showing an eighth embodiment of the synthesizer according to the present invention.

FIG. 10 is a circuit block diagram showing a ninth embodiment of a synthesizer according to the present invention.

FIG. 11 is a circuit block diagram showing a tenth embodiment of a synthesizer according to the present invention.

FIG. 12 is a circuit block diagram showing a configuration of a transmission / reception circuit according to an eleventh embodiment of the present invention.

FIG. 13 is a circuit block diagram showing a configuration of a transmission / reception circuit according to a twelfth embodiment of the present invention.

FIG. 14 is a circuit block diagram showing a configuration of a transmission / reception circuit according to a thirteenth embodiment of the present invention.

FIG. 15 is a circuit block diagram showing a configuration of a transmission / reception circuit according to a fourteenth embodiment of the present invention.

[Explanation of symbols]

 SYN1 to SYN3 synthesizer 1 first VCO (VCO for RF) 2 second VCO (VCO for IF) 3 reference oscillator 4 PLL circuit 5, 6 loop filter 7, 8 frequency dividing phase shifter 9: frequency divider for frequency shift width setting 10: mixer for frequency shift 21, 22, 23, 24 ... frequency divider 25, 26, 27 ... frequency divider 28, 29 ... selection circuit

Claims (10)

[Claims] 1. A first communication system in which different communication bands are allocated and these communication bands are not in integral multiples with each other.
And a synthesizer for generating first and second radio frequency local oscillation signals and intermediate frequency local oscillation signals respectively corresponding to the first and second radio frequency communication systems using PLL means. First radio frequency local oscillation means for generating a local oscillation signal; intermediate frequency local oscillation means for generating the first and second intermediate frequency local oscillation signals using PLL means; The signal generated by the PLL means is frequency-divided by a frequency division number set based on the frequency difference of the communication band between the first and second systems to generate a signal representing a frequency shift width. Mixing a shift width generating means, a first RF local oscillation signal generated by the first RF local oscillation means, and a signal generated by the shift width generating means; A second radio frequency local oscillation means for generating the second radio frequency local oscillation signal. 2. The second radio frequency local oscillation means includes means for mixing the first radio frequency local oscillation signal and a signal generated by the shift width generation means, and a signal generated by the mixing. A first method for dividing a signal by a predetermined frequency to generate a second radio frequency local oscillation signal
2. The synthesizer according to claim 1, further comprising a frequency dividing means. 3. The second radio frequency local oscillation means includes: a second frequency division means for dividing the first radio frequency local oscillation signal; and a signal obtained by the second frequency division means. And means for mixing the signal generated by the shift width generating means and the signal generated by the mixing, and outputting the signal generated by the mixing as a second radio frequency local oscillation signal. Synthesizer. 4. The first radio frequency local oscillation means: PLL means, frequency division of an oscillation signal of the PLL means, and outputs the frequency-divided signal as a first radio frequency local oscillation signal. The synthesizer according to claim 1, further comprising third frequency dividing means. 5. The second radio frequency local oscillation means, means for mixing the first radio frequency local oscillation signal and a signal generated by the shift width generation means, and a signal generated by the mixing. A first step of multiplying the signal by a predetermined multiple to generate a second radio frequency local oscillation signal;
2. The synthesizer according to claim 1, further comprising a multiplying means. 6. The second radio frequency local oscillation means, a second multiplication means for multiplying the first radio frequency local oscillation signal, a signal obtained by the second multiplication means and the shift 2. The synthesizer according to claim 1, further comprising: means for mixing the signal generated by the width generating means and outputting the signal generated by the mixing as a second radio frequency local oscillation signal. 7. The first radio frequency local oscillation means includes: PLL means; a third radio frequency local oscillation signal for multiplying an oscillation signal of the PLL means; and outputting the multiplied signal as a first radio frequency local oscillation signal. 2. The synthesizer according to claim 1, further comprising a multiplying means. 8. The second radio frequency local oscillation means, means for mixing the first radio frequency local oscillation signal and the signal generated by the shift width generation means, and a signal generated by the mixing. And first selecting means for selecting a signal having a desired frequency from the signals and outputting the selected signal as a second radio frequency local oscillation signal. The synthesizer as described. 9. The shift width generating means, when dividing the signal generated by the PLL circuit of the intermediate frequency local oscillation means, sets the frequency division number in accordance with the communication band of the first and second communication systems. The synthesizer according to any one of claims 1 to 8, further comprising means for changing the frequency of the synthesizer. 10. A transmitting and receiving circuit for transmitting and receiving radio frequency signals respectively corresponding to first and second communication systems to which different communication bands are allocated and these communication bands are not an integral multiple of each other. And the second communication system, respectively,
A synthesizer for generating first and second radio frequency local oscillation signals and an intermediate frequency local oscillation signal; and a first and second radio frequency local oscillation signal generated by the synthesizer. A receiving system for mixing and frequency converting the received intermediate frequency signal into a received intermediate frequency signal, mixing the received intermediate frequency signal with the first and second intermediate frequency local oscillation signals, and converting the frequency into a received baseband signal; The band signal is mixed with the first and second intermediate frequency local oscillation signals and frequency-converted into a transmission intermediate frequency signal. The transmission intermediate frequency signal is further combined with the first and second radio frequency local oscillation signals. A transmission system for mixing and frequency-converting the signal into a transmission radio frequency signal and transmitting the signal; and wherein the synthesizer uses PLL means to perform the first A first radio frequency local oscillation means for generating a radio frequency local oscillation signal, and an intermediate frequency local oscillation means for generating the first and second intermediate frequency local oscillation signals using PLL means. A signal generated by the PLL means of the intermediate frequency local oscillation means is frequency-divided by a frequency division number set based on a frequency difference of a communication band between the first and second systems to represent a frequency shift width. A shift width generating means for generating a signal; mixing the first RF local oscillation signal generated by the first RF local oscillation means with a signal generated by the shift width generating means. And a second radio frequency local oscillation means for generating the second radio frequency local oscillation signal.