JP3261324B2 - Wireless communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication device, and more particularly, to a radio portable telephone capable of transmitting and receiving a plurality of bands.

[0002]

2. Description of the Related Art FIG. 4 is a circuit block diagram of a radio section of a super heterodyne type radio portable telephone capable of transmitting and receiving two different frequency bands based on Japanese Patent Application Laid-Open No. 60-235510. As shown in FIG. 4, the circuit block of the radio unit includes an antenna 31, a transmission / reception switching circuit 32, and an RF, which are shared by the first frequency band and the first frequency band.
A SAW filter 33, a mixer 34 for down-converting a received RF frequency signal to an intermediate frequency signal, a SAW filter 35 for an intermediate frequency signal in a first band, a SAW filter 36 for an intermediate frequency signal in a second frequency band, transmission and reception A switch 37 for switching the SAW filter in accordance with the frequency band, a mixer 38 for down-converting the intermediate frequency signal to a baseband frequency signal, a second local synthesizer 41, a local synthesizer 45 for both transmission and reception,
It comprises a reference oscillator 46.

[0003] First, the reception will be described. When the first frequency band and the second frequency band are used, the RF reception frequency signal received by the antenna is 810 to 818M.
Hz or 870-885 MHz. At this time, the transmit / receive local synthesizer 45 oscillates and outputs a frequency of 940 to 948 MHz when the first frequency band is used and 925 to 940 MHz when the second frequency band is used. Therefore, the first mixer 34 receives the output of the transmit / receive local synthesizer 45 as it is as the first local frequency signal, and outputs 1 when using the first frequency band.
30 MHz, 55 MHz when using the second frequency band
A first intermediate frequency signal is generated. The generated first intermediate frequency signal passes through SAW filters 35 and 36 corresponding to the respective intermediate frequencies selected by the switch 37, and then passes through the second intermediate frequency signal.
Input to the mixer 38.

Here, the second mixer 38 mixes the second local synthesizer signal and the first intermediate frequency signal of 129.55 MHz when using the first frequency band and 55.45 MHz when using the second frequency band to 450 kHz.
The z second intermediate frequency signal is input to the demodulator and demodulated.

[0005] Next, transmission will be described. In the wireless communication apparatus having the above configuration, 925 to 948 output from the transmit / receive synthesizer 45 according to the specified frequency band.
The frequency signal of MHz is directly input to the transmission system circuit 42, directly modulated, and transmitted from the antenna 31 via the transmission / reception switching circuit 32.

[0006] In this way, a radio section of a wireless portable telephone capable of transmitting and receiving in both the first portable telephone frequency band and the second portable telephone frequency band can be constructed.

[0007]

However, in the above-mentioned prior art configuration, the pass frequency band of the SAW filter 33 is 810 to 885 MHz, and when the first local signal when the second frequency band is used is about 925 MHz. , The first local signal exists 40 MHz higher than the pass frequency band. FIG. 5 shows the SAW filter 3
3 shows a relationship diagram between the characteristic example of FIG. 3 and the first local signal. In a normal SAW filter, it is difficult to obtain a sufficient amount of attenuation at a frequency near about 40 MHz away from the pass frequency band. The first local signal leaks to the antenna side, and there is a problem that the first local leak signal radiated from the antenna adversely affects other mobile phones used at the same time as an interference wave.

[0008] Further, since the SAW filter cannot be formed into a chip when the IC is activated, when the radio section is formed into one chip and the size is reduced, parts other than the SAW filter are reduced to one chip.
Make a tip. At this time, as shown in FIG. 4, even if the portion surrounded by the dotted line is one chip, it is not suitable for miniaturization because there are four SAW filters in the receiving system. In particular, the SAW filter 3 for the intermediate frequency signal in the second frequency band of 55 MHz
6 is large because of its low frequency, and is not suitable for further miniaturization.

In addition, since the current consumption of each part is large, there are also problems that it is difficult to use the wireless portable telephone for a long time and the standby time is short.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to perform good communication without signal leakage or the like at the time of communication, and to reduce the size of the wireless communication with low power consumption. It is intended to provide a device.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, the transmission frequency is set to
940-948 MHz, and the reception frequency is 810-8
The first and the frequency band range is 18MHz, the transmission frequency 9
25 to 940 MHz, and the reception frequency is 870 to 88
The radio communication apparatus superheterodyne which can be used in the second 2-band frequency band ranges is 5 MHz, the oscillation frequency band of both transmission and reception local oscillator 925-9
And 48 MHz, as a reception local signal, the at the time of the first frequency band used the transmission and reception shared local oscillator output, using a signal obtained by frequency converting the both transmission and reception local oscillator output to 1000~1015MHz during a second frequency band used It is characterized by.

That is, transmission and reception are performed only when the second frequency band is used.
And Shin shared local synthesizer output frequency 75MH
By frequency mixing the sine wave signal of z with
A first local signal for reception of 0 to 1023 MHz is obtained.

With this configuration, the first local signal received at the time of transmission / reception of the second frequency band is set to 1000 to 1015.
By up-converting to MHz, the reception intermediate frequency becomes 130 MHz in both the first and second frequency bands, so that the intermediate frequency SAW filter is shared and suitable for miniaturization.

[0014] Further, according to this structure, when the second frequency band reception, the transmission and reception shared local synthesizer output by up-converting only 75 MHz, the reception first local signal, a large insertion loss of RF · SAW filter it is possible to frequency conversion to frequency band range, it is possible to prevent the first local signal leaks to the antenna side.

According to a second aspect of the present invention, an oscillation frequency F of a reference oscillator in the wireless communication apparatus according to the first aspect is provided.
ref is set to Fref = 75 / N (MHz, where N is an integer), and when the second frequency band is used, the output of the reference oscillator is multiplied to 75 MHz using an N-multiplier.
The output of the local oscillator is also upconverted by a frequency converter using a multiplied signal of 75 MHz to obtain a received local signal.

With this configuration, the frequency of the reference signal source in the portable telephone is set to (75 / N) MHz (N is an integer), and the output of the reference signal source is multiplied by an N multiplier. Can be obtained by multiplying N by N.
By adding a new oscillator such as a multiplier, problems such as an increase in the circuit scale and an increase in cost can be solved, and this is suitable for further miniaturization.

According to a third aspect of the present invention, in the wireless communication apparatus according to the second aspect, the power of the N-multiplier is turned off when the first frequency band is used. That is, by turning off the power of the N-multiplier when the first frequency band is used, the power consumption of the wireless communication device is reduced. In particular, in the case where the method of using the second frequency band is used only when all communication channels of the first frequency band are used, the probability that the multiplier is turned on in the above configuration decreases, The average current consumption can be reduced as compared with the conventional case.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram illustrating a configuration of a wireless unit of the wireless communication device according to the first embodiment of the present invention. As shown in the figure, the wireless communication apparatus down-converts an antenna 1, a transmission / reception switching circuit 2, an RF / SAW filter 3, and a reception RF frequency signal to a reception intermediate frequency signal, which are shared by a first frequency band and a second frequency band. Mixer 4, SAW filter 5, mixer 6 for down-converting the received intermediate frequency signal to a baseband frequency signal, second mixer
A local synthesizer 10, a mixer 11, a switch 12, which is turned off when the first frequency band is used, and a switch 12, which is turned on when the second frequency band is used, a 75MHz synthesizer 20, and a transmission / reception-use local which can switch the frequency according to the frequency band to be used. It comprises a synthesizer 18 and a VCXO (reference signal source) 19.

First, the reception state of the first frequency band signal will be described. In the wireless communication apparatus having the above configuration, the signal (810 to 810) of the first frequency band received by the antenna 1
818 MHz) is input to the mixer 4 via the transmission / reception switching circuit 2. The mixer 4 receives the first local frequency signal of 940 to 948 MHz output from the local synthesizer 18 for both transmission and reception, and
Is down-converted to an intermediate frequency signal. At this time, the switch 12 is off, and the mixer 11 has only the input of the local synthesizer 18 for both transmission and reception. Therefore, the input of the mixer 11 is output as it is. The downconverted 130 MHz intermediate frequency signal is input to mixer 6. At the same time, the mixer 6 outputs 129.55 MHz output from the second local synthesizer 10.
and a second local frequency signal of 450 kHz
After being down-converted into a baseband frequency signal of

At the time of transmission, the transmission / reception local synthesizer oscillates at the transmission frequency itself. In the transmission system 15, the output of the local synthesizer is directly modulated, amplified, and transmitted from the antenna 1.

Next, the signal receiving state of the second frequency band will be described. In the wireless communication apparatus having the above configuration, the signal (870) in the second frequency band received by the antenna 1
To 885 MHz) is input to the mixer 4 via the transmission / reception switching circuit 2. At the same time, a signal (frequency: 925) output from the transmit / receive local synthesizer 18 is supplied to the mixer 4.
940 MHz) and a 75 MHz sine wave signal output from the 75 MHz synthesizer 20 are up-converted by the mixer 11, a first local frequency signal of 1000 to 1015 MHz is input, and down-converted to an intermediate frequency signal of 130 MHz. The downconverted 130 MHz intermediate frequency signal is input to mixer 6. At the same time, the mixer 6 has the second local synthesizer 1
The second local frequency signal of 129.55 MHz output from 0 is input, down-converted to a 450 kHz baseband frequency signal, and then input to a demodulation circuit.

Therefore, at the time of reception, the mixer 4
The first local signal of 1015 MHz is input. This is because the first local signal frequency is used in a frequency band where the insertion loss of the RF / SAW filter 3 is large as shown in FIG. No signal leaks to the antenna side. Also, since the intermediate frequency can be made the same when receiving the signal in the first frequency band and the signal in the second frequency band, the SAW filter for the intermediate frequency can be shared, and the size can be reduced.

When transmitting the second frequency band,
The transmission / reception local oscillator oscillates at the transmission frequency itself, as in the first frequency band transmission.
, And directly transmits from the antenna 1.

FIG. 3 shows an embodiment according to the second aspect of the present invention (when N = 5). As shown in FIG. 3, VC which is the reference signal source of all the synthesizers
The oscillation frequency of XO19 is 15 MHz (= 75 (MHz)
/ 5), and the quintuple signal is multiplied by 5 by the quintuplexer 14, and the output of the local oscillator for both transmission and reception is output to the mixer 11 by the quintuple signal.
Is up-converted by only 75 MHz. Therefore, in the present embodiment, the 75 MHz synthesizer 2 in FIG.
Since a multiplied wave of the VCXO 19, which is a reference signal source, is used instead of 0, it is possible to further reduce the size without adding a new 75 MHz oscillator.

The ON-OFF control signal 21 shown in FIG.
Is supplied to the switch 12 and the quintuple multiplier 14 so that the switch 12 and the quintuple multiplier 14 are used when the first frequency band is used.
Are both OFF, and when the second frequency band is used, both the switch 12 and the quintuple multiplier 14 are turned ON, so that the power consumption when the first frequency band is used can be reduced.

[0026]

Effect of the Invention] As described above, according to the configuration according to one of claims of the present invention, by up-converting a transmission and reception shared first local signal in signal reception of the second frequency band,
By using the first local signal in a frequency band where the insertion loss of the RF / SAW filter is large, it is possible to prevent the first local signal from leaking to the antenna side.

Also, by making the intermediate frequency of the signal of the first frequency band and the signal of the second frequency band the same, the SAW
By reducing the number of filters and the number of synthesizers, a circuit configuration suitable for miniaturization and cost reduction by using an IC is obtained.

Further, according to the configuration of the second aspect of the present invention, since a multiplied wave of the reference signal source in the portable telephone is used, it is not necessary to add a new synthesizer, and further downsizing is achieved.・ Low cost is possible.

Further, when the first frequency band is used, turning off the N-multiplier enables low power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram of a wireless unit of a wireless mobile phone according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a pass characteristic and a first local frequency of an RF / SAW filter for reception according to an embodiment of the present invention.

FIG. 3 is a block diagram of a wireless unit of the wireless mobile phone according to the second embodiment of the present invention.

FIG. 4 is a block diagram of a wireless unit of a conventional wireless mobile phone.

FIG. 5 is a diagram illustrating a relationship between a pass characteristic of a conventional reception RF / SAW filter and a first local frequency.

[Explanation of symbols]

 Reference Signs List 1 antenna 2 transmission / reception switching circuit 3 RF / SAW filter 4 mixer 5 SAW filter 6 mixer 7 baseband filter 8 demodulation system circuit 9 bandpass filter 10 second local synthesizer 11 mixer 12 switch 13 bandpass filter 14 5 multiplier 15 transmission System circuit 16 Band pass filter 17 Amplifier 18 Local synthesizer for both transmission and reception 19 VCXO 20 75 MHz synthesizer 21 ON-OFF control signal 31 Antenna 32 Transmission / reception switching circuit 33 RF / SAW filter 34 Mixer 35 SAW filter 36 SAW filter 37 Switch 38 Mixer 39 Base band Filter 40 Demodulation system circuit 41 Second local synthesizer 42 Transmission system circuit 43 Bandpass filter 44 Amplifier 45 Transmitter / receiver local Synthesizer 46 VCXO

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-107676 (JP, A) JP-A-8-223073 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/40 H04B 1/26

Claims (3)

(57) [Claims] The transmission frequency is 940 to 948 MHz.
Ri, a first frequency band domain received frequency is 810～818MHz, transmission frequency 925~940MHz der
Ri, in the wireless communication apparatus superheterodyne which can be used in 2-band of the second frequency band domain received frequency is 870～885MHz, the oscillation frequency band of both transmission and reception local oscillator 925～
And 948MHz, the reception local signal, the at the time of the first frequency band used the transmission and reception shared local oscillator output, using a signal obtained by frequency converting the both transmission and reception local oscillator output to 1000~1015MHz during a second frequency band used A wireless communication device characterized by the above-mentioned. 2. An oscillation frequency Fref of a reference oscillator in the wireless communication apparatus according to claim 1, wherein Fref = 75 / N (MH
z, where, N is chosen integer), when a second frequency band used, the reference oscillator outputting the multiplying to 75MHz using N multiplier, the transmission and reception shared frequency by a signal of 75MHz which is multiplied with the local oscillator output 2. The wireless communication device according to claim 1, wherein a received local signal is obtained by up-conversion by a converter. 3. The wireless communication device according to claim 2, wherein the power of the N-multiplier is turned off when the first frequency band is used.