JP3282682B2 - Mobile phone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile telephone.

[0002]

2. Description of the Related Art In an analog cellular mobile phone, for example, in the E-TACS system, the frequency band of the upstream channel is 872-905 MHz and the frequency band of the downstream channel is 917-950 MHz. The frequency difference between the paired up channel and down channel is 45 MHz.

For this reason, a portable telephone of the E-TACS system is configured, for example, as shown in FIG. That is, in FIG. 4, 10 is a transmitting circuit, 20 is a receiving circuit,
Numeral 40 denotes a PLL for setting a transmission / reception channel, and numeral 60 denotes a microcomputer for system control.

[0004] In the transmission circuit 10, a signal to be transmitted such as a voice signal, a data signal or a control signal is supplied from a terminal 11 to an FM modulation circuit 12.
Although not shown, the modulation circuit 12 is a VCO constituting a PLL, and a signal from a terminal 11 is supplied to the VCO as a control voltage.

Thus, the signal from the terminal 11 is converted into an FM signal S12 having a carrier frequency f12 of, for example, f12 = 90 MHz in the modulation circuit 12, and the FM signal S12 is supplied to the mixer circuit 13 and the buffer amplifier 14 outputs a local oscillation signal S41 having a predetermined frequency f41 to the mixer circuit 13.
And the frequency of the FM signal S12 is converted to an FM signal S13.

In this case, the frequency f41 of the signal S41 is changed between f41 = 962 to 995 MHz in accordance with the channel to be used. Therefore, the FM signal S
The 13 carrier frequency f13 is f13 = f41−f12 (1) = (962 to 995 MHz) −90 MHz = 872 to 905 MHz, that is, the carrier frequency of any one of the upstream channels. .

The mixer circuit 13 also outputs a signal component having a frequency (f41 + f12) of the sum of the signals S12 and S41, which is an unnecessary component and is ignored because it is removed by a subsequent filter. Hereinafter, the same applies to other mixer circuits).

Then, the FM signal S13 is supplied to the antenna 50 through the signal line of the preamplifier 15 → the band pass filter 16 having all the up channels as pass bands → the power amplifier 17 → the transmission band pass filter 18 of the antenna duplexer. Then, it is transmitted to the base station as an uplink channel transmission signal.

Also, the FM of the downlink channel from the base station is
Signal S21 is received by antenna 50. In this case, the carrier frequency f21 of the FM signal S21 is any one of f21 = 917 to 950 MHz, and is the frequency of the channel paired with the upstream channel. Therefore, as described above, f21−f13 = 45 MHz (2)

The signal S21 is supplied to the receiving bandpass filter 21 of the antenna duplexer → the high-frequency amplifier 22 →
The signal is supplied to the first mixer circuit 24 through a signal line of the band-pass filter 23 having all the downstream channels as pass bands, and a local oscillation signal S41 is extracted from the buffer amplifier 25.
The frequency f24 of the signal S21 is converted to a first intermediate frequency signal S24 of f24 = f41-f21 (3) = (962 to 995 MHz)-(917 to 950 MHz) = 45 MHz. You.

The signal S24 is supplied to the second mixer circuit 27 through the first intermediate frequency filter 26, and the second local oscillation circuit 28
The local oscillation signal is supplied to the mixer circuit 27 and the signal S24
Is frequency-converted into a second intermediate frequency signal having a predetermined frequency, and this signal is supplied to an FM demodulation circuit 32 through an amplifier 29 and a second intermediate frequency filter 31. Thus, the voice signal of the communication partner, the data signal or the control signal from the base station, etc. are taken out to the terminal 33.

[0012] In this case, the upstream and downstream channels used for a call or the like are determined by the frequency f41 of the signal S41. The signal S41 is formed by the PLL 40.

That is, in the PLL 40, the VCO 4
1, an oscillation signal S41 is taken out, and this signal S41 is supplied to the amplifiers 14 and 25 and the prescaler 4
2 and is frequency-divided to a frequency of 1 / n (n is a predetermined fixed frequency division ratio), and this frequency-divided signal is supplied to a variable frequency dividing circuit 43 and frequency-divided to a frequency of 1 / N. The frequency-divided signal is supplied to the phase comparison circuit 44. Further, an oscillation signal of the reference frequency is taken out from the oscillation circuit 45, and this oscillation signal is supplied to the comparison circuit 44.

In this manner, the phase of the frequency-divided signal from the frequency-dividing circuit 43 and the phase of the oscillation signal from the oscillation circuit 45 are compared in the comparison circuit 44, and the comparison output is supplied to the VCO 41 via the low-pass filter 46 as the control voltage. Is done.

In this case, the frequency of the frequency-divided signal from the frequency-dividing circuit 43 is n · N times the frequency of the oscillation signal S of the VCO 41.
Since the frequency f41 of the signal S41 is equal to the frequency f41 of the signal S41, the frequency f41 of the signal S41 is determined by setting the frequency division ratio N by the microcomputer 70. Therefore, by changing the frequency division ratio N,
Up and down channels can be set arbitrarily.

[0016]

By the way, the first intermediate frequency filter 26 is generally formed of a crystal filter in order to obtain a predetermined selectivity characteristic. However, if a crystal filter is used for a fundamental wave and its passing frequency is selected to be as high as 80 MHz, for example, the shape of the crystal filter becomes large. However, mobile phones are small,
It is required to be lightweight.

Therefore, when the first intermediate frequency filter 26 is constituted by a crystal filter, the first intermediate frequency f
24 is reduced to, for example, 45 MHz as described above, whereby the size of the crystal filter as the first intermediate frequency filter 26 is reduced, and the size and weight of the mobile phone are reduced.

By the way, when the above equation (1) is modified, the following is obtained. That is, f13 = f41−f12∴f41 = f13 + f12 (4) By transforming equation (2), f21−f13 = 45 MHz∴f21 = 45 MHz + f13 (5)

By substituting equations (4) and (5) into equation (3), f24 = f41−f21 = (f13 + f12) − (45 MHz + f13) = f12−45 MHz45f12 = f24 + 45 MHz (6) Become.

Therefore, as described above, when a crystal filter is used as the first intermediate frequency filter 26 and f24 = 45 MHz for miniaturization and weight reduction, the signal S12 becomes f12 must be 90 MHz.

However, if f12 = 90 MHz, the signal S
The frequency fhm of the twelfth harmonic is fhm = 90 MHz × 11 = 990 MHz, and as shown in FIG.
In the band of 962 to 995 MHz of the oscillation frequency f41.

In this case, when the VCO 41 and the modulation circuit 12 are assembled with discrete components, the VCO 4
By arranging circuits or components in consideration of the isolation between the circuit 1 and the modulation circuit 12, no problem occurs.

However, due to miniaturization and weight reduction, VC
When the O41 and the modulation circuit 12 are integrated on the same chip, it is difficult to sufficiently isolate the VCO 41 and the modulation circuit 12 from each other.
Interference occurs between 41 and the modulation circuit 12,
For example, unnecessary spurious components are generated.

The present invention is to solve such a problem.

[0025]

Therefore, according to the present invention, when the reference numerals of the respective parts correspond to the embodiments described later, the transmitting circuit 10, the receiving circuit 20, the transmitting circuit 10 and the receiving circuit 20, And a PLL 40 for supplying an oscillation signal having a frequency for setting those channels. The transmission circuit 10 converts the signal to be transmitted into an FM signal S12.
A modulation circuit 12 and a mixer circuit 13 for frequency-converting the FM signal S12 into an up-channel signal by an oscillation signal. The receiving circuit 20 converts the down-channel signal S21 into
A first mixer circuit 24 for converting the frequency of the oscillation signal into a first intermediate frequency signal S24, a circuit 27 for converting the frequency of the first intermediate frequency signal S24 to a second intermediate frequency signal, and an FM for FM demodulating the second intermediate frequency signal A demodulation circuit 32, and sets the carrier frequency f12 of the FM modulation circuit 12 to an integral multiple of the sum of the intermediate frequency f24 of the first intermediate frequency signal S24 and the frequency difference between the upstream and downstream channels of 45 MHz. It is like that.

[0026]

When the first intermediate frequency f24 is set to, for example, 45 MHz, the frequency of the harmonics of the FM
Out of the oscillation frequency band, and the FM modulation circuit 12 and the VC
Interference with O41 is eliminated.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a circuit enclosed by a chain line is integrated into one chip. Then, F from the FM modulation circuit 12
The carrier frequency f12 of the M signal S12 is, for example, twice that in the case of the example of FIG. 4, that is, f12 = 180 MHz, and the FM signal S12 of this frequency f12 is
3 is supplied.

The oscillating signal S41 of the VCO 41 is supplied to the multiplying circuit 71 through the amplifier 14 and multiplied to a signal S71 having a double frequency 2f41, and the signal S71 is supplied to the mixer circuit 13 through the band-pass filter 72. You.

Therefore, the carrier frequency f13 of the FM signal S13 extracted from the mixer circuit 13 is f13 = 2f41-f12 (11) instead of the equation (1).

Then, the signal S13 is supplied to the frequency dividing circuit 75 through the amplifier 15, and is converted into a signal S75 having a half frequency f75. Therefore, f75 = f13 / 2 = f41−f12 / 2 (12)

In this case, the frequency f41 of the oscillation signal S41 varies between f41 = 962 and 995 MHz according to the channel to be used, as described above.

Therefore, the equation (12) is expressed as follows: f75 = f41−f12 / 2 = (962 to 995 MHz) −180 MHz / 2 = (962 to 995 MHz) −90 MHz = 872 to 905 MHz = f13 13), and the signal S75 is equivalent to the FM signal S13 in FIG.

The signal S75 is supplied to the power amplifier 17 through the bandpass filter 16 and the amplifier 76, and transmitted from the antenna 50.

The receiving circuit 20 and the like are the same as the conventional one.

According to such a configuration, since the frequency of the harmonic of the modulation signal S12 is an integer multiple of the frequency f12 of the signal S12, the distribution of the harmonic of the modulation signal S12 is as shown in FIG. 3B. The harmonics of the modulation signal S12 do not enter the band 962 to 995 MHz of the oscillation frequency f41 of the VCO 41.

Therefore, the VCO 41 and the modulation circuit 12
Even if it is difficult to obtain sufficient isolation from the VCO 41 and the modulation circuit 12, no interference occurs between the VCO 41 and the modulation circuit 12, so that the VCO 41 and the modulation circuit 12 are integrated on the same chip. The mobile phone can be reduced in size and weight.

The first intermediate frequency f24 of the receiving circuit 20
Can be reduced to, for example, 45 MHz, so that a small crystal filter can be used as the first intermediate frequency filter 26. Therefore, also from this point, the size and weight of the mobile phone can be reduced.

Moreover, for this purpose, a special technique or circuit is not required, and the IC can be integrated into a chip together with the VCO 41 and the modulation circuit 12 as shown by a chain line.

In the example shown in FIG. 2, the FM modulation circuit 1
2, an FM signal S12 of f12 = 180 MHz is extracted and supplied to the mixer circuit 13.

The frequency f41 of the oscillation signal S41 of the VCO 41 of the PLL 40 is twice that of the example in FIG. 4, that is, 2f41 = 1924 to 1990 MHz (14) in accordance with the channel to be used. You. In this case, the oscillation signal S41 is supplied to the prescaler 42 and frequency-divided to a frequency of 1 / 2n, and then supplied to the variable frequency dividing circuit 43. Thereafter, the processing of the PLL 40 is executed as in the example of FIG. You. Therefore, the frequency 2f41 of the equation (14) is realized.

Then, the oscillation signal S41 of the VCO 41 is supplied to the mixer circuit 13, so that the mixer circuit 1
3, the FM signal S13 of the frequency f13 represented by the equation (11)
The signal S13 is supplied to the frequency dividing circuit 75 through the amplifier 15, and is frequency-divided into a signal having a frequency of 1/2, that is, a signal S75 having a frequency f13 (= f75) represented by the equation (13). This signal S75 is supplied to the power amplifier 17 through the bandpass filter 16 and the amplifier 76, and transmitted from the antenna 50.

On the other hand, in the receiving circuit 20, the down-channel FM signal S21 from the band-pass filter 23 is output.
Is supplied to the first mixer circuit 24 and the VCO
The oscillation signal S41 from the signal 41 is supplied to the frequency dividing circuit 77 and is divided into a signal S74 having a frequency f74 of 1/2.

In this case, the frequency 2f41 of the oscillation signal S41 is
(14), the frequency f74 of the signal S74 is f74 = 2f41 / 2 = (1924-1990 MHz) / 2 = 962-995 MHz, and the signal S74 is the mixer circuit 2 in the example of FIG.
4 is equivalent to the oscillating signal S41 supplied to the control signal S4.

Therefore, a first intermediate frequency signal S24 having a frequency f24 = 45 MHz is extracted from the mixer circuit 24.
Thereafter, the same reception processing as in the example of FIG.
The demodulated output is taken out.

In this case, also in this example, the distribution of harmonics of the modulation signal S12 is as shown in FIG. 3B, and the band 962 to 995 MHz of the oscillation frequency f41 of the VCO 41 is obtained.
Never enter.

Therefore, the VCO 41 and the modulation circuit 12
Can be integrated into the same chip as
A small crystal filter can be used as the first intermediate frequency filter 26, which can contribute to a reduction in size and weight of the mobile phone. Also, as indicated by the dashed line, the VCO
41 and the modulation circuit 12 can be integrated into a chip.

In the above description, the carrier frequency f12 of the modulation circuit 12 is twice the conventional frequency of 90 MHz, but harmonics of the carrier frequency f12 do not fall within the band of the frequency f41 of the VCO 41 for channel setting. Any frequency may be used.

[0048]

According to the present invention, the harmonics of the modulation signal S12 have a frequency range of 962 to 995 M in the oscillation frequency f41 of the VCO 41.
Never enter Hz. Therefore, even if it is difficult to obtain sufficient isolation between the VCO 41 and the modulation circuit 12, no interference occurs between the VCO 41 and the modulation circuit 12.
2 can be integrated on the same chip as an IC, and the size and weight of the mobile phone can be reduced.

The first intermediate frequency f24 of the receiving circuit 20
Can be reduced to, for example, 45 MHz, so that a small crystal filter can be used as the first intermediate frequency filter 26. Therefore, also from this point, the size and weight of the mobile phone can be reduced.

Furthermore, the VCO 41 and the modulation circuit 12 can be integrated on a chip together with other circuits without requiring any special technique or circuit.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of the present invention.

FIG. 2 is a system diagram showing another example of the present invention.

FIG. 3 is a characteristic diagram showing a frequency distribution.

FIG. 4 is a system diagram for explaining the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 transmission circuit 12 FM modulation circuit 13 mixer circuit 18 transmission band-pass filter 20 reception circuit 21 reception band-pass filter 24 first mixer circuit 26 first intermediate frequency filter 27 second mixer circuit 27 second local oscillation circuit 31 second Intermediate frequency filter 32 FM demodulation circuit 40 PLL 41 VCO 42 prescaler 43 Variable frequency divider 44 Phase comparator 45 Oscillator 46 Low pass filter 60 Microcomputer 71 Multiplier 72 Band pass filter 75 Frequency divider 77 Frequency divider

Claims (4)

(57) [Claims] 1. A transmission circuit, a reception circuit, and a PLL for supplying an oscillation signal having a frequency for setting the channels to the transmission circuit and the reception circuit, wherein the transmission circuit includes a signal to be transmitted. And a mixer circuit for converting the frequency of the FM signal into an upstream channel signal by the oscillation signal. The reception circuit converts the downstream channel signal by the oscillation signal. A first mixer circuit for converting the frequency of the first intermediate frequency signal to a first intermediate frequency signal; a circuit for converting the frequency of the first intermediate frequency signal to a second intermediate frequency signal; and an FM demodulation circuit for performing FM demodulation of the second intermediate frequency signal. And adjusting the carrier frequency of the FM modulation circuit to the sum frequency of the intermediate frequency of the first intermediate frequency signal and the frequency difference between the upstream channel and the downstream channel. Mobile telephone which is set to double. 2. A transmission circuit, a reception circuit, and a PLL for supplying an oscillation signal having a frequency for setting the channels to the transmission circuit and the reception circuit, wherein the transmission circuit transmits a signal to be transmitted. And a mixer circuit for converting the frequency of the FM signal into an upstream channel signal by the oscillation signal. The reception circuit converts the downstream channel signal by the oscillation signal. A first mixer circuit for converting the frequency of the first intermediate frequency signal to a first intermediate frequency signal; a circuit for converting the frequency of the first intermediate frequency signal to a second intermediate frequency signal; and an FM demodulation circuit for performing FM demodulation of the second intermediate frequency signal. The carrier frequency of the FM modulation circuit is 2 times the sum of the intermediate frequency of the first intermediate frequency signal and the frequency difference between the upstream channel and the downstream channel. Mobile telephone set in. 3. A transmission circuit, a reception circuit, and a PLL for setting a channel of the transmission circuit and a channel of the reception circuit, wherein the transmission circuit converts a signal to be transmitted into an FM signal. The circuit and the oscillation signal from the PLL are multiplied by K (K is an integer of 2 or more)
A frequency multiplier for multiplying the frequency of the FM signal by a signal multiplied by the frequency multiplier, and an output signal of the mixer circuit divided into a frequency of 1 / K and an upstream channel. And a frequency dividing circuit for converting the signal of the down channel into the PLL.
A first mixer circuit that converts the frequency of the first intermediate frequency signal into a second intermediate frequency signal by using the oscillation signal of the first and second intermediate frequency signals; and an FM demodulation that performs FM demodulation of the second intermediate frequency signal. And a carrier frequency of the FM modulation circuit is set to K times a frequency of a sum of an intermediate frequency of the first intermediate frequency signal and a frequency difference between the upstream channel and the downstream channel. 4. A transmission circuit, a reception circuit, and a PLL for setting a channel of the transmission circuit and a channel of the reception circuit, wherein the transmission circuit converts a signal to be transmitted into an FM signal. A mixer circuit for converting the frequency of the FM signal with the oscillation signal of the PLL; and dividing an output signal of the mixer circuit into a frequency of 1 / K (K is an integer of 2 or more) to obtain an upstream channel. A frequency divider circuit for dividing the frequency of the PLL oscillation signal into a frequency of 1 / K; and a frequency divider for dividing a downstream channel signal into another frequency division signal. A first mixer circuit that converts the frequency of the first intermediate frequency signal into a second intermediate frequency signal based on an output signal of the circuit; a circuit that converts the frequency of the first intermediate frequency signal to a second intermediate frequency signal; and an FM that performs FM demodulation of the second intermediate frequency signal Demodulation circuit And a carrier frequency of the FM modulation circuit is set to K times a frequency of a sum of an intermediate frequency of the first intermediate frequency signal and a frequency difference between the upstream channel and the downstream channel.