JP2000124825A - Circuit and method of receiving - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reception circuit capable of improving reception characteristics and reducing power consumption. SOLUTION: This circuit, provided with a temperature-compensated crystal oscillator (TCXO) 10 for generating source oscillations being the base of set as a whole, a frequency divider circuit 11 for generating the source oscillation of a demodulating part and various operating clocks by dividing the oscillation frequency of the TCXO 10, a demodulating part 12 for generating a regenerative reference signal (AFCIF) by sampling a reception signal with the source oscillation of the demodulating part, and frequency correcting means 13 and 14 for generating the frequency corrected signals of the AFCIF, is provided with a demodulating part source oscillation generating means 15 for generating a second demodulating part source oscillation from the output of the frequency divider circuit 11 and a selecting means 16 for selecting one of the demodulating part source oscillations generated by the frequency divider circuit 11 and the second demodulating part source oscillation and supplying it to the demodulating part 12. By switching the source oscillation of the demodulating part 12 according to the conditions, reception characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile phone, a receiving circuit and a receiving method thereof, and a mobile communication system using the mobile phone. More particularly, the present invention aims to improve the receiving characteristics of the mobile phone.

[0002]

2. Description of the Related Art A digital portable telephone used in a mobile communication system such as a PDC (Personal Digital Cellular) system uses a common clock source for a clock sent to each functional block, thereby reducing the size of the device and reducing the size of the device. Power consumption is being reduced.

As shown in FIG. 4, a receiving circuit of a conventional portable telephone has a temperature-compensated crystal oscillator (TCXO) 40 as a clock source, and a frequency divider for dividing the oscillation frequency of the TCXO 40 to generate various clocks. A circuit 41, a demodulation unit 42 for demodulating the IF signal and outputting a reproduction reference signal (AFCIF), a reproduction clock and demodulated data, and a frequency correction unit 43 for generating an AFCIF frequency correction signal and outputting the signal to the demodulation unit 42
And a CP for setting a frequency correction value in the frequency correction unit 43
U44.

In this receiving circuit, a frequency dividing circuit 41 divides a frequency of a clock supplied from a TCXO 40, and generates a source oscillation of a demodulating section 42 and an operation clock of each functional block. By using a common clock source in this way, the device can be reduced in size and power consumption can be reduced.

[0005] The demodulation section 42 samples the IF signal with the demodulation section source oscillation, generates an AFCIF signal necessary for symbol determination and a reproduction clock, generates demodulated data using these, and outputs them. .

[0006] Originally, the source vibration of the demodulation section 42 is IF frequency × N
The demodulation unit 42 uses this source oscillation to generate A
Generate an FCIF signal. However, in a device that uses a common clock source, the oscillation frequency of the TCXO 40 is the least common multiple of the system-determined frequency (transmission clock, audio processing clock, etc.). The demodulation unit source oscillation to be output is (IF frequency × N
Times) ± α clock.

For this reason, the frequency correction signal generated by the frequency correction unit 43 is periodically output to the demodulation unit 42,
42 corrects the AFCIF signal using the frequency correction signal. By doing so, the source vibration of the demodulation unit 42 becomes (I
(F frequency x N times) ± α
An FCIF signal can be obtained. Further, when the value of ± α of the source vibration changes, the CPU 44 changes the frequency correction value set in the frequency
43 varies the correction frequency based on this change. By doing so, it becomes possible to cope with a change of ± α.

[0008]

However, in the conventional receiving circuit, the source oscillation of the demodulation unit is (IF frequency × N times) ± α
When the clock is used, the reception characteristic is slightly deteriorated due to the jitter at the time of correction as compared with the case where the source oscillation of IF frequency × N times is used. Such a state is not a problem when the electric field is strong or the reception characteristics are stable, but it is necessary to improve the reception characteristics when the electric field is weak or a burst error occurs.

The present invention solves such a conventional problem, and provides a receiving circuit and a receiving method capable of improving the receiving characteristic and reducing the power consumption by appropriately switching the source oscillation of the demodulating section. It is another object of the present invention to provide a mobile phone having the receiving circuit and a mobile communication system using the mobile phone.

[0010]

Therefore, in a receiving circuit according to the present invention, a demodulation section source oscillation generating means for generating a second demodulation section oscillation from the output of the frequency dividing circuit, and a second signal generated by the frequency dividing circuit. Selecting means for selecting any one of the first demodulation section source oscillation and the second demodulation section oscillation generated by the demodulation section source oscillation generation section and supplying it to the demodulation section.

Further, in the receiving method of the present invention, the oscillation frequency of the TCXO is divided to generate the first oscillation of the demodulation unit, and the first oscillation of the oscillation frequency of the TCXO is divided into the first signal.
Generates a second demodulation unit oscillation having a smaller difference with respect to the reception frequency N times as large as the demodulation unit oscillation, and selects a demodulation selected from the first demodulation unit oscillation or the second demodulation unit oscillation. AFCIF is generated by sampling the received signal with the local oscillator, and the first
When the AFCIF is generated by selecting the source
This AFCIF is corrected by a frequency correction signal.

As described above, by switching the demodulation unit source oscillation used for sampling the received signal according to the situation, it is possible to improve the reception characteristics and reduce the power consumption.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The invention as set forth in claim 1 of the present invention comprises a TCXO for generating a source vibration on which the entire set is based;
A frequency dividing circuit that divides the oscillation frequency of the TCXO to generate a demodulator source oscillation and various operation clocks; a demodulation unit that samples the received signal with the demodulation source oscillation to generate an AFCIF;
A frequency correction means for generating a frequency correction signal of AFCIF.
Either a first demodulation unit oscillation generated by the frequency divider circuit or a second demodulation oscillation generated by the demodulation unit oscillation generation unit. And selecting means for supplying the selected signal to the demodulation unit, and switching the source oscillation of the demodulation unit according to the situation, so that the reception characteristics can be improved.

According to a second aspect of the present invention, the demodulation section source oscillation generating means has a second demodulation section source oscillation having a small deviation from the first demodulation section oscillation with respect to the reception frequency as compared with the first demodulation section oscillation. When the AFCIF is generated by sampling the received signal with the demodulator source oscillation, the frequency correction of the AFCIF becomes unnecessary.

According to a third aspect of the present invention, the demodulation unit source oscillation generating means is provided with a VCO for outputting the second demodulation unit source oscillation, and a deviation from the VCO with respect to an N-fold reception frequency is small. Source vibration is output.

According to a fourth aspect of the present invention, the selecting means selects the first demodulation section source oscillation when the reception level is high, and selects the second demodulation section source oscillation when the reception level is low. This makes it possible to improve the reception characteristics when the reception level is low.

According to a fifth aspect of the present invention, the selection means selects the first demodulation unit power source in the continuous reception mode / standby mode, and selects the second demodulation unit power source in the call mode. Is selected, and it is possible to improve reception characteristics in a call mode in which good reception characteristics are required.

According to a sixth aspect of the present invention, when the low reception level continues in the continuous reception mode / standby mode, the selection means switches the first demodulation section source oscillation to the second demodulation section source oscillation, and makes a call. When the high reception level continues in the mode, the second demodulation section source oscillation is switched to the first demodulation section source oscillation, so that it is possible to improve reception characteristics and reduce power consumption.

According to a seventh aspect of the present invention, a source oscillation which is the basis of the entire set is generated by the TCXO, the received signal is sampled by the demodulation source oscillation generated by dividing the oscillation frequency of the TCXO, and the AFCIF is processed. Generate and optionally use this AFC
In a receiving method for correcting IF with a frequency correction signal,
The oscillation frequency of the CXO is divided to generate the first oscillation of the demodulation unit, and the signal obtained by dividing the oscillation frequency of the TCXO is shifted N times from the oscillation frequency of the first demodulation unit with respect to the reception frequency. Generates a second demodulation section source oscillation having a small value, samples the received signal with a demodulation section source oscillation selected from the first demodulation section oscillation or the second demodulation section oscillation, generates an AFCIF, The AFCIF is corrected by the frequency correction signal when the AFCIF is generated by selecting the first demodulator source oscillation, and the demodulation source oscillation used for sampling the received signal is switched according to the situation. As a result, the reception characteristics can be improved.

According to the present invention, when the reception level is high, the first demodulation section source oscillation is selected, and when the reception level is low, the second demodulation section source oscillation is selected. Therefore, it is possible to improve the reception characteristics when the reception level is low.

According to a ninth aspect of the present invention, the first demodulation section source oscillation is selected in the continuous reception mode / standby mode, and the second demodulation section source oscillation is selected in the talking mode. Thus, it is possible to improve reception characteristics in a call mode in which good reception characteristics are required.

According to a tenth aspect of the present invention, when the low reception level continues in the continuous reception mode / standby mode, the first demodulation section source oscillation is switched to the second demodulation section oscillation, and high reception is performed in the talking mode. When the level continues, the second demodulation section source oscillation is switched to the first demodulation section source oscillation, so that it is possible to improve reception characteristics and reduce power consumption.

According to an eleventh aspect of the present invention, the receiving circuit according to any one of the first to sixth aspects is provided in a digital mobile phone, and the size, power consumption, and receiving characteristics of the mobile phone are improved. be able to.

According to a twelfth aspect of the present invention, a mobile communication system is constituted by the digital portable telephone according to the eleventh aspect, and a communication system capable of receiving with good communication quality can be constructed. it can.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(First Embodiment) As shown in FIG. 1, the receiving circuit of the first embodiment divides the frequency of the oscillation frequency of a temperature-compensated crystal oscillator (TCXO) 10 as a clock source and the oscillation frequency of the TCXO 10. Divider circuit 11 that generates various clocks
A demodulation unit 12 that samples an IF signal with a demodulation unit source and outputs a reproduction reference signal (AFCIF), a reproduction clock, and demodulated data; Voltage-controlled oscillator (V
CO) 15 and the demodulation unit source oscillation B of IF frequency × N times output from the VCO 15 to the demodulation unit 12 or the frequency dividing circuit 11
A selector 16 for switching and outputting the demodulation unit source oscillation A of (IF frequency × N times) ± α output from the A / D converter, a frequency correction unit 13 for generating an AFCIF frequency correction signal and outputting it to the demodulation unit 12, A CPU 14 is provided for setting a frequency correction value in the correction unit 13 and for setting switching of the source oscillation of the demodulation unit in the selector 16.

The operation of the receiving circuit will be described. In this receiving circuit, the frequency dividing circuit 11 divides the frequency of the clock supplied from the TCXO 10, and outputs the operating clock of each functional block, the demodulation unit source oscillation A of (IF frequency × N times) ± α, and VC
And an output signal to O15. The VCO 15 uses a PLL (not shown) to remove the frequency difference between the signal input from the frequency divider 11 and the signal of IF frequency × N times, and
An N-fold demodulator source oscillation B is generated and output to the selector 16.

Thus, as the source oscillation of the demodulation unit 12, (IF
(Frequency × N times) ± A demodulation source oscillation A and IF frequency × N
A double demodulation source oscillation B is generated.

The source oscillation of the demodulation unit 12 is always
, The reception characteristics are improved, but the voltage controlled oscillator 15
The current consumption increases by the amount of the operation. On the other hand, if the demodulation unit source oscillation A is always used as the source oscillation of the demodulation unit 12, the reception characteristics deteriorate when a weak electric field or a burst error occurs, as described above.

For this reason, the CPU 14 sets the reception level (RS
When SI) is sufficiently high, the selector 16 is instructed to select the demodulation unit source oscillation A generated by the frequency dividing circuit 11, and when the reception level is low or the frequency of occurrence of burst errors is high, The selector 16 is instructed to select the demodulation unit source oscillation B generated by the voltage controlled oscillator 15.

The selector 16 outputs the demodulation unit power specified by the CPU 14 to the demodulation unit 12, and the demodulation unit 12 samples the IF signal with the demodulation power and outputs an AFCIF signal.

When the demodulator source oscillation A of (IF frequency × N times) ± α is selected by the selector 16, the frequency correction signal generated by the frequency correction unit 13 is periodically transmitted as in the conventional circuit. The signal is output to the demodulation unit 12, and the demodulation unit 12 corrects the AFCIF signal using the frequency correction signal. Further, when the value of ± α of the source vibration changes, the CPU 14 changes the frequency correction value set in the frequency correction unit 13, and the frequency correction unit 13 changes the correction frequency based on this change.

As described above, in the receiving circuit of this embodiment, when the reception level is low or the frequency of occurrence of the burst error is high, the source frequency of the demodulation unit is (IF frequency × N times).
And the demodulation unit source B having an extremely small deviation with respect to can be selected, so that it is possible to reduce the power consumption in a good reception environment while improving the reception characteristics when the reception environment is bad. Can be.

(Second Embodiment) The receiving circuit of the second embodiment can switch the frequency of the source oscillation of the demodulation unit according to the reception mode.

As shown in FIG. 2, the receiving circuit includes a CPU 24 for setting the selection of the demodulation unit source oscillation by the selector 26 in accordance with the reception mode. Other configurations are the same as those of the first embodiment (FIG. 1).

The CPU 24 instructs the selector 26 to select the demodulation section source B in the communication mode (voice, data communication) where good reception characteristics are required, and performs continuous reception for synchronization acquisition / holding. In the mode and the standby mode, the selector 26 is instructed to select the demodulation unit source oscillation A.

Therefore, in the receiving circuit of this embodiment,
In the call mode (voice and data communication), the demodulation unit source B having zero or extremely small deviation from (IF frequency × N times) can be selected as the demodulation unit source oscillation. It is possible to improve reception characteristics in a call mode while reducing power consumption in the mode.

(Third Embodiment) The receiving circuit according to the third embodiment can switch the frequency of the demodulation unit source oscillation according to the reception level and the reception mode.

As shown in FIG. 3, the receiving circuit includes a CPU 34 for setting the selection of the demodulation unit source oscillation by the selector 36 according to the reception mode and the reception level. Other configurations are the same as those of the first embodiment (FIG. 1).

The CPU 34 instructs the selector 36 to select the demodulation unit source B in the call mode (voice and data communication), and in the continuous reception mode and the standby mode, in which synchronization acquisition / holding is intended, and the standby mode. The selector 36 is instructed to select the shake A. Also, even in the call mode, if the reception level (RSSI) continues to be sufficiently high,
When the demodulation unit source A is selected and the reception level is low or the frequency of occurrence of burst errors is high even in the continuous reception mode / standby mode, the demodulation unit source B is selected. The selector 36 is designated.

Therefore, in the receiving circuit of this embodiment,
In each reception mode, it is possible to improve reception characteristics and reduce power consumption.

Further, by providing the receiving circuit of each embodiment in a digital portable telephone, it is possible to reduce the size and power consumption of the apparatus by using a common clock source, and to improve the receiving characteristics.

Further, by using this portable telephone, a mobile communication system capable of performing stable communication with low power consumption can be constituted.

[0044]

As is apparent from the above description, the receiving circuit and the receiving method of the present invention can realize both reduction of power consumption and improvement of receiving characteristics by switching the source oscillation of the demodulation section. it can.

Also, by applying this receiving circuit to a mobile phone, the size and power consumption of the mobile phone can be reduced, and the receiving characteristics can be improved. Thus, a mobile communication system capable of performing stable communication can be configured.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a receiving circuit according to a second embodiment of the present invention;

FIG. 3 is a block diagram of a receiving circuit according to a third embodiment of the present invention;

FIG. 4 is a block diagram of a conventional receiving circuit.

[Explanation of symbols]

 10, 20, 30, 40 Temperature Compensated Crystal Oscillator (TCXO) 11, 21, 31, 41 Divider 12, 22, 32, 42 Demodulator 13, 23, 33, 43 Frequency Corrector 14, 24, 34, 44 CPU 15, 25, 35 Voltage controlled oscillator (VCO) 16, 26, 36 Selector

Claims (12)

[Claims] 1. A temperature-compensated crystal oscillator (TCXO) for generating a source oscillation as a basis of an entire set, and a frequency dividing circuit for dividing an oscillation frequency of the TCXO to generate a demodulation source oscillation and various operation clocks. A demodulation unit that samples a received signal with a demodulation unit source and generates a reproduction reference signal (AFCIF);
A receiving circuit comprising: a frequency correcting means for generating a frequency correction signal of AFCIF; a demodulating section power source generating means for generating a second demodulating section power source from an output of the frequency dividing circuit; Selecting means for selecting either the first demodulation section source oscillation or the second demodulation section oscillation generated by the demodulation section oscillation generation section and supplying the selected demodulation section oscillation to the demodulation section. circuit. 2. The method according to claim 1, wherein the demodulation section source oscillation generation means includes N second demodulation section source oscillations as compared with the first demodulation section source oscillations.
2. The receiving circuit according to claim 1, wherein a source oscillation having a small shift with respect to a double reception frequency is generated. 3. The receiving circuit according to claim 1, wherein the demodulation unit source oscillation generating means includes a voltage controlled oscillator (VCO) that outputs the second demodulation unit source oscillation. 4. The selection means selects the first demodulation section source oscillation when the reception level is high, and selects the second demodulation section source oscillation when the reception level is low. The receiving circuit according to claim 1, 2, or 3. 5. The method according to claim 1, wherein the selecting unit selects the first demodulation unit source oscillation in a continuous reception mode / standby mode.
4. The reception circuit according to claim 1, wherein the second demodulation unit source oscillation is selected in a call mode. 6. When the low reception level continues in the continuous reception mode / standby mode,
The first demodulation unit source is switched to the second demodulation unit source, and in the communication mode, when the high reception level continues, the second demodulation unit source is switched to the first demodulation unit source. The receiving circuit according to claim 5, wherein the receiving circuit is switched. 7. A source oscillation which is the basis of the entire set is generated by the TCXO, and a received signal is sampled by the demodulation source oscillation generated by dividing the oscillation frequency of the TCXO to generate an AFCIF. In the receiving method for correcting the AFCIF with the frequency correction signal, the oscillation frequency of the TCXO is frequency-divided to generate a first demodulation unit oscillation, and the signal obtained by dividing the oscillation frequency of the TCXO is converted to the first signal. A second demodulation unit oscillation having a smaller difference with respect to the reception frequency N times as large as the demodulation unit oscillation is generated and selected from the first demodulation unit oscillation or the second demodulation unit oscillation. A is obtained by sampling the received signal with
Generate FCIF, select the first demodulation unit source oscillation, and
A receiving method, wherein when the FCIF is generated, the AFCIF is corrected with a frequency correction signal. 8. When the reception level is high, the first demodulation section source oscillation is selected. When the reception level is low, the second demodulation section source oscillation is selected.
8. The receiving method according to claim 7, wherein the demodulation unit source oscillation is selected. 9. The method according to claim 1, wherein the first demodulator source oscillation is selected in a continuous reception mode / standby mode, and the second demodulation source oscillation is selected in a speech mode. Item 7. The receiving method according to Item 7. 10. When the low reception level continues in the continuous reception mode / standby mode, the first demodulation section power source is switched to the second demodulation section source oscillation, and the high reception level continues in the call mode. The receiving method according to claim 9, wherein the second demodulation unit source oscillation is switched to the first demodulation unit oscillation. 11. A digital mobile phone comprising the receiving circuit according to claim 1. 12. A mobile communication system constituted by the digital mobile phone according to claim 11.