JPH10242885A - Reference frequency control method, reference frequency control circuit, and mobile radio communication device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a wireless communication device that performs automatic frequency control and performs intermittent reception. SOLUTION: A wireless communication signal reaching a receiving unit 3 is combined with a receiving local oscillation signal input from a synthesizer 4, converted into an intermediate frequency signal, and reaches a signal processing unit 5. The signal processing unit 5 processes the signal and supplies it to the speaker 24, detects the frequency error of the reference oscillator 8 from the intermediate frequency signal, and sends it to the switching circuit 20. When the apparatus is in the communication state, the time constant circuit 7A having a large time constant is selected, and when the apparatus is performing intermittent reception, the time constant circuit 7B having a small time constant is selected. The frequency of the reference frequency signal of the reference oscillator 8 is corrected in accordance with the signal of the frequency error given via one of the time constant circuits 7A and 7B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference frequency control method adopted in a radio communication system for processing a received signal with reference to a signal generated from a reference frequency signal, and for correcting a frequency error of the reference frequency signal. .

[0002]

2. Description of the Related Art Generally, in a digital radio communication device such as a PDC (Digital Cellular Phone for Japan), the receiving characteristic is significantly deteriorated due to the frequency deviation of a reference signal oscillator.
(Automatic frequency control).

FIG. 5 shows a configuration of a conventional general wireless communication device. In this wireless communication device, a signal received by an antenna 1 is split by a duplexer 2 to reach a receiving unit 3, where it is combined with a signal of a certain frequency given from a synthesizer 4, and the combined signal is processed by a signal processing unit. Reaches 5. Control unit 6
Controls the signal processing unit 5 according to an instruction from the operation unit 25. The signal processing unit 5 processes the synthesized signal and supplies the processed signal to the speaker 24, detects a frequency error of the reference frequency signal from the synthesized signal, and outputs a correction signal corresponding to the error to the time constant circuit 7. In the time constant circuit 7, the correction signal is band-limited and transmitted to the reference oscillator 8. The reference oscillator 8 generates a reference frequency signal, and its frequency changes according to a correction signal given from the time constant circuit 7. The synthesizer 4 generates a plurality of signals having different frequencies based on a signal provided from the reference oscillator 8.

On the other hand, the signal processing unit 5 is controlled by the control unit 6, processes a signal given from the microphone 23, and outputs the processed signal to the transmission unit 9. This signal is modulated by the signal from the synthesizer 4 in the transmission unit 9 and transmitted to the base station via the duplexer 2 and the antenna 1.

FIG. 6 is a block diagram of A in such a wireless communication device.
FIG. 3 is a diagram illustrating details of an FC circuit. A wireless communication signal transmitted via a wireless communication channel from a base station (not shown)
The signal is input to the receiving unit 3 via the antenna 1 and the duplexer 2.
Here, the signal is combined with the reception local oscillation signal input from the synthesizer 4 and converted into an intermediate frequency signal.

The intermediate frequency signal is sampled by an A / D converter 11 and then input to a phase detection circuit 12,
This phase detection circuit 12 detects the phase of the received signal.
The phase detected here is input to the delay detection circuit 13.

[0007] The delay detection circuit 13 detects a phase difference between one symbol based on the phase detected by the phase detection circuit 12, and inputs the obtained phase difference to a determination circuit 14 and a frequency error detection circuit 15. The determination circuit 14 establishes clock synchronization of the detected phase difference and determines received data.

On the other hand, a frequency error detection circuit 15 detects a frequency error from the phase difference. Then, this detection result is subjected to D /
The signal is converted into an analog signal by the A conversion circuit 17 and input to the reference oscillation circuit 18.

The reference oscillation circuit 18 includes a D / A conversion circuit 17
Generates a reference frequency signal having a frequency corrected by the signal given by the controller and outputs it to the synthesizer 4. The synthesizer 4 generates a reception local oscillation signal based on the reference frequency signal, and inputs the signal to the reception unit 3.

The above-mentioned A / D converter 11, phase detection circuit 1
2. The delay detection circuit 13, the determination circuit 14, and the frequency error detection circuit 15 are included in the signal processing unit 5 shown in FIG. 5, and the low-pass filter 16 is used for the time constant circuit 7 shown in FIG. The circuit including the D / A conversion circuit 17 and the reference oscillation circuit 18 is the reference oscillator 8 shown in FIG.

As described above, in the conventional AFC circuit of a wireless communication device, the delay detection circuit 13 detects a phase difference based on the phase detected by the phase detection circuit 12, and the detection result is used as an evaluation criterion. 15 detects the frequency error, and corrects the frequency of the reference frequency signal of the reference oscillator 8 based on the frequency error. Here, the low-pass filter 16
That is, the time constant circuit 7 plays a role of a smoothing circuit, and the change in the frequency error from the frequency error detection circuit 15 is transmitted gradually. Therefore, the time constant circuit 7
This circuit determines the response speed of the FC, that is, the time constant.

When the wireless communication device is of a portable type, in order to save power, it is common to perform a so-called intermittent reception in which a reception operation is performed intermittently in a standby state in which no call is made. . Conventionally, in a wireless communication device that performs intermittent reception in this way, the response speed of AFC is constant regardless of whether it is during intermittent reception or during a call.

According to this method, when the response speed of the AFC is set to a high speed, it is convenient because the response is performed in a short time at the time of intermittent reception, but at the time of a call, the wrong frequency is affected by disturbance due to radio wave interference. When the information is detected, a problem occurs that the reception frequency fluctuates instantaneously. In addition, when the response speed of the AFC is set to a low speed, the reception frequency does not fluctuate during a telephone call, which is convenient. However, the reception frequency cannot be drawn during intermittent reception.

[0014]

As described above, the AFC
In a wireless communication device having the above function and performing intermittent reception during standby, the response speed of the AFC has been constant in any of the intermittent reception and the telephone call in the past. For this reason, if the response speed is set to high speed, it is susceptible to disturbance during a call, the receiving frequency fluctuates, and if the response speed is set to low speed, There was a problem that the frequency could not be drawn.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to provide an AFC system which is less susceptible to disturbance during communication and which does not cause any trouble in receiving operation during intermittent reception. It is to be.

[0016]

According to a reference frequency control method of the present invention, an error in the frequency of a reference frequency signal is detected based on the frequency of a received signal, and the control of the frequency of the reference frequency signal is performed in accordance with the error. Is performed using the first time constant during the standby operation of the received signal, and is performed using the second time constant larger than the first time constant during the communication operation.

For this reason, the response of the frequency control is fast during the standby operation, so that the reception frequency can be easily pulled in.
In addition, the response of frequency control is slow during communication, so that it is less likely to be affected by disturbance.

A reference frequency control circuit according to the present invention is a circuit for detecting a frequency error of a reference frequency signal based on a frequency of a received signal and controlling the frequency of the reference frequency signal in accordance with the error. Control means is provided for controlling the frequency of the reference frequency signal using a first time constant during a signal waiting operation and using a second time constant larger than the first time constant during a communication operation. With this control means, the response of the reference frequency control is made faster during standby, and the reception frequency is more easily drawn. Also, during communication, the response of the reference frequency control becomes slow, making it less susceptible to disturbances.

In the reference frequency control circuit according to the present invention, the control means includes a first low-pass filter having a first time constant and a second low-pass filter having a second time constant. It is means for selecting the first low-pass filter at times and selecting the second low-pass filter at the time of communication operation to control the frequency of the reference frequency signal. According to such a configuration, at the time of standby, the first low-pass filter having a small time constant can be selected to speed up the response of the reference frequency control, thereby improving the reception frequency. Further, at the time of communication, it is possible to select the second low-pass filter having a large time constant to delay the response of the reference frequency control, thereby making it less susceptible to disturbance.

Further, the mobile radio communication apparatus of the present invention has a reference frequency signal generating means for generating a reference frequency signal, a received signal received via a radio line, and a reference frequency signal generated by the reference frequency signal generating means. Receiving means for generating an intermediate frequency signal from the signal; detecting means for detecting a frequency error of a reference frequency signal generated by the reference frequency signal generating means based on the intermediate frequency signal generated by the receiving means; Based on the error detected by the means,
And control means for controlling the frequency of the reference frequency signal using a first time constant during a reception operation of the received signal and using a second time constant larger than the first time constant during a communication operation. According to this configuration, the response of the reference frequency control at the time of standby becomes faster, and the reception frequency is more easily drawn. Also, during communication, the response of the reference frequency control becomes slow, making it less susceptible to disturbances.

In the mobile radio communication apparatus according to the present invention, the control means includes a first low-pass filter having a first time constant and a second low-pass filter having a second time constant. The first low-pass filter is selected, and during the communication operation, the second low-pass filter is selected to control the frequency of the reference frequency signal. Therefore, the response speed of the reference frequency control can be changed with a simple configuration.

[0022]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention. The wireless communication signal reaching the antenna 1 is split by the duplexer 2 and reaches the receiving unit 3. The receiving section 3 combines the received local oscillation signal and the received signal supplied from the synthesizer 4 and outputs the combined signal to the signal processing section 5. The control unit 6 includes a microprocessor, and controls the signal processing unit 5 according to an instruction from the operation unit 25. The signal processing unit 5 processes the synthesized signal and supplies the processed signal to the speaker 24, detects a frequency error of the reference frequency signal from the synthesized signal, and outputs a correction signal corresponding to the error to the switching circuit 20. . The time constant circuits 7A and 7B are circuits that limit the band of the applied correction signal with different time constants and transmit the band to the reference oscillator 8 via the switching circuit 21. Further, the control unit 6 determines, based on an instruction from the operation unit 25, whether it is in a standby state or a telephone call, and switches the connection points in the switching circuits 20 and 21 according to the determination. Furthermore,
When in the standby state, the control unit 6 turns on and off a power supply unit (not shown) to intermittently perform the reception processing operation of each unit. Each of the time constant circuits 7A and 7B is specifically composed of a low-pass filter. Here, the time constant A of the time constant circuit 7A is larger than the time constant B of the time constant circuit 7B.

The reference oscillator 8 has the same configuration as that shown in FIG. 6, and generates a reference frequency signal.
The frequency is corrected according to a correction signal provided from the time constant circuits 7A and 7B. The synthesizer 4 generates a plurality of signals having different frequencies based on a signal provided from the reference oscillator 8.

The signal processing section 5 is controlled by the control section 6 to process a signal given from the microphone 23 and output the processed signal to the transmission section 9. This signal is modulated by the signal from the synthesizer 4 in the transmission unit 9 and transmitted to the base station via the duplexer 2 and the antenna 1.

In this embodiment, the antenna 1, the duplexer 2, the synthesizer 4 and the receiving section 3 constitute a receiving means, the reference oscillator 8 constitutes a reference frequency signal generating means,
The signal processing unit 5 constitutes a reception signal processing unit, the signal processing unit 5 and the control unit 6 constitute an error detection unit, and the frequency correction function of the reference oscillator 8 corresponds to the frequency control unit. The control unit 6, the switching circuits 20, 21 and the time constant circuits 7A, 7B constitute a response speed changing unit.

Next, the operation of the device configured as described above will be described.
With reference to the flowchart of FIG. 2, description will be made focusing on AFC. The control unit 6 follows an instruction from the operation unit 25,
It judges whether it is a standby (intermittent reception) or a call (S
1) The connection point of the switching circuits 20 and 21 is switched so that the time constant circuit 7A is selected for a call and the time constant circuit 7B is selected for a standby.

A radio communication signal transmitted from a base station (not shown) via a radio communication channel includes an antenna 1 and a duplexer 2.
, And is combined with a reception local oscillation signal input from the synthesizer 4 to be converted into an intermediate frequency signal. The reception local oscillation signal is generated from a reference frequency signal provided from the reference oscillator 8.

This intermediate frequency signal reaches the signal processing section 5. The signal processing unit 5 has a configuration similar to the configuration shown in FIG. 6, detects a phase from the intermediate frequency signal, detects a phase difference between one symbol from the phase, and detects a frequency error from the phase difference. Is detected. The signal indicating this frequency error reaches the switching circuit 20.

Here, when the apparatus is in a talking state, the connection points in the switching circuits 20 and 21 are switched so as to select the time constant circuit 7A, and the time constant circuit 7A outputs a signal indicating the frequency error. Is band-limited, and the result is given to the reference oscillator 8 (S2). The reference oscillator 8 performs D / A conversion of the applied signal (S3), corrects the frequency of the reference frequency signal based on the analog signal (S4), and sends the corrected reference frequency signal to the synthesizer 4. Here, since the time constant A of the time constant circuit 7A is large, the response of controlling the frequency of the reference frequency signal is slow. For this reason, the received signal is less likely to be affected by disturbance.

When the apparatus is in the standby state, the connection points in the switching circuits 20 and 21 are switched so as to select the time constant circuit 7B, and the time constant circuit 7B limits the signal indicating the frequency error to the band. Then, the result is given to the reference oscillator 8 (S5). The reference oscillator 8 performs D / A conversion of the applied signal (S3), corrects the frequency of the reference frequency signal based on the analog signal (S4), and sends the corrected reference frequency signal to the synthesizer 4. Here, since the time constant B of the time constant circuit 7B is small, the response of controlling the frequency of the reference frequency signal is fast. For this reason, the reception frequency is improved.

FIG. 3 is a diagram showing the time constant levels of AFC at the time of intermittent reception and at the time of a call.

FIG. 4 shows a second embodiment. In the present embodiment, the signal processing unit 5 detects the frequency error of the reference frequency signal from the received signal as in the first embodiment, but this frequency error is detected by the time constant circuit 6A in the control unit 6.
Is input to the reference oscillator 8 through The control unit 6 has a configuration of a myloprocessor, and the time constant circuit 6A represents a digital filter function provided in the myroprocessor. Here, the myloprocessor performs a low-pass filter operation process with a large time constant A in a call state, and performs a low-pass filter operation process with a small time constant B in a standby state. This change is made by changing the coefficient of the operation. Other configurations are the same as those of the first embodiment.

The operation of the present apparatus will be described focusing on AFC. The control unit 6 determines whether it is a standby mode or a telephone call in accordance with an instruction from the operation unit 25, and stores the result.

A radio communication signal transmitted from a base station (not shown) via a radio communication channel includes an antenna 1 and a duplexer 2.
, And is combined with a reception local oscillation signal input from the synthesizer 4 to be converted into an intermediate frequency signal. The reception local oscillation signal is generated from a reference frequency signal provided from the reference oscillator 8.

This intermediate frequency signal reaches the signal processing section 5. The signal processing unit 5 detects a phase from the intermediate frequency signal, detects a phase difference between one symbol from the phase, and detects a frequency error from the phase difference. The signal indicating the frequency error reaches the control unit 6.

Here, when the apparatus is in a talking state, the control unit 6 performs an operation as a low-pass filter with a time constant A to which the signal indicating the frequency error is input, and gives the result to the reference oscillator 8. . The reference oscillator 8 controls the frequency of the reference frequency signal according to the result, but since the time constant A is large, the control response is slow. For this reason, the received signal is less likely to be affected by disturbance.

If the apparatus is in the intermittent reception state, the control unit 6
Performs an operation as a low-pass filter with a time constant B to which the signal indicating the frequency error is input, and supplies the result to the reference oscillator 8. The reference oscillator 8 controls the frequency of the reference frequency signal according to the result, but since the time constant B is small, the control response is fast. For this reason, at the time of the intermittent reception, the reception frequency is improved.

As described above, the device of this embodiment has the same effects as the device of the first embodiment, but also has the effect of reducing the number of external circuits and the number of parts. .

[0039]

According to the reference frequency control method or the reference frequency control circuit of the present invention, it is possible to reduce the influence of disturbance during communication and to improve the reception frequency during intermittent reception.

Further, according to the reference frequency control circuit of the present invention, since two low-pass filters having different time constants are used, a simple configuration can be achieved.

The mobile radio communication apparatus according to the present invention has an effect that it is hardly affected by disturbance at the time of communication, and the reception frequency is well drawn during intermittent reception.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a diagram showing AFC time constant levels at the time of intermittent reception and at the time of communication in the first embodiment of the present invention.

FIG. 4 is a diagram showing an overall configuration of a second embodiment of the present invention.

FIG. 5 is a diagram showing an overall configuration of a conventional portable wireless communication device.

FIG. 6 is a diagram showing details of an AFC circuit of the device shown in FIG. 5;

[Explanation of symbols]

 Reference Signs List 3 receiving section 4 synthesizer 7A, 7B, 6A time constant circuit 8 reference oscillator 5 signal processing section 6 control section 20, 21 switching circuit

Claims (5)

[Claims] 1. A reference frequency control method for detecting a frequency error of a reference frequency signal based on a frequency of a received signal and controlling a frequency of the reference frequency signal in accordance with the error. A reference frequency control method, wherein a frequency of a reference frequency signal is controlled using a time constant of 1 and a second time constant larger than the first time constant during a communication operation. 2. A reference frequency control circuit for detecting a frequency error of a reference frequency signal based on a frequency of a received signal and controlling a frequency of the reference frequency signal in accordance with the error. A reference frequency control circuit, comprising: control means for controlling the frequency of a reference frequency signal using a time constant of 1 and a second time constant larger than the first time constant during a communication operation. 3. The control device according to claim 1, wherein the control means has a first time constant having a first time constant.
And a second low-pass filter having a second time constant, wherein the first low-pass filter is selected at the time of waiting for a received signal, and the second low-pass filter is selected at the time of communication operation, and a reference frequency is selected. 3. The reference frequency control circuit according to claim 2, wherein the frequency of the signal is controlled. 4. A reference frequency signal generating means for generating a reference frequency signal, and an intermediate frequency signal is generated from a received signal received via a radio line and a signal based on the reference frequency signal generated by the reference frequency signal generating means. Receiving means, and detecting means for detecting a frequency error of the reference frequency signal generated by the reference frequency signal generating means based on the intermediate frequency signal created by the receiving means, based on the error detected by the detecting means, Control means for controlling the frequency of the reference frequency signal using a first time constant during a reception operation of a reception signal and using a second time constant larger than the first time constant during a communication operation. A mobile radio communication device characterized by the above-mentioned. 5. The control means according to claim 1, wherein said control means has a first time constant having a first time constant.
And a second low-pass filter having a second time constant, wherein the first low-pass filter is selected at the time of waiting for a received signal, and the second low-pass filter is selected at the time of communication operation, and a reference frequency is selected. The mobile radio communication device according to claim 4, wherein the frequency of the signal is controlled.