JP2002314380A - System and method for automatically controlling frequency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To communicate with a base station without making the convergence time of a reference frequency long and without disconnecting a line even when the reference frequency deviates largely. SOLUTION: This automatic frequency control system for performing correction control of a reference frequency supplied to a PLL, is provided with an oscillator 6 having a frequency control function for generating a reference frequency that needs a fixed period for a single correction, and maximum correction width setting parts 7 and 7A for repeatedly setting a maximum correction width in the oscillator having a frequency control function for a frequency error when the frequency error of the reference frequency is larger than the maximum correction width and for setting an odd correction width that is smaller than the maximum correction width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic frequency control system used for digital mobile communication. In particular, the present invention relates to an automatic frequency control system and method for preventing line disconnection by correcting a largely shifted reference frequency and correcting the reference frequency with a shorter convergence time.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a schematic configuration of a portable telephone device on which the present invention is based. Note that the same components are denoted by the same reference numerals and symbols throughout the drawings and will be described. As shown in the figure, a control unit 8 is provided in the mobile phone device, and the control unit 8 is configured by a CPU (Central Processing Unit) or hardware, and performs all control of the mobile phone device.

[0003] Furthermore, a common unit 1 is provided in the portable telephone device, and the common unit 1 prevents transmission / reception interference of the transmission / reception shared antenna. The common unit 1 is connected to both the receiving unit 2 and the transmitting unit 4. The receiving unit 2 receives a signal of a carrier frequency on a wireless channel transmitted from a base station (not shown) via the sharing unit 1.

[0004] The transmission unit 4 transmits a signal of a carrier frequency on a radio channel to the base station via the common unit 1. Further, both the reception unit 2 and the transmission unit 4 include a frequency generation unit 3
The frequency generator 3 generates a frequency of a radio channel band with a precision equal to the frequency precision of the reference frequency by a PLL (Phase Lock Loop), and transmits a signal of the frequency of the radio frequency band to the receiver 2 and the transmitter 4. The receiver 2 replaces the carrier frequency signal on the radio channel received from the base station with an intermediate frequency signal, and the transmitter 4 converts the modulated signal into a carrier frequency signal on the radio channel.

[0005] A TCXO (oscillator with frequency control function) 6 is connected to the frequency generator 3, and the TCXO 6 supplies a reference frequency to the frequency generator 3. A demodulation unit 5 is connected to the reception unit 2, and the demodulation unit 5 demodulates the intermediate frequency signal supplied from the reception unit 2 into an audio signal. The modulation unit 9 is connected to the transmission unit 4, and the modulation unit 9 outputs a modulation signal to the transmission unit 4.

A transmitter / receiver 10 is connected to the controller 8, and the transmitter / receiver 10 converts the input audio information into an audio signal, and outputs the audio signal to the modulator 9 via the controller 8 to perform digital modulation.
Furthermore, the audio signal demodulated by the demodulation unit 5 is input via the control unit 8 and converted into audio information and output. further,
The output side of the receiving unit 2 has an AFC unit (Automatic
Frequency control (automatic frequency control) 7 is provided, and the AFC unit 7 receives an intermediate frequency signal from the receiving unit 2, further receives a reference frequency signal from the TCXO 6, compares the intermediate frequency with an expected value, and determines a deviation of the reference frequency. Calculate and pass the calculated result to the control unit 8
, The control voltage of the TCXO 6 is controlled in such a direction as to cancel the deviation amount with respect to the TCXO 6 to maintain the frequency accuracy of the reference frequency.

Here, the reason why the AFC section 7 is provided will be described below. In digital mobile communication systems,
Since the receiving station cannot receive the signal even if the frequency slightly deviates, the reference frequency of the digital portable telephone device needs to have extremely high frequency accuracy with respect to temperature change and the like. On the other hand, having a high-precision reference frequency oscillator in the mobile phone device itself is disadvantageous in terms of miniaturization and weight reduction.

[0008] For this reason, in order to secure high frequency accuracy, a digital mobile phone device uses frequency accuracy,
AFC control is performed in order to match the reference frequency of the base station whose stability is extremely high. FIG. 7 is a flowchart for explaining the operation of the conventional AFC unit 7 in FIG.

In step S101, when the portable telephone device is turned on, the operation of the flow starts. In step S102, control of the AFC unit 7 is started next,
Calculate the frequency error (the deviation of the reference frequency). In this calculation, a reference frequency is input from the TCXO 6 to create a window of a fixed time, and the number of intermediate frequencies input from the receiver 2 is counted in the window. The deviation of the reference frequency is calculated by comparing the counted result with the expected value.

When the AFC unit 7 is completed in step S103, the completed frequency correction value is set in the TCXO 6. In this setting, the calculated result is passed to the control unit 8,
The setting of the TCXO 6 is performed from the control unit 8. TCXO6
In this case, the control voltage is controlled in a direction to cancel the deviation amount of the reference frequency, and the frequency accuracy of the reference frequency is maintained.

In step S104, the process ends. After the processing is completed, step S101 is performed again.
And the flow control of the AFC unit 7 is performed, and the operation is always continued until the power of the mobile phone device is turned off. In this way, it is possible to match the frequency accuracy of the wireless channel band.

Regarding the above-mentioned conventional AFC unit 7,
For example, Japanese Patent Application No. 11-273899, Japanese Patent Application No. 2000-
193934.

[0013]

However, since the result of ending the AFC calculation and determining the deviation amount of the reference frequency is set in the TCXO 6 as it is in the AFC unit 7 of the portable telephone device, For example, when the deviation amount is large, the frequency fluctuates greatly. As a result, there is a problem that the line may be disconnected by performing the AFC control even though the signal has been received up to now.

[0014] The cause of the line disconnection may be that the portable telephone device becomes unable to transmit or receive, but here, the case where the reception becomes impossible and the line is disconnected will be described below. . FIG. 8 is a diagram illustrating a state in which communication with a base station cannot be performed due to a line disconnection. This figure shows an IQ plan view in the case where the phase difference is calculated for a signal obtained by dividing the intermediate frequency into 36 equal parts (9 equal parts in one quadrant) by differential detection.

In addition, PDC (Personal Dig)
Since the symbol rate is 21 KHz in the italian cell, the frequency of one section when divided into 36 equals is 21 KHz / 36 ≒ about 583.3 Hz. As shown in FIG. 8, when the delay detection circuit is configured to divide the intermediate frequency into 36 equal parts, demodulation is possible in principle within a range not exceeding the quadrant. For example, 0 to 8 in FIG.
Is calculated, the demodulated data can be demodulated as -π / 4.

However, when this quadrant is exceeded, for example,
Now, if there is a shift of the intermediate frequency such that the phase shifts to the phase of 9 when the point is 4 in FIG. 8, the demodulation cannot be performed because it crosses the quadrant. In other words,
When the control of the AFC unit 7 is performed, the reception may not be possible if the frequency is corrected so as to cross the quadrant.

In a specific example, the deviation of the intermediate frequency when the signal is pulled in from 9 to 4 is 583.3 Hz × (9−4).
4) と な り 2917 Hz, and the intermediate frequency is 281
If a reference frequency pull-in operation that shifts by 7 Hz or more is performed, the line may be disconnected, and communication with the base station cannot be performed. That is, the calculation in the AFC unit 7 is terminated, and the result of the determination of the deviation amount of the reference frequency is directly used as T
Since the value is set to CXO6, when the deviation amount of the reference frequency is large, the reference frequency largely varies. As a result, although it was possible to receive
By controlling the C unit 7, the line may be disconnected.

As a solution to this, it is conceivable to apply a correction to the TCXO 6 at a time, rather than to the TCXO 6 at a time, on the result calculated by the AFC unit 7, but the reference frequency converges. Is not a good solution because it takes time. Accordingly, the present invention has been made in view of the above-described problems. Therefore, even when the reference frequency is largely deviated, without extending the convergence time of the reference frequency, the line is not cut, and the automatic frequency that enables communication with the base station is provided. It is an object to provide a control system and method.

[0019]

According to the present invention, there is provided an automatic frequency control system for controlling the correction of a reference frequency supplied to a PLL. Oscillator with a frequency control function to be generated, if the frequency error of the reference frequency is larger than the maximum correction width, the oscillator with the frequency control function, by the frequency error, repeatedly set the maximum correction width, Further, the present invention provides an automatic frequency control system including a maximum correction width setting unit that sets a remaining correction width smaller than the maximum correction width.

Preferably, the maximum correction width setting section divides the frequency error by the maximum correction width, obtains a quotient and a remainder, sets the quotient as the number of corrections, and supplies the maximum correction width to the oscillator with frequency control function. Are sequentially set for the number of corrections, and finally, the remaining correction width is set. By this means, the reference frequency is corrected repeatedly with the maximum correction width, so that even if the reference frequency is largely deviated, the line is not cut without extending the convergence time of the reference frequency and communication with the base station is performed. enable.

Preferably, the maximum correction width setting section sets the frequency error in the oscillator with a frequency control function at once immediately after power-on even when the frequency error of the reference frequency is larger than the maximum correction width. I do. By this means, the convergence time of the reference frequency is advanced so that the communication with the base station can be performed quickly immediately after the power is turned on.

Preferably, the maximum correction width setting section reviews the number of repetitions of correction while following the fluctuation of the reference frequency even while the oscillator with the frequency control device is performing the operation of pulling in the reference frequency. By this means, when the reference frequency fluctuates while the reference frequency is being pulled in, it is possible to review the number of corrections following the fluctuation.

Preferably, the maximum correction width is large enough not to affect reception characteristics, and is stored in a nonvolatile memory. By this means, even when the accuracy of the demodulator of the mobile phone device or the oscillator with the frequency control device changes, the maximum correction width, which is a parameter, can be stored in the nonvolatile memory, and a stable correction width can be obtained. Can,
And a flexible response becomes possible.

Further, according to the present invention, there is provided an automatic frequency control correction method for performing correction control of a reference frequency supplied to a PLL, wherein the step of generating the reference frequency requiring a fixed time for one time correction includes: Is larger than the maximum correction width, the frequency error is divided by the maximum correction width and the number of corrections for correcting the reference frequency with the maximum correction width, and the remaining correction width smaller than the maximum correction width are obtained. And an automatic frequency control correction method.

By this means, the reference frequency is corrected by repeating with the maximum correction width in the same manner as in the above invention. Therefore, even when the reference frequency is largely shifted, the line can be connected without increasing the convergence time of the reference frequency. Enables communication with the base station without interruption.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a mobile phone device according to the present invention. As shown in FIG. 6, as compared with FIG. 6, the AFC unit 7 has a maximum correction width setting unit 7A and a nonvolatile memory 7B which are characteristic parts of the present invention.
Is provided.

FIG. 2 is a flowchart for explaining the operation of the maximum correction width setting section 7A of the AFC section 7 in FIG.
In step S201, when an AFC operation instruction is issued from the control unit 8, the flow of the present invention starts. In step S202, the AFC unit 7 calculates an error amount of the reference frequency from the relationship between the reference frequency and the intermediate frequency.

In step S203, the maximum error width setting unit 7A of the AFC unit 7 sets the frequency error (δ).
Is larger than the maximum correction width (MAX). In step S204, if it is smaller, TCX
A correction value is set in O6.

In step S205, the AFC unit 7,
The processing of the maximum correction width setting unit 7A is stopped. Step S2
In 06, when it is determined that δ> MAX, δ is divided as follows. That is, the calculation of the frequency error (δ) / the maximum correction width (MAX) is performed, and the quotient m is obtained as the number of corrections m. The remainder (n) of δ / MAX is similarly obtained.

In step S207, the maximum correction width setting unit 7A sets the maximum correction width (MAX) to the value of the TCXO m times.
The voltage of 6 is corrected. In step S208, the voltage of the TCXO 6 is finally corrected using the value of the remaining correction width n, and the process proceeds to step S205. FIG. 3 is a diagram illustrating a specific example of the setting of the correction width by the maximum correction width setting unit 7A.

As shown in the figure, 00h (0d) to FF
The 8-bit image of h (255d) represents the correction range of TCXO6, for example, 80h (128d)
Indicates a value when there is no error in the reference frequency. As a result of calculating the frequency error (δ) in the AFC unit 7,
52h (82d) at one time, as in the conventional technology common unit 1
When it is necessary to pull in from the time to 80h (128d), the current value 52h (82d)
The distance up to the convergence target of 80h (128d) is calculated.

That is, δ = 80h (128d) −52h (82d) = 46d is calculated. On the other hand, in the present invention, δ is divided as follows. That is, for example, assuming that the maximum correction width is 10d, in the maximum correction width setting unit 7A, 46d becomes 10d
The correction value is determined to be larger than the maximum value, and the correction value is divided by the maximum correction width.

46d / 10d = 4, and the remainder is 6. Here, the calculated quotient 4 indicates the number of times the TCXO 6 is corrected with the maximum correction width, and the remainder indicates the remaining correction width. In the example of FIG. 3, the convergence is achieved by five corrections. Next, in the example of FIG. 3, the time required for one correction of the TCXO 6 is set to td, and the time T required until the reference frequency converges is obtained.

T = td × (4 + 1) = 5td Here, the values of (4) and (1) in parentheses indicate that four corrections are required with the maximum correction width, and that the remainder requires one correction with the remaining correction width of five, for a total of five corrections. . On the other hand, in the related art 2, when one correction width is “2”, T = td × (23 = 46/2) = 23td, and the convergence time of the reference frequency becomes longer.

As described above, by performing the pull-in operation of the AFC control with the maximum correction width (maximum correction width MAX) which does not affect the reception characteristics, even when the reference frequency is largely shifted, the convergence of the reference frequency is achieved. The reference frequency can be converged with a stable correction width without increasing the time. Since the value of the maximum correction width MAX changes depending on the accuracy of the demodulation unit 5 and the accuracy of the TCXO 6 to be used in the mobile phone, after the mobile phone is developed, the maximum correction width that does not affect the reception characteristics is determined in advance. It is confirmed by an experiment or the like and stored in the nonvolatile memory 7B or the like of the AFC unit 7 in FIG.

Thus, the demodulation unit 5, T
Even when the accuracy of the CXO 6 changes, the maximum correction width, which is a parameter, can be stored in the non-volatile memory 7B, a stable correction width can be obtained, and a flexible response is possible. FIG. 4 is a first modification of FIG. 2, and is a flowchart illustrating the operation of the maximum correction width setting unit 7A of the AFC unit 7.

As shown in this figure, as compared with FIG. 2, in step S303, a process for determining whether or not the portable telephone device has just been turned on is included. The reference frequency of the mobile phone immediately after the power is turned on may be largely shifted because it has not communicated with the base station, and communication cannot be performed unless AFC control is performed and the reference frequency is adjusted. There is a risk.

Therefore, immediately after the power is turned on, the AFC
It is required that the convergence time in the unit 7 be as short as possible,
In step S303, when it is determined that the power supply has just been turned on, the frequency error δ calculated by the AFC unit 7 is directly set in the TCXO 6, and the convergence time of the reference frequency is shortened. Make communication possible.

FIG. 5 shows a second modification of FIG.
9 is a flowchart illustrating an operation of a maximum correction width setting unit 7A of the C unit 7. As shown in this figure, compared to FIG.
This is a point that a process for determining whether or not the number of corrections m is greater than zero in step S409 is included. Step S40
In step 9, when it is determined that m> 0, the process returns to step S402, and the AFC unit 7 calculates the frequency error again.

Thus, the fluctuation of the reference frequency is monitored even during the operation of pulling in the reference frequency. The fluctuation of the reference frequency is monitored by the number of corrections m. If the reference frequency fluctuates while the reference frequency is being pulled in, the number of corrections can be reviewed according to the fluctuation.

[0041]

As described above, according to the present invention,
Generates a reference frequency that requires a fixed time for a single correction, and if the frequency error of the reference frequency is larger than the maximum correction width, divides the frequency error by the maximum correction width and corrects the reference frequency with the maximum correction width Since the number of times and the remaining correction width smaller than the maximum correction width are obtained, the reference frequency is corrected by repeating the maximum correction width, so that even when the reference frequency is largely shifted, the convergence time of the reference frequency can be reduced. Without lengthening, the line is not cut off and communication with the base station is enabled.

Further, since the maximum correction width setting section sets the frequency error in the oscillator with the frequency control function at once immediately after the power is turned on even when the frequency error of the reference frequency is larger than the maximum correction width. By shortening the convergence time of the reference frequency, it is possible to quickly communicate with the base station immediately after the power is turned on. Furthermore, the maximum correction width setting unit is configured to re-check the number of repetitions of the correction while following the fluctuation of the reference frequency even while the oscillator with the frequency control device is performing the pull-in operation of the reference frequency. If the reference frequency fluctuates while
The number of corrections can be reviewed according to the fluctuation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a mobile phone device according to the present invention.

FIG. 2 is a flowchart illustrating an operation of a maximum correction width setting unit 7A of the AFC unit 7 in FIG.

FIG. 3 is a diagram illustrating a specific example of setting a correction width by a maximum correction width setting unit 7A.

FIG. 4 is a first modification example of FIG. 2, and is a flowchart illustrating an operation of a maximum correction width setting unit 7A of the AFC unit 7;

FIG. 5 is a flow chart illustrating an operation of a maximum correction width setting unit 7A of the AFC unit 7 according to a second modification of FIG.

FIG. 6 is a block diagram showing a schematic configuration of a mobile phone device as a premise of the present invention.

FIG. 7 is a flowchart for explaining the operation of the conventional AFC unit 7 in FIG. 6;

FIG. 8 is a diagram for explaining a state where communication with a base station becomes impossible due to a line disconnection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Common part 2 ... Receiving part 3 ... Frequency generation part 4 ... Transmission part 5 ... Demodulation part 6 ... TCXO 7 ... AFC part 7A ... Maximum correction width setting part 7B ... Non-volatile memory 8 ... Control part 9 ... Modulation part 10 ... Handset

Claims (6)

[Claims] An automatic frequency control system for performing correction control of a reference frequency supplied to a PLL, comprising: an oscillator with a frequency control function for generating the reference frequency requiring a fixed time for one correction; In the case where the maximum correction width is larger than the maximum correction width, the maximum correction width is repeatedly set in the oscillator with a frequency control function by the frequency error, and further, a correction width smaller than the maximum correction width is set. An automatic frequency control system comprising a width setting unit. 2. The maximum correction width setting unit divides the frequency error by the maximum correction width, obtains a quotient and a remainder, sets the quotient as the number of corrections, and sets the maximum correction width in the oscillator with a frequency control function. 2. The automatic frequency control system according to claim 1, wherein the number of corrections is sequentially set, and the remaining correction width is finally set. 3. The maximum correction width setting unit sets the frequency error in the oscillator with a frequency control function at once immediately after power is turned on, even when the frequency error of the reference frequency is larger than the maximum correction width. 2. The automatic frequency control system according to claim 1, wherein: 4. The maximum correction width setting unit, while the oscillator with a frequency control device is performing a pull-in operation of the reference frequency, reviews the number of repetitions of correction by following a change in the reference frequency. The automatic frequency control system according to claim 1, wherein: 5. The automatic frequency control system according to claim 1, wherein the maximum correction width has a size that does not affect reception characteristics and is stored in a nonvolatile memory. 6. An automatic frequency control correction method for performing correction control of a reference frequency supplied to a PLL, comprising: a step of generating the reference frequency requiring a fixed time for one time correction; If the difference is larger than the maximum correction width, the frequency error is divided by the maximum correction width, and the reference frequency is corrected by the maximum correction width, and a correction width smaller than the maximum correction width is obtained. An automatic frequency control correction method, characterized in that: