JP2008066906A - Frequency correction system and its method, and radio communication equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent frequency tracking characteristics while maintaining frequency correction accuracy same as that in a normal temperature in a high temperature or a large frequency error when correcting the frequency of the oscillation frequency of a crystal oscillator. <P>SOLUTION: When a detected temperature is a temperature (normal temperature) lower than a threshold T, a frequency correction shift width is set to F(ppm) and a frequency correction time interval is set to t1. When the detected temperature reaches the threshold T (high temperature), the frequency correction shift width is not changed and is set to F(ppm) and the frequency correction time interval is set to t2 (t1>t2). At the high temperature, a frequency correction operation is accelerated and a frequency tracking speed is increased. At the time, by maintaining the frequency correction shift width as F(ppm) in the normal temperature, the degradation of the frequency correction accuracy is suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a frequency correction system and method and a radio communication apparatus using the same, and more particularly to a method for correcting an oscillation frequency of a crystal resonator used in the radio communication apparatus.

  A crystal resonator is used in a radio communication terminal including a mobile phone, and a high-frequency signal transmitted from a communication partner radio communication device such as a radio base station is generated using an oscillation output generated by the crystal resonator. Reception and transmission of a high-frequency signal to be transmitted to the communication partner radio communication apparatus are enabled. In general, since the oscillation frequency of an oscillation circuit using a crystal resonator is easily affected by a temperature change, the wireless communication terminal is provided with an AFC circuit that is a temperature compensation circuit, and crystal oscillation caused by a temperature rise. The frequency error of the child is corrected.

  Here, the frequency correction function in the mobile phone will be described. In frequency correction with a conventional mobile phone, frequency correction operation is performed at regular time intervals regardless of temperature conditions, and at high temperatures when the frequency error fluctuates, the frequency correction shift width is changed accordingly. The frequency tracking speed is accelerated.

  Now, let the time interval of frequency correction operation be every t (msec), and the shift width of frequency correction at room temperature of 25 ° C. be F (ppm). Then, when the temperature is high at 50 ° C., it is necessary to set the follow-up speed of frequency correction five times that at the normal temperature of 25 ° C. Then, when the temperature is high at 50 ° C., the frequency correction shift width needs to be five times that at the normal temperature of 25 ° C. The frequency correction time interval at this time is t (msec) as in the normal temperature of 25 ° C. as described above. FIG. 5 shows the setting parameters for the frequency correction operation in this conventional example in comparison at normal temperature (25 ° C.) and high temperature (50 ° C.).

  The frequency follow-up speed at high temperature is 5 F / t (ppm / msec), which is five times higher than that at normal temperature (F / t (ppm / msec)). Since it becomes the same as the shift width, it is within 5F (ppm), and the accuracy of frequency correction is degraded as compared with the room temperature at 25 ° C.

Here, referring to Patent Document 1, when the temperature change is abrupt, the time interval of the temperature correction operation is reduced, and conversely, when the temperature change is gentle, the time interval of the temperature correction operation is increased. Is disclosed.
JP 2003008348 A

  In the prior art as shown in FIG. 5, at high temperatures, the frequency follow-up speed is increased by increasing only the frequency correction shift width while maintaining the frequency correction operation time interval at room temperature. Therefore, there is a drawback that the correction accuracy of the frequency correction is deteriorated at a high temperature as compared with a normal temperature.

  In the technique of Patent Document 1, the time interval of the frequency correction operation is changed according to the temperature change regardless of the low temperature or the high temperature, and the frequency correction shift width at the high temperature or the normal temperature. Is not considered at all. Therefore, there is no guarantee that the frequency correction accuracy is kept the same at normal temperature and high temperature.

  An object of the present invention is to provide a frequency correction circuit and method for enabling frequency tracking while maintaining the same frequency correction accuracy as that at room temperature when the temperature is high or when the frequency error is large.

  The frequency correction system according to the present invention is a frequency correction system for correcting the oscillation frequency of the crystal resonator, and the time interval of the frequency correction operation is variably controlled according to the temperature while keeping the frequency correction shift width constant. It is characterized by including the means to do.

  Another frequency correction system according to the present invention is a frequency correction system for correcting the oscillation frequency of a crystal resonator, and the frequency interval of the frequency correction operation is kept constant while maintaining the frequency correction shift width constant. It is characterized by including means for variably controlling in response.

  A wireless communication apparatus according to the present invention is characterized by using the frequency correction system described above.

  The frequency correction method according to the present invention is a frequency correction method for correcting the oscillation frequency of the crystal resonator, and the time interval of the frequency correction operation is variably controlled according to the temperature while keeping the frequency correction shift width constant. Including the step of:

  Another frequency correction method according to the present invention is a frequency correction method for correcting the oscillation frequency of a crystal resonator, and the frequency interval of the frequency correction operation is kept constant while maintaining the frequency correction shift width constant. The method includes a step of variably controlling in response.

  A program according to the present invention is a program for causing a computer to execute a frequency correction method for correcting the oscillation frequency of a crystal resonator, while maintaining a frequency correction operation time interval with a constant frequency correction shift width. It includes a process of variably controlling according to temperature.

  Another program according to the present invention is a program for causing a computer to execute a frequency correction method for correcting the oscillation frequency of a crystal resonator, maintaining a frequency correction operation time interval and a frequency correction shift width constant. However, it is characterized by including a process of variably controlling according to the oscillation frequency error.

  According to the present invention, the frequency follow-up speed can be reduced by setting the frequency correction operation time interval smaller while maintaining the same frequency correction shift width at a high temperature or when the frequency error is large. As well as accelerating, the frequency correction accuracy is the same as that at room temperature, and it is possible to prevent deterioration.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram of an embodiment of the present invention, in which the frequency correction circuit of the present invention is applied to a mobile phone. The block diagram of FIG. 1 is the same as the conventional example, but the operation of the frequency correction circuit is different, and the operation is shown in the flowchart of FIG.

  Referring to FIG. 1, a mobile phone to which the present invention is applied includes a radio reception unit 1, a crystal resonator 2, a reception baseband unit 3, a frequency error detection unit 4, and a frequency correction circuit (AFC circuit) 5. And a temperature sensor 6, a transmission baseband unit 7, and a wireless transmission unit 8.

  The radio reception unit 1 receives a reception signal transmitted from a radio base station (not shown). This reception signal is a high-frequency signal, and reception processing is performed using an oscillation output supplied from the crystal resonator 2. To the reception baseband unit 3 and the frequency error detection unit 4. The crystal resonator 2 supplies an oscillation output to the wireless reception unit 1 and the wireless transmission unit 8. In addition, the crystal resonator 2 can correct the frequency error under the control of the frequency correction circuit 5.

  The reception baseband unit 3 performs baseband processing on the signal received by the wireless reception unit 1. The frequency error detection unit 4 measures the frequency error of the crystal resonator 2 from the signal received by the wireless reception unit 1 and reports the measurement result to the frequency correction circuit 5, and has a known frequency counter configuration. is there. The frequency correction circuit 5 controls the crystal resonator 2 based on the frequency error information reported from the frequency error detection unit 4 and the temperature information reported from the temperature sensor 6 to correct the frequency error. The AFC circuit performs a control operation according to a control algorithm based on the flowchart shown in FIG.

  The transmission baseband unit 7 generates a baseband signal to be transmitted to the radio base station. The wireless transmission unit 8 converts the information received from the transmission baseband unit 7 using the oscillation signal supplied from the crystal unit 2 into a high frequency signal and transmits it to the wireless base station. The temperature sensor 6 is mounted near the crystal unit 2 on the circuit board inside the mobile phone, monitors the ambient temperature of the crystal unit 2, and notifies the frequency correction circuit 5.

  The above has shown the configuration of the part related to the frequency correction function of a general mobile phone, but this configuration is generally known and will not be described in detail. As described above, the present invention is characterized by the correction control algorithm of the frequency correction circuit 5, and FIG. 2 shows a flowchart of the control operation.

  In this embodiment, the frequency follow-up speed is accelerated by setting the time interval of the frequency correction operation to be shorter at a high temperature when the fluctuation of the frequency error is larger than at a normal temperature, but the frequency shift width at that time is Set to the same frequency correction shift width at room temperature. That is, at a high temperature of 50 ° C., for example, the time interval of the frequency correction operation is set to 1/5 compared to that at a normal temperature of 25 ° C., and the shift width of the frequency correction is set to F (ppm) as in the normal temperature of 25 ° C. . Therefore, the frequency tracking speed is 5 F / T (ppm / msec), and a frequency error tracking speed of 5 times that at room temperature can be obtained. Thus, no deterioration occurs. FIG. 3 shows setting parameters for the frequency correction operation in this case.

  The operation of the embodiment of the present invention will be described in detail using the flowchart of FIG. Temperature measurement is performed by the temperature sensor 6 (step S1), and the frequency correction circuit 5 is notified. In the frequency correction circuit 5, the threshold temperature T (for example, 50 ° C.) is compared with the measured temperature (step S2). If the measured temperature is lower than T, the frequency correction shift width is set to F (ppm), and the next time The frequency correction operation is set to be after t1 (msec) (step S3). Then, frequency correction is executed with the set parameters (step S4). Thereafter, the next frequency correction processing is waited (step S5). At this time, the timer starts counting, and the next frequency correction processing is performed after t1 (msec) elapses.

  In step S2, when the measured temperature reaches T (becomes T or more), the next frequency correction operation is set after t2 (msec) with the frequency shift width being F (ppm) (step S6). ). It is assumed that t1> t2. Then, frequency correction is executed with the set parameters (step S7). Thereafter, the next frequency correction processing is waited (step S8). At this time, the timer starts counting, and after the elapse of t2 (msec), the next frequency correction process is performed.

  Next, another embodiment of the present invention will be described. The functional block of the mobile phone in this embodiment is the same as that of the previous embodiment shown in FIG. The difference from the previous embodiment is the frequency correction control algorithm of the frequency correction circuit 5, and the operation of the control algorithm is shown in the flowchart of FIG. In the flowchart of FIG. 4, steps equivalent to those in FIG. 2 are denoted by the same reference numerals.

  Referring to FIG. 4, first, frequency error detection is performed by the frequency error detector 4 (step S11). This frequency error is notified to the frequency correction circuit 5, and the frequency correction circuit 5 compares the threshold value A with the frequency error (step S12). If the frequency error is smaller than A, the process proceeds to step 3, and the frequency error When A reaches A (becomes A or more), the process proceeds to step S6.

  In the process of step S3, the correction shift width is set to F (ppm), and the next frequency correction operation is set to be after t1 (msec). That is, if the frequency error is smaller than the threshold value A, the same parameters (F and t1) as normal temperature are set. In the process of step S6, the correction shift width is set to F (ppm), and the next frequency correction operation is set to be after t2 (msec) (note that t1> t2). The operations in steps S3 to S5 and the operations in steps S6 to S8 are the same as the operations shown in FIG. 2 in the previous embodiment.

  In this embodiment, since the parameter is set using the frequency error instead of the temperature, it is needless to say that the temperature sensor of FIG. 1 can be omitted.

  As described above, in each embodiment of the present invention, since the time interval (cycle) of the frequency correction operation is made variable while keeping the frequency shift width F constant, the temperature rises and the frequency error is reduced. Even if the fluctuation increases, the frequency correction accuracy does not deteriorate. In addition, under the condition that the frequency error becomes large, the time interval of the frequency correction operation is shortened, so that stable frequency tracking characteristics can be obtained. Furthermore, since the embodiment of the present invention can be realized without changing the hardware of the conventional mobile phone, the performance of the mobile phone can be easily improved.

  Furthermore, since the accuracy of the frequency correction operation is improved, sufficient characteristics can be obtained even with an inexpensive crystal unit that causes a large variation in frequency error due to temperature, contributing to cost reduction. It will be. Further, when the temperature is normal temperature and the frequency error is small, the frequency correction operation interval is increased, so that the frequency of the frequency correction (AFC) circuit is reduced and the current consumption of the mobile phone can be reduced.

  In each of the above embodiments, the case where the present invention is applied to a mobile phone has been described. However, the present invention is not limited to this, and it is obvious that the present invention can be widely applied to wireless communication devices including a wireless communication terminal. The operation flow shown in FIGS. 2 and 4 can be configured such that the operation procedure is stored in advance in a recording medium such as a ROM as a program and can be read and executed by a computer (CPU). .

  In each of the above embodiments, the temperature and frequency error are compared with one threshold value T and A, and the frequency correction time interval is changed in two stages. Obviously, the frequency correction time interval can be set in a plurality of stages.

It is a functional block diagram of the Example of this invention. It is a flowchart which shows operation | movement of one embodiment of this invention. It is a figure which shows the example of the setting parameter of the frequency correction operation | movement of this invention. It is a flowchart which shows the operation | movement of other embodiment of this invention. It is a figure which shows the example of the setting parameter of the frequency correction operation | movement in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radio reception part 2 Crystal oscillator 3 Reception baseband part 4 Frequency error detection part 5 Frequency correction (AFC) circuit 6 Temperature sensor 7 Transmission baseband part 8 Wireless transmission part

Claims (11)

A frequency correction system for correcting the oscillation frequency of a crystal unit,
A frequency correction system comprising means for variably controlling the time interval of the frequency correction operation according to temperature while maintaining a constant frequency correction shift width.   The means is characterized in that the time interval of the frequency correction operation is set to a predetermined value when the temperature is lower than a predetermined threshold, and is set to a value smaller than the predetermined value when the temperature is equal to or higher than the predetermined threshold. The frequency correction system according to claim 1. A frequency correction system for correcting the oscillation frequency of a crystal unit,
A frequency correction system comprising means for variably controlling the time interval of the frequency correction operation according to an oscillation frequency error while maintaining a constant frequency correction shift width.   The means sets the time interval of the frequency correction operation to a predetermined value when the frequency error is lower than a predetermined threshold, and to a value smaller than the predetermined value when the frequency error is equal to or higher than the predetermined threshold. The frequency correction system according to claim 3.   A radio communication apparatus using the frequency correction system according to claim 1. A frequency correction method for correcting the oscillation frequency of a crystal resonator,
A frequency correction method comprising the step of variably controlling the time interval of the frequency correction operation according to temperature while maintaining a constant frequency correction shift width.   The step is characterized in that a time interval of the frequency correction operation is set to a predetermined value when the temperature is lower than a predetermined threshold, and is set to a value smaller than the predetermined value when the temperature is equal to or higher than the predetermined threshold. The frequency correction method according to claim 6. A frequency correction method for correcting the oscillation frequency of a crystal resonator,
A frequency correction method comprising a step of variably controlling a time interval of a frequency correction operation according to an oscillation frequency error while maintaining a constant frequency correction shift width.   In the step, the time interval of the frequency correction operation is set to a predetermined value when the frequency error is lower than a predetermined threshold, and is set to a value smaller than the predetermined value when the frequency error is equal to or higher than the predetermined threshold. The frequency correction method according to claim 8. A program for causing a computer to execute a frequency correction method for correcting the oscillation frequency of a crystal resonator,
A program comprising a process of variably controlling a time interval of a frequency correction operation according to a temperature while maintaining a constant frequency correction shift width. A program for causing a computer to execute a frequency correction method for correcting the oscillation frequency of a crystal resonator,
A program comprising a process of variably controlling a time interval of a frequency correction operation according to an oscillation frequency error while maintaining a constant frequency correction shift width.

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