Method of compensating for the frequency error of system clock in mobile communication terminal with digitally controlled crystal oscillator and mobile communication terminal thereof

• US 20070092035A1
• Filed: 10/19/2006
• Published: 04/26/2007
• Est. Priority Date: 10/26/2005
• Status: Abandoned Application

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Kim, Chang
• Application Number:
  US11/583,042
• Publication Number:
  US 20070092035A1
• Time in Patent Office: Days
• US Class Current: 375/296
• CPC Class Codes: H04B 1/3888 Arrangements for carrying or protecting transceivers

Abstract

A method of compensating a frequency error of a system clock, comprising: detecting an ambient temperature, providing the frequency compensation value for compensating the frequency error of the system clock which is generated in a digitally controlled crystal oscillator on the basis of the detected ambient temperature, and controlling the frequency error of the system clock generated in the digitally controlled crystal oscillator to compensate for the frequency error in accordance with the frequency compensation value.

Claims

1. A mobile communication terminal, comprising:

A digitally controlled crystal oscillator for generating a system clock;

A sensor for detecting an ambient temperature;

A frequency compensation value provider for providing a frequency compensation value for compensating for a frequency error in the system clock generated in the digitally controlled crystal oscillator on the basis of the ambient temperature detected from the sensor; and

A controller for transmitting a control signal for compensating for a frequency error of a system clock to the digitally controlled crystal oscillator on the basis of the frequency compensation value provided from the frequency compensation value provider, and for controlling the frequency of the system clock generated from the digitally controlled crystal oscillator.

2. The mobile communication terminal of claim 1, further comprising a memory unit which stores a program for executing a frequency compensation value calculation function to calculate the frequency compensation value, wherein the frequency compensation value provider calculates the frequency compensation value of the system clock using the program when an ambient temperature is input from the sensor.

3. The mobile communication terminal of claim 2, wherein the program calculates the frequency compensation value using a Taylor series as described below:

$f<br><br>\left(\mathrm{freq}\right)=f<br><br>\left(a\right)+f^{\mathrm{\prime <br><br>}}<br><br>\left(a\right)<br><br>\left(T-a\right)+\left(\frac{f^2<br><br>\left(a\right)}{2!}\right)<br><br>{\left(T-a\right)}^2+\left(\frac{f^3<br><br>\left(a\right)}{3!}\right)<br><br>{\left(T-a\right)}^3+\mathrm{\dots <br><br>}+\left(\frac{f^n<br><br>\left(a\right)}{n!}\right)<br><br>{\left(T-a\right)}^n+\mathrm{\dots <br><br>}$

Wherein the f(freq) is a frequency compensation value, “

T”

is an ambient temperature detected by a temperature sensor, and “

a”

is a coefficient according to a characteristic of a DCXO.

4. The mobile communication terminal of claim 1, further comprising a memory unit which stores an ambient temperature and a frequency compensation value of a system clock respectively corresponding to the ambient temperature in the form of a look up table, wherein the frequency compensation value provider reads a frequency compensation value of the system clock corresponding to the ambient temperature by searching the look up table when an ambient temperature is input from the sensor, and outputs the frequency compensation value to controller.

5. The mobile communication terminal of claim 1, further comprising a memory unit which stores a difference between an ambient temperature and predetermined reference temperature, and a frequency compensation value of a system clock respectively corresponding to the difference in the form of a look up table, wherein the frequency compensation value provider calculates a difference between an ambient temperature and a predetermined reference temperature, reads the frequency compensation value of the system clock corresponding to the difference by searching the lookup table, and outputs the frequency compensation value to the controller.

6. The mobile communication terminal of claim 1, further comprising an A/D converter which converts a temperature detected from the sensor to a digital value and provides the digital value to the frequency compensation value provider.

7. A method of compensating a frequency error of a system clock, comprising:

Detecting an ambient temperature;

Providing the frequency compensation value for compensating the frequency error of the system clock which is generated in a digitally controlled crystal oscillator on the basis of the detected ambient temperature; and

Controlling the frequency error of the system clock generated in the digitally controlled crystal oscillator to compensate for the frequency error in accordance with the frequency compensation value.

8. The method of claim 7, further comprising the step of storing a program for executing the frequency compensation value calculation function to calculate the frequency compensation value of the system clock corresponding to the ambient temperature, wherein the frequency compensation value of the system clock is calculated using the program when the ambient temperature is input.

9. The method of claim 8, wherein the program calculates a frequency compensation value using a Taylor series as described below:

$f<br><br>\left(\mathrm{freq}\right)=f<br><br>\left(a\right)+f^{\mathrm{\prime <br><br>}}<br><br>\left(a\right)<br><br>\left(T-a\right)+\left(\frac{f^2<br><br>\left(a\right)}{2!}\right)<br><br>{\left(T-a\right)}^2+\left(\frac{f^3<br><br>\left(a\right)}{3!}\right)<br><br>{\left(T-a\right)}^3+\mathrm{\dots <br><br>}+\left(\frac{f^n<br><br>\left(a\right)}{n!}\right)<br><br>{\left(T-a\right)}^n+\mathrm{\dots <br><br>}$

Wherein the f(freq) is a frequency compensation value, “

T”

is an ambient temperature detected by a temperature sensor, and “

a”

is a coefficient according to a characteristic of a DCXO.

10. The method of claim 7, further comprising the step of storing the ambient temperature and the frequency compensation value of the system clock respectively corresponding to the ambient temperature in the form of lookup table, wherein the frequency compensation value of the system clock corresponding to the ambient temperature is obtained using a lookup table search when the ambient temperature is input.

11. The method of claim 7, further comprising the step of storing a difference between an ambient temperature and a predetermined reference temperature and the frequency compensation value of the system clock respectively corresponding to the difference in the form of a lookup table, wherein the difference between the ambient temperature and the predetermined reference temperature is calculated when the ambient temperature is input, and the frequency compensation value of the system clock corresponding to the difference is obtained using a lookup table search.

12. The method of claim 7, further comprising the step of converting the detected temperature to a digital value.