Mobile communication terminal and method of clibrating frequency in the same

• US 20030211837A1
• Filed: 04/30/2003
• Published: 11/13/2003
• Est. Priority Date: 05/09/2002
• Status: Active Grant

• Current Assignee: Lenovo Innovations Ltd Hong Kong (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Kitatani, Kenichi
• Granted Patent: US 7,072,631 B2
• Time in Patent Office: Days
• US Class Current: 455/192.1
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: H03J 1/0008 using a central processing unit, e.g. a microprocessor digital tuning in general H03J5/0245
• CPC Class Codes: H03J 2200/11 Cellular receiver, e.g. GSM, combined with a GPS receiver

Abstract

A mobile communication terminal includes (a) a first unit for calibrating a frequency, (b) a global positioning system (GPS) module, and (c) a processor which electrically connects the first unit and the global positioning system module to each other. The first unit counts the number of an intermediate frequency (IF) signal generated by converting a frequency of a signal transmitted from a base station, the processor coverts a count of the intermediate signal obtained while the first unit is in lock-up condition, into a real count offset, and the global positioning system module counts the number of a signal transmitted from a circuit which generates an operational frequency of the mobile communication terminal, and calibrates the number of the signal with the real count offset.

Claims

1. A mobile communication terminal including:

(a) a first unit for calibrating a frequency;

(b) a global positioning system (GPS) module; and

(c) a processor which electrically connects said first unit and said global positioning system module to each other,

wherein said first unit counts the number of an intermediate frequency (IF) signal generated by converting a frequency of a signal transmitted from a base station,

said processor coverts a count of said intermediate signal obtained while said first unit is in lock-up condition, into a real count offset, and

said global positioning system module counts the number of a signal transmitted from a circuit which generates an operational frequency of said mobile communication terminal, and calibrates said number of said signal with said real count offset.

2. The mobile communication terminal as set forth in claim 1, wherein said first unit is comprised of:

(a1) a down-converter which converts a frequency of a signal transmitted from a base station, and transmits an intermediate frequency (IF) signal;

(a2) an auto-frequency calibration (AFC) circuit which counts the number of said intermediate signal transmitted from said down-converter;

(a3) a digital-analog converter which converts a voltage transmitted from said auto-frequency calibration circuit, into analog data; and

(a4) a first circuit which generates an operational frequency of said mobile communication terminal, and transmits a frequency signal indicative of said operational frequency.

3. The mobile communication terminal as set forth in claim 2, wherein said processor reads a count of said intermediate frequency signal out of said auto-frequency calibration circuit while said first unit is in lock-up condition, converts the thus read-out count into a real count offset, and outputs said real count offset.

4. The mobile communication terminal as set forth in claim 2, wherein said global positioning system module is comprised of:

(b1) a second circuit which generates an operational frequency of said global positioning system module;

(b2) a counter which counts said frequency signal calibrated by said first unit;

(b3) a real count calibrator which receives a real count transmitted from said counter and a real count offset transmitted from said processor, and calibrates said real count with said real count offset;

(b4) a calculator which calculates a difference between said real count calibrated by said real count calibrator, and an ideal count, and outputs a calibration signal indicative of the thus calculated difference; and

(b5) a GPS signal processor which receives said calibration signal and a signal transmitted from a global positioning system satellite, and processes signals relating to measurement of position.

5. The mobile communication terminal as set forth in claim 4, wherein said real count calibrator adds said real count offset transmitted from said processor, to said real count transmitted from said counter, to thereby calibrate said real count.

6. The mobile communication terminal as set forth in claim 3, wherein said processor estimates an error in said operational frequency of said mobile communication terminal, based on said count of said intermediate frequency signal, calculates offset in said real count transmitted from said auto-frequency calibration circuit, based on said error, and outputs said offset as said real count offset.

7. The mobile communication terminal as set forth in claim 6, wherein said processor reads out said count of said intermediate frequency signal, and converts said count of said intermediate frequency signal into said real count offset in accordance with a conversion table or a conversion equation.

8. The mobile communication terminal as set forth in claim 4, wherein said counter counts both of a rising-up edge and a falling-down edge of a waveform of the received frequency signal.

9. The mobile communication terminal as set forth in claim 4, wherein said calibration signal transmitted from said calculator is fed back to said counter.

10. The mobile communication terminal as set forth in claim 4, wherein said calibration signal transmitted from said calculator is converted into a control voltage in accordance with which a frequency transmitted from said second circuit is calibrated.

11. A method of calibrating a frequency in a mobile communication terminal, comprising the steps of:

(a) counting the number of an intermediate frequency (IF) signal generated by converting a frequency of a signal transmitted from a base station;

(b) converting a count of said intermediate signal obtained while a first unit for calibrating a frequency in said mobile communication terminal is in lock-up condition, into a real count offset; and

(c) counting the number of a frequency signal transmitted from a circuit which generates an operational frequency of said mobile communication terminal, and outputs said frequency signal indicative of said operational frequency, and calibrating said number of said frequency signal with said real count offset.

12. The method as set forth in claim 11, wherein said real count is calibrated by adding said real count offset to said real count in said step (c).

13. The method as set forth in claim 11, wherein said step (b) includes the steps of:

estimating an error in said operational frequency of said mobile communication terminal, based on said count of said intermediate frequency signal;

calculating offset in said real count of said intermediate frequency signal, based on said error; and

outputting said offset as said real count offset.

14. The method as set forth in claim 11, wherein said step (b) includes the steps of:

reading out said count of said intermediate frequency signal; and

converting said count of said intermediate frequency signal into said real count offset in accordance with a conversion table or a conversion equation.

15. The method as set forth in claim 11, wherein both of a rising-up edge and a falling-down edge of a waveform of said frequency signal are counted in said step (c).

16. A program for causing a computer to carry out a method of calibrating a frequency in a mobile communication terminal, processing executed by said computer in accordance with said program including:

(a) counting the number of an intermediate frequency (IF) signal generated by converting a frequency of a signal transmitted from a base station;

(b) converting a count of said intermediate signal obtained while a first unit for calibrating a frequency in said mobile communication terminal is in lock-up condition, into a real count offset; and

(c) counting the number of a frequency signal transmitted from a circuit which generates an operational frequency of said mobile communication terminal, and outputs said frequency signal indicative of said operational frequency, and calibrating said number of said frequency signal with said real count offset.

17. The program as set forth in claim 16, wherein said real count is calibrated by adding said real count offset to said real count in said processing (c).

18. The program as set forth in claim 16, wherein said processing (b) includes:

estimating an error in said operational frequency of said mobile communication terminal, based on said count of said intermediate frequency signal;

calculating offset in said real count of said intermediate frequency signal, based on said error; and

outputting said offset as said real count offset.

19. The program as set forth in claim 16, wherein said processing (b) includes:

reading out said count of said intermediate frequency signal; and

converting said count of said intermediate frequency signal into said real count offset in accordance with a conversion table or a conversion equation.

20. The program as set forth in claim 16, wherein both of a rising-up edge and a falling-down edge of a waveform of said frequency signal are counted in said processing (c).

21. A recording medium readable by a computer, storing a program defined in claim 16.