Method for calibrating the frequency of an RF oscillator in a mobile part of a mobile communications device

• US 7,289,779 B2
• Filed: 08/31/2001
• Issued: 10/30/2007
• Est. Priority Date: 09/20/2000
• Status: Expired due to Fees

• Current Assignee: Gemalto M2M GmbH (Thales SA)
• Original Assignee: Siemens AG
• Inventors: Falkenberg, Andreas, Karger, Stephan, Bienek, Bernd, Kunz, Albrecht, Kreul, Theo, Landenberger, Holger
• Primary Examiner(s): Urban; Edward F.
• Assistant Examiner(s): Nguyen; Tu X.
• Application Number:
  US10/381,014
• Publication Number:
  US 20040043737A1
• Time in Patent Office: 2,251 Days
• Field of Search: 455/75, 455/87, 455/147, 455/150.1, 455/154.1, 455/158.1, 455/161.1, 455/183.1, 455/184.1, 455/196.1, 455/208, 455/265, 375/343, 375/340
• US Class Current: 455/147
• CPC Class Codes: H03J 1/0066 with means for analysing the received signal strength H03J1/0083 takes precedence
• CPC Class Codes: H03J 7/04 where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant

Abstract

A method is provided for calibrating the frequency of an RF oscillator in a mobile part of a mobile communications device when the mobile part is first switched on, wherein the method includes the steps of: sampling a modulated carrier that is transmitted by a base station and has a prescribed frequency accuracy, such that scanning of the modulated carrier is performed via a frequency search algorithm with the modulated carrier being demodulated, a signal thus demodulated being compared in an evaluation and synchronization program via a correlation with a sequence known in advance, and a correlation peak in an output of the correlator being determined; determining a frequency error between the frequency of the RF oscillator in the mobile part of the mobile communications device and a known channel frequency of the base station by comparing the determined correlation peak of the output of the correlator with a channel raster, known in advance to the mobile communications device, of the base station; synchronizing the mobile communications device with the modulated carrier; and adopting a frequency, corrected by the frequency error, for the RF oscillator as reference frequency for further calibration operations.

Claims

1. A method for calibrating a frequency of an RF oscillator in a mobile part of a mobile communications device when the mobile part is first switched on, the method comprising the steps of:

sampling a modulated carrier that is transmitted by a base station and has a prescribed frequency accuracy, wherein a scanning of the modulated carrier is performed via a frequency search algorithm with the modulated carrier being demodulated, a signal thus demodulated being compared in an evaluation and synchronization program via a correlator with a sequence known in advance, and a correlation peak in an output of the correlator being determined;

determining a frequency error between the frequency of the RF oscillator in the mobile part of the mobile communications device and a known channel frequency of the base station by comparing the determined correlation peak of the output of the correlator with a channel raster, known in advance to the mobile communications device, of the base station;

synchronizing the mobile communications device with the modulated carrier; and

adopting a frequency, corrected by the frequency error, for the RF oscillator as reference frequency for further calibration operations.

2. A method for calibrating a frequency of an RF oscillator in a mobile part of a mobile communications device as claimed in claim 1, wherein the method is carried out under a UMTS Standard, with the sequence being a pSCH sequence uniform throughout an associated network.

3. A method for calibrating a frequency of an RF oscillator in a mobile part of a mobile communications device as claimed in claim 1, wherein the method is carried out repeatedly, starting out from the respective reference frequency last determined.

4. A method for calibrating a frequency of an RF oscillator in a mobile part of a mobile communications device as claimed in claim 1, wherein, for a first synchronization of a transmitted signal, use is made of an arbitrary base station and, for a subsequent callup, use is made of a carrier of another base station.

5. A method for calibrating a frequency of an RF oscillator in a mobile part of a mobile communications device as claimed in claim 4, wherein a single multi-mobile part is used for synchronizing the mobile communications device with mutually synchronized base stations of different standards.

6. A method for calibrating a frequency of an RF oscillator in a mobile part of a mobile communications device as claimed in claim 1, the method further comprising the step of performing a calibration over a temperature range via a temperature measurement.