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