Patent ID: 7982510
Filing Date: 2011-07-19
Classification: H03C

Abstract:
1. A self-calibration method for a frequency synthesizer that can perform two point frequency modulation for data transmission, the self-calibration method including the steps of: (a) providing a frequency synthesizer, wherein the frequency synthesizer includes: (b) in a first phase, locking the first low-pass phase lock loop onto a transmission channel with a determined carrier frequency at an output of the synthesizer, and supplying a first command word to the converter in the high frequency access corresponding to the determined carrier frequency for generating a second control voltage signal for the voltage-controlled oscillator, at a first basic voltage level, (c) in a second phase, opening the first low-pass phase lock loop, while maintaining, via the first low-pass loop filter, a first control voltage signal corresponding to the determined carrier frequency for a first input of the voltage-controlled oscillator, locking a second low-pass phase lock loop, which includes a second low-pass loop filter in the high frequency access connected between the phase comparator of the first loop and a second input of the voltage-controlled oscillator, at a first output frequency equal to the carrier frequency added to a maximum modulation frequency shift, and supplying the digital-analogue converter with a second command word that represents the first output frequency, (d) in a third phase, opening the second low-pass phase lock loop while maintaining, via the second low-pass loop filter, a second control voltage signal corresponding to the first output frequency for the second input of the voltage-controlled oscillator, and comparing the converter output voltage with the voltage stored in the second low-pass loop filter to calibrate the converter gain automatically so that the converter output voltage is equivalent to the voltage stored in the second low-pass loop filter at a second voltage level, whose shift with the first basic voltage level defines the maximum equalised modulation frequency shift, and (e) in a modulation phase, closing the first low-pass phase lock loop and connecting the converter output to the second input of the voltage-controlled oscillator for two point data modulation by the voltage-controlled oscillator using a series of command words in time supplied to the calibrated digital-analogue converter and to the modulator of the first low-pass phase lock loop.