Automatic calibration of modulated frequency synthesizers

Abstract

This paper describes a new approach to the automatic calibration of modulated phase-locked loop (PLL) frequency synthesizers. The new calibration approach tunes the response of the PLL while the synthesizer is in service and compensates for process and temperature variation. The availability of this new calibration method allows the use of precompensation techniques to achieve high data rate modulation of sigma-delta (6 1) frequency synthesizers. The calibration method can be applied to Gaussian frequency shift keying (GFSK), Gaussian minimum shift keying (GMSK) modulation, and also -ary FSK modulation. A low-frequency board level prototype has been constructed to validate the calibration approach.Index Terms-Calibration, Gaussian frequency shift keying (GFSK), Gaussian minimum shift keying (GMSK), modulator, synthesizer.

Mobile and Wireless Communications

“…FSK modulation has been adopted as it allows the use of power efficient, non linear RF power amplifier (McMahill & Sodini, 2002). The high tolerance to system linearity allows decreasing operating current and supply voltage.…”

“…Loop Filter This solution requires stabilizing the VCO gain and the frequency versus temperature and process. The quadrature, or I-Q modulator, illustrated in Figure 7 is the most flexible one since any modulation type may be produced through correct choice of I(t) and Q(t) signals (McMahill & Sodini, 2002). The transmitted data sequence is processed digitally through a DSP and then converted to analog base band signal through a pair of digital-to-analog converters (DACs) to drive RF mixers whose local oscillator inputs are in quadrature.…”

A Fully Integrated 2.45-GHz Frequency Synthesizer and FSK Modulator

“…Frequency Modulation based schemes such as Frequency Shift Keying (FSK) or Gaussian Frequency Shift Keying (GFSK) modulation, are of special interest for wireless communication systems and for portable, battery operated transmitters as it allows the use of power efficient non linear RF power amplifier [1]. The high tolerance to system linearity allows to decrease operating current and supply voltage.…”

“…The quadrature, or I-Q modulator (Fig. 2b), is the most flexible one since any modulation type may be produced through correct choice of I(t) and Q(t) signals [1]. The transmitted data sequence is processed digitally through a DSP and then converted to analog baseband signal through a pair of digital-to-analog converters (DACs) to drive RF mixers whose local oscillator inputs are in quadrature.…”