Fractional divider-calibrated phase modulator and interpolator for a wireless transmitter

Abstract

Techniques are described herein for phase modulation and interpolation that support high phase modulation resolution with high linearity. Embodiments receive a digital signal that uses a sequence of K-bit digital codes to encode a sequence of instantaneous phases for phase-modulating a local oscillator signal. A fractional divider divides a reference clock into N divided clock signals at equally spaced phase intervals and selects a pair of such signals based on first designated bits of the digital code. A fractional divider-calibrated delay line generates M delayed clock signals at equally spaced phase intervals between the selected pair of divided clock signals, and selects a pair of the delayed clock signals based on second designated bits of the digital code. A digital controlled edge interpolator generates a delayed local oscillator output signal by interpolating between the selected pair of delayed clock signals based on third designated bits of the digital code.