ASK Modulator Spur reduction using Sigma Delta Modulator and Oscillator

Abstract

This paper proposes a technique that uses the Sigma Delta modulator and oscillator to reduce the modulation reference clock in dedicated short range communication (DSRC) applications using Amplitude shift Keying (ASK) modulation. The digital modulator's reference clock is supplied from an oscillator that is frequency-tunable with current and capacitors. Sigma-delta modulator modulates the current of the oscillator to reduce the spur by clock-dithering the components of the digital modulator reference clock occurring at the TX output. The proposed structure is implemented using CMOS 130nm process and uses 1.2V supply power.