CARRIER PHASE MODULATION USING DIRECT DIGITAL SYNTHESIS FOR AN S-BAND UPLINK

Abstract

Phase modulation has traditionally been performed in analog hardware. A new product will be described that implements this function using a phase-modulating NCO IC. The modulating signal is sampled and added digitally to the phase of the carrier generated by the NCO. This method produces an output spectrum with highly accurate modulation control, low spur levels and minimal distortion. The effects of generating sampled phase-modulated signals will be described. The selection of the clock and output frequencies are critical to ensuring a clean spectrum. Resulting output spectra are shown.