Investigation of interference in a mobile phone from a DC-to-DC converter

Turning on the LCD screen of a mobile phone causes desensitization of its receiver in the GSM lower frequency band (900 MHz). In this paper, the measurement techniques used for the investigation of intra-system interference in a mobile phone caused due to the DC-DC converters present on-chip the LCD driver IC are presented. An equivalent noise source model is created by modelling the flexible printed circuit board traces and obtaining a Thevenin equivalent noise by changing the load conditions.