LCD baseband noise modulation estimation for radio frequency interference in mobile phones

A method to predict the modulated noise coupling to an antenna is proposed and experimentally validated using a practical mobile phone. The baseband noise of a liquid crystal display (LCD) is modulated with the Tx carrier signal of cellular communication, resulting in a radio frequency desensitization problem. The modulation mechanism is understood and its circuit representation is proposed to estimate the modulated noise coupling to an antenna. The modulation coefficient, which represents a relationship between the coupled voltage and modulated current, is experimentally extracted from a stand-alone LCD panel. The proposed modulation model is successfully validated through comparison with measurements using a practical mobile phone.