Modeling and Estimation of LCD Noise Modulation for Radio Frequency Interference

A liquid crystal display baseband noise, whose spectrum is much lower than RF bands, is modulated with the carrier signal of cellular communication and interferes with an Rx receiver resulting in a desensitization problem. The modulation phenomenon is modeled with impedance parameters and a modulation coefficient. The coupled noise on the embedded cellular antenna is experimentally validated in both small- and large-frequency offset cases. In addition, to estimate the modulated noise coupling to the antenna earlier in the development process, a numerical simulation method considering the impedance of display drive IC is proposed successfully validated.