Electromagnetic interference EMI in integrated digital TV

An Electromagnetic interference (EMI) noise can couple with a high frequency TV signal on a transmission system and passes through access fiber to the optical network unit (ONU). Switch mode power supplies (SMPSs) have become the major source in the deterioration of our electromagnetic environment. This paper proposes the use of the random pulse width modulation (RPWM) technique for flattening the spectrum of the electromagnetic interference (EMI) produced by SMPS used in the integrated digital TV (IDTV). In addition this paper describes the implementation of this technique, which involves adding of a simple digital circuitry to the pulse width controller of the switching power supply used in the IDTV without any modification of the design of the other circuits. Finally this paper explains the method of clocking the pulse width modulator by a pseudo random pulse generator.