Spread clock modulated with chaotic signal to reduce EMI and RFI with master reference cell controlling a spreading slave cell

摘要

A clock signal is spread to reduce levels of electro-magnetic interference (EMI) and radio frequency interference (RFI) (see Fig. 1). The clock source comprises a master cell which may include a pair of ramp generators 203,204 feeding comparators 205,206 whose outputs feed back to the ramp generator reset/trigger inputs to produce an oscillating system. The output of this system is locked to a reference clock signal 209 using a phase frequency detector 208, which feeds back a control voltage to the ramp generator control input. The slave cell may comprises a similar arrangement of ramp generators 210,211 and comparators 213,214 to produce an oscillating output, however the comparator reference voltages include an element produces by chaotic signal generator 212. This voltage variation results in modulation of the clock frequency (see Fig. 3 306-308). The chaotic generator may use a chaotic transfer map.