US Patent 7187705 Analog spread spectrum signal generation circuit

An analog spread spectrum signal generation circuit. A clock generator generates a periodic signal. A plurality of switchable analog loading elements each load the periodic signal by a respective load to vary propagation delay of the periodic signal to an output node. A decoder controls the plurality of switchable analog loading elements. A counter coupled to drive the decoder causes the output node to generate a periodic spread spectrum signal with modulated phase. In one embodiment, the periodic spread spectrum signal with modulated phase is used for reducing radiated electromagnetic interference and downstream phase-locked loop tracking error.