Digital spread spectrum technique for electromagnetic emission reduction

摘要

Techniques for reducing electromagnetic (EM) emission in a wager-based gaming machine. A gaming machine includes one or more processors configured to generate a bus clock signal having a fundamental frequency and fundamental spectral components at harmonics of the fundamental frequency. The fundamental spectral components each have a fundamental amplitude. A signal processor is configured to generate a spread spectrum clock signal having a nominal frequency substantially equivalent to the fundamental frequency of the bus clock signal as well as nominal spectral components at harmonics of the nominal frequency. However, the nominal spectral components each have a nominal amplitude less than the fundamental amplitude of a fundamental spectral component at the same harmonic. A bus connects the signal processor with one or more elements and carries the spread spectrum clock signal to the one or more elements, thereby reducing EM emissions from the bus.

主权项

1. A machine comprising:
a master clock generator configured to generate a master clock signal; one or more microprocessors configured to: (1) use the master clock signal to generate a bus clock signal, the bus clock signal having a fundamental frequency and fundamental spectral components at harmonics of the fundamental frequency, the fundamental spectral components each having a fundamental amplitude; and (2) generate a data signal; a signal processor configured to:
generate a spread spectrum clock signal by causing the bus signal to jitter between two or more frequencies around the fundamental frequency such that the spread spectrum clock signal has a nominal frequency substantially equivalent to the fundamental frequency of the bus clock signal,wherein the spread spectrum clock signal has nominal spectral components at harmonics of the nominal frequency, the nominal spectral components each having a nominal amplitude less than the fundamental amplitude of a fundamental spectral component at the same harmonic; one or more elements controlled by the data signal and the spread spectrum clock signal; and a bus communicatively connecting the one or more microprocessors and the signal processor with the one or more elements, the bus configured to carry the data signal and the spread spectrum clock signal to the one or more elements.