Today, microprocessors are found in personal computers, office appliances, and many digital home electrical appliances, and the harmonics of the respective clock signals are emitted over a wide frequency range. Recent years have seen the development of spread-spectrum clock (SSC) techniques, which widens the frequency band by sweeping the clock frequency. SSC techniques have been adopted in many electronic devices, since its use reduces the maximum amplitude of measured noise spectrum; however, this does not mean that noise power is reduced. Further, we have yet to clarify the precise consequences of the SCC in terms of the effects of electromagnetic interference caused by radiated noise on nearby wireless systems. Our group is therefore currently investigating the results of the introduction of the SCC method, for noise spectra as well as for a variety of wireless systems.