xenquan - RF Cafe Forums
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Post subject: xenquan
Posted: Mon Sep 05, 2005 9:38 pm
Joined: Mon Sep 05, 2005 9:32 pm
Hi All! I'm new to RF and electronics. WOuld like to ask you guys a very basic question that I couldn't get from internet. What is the difference between RF & CPU frequency? Does CPU frequency exhibit electromagnetic characteristics? Thnx!
Posted: Tue Sep 06, 2005 4:29 am
Posted: Tue Sep 06, 2005 9:06 am
Joined: Mon Sep 01, 2003 6:59 pm
RF, which stands for "radio frequency," does not really have a formal definiton for at which frequency it starts. Generally, anything above around 30 MHz is considered RF, but again, that's just some people's rule of thumb.
CPU frequencies are almost always a broad spectrum of frequencies created by the clocks driving the CPUs as well as all the internal frequencies created inside. Since all are rectangular in form, with vertical leading and trailing edges, odd harmonics of all the fundamentals are created with varying amplitudes. Add to that the mixing process that occurs due to nonlinearities in the circuitry, and you get a real mess of spectral noise. The higher the CPU frequency is, the worst it gets, usually.
Computer product vendors go to great trouble to shield their circuitry, and in fact are required by the FCC (in the U.S.) and CE (E.U.) to keep emissions below certain levels.
So, in answer to your question, yes, CPU frequencies are essentially RF.