Smear jobs (Electromagnetic Spectrum Division)
EDN Magazine Blog
Dec 5 2005 7:06AM | Permalink | Email this | Comments (7) |
This blog and the comments that follow have some interesting things about an EMI suppression technique.
EDN Magazine Blog
Dec 5 2005 7:06AM | Permalink | Email this | Comments (7) |
A recent Design Idea entitled "Dither a power converter's operating frequency to reduce peak emissions" has drawn several heated comments from readers regarding the wisdom—or lack thereof—of reducing the EMI signature of an SMPS (switched-mode power supply) by smearing it over a broad swath of spectrum.
Interference production by consumer electronics and electrical appliances has existed since the dawn of the radio age. Certain early-vintage incandescent lamps produced RF that interfered with reception, as did arcing thermostats, neon advertising signs, electric razors, and just about everything that drew juice from the ac line. Some noise sources didn't have to plug in—for instance, automobile-ignition noise plagued television reception in the immediate post-WWII era.
What's new in SMPS design—and, for that matter, in BPL (broadband over powerline) data transmission, frequency-hopping communications equipment, and baseband or extremely wideband systems—is their common tendency to disperse signals and noise over a range of frequencies.
Interference production by consumer electronics and electrical appliances has existed since the dawn of the radio age. Certain early-vintage incandescent lamps produced RF that interfered with reception, as did arcing thermostats, neon advertising signs, electric razors, and just about everything that drew juice from the ac line. Some noise sources didn't have to plug in—for instance, automobile-ignition noise plagued television reception in the immediate post-WWII era.
What's new in SMPS design—and, for that matter, in BPL (broadband over powerline) data transmission, frequency-hopping communications equipment, and baseband or extremely wideband systems—is their common tendency to disperse signals and noise over a range of frequencies.
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