Dictionary: A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z

Radio frequency interference

hardware, testing
(RFI) Electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits.
The most important means of reducing RFI are: use of bypass or “decoupling” capacitors on each active device (connected across the power supply, as close to the device as possible), risetime control of high speed signals using series resistors and VCC filtering. Shielding is usually a last resort after other techniques have failed because of the added expense of RF gaskets and the like.
The efficiency of the radiation is dependant on the height above the ground or power plane (at RF one is as good as the other) and the length of the conductor in relationship to the wavelength of the signal component (fundamental, harmonic or transient (overshoot, undershoot or ringing)). At lower frequencies, such as 133 MHz, radiation is almost exclusively via I/O cables; RF noise gets onto the power planes and is coupled to the line drivers via the VCC and ground pins. The Rf is then coupled to the cable through the line driver as common node noise. Since the noise is common mode, shielding has very little effect, even with differential pairs. The RF energy is capacitively coupled from the signal pair to the shield and the shield itself does the radiating.
At higher frequencies, usually above 500 Mhz, traces get electrically longer and higher above the plane. Two techniques are used at these frequencies: wave shaping with series resistors and embedding the traces between the two planes. If all these measures still leave too much RFI, sheilding such as RF gaskets and copper tape can be used. Most digital equipment is designed with metal, or coated plastic, cases.
Switching power supplies can be a source of RFI, but have become less of a problem as design techniques have improved.
Most countries have legal requirements that electronic and electrical hardware must still work correctly when subjected to certain amounts of RFI, and should not emit RFI which could interfere with other equipment (such as radios).
See also Electrostatic Discharge, Electromagnetic Compatibility.


Read Also:

  • Radio-galaxy

    noun 1. a galaxy that emits much more strongly in the radio part of the spectrum than does a typical galaxy. noun 1. a galaxy that is a strong emitter of radio waves radio galaxy A galaxy that emits large amounts of radio energy. Radio galaxies are typically elliptical galaxies with large symmetrical lobes. The […]

  • Radiogenic

    [rey-dee-oh-jen-ik] /ˌreɪ di oʊˈdʒɛn ɪk/ adjective 1. Physics. produced by radioactive decay: radiogenic lead; radiogenic heat. 2. having qualities or characteristics that broadcast well; suitable for presentation on the radio. /ˌreɪdɪəʊˈdʒɛnɪk/ adjective 1. produced or caused by radioactive decay: a radiogenic element, radiogenic heat radiogenic (rā’dē-ō-jěn’ĭk)

  • Radiogold colloid

    radiogold colloid ra·di·o·gold colloid (rā’dē-ō-gōld’) n. A colloidal dispersion of a radioactive isotope of gold that emits a negative beta particle and a gamma ray for each atom of gold present, used for irradiating closed serous cavities and for liver scans.

  • Radiogram

    [rey-dee-oh-gram] /ˈreɪ di oʊˌgræm/ noun 1. a message transmitted by radiotelegraphy. [rey-dee-oh-gram] /ˈreɪ di oʊˌgræm/ noun, British. 1. a combination and record player. /ˈreɪdɪəʊˌɡræm/ noun 1. (Brit) a unit comprising a radio and record player 2. a message transmitted by radiotelegraphy 3. another name for radiograph radiogram ra·di·o·gram (rā’dē-ō-grām’) n. A radiograph.

Disclaimer: Radio frequency interference definition / meaning should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. All content on this website is for informational purposes only.