|
|
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.
(1998-01-26)
Try this search on OneLook / Google
Nearby terms:
RACF « RAD « Raddle « Radio Frequency Interference » radiosity » RADIUS » radix
This article was derived from the Free Online Dictionary of Computers and is available under ther terms of the GNU Free Documentation License.
Sony Ericsson J200i GSM Tri-band Mobile PhoneSony Ericsson J200i GSM Tri-band Mobile Phone ** Sony Ericsson J200i Mobile phone **J200i is simplicity in style. It has everything a good phone should have including excellent talk and standby time. J200i has 40-voice polyphonic ring tones and a dedicated ring tone speaker for an impressive sound. A great color screen needs great pictures. Inside J200i, you have a gallery of color pictures which you can use as onscreen wallpapers in standby mode. When you need to be reminded of a special event, a friend’s birthday or anniversary, J200i will remind you.General Features- Midnight blue phone- Color LCD- Picture gallery - Picture Phonebook - Picture wallpaper - Backlight display- Tri-band - SMS long (Text Messaging) - Themes display - 128x128 pixel display - EMS (Enhanced Messaging) - Predictive text input Networks:- GSM 900 - GSM 1900 - GSM 1800 Entertainment:- Melody composer - Content Online - Games Embedded - Polyphonic Sound 40 voices Connectivity:- Infrared port - GPRS - High-Speed Data Internet:- WAP 1.2.1 - OTA settings - WTLS Controls:- Redial - Vibrating Alert - Joystick - Menu shortcuts - Icon Desktop 9 - Sleep mode - Option key - Voice Mail - SIM card lock - Status view Organizer:- Code memo - Events calendar - Calculator - Calendar - Tasks - Stopwatch - Clock - Contacts - Alarm clock - Timer - Phone book - Conference calls - Chinese input methods - Call list Power Management:- Talk time: Up to 4.5h - Standby time: Up to 200 h Dimensions:- 3.9 x 1.7 x .7-inches - 2.6-ounces Regulatory Approvals:- CE- A-TickRetail Package Includes:- Sony Ericsson J200i GSM mobile phone- Owners Manual- Power adapter (100 – 240 V ~ 50/60 Hz)Notes:- Model: J200i- UPC: 0 95673 47398 5 Compatibility/Requirements/Disclosures: ** Requirements *** Need for a GSM phone* Active SIM card* Available power outlet for charging More ...
DB-15 Game Port SwitchDB-15 Game Port Switch ** DB-15 Game Port Switch **Easily switch from joystick to gamepad with the DB-15 GamePort Switch! Flip the switch and you can select to a 1 player/4-button mode or 2 player/2-button mode. Get this41811 Game Port Switch today!General Features:- Two (2) 15-pin female connector for game controllers- One (1) 15-pin male connector to connect to PC- Switchable button for 1 or 2 players- Red and Green LEDs- 74-inch cord length (approximate)Notes:- Model: 41811- UPC: 0 96937 41811 7 Compatibility/Requirements/Disclosures: ** Requirements *** Available 15-pin Game port* Available Joystick and Gamepad 15-pin controller More ...
Britannica Concise EncyclopediaBritannica Concise Encyclopedia Get quick answers to everyday questions about history, art, science, and other fields. A comprehensive collection of knowledge in a manageable-sized volume, this CD-ROM contains 28,000 articles condensed from the flagship 32-volume Encyclopedia Britannica. Windows 95/98/ME/2000/NT/XP and MAC More ...
32MB SDRAM PC66 168-Pin DIMM32MB SDRAM PC66 168-Pin DIMM ** 32MB SDRAM PC66 168-Pin DIMM **- 32 MB DIMM Module- 168 Pin PC-66- Major/3rd- - Synchronous- Non ECC- unbuffered Compatibility/Requirements/Disclosures:* Important note when buying memory: We only supply highquality parts that can be used in PC's reliably over thelong term. We supply only brand name memory on 3rd partymodules. * Country of Origin: Singapore, Canada, Korea, USA, Japan,Italy** Disclosures *** Picture is for representational purposes only More ...
McAfee VirusScan 8.0 2004 OEMMcAfee VirusScan 8.0 2004 OEM ** McAfee VirusScan 8.0 2004 OEM 1 year Updates**Stop viruses and keep your PC safe with McAfee VirusScan software! When you're surfing the Internet, there's more to worry about than just viruses. VirusScan software destroys threats at all entry points to your PC including email, the Internet, and even synchronization with your PDA. VirusScan includes extra firewall protection to keep your computer safe from Internet-based threats.Notes:- OEM CD ONLY More ...
Golden Books: Jack and the BeanstalkGolden Books: Jack and the Beanstalk Golden Book's Jack and the Beanstalkcomes to life in this animated storybook. Fun and educational activities, such as memory and concentration games, keep your child interested in reading and learning. Printable coloring pages too! Ages 3-6. Windows 95/98/ME/2000/XP and MAC More ...
|
