Electromagnetic Compatibility (
EMC
)
•
Definition of EMC: A system is said to be electromagnetically compatible if
it
– Does not cause interference with other systems – Is not susceptible to emissions from other systems – Does not cause interference with itself
•
EMC problem may be broken up into three parts shown below.
•
Interference to the receptor may be prevented by:
– Supress the emission at its source (“Nip it in the bud!”) – Make the coupling path as inefficient as possible
– Make the receptor less susceptible to the emission
Electrical Length of a wire “k” is how long
the wire is in terms of wavelengths
k = L / λ (unitless)
where L = physical length of wire in meters and λ =
wavelength, which is the length of one complete period of the
wave at some instant of time as it propagates away from the
emitter
λ = v * T = v / f
where
v = velocity of propagation of an EM wave (m/s)
T = period of the wave (time it takes for the emitter to
generate one complete period of the wave.) Measured in
seconds.
Speed of EM wave in free space (air):
v = 1/sqrt(ε
Oε
Rμ
Oμ
R)
for a medium with
relative permeability μ
Rand relative
permittivity ε
Rboth of which range between 1
and infinity. Thus v is always slower in a
material medium compared to free space.
v = 1/sqrt(ε
O
μ
O
) = 3 x 10
8
m/s
where ε
O= permittivity of free space
= 1/(36π) x 10
-9F/m
μ
O= permeability of free space
= 4 π x 10
-7H/m
For a non-magnetic medium μ
R= 1.0
Example: Find the electrical length of a 10 cm wire in air at a frequency of 5000
MHz: k = 10*10
-2m / [(3*10
8m/s) / 5000*10
61/s)] = 1.667 wavelengths
Emitter and receptor coupling is most efficient when
their dimensions are on the order of a wavelength.
As products are made to operate faster and faster,
their operating frequencies of products increase.
Thus a wavelength becomes smaller and smaller, and
even physically small products become efficient
receptors and radiators at the frequencies at which
they operate.
Therefore….
Wavelengths at different frequencies in AIR
Note wavelength in meters = v / f = 300 / f
MHZIntel Pentium II & III & 4 Jul-99 Nov-00 Jun-03 Apr-02 Aug-02 Mar-00 May-98 Aug-98 Mar-99 Feb-99 Dec-99 Dec-99 0 500 1000 1500 2000 2500 3000 3500
Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04
Performance, Pricing and Availability
Pentium® 4 Extreme Edition
3.46GHz, Nov. 1, 2004
Core Speed Level Two Cache Size System Bus Speed 1KU Price Pentium® 4
Extreme Edition 3.46 GHz 2MB level 3 1,066MHZ $999
Intel® Xeon™
processor 3.2 GHz 1000K 800MHZ $??
Intel® Pentium® 4
Procesor 2.80 GHz 512K 533MHZ $508
Intel® Pentium® 4
Procesor 2.66 GHz 512K 533MHz $401
Intel® Pentium® 4
Speeds of PC Components
•
3.5 GHz Pentium 4 (announced on 28 August 2001)
•
533 MHz PC system bus
•
800 MHz DDRAM, RDRAM
•
1-GHz DSP chip from TI, 1-19-2004
•
6-Gbit/s backplane from PMC-Sierra, LSI Logic, Accelerant, Rambus,
2-2-2004
•
3.46 GHz Pentium 4, August 28, 2001
•
800 MHz PC system bus
•
800 MHz DDRAM, RDRAM
Speeds of Backplane and Networks
• 10-Gbit/second Ethernet over Category 5e cable demo, March 22, 2004 • 10-Gbit/, s Backplane design, April 8, 2004
Wireless Devices
• Cordless Phones – 900 MHz, 2.4 GHz (Digital Spread Spectrum)
• Walkie Talkie – 467 MHz
• Analog Cell Phone, AMPS: Advanced Mobile Phone Service – 800 MHz
• CDMA: Code Division Multiple Access – 800 MHz or 1900 MHz
• DCS-1800: European 1800 MHz GSM band.
• PCS: Personal Communication Services – 1900 MHz
• TRI-BAND – GSM phone at 900 MHz, 1800 MHz, and 1900 MHz.
• GSM: Global System for Mobile communications.
• Most wireless LANs currently use the 2.4 to 2.48 GHz band.
• ISM: Industrial Scientific and Medical Unlicensed Frequency Bands - Operates at 900 MHz and 2.4 GHz.
• MMDS: Multi-channel Multi-point Distribution Service, a fixed wireless service for data, voice and video which operates in the 2.5 GHz band in North America and in the 3.5 GHz bandwidth internationally.
• The Bluetooth system is operating in the 2.4 GHz ISM band.
The Digital Hub as Gateway
The Core of A Home Entertainment Hub
•Expanding Autopmotive Electronic Sysmtes, IEEE Computer, Jan. 2002
