modified 1998-08-11.
useful tools for electromagnetic compatibility (EMC), both (a) to measure how much your device radiates (EMI), to make sure it doesn't interfere with other devices, and (b) to generate radiation, to make sure your device doesn't flake out when placed near other radiators.
Also: (c) design tips and various components that improve EMC.
Note that this is woefully incomplete. Please help me flesh this out.
EMI, RFI, and ESD
info on the "political laws" regulating the use of photons and electromagnetic waves.
Contents:
Related pages:
electro-magnetic compatibility
I would like to know of ways to
Here are a couple of ways I've found already; please help me find more.
Besides the physical laws that limit what you can do with photons, there are also bunches of legal limits to what you can do.
FCC Compliance and Information Bureau http://www.fcc.gov/cib/
see #fcc_spectrum
"Radio waves do not recognize political boundaries" -- Paul Cary.
frequency chart; the electromagnetic spectrum
[FIXME: lots of stuff scattered elsewhere] [I'm putting the spectrum here in emc_faq, rather than machine_vision, because in EMC it's nice to know exactly what frequency you're dealing with and what else is on that frequency ... and its harmonics ... while most machine vision stuff doesn't really matter which frequency, as long as the transmitter and the receiver agree.] [FIXME: maybe make an independent page out of this ?]
[FIXME: email Scott Acton]What is the color of the Universe? This seemingly simple question has never really been answered by astronomers. It is difficult to take an accurate and complete census of all the light in the Universe.
However using the 2dF Galaxy Redshift Survey - a new survey of more than 200,000 galaxies which measures the light from a large volume of the Universe - we have recently been able to try and answer this question. We have constructed what we call "The Cosmic Spectrum", which represents all the sum of all the energy in the local volume of the universe emitted at different optical wavelengths of light. ... We have de-redshifted all our light before combining
-- http://www.timezone.com/messageView.aspx?forumId=tzclassic&msgId=tzclassic000707VHF (roughly 100 to 200 MHz) and UHF (roughly above 200 MHz)are line-of-site propogation. Those signals are easily scattered and absorbed. They are scattered and absorbed by water (rain, snow, mist, fog, ... ). ...
The civilian model of this watch is essentially a Class B EPIRB, operating at 121.5 Mhz. The military model is at 243 Mhz, I believe.
...
Alert detection on the Class A/B EPIRBs is being phased out (at least on the 121.5Mhz band), likely by 2008.
In the USA, the Coast Guard no longer recommends that Class A or B EPIRBs be purchased.
...
1. 121.5 is monitored by SARSATS, high-flying commercial aircraft, and ...
2. In the US, land areas, all SARSAT data goes to the AFRCC (Air Force Rescue Coordination Center) in Langley VA, and, when a signal is received and sufficient locational data is reduced, authorities in the appropiate state are notified. The SARSAT "Hits" can derive the core frequency, whether it is a dual frequency or a single frequency (remember, the second harmonic of 121.5 is 243 MHz), ...
3. The location derived from a SARSAT hit is good for perhaps a 20 - 30 square mile area - and sometimes worse. Both local air and ground resources need to be called out to localize the actual transmitter in conjunction with the SARSAR merges.
...
6. Thankfully, 97% of the emergency beacons prove to be false alarms. Most are resolved as "ramp turnoffs" - someone was working on their aircraft and kicked the ELT switch on. Its isn't always just the private pilot doing this, - the military has its share of false alarms. It is amazing how sensitive those SARSATS are, though. We once found an ELT with a weak battery that was thrown into a steel dumpster with the cover down. The impact set it off and the SARSAT still heard it. (remember that if you think NSA can't monitor your cell phone calls!)
... Prepare to wait hours before you are discovered, though. ...
...
... ELT's get triggered accidentally all the time as you know. A hard landing can trigger one and a good pilot will always flip his radio to 121.5 to check after a hard landing before shutting down the radios and engine. ... That ELT that was in the dumpster likely radiated a signal that was much stronger than you might assume. ... that dumpster could easily have been acting as the antenna.
...
Search and Rescue ... a distress beacon on either 121.5 MHz or 243.0 MHz ...
Along coastal areas, where much of the US population lives, the most common source of false alarms are marine EPIRBs (Emergency Position Indicating Radio Beacon) that a boater brings home, throws in the closet, turned upright, which closes the gravity switch, and WAH-WAH-WAH . . .
In much of the US, the satellite that first receives this signal will be RUSSIAN . . . yup, Russian . . . after all, we watch them and they watch us. We have agreements to mutually advise each other of such things, and they'll call Langley.
...
... ELTs (Emergency Locator Transmitters, the aviation beacon) ...
Yes, there are four countries who have launched and support the SARSAT network; USA, Canada, Russia, and France. ...
...
Elektromagnum http://www.newphys.se/elektromagnum/ devoted to speculative electromagnetics and especially the possible explanation af gravity/inertia by EM.
ELMA http://www.elma.com/ shielded enclosures
some FCC labs http://www.act1.com/fcclab.htm
Credence Technologies, Inc. http://www.credencetech.com/ EMC probes.
FAQ: Sources of EMC and Safety Compliance Information http://world.std.com/~techbook/compliance_faq.html FAQ for the sci.engr.electrical.compliance newsgroup
The Complete, Unofficial TEMPEST Information Page \ http://www.eskimo.com/~joelm/tempest.html lists one of the more ... controversial ... aspects of electromagnetic compatibility.
Rubbercraft Corp. http://www.rubbercraftcorp.com/ EMI, RFI, and ESD shields
International Mobile Telecommunications http://www.itu.int/imt/
The IEEE Electromagnetic Compatibility Society http://www.emclab.umr.edu/ieee_emc/
A 5V peak-to-peak, 10 MHz clock line... has many harmonics ... one of which is a 450 mV 110 MHz signal ! Another is a 225 mV 220 MHz signal. ... square wave = cos(ωt) - cos(3ωt)/3 + cos(5ωt)/5 - cos(7ωt)/7 + ... ... one design problem is how to get a signal from one IC to the net without radiating these harmonics ... to other signal lines ... and ... to FCC compliance measuring devices ... the critical issue is rise time, not frequency ... ... The worst design to have is one that works most of the time. Good designers don't design to "acceptable" levels of noise immunity and margin. They design for the maximum possible noise margin, and, in doing so, they tend to have the fewest number of subsequent problems. ...
-- Douglas Brooks, "Brookspeak: Designing for performance" article in _Printed Circuit Design_ Oct. 1996.
Xref: agora alt.radio.pirate:3544 sci.electronics:66348
Newsgroups: alt.radio.pirate,sci.electronics
From: (Rick Harrison)
Subject: FCC Part 15 Rules FAQ
Followup-To: poster
Organization: The World Public Access UNIX, Brookline, MA
Distribution: na
Date: Thu, 8 Sep 1994 07:20:29 GMT
Expires: Sat, 8 Oct 1994 23:59:00 GMT
Lines: 217
excerpts from FCC "Part 15" rules
(Title 47 of the Code of Federal Regulations, Part 15)
Subpart A -- General
15.1 Scope of this part.
(a) This part sets out the regulations under which an intentional,
unintentional, or incidental radiator may be operated without an
individual license. It also contains the technical specifications,
administrative requirements and other conditions relating to the
marketing of part 15 devices.
15.5 General conditions of operation.
(b) Operation of an intentional, unintentional, or incidental radiator
is subject to the conditions that no harmful interference is caused
and that interference must be accepted that may be caused by the
operation of an authorized radio station, by another intentional or
unintentional radiator, by industrial, scientific and medical (ISM)
equipment, or by an incidental radiator.
(c) The operator of a radio frequency device shall be required to cease
operating the device upon notification by a Commission representative
that the device is causing harmful interference. Operation shall not
resume until the condition causing the harmful interference has been
corrected.
15.23 Home-built devices.
(a) Equipment authorization is not required for devices that are not
marketed, are not constructed from a kit, and are built in quantities
of five or less for personal use.
(b) It is recognized that the individual builder of home-built equipment
may not possess the means to perform the measurements for determining
compliance with the regulations. In this case, the builder is expected
to employ good engineering practices to meet the specified technical
standards to the greatest extent practicable. The provisions of 15.5
apply to this equipment.
15.35 Measurement detector functions and bandwidths.
(b) ...When average radiated emission measurements are specified in the
regulations, including emission measurements below 1000 MHz, there is
also a limit on the radio frequency emissions, as measured using
instrumentation with a peak detector function, corresponding to 20 dB
above the maximum permitted average limit for the frequency being
investigated.
Subpart C -- Intentional Radiators
15.207 Conducted limits.
(a) For an intentional radiator which is designed to be connected to the
public utility (AC) power line, the radio frequency voltage that is
conducted back onto the AC power line on any frequency or frequencies
within the band 450 kHz to 30 MHz shall not exceed 250 microvolts.
Compliance with this provision shall be based on the measurement of
the radio frequency voltage between each power line and ground at the
power terminals.
(c) The limit shown in paragraph (a) of this section shall not apply
to carrier current systems operating as intentional radiators on
frequencies below 30 MHz. In lieu thereof, these carrier current
systems shall be subject to the following standards:
(1) For carrier current systems containing their fundamental emission
within the frequency band 535-1705 kHz and intended to be received
using a standard AM broadcast receiver: no limit on conducted emissions.
(2) For all other carrier current systems: 1000 uV within the frequency
band 535-1705 kHz.
15.209 Radiated emission limits; general requirements.
(a) Except as provided elsewhere in this subpart, the emissions from
an intentional radiator shall not exceed the field strength levels
specified in the following table:
| Field strength | Measurement distance
Frequency (MHz) | (microvolts/meter) | (meters)
-----------------+------------------------+-----------------------
0.009-0.490 2400/F(kHz) 300
0.490-1.705 24000/F(kHz) 30
1.705-30.0 30 30
30-88** 100** 3
88-216** 150** 3
216-960 200** 3
Above 960 500 3
-----------------+------------------------+-----------------------
**Except as provided in paragraph (g), fundamental emissions from
intentional radiators operating under this Section shall not be
located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz or
470-806 MHZ.
{Editor's note: paragraph (g) allows perimeter protection systems
and biomedical telemetry devices to use the frequency bands 54-72 MHz,
76-88 MHz, 174-216 MHz or 470-806 MHZ. These are TV broadcast channels.
No other unlicensed transmissions on TV frequencies are permitted.}
15.215 Additional provisions to the general radiated emission limitations.
(a) The regulations in 15.217 through 15.251 provide alternatives to the
general radiated emission limits for intentional radiators operated in
specified frequency bands. Unless otherwise stated, there are no
restrictions as to the types of operation permitted under these sections.
15.217 Operation in the band 160-190 kHz.
(a) The total input power to the final radio frequency stage (exclusive
of filament or heater power) shall not exceed one watt.
(b) The total length of the transmission line, antenna, and ground lead
(if used) shall not exceed 15 meters.
(c) All emissions below 160 kHz or above 190 kHz shall be attenuated at
least 20 dB below the level of the unmodulated carrier. Determination
of compliance with the 20 dB attenuation specification may be based on
measurements at the intentional radiator's antenna output unless the
intentional radiator uses a permanently attached antenna, in which case
compliance shall be demonstrated by measuring the radiated emissions.
15.219 Operation in the band 510-1705 kHz.
(a) The total input power to the final radio frequency stage (exclusive of
filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground lead
(if used) shall not exceed 3 meters.
(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at
least 20 dB below the level of the unmodulated carrier. Determination
of compliance with the 20 dB attenuation specification may be based on
measurements at the intentional radiator's antenna output unless the
intentional radiator uses a permanently attached antenna, in which case
compliance shall be demonstrated by measuring the radiated emissions.
15.221 Operation in the band 525-1705 kHz.
(a) Carrier current systems and transmitters employing a leaky coaxial
cable as the radiating antenna may operate in the band 525-1705 kHz
provided the field strength levels of the radiated emissions do not
exceed 15 uV/m, as measured at a distance of 47.715/(frequency in kHz)
meters (equivalent to Lambda/2Pi) from the electric power line or the
coaxial cable, respectively. The field strength levels of emissions
outside this band shall not exceed the general radiated emission limits
in 15.209.
(b) As an alternative to the provisions in paragraph (a) of this section,
intentional radiators used for the operation of an AM broadcast station
on a college or university campus or on the campus of any other
education institution may comply with the following:
(1) On the campus, the field strength of emissions appearing outside
of this frequency band shall not exceed the general radiated emission
limits shown in 15.209 as measured from the radiating source. There
is no limit on the field strength of emissions appearing within this
frequency band, except that the provisions of 15.5 continue to comply.
{Editor's note: they probably meant "continue to apply."}
(2) At the perimeter of the campus, the field strength of any emissions,
including those within the frequency band 525-1705 kHz, shall not exceed
the general radiated emission in 15.209.
(3) The conducted limits specified in 15.207 apply to the radio
frequency voltage on the public utility power lines outside of the
campus. Due to the large number of radio frequency devices which may
be used on the campus, contributing to the conducted emissions, as an
alternative to measuring conducted emissions outside of the campus,
it is acceptable to demonstrate compliance with this provision by
measuring each individual intentional radiator employed in the system
at the point where it connects to the AC power lines.
(c) A grant of equipment authorization is not required for intentional
radiators operated under the provisions of this Section. In lieu
thereof, the intentional radiator shall be verified for compliance with
the regulations in accordance with subpart J of part 2 of this chapter.
This data shall be kept on file at the location of the studio, office
or control room associated with the transmitting equipment. In some
cases, this may correspond to the location of the transmitting equipment.
(d) For the band 535-1705 kHz, the frequency of operation shall be chosen
such that operation is not within the protected field strength contours
of licensed AM stations.
15.239 Operation in the band 88-108 MHz.
(a) Emissions from the intentional radiator shall be confined within a
band 200 kHz wide centered on the operating frequency. The 200 kHz band
shall lie wholly within the frequency range of 88-108 MHz.
(b) The field strength of any emissions within the permitted 200 kHz
band shall not exceed 250 microvolts/meter at 3 meters. The emission
limit in this paragraph is based on measurement instrumentation employing
an average detector. The provisions in 15.35 for limiting peak emissions
apply.
(c) The field strength of any emissions radiated on any frequency outside
of the specified 200 kHz band shall not exceed the general radiated
emission limits in 15.209.
--
They pretend to govern, and we pretend to obey.
Design/Analysis Consultants, Inc. (DACI) http://www.cyberspy.com/~daci/ books on grounding and proper analog design
limiting optical power, rather than radio power, uses very different techniques ... but I put it here since they're all photons.
Newsgroups: sci.physics From: meron at cars3.uchicago.edu Subject: Re: Golden eye:007 Organization: CARS, U. of Chicago, Chicago IL 60637 Date: Wed, 29 Nov 1995 21:48:27 GMT ... Adam Whybrew <whybrew at physics.ox.ac.uk> writes: ><gt5542d at acmex.gatech.edu> (Ethan) wrote: >> >>I don't know how many of you have seen Golden Eye:007, but in the movie, >>the Russians have this weapon called "golden eye". Its >>suppose to detonate a nuclear weapon in the upper atmosphere to create >>an electomagnetic storm over its target, causing every piece of electronic >>equipment to fry. I was woundering if this was possible (considering this >>is a movie) and if so how powerful would the nuclear warhead have to be? >> > >You don't even need a nuclear bomb. I work with a largish discharge excited >laser. When that fires the more sensitive electronic equipment in the room >immediately fries. It works - I've done it: to a thermometer, temperature >controller, video camera, and its power supply. You'd think I'd learn :-) > >Unless my demands are met the UN building will disappear at noon... You may get a better offer if you say "Unless my demands are met the UN building won't disappear at noon..." Mati Meron | "When you argue with a fool, <meron at cars3.uchicago.edu> | chances are he is doing just the same"
From: < elvey at hal.COM> (Dwight Elvey) Newsgroups: sci.electronics.design Subject: Re: Audio 90 degree phase shift Date: 6 Dec 1995 02:48:49 GMT Organization: HAL Computer Systems, Inc. Lines: 20 Distribution: world NNTP-Posting-Host: civic.hal.com ... (Stephen G. Matzuk) writes: |> I'm looking for a topology that I can use to achieve a 90 degr. phase shift 50- 10,000 Hz. |> without shifting the phase of the other signal. |> |> Any sugggestions? |> |> Thanks. |> |> -Steve Hi Steve If you want to shift the hole spectrum 90 degrees simulaniously, you need what is called a Hilbert transfrom. Like many have said this is difficult to do with resistor and capacitors. It is quite easily done with a special type of FIR filter in DSP. Analog Devices, TI and Motorola all make development kits in the range of $89 to $150. I personally would recommend the ADI or Mot., as I believe these both have stereo codec's. Dwight From: cfindlay at netspace.net.au (Craig Findlay) Newsgroups: sci.electronics.design Subject: Re: New EMI regulations - January 96 Date: Mon, 04 Dec 1995 05:09:18 GMT Organization: NetSpace Online Systems Lines: 41 NNTP-Posting-Host: dialup-a2-4.mel.netspace.net.au X-Newsreader: Forte Agent .99c/16.141 Andrew Holder <andrew at resmon.demon.co.uk> wrote: >Hello. > >I'm involved in designing and prototyping of small medical equipment. >The new European legislation on EMI looks pretty frightening. I don't >want to end up in jail! > >Are there foolproof ways of designing so that you are well within the >requirements ? We already have substantial ground planes on all boards >and I intend to use screened cases. Maybe its then just a case of being >careful about signal inputs and outputs from the device. > >I really don't have the sort of capital funding to be able to afford >even a day at most test houses and I certainly can't afford the >equipment myself. > >Any advice on books etc. would be greatly appreciated. BTW, I'm not a >mathematician so it'll have to be fairly readable. > Andrew, There is an extremely good and readable book on this subject called Noise reduction in Electronic Systems, by Henry Ott. I don't have the ISBN number handy but let me know if you want it and I'll email it to you. I would advise you strongly to buy this, it has a solid math basis, but Ott carefully translates this into the real world with clear writing style and easy to understand diagrams, and the only formulas in the book are ones that even I can cope with. He also provides good references. Hope this helps, Craig Findlay <cfindlay at netspace.net.au> The Law, in its majestic equality, forbids the rich, as well as the poor, to sleep under the bridges, to beg in the streets, and to steal bread. -- Anatole France From: ft63 at dial.pipex.com (Peter) Newsgroups: sci.electronics.design Subject: Re: New EMI regulations - January 96 Date: Wed, 06 Dec 1995 11:41:28 GMT Organization: UnipalmPIPEX server (post doesn't reflect views of UnipalmPIPEX) Lines: 30 NNTP-Posting-Host: ai189.du.pipex.com X-Newsreader: Forte Agent .99c/16.141 Andy, >Technically, it is the final system that has to comply. The DTI product >standards guidline on EMC (April 1993) gives a definition of 'Apparatus' >(the item which must comply) as '..an electrical or electronic appliance >or system consisting of a finished product or products having an >intrinsic function which is intended for the end user, and is supplied or >taken into service or intended to be taken into service as a single >commercial unit.' I do not wish to minimise what you are saying, but sadly, the issues of "does it need to comply" and "does it need to comply to sell" have become quite separate, in the UK's crazy headless chicken EMC environment. Everyone wants to see the CE mark on everything, even products which don't need it. This is because few people ever read the regs, and far fewer understand them. It is little use telling a customer "this product is exempted" because he will not understand. People want to see the CE mark on everything which does anything because they believe it protects them, somehow. I speak from 100% direct experience; I spend a lot of time every day talking to customers about this. I know a firm selling "CE marked" cables and gender changers... Soon we will have CE marked toilet rolls. This is getting like BS5750 in its early days (not many firms care much about it now, thank God). Peter.
-- http://news.yahoo.com/news?tmpl=story2&cid=857&ncid=757&e=10&u=/nm/20030130/od_uk_nm/oukoe_qatar_mosque_cellphonesMosque mobiles silenced Thu Jan 30, 6:37 AM ET
DOHA (Reuters) - Qatar has imported 1,000 frequency jammers to block mobile phone transmissions that disrupt prayers and sermons in the Gulf state's mosques, the daily newspaper The Peninsula has reported.
The Cellular Phone Hunter, a pocket-size device, should silence the modern-day nuisance of mobile phones chirruping during prayers, the paper said.
"Imams and muezzins (prayer callers) have been instructed to switch on the devices a few minutes before the call for prayer and keep them on till five minutes after the prayers, five times a day," Thursday's The Peninsula added.
Designing an FCC Approved ASK rfPIC(TM) Transmitterwhite paper by Myron Loewen, Microchip Technology Inc. http://www.microchip.com/download/appnote/rfpic/00242a.pdf has some good information about FCC limits and good RF circuit board design. Has a nice graph "FIGURE 4: SPECTRUM USAGE IN THE UNITED STATES: Permitted Fundamental Frequencies" showing the broadcast TV bands (this will all change with HDTV broadcast ...) and has a list of tools needed for proper testing; testing tips, ...
Useful information on high frequency measurement techniques and homebuilt probes.
This application note covers the most common EMC problems designers encounter when using microcontrollers.
One way of designing a ground plane on a two-layer board and still allow routing on both layers, is to design a ground grid [lots of vertical ground tracks on the bottom layer, lots of horizontal ground tracks on the top layer, connected with a via every time they cross.] ...
When... four or more layers are used ... one plane is used as a ground plane... one layer as a power plane ... These two planes should then be placed next to each other in the middle of the board, to reduce power supply impedance and loop area. It is not a good idea to place the power and ground planes as the outer layers to act as shields. It does not work as intended, as high currents are running in the ground plane. A shield layer would have to be a second pair of ground layers.
...
... AVR-specific subjects ...
To achieve the same protection on Reset as on other I/O pins, an external diode should be connected from Reset to VCC. A normal small-signal diode will do. In addition, a pullup resistor (10K typical) and a small filter capacitor (4.7 nF) should be connected as shown in Figure 10.
All this, of course, is not needed if Reset is connected directly to VCC, but then external reset and In-System Programming (ISP) is disabled, too.
...
Validate this page: http://validator.w3.org/check?pw=&uri=http://rdrop.com/~cary/html/emc_faq.html
Send comments, suggestions, bug reports to
David Cary
d.cary+emc7@ieee.org.