Questions tagged [emissions]

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Conducted/Radiated emissions through 40-pin FFC cable

I have a 40 pin FFC cable that looks like this between 2 PCB's: https://www.digikey.com/en/products/detail/molex/0151660427/3281308 The problem is I'm getting radiated emissions from mostly the ...
Voltage Spike's user avatar
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2 answers
93 views

Conversion of radio emissions to decibels and role of impedance ratio to power ratio

This question is about a web article about radio noise suppression by Ferrite beads. The above diagram plots of a family of four curves for the ferrite bead. Each curve depicts the relation of ...
Jacob Miller's user avatar
1 vote
1 answer
208 views

EMC Radiated Emissions, peak vs quasi-peak

This is regarding some Radiated Emissions testing unintentional radiator: Critical frequency is at 314.986 MHz Polarization is Horizontal Peak detector is 53 dBμV/m Quasi-Peak detector is 56.68 ...
Dimitar Zhekov's user avatar
12 votes
2 answers
2k views

Why should I route the feedback trace under the output capacitor?

I'm looking at the TI TPS5430DDAR. In the reference circuit, it has a note to route the feedback trace under the output filter capacitor. It feels like it would be much more simple/direct to not do ...
Helpful's user avatar
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1 answer
84 views

Test lab noise floor variance and emission limits

I have recently taken part of noise floor measurements for emission tests from two separate EMC labs, both well known and international companies. The thing that shocked me is the dramatic difference ...
NoobPointerException's user avatar
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0 answers
87 views

EN55032 Conducted Emissions - 40cm From Vertical Reference Ground Plane

I've always wondered why we need to position the EUT 40cm from the metallic wall for conducted emissions testing. Does it have something to do with the EUT capacitively coupling the higher end of the ...
SuperNintendoChalmers's user avatar
3 votes
2 answers
188 views

Density of braid shielding

Does the shielding braid density depend on frequency range to provide good cable shielding? I have read that braiding works well for low frequency but that at high frequency the effectiveness ...
Rishab's user avatar
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1 vote
0 answers
448 views

Conducted Emissions for Ethernet ports

A device has a DC power port as well as 2 Ethernet ports. One of the ethernet ports supports PoE++. Basically, the EUT can be powered through PoE. I have a question regarding Conducted Emissions ...
Dimitar Zhekov's user avatar
7 votes
4 answers
574 views

Radiated emissions from WS2812 LEDs

We have a product which is failing EMC testing on radiated emissions. It fails by approx. 25 dBuV at the peaks. The product has a large 550x900 mm opaque 5mm acrylic window. Behind this, at a 50 mm ...
srlevitt's user avatar
5 votes
2 answers
577 views

EMC emission harmonics

I have a crystal associated with an Ethernet-to-PCIe bridge operating at 25 MHz. I observe spikes at 62.5 MHz and 312.5 MHz. Those harmonics are 2.5 times and 12.5 times the crystal fundamental ...
user avatar
17 votes
6 answers
3k views

Failed radiated emissions test on USB cable - USB module hardware and firmware improvements

I posted a few days about ago how our product failed ESD testing. Well, it also failed radiated emissions testing so I thought I'd make a separate post. The product is a 5V USB powered, non-radio, 3v3 ...
Geo's user avatar
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173 views

Shielding issues with RJ45 connectors

I've been dealing with a pretty nasty radiated emissions problem at work and I've pretty well exhausted any list of potential solutions/mitigation tactics to resolve this given the design constraints. ...
carbonboy25's user avatar
0 votes
0 answers
80 views

Why are the radio emissions from a vga cable polarized

So im doing this college project for my CS degree, and we're starting to notice that more and more the project falls short on what we've learned, either way i would like to put a complete answer ...
Imeguras's user avatar
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4 votes
2 answers
200 views

When to employ RF shield cover on PCBA?

During reparations and teardowns I have frequently come across PCB-mounted RF shields and covers. While I don't typically work with GHz processors or design RF modules I wonder if such covers could be ...
NoobPointerException's user avatar
0 votes
1 answer
146 views

Estimate electromagnetic emission due to current in wire

I am working on a project that will need to pass CEM requirements. I would like to "estimate", as in, get an order of magnitude of the electromagnetic emission. The device include 2 parts. ...
Romain's user avatar
  • 101
2 votes
1 answer
94 views

How should non-shielded connectors be handled in a casing design?

Assume a design with a mix of shielded connectors (e.g. USB, HDMI) and non-shielded connectors (e.g. standard 0.1" headers) A metallic casing is designed to mesh with the shielded connector ...
jfowkes's user avatar
  • 618
0 votes
1 answer
55 views

BLE emission when disconnected and waiting connection

I'm working on a toy device that goes into an airplane. It is using a BLE device and yet my knowledge about is a quite limited. If I understood correctly, usually in protocols: the device advertise, ...
robotsmith's user avatar
6 votes
5 answers
393 views

What could be generating this waveform in an EMC Compliance test?

We are having trouble with a CISPR-11 (EN55011) Radiated Emissions Class B compliance test in one of our solutions. The troubling part of it is basically an industrial motherboard (with a commercial ...
Seelenjäger's user avatar
4 votes
3 answers
741 views

EMC 30-50 MHz emssions

I was trying to pass EMC tests for my 48V 5A BLDC driver and failed in 30-50 MHz range. I think I found the problem in my drive circuit, but I have a few questions that got me thinking, maybe someone ...
Eugen's user avatar
  • 61
0 votes
0 answers
479 views

What does a capacitor in parallel with a pull up resistor at the drain of a N mosfet do?

I am analyzing a past design that uses a GPIO to toggle the N mosfet on and off. The resistor is just a super long winded trace on a separate board. There is a capacitor in parallel with the resistor. ...
GG19228's user avatar
  • 39
1 vote
1 answer
70 views

FCC rules for wideband / spread spectrum devices

I'd like to clarify how the FCC measures power in a frequency band (both for intentional and unintentional radiators). There are devices which either frequency hop (output is a sine wave, but center ...
Alex I's user avatar
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1 vote
1 answer
74 views

Differential emission of LED die under changing current?

This is going to be a bit too specialist for most people, but here goes... Normally we treat LEDs as point sources. However, they are actually flat chips that emit light from the surface. I am ...
Dirk Bruere's user avatar
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3 votes
2 answers
93 views

Why are radiated emissions standards for consumer electronics different from industrial?

Why are radiated emissions standards for consumer electronics different from industrial? Source:??
Will's user avatar
  • 61
0 votes
1 answer
251 views

Why isn't capacitive coupling considered in EMC testing?

It seems like the emissions of interest in EMC testing are radiated and conducted emissions. Is this because capacitive coupling is so weak it doesn't pose a threat to other devices?
zsky3333's user avatar
  • 489
3 votes
3 answers
1k views

How to estimate the temperature of a filament?

I would like to know how I can estimate/calculate the temperature of a heated filament. For example, the filament (rhenium) is 0.2mm in diameter and heated with a voltage of 6.4V and a current of 2....
Mattes's user avatar
  • 39
1 vote
2 answers
382 views

In what pattern does the electrons get emitted from cathode in thermionic emission?

We have structure with an cathode and filament at the center. A cylindrical shaped anode with cavities surrounds the cathode (fig 1). When the cathode get heated the electrons are emitted from cathode ...
Prerna's user avatar
  • 171
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0 answers
49 views

RF output power too high because of PSU cable

We have a situation where an integrated 868-920MHz RF chip is programmed to output the chip maximum of 14 dBm power. From professional chamber/measurement equipment 16 dBm is measured in the carrier ...
EmilBonnevie's user avatar
0 votes
1 answer
91 views

FCC/ETSI conformance with backscatter

Do passive backscatter devices fall under regulations of FCC/ETSI? Suppose a system emits a 4W EIRP tone in the ISM band (conforming to FCC/ETSI regulations). A fully passive device backscatters data ...
divB's user avatar
  • 1,316
0 votes
2 answers
130 views

EMC issue on 6 layer PCB design [closed]

I have EMC issue and there is spike at 64 MHz on my 6 layer PCB design. I have used many decoupling capacitors and ferrite beads according to the datasheet. Is there any cad tool to measure on which ...
Ashkan's user avatar
  • 39
2 votes
0 answers
48 views

Spurious microwave emissions perhaps coming from conducting TRIAC controlling AC power?

I have a TRIAC switch on an 240VAC single phase AC line. There is voltage on the gate as specified, there is a small dead band near zero. I.e. it is conducting as expected. However, I'm picking up ...
user avatar
1 vote
1 answer
99 views

What receiver is appropriate for studying compromising emanations in 2019?

I'm currently reading the Cambridge Technical Report Number 577, Compromising emanations: eavesdropping risks of computer displays, by Markus G. Kuhn and published in Dec 2003. In the paper, Kuhn uses ...
BLUC's user avatar
  • 113
1 vote
2 answers
72 views

Adjacent Signal Selectivity: Section 6.1 of ETSI EN 303 372-2 (RED testing). Bad procedure/standard?

I'm doing pre-certification testing to ETSI EN 303 372-2 V1.1.1 (2016-04), specifically the Adjacent Signal Selectivity test in Section 6.1. I am a Systems engineer with lots of experience designing ...
BobC's user avatar
  • 113
3 votes
2 answers
964 views

What is the acceptable margin for radiated emission on an European CE device

One of our prototype (IOT gateway) has completed the emission test (EMC) but we have a margin on two particular frequencies, just wondering what is the acceptable margin for CE device in Europe ? I ...
rajeshk's user avatar
  • 133
4 votes
0 answers
1k views

Do I need to get a device certified by the FCC if it uses the ESP32/8266? [duplicate]

I plan on making a device that the user can control with their phone via a WiFi connection to an ESP8266 or ESP32. If I end up selling this device, will I need to get it certified? The ESP32/8266 has ...
888's user avatar
  • 179
0 votes
1 answer
126 views

EMC conducted emissions go up if input cable is close to inductor

I am measuring conducted emission at the input of a SEPIC converter. At first, the emissions are only about 45 dBµV at switching frequency. But when I put my finger on the SEPIC (coupled) inductor,...
B. Kraemer's user avatar
8 votes
2 answers
3k views

Twisted pair for mains AC load wiring?

Working on an enclosure in which there will be low voltage high precision circuitry (my area of more experience) coexisting with fairly high current (~15A) 120VAC load wiring (my area of less ...
ChateauDu's user avatar
  • 128
2 votes
1 answer
562 views

Radiated Emissions

I have been performing some EMC testing on a product (which I didnt design) Its been a right barrel of laughs and it was quite challenging decreasing the radiated emissions below the 50dBuV/m limit ...
Jamie Lamb's user avatar
1 vote
1 answer
299 views

Effect of a longer loopback cable on radiated EMI

We have a product that we successfully ran through radiated EMI testing (EN55022) with our highest peak approx. 13dB under the permissible limit. Looking at our test setup and what is required to ...
1N4007's user avatar
  • 507
0 votes
4 answers
1k views

Capacitive coupling between hot and cold ground

Its understood from other Q&A regarding this topic, the link between rectified mains side and low voltage DC side of most smps are to provide some sort of grounding for very high frequency EMI ...
soosai steven's user avatar
3 votes
3 answers
975 views

Will a star-shaped Vdd net reduce ground oscillations?

One of EE.SEs famous answers advocates to use local ground-planes or -nets on ICs that generate broadband noise on power rails (like microcontrollers) in order to reduce excitation of planes as patch ...
Andreas's user avatar
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2 votes
2 answers
130 views

RF Emissions Testing and Discovery of Hidden Undocumented RF Device

I would like to know is it possible to induce RF emissions (incidental waves (re-radiation) from a RF device that is not transmitting ? The purpose of this testing is discover whether there is a ...
David J's user avatar
  • 77
0 votes
3 answers
74 views

Is it possible to induce RF Emissions from a RF enabled Device

Would it be possible to take a device anything such as a wireless router or a wireless video and induce unintentional RF emissions while no power is supplied to the device ? Can you send it some range ...
David J's user avatar
  • 77
4 votes
3 answers
599 views

SIM900 Conducted Emissions Fail

I'm currently having trouble getting a product through EMC. Radiated emissions were comfortably under the limit, but conducted are failing badly. Here are the results: The noise appears to be ...
Skov's user avatar
  • 41
-2 votes
1 answer
156 views

RF Emissions (Unintentional) [closed]

Hello can a device emit unintentional RF emissions when there is no power supplied to the RF embedded device such as a wireless router ? [UPDATE 1] YES when there is absolute NO power whatsoever ...
VikkiM's user avatar
  • 57
0 votes
2 answers
313 views

Transceiver and RF Emissions (Unintentional)

My question is simply what is RF emissions (unintentional) and how does it relate to a device (such as a smart phone) which contains a transceiver or transmitter (baseband IC) ? Which part of a RF ...
VictorM's user avatar
  • 17
0 votes
1 answer
96 views

FCC Per Unit Factory Test For Intentional Radiators

Can someone clarify if each unit for an intentional radiator must perform factory emission testing or is this only required for a one time tst in an approved test lab? Is this tied to a specific ...
MountainLogic's user avatar
0 votes
3 answers
934 views

Via fences or pickets important parameters for design

What is more important for EMI shielding effectiveness with respect to guard traces and via fences, the width of the copper trace that circles around the area or the distance between the vias to ...
broncoremy's user avatar
0 votes
2 answers
706 views

How dBuV value changes with distance?

I've got an emissions source that's designed to generate a peak at a certain frequency that when measured by an antenna 3m away gives a value of X dBuV. If the emissions source if moved closer to ...
Amr Bekhit's user avatar
  • 1,298
1 vote
1 answer
938 views

Can I cross the output inductor trace with input power line?

I'm attempting to learn a little more about SMPS design while referring to existing designs and posts such as this one: SMPS PCB Design Critic I'm implementing an AL8805 based constant current buck ...
carveone's user avatar
  • 2,578
7 votes
4 answers
2k views

How to fix EMC problems for existing designs?

I'm going to be looking at a few products that have failed EMC radiated emissions testing and will need to apply fixes in order to make them pass (unfortunately, in these cases, two of the designs can'...
Amr Bekhit's user avatar
  • 1,298