Questions tagged [emissions]
The emissions tag has no usage guidance.
44
questions
4
votes
2
answers
77
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 ...
0
votes
1
answer
75
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. ...
- 101
2
votes
1
answer
59
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 ...
- 596
0
votes
1
answer
30
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, ...
- 50
4
votes
4
answers
174
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 ...
4
votes
3
answers
415
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 ...
- 61
0
votes
0
answers
127
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. ...
- 1
0
votes
0
answers
36
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 ...
- 3,289
1
vote
1
answer
60
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 ...
- 12.1k
3
votes
2
answers
60
views
Why are radiated emissions standards for consumer electronics different from industrial?
Why are radiated emissions standards for consumer electronics different from industrial?
Source:??
- 61
0
votes
1
answer
124
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?
- 487
2
votes
3
answers
394
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....
- 29
1
vote
2
answers
254
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 ...
- 151
0
votes
0
answers
45
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 ...
- 430
0
votes
1
answer
44
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 ...
- 1,208
0
votes
2
answers
114
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 ...
- 39
2
votes
0
answers
47
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 ...
user229292
1
vote
1
answer
83
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 ...
- 113
1
vote
2
answers
55
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 ...
- 113
3
votes
2
answers
803
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 ...
- 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 ...
- 179
0
votes
1
answer
78
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,...
- 193
7
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 ...
- 118
1
vote
1
answer
231
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
...
- 317
1
vote
1
answer
242
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 ...
- 457
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 ...
- 1,687
3
votes
3
answers
883
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 ...
- 1,720
2
votes
2
answers
113
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 ...
- 77
0
votes
3
answers
72
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 ...
- 77
4
votes
3
answers
406
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 ...
- 41
-2
votes
1
answer
155
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 ...
- 57
0
votes
2
answers
255
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 ...
- 17
0
votes
1
answer
91
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 ...
0
votes
3
answers
753
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 ...
0
votes
2
answers
373
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 ...
- 1,268
1
vote
1
answer
847
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 ...
- 2,568
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'...
- 1,268
3
votes
1
answer
674
views
LT1084 as Current control Regulator
I am using LT1084 as a current control Regulator. Circuit shown below
Since the transistor Q2 is controlled by a PWM pulse so output voltage of LT1084 is varying as shown below
Since it is used as ...
- 1,454
2
votes
2
answers
586
views
Stray-inductance and capacitance of non-isolated heat-sink
I read an application-note that says the heat-sink (when not electrically isolated), is one of major source of EMI. Well I think this can be corrected at some point by good EMI filters and a good case ...
- 1,002
3
votes
3
answers
2k
views
Assessing and reducing EMI from PWM LED lighting
I need to run 50 individually dimmable LED fixtures on a pair of wires 30m long. Total load will be about 6A at 48V DC. I have to get power and control down a single pair, and AFAIK there are ...
- 31
6
votes
2
answers
1k
views
How good is coaxial cable?
My question relates to the accumulated AC voltage that will appear on the screen of a length of coax:
If the cable is properly terminated at one end and fed with data (or any signal) at the other end,...
- 380k
3
votes
2
answers
2k
views
PWM controller to meet EMI/EMC regulations
I'm designing an application in which the current running into a load is controlled by PWM.
A microcontroller generates a PWM cycle at 20kHz and this signal is used to control a MOSFET which is ...
- 989
4
votes
2
answers
6k
views
EMI/RFI emissions and computer cases
I have designed a computer case (enclosure) for mini-itx motherboards.
Its bottom and rear are made out of 2mm thick aluminium and the sides and top out of 4mm plastic (ABS).
I'd like some advice ...
- 41
1
vote
0
answers
127
views
FCC Pre-Certification Testing [duplicate]
Possible Duplicate:
FCC and CE Testing / Failure Resolution
I am looking to do some pre-certification on several boards. I know several members here are quite experienced in this area. I would ...
- 7,541