Questions tagged [emissions]

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33 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 ...
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48 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. ...
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0answers
25 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 ...
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1answer
54 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 ...
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2answers
50 views

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

Why are radiated emissions standards for consumer electronics different from industrial? Source:??
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1answer
57 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?
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3answers
118 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....
1
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2answers
89 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 ...
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0answers
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 ...
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1answer
30 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 ...
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2answers
98 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 ...
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0answers
44 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 ...
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1answer
71 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 ...
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2answers
44 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 ...
3
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2answers
717 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 ...
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0answers
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 ...
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1answer
63 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,...
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2answers
2k 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 ...
1
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1answer
165 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 ...
1
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1answer
184 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 ...
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4answers
881 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 ...
3
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3answers
771 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 ...
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2answers
105 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 ...
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3answers
67 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 ...
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3answers
333 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 ...
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1answer
143 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 ...
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2answers
201 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 ...
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1answer
85 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 ...
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3answers
635 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 ...
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2answers
276 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 ...
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1answer
745 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 ...
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4answers
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'...
3
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1answer
587 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 ...
2
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2answers
492 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 ...
3
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3answers
1k 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 ...
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2answers
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,...
1
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2answers
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 ...
4
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2answers
5k 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 ...
1
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0answers
123 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 ...