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0
votes
3answers
39 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
0answers
51 views

Preventing High Frequency EMI on Headphone Output

I am working a project with the following final power amplifier for audio output. What is best practice to prevent injecting RF EMI onto the cable from the MPU(tens of Mhz) and another radio ...
0
votes
2answers
58 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
vote
1answer
100 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 ...
5
votes
4answers
490 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 ...
3
votes
1answer
124 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
vote
2answers
107 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
votes
3answers
341 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 ...
4
votes
2answers
407 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 ...
0
votes
2answers
895 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 ...
3
votes
2answers
2k 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
vote
0answers
74 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 ...