FreshmanNewbie
Advanced Member level 1
I have a question on how does EMC issue arise in a PCB board.
Suppose I have a PCB board that has switching DC-DC converters and other high speed interfaces such as Ethernet, and USB.
If my board says, radiates say 75MHz, and it goes above the threshold limit, I will find out the source of the 75MHz.
While debugging, I find that I don't have a 75MHz source, but rather a 25MHz clock.
Now my question is:
1. Why does the 75MHz signal radiate and cause the issue where the 25MHz does not cause the failure in EMC?
Or in other words, how does or which factor (say PCB parasitics, layout, RC component values etc) is responsible for making the 3rd harmonic cause the problem and not the fundamental?
Suppose I have a PCB board that has switching DC-DC converters and other high speed interfaces such as Ethernet, and USB.
If my board says, radiates say 75MHz, and it goes above the threshold limit, I will find out the source of the 75MHz.
While debugging, I find that I don't have a 75MHz source, but rather a 25MHz clock.
Now my question is:
1. Why does the 75MHz signal radiate and cause the issue where the 25MHz does not cause the failure in EMC?
Or in other words, how does or which factor (say PCB parasitics, layout, RC component values etc) is responsible for making the 3rd harmonic cause the problem and not the fundamental?