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Electromagnetic emission and reduction of digital circuits with various clock frequencies

Md Mustam, Saizalmursidi (2011) Electromagnetic emission and reduction of digital circuits with various clock frequencies. Masters thesis, Universiti Tun Hussein Onn Malaysia.


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Most digital electronic products must comply with the Electromagnetic Compatibility (EMC) requirements to access the market of EMC-enforced countries. One of the EMC requirements is to control unwanted emission of electromagnetic (EM) energy. However, as the clock frequency goes higher, it is a greater challenge to design EMC-complied circuitry due to the problem of rahation in the harmonic frequencies. Consequently, it is crucial to understand the basic concepts of the emission mechanisms and the suitable mitigation techniques to ensure EMC compliance. This research was to characterise the sources of radiated emissions from a hgital circuit and investigate the effects of employing EMC design practices on the reduction of emission. The novelty of this research is athibuted to the comprehensive study on the sources of emission and mitigation techniques of digital circuits on double-sided board at 0.125 MHz, 0.25 MHz, 1.25 MHz, 2.5 MHz, 12.5 MHz and 25 MHz. The radiated emissions are measured for various mitigation techmques such as the size of loop area, length of cable and signal currents. The measurement results are then compared with the radiated emission limits of European Norm (EN) 55022 and the Federal Communications Commission (FCC) Part 15 Class B. Nine Printed Circuit Board (PCB) layouts with different design are designed and fabricated by using the IsoPro software and the Quick Circuit milling machine. The peak measurements were conducted in a 3-meter Semi Anechoic Chamber (SAC) in the frequency range from 30 MHz to 1 GHz. The results showed a reduction of emission level by an average 6.5 dB at frequency below 800 MHz (harmonics) by keeping the loop of return current small. However, the emission level for harmonic frequencies of 25 MHz or 12.5 MHz clock signals increase above the frequency of 300 MHz. Series resistor on each signal trace reduces the level by an average 10 dB above the frequency 175 MHz to 1 GHz. The employment of small area of ground plane for critical clock trace routing and wide power trace can reduce the emission by an average of about 9.1 dB.

Item Type: Thesis (Masters)
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800-8360 Electronics
Depositing User: Normajihan Abd. Rahman
Date Deposited: 23 Apr 2012 00:43
Last Modified: 23 Apr 2012 00:43
URI: http://eprints.uthm.edu.my/id/eprint/2421
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