volume | PIER Journals

2013-09-13

An Improved Model for Estimating Radiated Emissions from a PCB with Attached Cable

Jia Haw Goh,

Mr. Jia Haw Goh

Electrical and Electronic Engineering

Universiti Tunku Abdul Rahman

Malaysia

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Boon-Kuan Chung,

Dr. Boon-Kuan Chung

Electrical and Electronic Engineering

Universiti Tunku Abdul Rahman

Malaysia

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Eng Hock Lim,

Professor Eng Hock Lim

Electrical and Electronic Engineering

Universiti Tunku Abdul Rahman

Malaysia

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Sheng-Chyan Lee

Dr. Sheng-Chyan Lee

Universiti Tunku Abdul Rahman

Malaysia

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Progress In Electromagnetics Research M, Vol. 33, 17-29, 2013

doi:10.2528/PIERM13061101

Abstract

Common mode current induced on cable attached to a PCB has been a well-known source of unintentional radiated emissions. The coupling mechanism of the common mode current to the cable can be divided into two types: voltage-driven and current-driven. In voltage-driven mechanism, the common mode current is induced by electric field that couples from traces on PCB to the cable. Previous work showed that these radiated emissions can be estimate based on the self-capacitance of the trace and the signal return plane but the method is only reasonably accurate at lower frequency. This paper develops a model which gives an extended frequency range up to 800 MHz. The formulation for the equivalent common-mode voltage source is improved by taking into account the driving point impedance of the cable which behaves as a wire antenna. The radiated emissions estimated by the improved model match well with the values from 3D electromagnetic simulation of the original PCB with attached cable. It represents an improvement compared to earlier model by 11 dB at 400 MHz to 16 dB at 700 MHz for board size of 10 cm x 16 cm and cable length of 3 m. Similar improvements are obtained for other combinations of board size and cable length. The results show that the cable length is an important factor, in addition to the board area as suggested by earlier work, in determining the magnitude of the equivalent common-mode voltage source. Resonant of the wire antenna affects not only the radiated electromagnetic field but also the commonmode voltage source magnitude due to varying antenna impedances.

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Jia Haw Goh, Boon-Kuan Chung, Eng Hock Lim, and Sheng-Chyan Lee, "An Improved Model for Estimating Radiated Emissions from a PCB with Attached Cable," Progress In Electromagnetics Research M, Vol. 33, 17-29, 2013.
doi:10.2528/PIERM13061101

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