BACK PAGE A Dipole Moment

Considering dipole moments during the design of circuit boards could yield further miniaturisation through removing the need for EMI shielding

result in the cost savings obtained by minimising shielding. The researchers’ paper was published for a high-speed communication and semiconductor industry conference earlier this year.


CONSUMER ELECTRONICS APPLICATION In their paper, the Missouri researchers studied a popular consumer electronic device and its multiple digital sub-systems, including a central processing unit, a double data rate (DDR) memory chip and Wi-Fi antennas. They proposed a way to reduce radio-frequency interference, or RFI, in the device without impeding signal integrity.

One of the paper’s authors is Dr Jun Fan, the director of the EMC Lab in Missouri as well as Professor of Computer Engineering. He believes that boards with the new design clearly reduce RFI.

Shielding, or blocking

an electromagnetic field with barriers made of conductive or magnetic materials, is the approach most commonly used to reduce RFI in electronic products. However, shielding is costly and adds to the bulk and weight of a board, thereby introducing limits on miniaturisation. Therefore, the researchers propose making layout changes to the board itself, based on analysis of “dipole moments”. “The analysis of dipole moments could possibly remove the need for shielding for some electronic products, thus enabling a cost-saving possibility,” says Fan.

❱ ❱ Academics believe that considering the dipole moment in circuit geometry can help to reduce the requirements for on- board shielding

DIPOLE MOMENTS A dipole moment refers to a measure of separation of positive and negative electrical charges within a system. At radio frequencies, a dipole moment can be used to describe electromagnetic radiation from certain circuit structures that act as unintentional antennas and cause interference, according to Fan. By studying the dipole moments created in such designs and modelling them in alternative circuit designs, such radiating antennas can be avoided or reduced. At Missouri, Dr Fan and co-author Dr Chulsoon Hwang, have been studying the phenomenon of dipole moments and their effect on RFI for some time and have previously produced a paper on “Accurate and fast RFI prediction based on dipole moment sources and reciprocity.”

28 /// EMC Testing Vol 2 No. 1 &

cademics at the Missouri University of Science and Technology have been studying the effects of circuit geometry on radio frequency interference (RFI) in a bid to reduce the requirements for shielding. Researchers at the Electromagnetic Compatibility (EMC) Laboratory of the university have proposed an approach that could

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