Switching noise picked up by a planar dipole antenna mounted near integrated circuits

For applications in which antennas are located near or in integrated circuits (ICs), the switching noise from digital circuits can interfere with the operation of antennas. This paper presents a study of the switching noise picked up by a planar dipole antenna from a divide-by-128 IC located near the antenna. To develop understanding of the measurement results, a lumped-element simulation model has been developed. Quantitative agreements between the measurements and simulations for numerous experiments have been obtained. The measurements indicate that by selecting the signal frequency on the antennas much greater than the circuit frequency, the immunity from switching noise can be improved. The measurements also showed that circuits such as buffers are relatively noisier, and emanate more noise at higher operating frequencies. Finally, the measurements showed that using antennas with a differential or balanced feed structure can substantially reduce the coupling of switching noise (/spl sim/20 dB) which is mostly common-mode in nature.