An effective technique utilizing neutralization lines to increase the isolation of a compact two-element dual-frequency microstrip antenna array is proposed in this paper. Two neutralization lines connect the two elements at the edge of each radiating patch. The positions and lengths of the two neutralization lines are studied to get the best performance of element isolation. A prototype of the proposed design was fabricated to validate the results. The measured results agree well with the simulated ones. It is shown that an increase of about 25 dB at the lower frequency and that of 17 dB at the upper frequency in isolation between the two antennas have been achieved.
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