Two major objectives are concerned in this paper. On one hand, a multiplicity of typical methodologies available for achieving dual-frequency operation for microstrip patch antennas are summarized and classified into three categories, based on their intrinsic mechanisms. On the other hand, by employing the dual-frequency solutions, microstrip patch antennas are applied to the mobile handsets of the third-generation IMT-2000 system. Two novel microstrip patch antennas with broadband property and miniaturized size have been proposed and discussed theoretically and experimentally. Only a single simply-slotted patch, either semi-disc or square, is introduced in each of the two probe-fed antennas. Both antennas exhibit the impedance bandwidths (return loss · −10 dB) of 25.6% and 34.4% respectively, which would be suitable for the practical application of the IMT-2000 mobile handsets.
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