The dual-mode square loop resonator with Hilbert-curve perturbation is introduced for multiple resonances and wideband filters in this letter. To obtain low insertion loss (0.5 dB), high out-of-band rejection level ( 49 51 dB) and wider band (BW 65%) filters, iterative Hilbert-curve perturbation and space-filling technique are proposed. Multiple resonances that included dual modes, third, fourth, and fifth order resonances are presented with resonance splitting plots. Surface current distributions with multiple resonances and transmission zeros are presented and discussed.

parts. The input resistance of the tag antenna increases in proportion to the squared mutual coupling in (1). As the distance d p between the parts increases, the mutual coupling decreases. As the mutual coupling decreases, the resistance of the antenna decreases. Therefore, the input resistance of the tag antenna can be easily adjusted.A number of tag chips are fabricated with various impedances according to the chip providers. Therefore, this method is convenient when designing tag antennas. CONCLUSIONIn this article, to understand the physical operation of the proposed tag antenna, we have presented an analysis and an equivalent circuit model of the simplified structure. We have validated the model through a comparison between simulation and calculation of the equivalent circuit. For use in plastic lids, we have presented a compact (diameter: 0.08, 26.4 mm) wideband (102 MHz) tag antenna for UHF RFID. Using an inductively coupled feeding method, a wide bandwidth and a simple matching technique can be obtained, while size reduction can also be achieved using meander lines. The prototype antenna can be operated continually in the UHF RFID frequency range. CASCADED DUAL-MODE SQUARE-LOOP RESONATORS USING HILBERT-CURVE PERTURBATION FOR WIDE BANDPASS FILTER APPLICATIONS