Design and analysis of a single-feed arrangement of stacked rectangular patches is proposed, which is capable of providing circular polarization along with broadband performance. An antenna is designed on a glass epoxy FR-4 substrate with overall thickness of the structure less than 8 mm or 0.11 0 . The patch area of the corner truncated driven patch is marginally smaller than that of a parasitic patch to achieve improved performance. Both driven and stacked patches have narrow slots of unequal size in a way that their centers lie one over the other. The locations of the feed point, the amount of corner truncation of the driven patch, and the size of slots on both the driven and the stacked patches are optimized. Axial ratio bandwidth better than 11% and impedance bandwidth better than 27% may be achieved with the proposed geometry. Measured gain and axial ratio variations of the proposed antenna with frequency are compared to simulated results for better understanding. The measured E-and H-plane radiation patterns in the entire impedance bandwidth are identical in shape, and the direction of maximum radiations is normal to the patch geometry. In the entire axial ratio bandwidth range of the proposed antenna, the E-plane left circularly polarized patterns are nearly 15 dB higher than the corresponding right circularly polarized patterns.Index Terms-Axial ratio bandwidth, broadband, circularly polarized, radiation patterns, stacked microstrip antenna.

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shunt inductance causes the LH branch in Figure 1 to be upshifted, resulting in the upshifted resonance frequency in Figure 7(b). It is observed that the radiation loss of the CRLH filter is improved by adding via holes and the bandwidth is increased from 5.7 to 8.2%. The insertion loss of the CRLH filter with additional via holes is measured to be 1.1 dB. CONCLUSIONSThe second-order CRLH-coupled line bandpass filter using the first negative mode is proposed. To design a CRLH bandpass filter, the design equations are derived. The even-mode and oddmode impedances of a CRLH-coupled line are calculated versus the width and separation of a coupled line section. The resonators of a filter are implemented by four unit-cells supporting the first negative mode and the size is reduced by 53%, compared with those of a conventional filter. An insertion loss of a CRLH filter is suppressed by adding via hole in the end of resonators. ACKNOWLEDGMENTSThis work was supported by the IT R&D programme of KEIT (Korea Evaluation Institute of Industrial Technology; 2009-F-033-01, Study of technologies for improving the RF spectrum characteristics by using the meta-electromagnetic structure.)ABSTRACT: The design and performance of a stacked arrangement of edge truncated elliptical patch and conventional circular patch antennas is proposed in this communication which is capable in providing improved impedance bandwidth with circularly polarized radiations. Both patches are designed on two independent glass epoxy FR-4 substrates separated by thin air gap. The two patches are placed one over other in such a way that their centers also lie one over other. The size of upper circular patch is marginally larger than lower edge truncated elliptical patch which is acting as driver patch. Proposed arrangement of patches yield measured impedance bandwidth as high as 0.94 GHz with measured axial ratio bandwidth close to 3.33%. The measured gain and axial ratio results of proposed arrangement on patches are compared with simulated results. Co and cross polar patterns suggest that radiations are right circularly polarized in nature. V C 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:947-952, 2011; View this article online at wileyonlinelibrary.com.Figure 13 (a) E plane E left and E right patterns of stacked antenna at frequency 2.93 GHz (b) H-plane E left and E right patterns of stacked antenna at frequency 2.93 GHz (c) E plane E left and E right patterns of stacked antenna at frequency 3.02 GHz (d) H-plane E left and E right patterns of stacked antenna at frequency 3.02 GHz. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

A novel dual-frequency broadband design of a single-layer single-feed circular microstrip antenna with an off-centered Y-slot is demonstrated in this communication. By selecting a suitable location of the Y-slot in the circle, the proposed antenna on glass epoxy FR-4 substrate not only resonates efficiently at two closely spaced frequencies (2.736 and 2.868 GHz) but also offers improved bandwidth (210 MHz or 7.5%) in comparison with a conventional circular microstrip patch antenna (2%). From the measured results, almost identical broadside radiation patterns are obtained at two resonant frequencies, and the variation of less than 1 dBi in gain values is achieved in the frequency range where broadband behavior is observed.