The concept of a dual‐band dual‐circularly‐polarized antenna for GPS (Global Positioning System, 1575 MHz) and DAB (Digital Audio Broadcasting, 1452–1492 MHz) system is proposed. The generation of circular polarizations and reduction of an overall antenna‐element dimension are achieved by placing a partially filled high‐permittivity dielectric bar under the radiating edges of the patch. A patch‐antenna element based on the proposed method and a conventional antenna element with an air layer filling the whole volume under the patch are compared, and antenna‐dimension reduction of more than 30% is achieved using the proposed method. Finally, a sector‐type antenna is designed by employing the space‐diversity technique with the proposed antenna elements. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 43–46, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20896
IntroductionAs is well known, a dual-band antenna is better than a wideband antenna if both of them are required to cover two frequency bands that are far away from each other. Consequently, the researches on dual-band shorted patch antennas are increasing dramatically. In the literature, several methods have been reported to develop this type of antenna. They involved cutting a special slot [1] and using a stacked structure [2] on the traditional quarter-wave shorted patch antenna. Although the new antenna has dual-band characteristic, its impedance bandwidth of each frequency band is narrow (2-10%). In order to tackle this problem, a bandwidth widening technique is utilized. By using proximity-coupled feeds to excite two quarter-wave shorted patches that are in stacked configuration, wide impedance bandwidths of 47-54% are obtained in two frequency bands [3][4]. Nevertheless, they will be reduced to around 10% if the height of the antenna is low (<0.05λ L ). Actually, most of the wideband techniques in the literature are not effective for the low profile antennas. In the last year, a wideband low-profile antenna is proposed. By folding the open (or radiating) edge of a quarter-wave shorted patch antenna backwards, wide impedance bandwidth of 29.4% is acquired at a low profile of 0.046λ C [5].In this paper, a dual-band folded shorted patch antenna with a low profile of 0.05λ L and a small size of 0.25λ L x 0.36λ L is presented. It is operated at both TM 10 mode and TM 30 mode, which is developed by introducing two slots to the patch of our previously proffered folded shorted patch antenna [5]. With the proper choose of the sizes and the positions of these slots, wide impedance bandwidths of 20.4% and 32.2% are measured at the lower and the upper bands, respectively. Antenna performance procured by the measurement is also compared with the simulation and good agreement is observed. Moreover, details of the antenna design are given. Antenna StructureThe geometry of the proposed antenna is shown in Fig. 1. This antenna is mounted in the middle of a rectangular ground plane. It consists of a rectangular patch that is supported by a foam substrate above the ground plane. Along the xaxis, this patch has one end shorted to the ground and the other end folded backwards. The folded part is supported by another foam substrate over the main part of the patch. Also, two slots with different sizes are etched on different 978-1-4244-2042-1/08/$25.00 ©2008 IEEE positions of the patch. Moreover, a coaxial feeding probe and a shorting post are connected to the main part of the patch. Let λ L be the free space wavelength at 0.883GHz. For this antenna, the size of the ground plane is 280.2mm x 318mm (0.82λ L x 0.94λ L ). The thicknesses of the patch and the ground plane are 0.2mm and 2mm, respectively. Dielectric constant of the foam substrate is 1.1. The other dimensions are listed in Table 1 in details. In fact, the lateral size (or projection area) of this antenna is 36% that of a regular half-wave square patch antenna with the...
8510C network analyzer. The frequency responses of the EM simulation and measurement are shown in Figure 4(b). The measured results of the BPF have S 11 of 19 dB, S 21 of 0.8 dB, and 3-dB fractional bandwidth (FBW) of 0.04 at 1.575 GHz and S 11 of 27 dB, S 21 of 1 dB, and FBW of 0.04 at 5.7 GHz. The measured frequency responses of the passband are closely matched the simulated results, thus verifying the theoretical prediction of the passband. CONCLUSIONThe compact dual-band BPF using diverse coupled /4 resonators has been presented for GPS (1.575 GHz)/WLAN (5.7 GHz) application. Detailed design procedure which has been described. By adjusting the impedance ratio and physical length of the SIRs, multiple resonant modes can be created and are suitably arranged for achieving dual-band performance with widely frequency range. Overall size of the BPF is around 0.19 g ϫ 0.11 g . Good agreement with responses of electromagnetic simulation and measurement is compared.ABSTRACT: A meandered loop antenna with the modified ground plane in conjunction with the balanced structure is proposed to mitigate the degradation of antenna performance when the handset is directly held by the user's hand. The antenna efficiency for a dual frequency band (AMPS and PCS) is studied under the influence of the user's hand.
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