Cerium oxide (CeO 2 ) filled polytetrafluoroethylene (PTFE) composites prepared by powder processing technique for microwave substrate application is presented in this paper. The PTFE is used as the matrix and the dispersion of CeO 2 in the composite is varied up to 0.6 by volume fraction, and the dielectric properties were studied at 1 MHz and microwave frequencies. The relative permittivity and dielectric loss increased with increase in CeO 2 content. For 0.6 volume fraction loading of the ceramic, the composite has e r of 5 and tan d of 0.0064 at 7 GHz. Different theoretical approaches have been employed to predict the effective permittivity of composite systems and the results were compared with that of experimental data. The serial mixing model shows good correlation with the experimental results.

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A compact dual-band uniplanar antenna for operation in the 2.4=5.2=5.8 GHz WLAN=HIPERLAN2 communication bands is presented. The dual-band antenna is obtained by modifying one of the lateral strips of a slot line, thereby producing two different current paths. The antenna occupies a very small area of 14.5 Â 16.6 mm 2 including the ground plane on a substrate having dielectric constant 4.4 and thickness 1.6 mm at 2.2 GHz. The antenna resonates with two bands from 2.2 to 2.52 GHz and from 5 to 10 GHz with good matching, good radiation characteristics and moderate gain.Introduction: With the tremendous increase in the number of laptops and other portable devices the need for wire-free communication, devoid of wires and interconnections, has become inevitable. The availability of the ISM band as licence free has paved the way for the design of various communication devices working at these frequencies for short-range communication. This has created great demand for suitable antennas working at these frequencies. Also, with the process of miniaturisation in full swing, greater emphasis is given to compactness. Of available designs, planar antennas are preferred owing to advantages such as small volume, ease of fabrication and flush mounting facility. Various types of antenna designs complying with these requirements have been reported. The printed double T monopole presented in [1] consists of two stacked T shaped monopoles for achieving dual resonance in the 2.4=5.2 GHz WLAN bands using a microstrip feed with a 50 Â 75 mm 2 ground plane. The planar monopole antenna [2] uses a shorted parasitic inverted L wire to obtain resonances in the 2.4=5.2=5.8 GHz bands. Compared to other designs, uniplanar antennas have advantages such as lack of soldering points, easy fabrication, easy integration to MMICs and single metallic layer structure. The compact dual-band antenna for ISM applications reported in [3] consists of an asymmetric dipole having a total area of 15 Â 40 mm 2 and dual band is produced using the unbalanced current distribution in the asymmetric arms. The CPW fed dual-frequency antenna mentioned in [4] produces dual resonances connecting two monopoles to a single feed line.In this Letter we propose a compact uniplanar antenna for WLAN applications. The proposed antenna design is obtained by modifying one of the lateral strips of a slot line. Ansoft HFSS is used for simulation and analysis of the structure. The proposed antenna resonates with two bands from 2.20-2.52 GHz and from 5.03-10.09 GHz which is wide enough to cover the IEEE 802.11b=g (2.400-2.484 GHz), GHz) and HIPERLAN2 (5.47-5.725 GHz) communication bands. Moreover, the antenna has a simple structure, occupies a very small area of 14.5 Â 16.6 mm 2 and can be easily printed into circuit boards.

A planar monopole antenna suitable for broadband wireless communication is designed and developed. With the use of a truncated ground plane, the proposed printed monopole antenna offers nearly 60% 2:1 VSWR bandwidth and good radiation characteristics for the frequencies across the operating band. A parametric study of the antenna is performed based on the optimized design, and a prototype of the antenna suitable for 2.4‐GHz WLAN application is presented. The antenna can be easily integrated into wireless circuitry and is convenient for application in laptop computers. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 871–873, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21503

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