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A broadband dual-polarised antenna with four end-to-end folded dipoles and a U-shaped ground is presented. Stable and symmetric radiation patterns at slanted +458 polarisation have been obtained within the band 1.71 -2.17 GHz. Measurements show two linear polarisations with an isolation of more than 30 dB over the operating frequency band. A return loss less than 214 dB is achieved and the measured cross-polar level is 23.5 dB below the co-polar level within the above-mentioned band.Introduction: There is continuing need for dual-polarised broadband antennas owing to the explosive growth in broadband wireless communication systems. The ideal base station antenna for use in wireless communication would have broadband performance, high isolation, high front-to-back ratio, low cost, easy assembly and the required appropriate beam width for cell sector design. Several dual-polarised antennas have been suggested [1][2][3][4][5]. These antennas [1-3], with aperture coupled feed, generate high back-radiation and involve several layers that result in difficulty in achieving the required cost targets owing to the use of high cost printed circuit boards. The use of a bowtie patch with cross dipoles [4] or a probe fed stacked patch with slots loaded [5] leads to broadband performance and high isolation between the two polarisation ports, but results in a complex structure and has the drawback of high cross-polar levels compared to the peak co-polar levels.In this Letter, a broadband dual-polarised element with four end-to-end folded dipoles and a U-shaped ground is proposed for the existing DCS, PCS and 3G mobile communication systems operating at 1.71-2.17 GHz. The antenna exhibits dual linear polarisations at slanted +458 with an isolation of more than 30 dB when two orthogonal ports are simultaneously excited. Measured and simulated results show that the proposed antenna element is suitable for the systems mentioned above.

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A compact circularly polarized (CP) microstrip antenna with inserted nine cross slots is proposed to reduce the size and widen the beamwidth. The antenna is operated at 1.268 GHz, and built by using a substrate with a coaxial probe feed. The impedance bandwidth (VSWR < 2) is 1.5% and the 3 dB axial ratio bandwidth is 0.52%. The measure gain is 4.5 dBi and beamwidth is about 110 •. The measured results for the compact CP antenna with embedded cross slots size shows that the resonate frequency is significantly lowered from 1.951 GHz to 1.268 GHz, corresponding to a 35% antenna size reduction compared with the one without any slot.