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were used to construct the MIMO antenna system for Wibro service. To obtain high isolation between antenna #2 and antenna #3, a hairpin resonator was added between the two antenna elements. The total size of the proposed multiantenna is 40 mm  7 mm  5 mm. The designed multiantenna has measured peak gains of 3.8 dBi at the WCDMA lower band, 1.4 dBi at the WCDMA higher band, 1.2 dBi for antenna #2, and À0.95 dBi for antenna #3 in the Wibro band. The isolation (S 32 ) in the Wibro band is lower than À17 dB.Although the two MIMO antenna elements have different directivities, their radiation patterns resemble each other. Further research will examine the following: (1) gain enhancement at the WCDMA higher band (Rx band) and the Wibro band and (2) equalization of the performance of Wibro MIMO antenna elements. ABSTRACT: In this article, a novel and compact hairpin bandpass filter (BPF) using defected ground structure (DGS) is discussed. By placing a novel cascaded z-slot DGS at the location of the input and output port, the first spurious passband can be rejected. The elaborate analysis of the z-slot DGS has been given. The equivalent circuit of the z-slot and how the dimension affects the frequency response are presented. In addition, as the DGS is etched on the backside of the substrate, no extra size is added to the final layout. The experimental results demonstrate that this filter has low insertion loss, small size, and with a rejection level of more than 35 dB for the first spurious passband. The measured results of the proposed BPFs are in good agreement with the simulated ones.

This paper presents a planar monopole backed with a 2×1 array of Electromagnetic Band Gap (EBG) structures. The reflection phase of a single EBG unit cell has been studied and exploited towards efficient radiation of a planar monopole antenna, intended for wearable applications. The shape of the EBG unit cell and the gap between the ground and the EBG layer are adjusted so that the antenna operates at 2.45 GHz. The proposed antenna retains its impedance matching when placed directly upon a living human subject with an impedance bandwidth of 5%, while it exhibits a measured gain of 6.88 dBi. A novel equivalent array model is presented to qualitatively explain the reported radiation mechanism of the EBG-backed monopole. The proposed antenna is fabricated on a 68×38×1.57 mm 3 board of semi-flexible RT/duroid 5880 substrate. Detailed analysis and measurements are presented for various cases when the antenna is subjected to structural deformation and human body loading, and in all cases the EBG-backed monopole antenna retains its high performance. The reported efficient and robust radiation performance with very low specific absorption rate (SAR), the compact size, and the high gain, make the proposed antenna a superior candidate for most wearable applications used for offbody communication.

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