A new compact multiple-input multiple-output (MIMO) ultra-wideband (UWB) antenna array is presented. The antenna array initially consisted of two monopoles placed side by side at a distance of 4 mm. A strong mutual coupling was observed so the design was modified by rotating the second radiator at 90° at a distance of 1 mm. Wideband isolation is achieved by exploiting polarisation diversity of antenna elements. Simulation in HFSS and printed prototype results validate the high isolation, over 21 dB on the entire 2.5-12 GHz frequency range. A prototype was fabricated on a low loss substrate of Rogers TMM4 measuring 23 × 39.8 mm2. To evaluate the diversity performance, the envelope correlation coefficient was calculated resulting below -20 dB, thus ensuring good diversity performance. The compactness of the proposed UWB-MIMO design is finally compared against alternative solutions already present in the literature
Abstract-This work presents the analytical solution of vector wave equation in fractional space. General plane wave solution to the wave equation for fields in source-free and lossless media is obtained in fractional space. The obtained solution is a generalization of wave equation from integer dimensional space to a non-integer dimensional space. The classical results are recovered when integer-dimensional space is considered.
Presented are two different frequency reconfigurable ultra-wideband multiple-input multiple-output (MIMO) antenna array designs capable of rejecting on-demand all WLAN communications in the 4.8 to 6.2 GHz range. Both arrays consist of two monopole UWB radiators placed orthogonally with respect to each other to introduce polarisation diversity and a quarter-wave stub connected to the ground plane via pin diodes is used to introduce the on-demand band rejection feature. One array design has separate ground planes and the other has two ground planes connected with a printed conductor (i.e. shared). For both cases, an isolation better than 20 dB between the elements is achieved in the 2 to 12 GHz frequency range with simulations and a manufactured prototype.
This paper presents the GA optimization of a CPW fed UWB circular ring monopole antenna with modified ground plane. The antenna design parameters have been examined through HFSS parametric simulation and GA optimization processes. Antenna prototypes have been designed and tested and a good agreement between numerical simulation and experimental results has been obtained. The measured S 11 results showed that the non-optimized antenna impedance bandwidth is 4.2:1 while for the GA optimized prototype it increased to 4.8:1. The measured gain is about 3 dBi at 5.8 GHz. In addition, the presented measured and simulated radiation pattern results indicate typically omnidirectional radiating characteristics over the 2.75 GHz to 7 GHz frequency range of the proposed antenna, confirming that it is a good candidate for UWB and cognitive radio spectrum sensing applications.
Abstract-Reflection from a planar DB interface placed in chiral and chiral nihility medium is studied. No difference between the two cases, regarding reflection chracteristics, is noted. No reflected backward wave is produced for DB interface placed in chiral nihility metamaterial. In this regard, DB interface may be considered as first known perfect reflector interface which yields non zero power when placed in chiral nihility medium.
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