![]() ![]() The designed antenna has resonances at the frequencies of 6, 8, 10.8, 15.8 and 18.8 GHz. A good isolation of more than 15 dB is achieved. The differences between the S 11 and S 22 characteristics are due to asymmetrical structure with respect to substrate. In addition to mesh size, it is also important to mention that in CST MWS the structure can be solved in single pass instead of solution for different frequency spectrum, i.e. These discrepancies can be attributed to the different mesh size suitable for numerical techniques on which the simulators are designed. From Figure 6 and Table 3, it is observed that there are some discrepancies among the two simulation results. The quantitative analyses of bandwidth for two antenna elements used in designed antenna structure are presented in Table 3. The variations of simulated scattering parameters with frequency are demonstrated in Figure 6. The designed diversity antenna structure is simulated by using HFSS and CST MWS simulators. Finally, it is concluded with major findings of this chapter. In the following sections, antenna design description is followed by discussion of frequency domain analysis results, time domain analysis results and diversity performance parameter calculation. Two identical copies of this antenna structure are arranged orthogonally to achieve good interport isolation and orthogonal polarization diversity performance without affecting the UWB performance. The bandwidth of the antenna structure is enhanced by loading the coplanar ground planes with a quarter wavelength long rectangular notches. In this chapter, a compact CPW-fed UWB fractal antenna with polarization diversity performance is presented. Fractal antenna structures have a compact size and wideband performance due to properties of self-similarity, space filling and effective energy coupling properties. However, the application of those available structures is limited due to their large dimensions, multilayer structure, complex feedline, complex geometries, etc.Īmong the various bandwidth enhancement techniques, the use of fractal geometries is proven to be a good method. ![]() Some UWB polarization diversity antennas are already reported in the literature. An UWB system with polarization diversity technique has potential applications in advanced instruments used for microwave imaging, radar and high-speed data transfer. These alternate techniques involve the use of two or more antenna elements with different radiation patterns. To overcome this drawback, other techniques such as pattern or polarization diversity are investigated. This large space requirement limits the use of this diversity method. In a spatial diversity scheme, a large separation (compared to wavelength) between the antennas is used to achieve decoupling between signals. An increase in correlation reduces the combining efficiency. įor good diversity performance, the received signals should have very low correlation between them. The detailed description of diversity combining techniques is available in. In a diversity scheme, the power or signal-to-noise ratio of the received signal is optimized by the selection or combining of output signals in several ways like selection combining, equal gain combining or maximal ratio combining. Several types of diversity, such as space/spatial, pattern and polarization diversity, have been already proposed and implemented to receive multiple signals. This multipath fading results into the degradation of signal-to-noise ratio (SNR) and channel capacity.Īn effective method to resolve these multipath fading issues is the incorporation of antenna diversity techniques in wireless communication systems. ![]() In a highly dense and dynamic environment, the UWB systems suffer from multipath fading due to reflection and diffraction. After this allocation, ultra-wideband has received attention from wireless communication experts owing to its advantageous features like wider bandwidth, low cost, low susceptibility to multipath fading, reduced probability of detection and intercept and potentially high data rates. In 2002, FCC allocated the unlicensed frequency spectrum from 3.1 to 10.6 GHz for ultra-wideband (UWB) technology. ![]()
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