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A compact monopole ultra wide band (UWB) antenna is analyzed and described with defect in ground plane.

In this paper, a flexible UWB antenna with band notched characteristics for high speed WLAN applications is presented. The flexibility of the designed antenna is achieved by developing the antenna on a flexible Teflon substrate. The proposed antenna primarily consists of a slot loaded octagonal star-shaped patch with a partial ground plane for wide operating bandwidth. A split ring resonator (SRR) based stop band filter is embedded in the ground plane to realize a rejection band characteristic to mitigate the interference impact from wireless local area network (WLAN) IEEE802.11n (5.725-5.825 GHz) band. The measured result shows that the suggested antenna operates over 3.25 to 13 GHz with a fractional bandwidth of about 120% with a peak gain of 6.7 dBi. The measurement results also confirm the presence of the rejection band from 5.7-6.2 GHz. Also, in terms of flexibility, the antenna provides high robustness in the performance for different types of bending conditions. The obtained results depict that the proposed antenna is suitable for mounting on all types of surface area with band rejection characteristics.

A compact dual wide-band multiple-input-multiple-output (MIMO) radiator is presented in this article. The MIMO radiator is developed on a 1.5 mm thick FR-4 substrate. The proposed structure is composed of U-shaped patches which are connected with small rectangular slit loaded circular rings and partial ground plane with chamfer edges. This arrangement is placed symmetrically at a far distance of 2.5 mm to achieve dual-operating bands with a high amount of isolation, radiation efficiencies and group delay between two radiators. The proposed compact dual-band radiator is resonating at 2.5/6.4 GHz frequencies and it provides isolation greater than 20 dB over the operating bands. The proposed design has a size of 0.45λ 0 × 0.291λ 0 × 0.03λ 0 mm and |S 11 | of about 41.25 dB and 14.58 dB. This design has a wide impedance matching in the range of frequencies from 2.38 GHz to 3.17 GHz & 5.14 GHz to 7.39 GHz with |S 21 | < 15 dB. The performance of diversity is calculated through diversity gain (DG) higher than 9.99, and Envelope Correlation Coefficient (ECC) which is less than 0.04 over the operating bands.

A small size neutralization line integrated flower-shaped MIMO antenna is designed and analyzed for sub-6 GHz type 5G NR frequency bands like n79 (4400-5000 MHz), n78 (3300-3800 MHz), n77 (3300-4200 MHz), and WLAN (5150-5825 MHz) applications. The novel approach of theory of characteristic mode analysis (TCMA) is introduced to provide physical insight of the designed structure and its characteristics behavior. Due to the suggested modifications in the geometry, the isolation among the patches is greatly increased.The overall miniaturized dimension of the MIMO antenna is 25 Â 40 mm 2 . The edge-edge spacing among the elements is 0.0233λ. The prototype antenna is fabricated and measured that shows good agreement compared with simulated results. The designed MIMO antenna without the presence of decoupling structure offers an isolation of 28 dB, gain of 3.6 dBi, and radiation efficiency of 69.7% at the resonant frequency. The proposed MIMO antenna covers a broad range of frequency band from 3.296 to 5.962 GHz with À10 dB impedance bandwidth of 2666 MHz and maintains a good isolation of greater than 50 dB for the entire operating band. The tested radiation efficiency and gain are 85.3% and 6.22 dBi at 3.5 GHz. Moreover, the diversity parameters of the neutralization line integrated MIMO antenna, that is, channel capacity loss (CCL) isolation, mean effective gain (MEG), total active reflection coefficient (TARC) diversity gain (DG), and envelope correlation coefficient (ECC), are analyzed and discussed in this article.

A tree-shaped graphene based microstrip MIMO antenna for terahertz applications is proposed.The proposed MIMO antenna is designed on a 600×300 μm 2 polyimide substrate. The designed MIMO antenna exhibits a wide impedance bandwidth of 88.14% (0.276 -0.711 THz) due to the suggested modifications in the antenna configuration. The MIMO design parameters like total active reflection coefficient (TARC), mean effective gain (MEG), envelope correlation coefficient (ECC) and diversity gain (DG), Channel capacity loss (CCL) are evaluated and their values are found within acceptable limits. The proposed MIMO structure offers MEG ≤ −3.0 dB, TARC≤ -10.0 dB, DG≈ 10 dB, CCL < 0.5 bps/Hz/sec and ECC < 0.01 at the resonant frequency. At the resonant frequency, the isolation between the radiating elements of the proposed MIMO is recorded as −52 dB. The variations in operating frequency and S-parameters are also analyzed as a function of the chemical potential (μc) of the graphene material.The parametric analysis, structural design evolution steps, surface current distribution, antenna characteristics parameters and diversity parameters are discussed in detail in this paper. The designed MIMO antenna is suitable for high speed short distance communication, video rate imaging, biomedical imaging, sensing, and security scanning in the THz frequency band.

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