الفهرس 
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Abstract
Recently, Ultra-wideband (UWB) technology has become the modern wireless communication systems’ main demand. Consequently, it comes to be more popular after allocating of 3.1- 10.6 GHz for UWB applications which were announced by the Federal Communications Commission (FCC). Since then, many challenges have emerged that have faced the design of UWB antenna systems for many applications like in high-speed wireless devices. Therefore, countless research opportunities have emerged to meet the UWB antenna design challenges. Multiple-Input-Multiple-Output (MIMO) is considered to be an advantageous system to significantly increase the channel capacity without out the need for increasing neither the transmitted power nor the bandwidth. The achievement of diversity gain and array gain can be done by deploying two or more antennas in the transmitter and receiver. Thus, the reliability and spectral efficiency are improved. Due to the use of multiple antennas in MIMO systems, obtaining high isolation that is less than -16 dB between antenna elements is the MIMO systems’ main requirement. Therefore, the decoupling between the antennas must be high. Also, it must be compatible with many integrated circuits so it must have a small size. This thesis focuses on the design and the analysis of UWB-MIMO antenna system with a wide impedance bandwidth (3-18 GHz) which achieve the desired characteristics, enhance the performance and can be employed in many applications like radar and biomedical applications. This dissertation presents, a new proposed design of compact wide-band monopole antenna with dual notch band characteristics using Particle Swarm Optimization (PSO). The proposed antenna design is compact in size (32 mm × 38 mm × 1 mm) with a beveled ground plane for wide-band performance. It is fed by a microstrip transmission line, and it exhibits a monopolar far-field pattern in the radiating band. In order to prevent interference problems from existing nearby communication systems within the frequency range of 3- 20 GHz, an open loop slot etched is embedded in the radiating patch and a pair of U-shaped parasitic strips is inserted beside the feed line. This design cancels interferences due to Worldwide Interoperability for Microwave Access (WiMAX) (3.3 –3.8 GHz) and Wireless Local Area Network (WLAN) (5.1 – 5.8 GHz) frequencies while maintaining good gain over the UWB, X-band, and Ku band frequencies. Combined with the High-Frequency Structure Simulator (HFSS), the proposed dual band-notched antenna is designed and analyzed using the PSO algorithm. Simulation results show that the proposed antenna design has a very wide bandwidth covering the entire UWB, X-band, and Ku band frequency range (2.57 to 20 GHz), along with notch-bands in the WiMAX (3.3–3.8 GHz) and WLAN (5.1 –5.8 GHz) frequencies. Also, the results show good gain flatness, good impedance matching, and omnidirectional radiation patterns at almost all frequency bands of operation (3 GHz to 20 GHz). This reveals the effectiveness of the proposed antenna design in the applications of wide-band communication systems such as satellite communications.Also, in this work, a new design of wide-band MIMO antenna with dual band-notched characteristics and improved isolation is proposed for wireless applications operating over a frequency range of 3–18 GHz. The proposed UWB-MIMO antenna consists of 4 symmetric antenna elements and is fabricated on the Rogers RT/Duroid 5880 substrate with a dimension of 73 × 73 × 0.79 mm3. The proposed design achieves high isolation (> 20 dB) without using any decoupling elements, but it requires an orthogonal orientation of the four elements and an individual element size of 32 × 38 mm2. In order to prevent interference problems from existing WiMAX (3.3 –3.8 GHz) and WLAN (5.1 – 5.8 GHz) systems, a C-shaped stub is embedded in the radiating patch and a pair of U-shaped parasitic strips is inserted beside the feed line in the single element design. The effectiveness of the proposed UWB-MIMO antenna is demonstrated by investigating the measurement and simulation results and comparing them with other existing designs. The simulated and measured results show that the proposed design has a return loss less than -10 dB, mutual coupling less than -20 dB, and omnidirectional radiation patterns across the operating frequency range (3 to 18 GHz) excluding the two rejected bands. Also, the proposed UWB-MIMO antenna exhibits a high diversity performance in terms of the envelope correlation coefficient (ECC) < 0.0015 and channel capacity loss (CCL) < 0.3 bits/s/Hz. This reveals the effectiveness of the proposed UWB-MIMO antenna design in wide-band wireless applications such as satellite communications, radars systems, and microwave medical imaging.