DESIGN AND ANALYSIS OF MICROWAVE COMPONENTS FOR MIMO COMMUNICATION SYSTEM

Abstract

Wireless communication demands better channel capacity with a high data rate in the modern era. To fulfill these demands, the MIMO-communication systems are developed that use manifold antennas for transmitter and receiver end. MIMO is a state-of-art technology that improves the reliability of the communication systems by utilizing the diversity technique to mitigate the multi-path fading issues, where signals may come together belligerently at the receiver. Improve spectral efficiency is achieved by the total transmitted power spreading over the antennas. Thus, MIMO can increase channel capacities as well as the reliability of the communication system without sacrificing extra transmitted power or power spectrum. Several MIMO antennas have been designed in the literature to improve their characteristics in terms of impedance bandwidth; miniaturization & isolation improvement. The MIMO-communication systems with THz range are required for high data speed in Terabit/sec (Tbps). Also, it is providing very high throughput per device (from multiple Gbps to several Tera-bps) including per area efficiency (bps/km2). It is also predicted that the world monthly traffic in smartphones will be about 40 Peta-bytes in 2021, so the demand for MIMO antennas will be increased in the future. In this thesis, various microwave components for the MIMO wireless communication system has been analyzed and designed. Three major components designed and analyzed in this thesis are 1. MIMO Antennas 2. Metamaterial Absorber 3. UWB Microwave Filter MIMO Antennas: In this thesis, various MIMO antennas for UWB, SWB, and Multiband applications have been designed. Various decoupling techniques to avoid the v interference between antenna elements are designed which enhancing the diversity parameters with improved channel capacity for modern wireless applications. To mitigate the interference between bands and to improve the reliability of the signals, a notch characteristic has been introduced. SAR analysis also discusses in this thesis with the human head and confirms that proposed MIMO antennas are in the acceptable range with 1g and 10g of bio tissues given by FCC and EU for mobile and other near field applications. All the MIMO antennas with different frequency characteristics are discussed in Chapter-2 to Chapter-6. Metamaterial Absorber: To improve the isolation level in MIMO antennas as well as to minimize the Radar Cross Section (RCS) and Electromagnetic Interference (EMI), a design of multiband metamaterial absorber (MMA) for X-band applications has been suggested. This MMA provides three high absorbance bands at 8.2GHz, 9.45GHz, and 12.45GHz with 99.4%, 96.4%, and 91.25% absorbance respectively. Proposed MMA is polarization insensitive in all three bands with minimum RCS -33.2dBm2. This absorber structure has designed on FR-4 (4.4) substrate having tanδ = 0.02 with unit cell dimension 20×20×1mm3. So the proposed absorber is found appropriate for stealth aircraft, RCS and EMC reduction, isolation in MIMO antenna, imaging, and sensing in the X-band applications, discussed in Chapter-7. UWB Microwave Filter: In this research work, the design of the UWB filter with extended stopband characteristics by using a parallel-coupled line, open-ended line, multimode resonator (MMR), and defected ground structure (DGS) has been presented. This filter provides good return and insertion loss in the passband (3.1-10.6GHz) as well as stopband (10.8-18GHz). The group delay of the filter is almost constant throughout the passband. Detailed analysis of supportive coupled, feeding, and the open-ended line is vi verified with equivalent circuits. The prototype of the filter is compact as 22×20mm2 with a 109% fractional bandwidth. The proposed filter is suited for recent weather reporting Radar, Imaging, and Satellite receiver systems because simulated results have good agreement with measured results as discussed in the Chapter-8. RESEARCH OBJECTIVES: The major objectives of the research work are listed below: 1. To enhance the impedance bandwidth of the MIMO antenna and microstrip filter for various wireless applications. 2. To design and analyze the circularly polarized MIMO antenna for GPS, vehicular and 5G applications. 3. To enhance the isolation between the various elements of the MIMO antenna, to improve the various diversity parameters. 4. To enhance the specific absorption ratio (SAR) performance of the MIMO antenna for a handhold and mobile applications. 5. To design a Metasurface for stealth and isolation improvement in MIMO antenna applications.