Theses and Dissertations
Permanent URI for this collectionhttp://ir.daiict.ac.in/handle/123456789/1
Browse
7 results
Search Results
Item Open Access Compact Circularly Polarized Tri-, Dual- and Single-Band Dielectric Resonator Antennas(Dhirubhai Ambani Institute of Information and Communication Technology, 2021) Chaudhary, Pankaj Prabhubhai; Ghodgaonkar, Deepak K.; Gupta, SanjeevThe Dielectric Resonator Antennas (DRAs) have received wide attention due to low loss, high radiation efficiency, small size, wider bandwidth and simple feed network as compared to the microstrip antennas. Microstrip antennas have many challenges such as low radiation efficiency, high conductor loss, poor polarization purity, multiple frequency bands and multiple polarizations with a large footprint area of the antenna, low gain and narrow bandwidth. The existing design techniques for tri-, dual- and single-band DRAs reported in the literature have various limitations such as ground plane area of DRA, volume of Dielectric Resonator (DR) and DRA not sufficient for small physical area applications, realization of Circular Polarization (CP) over large ground plane area and unavailability of single DR geometry with multi-mode for multi-band applications. In this thesis, compact CP tri-band (L5, L1 and S-bands) staired Rectangular Dielectric Resonator Antennas (RDRAs) (two port, single port) using tri-, dualand single-sections Wilkinson Power Dividers (WPDs) with wide-band 90◦ phase shifters are designed, analyzed, fabricated and tested. These tri-band RDRAs are used in Indian Regional Navigation Satellite System (IRNSS) and GPS-Aided GEO Augmented Navigation (GAGAN) applications. The ground plane footprint areas of tri-band RDRAs and volumes of staired Rectangular Dielectric Resonators (RDRs) are significantly reduced by using high dielectric constant of DR materials and high dielectric constant of dielectric substrates. The broadside radiation patterns of triband RDRAs are produced by TEy 111, TEy 113 and TEy 112 modes for L5, L1 and S-bands, respectively. Various parameters of tri-band RDRAs like return loss, Right Hand Circularly Polarized (RHCP) - Left Hand Circularly Polarized (LHCP) radiation patterns, RHCP gains and axial ratios are analyzed and measured. Compact CP dual-(L5 and L1) and single-band RDRAs are designed, analyzed, fabricated and tested using feed networks of dual- and single-sections WPDs with wide-band 90◦ phase shifters. The miniaturized volumes of RDRs and ground plane areas of dual- and single-bands RDRAs are achieved using high dielectric constant of DR materials and high dielectric constant of dielectric substrates. The broadside radiation patterns of dual-band RDRA are produced by TEy 111 and TEy 113 modes for L5 and L1-bands, respectively. The TEy 111 modes are produced in three single-band RDRAs for L5, L1 and S-bands. The simulated and measured parameters of dualand single-band RDRAs are return loss, RHCP-LHCP far field radiation patterns, RHCP gain and axial ratio. The design and analysis of finite ground plane single-band CP RDRAs using WPD with wide-band 90◦ phase shifter for L1 and L5-bands are carried out by using high dielectric constant of DRs and dielectric substrates. Also, the effect of different radii of finite circular ground planes of single- and dual-band RDRAs are investigated by using the Method of Moments (MoM). The effect of different radii of circular ground plane on single- and dual-band RDRAs are analyzed for return loss and gains.Item Open Access Computational investigation of patch antennas in plasma environment(Dhirubhai Ambani Institute of Information and Communication Technology, 2016) Vyas, Hardik; Chaudhury, Bhaskar; Gupta, SanjeevMicrostrip antennas are extensively used in spacecraft systems and other applicationswhere they encounter a plasma environment. A detailed computationalinvestigation of change in antenna radiation properties in the presence of plasma has been done. The study shows antenna properties such as the resonant frequency,return loss, radiation properties and the different characteristics of the antenna changes when it is surrounded by plasma. Particular focus of the work is to understand the causes behind these changes by correlating the complex propagation constant in the plasma medium, field distribution on the patch and effective dielectric of the antenna substrate with antenna parameter variations. Besides this, the study also provides important insights to explore the possibilities of designing frequency reconfigurable microstrip antenna where the substrate can be replaced with plasma and important antenna characteristics can be controlled by varying the plasma density. Plasma can be the potential frequency reconfigurable element since its dielectric properties can be varied by varying plasma density. It has high microwave power handling capability which makes it preferrable over current semiconductor technologies in situations such as electromagnetic attacks.Followed by this, minimization of power required to sustain plasma in a reconfigurable antenna has been done by using microplasma technology.Item Open Access Dual-band and shorted microstrip patch antenna design for communication system applications(Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Rai, Karishma K.; Gupta, SanjeevDual-band and miniaturized microstrip patch antennas are in much demand due to their small size, light weight and planar configuration. In this thesis, an attempt is made to design and analyze miniaturized microstrip patch antennas, patch arrays and dual-band microstrip patch antennas. These antennas can be used in any application, over a wide frequency range of 1 GHz to 10 GHz. An array of shorted microstrip patches has been designed to operate at the desired frequency. The dual-band operation is obtained by either creating a notch on one of the radiating patch of the microstrip patch antenna or loading the radiating patch by a slot. The patch used for this dual-band operation is shorted using a shorting wall. The results of both the designs are analyzed. The study carried on, helps to find the various antenna parameters and the optimized design of an antenna array and dual-band antenna.Item Open Access Broadband microstrip antennas with switchable polarizations(Dhirubhai Ambani Institute of Information and Communication Technology, 2010) Bombale, Uttam Laxmanrao; Gupta, SanjeevMicrostrip antenna consists of a patch of metallization on grounded substrate. These are low profile, lightweight antennas, most suitable for aerospace and mobile application. They are replacing many conventional antennas used in defense and commercial applications. They have got certain drawbacks such as narrow bandwidth, low gain, and low power handling capability and polarization impurity. Many researchers are trying to overcome these drawbacks. In this thesis also some efforts have been done to overcome certain drawbacks of microstrip antenna. One of the serious limitations of the microstrip antennas is its narrow bandwidth. The impedance bandwidth of MSA is around 1% only for thin substrates. The bandwidth of the MSA can be increased by increasing thickness of the substrate. If the thickness is increased it creates problems for impedance matching, produces radiations from the feed and distortions in the radiation patterns due to higher order modes. Therefore to avoid these problems thicker substrate is not used. The common techniques to improve bandwidth are Planner multiresonator configurations, Electromagnetically coupled MSA; Aperture coupled MSAs, Impedance matching networks for broad band MSAs & Log periodic MSA configurations. It is advantageous to use Electromagnetically coupled MSA because of its small size and no back radiations. Therefore Electromagnetically coupled MSA is used to design the antenna. The MSA gives linear polarization. Many times we need circular polarization with low cross polar level (generally below 10-12 dB). This circular polarization is obtained in this antenna using a shorting pin. This is the major achievement. Many papers discuss about bandwidth only, a few papers discuss just about polarizations using shorting pins. Many times we need large bandwidth, desired polarization and high gain. In order to obtain high gain we have to form an array of antennas. It is convenient to feed the array elements using microstrip feed. Therefore the Electromagnetically coupled MSA is fed using a microstrip line as described in chapter 4. Some times we need right circular or left circular or linear polarization depending on situation. These polarizations can be obtained using two shorting pins instead of one as described in chapter 4. In satellite TV transmission vertical and horizontal polarizations (Eθ and EФ) are used. In order to minimize adjacent channel interference they are placed alternately on vertical and horizontal polarizations. These additional Eθ, EФ polarizations as well as RHCP and LHCP are obtained using additional shorting pins as described in chapter 4. for satellite TV transmission we need high gain around 30 dB. This can be obtained using an array of above elements. The design is given in chapter 4. Various feeding techniques, transmission lines, bends, power dividers and quarter wave transformers are discussed. Spacefed microstrip antennas are also designed, simulated and studied in chapter 5. Recently fractal antennas are becoming very popular because of their small size, multiband response and high efficiency. The basic types of fractal antennas are designed and simulated in chapter 6. Bandwidth is the major problem in microstrip antennas. In chapter 7, it is discussed how do we get large bandwidth, and the concept is used to obtain very large or ultra-wide bandwidth using rectangular microstrip antenna. The same concept is used to obtain very large bandwidth using sierpinski fractal antennas.Item Open Access Multi band fractal antenna for satellite application(Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Kalariya, Vishalkumar Rameshbhai; Gupta, SanjeevFractal Antenna is the current topic for the research engineering because Fractal Technology allow us to design miniature antennas and integrate multiple band in single device. This antenna is a type of Micro strip antenna so it can be mount on the same PCB on which other RF components are mounted. There is not exact method to predict the resonance frequency of the Fractal antenna. Current research work tell that the prediction of resonance frequency of the Antenna is made from the simulation result. But in this work we try to predict the resonance frequency by mean of Network connection method. In this method each small segment of fractal shape antenna is treated as the single square patch and by analysis the separate patch and combing the total impedance by mean of Network connection method and the prediction of the resonant frequency is done by this thesis work. By using the Cavity model approach we find the impedance of the separate patch and by the Network connection model approach we can combine the total resistance and find the input impedance of the fractal antenna and we are trying to design the Multi band Fractal antenna for the L band(1.4GHz), C band(5.35GHz) and last is X band(9.65GHz) which is resonating at three band of frequency by this method.Item Open Access Dual-band microstrip antenna design(Dhirubhai Ambani Institute of Information and Communication Technology, 2005) Desai, Bhumi; Gupta, SanjeevMulti-frequency microstrip antennas are very much in demand due to their physical and mechanical properties like small size, lightweight, thin profile, low power consumption, and ease of implementation in the domestic applications. Some designs of dual-band microstrip patch suitable for GSM 900/1800 base station operation are already a research topic. Dual frequency microstrip antennas are also used in GPS and SAR. Commercially, these are deployed in RFID tags. But for the antenna to be useful in all these applications, its behavior like return loss, bandwidth, beam width, radiated power, gain, and directivity, at both the frequencies, should be nearly identical. The purpose of this work is to design the microstrip patch for dual frequencies of 945 MHz and 1960 MHz. Two new approaches called Coplanar patches and Overlapped patches are proposed. Then some of the existing techniques like Stacked patches, Dual slot loaded patches and Dual frequency PIFA are explored for our design specifications. Finally, the comparison of all the design aspects including the proposed ones is carried out in this work.Item Open Access Shorted microstrip patch antenna(Dhirubhai Ambani Institute of Information and Communication Technology, 2005) Bala, Shashi; Gupta, SanjeevIn this thesis, electrically small microstrip patches incorporating shorting posts are thoroughly investigated. These antennas are suitable for mobile communications handsets where limited antenna size is a premium. In particular, it is shown that the zero mode of the unloaded MSA (Microstrip Antenna) plays a central role for reducing the lowest operation frequency of the loaded MSA. The studies carried out allow the determination of all relevant antenna parameters for different post specifications and can easily be extended for different patch architectures.