https://dspace.iiti.ac.in:8080/jspui/handle/123456789/9535 2026-05-12T17:12:09Z https://dspace.iiti.ac.in:8080/jspui/handle/123456789/17540 Title: A neural network framework to uncover cosmology from radio observations of the early universe Authors: Tripathi, Anshuman Abstract: The cosmic dawn (CD) and the epoch of reionization (EoR) mark critical periods in the early Universe, characterized by the formation of the first luminous sources and the subsequent heating and ionization of the intergalactic medium (IGM). Despite their significance, the physical conditions of the IGM during these epochs remain poorly constrained due to observational challenges. The redshifted HI 21-cm signal offers a unique window into these periods, and several experiments, such as EDGES, SARAS, MWA, and the forthcoming SKA, are actively targeting the detection of this signal. However, the signal is obscured by dominant foregrounds, instrumental systematics, and ionospheric distortions, further complicating by direction-dependent and frequency-dependent variations in antenna beam patterns, particularly at low radio frequencies. This thesis focuses on addressing these challenges by developing a robust, end-to-end data analysis pipeline that leverages machine learning (ML) and Bayesian statistical techniques. Traditional inference methods become computationally expensive as the dimensionality of the problem grows, necessitating scalable and adaptive approaches. We systematically investigate each major observational obstacle, such as foreground contamination and ionospheric effects, and train artificial neural networks (ANNs) to recover global 21-cm signal parameters from all-sky averaged spectra. The trained ANN achieves a signal parameter recovery accuracy of 96–97%, exhibiting resilience to static and slowly time-varying ionospheric conditions. Additionally, the performance of the ANN framework remains consistent across different sets of signal simulation datasets using different input parameter distributions. 2025-12-17T00:00:00Z https://dspace.iiti.ac.in:8080/jspui/handle/123456789/17476 Title: UAV-based radio frequency spectrum sensing using FPGA and radio frequency modulation classification Authors: Rajuskar, Tejas Abstract: This thesis is divided in two stages. The first stage showcases a methodical implementation for a real-time RF emission acquisition, storage, and analysis system, useful for a variety of uses, including spectrum sensing, RF fingerprinting, commercial communication, electronic warfare, and more. The receiving antenna, low noise amplifiers, signal mixers, band-pass filters, and other components make up the analog front end of an RF signal acquisition chain. In order to process the continuous input RF signal from the front-end using digital computing devices such as a CPU (such as a Raspberry Pi SBC) and FPGA (such as a Xilinx ZCU-104), an ADC in the system backend transforms it into digital form. The Red Pitaya STEM Lab 125-10 serves as the main signal collection device in this project, which simulates an electronic warfare system and uses a small signal acquisition and recording system with a simple analog front-end. A Raspberry Pi 3B+ (Single Board Computer) receives the obtained samples for software-based signal processing and analysis. The Red Pitaya’s RF input "IN1" has a 50 MHz LPF and a preset sampling rate of 125 MSPS. Strategic and commercial enterprises will employ the system, which consists of the Red Pitaya, Raspberry Pi, and antenna front-end, for remote data collecting applications using drones, unmanned vehicles, and other devices. 2025-05-16T00:00:00Z https://dspace.iiti.ac.in:8080/jspui/handle/123456789/17475 Title: Space-deployable reflectarray antenna in L-band Authors: Ghosh, Sreya Abstract: This thesis introduces a novel space-deployable reflectarray(RA) antenna in L band (1-2 GHz) tailored to be stowed in CubeSats. The lower frequency of L band makes the size of reflectarray considerably large to be stowed in microsatellites. The novel design aims to incorporate miniaturization of the phasing elements of the reflectarray to diminish the overall size of the structure. The RA is made up of 256 unit cells, each of periodicity 35mm and a third order Minkowski fractal. The feed antenna designed for the RA system is a 2x2 patch array. The patch array and the RA together make the RA system compact and easy to be deployed in a CubeSat. This work aims to contribute to space-deployable compact L band antennas for better understanding of the universe’s structure and evolution. A precursor to space deployment of the reflectarray antenna can be a deployment of the antenna for RFI survey in the pristine radio-silent Arctic region. Radio frequency interference (RFI) is a crucial aspect of radio astronomy. Thus the thesis presents the preliminary results of the RFI survey conducted at the Himadri Station in Svalbard, Arctic. The frequency range of 100 kHz to 1750 MHz is significant for various low-frequency radio astronomy studies, such as redshifted 21 cm observations. This work examines the potential of Himadri Station as a suitable site for RFI free radio astronomy observations. The experiment provides a hands-on experience of the use of antennas for radio astronomical purposes. 2025-05-16T00:00:00Z https://dspace.iiti.ac.in:8080/jspui/handle/123456789/17474 Title: Study, simulation, design and manufacturing of attitude determination and control system for mini-satellite system in low earth orbit Authors: Hazara, Souradeep Abstract: The objective of this thesis is to investigate the complete Study, simulation, design and fabricate of Attitude Determination and Control Systems (ADCS) in Earth-orbiting satellites specifically for the Low Earth Orbit(LEO). First part of the thesis focuses on the experimental determination of geomagnetic fields and methodologies, providing a solution to determine the orbit’s magnetic field in reference to the subsatellite point of the earth giving a new dimension to the research. ADCS is critical for maintaining a satellite's orientation relative to reference points such as Earth, the Sun, or other celestial bodies, allowing critical operations such as high-resolution imaging, precise data collection, and stable communication links. The research highlights the importance of attitude control systems (ADCS) in modern space missions as well as the difficulties associated with achieving accuracy and reliability in attitude control. Magnetometers, Helmholtz cages, and inertial measurement units (IMUs) are among the components and technologies examined in this study. 2025-06-07T00:00:00Z