In this thesis, a computationally efficient model is proposed to determine different performance parameters of a conical horn antenna of arbitrary profile numerically over a wide range of frequencies. The model is developed using mode matching technique that solves the waveguide junction problem and an integral equation technique that solves the waveguide aperture free-space transition. It has functions to evaluate the S parameters, near-fields and far-fields of the antenna. Rigorous testing of the proposed novel technique has been done using MATLAB and the results have been verified by comparing them with the results obtained from commercial tools like FEKO and CST. This technique is capable of finding the performance parameters of the antennas faster than the available solvers in commercial tools like FEKO and CST. Furthermore, various goal functions are proposed for the optimization of some of the performance parameters such as the S parameters, the cross-polarization levels, and the aperture efficiency. These goal functions can be used to find optimum horn antenna feed profiles for radio astronomy applications.

Mankind becomes ever more reliant on wireless technology like mobile communications, navigation and radar. This development has resulted in more sensitive receivers, but this increased sensitivity also has increased the susceptibility of these receivers to interference from external sources. One of these sources that is known to disrupt terrestrial communications is the Sun. The DISTURB project aims to provide the means to observe and study interference phenomena generated by the Sun between frequencies of 10 MHz and 3 GHz. Furthermore, DISTURB stations should provide the ability to observe the Sun from sunrise to sunset, at any location in the world and thus require full hemispherical coverage. This master thesis project is concerned with the design of a conformal phased array antenna for a novel application in radio astronomy. The goal of this project is to provide an initial conformal array design that is able to provide full hemispherical coverage in the 1500 MHz to 3 GHz band of the DISTURB project. A quasi-spherical array of radius 1.55 metres and with 343 crossed modified bow-tie antenna elements, distributed using a novel geodesic topology, is proposed and found to satisfy DISTURB requirements in the frequency range of 1.3 to 3 GHz. Hence, the designed array is found to achieve a fractional bandwidth of 79% and therefore even exceeds the initial design goal. Finally, the designed array is compared to a parabolic reflector antenna, resulting in an insight in the complexity of a conformal phased array antenna design and the advantages and disadvantages such a conformal phased array antenna may bring to the DISTURB project.

Space launches have been steadily increasing over the years as satellites are being used in various applications such as communication, military, and science. The costs of launching satellites are still high and depend on the dimensions and weight of the satellite. With the advancement in the field of autonomous robotics and telecommunications, the need for multiple satellites in swarms and constellations is also growing. Cubesats have emerged as an alternative for these issues as they provide a low cost and compact solution. After the successful launch of NCLE (Netherlands China Low-Frequency explorer), a radio astronomy payload in the Chang'e 4 mission, efforts are being made to reduce the size of the payload to meet the cubesat standards. This work aims at investigating the design and implementation of a sensitive radio receiver for low-frequency radio astronomy from the lunar orbit with a cubesat platform. The aim is to study the practical aspects involved in realizing the design and improving the sensitivity of the instrument. The science objectives are similar to that of the NCLE payload which includes the frequency band of 80 kHz-80 MHz with high dynamic range and linearity. The thesis is a step further in the project OLFAR which aims to have a swarm of satellites in the lunar orbit to perform long-baseline interferometry at low frequencies. This work focuses on the analog signal chain of the payload which contains the antenna, low noise amplifier, filters, and the ADC. For the design of the antenna, the antenna length, efficiency, and IXR of three antenna configurations have been presented. As radio frequency interference poses a problem during the design of the amplifier chain, the effects and coupling mechanisms of RFI have also been studied. Limits on all internal and external instruments for radiated emissions have been set for the design to be sky noise limited. The amplifier design takes the science cases into account and is designed to achieve the required sensitivity, using a structured electronic design approach. The implementation of the amplifier chain was done with discrete components at ASTRON (Netherlands Institute for Radio Astronomy) and measurement results have also been discussed at the end.