| A high-power microwave (HPM) reflectarray antenna (RAA) element consisting of a twoarm spiral short circuit waveguide is presented. The RAA element has omnidirectional circularly
polarized radiation, which is designed and simulated using CST Microwave Studio Suite.
Reflectarray antennas, a relatively recent advancement in antenna technology, combine the high
gain characteristics of parabolic reflectors with the design flexibility of phased array antennas,
without requiring the complex feeding network of traditional phased arrays.
The reflectarray is designed for fc = 2.85 GHz, and the maximum reflectance is between
2.7 and 3.1 GHz. A single element can handle 70 MW power under vacuum condition. The antenna
is made up of a Perfect Electric Conductor (PEC) consists a two spiral arm slots, ensuring optimal
electrical conductivity and minimal ohmic losses. The proposed RAA element is a slot which inset
within an all-metal structure, which are crucial in generating the circularly polarized wave. These
slots are strategically configured to achieve phase advancement curve across the aperture, resulting
in a broad radiation pattern and an optimal gain-bandwidth by varying the element positions.
To accurately simulate the electromagnetic behavior of the RAA, the CST Microwave
Studio Suite was utilized, employing the Floquet mode in the frequency-time domain to solve the
antenna structure. This method models the periodic structure as an infinite array and yields
accurate results for fundamental performance characteristics including S-parameters, phase
advancement, E-field radiation patterns.
A comprehensive parametric study was conducted to optimize the RAA design. Two-phase
advancement schemes for controlling the RAA beam steering are proposed. A rotational method
can provide 140° advancement, while a short-circuit depth control method provides 360°.
The array directivity is simulated with Floquet mode analysis and calculated analytically.
The measured radiation performance supports the feasibility of the design, and the results are
consistent with the simulations. Unlike traditional phased array antennas, reflectarray antennas do
not require a complex feeding network, which significantly reduces power losses and enhances
overall system efficiency.
The proposed antenna design work is entirely based on simulation, which is the standard
and most common practice for solving High Power Microwave and Radio Frequency experiments.
Conducting a hardware-based experiment requires various hardware components, high-power
generators, and an anechoic chamber for performing high-power radiation experiments which are
expensive and tough to set up. In accordance with microwave engineering best practice, we, we
were able to rely on simulation-based methods, which provided an effective alternative to
hardware-based experiments.
In summary, this thesis demonstrates the design and simulated result of the RAA to show
its effectiveness and the feasibility of the practical advantages offering a compact, high-gain,
circularly polarized antenna solution for next-generation wireless communication and radar
applications.
Keywords: Reflectarray, spiral, slot antenna, high-power-microwave (HPM), omni-directional,
satellite, 5G Technologies. |