Dielectric leaky wave antennas for future terahertz systems

Yao, Kai (2024). Dielectric leaky wave antennas for future terahertz systems. University of Birmingham. Ph.D.

Preview

Yao2024PhD.pdf
Text - Accepted Version
Available under License Creative Commons Attribution.
Download (8MB) | Preview

Abstract

This thesis endeavours to enhance the performance of terahertz antennas for communication and sensing applications. In pursuit of this objective, the thesis presents the design of two integrated dielectric leaky wave antennas (LWAs) operating in the sub-terahertz band. It includes the design of a H-band Dirac leaky wave antenna (DLWA) constructed from micromachined silicon, which is suitable for beam scanning applications. Additionally, the research encompasses a H-band direct laser written polymer Fabry-Perot cavity antenna (FPCA), designed for stable beam pointing applications.
In this thesis, the proposed DLWA represents the first instance of a sub-terahertz band all-dielectric DLWA featuring a closed bandgap. The all-dielectric unit cell exploits accidental degeneracy (i.e. frequency-balancing) to achieve suppression of the open stopband at broadside radiation. Through dispersion analysis of the unit cell, the radiation aperture is tapered with a Taylor amplitude distribution to achieve a sidelobe level (SLL) less than -30 dB at the center frequency while keeps the open stopband suppressed. The DLWA proposed in this thesis exhibits a fan-beam radiation pattern, low sidelobe levels (SLLs), and high aperture efficiency across the entire WR-3 frequency band. To mitigate Ohmic losses and enhance total efficiency, the antenna was fabricated using through-hole deep reactive ion etching (DRIE) on a high resistivity silicon wafer. The fabricated prototype of the DLWA has been measured, providing further validation for the proposed design.
Additionally, for the first time, an all-dielectric direct laser written FPCA operating at WR-3 band is proposed. Leaky wave analysis and transvers resonance method is used for the unit cell design. For a wider working bandwidth, the resonance unit cell of the FPCA’s partial reflective dielectric surface is tapered. Additionally, the total quality factor of the FPCA's resonance cavity is carefully adjusted to optimize gain while minimizing dielectric losses attributed to the photoresin. A standard UG-387/U flange shim is fabricated to integrate the FPCA with open-ended waveguide and evaluate the performance of the FPCA. After the measurement of the fabricated prototype of the FPCA, it was confirmed that the innovative design eliminates the need for additional iris and matching metal layers. This achievement leads to good impedance matching and a high 3 dB gain bandwidth product (GBWP), surpassing the performance of similar antennas reported in previous publications.
Finally, this thesis discusses the remaining issues and future work plans for the two antenna designs proposed.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):