Gap Waveguide Array Element Filters

In order for the next generation of wireless communications to implement higher data rates, devices operating at higher frequencies such as W-band are required. Control of spectral emissions in integrated mm-wave systems has so far been neglected due to the limited amount of devices operating at the frequency range. Gap waveguides are a type of waveguide implemented in a periodic metamaterial that offer several critical advantages over standard waveguides, especially with regards to manufacturability. This research provides the design and analysis of three gap waveguide filters that are integrated into larger transmitter systems in order to prevent out of band emissions. These types of filters, which are directly integrated with antenna array elements are known as array element filters. The first filter is a third order filter centred at 100 GHz with a bandwidth of 4 GHz and 20 dB of passband return loss that was used to develop several filter components for the other filter designs. The filter was integrated with a slotted waveguide antenna array and the effects of the coupling between adjacent filter channels was investigated. The coupling between adjacent channels altered the farfield radiation pattern of the antenna, especially when beam steering is done on the array. The second filter is a seventh order folded filter that was designed and manufactured to meet the electrical specifications of the transmitter system whilst fitting into a transmitter system and minimising coupling between adjacent channels. The filter was designed with an inline topology with a centre frequency of 101 GHz and a bandwidth of 10 GHz with a transversal fold. The filter was manufactured using computer numerical control (CNC) milling from aluminium. The manufactured filter shifted up in frequency by 1 GHz. The measured response showed a large peak in the return loss at 98 GHz which was found to be due to an increase in the gap height of the gap waveguide structure. The lowest insertion loss measured in the passband was 1.34 dB. The third and final filter, a seventh order filter with a centre frequency of 100 GHz and a bandwidth of 5 GHz, implements transmission zeros in a novel structure that fits under a slotted waveguide antenna. The structure implements two transmission zeros in the upper passband of the structure at 103.7 and 107.5 GHz with a minimum passband return loss of 14 dB. Due to manufacturing costs, filters one and three were not manufactured, only verified through full-wave simulation using CST.

Grantor dc:publisher

Stellenbosch University

Year dc:date.issued

2025

Author dc:creator

• Fourie, Jack Duncan

Advisors dc:contributor.advisor

• Meyer, Petrie
• Steyn, Werner

Language dc:language.iso

en

Repository record dc:identifier.uri

https://scholar.sun.ac.za/handle/10019.1/132178

OAI identifier oai:identifier

oai:scholar.sun.ac.za:10019.1/132178