Non-uniform Transmission Lines for Ultra Wideband: Design Optimisation and Interfacing to Antennas and Loads
Date of Award
Doctor of Philosophy
Dr. John Barrett
This thesis presents the electrical characterization of ultra-wideband non- uniform transmission lines (UWB NUTLs). Non-uniform transmission lines have been identified as a successful device for ultra-wideband pulse shaping, which can be designed to generate complex and arbitrary pulse shapes as an impulse response. The performance of a range of UWB NUTLs, with different substrate materials and load impedances, has been characterised. In addition, the possibility of interfacing NUTL with antennas and the filtering effect of antennas has been investigated. To characterise the NUTLs, knowledge of current literature related to NUTL designs is required. A detailed review of the literature published on topics related to microwave methods for electrical characterization of dielectric substrate materials, design of NUTLs for pulse shaping and measurements with UWB antennas has been presented. The literature review details the need for further study to characterise NUTLs and the advantages of NUTLs compared to traditional pulse shaping methods.
To design UWB NUTLs on different substrate materials, the broadband dielectric characteristics of the materials need to be known over a bandwidth of about 10GHz. Such information is not readily available from manufacturers. To do this, a novel broadband microstrip line-based permittivity measurement method has been developed. Measurement and simulation of the broadband relative permittivity of four different substrate materials using this method have been carried out. To identify the effect of different substrate materials, NUTLs have been manufactured with four different substrate materials with permittivity values in the range of 2.5 - 10 and their responses have been analysed. The results show that the loss and dispersive effect is significantly visible in an ordinary high loss substrate, FR4. The effect of various resistive, capacitive and inductive load terminations on NUTL’s response has also been studied. The experimental results show that the characteristics of load impedances do not influence the NUTL’s impulse response. In addition, the various load impedances can be identified from the impulse response of the respective loads. Finally, the effect of antennas on NUTL performance has been studied by integrating NUTLs with UWB antenna and measuring the response.
Narayanan, Prasanth Moolakuzhy, "Non-uniform Transmission Lines for Ultra Wideband: Design Optimisation and Interfacing to Antennas and Loads" (2013). Theses [online].
Available at: https://sword.cit.ie/allthe/475