Use this URL to cite or link to this record in EThOS:
Title: Submillimetre scattering antennas
Author: Cummins, Howard John
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1982
Availability of Full Text:
Access from EThOS:
Access from Institution:
Early attempts at constructing point contact detectors for submillimetre radiation led to the conclusion that the whisker itself exhibited long wire antenna properties. This discovery initiated the design of more advanced travelling wave antenna structures in a number of laboratories. The objective of the present study has been to investigate an alternative approach to electromagnetic transduction, namely the standing wave antenna. In the context of this work the antenna is to be regarded not merely as a coherent flux collector, but as a device for efficiently converting the Poynting flux in a Gaussian beam waist into a conduction current. A basic study of coupled dipole arrays has been undertaken by a scattering technique that obviates the need for extracting power from the antenna terminals. A microcomputer controlled open resonator has been developed for making absolute measurements of the total scattering cross-section of arrays and the optical constants of various ultra thin substrate materials. Back-scattering measurements under travelling wave conditions were also undertaken to verify that these arrays exhibited useful radiation patterns in both the E and H-planes. The electrical properties of the antenna arrays were found to be predictable using established theory. A photolithographic technique was employed to reproduce the antenna structures on thin mylar substrates previously metallized with silver. Once antennas can be fabricated, there is a requirement for compatible transmission line structures which should ideally match the feed point impedances of the antennas so as to achieve maximum power transfer. In order to investigate the matching conditions, backscattering measurements were made on arrays of identical dipoles each connected to a length of coplanar transmission line. Travelling wave vee-antennas have also been employed in an investigation of the dependence of the line velocity factor on substrate thickness. The electrical properties of the coplanar transmission lines were found to be in agreement with conventional theory and the ability of standing wave antennas to efficiently couple energy to them at a frequency of 891 GHz was verified.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Electrical Engineering