Transients in antennas
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Measurement and computational procedures are developed for inferring the frequency responses (both driving point and far field) of an antenna or antenna system from measurements made in the time domain (using nanosecond time-domain-reflectometer techniques). A hybrid computer has been used to present simultaneous displays of the pulse response and the frequency response (in both magnitude and phase). The experimental technique is used to empirically design a new wideband antennu for the 3-30 MHz band from measurements made on scale models. A design principle for an antenna which is to faithfully and efficiently transmit a very wide bandwidth signal is also presented, and an experimental evaluation of a preliminary design is reported. The frequency responses of individual parts of an antenna can be isolated and displayed simply with this experimental technique. To illustrate this, the input impedance and radiation from an effectively infinite monopole are presented. These results verify previous theories. Transmission and reflection coefficients describing the propagation of monochromatic current waves on thin bent wire antennas are inferred from parts of the reflected pulse response, Inspection of both the reflected pulses and the inferred frequency responses reveals the mechanism of current propagation on a bent wire antenna.