Ultra wideband spiral antenna - time delay removal

Abstract

This paper deals with the time delay removal of an Archimedean spiral antenna which operates from 400 MHz to 4845 MHz. As it is known, spiral antennas show a dispersive behavior, thus, in time domain, a "chirp" pulse will be displayed at the output. For time delay removal two procedures are investigated: the first one uses an error-term flow graph for the frequency signal as for Vector Network Analyzers while the second one supposes to place a reference metallic plate at a certain distance in order to identify the phase dispersion given by the antenna. In the second case the received signal is passed in time domain by applying an ifft, the multiple reflection are removed and the phase variation due to the time propagation is subtracted. After phase correction the time domain response as well as the side lobes level are decreased. The antenna system made up of two Archimedean spirals is employed by a stepped frequency continuous wave radar (SFCW) which works with a frequency step of 35 MHz.