Frequency- and Time-Domain Performance of Four-Arm Mode-2 Spiral Antennas

The performance of simply-fed four-arm Archimedean and equiangular spiral antennas operating in mode-2 (conical beam) and their suitability for pulsed communication applications are investigated. The frequency-domain transfer function of spiral antennas-based ultra-wideband (UWB) link is synthesized using complex far field information measured in a spherical near-field chamber from 2 to 12 GHz. The time-domain performance is obtained by post-processing frequency-domain data using the inverse fast Fourier transform. The synthesized approach is validated computationally and using direct link measurements. The quality of radiated pulses is evaluated in terms of the fidelity factor over the full field of view. The study demonstrates that the mode-2 spirals exhibit good time- and frequency-domain performance over a multioctave bandwidth which allows multiple communication services including UWB and time-frequency RF surveillance applications to be integrated into a single aperture system.