Radiation and Dispersion Effects from Frequency-Modulated (FM) Sources

Abstract

We consider the Far-zone field radiated bv a frequency-modulated (FM) source in open-ended circular waveguide. The source is uniformly distributed over the waveguide cross-section. Possible multimode effects are included. The radiated fields are derived from an eauivalent source in the aperture. Far-zone fields are first obtained in the frequency domain with time-domain results following through an inverse Fourier transform. Results are given first in standard time and frequency domain plots. These are followed by short-time Fourier transforms and spectrograms that clearly show frequency modulation effects from the source and from the dispersion inherent in the wave propagation.