Novel mode content analysis technique for multimode waveguides

This paper presents a novel technique for analyzing the mode content in multimode waveguides. The technique is based on measuring the frequency response between the two antennas coupled into a multimode waveguide and using that information to extract the frequency-averaged mode content at the location of the transmitting antenna. The technique is applicable to cases in which the complex mode amplitudes are approximately constant over the frequency range of interest. This method is valuable for determining the mode mix generated by arbitrary transmitting antennas in a multimode waveguide propagation environment, such as HVAC duct system used for indoor wireless communications.