Dual Source Excitation Rectangular Waveguide Design and Evaluation for the Measurement of Electromagnetic Material Properties

Broadband material parameter measurements are essential in understanding how materials interact with electromagnetic waves. Traditional rectangular waveguide material measurement systems are bandwidth limited. This results in multiple rectangular waveguides of different sizes used to conduct broadband material parameter extraction. Efforts to produce a broadband rectangular waveguide have focused on the inclusion of different guiding structures in the waveguide body. These designs have the drawback of requiring precise machining and time-consuming sample preparation. This research proposes a new broadband rectangular waveguide design which uses a dual source excitation design. This is enabled by the fact that rectangular waveguides are linear time invariant systems. The fields excited by each source superimpose in a linear fashion. As a result, specific electromagnetic modes are suppressed. The single electromagnetic mode frequency range now depends on the relative phase of the excitation sources rather than the cutoff frequency of higher order modes. A dual source excitation S-band waveguide is proposed in this research. Results from CST Microwave Studio ® (MWS ®) simulations are compared with those from a physical design measured with a 2-port network analyzer. These results are used to determine if this proposed rectangular waveguide design is suitable for broadband material measurements