Microwave chemical sensing using an 3–18 GHz wideband overmoded coaxial cable

A room-temperature chirped pulse Fourier transform microwave spectrometer was recently demonstrated using a WRD750 double ridge waveguide. The operation frequency range, 7.5 GHz to 18 GHz, is limited by the waveguide, and the effective sensing area is confined within the small region between the two ridges. This paper shows a new overmoded coaxial cable spectrometer design utilizing a Hamming function tapered transmission line method that provides smooth tapering to increase the spectrometer's bandwidth by 43%. The successful spectra measurement in this paper proves the application of using the overmoded coaxial cable as a chemical sensor.