Spectral Signature Decay Analysis and New Tapered Coaxial Transmission Line Spectrometer Design

A molecule dynamics model and details of a large electrical volume coaxial spectrometer are presented in this paper. The molecule dynamics model gives successful molecular signal decay predictions in coaxial spectrometers and shows that our current design is beyond the wall collision limit. The dimensions of the large electrical volume coax and a solution for practical fabrication of the transmission line that avoids spurious mode coupling are also introduced in this paper. The measured spectrum has an 8-dB improvement in signal-to-noise ratio over previous techniques, and fast detection was achieved with 100 averages. The better performance of this coaxial transmission line spectrometer improves its potential in the application of microwave chemical sensing, and the molecule dynamics model is useful for future coaxial spectrometer designs for higher operation frequency where molecular signals are stronger.