Compared to the history of science, spectroscopy at terahertz frequencies is a relatively recent development. Terahertz instruments were initially large and inefficient due to the characteristics of available technology. With progress in materials science and miniature circuit manufacturing techniques, we may fabricate micro-meter scale devices to generate and detect terahertz radiation. However, the complete spectroscope apparatus remains large due to the use of components such as lenses and mirrors designed in the far-field optical regime. A truly miniature terahertz spectroscope would be designed without lenses and mirrors to enable a wide range of inexpensive and pervasive applications in diverse fields such as medicine, materials identification, and security. We present detailed evaluation of some candidate structures for a quasi-optical device and design criteria for a quasi-TEM transmission-line based device. Quasi-TEM transmission lines are inherently broadband and therefore suited for use in a spectroscope. / Graduate