The measurement of propagation characteristics of the atmosphere at 890 GHz using an open resonator technique

A method using a modified conventional microwave open resonator technique in the form of a folded three-mirror submillimeter open resonator is developed to measure the propagation characteristics of the atmosphere at 890 GHz. This method allows both the atmospheric attenuation and the refractive index to be obtained by observing the changes in the Q factor of the resonances and the changes in the resonance condition of the open resonator, respectively. It is shown that a major advantage of the open resonator method is that both measurements may conveniently be made together in an instrument of relatively small dimensions, which enables measurements in artificial atmospheres or real atmospheres. In addition, the method has the capability of extending the measurements over a wide range of frequencies.