Method of Measuring Millimeter Waveguide Line Attenuation

The shuttle-pulse method has been used to measure the attenuation characteristics of the circular waveguide for millimeter-wave transmission. However, the measured results by the shuttle-pulse method cannot avoid some errors when there are periodic imperfections along the waveguide axis. To remove this shortcoming the pulse single-reflection method was developed in the Electrical Communication Laboratory, Nippon Telegraph and Telephone Public Corporation. This paper describes measured results using these two methods. It is confirmed that the measured results are in good agreement with each other when the waveguide has no periodic imperfections. But the attenuation measured by the shuttle-pulse method is smaller than the pulse single-reflection method, when there are periodic imperfections. These results are also theoretically confirmed. The pulse singlereflection method is shown and recommended as a reliable measuring method to determine circular waveguide line loss.