Waveguide adapter with contactless flange for operation in the millimeter wavelength range

Methods of increasing accuracy of measurement results of S-parameters of waveguide devices operating in the upper part of extremely high frequency range are reviewed. It is shown that accuracy and reliability of measurements of S-parameters of waveguide devices depend on the quality of contact between waveguide flanges: leakage of electromagnetic radiation through gaps poses a significant problem and can lead to unreliable results in measuring insertion loss and voltage standing wave ratio. Therefore, particular attention is paid to quality of contact between the measurement system and the device under test when operating in the millimeter wavelength range. In this paper, a contactless waveguide adapter flange for millimeter wavelength range insensitive to any air gap when connected to the device under test is designed. The waveguide adapter with contactless flange constitutes a section of a standard WR10 rectangular waveguide terminated on one side by a standard UG-387 flange and on the other side by the proposed contactless flange with a pin-like structure. Use of an adapter with a contactless flange allows for minimizing issues related to measuring insertion loss and return loss caused by incomplete contact or lack of it when connecting two waveguide flanges. This type of flange connection can be used for rapid measurements because no flange screw fastening is required. A comparative analysis of a standard adapter and an adapter with a contactless flange is performed in a WR10 waveguide channel. Efficiency of contactless coupling is experimentally confirmed within the entire operating range of 75 to 110 GHz with a 100 μm gap at the edge of the waveguide coupling. Use of a waveguide adapter with a contactless flange allows for faster and at the same time more accurate measurement of S-parameters of the devices under test. This adapter is indispensable for quick certification of millimeter-wave waveguide devices by modern metrological tools (vector network analyzer and scalar network analyzer).