Attenuator for rectangular waveguide (X-band)

Many attenuators are based on the cutoff principle [1] and can be divided into two groups. 1 - attenuators realized by means of coaxial cables placed between two portions of waveguide, thus requiring a double passage between the waveguide and the cable. Due to the connection between waveguide and cable, this kind of attenuator presents some drawbacks in the realization of microwave circuits. 2 - attenuators realized by using waveguides of different dimensions. In this way it is possible to have a direct connection in the microwave circuit. However, also this latter type of attenuator has some drawbacks, due to the abrupt transition between waveguides of different sections. Thus, a new kind of attenuator working directly in the waveguide, and in perfect matching conditions, can represent an instrument that can be extremely useful in experimental set-ups. We describe here a cutoff attenuator for rectangular waveguides in X-band that eliminates the drawbacks mentioned above.