Agilent / HP R382A

This attenuators consist of three sections of waveguide with a resistive film stretched across the center of each.

The films at each end are in line with each other and fixed at right angles to the E-field of an incoming wave.

The center section is free to rotate axially.

When all three films are in line, there is no current flow in the films and no attenuations.

When the center section is rotated with respect to the plane of the other two films, attenuation increases according to a consine squared law.