Vector Reflectometry in a Beam Waveguide
  We present a one-port calibration technique for characterization of beam waveguide components with a vector network analyzer. This technique involves using a set of known delays to separate the responses of the instrument and the device under test. We demonstrate this technique by measuring the reflected performance of a millimeter-wave variable-delay polarization modulator. 
Joseph R. Eimer, Charles L. Bennett, David T. Chuss, Edward J. Wollack
astro-ph.IM