Measurement of Reflection Coefficient by Means of Slotted Line and Homodyne Detection System

A new method for measuring the complex reflection coefficient in a measurement system with a slotted line and homodyne detector is presented. The measurement involves the investigation of the change of phase angle of wave voltage along the waveguide terminated with the element under test. The principle of measurement and X-band measurement system consisting of waveguide elements are described. The signal fed to the homodyne detector is subject to the rectangular phase modulation which facilitates the construction of the modulator and increases the accuracy of phase determination. The phase shifter used in the system includes a slotted line. The reduction of the influence of residual reflections on the phase shift determination is described. Even with standard waveguide elements the measuring accuracy of amplitude reflection coefficient is found to be approximately 10-3.