Microwave measurements of reflection coefficients according to angle of incidence with the aid of a bistatic configuration

A technique deploying two horn antennas in bistatic configuration is used to measure coefficients of reflection from surfaces having anisotropic properties. In a context where a high degree of exactitude is not strictly necessary, the method or strategy developed by the authors gives rapidly an idea of the true behaviour of reflection coefficients with respect to the angle of incidence. This is convenient for restricted budgets since it uses conventional apparatus to measure relative powers. The modulus of the reflection coefficient is measured directly with the aid of matched lenses used to improve the directivity of the radiation and hence to block direct coupling between the antennas. On the other hand it is shown that with less directive antennas the direct path can be used knowingly to measure the phase. Edge effects causing diffraction and multiple reflections should be negligible. In order to verify its effectiveness the method has been studied in detail on samples of slightly lossy dielectric materials backed with a metallic plate.