Planar Scanning Measurement System of Material Properties Based on Free Space Method

In order to measure the dielectric electromagnetic properties of composite plates, a free space measurement system with frequency range of 8~18 GHz using planar scanning method is developed in this work. The key components of the measurement system are a pair of spot focusing lens antenna, a network analyzer, and a three-dimensional moving fixture guide rail and a computer. Due to the far-field focusing ability of the lens antenna, materials operating at microwave frequency can be measured in free space in a relatively compact and simple measuring device [1]. Through the movement of the guide rail of the three-dimensional moving fixture, the lens antennas are used to measure the composite plate in planar scanning mode, and the permittivity and permeability of the rectangular matrix in each frequency band are obtained. Then the error term can be eliminated and the average value is able to be calculated, so that the accuracy of the free space measurement can be improved.