In Situ Measurement of Absorbing Properties of Materials Based on Near-Field Reflection Method

To meet the requirements of the in situ measurement of the absorbing properties of materials and break through the limitations of the transmission line probe method in ultrawideband and high-precision measurement, this article presents in situ measurement technology for the absorbing properties of materials based on near-field reflection testing. A miniaturized ultrawideband antenna, a decoupling structure, and a shielding cover are designed, and an in situ measurement probe is constructed. By integrating the probe with a microwave transceiver module as well as a control processing module, a handheld broadband microwave reflectivity test instrument is developed and its performance is verified. The measurement accuracy of the proposed instrument is higher than that of transmission line probes, and the deviation of its test results from those of standard arch systems is less than 1.5 dB in the reflectivity range of 0–20 dB; its test frequency band is wider and its frequency band covers 2–18 GHz. The instrument is suitable for accurately measuring the absorbing properties of materials with thicknesses of less than 1.5 mm.