Development and characterisation of (Mg, Mn) U-type microwave absorbing materials and its application in radar cross sections reduction

The preparation and complex permittivity and permeability measurement of a new U-type of hexaferrite microwave absorbing material (Ba₄ Mg_2-xMn_xFe₃₆ O₆₀) is reported for different value of x in range 0 ≤ x ≤ 2. Complex permittivity and permeability values of hexaferrite pellets are measured using a vector network analyser (VNA) in X-band. The reflection loss of the materials is computed for different values of x and thickness using the measured permittivity and permeability values. The optimum reflection loss is found to be -43 dB for hexaferrite pellet (x = 0.5) at a thickness of t = 1.7 mm. Microwave absorbing paint pellets are prepared by mixing hexaferrite powder with polyimide solution and their complex permeability and permittivity are also measured using a VNA. Using these measured values, radar cross-section reduction simulation for artillery shells has been carried out using electromagnetic simulation software in the 8-10 GHz frequency range. A maximum radar cross-section reduction of 15 dB has been observed for a 30 mm artillery shell at 9 GHz.