Phase characterisation in salisbury screen absorber at oblique incidence

In this paper we present the phase characterization in the Salisbury screen absorber at oblique incidence. As the angle of the incidence increases, electrical spacing between ground plane and the resistive sheet reduces, so the centre operating frequency of the microwave absorber increases. A High Impedance Ground Plane (HIGP) which is designed to scatter the reflected signals in a conjugate phase relationship to the change in the electrical spacing is employed in order to obtain a reduced angular sensitivity microwave absorber. Numerical and experimental results in the range 8 - 15 GHz are used to demonstrate that scan compensation can be obtained over the angular range 0° to 40° thus removing the shift in the resonant frequency which occurs in conventional Salisbury screen absorbers.