Metamaterial-based frequency selective surface with a band gap electronic adjustment
Currently, frequency selective surfaces, based on metamaterials are increasingly important in microwave technique. The mushroom-type metamaterial surfaces allow solving such tasks as isolation of elements in antenna arrays, multipath mitigating in GNSS systems, reduction of the ground plane edge influence on the directivity of the antenna elements etc. The usage of these structures in the microwave devices design can significantly improve their properties and performance. Structurally mushroom-type metamaterials are periodic microstrip structures and their properties depend strongly on the parameters of the substrate and the accuracy of manufacturing of the conductive pattern. As these structures have a narrow band gap, expensive materials and high precision technologies should be used for their manufacturing. A method of the mushroom-type metamaterial band gap electronic readjustment is proposed in this paper. The idea of the method is that a variable-capacitance diode, should be placed between two coupled mushroom hats one terminal of which is grounded for direct current through a metalized via of the metamaterial element, and the other one is connected to a controlled DC voltage source. At the same time the mushroom hats are separated by at least two capacitive gaps, one of which is in parallel with a variable-capacitance diode, which equivalent capacitance is determined by the DC voltage of the controlled source. The design of a band gap metamaterial-based frequency selective surface with an electronic readjustment of the working band, and the results of its numerical modeling, which show the working band frequency movement while the changing of the lumped elements capacitance are presented. The calculation of the structure dielectric parameters, which confirms that the proposed structure is a metamaterial, is provided.