A filter structure comprising: - a first conductor layer (101, 201, 401), - a second conductor layer spaced apart from the first conductor layer and substantially parallel to the first conductor layer, and - a pattern in the first conductor layer with interconnected pattern elements (106 to 114, 206 to 209, 306 to 309, 406 to 414) and in each pattern element high-impedance conductor strips with a length/area ratio such that the inductance seen by a longitudinal electric current in each of the high-impedance conductor strips is dominant over the capacitance of the high-impedance conductor strip against the second conductor layer, and a low-impedance conductive region where the ratio of the area and the maximum diameter is such that the capacitance against the second conductor layer is dominant over the inductance of the low-impedance conductive region, wherein at least one of the pattern elements comprises: - at least two adjacent first high-impedance conductor strips (115, 116, 415, 416, 420) in a first direction, and - at least two adjacent second high-impedance conductor strips (117, 118, 417, 418, 421) in a second direction, characterized in that the first high-impedance conductor strips being straight and first ends of the first high-impedance conductor strips being arranged to connect to the low-impedance conductive region (119, 419) of the at least one pattern element and second ends of the first high-impedance conductor strips being arranged to connect to the low-impedance conductive region of a first neighboring pattern element, and second high-impedance conductor strips being straight and first ends of the second high-impedance conductor strips being arranged to connect to the low-impedance conductive region (119, 419) and second ends of the second high-impedance conductor strips being arranged to connect to the low-impedance conductive region of a second neighboring pattern element, and the first direction and the second direction being mutually intersecting. - a first conductor layer (101, 201, 401), - a second conductor layer spaced apart from the first conductor layer and substantially parallel to the first conductor layer, and - a pattern in the first conductor layer with interconnected pattern elements (106 to 114, 206 to 209, 306 to 309, 406 to 414) and in each pattern element high-impedance conductor strips with a length/area ratio such that the inductance seen by a longitudinal electric current in each of the high-impedance conductor strips is dominant over the capacitance of the high-impedance conductor strip against the second conductor layer, and a low-impedance conductive region where the ratio of the area and the maximum diameter is such that the capacitance against the second conductor layer is dominant over the inductance of the low-impedance conductive region, wherein at least one of the pattern elements comprises: - at least two adjacent first high-impedance conductor strips (115, 116, 415, 416, 420) in a first direction, and - at least two adjacent second high-impedance conductor strips (117, 118, 417, 418, 421) in a second direction, - at least two adjacent first high-impedance conductor strips (115, 116, 415, 416, 420) in a first direction, and - at least two adjacent second high-impedance conductor strips (117, 118, 417, 418, 421) in a second direction,