A filtering device comprises an analogue quadrature splitter together with a first filtering element and a second filtering element. The filtering device is adapted to transform filtering characteristics of the first filtering element and filtering characteristics of the second filtering element into an effective filtering characteristic present in an output signal at an output terminal of the analogue quadrature splitter. The first filtering element and the second filtering element comprise filtering elements of high accuracy, with a steep roll-off but poor power handling capabilities. Using a high power quadrature splitter it is possible to transform the filtering characteristics of the first filtering element and/or the second filtering characteristic of the second filtering element into the effective filtering characteristics. The present disclosure further provides a method for filtering RF signals and a computer program implementing the manufacture of the filtering device and an execution of the method of filtering.