Waveguide filters

A method for designing a filter for filtering an electromagnetic wave, the method comprising:

• choosing an element with regarding to geometry;
• choosing size of a cavity with a first plate and a second plate, the first and second plates are in parallel and opposite to each other;
• choosing a number of elements distributed on the side of the first plate facing the cavity;
• defining locations of each element on the first plate by a coordinate system;
• choosing a number of elements distributed on the side of the second plate facing the cavity;
• defining locations of the elements on the second plate according to the locations of the elements on the first plate such that each element is distributed on the second plate with an offset with respect to a corresponding element on the first plate, wherein the elements are any of holes or recesses, and wherein the filter comprises electromagnetic band gap, EBG, surfaces on sides of the first and second plates to constrain the electromagnetic wave to propagate along a direction of the cavity from one end to the other, and as the electromagnetic wave is traversing about the elements in the cavity, specific wavelengths are filtered;
• analyzing a unit cell comprising a subset of the chosen elements;
• assessing performance of the unit cell;
• modifying elements until improve matching;
• assessing performance of the filter;
• and
• adjusting the size of a cavity, the number of unit cells until the performance of designed filter fulfils specifications of the filter.