Tailoring of higher‐order mode suppression in a high‐power alternative to classical waffle‐iron filters

In this article, a novel stepwise technique for the design of high‐power low‐pass harmonic filters is proposed. The fundamental and higher‐order mode suppression process is divided into three different steps. In the first step, the fundamental TE 10 ‐mode rejected band is accomplished by adjusting the height of E‐plane bandstop elements along the propagation direction. In the second step, this arrangement of bandstop elements is made two‐dimensional to suppress the higher‐order TE n0 modes. Finally, the higher‐order non‐TE n0 modes are rejected by controlling the minimum mechanical gap of the filter. The design process ends after the first, second, or third step depending on the intended mode behavior for the filter. The main characteristic of the new design technique is that the filter minimum mechanical gap can always be made much larger than in the classical solution (E‐plane corrugated or waffle‐iron filters) for the same frequency specifications. To validate the control of the higher‐order mode suppression that this method permits, three different filters are designed and compared. Moreover, a prototype has been fabricated and its S‐parameters measured to prove the feasibility of the proposed filters for a tailored frequency response. Finally, its high‐power handling capability has been estimated.