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

Abstract

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 TE10‐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 TEn0 modes. Finally, the higher‐order non‐TEn0 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. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2967–2974, 2014

Chirping Techniques to Maximize the Power-Handling Capability of Harmonic Waveguide Low-Pass Filters

“…Thus, if the maximum frequency to be rejected is high, the E-plane mechanical gap will be small and, therefore, high-power operation will not be allowed. In recent times, a high-power low-pass filter with suppression of the higher-order TE n0 modes was presented in [18]- [19] based on a two-dimensional arrangement of quarterwave bandstop elements of smooth profile. Like [8], this technique requires long windowed sections to achieve the matching of the filter which have a negative impact on the insertion loss of the filter and its final size.…”