This paper presents high power, thermal analyses, and implementation of a stepped impedance high-power low-pass filter (LPF). A comprehensive model and analysis have been developed for the design and simulation of the LPF. In this analysis, power handling capacity and breakdown-voltage are discussed, and the effects of critical points are considered. The attenuation due to conductor and dielectric losses is also studied. The novelty of our approach lies in employing theoretical analysis to estimate the power-dissipation of the filter based on the proposed equivalent circuit. An accurate method is also introduced to calculate attenuation in the filter's elements. Thermal analysis to obtain accurate temperature profiles is done for the first time based on the electro-thermal simulation. Consequently, an effective cooling method is used to spread heat across the entire filter. Finally, the filter was implemented and tested to operate at L-band with handling 8 kW peak and 800 W average power. The insertion-loss is less than 0.27 dB, the stop-band attenuation is more than 60 dB, and the return-loss is better than 15.7 dB. The filter is capable of tolerating produced heat without any destructive effects at a maximum temperature of about 200 C above ambient. The theoretical analysis and experimental results show that the LPF is suitable for high-power microwave applications.

Abstract:A quasi fractal structure is introduced to build up a nondegenerate dual mode dual band bandpass filter. In the proposed filter a Koch fractal structure is applied to a microstrip patch resonator for miniaturization and dual band operation. The first band is specified by the first iteration of the fractal patch while the second band is determined with the second iteration. The most important feature is that the second band is independent of the first band and is simply tuned which is a challenge in dual band filters. A precise analysis of operation of the filter is presented. The measured results of the filter have good agreement with the full-wave simulated results. Keywords: dual mode, dual band, fractal filter Classification: Microwave and millimeter wave devices, circuits, and systems Lett., vol. 18, no. 6, pp. 392-394, June 2008. [4] W. He, Z. Ma, C.-P. Chen, T. Anada, and Y. Kobayashi, "A compact dual band bandpass filter using stub loaded two mode resonators and direct source load coupling to obtain improved stopband characteristics," Microw. Opt. Technol. Lett., vol. 51, no. 3, pp. 618-621, March 2009. [5] X. Y. Zhang, J. Shi, J.-X. Chen, and Q. Xue, "Dual-mode dual band bandpass filter based on double-sided parallel-strip line," Microw. Opt. Technol. Lett., vol. 51, no. 5, pp. 1361-1363, May 2009 Y.-K. Su, J.-R. Chen, M. H. Weng, and C.-Y. Hung, "A right slotted patch dual-mode dual band bandpass filter used for WLAN," Microw. References