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Fractal-shaped microstrip coupled-line bandpass filters for suppression of second harmonic
Kim, Il Kwon,Kingsley, N.,Morton, M.,Bairavasubramanian, R.,Papapolymerou, J.,Tentzeris, M.M.,Yook, Jong-Gwan IEEE 2005 IEEE transactions on microwave theory and techniqu Vol.53 No.9
In this paper, microstrip coupled-line bandpass filters using a Koch fractal shape are proposed for the first time. These filters are fabricated on a liquid crystal polymer (LCP) substrate for Ku-band. Conventional microstrip coupled-line filters are very popular for RF front ends because they can be fabricated easily. However, their large second harmonic causes the shape of the passband to be asymmetric in the upper band and it worsens the skirt properties. By proper design, the second harmonic of fractal filters can be significantly suppressed through the use of fractal shapes. In this paper, using LCP, the maximum harmonic suppression was almost 42 dB. This type of filter can be used to suppress the second harmonic without any additional devices and regardless of the substrate.
X.D. Spiliotis,K.I. Ntampegliotis,V.G. Karayannis,G.A. Papapolymerou 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1
Pet coke (PC) and sewage sludge (SS) have been separately used as admixtures into clayey raw materials for ceramic manufacturing by extrusion and sintering. Thermal analysis of the clay mixtures incorporating 6% of either PC or SS shows a significant shift of the solidification temperature to lower temperatures. The bending strength-in terms of modulus of rupture (MOR)-of the ceramic specimens produced does not change appreciably up to 6% content in PC or SS, indicating that the manufactured clay-based ceramics are able to tolerate low percentages of these admixtures. The specimen open porosity increases and the thermal conductivity decreases by increasing the admixture percentage, while both thermal conductivity and MOR increase with increasing sintering temperature. The results indicate that the utilization of PC and SS in ceramic manufacturing processes may lead to changes in processing parameters, to energy savings and to materials with improved thermal insulating properties.
Manos M. Tentzeris,Joy Laskar,Jong-Gwan Yook,Il Kwon Kim,Nickolas Kingsley,Matthew A. Morton,Stephane Pinel,John Papapolymerou 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.4
In this paper, the fractal shape is applied to microstrip band pass filters and integrated on a high-resistivity Si substrate to solve conventional 2<SUP>nd</SUP> harmonic problem. Conventional microstrip coupled line filters are popular in RF front ends, because they can be easily fabricated and integrated with other RF components. However, they typically have large second harmonics that can cause unwanted interference in interested frequency bands. Without any additional filters, the proposed Koch shape filters have suppressed the 2<SUP>nd</SUP> harmonics by about ?40㏈, so they can be used in systems such as direct conversion receiver with stringent harmonic suppression requirements.