Design of Planar Single-section and Cascaded Directional Filters
In the proposed paper,a single-section and cascaded microstrip directional filters is designed for modern communication systems,such as mobile telephony,radiolocation and satellite links.The proposed filter takes on the structure of a Quadrature Hybrid coupler,where a parallel branch is capacitively coupled by two coupling resonators.It also has four ports which are completely match and exhibits a directional and filter-like frequency characteristics.This four-port device has a bandpass response between ports 1 and 4(S41),and its complementary reject-band response between ports 1 and 2(S21).No power is transmitted to port 3(isolation),and none is reflected to port 1.By compensating the line length between the coupling resonators of the single-section directional filter,better performance can be achieved,notably in matching.Furthermore,cascading multiple single-section directional filters will lead to the generation of transmission zeros in the stopband and therefore will sharper the cut-off response characteristics.To validate the proposed directional filter configuration,related analysis,and design theory,a single-section and cascaded microstrip directional filters are designed and fabricated using FR-4 substrate with dielectric constant of 4.05,loss tangent of 0.014 and thickness of 1.6 mm.The overall dimension of the single-section and cascaded directional filter are 74.4mm by 45 mm,and 122.2mm by 50mm respectively.For the single-section directional filter,the best matched measured return loss S11 is less than-20 dB around center frequency of 2.35 GHz.Good isolation S31 is obtained at values less than-25 dB.The filter response shows a bandstop characteristic with band elimination,S21 of-14.03 dB and a bandpass characteristic with coupling S41 of-3.64 dB.For the cascaded directional filter,the best matched measured return loss S11 is less than-25 dB.The measured S21 and S41,are-20.43 dB and-2.74 dB respectively.Power at port 3 is well isolated with S31 values of less than-25 dB.The measured filter response showed good agreement with the simulation results.Both simulation and measurement data are presented and discussed.
Y.H.Choo K.M.Lum
School of Science and Technology,SIM University,Singapore
国际会议
Progress in Electromagnetics Research Symposium 2013(2013年电磁学研究新进展学术研讨会)
台北
英文
70-75
2013-03-01（万方平台首次上网日期，不代表论文的发表时间）