Substrate Integrated Waveguide (SIW) Filtering Power Divider/Combiner with High Selectivity

A filtering power divider/power combiner using substrate integrated waveguide (SIW) cavities and microstrip transmission lines with high selectivity is presented. In this paper, two cavities which resonate in SIW TE102\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{TE}_{102}$$\end{document} and SIW TE201\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{TE}_{201}$$\end{document} modes are cascaded to make a bandpass-filtering response (SIW network). In addition, a microstrip network consisting of one isolation resistor and four sections of quarter-wavelength transmission lines is used to improve the isolation between output ports. In this microstrip network, the isolation resistor is connected to ground to arrest the appeared heat loss in the substrate. The physical dimensions are obtained by using the extracted external quality factor and coupling coefficient. The even and odd mode analysis is used to illustrate the operation of the circuit. There is a good agreement between the simulated and measured results. The measured results show a 3 dB bandwidth of 230 MHz ranging from 8.83 to 9.06 GHz. Within the passband, the return loss is better than 13 dB, the isolation between output ports is above 16 dB, and the minimum insertion losses are 2.7 and 3.3 dB at port 2 and port 3, respectively.