Compact Triple-Mode Folded-HMSIW Diplexer With Wide Stopband and High Isolation Based on Embedded Isolation Network

Abstract

In this brief, a triple-mode folded half mode substrate integrated waveguide (HMSIW) diplexer with wide stopband and high isolation based on embedded isolation network is proposed. The embedded isolation network of SIW diplexer is introduced to achieve miniaturization, low insertion loss and flexible design of high isolation between two channels for the first time. Triple-mode folded HMSIWs with loading different slots are utilized to design filtering responses in two channels, which can further reduce size and insertion loss of the diplexer. Besides, the wide stopband can be obtained for feeding technology in Channel 1 and harmonic mutual suppression technique in Channel 2. In final, a prototype with 3-dB fractional bandwidths of 14.6% (Channel 1) and 6.2% (Channel 2) is designed and fabricated at 5.05 GHz (Channel 1 @ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> ) and 7.46 GHz (Channel 2 @ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{2}$ </tex-math></inline-formula> ). The in-band isolations and upper-stopband attenuation are better than 55 dB / 49 dB (Channel 1 / Channel 2) and 20 dB extended to 12.3 GHz ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.43f_{1}$ </tex-math></inline-formula> ). It occupies only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.56~{\lambda }_{\mathrm{ g}}^{2}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\lambda }_{\mathrm{ g}}$ </tex-math></inline-formula> is the guided wavelength at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> .