Improved Low Cost Substrate Integrated Waveguide Symmetrical Window Bandpass Filter

Substrate integrated waveguide (SIW) has been recently emerged to be a promising technology in the development of microwave and millimetre-wave field. SIW is the integration of rectangular waveguide and planar circuit, exhibiting advantages from both technologies. In this paper, the design of low cost SIW technology for bandpass filter is discussed. The design of SIW symmetrical window bandpass filter is explained in detail. 5th order 0.5 dB ripple of Chebyshev filter response is used to design SIW symmetrical window bandpass filter. The measured results shows that the fabricated prototype is able to operate within X-band frequency with passband of 8.6 to 10.6 GHz. The design procedures in obtaining width of symmetrical windows and length of SIW window cavity are shown in detail in this paper. The filter design that fulfills the specifications is fabricated on a single layer Duroid RO4003C substrate using printed circuit board (PCB) process. The simulated result and measured result are compared and analyzed. Hence, it can be concluded that the measured bandwidth of the design is operating within X-band frequency range, which at 8.6 Hz until 10.6 GHz. The average value of measured S₁₁ has minimum of −20 dB and the average value of measured S₁₂ has maximum of −2 dB.