Design of a surface mounted waveguide filter in substrate integrated waveguide technology

In this paper, a novel combination of substrate integrated waveguide (SIW) and surface mounted waveguide (SMW) filter is presented for the purpose of reducing losses in SIW technology. The waveguide filter is comprised of five directly coupled resonators. Since the apertures in the top metallization of the SIW act as input/output inverters, no extra transitions are required to interface the two technologies. The SMW filter is designed for K-band with a 500 MHz bandwidth and a return loss of 20 dB. It is fabricated and measured, and experimental results are in good agreement with simulations. The SMW filter shows insertion losses of 1 - 2 dB which is superior to most SIW filters in this frequency range, while still inheriting most advantages of SIW technology. A tolerance analysis and a study on single resonator loss are presented as well. The final SMW filter design is suitable for integration in PCB sub-circuits boards using standard production lines with pick-and-place automation and reflow solder processes.