High Performance Air-Filled Substrate Integrated Waveguide Filter Post-Process Tuning Using Capacitive Post

International audienceThis paper presents an air-filled substrate integrated waveguide (AFSIW) filter post-process tuning technique. The emerging high-performance AFSIW technology is of high interest for the design of microwave and millimeter-wave substrate integrated systems based on low-cost multilayer printed circuit board (PCB) process. However, to comply with stringent specifica-tions, especially for space, aeronautical and safety applications, a filter post-process tuning technique is desired. AFSIW single pole filter post-process tuning using a capacitive post is theoret-ically analyzed. It is demonstrated that a tuning of more than 3% of the resonant frequency is achieved at 21 GHz using a 0.3 mm radius post with a 40% insertion ratio. For experi-mental demonstration, a fourth-order AFSIW band pass filter operating in the 20.88 to 21.11 GHz band is designed and fabri-cated. Due to fabrication tolerances, it is shown that its perfor-mances are not in line with expected results. Using capacitive post tuning, characteristics are improved and agree with opti-mized results. This post-process tuning can be used for other types of substrate integrated devices