Design and Fabrication of a New Triple-Band Bandpass Filter with Adjustable Bandwidth Passbands Depending on Coupling
Obaida Oulad Haddar,
Mohammed Boulesbaa and
Tarek Djerafi
In this research, a simple design with a compact size of a triple-band bandpass filter (BPF) based on SIW is proposed. The proposed design consists of a main SIW cavity combined with two others-secondary SIW cavities. The three passbands of the proposed BPF are formed based on the center frequencies (CFs) of the four modes given by the main SIW cavity and two transmission poles (TP1 and TP2) achieved with the secondary SIW cavity. The SIW modes achieved with the main SIW cavity are TE101, TE201, and TE301 addition to the suppressed mode, and those modes are realized by the perturbation of seven metallic vias. The coupling of the TP1 with the suppressed mode realizes the first passband of the filter proposed with a bandwidth of 0.53 GHz. Vertical CPW slots are etched at the main SIW cavity for coupling TE101 and TE201 to form the second passband with a bandwidth of 1.3 GHz. Horizontal CPW slots are etched in the two rectangular secondary SIW cavities to join the TP2 with TE301 mode for realizing the third passband with a bandwidth of 1.2 GHz. Finally, an adjustable bandwidth filter with CFs of 6.9/10.1/13.3 GHz, respectively, has been achieved. Also, six transmission zeros (TZs) are achieved in the operation frequency range (6-16 GHz), which improves the selectivity of the filter. The proposed filter is modeled with an approximate equivalent circuit, and the prototype of the filter is fabricated and tested to demonstrate its excellent performance. A good agreement was realized among simulation, equivalent circuit LC model, and measurement S-parameters, which proves and validates the operation of the proposed triple-band BPF. The multiple advantages of the proposed filter, such as a simple structure, compactness (1.29λg × 1.62λg), selectivity, and high performance, make it a promising candidate for multi-tasking communication systems.
