A 28-GHz Compact Substrate-Integrated Waveguide Bandpass Filter With Defected Ground Structure Using TGV Technology

This paper presents a bandpass filter (BPF) based on substrate integrated waveguide (SIW) using modified through glass vias (TGVs) technology. Optimized TGV technology realizes fine feature size, proper via sidewall shape and good via surface profile, which accommodates SIW design rules in millimeter-wave (mmWave) band and precisely actualizes the SIW structure. In addition, a novel defected ground structure loading half-mode substrate integrated waveguide (HMSIW-DGS) unit is proposed to miniaturize the bandpass filter. The proposed DGS unit efficiently exploits the available area on the top metal layer of the HMSIW structure to increase the equivalent capacitance and inductance of the guided wave structure. Compared to the conventional DGS units, it actualizes smaller size at the same bandgap frequency. To prove the validity, the mmWave BPF with three cascaded HMSIW-DGS units is constructed and designed at 28 GHz. The proposed BPF is numerically optimized and experimentally verified, and the simulation results are in good agreement with the measured results. The measured results indicate insertion loss (IL) of 1.12 dB, 3-dB fractional bandwidth (FBW) of 27.7% and electrical dimensions of 0.37 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.12 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . In comparison with the existing designs, the proposed BPF shows the superior advantages of small size, low insertion loss, and advanced process flow.