A Compact Millimeter-Wave On-chip DGS-based Bandstop Filter with Two Transmission Poles in CMOS Technology

A compact size millimeter-wave on-chip defected ground structure (DGS)-based bandstop filter (BSF) is proposed and implemented in 0.18-μm CMOS technology. The proposed BSF is realized with T-shape DGS. In combination with the series resonance circuits, the proposed design realizes two transmission poles: one at either side of parallel resonance. Despite the compact size, the proposed BSF still maintains higher quality (
$Q$
) factors and group delay. The proposed BSF optimized at 52 GHz frequency is fabricated and tested. The active area of the fabricated prototype without pads is 0.0129 mm
²
which is only 50% of the size of a wideband BSF recently proposed in a similar technology [8] and [16]. The measured loaded and unloaded
$Q$
-factors are 4.57 and 20.55, respectively.