Compact Hybrid CSRR‐DGS Bandstop Filter With Enhanced Suppression for 5G n1 Band

ABSTRACT With the rapid deployment of fifth‐generation (5 G) mobile communication technology, radio frequency (RF) front‐end components require higher performance to suppress interference in the n1 frequency band (1920–2170 MHz) coexisting systems. This paper proposes a compact bandstop filter (BSF) based on complementary split‐ring resonator (CSRR) integrated with defected ground structure (DGS), occupying dimensions of 0.58λg × 0.72λg. Experiments results demonstrate operation at 2.07 GHz center frequency with 24.2% fractional bandwidth (1.82–2.32 GHz), achieving > 23.6 dB stopband suppression and < 0.5 dB passband insertion loss. An equivalent circuit model based on transmission line theory exhibits close agreement with measurements, confirming the hybrid structure′s effectiveness in suppressing spurious responses. This design achieves a balance between compact dimensions and high stopband performance, offering an efficient solution for 5 G base stations.