Compact ultra‐wideband bandstop filter using capacitive loads

Abstract

A compact UWB band‐stop filter (BSF) using capacitive loads is proposed. In contrast to its traditional counterparts, this proposed BSF only consists of two capacitors and a short‐ended coupled line (C‐section). By introducing capacitors inside the C‐section and between two ports, respectively, cross‐coupling and source/load coupling are introduced to create up to four transmission zeros. Meanwhile, shunt capacitive effect of loaded capacitors can further reduce the length of C‐section. After working principle and design method of this proposed BSF are well‐illustrated, a prototype with 20 dB fractional bandwidth of 110% at 4.24 GHz is finally designed and fabricated. It occupies only 0.45λg × 0.061λg, where λg is the guided wavelength at the centre frequency.

Keywords

• compact UWB band‐stop filter
• capacitive loads
• C‐section
• cross‐coupling
• loaded capacitors
• compact UWB BSF