A Compact Ultra-Wideband Multimode Bandpass Filter With Sharp-Rejection Using Stepped Impedance Open Stub and Series Transformers
Kanaparthi V. Phani Kumar, Vamsi Krishna Velidi, Rajkumar Rengasamy, T. Rama Rao
Abstract
This brief presents the analysis and design of an ultra-wideband bandpass filter (UWBPF) with four transmission zeros and seven poles. The UWBPF model consists of series transformers, coupled lines, and a shunt-stepped impedance open stub. The even-odd mode analysis method and scattering parameters theory are used to extract the closed-form equations for transmission zeros and poles of the proposed UWBPF. For validation, a prototype with a center frequency of 2.49 GHz is designed, simulated, and tested. The measured 3 dB fractional bandwidth is 103.2%, and the fabricated prototype occupies an area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.165\lambda _{g}^{2}$ </tex-math></inline-formula> . The circuit, full-wave simulated, and experimental results are in a good match.