An Improved Equivalent Circuit Model for CSRR-Based Bandpass Filter Design With Even and Odd Modes

We present a new equivalent circuit model that incorporates the resonances and transmission zeros in terms of even and odd modes for CSRR-based bandpass filter (BPF) design. The circuit model and three resonance characteristics are consistent with the geometry of the CSRR-based BPF. The variations of distance ratio, related gap and loop number are investigated. The good performance of lower insertion loss (0.87 dB), deeper and symmetric transmission zero level (- 53.20 dB) , wider bandwidth (fractional BW 89.4%) and wider stopband (extended to 2.9 f₀ below - 28.5 dB rejection level) at the central frequency f₀ = 1.88 GHz are achieved by this methodology.