Microstrip lowpass filter with ultra-wide stopband using triangular shaped CMRC

In this paper, a microstrip lowpass filter with ultra-wide stopband is proposed. To achieve a wide stopband, the semicircle stepped impedance is connected in series with the triangular shaped compact microstrip resonance cell (CMRC). The lowpass filter with 3 dB cut-off frequency at 2.38 GHz and stopband region with the attenuation level better than –21 dB from 2.7 to 23 GHz has been designed, fabricated and measured. The filter has the transition band of 0.45 GHz. There is a good agreement between the simulated and measured results.