Improved performance step impedance lowpass filter

Performances of the conventional Butterworth step impedance lowpass filters (LPF) are significantly improved by placing transmission zero either closer to the cut-off frequency (fc) or away from it. It is achieved by using transverse resonance width of the capacitive line sections. We report method of designing transverse resonance type LPF (TR-LPF) for 5 to 11-pole filters. At fc = 2.5 GHz, we obtained selectivity in the range 113.3–56.66 dB/GHz and 20–60 dB rejection BW in the range 9.61–7.29 GHz. The TR-LPF can suppress the stopband signal by 60 dB up to 5fc. Insertion loss in passband is within 0.72 dB. Improved performance of TR-LPF can be designed for fc up to 7.5 GHz.