Development and Analysis of Compact Lowpass Filter for UWB Systems

This paper presents a developed compact lowpass filter which is devised by concatenating 'T' and inverted 'T' open stubs on a microstrip line. They are combined to enhance the bandwidth and also to improve the outband performance. Insertion loss of the developed filter is less than -0.15 dB and the return loss is -30 dB at 2.85 GHz. Stopband performance of the filter is less than -20 dB from 5.4 GHz to 7.8 GHz and provides -3 dB cut-off frequency at 4.5 GHz. The final dimension of the fabricated filter with the above features is only 16.17 mm (length) $imes$15.76 mm (width). The response of the developed filter has a good agreement with simulation response.