Prototype of compact Microstrip lowpass filter for active phased antenna array with ultra-wide stopband using funnel shaped resonator

Abstract

This paper deals with the design of a prototype microstrip filter, which would be suitable for integration into active phased array antennas. This novel compact microstrip lowpass filter is based on funnel shaped resonator and semi elliptical patches. The proposed filter is designed, modeled, and fabricated to achieve an ultra-wide stopband with a sharp transition band. Furthermore, the LC equivalent circuit and transfer function of funnel shaped resonator are extracted. The cut-off frequency of proposed filter at −3 dB is 1.4 GHz and this filter has an ultra-wide stopband begins from 1.66 GHz to 17 GHz with the suppression level of 20 dB. Moreover, this lowpass filter has a sharp transition band of 0.26 GHz and compact size of 0.138 λg ×0.05 λg. The proposed structure is printed on Rogers_Rt 5880 and the measured results are coincided with the simulation results.