Cascaded trisection linear-phase filter

This paper presents a new method to design Cascaded trisection(CT) linear-phase filters. In order to verify this method, we designed a band-pass HTS filter by using resonator deformation and improvement to achieve the CT structure and introducing a group delay equalizer to equalize group delay within the pass-band. Eventually we achieve an eight-order HTS filter with center frequency 899.5 MHz, bandwidth 19 MHz, band insertion loss better than 0.2 dB, band rejection better than 50 dB within 0.6 MHz at higher stop-band, group delay fluctuation better than 1.5 ns within 50% of the pass-band. All these parameters would meet the requirement of linear phase filter.