Sharp Rejection Wideband Band Pass Filter in Suspended Substrate Stripline Realization

This article presents a very sharp rejection band pass filter (BPF) design techniques in suspended substrate strip line (SSS). The proposed band pass filter is split into two parts viz., high pass filter (HPF) and low pass filter (LPF) and both are designed separately in SSS and integrated by providing slight matching between two and made a single circuit. The same generalized Chebyshev LPF prototype has been considered for both the design. Then Richard's frequency transformation is applied to map the LPF prototype to LPF as well as HPF respectively in distributed domain using commensurate transmission lines. Then Kuroda's identities applied to flip the elements in the shunt branch of HPF. This design technique also redistributes (n-3) finite transmission zeroes into different frequency zones near the cutoff frequency (±ω_o) to maintain rejection hump better than 100 dB at both the side of the BPF. Measured results of proposed filter are found in good agreement with the simulation response.