Synthesis and full-wave EM Simulation of Ku-band direct-coupled 10th order dual-band Zolotarev bandpass filter and performance comparison with Chebyshev bandpass filter

In this paper; the authors performed synthesis and full-wave EM Simulation of 10^th order Ku-band direct coupled dual-band Zolotarev and Chebyshev bandpass filters. Achieser-Zolotarev filtering functions have uneven in-band ripple distribution characteristics. The ripple characteristics can be exploited by increasing the ripple level very high in unwanted frequency band. This will result in higher out of band rejection compared to Chebyshev filters. It is suggested that for satellites having split Ku-band downlink frequency plan (lower band and upper band), Zolotarev dual-band bandpass filter can be a better receive filter than conventional Chebychev filter for ground terminals/VSATs. Both filters were synthesized with indigenously developed software tool and full-wave EM simulation was performed using coupling matrix model in 3D EM simulator. Key performance parameters (insertion loss, group delay and passband ripple) of both filters were compared at both synthesis and EM simulation levels. It was observed that Zolotarev bandpass receive filter has higher out-of-band rejection and added suppression between dual passbands as an extra benefit compared to conventional Chebyshev filter. This filter can significantly improve receiver selectivity and sensitivity.