Tune-all wideband planar filters for KAT-7

[摘要] ENGLISH ABSTRACT: A new type of widebandlters, with tunability in both the centre frequency and bandwidth,is presented in this thesis. Theselters are based on perturbed ring-resonators incascade, while varactor diodes are used for electronic tuning.The Karoo Array Telescope (KAT-7) requires a front-endlter that has the abilityforne-tuning the response after fabrication, in order to obtain the designedlteringresponse. Not only are tune-all characteristics required, but also wide bandwidth,atpassband, high selectivity and implementation in microstrip technology.In this thesis an extensive investigation of both tunable and widebandlters is done, inorder tond a possible solution for the KAT-7 speci cations. Following this investigation,it is concluded that no suitable design approach for tune-all widebandlters, implementedin microstrip, exists in current literature.Therefore, this thesis proposes a new type oflter along with the development of acomplete design procedure. Twolters are designed with this procedure to achieve therequired passband from 1.2 to 1.95 GHz (i.e. a fractional bandwidth of 49%). In the rstlter design, with a network consisting of 4 cascadedltering-sections, the centrefrequency is 5% tunable and the bandwidth 17.5%. With the secondlter consisting of 6cascadedltering-sections, higher selectivity is achieved but with lower return loss. Herethe centre frequency is 8.5% tunable and the bandwidth 18.8%. The theoretical resultsare validated with the fabrication of bothlters.This design is very unique in that it achieves wide bandwidth, is realisable in microstripand most importantly is tunable in both the centre frequency and bandwidth.An advantage of this design procedure is that full wave simulations are minimal, due tothe complete circuit models used for optimisation.

[发布机构] Stellenbosch University