Variable bandwidth planar coupled resonator filters utilizing tunable non-resonant node inverters

[摘要] ENGLISH ABSTRACT: This dissertation presents a novel design technique for designing microstrip staircase andpedestal substrate integrated waveguide (SIW) filters with tunable bandwidth. The design technique utilizes non-resonant nodes as inverters, allowing the inter-resonator coupling to be varied by varactor diodes.For the microstrip implementation, a circuit model of the proposed tunable nonresonantnode inverter (NI) to be implemented in parallel coupled line staircase filter is presented. Generalized synthesis design equations are formulated and dimensional designcharts are presented to aid designers in designing tunable staircase filters using NI.Reconfigurable second order and third order parallel coupled line staircase filters with constant absolute bandwidth are designed and measured.For the substrate integrated waveguide (SIW) implementation, the proposed tunablenon-resonant node inverter is implemented in a T-ridge pedestal SIW resonator basedfilter topology. A detailed dimensional analysis for integrating NI in T-ridge SIW filters is presented and design charts are formulated. A design procedure is proposed to designNI based T-ridge SIW filters with bandwidth control for a given filter specification. Asecond order T-ridge SIW filter with tunable bandwidth is designed and simulated.The designed reconfigurable filters using NI offer significant advantages over most ofthe other reconfigurable filter designs. The proposed synthesis method comprising ofdesign equations and design charts presents an insight into the dimensional informationrequired to design these filters for a given specification. Further, it reduces the relianceon full wave optimization and thus results in reduced computational cost and design time.The designed and measured prototype filters based on NI demonstrate negligible centrefrequency deviation as the bandwidth is tuned. The use of spatial biasing mechanismreduces the complexity of the filter designs as additional biasing circuit is not required to bias tuning elements

[发布机构] Stellenbosch University