Application of Capacitive-Loading Size-Reduction Techniques to Multi-Band and Reconfigurable-Bandwidth Signal-Interference Planar Bandpass Filters

This paper examines the applicability of capacitive-loading-based size-reduction techniques to wide band and multi-band signal-interference planar filters. Using this approach, a miniaturized 0.96/1.84-GHz dual-band bandpass filter (BPF) shaped by a branch-line-coupler-type transversal filtering section (TFS) is built and measured. It features a 55.4% area decrease in relation to its fully-planar counterpart. Besides, a compact-size 2-GHz reconfigurable-bandwidth BPF made up of two TFSs loaded with switchable stubs is designed. Its layout shows a size reduction of 56.0% when compared to its classic precursor. For both design examples, the trade-off existing between miniaturization level and narrowing effect of their transfer function is discussed.