Fully Adaptive Multiband Bandstop Filtering Sections and Their Application to Multifunctional Components

Abstract

An original RF design approach for the realization of fully reconfigurable planar multiband bandstop filters (BSFs) is reported. The engineered RF filtering topology allows independent control of its stopbands in terms of center frequency and bandwidth. It exploits the in-series cascade of K spectrally agile N-notch filtering cells that are connected through K − 1 static impedance inverters to realize an N-band filtering transfer function with K th-order stopbands. Each of these multinotch cells is formed by N tunable resonators-center-frequency control-that interact with the same nonresonating node by means of different variable couplings-bandwidth control. Additional features of this tune-all multiband BSF architecture when compared with related prior-art devices are: 1) scalability to the synthesis of an arbitrary number of stopbands; 2) notch-spectral-merging capability into wider eliminated bands of the same order, which equivalently allows the intrinsic control, i.e., without RF switches, of the amount of active rejected bands; and 3) smaller physical size. The coupling-matrix modeling of the conceived multiband BSF scheme is presented. Moreover, its cointegration with other RF analog-processing actions in multifunctional components, such as bandpass filtering and power division, is investigated. For experimental-validation purposes, three UHF-band mechanically reconfigurable microstrip prototypes are developed and tested. They correspond to a dual-notch filter, a wideband bandpass filter with embedded notches in its tunable passband, and a Wilkinsontype power divider with inserted stopbands for dynamic multiinterference mitigation.Index Terms-Bandpass filter (BPF), bandstop filter (BSF), multiband filter, multifunctional circuit, notch filter, power divider, reconfigurable filter, tunable filter, wideband filter.

An Electronically Tunable Dual-Band Filtering Power Divider With Tuning Diodes Sharing Technique

“…Tunable filtering power dividers, integrating the two types of components, have attracted much attention in [7][8][9][10][11][12][13][14][15]. [7][8][9][10] present that filtering power dividers are tuned by varactors, each of them having one tunable passband.…”

“…A tunable filtering power divider, utilizing a piezoelectric linear actuator, is reported in [11], whereas the size of the actuator is very bulky. Filtering power dividers with multiple passbands are achieved in [12][13][14][15]. As presented in [12], the switching between two passbands is realized by PIN diodes, and the bands cannot be tuned continuously.…”

“…As presented in [12], the switching between two passbands is realized by PIN diodes, and the bands cannot be tuned continuously. Power dividers with dual-band/multi-band tunable filtering performances are achieved in [13][14][15]. Tunable filtering power dividers, reported in [14,15], integrate multi-functions of frequencies and bandwidths controlling for both pass and stopbands.…”

“…Power dividers with dual-band/multi-band tunable filtering performances are achieved in [13][14][15]. Tunable filtering power dividers, reported in [14,15], integrate multi-functions of frequencies and bandwidths controlling for both pass and stopbands. However, none of them employed electronically tuning technique which is most commonly used in modern wireless systems, for example using varactors.…”

“…However, none of them employed electronically tuning technique which is most commonly used in modern wireless systems, for example using varactors. The multiple tuning bands filtering power dividers are implemented by replacing fixed capacitors [13,14] or using mechanically-adjustable capacitors [15]. That requires a technical intervention on trimmers.…”