Perfectly-matched bandstop filters using lossy resonators

Abstract

Normal realizations of bandstop resonators with finite unloaded Q suffer from degradation of performance due dissipation loss. In this paper it is shown theoretically that there exists a class of second-order networks which simultaneously exhibit an ideal bandstop resonance, with infinite stopband attenuation, and a perfect match at all frequencies. Theoretical analysis is backed up with experimental results for three different physical realizations.

Equivalent circuits and transmission zeros of the coupled square-loop resonator

“…1, consider an impedance matrix (Fig. 2 (b)) in which two 2-port networks, N (1) and N (2) , are connected in cascade. For this purpose, let an impedance matrix of N (k) (k = 1, 2) be defined as…”

“…Recently, in order to realize narrow bandstop filters like notch filters the coupled square-loop resonator was proposed in [1]. Thereafter, the design approach of such a resonator was discussed in [2]. Its approach is based on the assumption that the resonator is a lossy resonator circuit consisting of a series RLC circuit.…”

A Novel Single and Dual-Band Miniaturized Matched Band-Stop Filter Using Stepped Impedance Resonator

“…Various techniques have been proposed and developed in order to realize band-stop filter responses [1,2,7,9,[21][22][23][24][25]. The conventional technique to implement band-stop filters involves the use of shunt stubs with large circuits [1].…”

“…A new filter topology using lossy resonators has been introduced [2], where the topology can be used to partially compensate for the loss. The shortcoming of this type of filter is its large size, due to the second order resonator, which produces a single notch with an infinite attenuation.…”

Dual-band microstrip bandstop filter using dual-mode loop resonator

“…A microstrip dual-mode loop resonator BSF has been developed for the aforementioned requirements [1,2]. In recent years, various topologies for microstrip dual-mode loop-resonators (DMLRs) have been reported to elucidate the mechanism of coupling between the two degenerated modes, which is mainly determined by the feed-line structure or different types of perturbation [1][2][3][4][5]. In [3][4][5], dual-mode BSFs have been illustrated to obtain high selectivity, low insertion loss and good stopband attenuation.…”