Triple-Mode Microwave Filters With Arbitrary Prescribed Transmission Zeros

Abstract

This article presents a new filter design for arbitrary placement of real frequency transmission zeros in triple-mode filters, allowing for either asymmetric or symmetric responses. Triple-mode filters can be viewed, in general, as a series combination of coupled resonators with non-adjacent couplings, allowing for the realisation of transmission zeros. The strength and phase of couplings dictate the transmission zeros locations. The arbitrary placement of transmission zeros requires controlling all amplitude and phase rations, i.e., the ability to realise both negative and positive couplings. In general, this necessitates the use of capacitive and inductive probe structures complicating the construction and hence increasing the filter cost. The method presented in this article enables arbitrary placement of transmission zeros using only inductive or only capacitive couplings structures. In addition, broadband filtering characteristics can be realised using triple-mode filters. Examples of several narrow and broadband bandpass filters are given indicating that this method is valid for most triple-mode structures.

Quasi-elliptic Triple Passband Filter Using Stub Loaded Step Impedance Resonator and Non-resonating T structure

“…For the sake of good stopband performances Quasi-Elliptic filters are always preferred over Chebyshev filter. Extracted pole filtering method and discriminating parallel coupling methods are some of the popular well established approaches to find the solution of controllable transmission zero (TZ) [1][2][3][4][5]. In a true sense, variety of methods are available to introduce TZ in Band-Pass Filter (BPF), dual or triple passband filters, or even for quad or penta band filters.…”

Design of a Compact Triple-Mode Dielectric Resonator BPF with Wide Spurious-Free Performance

“…In [26], a triple-mode DR using one TM 01δ mode and two HE 11 degenerate modes was designed to develop miniaturized BPFs. [29] tried to design triple-mode DR BPFs with controllable TZs. The novel triple-mode DR was designed off-centered in a metal cylinder, which was quite difficulty in the assembling and tuning of the BPF.…”