Expanding Functionality of Dual-Mode Resonators and Filters Using Nonuniform Transmission Line Structural Elements
A. V. Zakharov, Sergii Litvintsev
Abstract
The article provides an optimal synthesis of nonuniform transmission line structural elements, where resonant frequencies have a special placement. It is possible to improve the functionality of dual-mode resonators, which use these transmission segments. The optimal synthesis means that we obtain the special ratio between resonance frequencies of structural elements and have the minimum of parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m}={Z}_{\text {0max}}/{Z}_{\text {0min}}$ </tex-math></inline-formula> . We used the parametric synthesis for optimize proposed structure. It leads to stepped-impedance transmission line segments (SILS) which have the resonant frequencies with required placement and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m}= {m}_{\text {min}}$ </tex-math></inline-formula> . Two SILS pairs are synthesized. Two ends of one pair are open-circuited and the other pair is short-circuited. We added different stubs to the middle of proposed SILS. As result, four new dual-mode resonators with enhanced functions are designed. All dual-mode resonators have an extended stopband. The dual-mode resonators have reduced length relative to a half-wave resonator. The resonators allow increasing their operating frequencies. These resonators are very promising for use in dual-band BPF, so we can change the placement of one passband to another in the range <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.46 \le {f}_{2}/{f}_{1} \le 6.47$ </tex-math></inline-formula> . The measured and simulated results of two microstrip filters with new structural elements are offered.