Microwave planar filters with multi-mode resonators

REZIME: Predmet istraživanja ove doktorske disertacije su mikrotalasni filtri propusnici opsega učestanosti, realizovani pomoću rezonatora sa više rezonantnih učestanosti, koji su implementirani u planarnoj štampanoj tehnici. S obzirom na stalan razvoj bežičnih tehnologija, kao što je peta generacija mobilnih mreža, postavljaju se zahtevi za projektovanje mikrotalasnih komponenti za šire propusne opsege, na višim učestanostima, čime bi se osvario brži prenos podataka, veći kapacitet mreže i bolja energetska efikasnost. Mikrotalasni filtri, kao deo nove tehnologije pete generacije mobilnih sistema, predstavljaju pravi izazov za projektante, o čemu svedoče brojne objavljene publikacije. Shodno sve strožijim specifikacijama tehnologije u razvoju, nameće se potreba za novim realizacijama mikrotalasnih filtara željenih performansi. U cilju zadovoljenja zahteva kao što su novi frekvecijski opsezi, širina kanala, primopredajnici sa više opsega, rekonfigurabilnost primopredajnika, minijaturizacija prenosivih uređaja uz uslov da ne dođe do neželjene sprege delova sitema, ostavlja se prostor za dalja istraživanja u oblasti projektovanja kako rezonatora, tako i filtara na mikrotalasnim učestanostima. Da bi se zadovoljili navedeni kriterijumi nove tehnologije, u okviru disertacije ispituje se nov način realizacije rezonatora sa dve ili tri rezonantne učestanosti. Razmatra se štampanje rezonatora u više slojeva planarne strukture u cilju smanjenja zauzeća štampane pločice. Korišćenje višeslojane strukture doprinosi minijaturizaciji sa jedne strane samog rezonatora, a sa druge strane celog filtra, uz težnju da se očuva ili poboljša karakteristika filtra. U razmatranom istraživanju, višeslojna realizacija je ostvarena spajanjem dve mikrotrakaste strukture masama, čime se masa postavlja u centar strukture. Predloženi rezonatori koriste se za projektovanje nove klase planarnih filtara koji imaju jedan ili više propusnih opsega. Za svaki propusni opseg filtra koristi se po jedan rezonator, a sprega između susednih opsega je izbegnuta ostavljanjem potrebnog rastojanja na štampanoj pločici. Osnovni cilj nove realizacije filtra je mogućnost nezavisnog vi podešavanja svakog od opsega. Shodno tome, ispitituje se optimalno rastojanja između rezonatora za različite propusne opsege.ABSTRACT: The scope of the research, presented in this doctoral dissertation, is the microwave bandpass filter design using multi-mode resonators implemented in planar technology. Due to the constant development of wireless technologies, such as the fifth generation of mobile networks, requirements for the microwave components design for wider pass bands are set up for higher frequencies, thereby securing faster data transfer, greater network capacity and better energy efficiency. As evidenced in numerous publications, microwave filters, as a part of the new technology of the fifth generation of mobile systems, present a real challenge for designers. In accordance with increasingly stringent technology specifications in development, the need for new microwave filter realizations of desired performance is imposed. In order to meet requirements such as new frequency bands, channel bandwidth, multi-band transceivers, reconfigurable transceivers, portable devices miniaturization without unwanted coupling between the parts of the system, a space for further resonators and filters design research remains. In order to satisfy the stated new technology criteria, in the framework of this dissertation, a new method of the resonator realization with two or three resonant frequencies is examined. In order to reduce the printed circuit area occupation, resonators printed in several layers of the planar structure are considered. The use of multilayer structure contributes to resonator miniaturization on one side, as well as for the entire filter, while preserving or improving the filter characteristics. In this study, the multilayer realization was achieved by combining two microstrip structures which are connected by a common ground, which is placed in the center of the structure. The proposed resonators are used for a new class of planar filters design with one or more pass bands. One resonator is used for each pass band of the filter, and the coupling between the adjacent pass bands is avoided by leaving the required distance on the printed circuit area. The main aim of the new filter realization is the possibility to independently tune each of the pass bands. Consequently, optimal distances between the resonators for different pass bands are examined. ix Due to the geometric complexity of the proposed filters, the analysis was performed in threedimensional electromagnetic software. For more efficient filter characteristics examination and for reducing the time needed for the analysis, equivalent circuits of the resonators and filters are proposed. The introduced equivalent circuits allow analysis of changing individual filter parameters on its frequency characteristics, almost instantaneously. Using the equivalent circuits significantly reduces the time required for filter design, since it allows the optimization of filter parameters at the microwave circuit level