Recent Techniques in Design and Implementation of Microwave Planar Filters

This paper details the techniques and initiatives made recently for improved response and simultaneous development of microwave planar filters. Although the objective of all the techniques is to design low cost filters with reduced dimensions, compact size with better frequency response, the methodological approaches are quite variant. The paper has gone through extensive analysis of all these techniques, their concept and design procedures

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

Microstrip dual mode multi-bandpass filters based on tree fractal slotted resonator for wireless communication

Dual mode microstrip multi-bandpass filter is proposed with tree fractal slot on a square patch resonator. The tree fractal slotted resonators are generated from conventional square patch using an iterative tree fractal generator method. A single square patch is used for realizing both dual and tri-bandpass filters exploiting the dominant, higher order and its corresponding degenerate resonant modes by the tree fractal iteration on the diagonal unequal slots on the square patch.The resonant peaks, transmission zeros and bandwidth of the pass bands can be tuned by varying the length and width of the fractal slot. By optimizing various parameters dual mode dual and tri-band pass filters are simulated, fabricated and measured. The proposed filter finds application in wireless communication devices and falls in the bands of GSM, WLAN, Bluetooth, Zigbee, WiMax and WiFi

A novel configuration of a miniature microstrip low pass filter

In this paper, we will present the design and the fabrication of a new configuration of a microstrip low pass filter. The originality of this work is that the final proposed filter is miniature and presents good performances in term of insertion loss around -0.15dB and it has a wide stopband until 7 GHz. The design of such filter is based on the use of optimization and tuning methods integrated into two electromagnetic solvers ADS and CST-MWS. After the fabrication, the final LPF structure is tested which give a good agreement between simulation results for the both solvers and measurement responses. The proposed filter has a cutoff frequency of 2.33 GHz which makes it suitable for many standards like DCS "Digital communication system", and UMTS "Universal Mobile Telecommunications System" bands. The final circuit presents an area of 20x20mm2

Microstrip diplexers with dual-mode patch resonant junctions

A conventional diplexer is made up of two channel filters which are connected to a transmission-line based signal distribution network. In this work, a novel diplexer has been proposed and designed using hairpin resonator filters that are joined together using a patch resonator. The patch being a dual-mode is made to resonate at the centre frequencies of the channel filters in corresponding modes. The patch functions as a signal splitter and at the same time as a resonant pole for each of the channel filters. A diplexer with the channel centre frequencies of 3.99 GHz and 4.39 GHz and 4% fractional bandwidth has been designed and tested. The simulated and measured results show very good agreements

A Novel Cpw Low Cost Lowpass Filter Integrating Periodic Structures

In this work, we propose a novel design of a planar CPW lowpass “LPF” filter based on the use of periodic structures. The periodic cells are formed from a rectangular slot repeated periodically. The originality of this work is to develop a new LPF structure which is simple, low cost for fabrication and easy to associate with others microwave planar circuits. The proposed and validated LPF is a compact planar filter structure. The final circuit is simulated and optimized by using two electromagnetic solvers, ADS (Advanced Design System) and HFSS (High Frequency Structural Simulator). After many series of optimization we have validated the final circuit into simulation by using optimization methods integrated into the both solvers, taking into account a high density of meshing in order to cover the whole circuit. The fabricated LPF circuit shows good agreement between simulation and measurement results in term of matching input impedance and insertion loss with a cutoff frequency of 1.25GHz. The entire area of the proposed LPF is 35x31 mm2

Multiband Bandstop Filter using an I-Stub-Loaded Meandered Defected Microstrip Structure

This paper presents a compact multiband bandstop filter (BSF) that utilizes an I-stub embedded within a meandered defected microstrip structure (MDMS). The proposed design for obtaining a single stopband is analyzed by using a transmission line network model. On the basis of the single stopband structure, we designed and fabricated a dual- and tri-band bandstop filters operating at 2.5/6.78 GHz and 1.98/5.60/7.78 GHz, respectively, thereby exploring the concept of generating as many stopbands by simply adding the same number of I-stubs. The proposed filter also features the possibility of tuning the resonant frequencies by varying the width of the I-stubs

Triple-band HTS filter using dual spiral resonators with capacitive-loading

The increasing demand on microwave spectrum for communication systems has been the driving force in the filter industry. Multiple filtering characteristics have become necessary for many filter designs in mobile and satellite applications. In this paper, a new cost-function for an optimization algorithm to achieve a multiple passband filtering function has been introduced. A high-temperature superconductor ten-pole filter with triple-band performance has been designed and fabricated to verify this algorithm. Each of the three passbands has a fractional bandwidth of approximately 0.26%

Design, Modelling and Implementation of Several Multi-Standard High Performance Single-Wideband and Multi-Wideband Microwave Planar Filters

The objectives of this work are to review, investigate and model the microwave planar filters of the modern wireless communication system. The recent main stream of microwave filters are classified and discussed separately. Various microwave filters with detailed applications are investigated in terms of their geometrical structures and operational performances. A comprehensive theoretical study of microwave filters is presented. The main types of microwave filters including the basic low-pass filters such as Butterworth and Chebyshev filters are fully analysed and described in detail. The transformation from low-pass prototype filters to high-pass filters, band-pass filters and band-stop filters are illustrated and introduced. Research work on stepped impedance resonator (SIR) and asymmetric stepped impedance resonator (ASIR) structure is presented. The characteristics of λg/4, λg/2 and λg (λg is the guided wavelength of the fundamental frequency in the free space) type SIR resonators, and the characteristic of asymmetric SIR resonator are categorized and investigated. Based on the content mentioned above, novel multi-standard high performance asymmetric stepped impedance resonator single-wideband and dual-wideband filters with wide stopbands are proposed. The methodologies to realize wide passband and wide stop-band filters are detailed. In addition, multi-standard high performance triplewideband, quadruple-wideband and quint-wideband filters are suggested and studied. The measurement results for all prototype filters agree well with the theoretical predictions and simulated results from Ansoft HFSS software. The featured broad bandwidths over single/multiple applicable frequency bands and the high performances of the proposed filters make them very promising for applications in future multistandard wireless communication