Development of planar filters and diplexers for wireless transceiver front ends

The central theme of this work is the design of compact microstrip bandpass filters and diplexers and the investigation of applications of these circuits in integrated transceiver RF front-end. The core of this thesis therefore presents the following stages of the work: - Analysis of coupled pseudo-interdigital resonators and lines; formulation of approximate transmission zero conditions and the investigation of coupling between these two resonators and related structures. - Development of compact, low loss and high selectivity microstrip pseudointerdigital bandpass filters. The design procedure of the filter consists of three simple steps, starting from the design of a parallel-coupled bandpass filter using the image parameter method applied to coupled microstrip lines. The development of compact microstrip diplexers composed of these filters uses the optimized common-transformer diplexing technique. An experimental verification of the developed filters and diplexers is made. - Investigation of the use of stepped impedance resonators (SIR) for the design of pseudo-interdigital bandpass filters with advanced characteristics. The design of compact dual-band filter using SIR. The investigation of possible improvement of the stopband of bandpass filters using bandstop generating structures. The application of SIR, defected ground structures (DGS), spur-lines, and opencircuited stubs in the design of compact bandpass filters with improved stopband. - The application of the proposed filters and diplexers in the design of integrated antenna filters and antenna diplexers. Improvement of performance of patch antennas, such as suppression of spurious harmonics of single-band antenna and improvement of bandwidth and selectivity of dual-band antenna, as a result of integration with filters. Separation of antennas’ bands and reduction of component count in integrated antenna diplexer

Development of turnable and miniature microwave filters for modern wireless communication

Due to the increasing demand for new wireless services and applications, the high level of integration and the coexistence of multi-standard (MS) or multi-band operations into a single device are becoming defining trends in designing microwave filters. This has driven considerable technological advances in reconfigurable/tunable and miniaturized filters. More specifically, reconfigurable/tunable filters that tune to different frequency bands instead of classical filter banks have great potential to significantly reduce the system size and complexity; while reducing the filter size becomes essential to achieve the highest degree of integration density in compact and portable wireless devices. In the light of this scenario, the objective of this dissertation is to develop the new design technologies, concepts and filtering configurations for tunable microstrip filters and compact passive microwave filters. To this aim, this dissertation is divided into two main parts. The first part (Part I) focuses on the designs of novel varactor-tuned microstrip filters with advanced performances. In this aspect, new topologies for realizing tunable lowpass and highpass filters are firstly developed. State-of-the-art performances, including wide tuning range, high selectivity with multiple transmission zeros, low insertion loss and compact size for all the tuning states are obtained in both of these filters. Secondly, two novel classes of tunable bandpass filters are presented. One of them is designed based on varactor-loaded parallel-coupled microstrip lines (PCML) and short-circuited stubs, which allows the lower passband edge together with two transmission zeros located around the lower passband skirt to be reconfigured separately. While the other tunable bandpass filter is iii constructed by the combination of tunable bandpass and lowpass filters, featuring both centre frequency and bandwidth tunabilities, as well as high selectivity with abundant transmission zeros. Furthermore, a new concept of tunable lossy filter is demonstrated, which attempts to achieve an equivalent high-Q tunable performance by using low-Q resonators. This concept makes the presented tunable combline filter interesting for some frequency-agile applications in which the low in-band loss variation and high selectivity are much desired while the absolute insertion loss can be a tradeoff. The second part (Part II) is devoted to the design of miniaturized passive microwave filters with improved characteristics. For this, the concept of artificial right-handed and left-handed transmission lines are applied to the signal interference filtering topology, which results in a compact circuit size and good out-of-band performance. In particular, for a further size reduction, such filter is implemented in the forms of multilayered structure by using liquid crystal polymer (LCP) technology. Additionally, another two types of miniaturized bandpass filters using stepped impedance resonators are demonstrated, which are implemented based on different fabrication processes (i.e. LCP bonded multilayer PCB technology and a standard planar PCB technology). Among their main features, the compact size, wide passband, broad stopband with multiple transmission zeros and circuit simplicity are highlighted. For all the proposed design techniques and filtering structures, exhaustive theoretical analyses are done, and design equations and guide rules are provided. Furthermore, all the proposed schemes and/or ideas have been experimentally validated through the design, implementation and measurement of different filters. The fabrication processes of multilayer technology utilized: liquid crystal polymer (LCP) technology and liquid crystal polymer (LCP) bonded multilayer printed circuit board (PCB) technology, are also demonstrated for reference. All of the results achieved in this dissertation make the proposed filters very attractive for their use in modern wireless communication systems.MultiWaves Project (PIRSES-GA-2010-247532) of the Seventh Framework Programme (FP7), European Commission

Development of tunable and miniature microwave filters for modern wireless communications

Due to the increasing demand for new wireless services and applications, the high level of integration and the coexistence of multi-standard (MS) or multi-band operations into a single device are becoming defining trends in designing microwave filters. This has driven considerable technological advances in reconfigurable/tunable and miniaturized filters. More specifically, reconfigurable/tunable filters that tune to different frequency bands instead of classical filter banks have great potential to significantly reduce the system size and complexity; while reducing the filter size becomes essential to achieve the highest degree of integration density in compact and portable wireless devices. In the light of this scenario, the objective of this dissertation is to develop the new design technologies, concepts and filtering configurations for tunable microstrip filters and compact passive microwave filters. To this aim, this dissertation is divided into two main parts. The first part (Part I) focuses on the designs of novel varactor-tuned microstrip filters with advanced performances. In this aspect, new topologies for realizing tunable lowpass and highpass filters are firstly developed. State-of-the-art performances, including wide tuning range, high selectivity with multiple transmission zeros, low insertion loss and compact size for all the tuning states are obtained in both of these filters. Secondly, two novel classes of tunable bandpass filters are presented. One of them is designed based on varactor-loaded parallel-coupled microstrip lines (PCML) and short-circuited stubs, which allows the lower passband edge together with two transmission zeros located around the lower passband skirt to be reconfigured separately. While the other tunable bandpass filter is constructed by the combination of tunable bandpass and lowpass filters, featuring both centre frequency and bandwidth tunabilities, as well as high selectivity with abundant transmission zeros. Furthermore, a new concept of tunable lossy filter is demonstrated, which attempts to achieve an equivalent high-Q tunable performance by using low-Q resonators. This concept makes the presented tunable combline filter interesting for some frequency-agile applications in which the low in-band loss variation and high selectivity are much desired while the absolute insertion loss can be a tradeoff. The second part (Part II) is devoted to the design of miniaturized passive microwave filters with improved characteristics. For this, the concept of artificial right-handed and left-handed transmission lines are applied to the signal interference filtering topology, which results in a compact circuit size and good out-of-band performance. In particular, for a further size reduction, such filter is implemented in the forms of multilayered structure by using liquid crystal polymer (LCP) technology. Additionally, another two types of miniaturized bandpass filters using stepped impedance resonators are demonstrated, which are implemented based on different fabrication processes (i.e. LCP bonded multilayer PCB technology and a standard planar PCB technology). Among their main features, the compact size, wide passband, broad stopband with multiple transmission zeros and circuit simplicity are highlighted. For all the proposed design techniques and filtering structures, exhaustive theoretical analyses are done, and design equations and guide rules are provided. Furthermore, all the proposed schemes and/or ideas have been experimentally validated through the design, implementation and measurement of different filters. The fabrication processes of multilayer technology utilized: liquid crystal polymer (LCP) technology and liquid crystal polymer (LCP) bonded multilayer printed circuit board (PCB) technology, are also demonstrated for reference. All of the results achieved in this dissertation make the proposed filters very attractive for their use in modern wireless communication systems

A Design of Compact Multi-harmonic Suppression LTCC Bandpass Filter

Filters are key components in RF front-end circuits and usually occupy much of the volume of the systems. Thus, reducing the size of filters is the main challenge in making RF systems compact. In addition to compact size, high performance is also desired. The presence of harmonics or spurious passbands is a fundamental limitation of microwave circuits, which can seriously degrade their performance and can be critical in certain applications. In this thesis, a simple and effective filter design method is proposed based on the structure of parallel short-ended coupled-line with capacitive loading for size reduction and ultra-broad rejection of the spurious passbands. It is achieved by adding lumped capacitors to the conventional coupled-line section such that the required length of the coupled-line can be largely reduced while maintaining approximately the same characteristics around the center frequency, and meanwhile the spurious passbands are excellently suppressed. In addition, the introduction of a cross-coupling capacitor into the miniaturized couple-line can create a transmission zero at the 2nd harmonic frequency for enhanced frequency selectivity and attenuation level. The aperture compensation technique is also applied to achieve a strong coupling in the coupled-line section. In order to examine the feasibility of the proposed structure, such a compact two-stage bandpass filter operating at 2.3 GHz with a fractional bandwidth of 10% was designed and realized with LTCC technology. Measured results are also provided, from which attractive features are observed experimentally as to size reduction and multi-harmonic suppression.Contents i Nomenclature iii List of Tables iv List of Figures v Abstract vii 요 약 ix CHAPTER 1 Introduction 1 1.1 Background and motivation 1 1.2 Organization of the thesis 5 CHAPTER 2 Filter Design Theory 6 2.1 Traditional bandpass filter design 6 2.2 Size reduction method 8 2.3 Realization of transmission zero 13 2.4 Aperture compensation technique 16 CHAPTER 3 Simulation, Fabrication and Measurement 18 3.1 Circuit simulation 19 3.1.1 One-stage bandpass filter design 19 3.1.2 Cascading for two-stage bandpass filter 24 3.2 Full-wave EM simulation and optimization 29 3.2.1 LTCC layout of the one-stage bandpass filter 29 3.2.2 Influence of the PCB size 32 3.2.3 Two-stage bandpass filter simulation 34 3.3 Fabrication and measurement 36 CHAPTER 4 Conclusion 42 References 44 Acknowledgement 4

Dual-band HTS filter using modified dual-spiral resonators

A symmetric dual-band filter with a centre frequency of 887 MHz is presented. The filter uses a modified structure of dual spiral resonators with interdigital capacitive load. At the same resonant frequency, the resonator can occupy an area of less than 2.75% of the area of the square loop resonator. Moreover, the resonator has a very low sensitivity to substrate thickness. The resonator structure also allows two types of couplings and, hence, allows application of cross-couplings with different signs to the direct couplings

Recent Trends on Dual- and Triple-Band Microwave Filters for Wireless Communications

In the past few years, several designs of dual- and triple-band microwave filters satisfying various objectives have been proposed for wireless communication. Several designs are new concepts, whereas others are inspired from previous works. The development trends of these designs can be reviewed from this compilation of studies. This paper begins with an explanation of dual- and triple-band microwave filters, followed by a discussion on several designs in terms of size, measurement, performance, and technology use. Among various designs, microstrip band-pass filters are extensively used because of their simple design procedures and because they can be integrated into circuits easily. Furthermore, most researchers use low frequencies in their designs because of the demands of current wireless applications. Finally, designs are proposed to produce compact microwave filters with good performance

Cross-coupled microstrip hairpin-resonator filters

Abstract-A new class of cross-coupled planar microwave filters using microstrip hairpin resonators is introduced. The realization of both the canonical and the cascaded quadruplet (CQ) filters is feasible. Coupling characteristics of four basic coupling structures encountered in this class of filters are investigated in the light of full-wave electromagnetic (EM) simulations. A four-pole cross-coupled filter of this type is designed and fabricated. Both the theoretical and experimental performance is presented. Index Terms-Cross coupling, hairpin resonator, microstrip filter

A review article of multi-band, multi-mode microstrip filters for RF, WLAN, WiMAX, and wireless communication by using stepped impedance resonator (SIR)

Filters are the basic part in wired, and wireless telecommunications and radar system circuits and they play an important role in determining the cost and performance of a system. The increasing demand for high performance in the fields of RF, WLAN, WiMAX and other wireless communications led to the great revolution in the advancement of the development of a compact microstrip resonator filter design. All these have made a vital contribution to both the required performance specifications for filters and other commercial requirements in terms of low cost, large storage capacity and high-speed performance. This review paper presents several design examples for multi-band, multi - mode microstrip filter resonators to satisfy RF, WLAN, WiMAX, UWB and other wireless communication frequency bands. To analyse the resonant frequencies odd - mode and even -modes can be used for the symmetrical structure. In general, the multi-mode resonators can be designed by using different methods like cross-coupling resonators Structure, and the allocation of the fundamental resonant frequencies of the resonator as stated by the Chebyshev's insertion loss function

Design and analysis of dual band pass filter

In this work, a dual-band meandered line bandpass filter is designed and simulated. The analysis is done while changing specific parameters, which includes mostly geometry and some material characteristics like dielectric thickness and metal types. This filter has a compact structure which is one of the main benefits. It has many applications in the industry and that is what makes work on it very interesting. Values for the S11 parameter are -20.70dB and -41.72 dB for 4.9GHz and 5.5GHz, respectively. Values for S12 parameter are -0.03dB and -2.91e-4dB for 4.9GHz and 5.5GHz, respectively

High aspect ratio transmission lines and filters

There are a significant number of microwave applications, where improvement of such qualities as manufacturing costs, size, weight, power consumption, etc. have attracted much research interest. In order to meet these requirements, new technologies can be actively involved in fabrication of microwave components with improved characteristics. One such fabrication technology is called LIGA (a German acronym with an English translation of lithography, electroforming, and moulding) that allows fabrication of high aspect ratio (tall) structures, and only recently is receiving growing attention in microwave component fabrication. The characteristics of high aspect ratio microstrip and coplanar waveguide (CPW) transmission lines are investigated in this thesis. Very low impedance high aspect ratio CPW transmission lines can be realized. A high aspect ratio microstrip folded half wavelength open loop resonator is introduced. Effective configurations for external and bypass gap coupling with open loop resonators are given. Filters with transmission zeros in the stopband, consisting of high aspect ratio single mode open loop resonators are presented to demonstrate the advantages of high aspect ratio structures in realizing lower external quality factors or tight coupling. The transmission zeros are created by novel coupling routings. Some of the filters are fabricated and the filter responses are measured to validate high aspect ratio coupling structures. High aspect ratio diplexers with increased channel isolation are also designed by appropriately combining filters with transmission zeros. A wideband bandpass filter design method, based on the electromagnetic bandgap (EBG) concept is introduced in this thesis. The wideband filters are miniaturized as a result of using the EBG concept in design. An EBG based wideband filter consisting of unit cells that are realized by using high aspect ratio CPW stepped impedance resonators is also presented. The main advantage of this approach is that the high aspect ratio CPW structures make short unit cells practically realizable, resulting in compact filter structure