A Very Compact Miniaturized GaAs Bandpass Filter For 5GHz Band WLAN

대역통과필터는 마이크로파시스템에서 특히 현대 무선 통신 시스템에서 많이 응용하고 있다. 대부분의 이동통신 시스템에서 단일 송수신 칩 구현을 위하여 작은 사이즈와 낮은 가격, 그리고 저지대역에서 높은 감쇠특성을 가지는 MMIC 대역통과 필터를 필요로 한다. 본 논문에서 종단 단락 된 평행 결합선과 집중 capacitor를 이용하여 새로운 소형화된 GaAs 대역 통과필터를 제안 하였다. 위에 언급하여 제안한 구조를 이용하여 GaAs 필터의 사이즈는 GaAs 필터에 있은 평행결합선의 전기적인 길로 결정할 수 있다. 그래서 평행 결합선의 길을 줄이는 방법을 통하여 매우 작은 필터를 구성할 수 있은 것이다. 불필요한 신호를 억제하기 위해서 inter-stage 선로를 서로 이웃한 공진기의 사이에서 삽입한다. 이 inter-stage선로는 반드시 필요한 회로 부분으로 중요한 역할을 하고 있다. 그리고 설계된 GaAs 필터는 넓은 높은 저지대역폭을 가지고 있다. 제작된 대역통과필터의 실제 size는0.54×0.78mm 까리 초소형화 되었다. 필터를 제작해서 측정된 결과는 본문에서 설계된 이론치와 잘 일치하었다.Contents I Nomenclature II List of Figures III Abstract V 요 약 VII Chapter 1 Introduction 1 Chapter 2 Size Reduction Method for the Quarter-wavelength Transmission Line 4 2.1 Introduction 4 2.2 Size Reduction Method 6 2.3 Hirota’s size reduction method for λ/4 transmission line 7 Chapter 3 Bandpass Filter Design Theory 13 3.1 Introduction 13 3.2 Size-reduced Bandpass Filter 14 Chapter 4 Simulation and Measurement Results 24 Chapter 5 Conclusion 33 References 34 Acknowledgement 3

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

An Extremely Miniaturized Microstrip Bandpass Filter

Miniaturized microwave bandpass filters are always in demand for systems requiring small size and light weight. This demand is much increased recently by rapidly expanding cellular communication systems. In this thesis, a novel miniaturized UHF bandpass filter using diagonally end-shorted coupled lines and lumped capacitors is proposed. With this new method, the size of the bandpass filter can be reduced to just a few degrees without sacrificing the characteristics of the conventional filter at the operating frequency. In addition to it, this new filter also shows a wider upper stopband. A two-stage bandpass filter using this method has been designed and fabricated at a midband frequency of 300 MHz with electrical length of 5.2°. Both theoretical and experimental performances are presented. The total physical size of the fabricated filter is only 17 mm, 95% reduced compared with the conventional one. The fabricated filter exhibits good filtering characteristics with a wider upper stopband. This extremely miniaturized band-pass filter holds promise for MMIC (Monolithic Microwave Integrated Circuits) technologies which can be applied to mobile communications and other applications.Contents = i Nomenclature = ii List of Tables = iii List of Fig.s = iii Abstract = v CHAPTER 1 Introduction = 1 CHAPTER 2 The theory of size reduction method = 4 2.1 Introduction of filters = 4 2.2 Size reduction method = 5 2.2.1 Hirota’s size reduction method for λ/4 transmission line = 6 2.2.2 New size reduction method = 8 2.3 Bandwidth of the bandpass filter = 11 2.3.1 The coupling coefficient and the bandwidth. = 12 2.3.2 The electrical length and the bandwidth. = 19 CHAPTER 3 Simulation and experiment results = 22 3.1 A design of a 300 MHz bandpass filter = 22 3.2 The effect of the inter-stage part = 24 3.3 Fabrication and measurement = 27 3.4 The harmonic suppression = 31 CHAPTER 4 Conclusion = 34 References = 35 Acknowledgement = 3

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

Electronically reconfigurable wideband microwave filters

Many systems require multi function capability in the filter aspects of systems; the method currently used is filter banks which take up a lot of board space. It is thought that reconfigurable filters hold the key to replacing filter banks in order to save board space and thus potentially increasing functionality of the systems. The aim of this research is to develop electronically reconfigurable microwave filters for future communication systems. The project investigates some key design issues of reconfigurable filters. Circuits were modelled and full-wave electromagnetic simulations were performed for the investigation. Experimental work was carried out to demonstrate advanced reconfigurable microwave devices. The components used in each concept investigated were pin diodes due to their superior performance in wideband and high frequency applications. Firstly a single coupled line concept was looked at for bandwidth reconfigurability. This concept was then further developed for industrial applications by simply cascading these sections to obtain a high selective filter. A design method was developed for any number of cascades both with and without an impedance transformer; the use of LCP was used to increase flexibility due to its desirable characteristics. The most desirable outcome would be filter to simultaneously control bandwidth and frequency. In order to tackle this issue the coupled line concept was adapted to incorporate frequency tunability, along with a design method being presented. Furthermore, a cascaded highpass/ lowpass filter was also explored for this concept for added flexibility in the design of a filter capable of control of both bandwidth and center frequency

SBIR: development of ferroelectric filters

Issued as final reportnGima

An Overview of Filter Integrated Switch (FIS) for RF and Microwave Applications

Integrating multiple devices into one single device is an effective method to reduce circuit size, mismatching loss, and fabrication cost. Radio frequency (RF) and microwave device integrated with filter have become a popular design concept in the recent years. In this paper, an overview of the filter integrated switch (FIS) for RF and microwave applications is presented based on previously published studies and research journals starting from 2006 until 2016. This paper also emphasizes the use of previous and current development of filter integrated switches which mainly covers the fundamental concept on the FIS, the research trends in designs and developments. At the end, this paper reports on the variety of applications that can greatly benefit from FIS and some challenges and factors that need to be considered in designing and development of filter integrated switches

Reconfigurable and multi-functional antennas

This thesis describes a research into multi-frequency and filtering antennas. Several novel antennas are presented, each of which addresses a specific issue for future communication systems, in terms of multi-frequency operation, and filtering capability. These antennas seem to be good candidates for implementation in future multiband radios, cognitive radio (CR), and software defined radio (SDR). The filtering antenna provides an additional filtering action which greatly improves the noise performance and reduces the need for filtering circuitry in the RF front end. Two types of frequency reconfigurable antennas are presented. One is tunable left-handed loop over ground plane and the second is slot-fed reconfigurable patch. The operating frequency of the left handed loop is reconfigured by loading varactor diodes whilst the frequency agility in the patch is achieved by inserting switches in the coupling slot. The length of the slot is altered by activating the switches. Compact microstrip antennas with filtering capabilities are presented in this thesis. Two filtering antennas are presented. Whilst the first one consists of three edge-coupled patches, the second filtering antenna consists of rectangular patch coupled to two hairpin resonators. The proposed antennas combine radiating and filtering functions by providing good out of band gain suppression