View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UTHM Institutional Repository EXPLORING MOORE SPACE-FILLING GEOMETRY FOR COMPACT FILTER REALIZATION EZRI MOHD A project report submitted as partial fulfilment of the requirements for the award of Degree of Master of Electrical Engineering Faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia JANUARY 2018 iii ACKNOWLEDGEMENT , Praise to The Almighty Allah, finally with His limitless kindness for granting me a healthy and strength to complete this work at last. For my beloved mother and father, my wife and sons for supporting me during my study. The author would like to express his sincere appreciation to his supervisor, Prof. Madya Dr. Samsul Haimi bin Dahlan for the support given throughout the duration for this project. The cooperation given by the Center for Applied Electromagnetic (Emcenter), Wireless and Radio Science Centre (WARAS) and Makmal Rekabentuk Papan Litar Tercetak Lanjutan (MRPLT) are also highly appreciated. Appreciation also goes to everyone involved directly or indirectly towards the compilation of this report. iv ABSTRACT A compact RF filter is desirable in modern wireless communication system. The Moore curves fill the defined space and compact the effective geometry within the same line length. The miniaturization rate of the planar microstrip filter can be accomplished by applying the Moore curves with defined iteration and yet still maintaining the acceptable performance. In this work, the 2 nd iterated Moore curves bandpass filter is designed to operate at center frequency, f center = 2.45GHz on RT/duroid ®5880 substrate. The first development stage investigate the characteristics of Moore resonator and consequently design Moore bandpass filter in next stage. The resulted mathematical equations revealed the correlation between Moore geometry with center frequency and bandwidth of the filter. The transmission response exhibited symmetrical response with two finite transmission zeros around center frequency to suggest a good selectivity and better rejection profile. Comparison between parallel coupled line filter, the Moore filter compacted the size about 90% while still presented reasonable performance. The fabricated Moore BPF has a good agreement with simulated result, thus our works is validated through realization. As a conclusion, the design of compact Moore BPF is successfully accomplished according to the required specification and the possible enhancement is also proposed in future work. v ABSTRAK Penapis gelombang mikro padat diperlukan dalam sistem komunikasi moden tanpa wayar. Lengkung Moore memenuhi ruangan tertentu dan memadatkan geometri berkesan dengan panjang talian yang sama. Kadar pengecilan penapis mendatar talian mikro boleh dicapai menggunakan lengkung Moore dengan pengulangan semula yang tertentu dan masih mengekalkan hasilan yang boleh diterima. Dalam kerja ini, penapis lulus jalur dengan pengulangan semula lengkung Moore sebanyak dua kali direka untuk beroperasi pada frekuensi pertengahan, fcenter = 2.45GHz di atas bahan RT/duroid ®5880. Pembangunan tahap pertama menyiasat ciri-ciri pengayun Moore dan seterusnya merekabentuk penapis lulus jalur Moore dalam tahap berikutnya. Penghasilan persamaan matematik mendedahkan perkaitan antara geometri Moore dengan frekuensi pertengahan dan lebar jalur penapis. Reaksi penghantaran mempamerkan tindakbalas bersimetri dengan dua penghantaran sifar terhad di sekitar frekuensi pertengahan untuk mencadangkan pemilihan dan profil penolakan yang baik. Perbandingan dengan penapis talian berkembar selari, penapis Moore memadatkan saiz kira-kira 90% serta masih mempamerkan prestasi yang munasabah. Penapis lulus jalur yang dibina mempunyai persetujuan yang baik dengan hasil simulasi, maka kerja kami disahkan melalui pembuatan. Sebagai kesimpulan, rekabentuk penapis lulus jalur Moore berjaya disempurnakan sewajarnya dengan spesifikasi yang ditetapkan dan kemungkinan penambahbaikan turut dicadangkan untuk kerja pada masa depan. vi TABLE OF CONTENTS TITLE i DECLARATION ii ACKNOWLEDGEMENT iii ABSTRACT iv ABSTRAK v TABLE OF CONTENTS vi LIST OF TABLES ix LIST OF FIGURES x LIST OF SYMBOLS AND ABBREVIATIONS xiv LIST OF APPENDICES xvi LIST OF PUBLICATIONS xvii CHAPTER 1 INTRODUCTION 1 1.1 Overview 1 1.2 Problem Statement 2 1.3 Objectives of the Project 2 1.4 Scope of the Project 3 1.5 Outline of the Report 4 CHAPTER 2 LITERATURE REVIEW 6 2.1 Introduction 6 2.2 Background of Fractal Geometry 6 2.3 RF Filter’s terminology 8 2.3.1 Bandpass definition 8 2.3.2 Selectivity 10 2.3.3 Quality factor, Q 11 2.4 Moore Fractal Resonator 12 2.5 Review of Fractal Resonator 13 2.5.1 Minkowski Resonator 13 vii 2.5.2 Hilbert Resonator 16 2.6 Coupling Coefficient of Coupled Line 17 2.6.1 Input and Output Coupling 17 2.6.2 Adjacent Resonator’s coupling 19 2.7 Class of Coupling 21 2.8 Review of Microwave Fractal Filter 22 2.9 Defected ground structure DGS 25 2.10 Conclusion 27 CHAPTER 3 METHODOLOGY 28 3.1 Introduction 28 3.2 Design and development study 28 3.3 Simulation 32 3.4 Fabrication 34 3.5 Measurement 36 CHAPTER 4 DEVELOPMENT OF MOORE FRACTAL RESONATOR 38 4.1 Design of Moore Fractal Resonator 38 4.2 Resonator’s dimension 38 4.3 Performances of Moore Resonator 40 4.4 Parametric Studies of Moore Resonator 42 4.5 Measurement of Moore Resonator 44 4.6 Conclusion 47 CHAPTER 5 DEVELOPMENT OF MOORE BANDPASS FILTER 48 5.1 Design Approach 48 5.1.1 Topology of Coupled Moore Resonator 48 5.1.2 Technique of Feeding 50 5.2 Parametric Studies on geometry’s dimension 51 5.2.1 Length of Moore open-line segment, x 51 viii 5.2.2 Distance gap between Moore resonators elements, g spacing 55 5.3 Moore Filter design at center frequency, fcenter = 2.45GHz 60 5.3.1 Optimized dimension of designed Moore fractal filter 60 5.3.2 Transmission Response 61 5.3.3 Surface current density 63 5.4 Comparison with Parallel-Coupled Line Filter 64 5.5 Moore Filter with DGS 66 5.6 Realization of Moore bandpass filter 70 5.6.1 Fabrication 70 5.6.2 Measurement 70 CHAPTER 6 CONCLUSION AND RECOMMENDATION 73 6.1 Conclusion 73 6.2 Recommendation 75 REFERENCES 76 APPENDIX 79 ix LIST OF TABLES 1.1 Scope of the proposed Moore filter 4 2.1 Fractal applications in different fields 8 2.2 Requirement of modern RF bandpass filter 8 4.1 Comparison of resonator’s size 40 4.2 Transmission characteristics of modelled resonators 41 4.3 Relation between resonant frequency and value of gap, g and width, w 43 4.4 Transmission characteristics of measured resonators 45 5.1 Transmission characteristic associated to variation of x and w 51 5.2 Validation of equation 5.1 between calculation and simulation 53 5.3 Validation of equation 5.2 between calculation and simulation 55 5.4 Summary of passband region attributes 62 5.5 Comparison of passband attributes 65 5.6 Simulated frequency suppression with different length of DGS transverse slot, s 68 5.7 Summary of comparison between measurement and simulation 72 6.1 Advantages and disadvantages of designed Moore bandpass filter 75 x LIST OF FIGURES 2.1 Examples of fractal geometries 7 2.2 Transmission coefficient, S21 of bandpass filter 9 2.3 Symmetrical response of bandpass filter 11 2.4 (a) Moore curves and (b) Hilbert curves with 2nd iteration level ( n=2) 12 2.5 Square dual-mode resonator with Minkowski’s iteration [8] 14 2.6 Relationship between L and g at 14GHz and transmission characteristic for 1 st iteration square Minkowski resonators. [8] 14 2.7 Transmission characteristics of square, 1 st and 2nd iteration Minkowski resonators. [8] 15 2.8 Transmission characteristics of 2 nd square Minkowski resonators. [8] 15 2.9 Open line λ/2 resonator to Hilbert fractal curves. [8] 16 2.10 Transmission characteristics of Hilbert Resonator. [8] 16 2.11 Types of coupling between resonators 17 2.12 Method used to determine the unloaded quality factor 18 2.13 Reference plane added to RLC equivalent circuit. [9] 19 2.14 response with input/output are weakly coupled [8] 20 2.15 Class of coupling between resonators. [8] 22 2.16 Transmission zero and selectivity 22 2.17 (a) 2 nd iteration and (b) 3 rd iteration of Hilbert filters and its transmission response [10] 23 xi 2.18 3rd order meandered line with (a) magnetic coupling and (b) electrical coupling and their transmission responses [11] 24 2.19 3rd order Hilbert filter with (a) magnetic coupling and (b) electrical coupling and their transmission responses. [11] 24 2.20 (a) 2nd and (b) 3rd iteration of Moore fractal and their transmission responses. [12] 25 2.21 (a) 3-Dimensional view of the DGS unit section. (b) The newly proposed equivalent circuit. [14] 26 3.1 Process flow of the project 39 3.2 Mesh solver and adaptive mesh refinement setting 33 3.3 Boundary conditions setting 33 3.4 Flow chart of fabrication process using photolithography technique 34 3.5 Laminator machine 35 3.6 UV exposure machine 35 3.7 The measurement outcome of network analyzer 37 3.8 Measurement setup to excite both ports of Moore resonator 37 4.1 Evolution of Moore fractal 38 4.2 Geometry of designed resonators, (a) half-wavelength resonator, (b) 1 st iteration Moore, (c) 2 nd iteration Moore. 39 4.3 Transmission characteristic of modelled resonators 40 4.4 Gap and width of Moore resonator 42 4.5 Transmission response with gap variation [w=2.5mm] 43 4.6 Resonant frequency with gap variation [w=2.5mm] 43 4.7 Relation between gap variation and resonant frequency 44 xii 4.8 Realization of the resonators, (a) half-wavelength resonator, (b) 1 st iteration