I Frequency Agile Antenna Integrated With Band Pass

Transcript

i FREQUENCY AGILE ANTENNA INTEGRATED WITH BAND PASS FILTER AHMAD MARWAN BIN MOHAMAD DAHLAN UNIVERSITI TEKNOLOGI MALAYSIA ii FREQUENCY AGILE ANTENNA INTEGRATED WITH BAND PASS FILTER AHMAD MARWAN BIN MOHAMAD DAHLAN A thesis is submitted in fulfilment of the requirements for the award of the degree of Master of Engineering (Electrical) Faculty of Electrical Engineering Universiti Teknologi Malaysia OCTOBER 2013 iii To my beloved parents Mohamad Dahlan Omar and Norlida Nordin, my lovely wife and daughter and finally my cherished siblings. iv ACKNOWLEDGEMENT In the Name of ALLAH The Most Benevolent, The Most Merciful Alhamdulillah, praise be to ALLAH s.w.t to Whom we seek help and guidance and under His benevolence we exist and without His help this project could not have been accomplished. I would like to express my deepest appreciation and gratitude to my supervisor, Dr Muhammad Ramlee bin Kamarudin, for all the support, guidance and time he given to me during my research. I am most thankful to my family members especially my parents and fiancé for their nonstop encouragement. Not to be forgotten my fellow researches in wireless technology, Norsiha, Rajaei, Musyidul Izdam, Arsany, Zairil, Faizal and Amirudin for the knowledge and help they share. Not to be forgotten all Wireless Communication Centre (WCC, FKE UTM) members (staffs and research students) for their readiness to lend a hand in time of need. Finally, thank you to all who has contributed to this research directly and indirectly. v ABSTRACT In the era of wireless communication, new problem arises when user’s attention increases together with new development of wireless applications. The limited frequency spectrum, which allows only one application to operate at the same time and frequency, has created resource issue for the wireless communication industry. Hence, new frequency agile technologies such as Software Define Radio and Cognitive Radio systems are being developed. One of the requirements of this type of application is an antenna system that is able to change its operating frequency as instructed by the back end system. This research explores the possibility of integrating band pass filters to manipulate the operating frequency of a broadband antenna. RF diode, inductors and capacitors are used as switching mechanism to actively change the operating frequency. Based on the spectrum allocation in Malaysia, frequency range from 1GHz to 6GHz was chosen due to the allocation of many types of communication applications such as mobile applications, unlicensed band and satellite communication. A proof of concept was done for active switching at 1.3GHz and 2GHz of the antenna prototype. Another structure was fabricated to implement frequency reconfigurability operation at 1.3GHz, 2GHz, 3GHz, 4GHz, 5GHz and 6GHz using copper strips instead of active elements. Simulated and measured results showed good agreement for 1.3GHz – 2GHz active switching prototype while 1.3GHz – 6GHz copper strip prototype shows minor shifts and degradation at high frequencies in measured result. From the data collected in this research, band pass filter integrated antenna shows high potential to be used as frequency agile antenna with active switching capability. The results from simulation and measurement of fabricated structures are analyzed and discussed in detail in this thesis. This research contributes to the development of frequency agile antenna design for future frequency agile application. vi ABSTRAK Pada zaman perhubungan tanpa wayar, wujud permasalahan baru apabila teknologi tanpa wayar terus mendapat perhatian pengguna dan pelbagai aplikasi baru yang sedang dibangunkan. Jalur frekuensi yang terhad membolehkan hanya satu aplikasi beroperasi pada waktu dan frekuensi yang sama telah menghasilkan isu sumber dalam industri perhubungan tanpa wayar. Maka, teknologi frekuensi tangkas baru sedang dibangunkan contohnya Software Defined Radio dan juga Cognitive Radio. Salah satu keperluan teknologi seperti ini adalah sistem antena yang mampu mengubah frekuensi operasinya seperti yang diarahkan oleh sistem belakang. Penyelidikan ini meneroka kebarangkalian untuk mengawal frekuensi operasi sebuah antena jalur lebar dengan mengintegrasikan penapis lulus jalur. Diod frekuensi radio (RF), peraruh dan kapasitor digunakan untuk mengawal frekuensi operasi secara aktif. Berdasarkan peruntukan spektrum di Malaysia, julat frekuensi dari 1GHz hingga 6GHz telah dipilih kerana kebanyakan aplikasi komunikasi berada dalam julat ini seperti komunikasi bergerak, jalur tanpa lesen dan komunikasi satelit. Satu bukti konsep telah dijalankan bagi membuktikan keupayaan suis aktif pada operasi 1.3GHz dan 2GHz. Sebuah struktur prototaip lain telah difabrikasi untuk operasi 1.3GHz, 2GHz, 3GHz, 4GHz, 5GHz dan 6GHz dengan menggunakan jalur tembaga berbanding penggunaan unsur-unsur aktif. Keputusan dari simulasi dan yang diukur menunjukkan persetujuan yang baik bagi prototaip operasi 1.3GHz – 2GHz manakala bagi operasi 1.3GHz – 6GHz, perubahan kecil dan kemerosotan dapat diperhatikan di frekuensi tinggi pada keputusan yang diukur. Dari data yang dikumpul dalam penyelidikan ini, antena yang diintegrasi dengan penapis lulus jalur menunjukkan potensi yang tinggi untuk digunakan sebagai antena tangkas jalur dengan keupayaan pensuisan aktif. Keputusan yang diperoleh dari simulasi dan pengukuran struktur yang telah difabrikasi dianalisa dan dibincangkan dengan terperinci di dalam tesis ini. Penyelidikan ini menyumbang dalam perkembangan rekaan antena tangkas frekuensi untuk aplikasi tangkas frekuensi masa hadapan. vii TABLE OF CONTENTS CHAPTER 1 TITLE PAGE DECLARATION ii DEDICATION iii ACKNOWLEDGEMENT iv ABSTRACT v ABSTRAK vi TABLE OF CONTENTS vii LIST OF TABLES xi LIST OF FIGURES xii LIST OF SYMBOLS xvi LIST OF ABBREVIATIONS xvii LIST OF APPENDIX xviii INTRODUCTION 1 1.1 Background 1 1.2 Problem Statement 3 1.3 Objectives 4 1.4 Scope of Work 4 1.4.1 Literature Review 5 1.4.2 Structure Design, Modification, 5 Simulation and Optimization 1.4.3 Antenna Fabrication 5 1.4.4 6 Structure Testing and Measurement 1.5 Thesis Outline 6 viii 2 THEORY AND LITERATURE REVIEW 7 2.1 Antenna 7 2.1.1 Basics 8 2.1.2 Types of Antenna 11 2.1.3 Performance Enhancement on Printed 13 Antennas 2.2 Microwave Filter 2.2.1 Printed Band Pass Filter 2.3 Reconfigurable Antenna 2.3.1 Frequency Reconfigurable Antenna 14 16 19 19 2.4 Frequency Agile Applications 21 2.5 Related Work in Frequency Reconfigurable 22 Antenna and Filter 2.5.1 Two Port Frequency Reconfigurable 22 Antenna For Cognitive Radio 2.5.2 A Dual Port Wide-Narrowband 24 Antenna for Cognitive Radio 2.5.3 Implementation of UWB Antenna with 26 Bandpass Filter using Microstrip-toCPW 2.5.4 Electronically Switchable Dual-Band 29 Microstrip Interdigital Bandpass Filter for Multistandard Communication Application 3 METHODOLOGY 31 3.1 Introduction 31 3.2 Design Specifications 33 3.3 Considerations and Limitations 33 3.4 Materials and Components 34 3.5 Procedures 35 3.5.1 Simulation 35 3.5.2 Fabrication 35 ix 3.5.3 Measurement 4 37 ANTENNA AND BAND PASS FILTER 39 4.1 Introduction 39 4.2 Antenna Design 40 4.2.1 Glass-Shaped Printed Monopole 40 4.2.2 U-Shaped Printed Monopole 41 4.2.3 42 Shorted Circular Patch Printed Monopole with Steps 4.3 Antenna Performance and DIscussion 44 4.4 Filter Design 47 4.4.1 48 1.3GHz and 2GHz Interdigital Band Pass Filter 4.4.2 3GHz and 4GHz Interdigital Band 50 Pass Filter 4.4.3 5GHz and 6GHz Interdigital Band 51 Pass Filter 4.5 5 Interdigital Filters Results and Discussions ANTENNA INTEGRATED WITH BAND PASS 52 56 FILTER 5.1 Introduction 56 5.2 Antenna Integrated with Band Pass Filter 57 5.3 Antenna Integrated with Band Pass Filter 62 Results and Discussions 6 5.3.1 Return Loss Analysis 62 5.3.2 Radiation Pattern Analysis 68 5.3.3 Surface Current Plot 70 CONCLUSION AND RECOMMENDATIONS 73 6.1 Conclusion 73 6.2 Recommendation for future research 75 x REFERENCES Appendix A: 76 Diode Biasing Circuit 79 xi LIST OF TABLES TABLE NO. TITLE PAGE 2.1 Summary, advantages and room for improvement 24 2.2 Summary, advantages and room for improvement for 26 dual port dual antenna design 2.3 Summary, advantages and room for improvement for 28 antenna integrated with fixed BPF 2.4 Summary, advantages and room for improvement for 31 frequency reconfigurable interdigital band pass filter 4.1 Parameters for the 1.3GHz and 2GHz filter 49 4.2 Parameters for the 3GHz and 4GHz filter 51 4.3 Parameters for the 5GHz and 6GHz filters 52 5.1 Wavelengths at specific frequencies 58 5.2 List of activated switches for each frequency 61 5.3 Simulated gain of finalized structure 70 xii LIST OF FIGURES FIGURE NO. TITLE PAGE 2.1 Return loss versus frequency graph 9 2.2 E-Plane radiation pattern 10 2.3 H-Plane radiation pattern 10 2.4 3D plot of radiation pattern 11 2.5 Conventional shapes of patch antennas 12 2.6 Basic structure of monopole (a,b) and dipole (c) antenna 12 2.7 Parabolic dish antenna for satellite communication 12 2.8 A circular printed monopole with slots and steps. (a) 14 antenna structure (b) surface current distribution at 4GHz (c) surface current distribution at 6GHz (d) surface current distribution at 9GHz [12] 2.9 Types of filter 15 2.10 Low pass filter configurations. (a) T-Network (b) π- 16 Network 2.11 High pass filter configurations. (a) T-Network (b) π- 16 Network 2.12 General configuration of end-coupled microstrip 17 bandpass filter 2.13 General structure of parallel-coupled microstrip band 17 pass filter 2.14 General configuration of interdigital bandpass filter 18 2.15 A design of frequency retuneable square ring patch 20 antenna 2.16 Dual band reconfigurable CPW patch antenna with 20 MEMs 2.17 Antenna and filter design 23 xiii 2.18 Transmission loss with varying slot gap width 23 2.19 Narrow band return loss 23 2.20 Very wide band return loss 24 2.21 Dual port and dual antenna design 25 2.22 Return Loss of Dual port and Dual Antenna Design: a) 25 UWB Antenna, b) Narrow Band Antenna 2.23 Overall structure of antenna integrated with fixed BPF 27 2.24 Components of antenna integrated with fixed BPF: a) UWB antenna, b) BPF with band reject   27 2.25 Return loss of antenna integrated with fixed BPF: a) 28 UWB antenna, b) BPF with band reject, c) simulated and measured results for whole structure 2.26 “Near Frequency” reconfigurable interdigital BPF: a) 30 filter design, b) return loss while switch is “ON” and “OFF” state 2.27 “Far Frequency” reconfigurable interdigital BPF: a) 30 filter design, b) return loss while switch is “ON” and “OFF” state 3.1 Flow chart of the overall project activities part 1 32 3.2 Structure of FR4 Board 34 3.3 UV Mask using transparency 36 3.4 UV exposure device 36 3.5 Developing image on FR4 board 36 3.6 Removing unwanted part of copper layer 37 3.7 Agilent E5071C-2K5 2-port VNA 38 4.1 Glass-shaped printed monopole antenna 41 4.2 U-shaped printed monopole antenna 42 4.3 Shorted circular printed monopole antenna: a) front 44 side, b) back side 4.4 Simulated Return Loss (dB) versus frequency (GHz) for 45 Glass-Shaped, U-Shape and Shorted-Circular patch printed monopole 4.5 Simulated and measured Return Loss (dB) versus 46 xiv 4.6 frequency (GHz) for Shorted-Circular patch printed monopole Simulated radiation pattern 3D plot at 2GHz: a) Glass- 47 Shape Antenna, b) U-Shape Antenna, c) ShortedCircular Patch Antenna 4.7 1.3GHz and 2GHz frequency reconfigurable interdigital 49 filter design 4.8 1.3GHz and 2GHz frequency reconfigurable interdigital 50 filter parameters 4.9 3GHz and 4GHz frequency reconfigurable interdigital 51 filter design: a) 3GHz, b) 4GHz 4.10 Basic structure of interdigital filter for 5GHz and 6GHz 52 operation 4.11 Simulated and measured Return Loss (dB) versus 53 frequency (GHz) for Filter A with diode “On” 4.12 Simulated and measured Return Loss (dB) versus 53 frequency (GHz) for Filter A with diode “Off” 4.13 Simulated and measured Return Loss (dB) versus 55 frequency (GHz) for Filter B, Filter C and Filter D 5.1 Block diagram of final structure 57 5.2 Top layer of finalized structure with transmission line 59 dimensions 5.3 Top layer of integrated structure with switch numbering 60 5.4 Bottom layer of integrated structure 60 5.5 Integrated structure prototype: a) Top layer, b) Bottom 61 layer 5.6 Simulated Return Loss versus frequency for antenna 62 integrated with band pass filter 5.7 Measured Return Loss versus frequency for antenna 63 integrated with band pass filter 5.8 Simulated and measured return loss versus frequency of 64 finalized structure at 1.3GHz 5.9 Simulated and measured return loss versus frequency of finalized structure at 2.0GHz 64 xv 5.10 Simulated and measured return loss versus frequency of 65 finalized structure at 3.0GHz 5.11 Simulated and measured return loss versus frequency of 65 finalized structure at 4.0GHz 5.12 Simulated and measured return loss versus frequency of 66 finalized structure at 5.0GHz 5.13 Simulated and measured return loss versus frequency of 66 finalized structure at 6.0GHz 5.14 Simulated radiation pattern for finalized structure: a) 69 1.3GHz, b) 2.0GHz, c) 3.0GHz, d) 4.0GHz, e) 5.0GHz, f) 6.0GHz 5.15 Simulated surface current for integrated structure at 70 1.3GHz 5.16 Simulated surface current for integrated structure at 71 2GHz 5.17 Simulated surface current for integrated structure at 71 3GHz 5.18 Simulated surface current for integrated structure at 71 4GHz 5.19 Simulated surface current for integrated structure at 72 5GHz 5.20 Simulated surface current for integrated structure at 6GHz 72 xvi LIST OF SYMBOLS ε eff - Effective Dielectric Constant εr - Dielectric Constant h - Substrate Thickness W - Width L - Length fr - Resonant Frequency υ0 - Free-space Velocity of Light; 3 x 108 ΔL - Length extension λo - Wavelength fH - Higher Operating Frequency fL - Lower Operating Frequency a - Radius of sphere 𝜂𝑎 - Efficiency of ESA Rr - Radiation Resistance Rm - Material Loss Resistance ηs - efficiency of system ηm - efficiency of matching network Tx - Transmitter Rx - Receiver xvii LIST OF ABBREVIATIONS CR - Cognitive Radio SDR - Software Defined Radio GHz - Giga Hertz ISM - Industrial Scientific Medical GSM - Global System for Mobile Communications TV - Television FR4 - Flame Retardant 4 MHz - Mega Hertz RF - Radio Frequency BW - Bandwidth 3D - Three Dimensional CPW - Co-planar Waveguide SMA - SubMiniature version A IF - Interdigital Filter UWB - Ultra Wide Band dB - Decibel LPF - Low Pass Filter BPF - Band Pass Filter HPF - High Pass Filter BSF - Band Stop Filter CST - Computer Simulation Technology VNA - Vector Network Analyzer MEMs - Microelectromechanical Systems UMTS - Universal Mobile Telecommunications System LTE - Long Term Evolution xviii LIST OF APPENDIX APPENDIX A TITLE Diode Biasing Circuit PAGE 79 CHAPTER 1 INTRODUCTION Research background, problem statement, objective of the research, scopes of the project and thesis outline is presented in this chapter. 1.1 Background The emergence of reconfigurable antennas has enabled wireless communication industry to expand wireless technology and system complexity. Reconfigurability in frequency has enable multi operating frequency while antenna with beam steering capability able to focus the antenna coverage towards desired location. Cognitive Radio (CR) and Software Defined Radio (SDR) are two examples that uses multiple operating frequency [1-2]. The purpose of these technologies is to increase the utilization of the available frequency spectrum hence enabling the network to have larger capacity. Generally, the spectrum can be classified into two categories, the license and unlicensed band. The unlicensed band or the ISM band (Industrial, Science and 2 Medical) which is 2.4 GHz and 5.8 GHz are usually used by various short range wireless consumer products such as WiFi, Bluetooth, wireless mouse, keyboard and other wireless user interface [3]. The free ISM band suffers from high spectrum occupancy due to the number of users that would create interference even though various techniques such as frequency hopping and code division multiple access have been applied. On the other hand, the licensed band could only be use by the company that pays for the certain frequency range. Example of such band is the GSM band, TV band, armature radio band and Satellite bands [3]. These bands are not usually being utilized all time. In some cases, the bands would be used periodically and in some scenario, the band would be occupied only once a year in a small area. Currently, CR has gained attention from researchers around the world to develop the system as it is hoped to be the solution to spectrum insufficiency problem. There are no standards presently set for CR but some of the researchers are focusing on the TV band while others set their own operating frequency range [4]. In Malaysia, the Multimedia and Communication Commission (MCMC) has allocated 1GHz to 6GHz of the spectrum to applications such as mobile communication, satellite communication and ISM [3]. Some of these applications will not always use the frequency allocated for them or their coverage are small. It is suitable for unlicensed applications such as SDR and CR to temporary occupy the licensed band. Hence, the frequency range from 1GHz to 6GHz was chosen as the frequency range for this research. One of the most important components in a wireless system is the antenna. A good antenna ensures the coverage area specification is met as well as the signal power and quality. For frequency agile application, new types of antenna need to be designed since the concept of dynamic operating frequency in this system requires the antenna to operate at broad bandwidth for scanning process as well as narrow bandwidth for the data transfer process [5]. 3 In this research, a broadband antenna were designed from conventional circular patch antenna by implementing bandwidth enhancing techniques such as shorting pin, slot and steps. The designed broadband antenna will be integrated with filters to limit and control the operating frequency. A proof of concept was done by integrating the broadband antenna with a dual frequency band pass filter operating at 1.3GHz and 2GHz. RF diodes were used as switches to manipulate the filter stub length for narrow band operation. Another structure was also fabricated to incorporate four band pass filter for narrow band operation at 1.3GHz, 2GHz, 3GHz, 4GHz, 5GHz and 6GHz. Copper strips were used instead of RF diodes for the second structure. However, by integrating multiple filters to the antenna, the overall structure will be larger and the complexity in fabrication will also increase. 1.2 Problem Statement Spectrum is a scarce recourse in wireless communication world. Nowadays, most of the available spectrum has been assigned to specific applications, the only free band to be used by general consumer is the ISM bands. A lot of application such as Bluetooth and WiFi that operates in small coverage areas share the ISM bands. In some areas such as highly populated cities, the number of ISM band users is high which would cause interference between the users. This fact calls for a solution to avoid further disturbance in the wireless service as more users will use the services each coming day. Antennas need to be designed for each application so that it could deliver the signal to its best. Moreover, compact antenna is highly desirable in modern society where everything is preferred to be mobile, small and light weighted. For frequency agile applications, the antenna should not only meet the expectation of normal antennas, it should also be able to reconfigure its operating frequency on demand by the back end system. Additional requirement for CR system is the antenna should 4 also be able to operate at broad bandwidth so that it could detect “holes” in the spectrum. The antenna and system development of Cognitive Radio (CR) are still in early stage. Some prototype antenna designs published in papers, conferences and journals can be use as reference in designing future antennas for CR. 1.3 Objective • To design a frequency reconfigurable antenna for frequency agile applications. • To design band pass filters to be integrated with a broadband antenna that will limit and determine the operating frequency of the antenna. • To analyze the performance of the structure designed in terms of bandwidth, operating frequency, return loss and gain. 1.4 Scopes of Work This research involves four scope of work, which begins with literature review, followed by structure design process, fabrication and measurement. 5 1.4.1 Literature Review Some reviews from previous works that have been done on the design of reconfigurable antenna specifically for CR. 1.4.2 Structure Design, Modification, Simulation and Optimization Several structures of antenna integrated with filters were designed which are reconfigurable, compact and suitable for frequency agile application. The structure of the antennas will be planar on the FR4 dielectric substrate. The design will include an antenna simulations and optimizations using CST Design Studio. 1.4.3 Antenna Fabrication The designed and simulated antennas were fabricated on the dielectric material (FR4 substrate). Implementation of RF diodes and SMA connectors will be conducted in this stage. 6 1.4.4 Structure Testing and Measurement The fabricated structures were measured at different frequencies ranging from 1GHz to 6GHz. The return loss of the reconfigurable antenna will be measured at all possible configuration. The measured and simulated results will be compared for further optimization purpose until a finalized design is obtained. 1.5 Thesis Outline The thesis consists of seven chapters starting with introduction which explains the background, problem statement, scope of work and objectives of this research. In Chapter 2, fundamental theories on antenna and filter design are explained as well as review on previous researches that are related to this research. The methodology, considerations and limitations involved in this research are discussed in Chapter 3. Chapter 4 explains the design of the antenna and filter prototypes in detail which includes all measurements and functions. Results obtained from simulation and measurement for antenna and filter designed are also analyzed this chapter. Chapter 5 explains about the design of integrated structure. The simulated and measured results of the integrated structure are discussed as well as comparison on performance between stand alone structure and integrated structure. Discussions are focused on return loss as this affects the operating frequency. Conclusion of the research and recommendations on future research are stated in Chapter 6. 76 REFERENCES 1. K. Hiraga, K. Akabane, H. Shiba and K. 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