A Design of Dual-Band Pass Filter for IEEE 802.11 a/b/g Wireless LAN

최근에 dual-band 필터는 초고주파수에서 무선 통신 제품을 위해 중요한 소자가 되고 있다. IEEE 802.11b와 IEEE 802.11g 무선 랜 제품들은 주파수 면허를 받을 필요가 없는 Industrial-Scientific-Medical(ISM) 2.4- GHz 대에서 이용한다. 특히 IEEE 802.11a 무선 랜 제품은 ISM 5- GHz 대를 사용한다. 따라서 더욱 효과적인 RF 장치를 설계하는데 dual-band filter, 안테나, 증폭기와 같은 dual-band RF 소자들은 필수적이고, 그것은 이동통신의 발전에 중요하다. 이 논문은 BPF와 BSF가 직렬로 구성되어있는 dual-band 통과필터 구조를 보여준다. 본 논문에서는 BSF는 serial-shunted 구조를 사용하여 실현하고 광 대역 BPF는 3단 링 공진기를 사용해서 만들었다. 두 회로는 마이크로 스트립 전송 선로를 기본으로 한다. 특히, dual-band 필터의 각 통과대역의 대역폭과 동작주파수는 광 대역 BPF와 BSF의 특성 임피던스를 조정함으로써 제어할 수 있다. 광 대역 BPF의 파라미터는 최적 값을 계산할 수 있는 막강한 방법인 Powell's 최소 자승법을 사용해서 구할 수 있다. 그리고, band stop filter의 파라미터는 고전적인 Chebyshev 저역통과 프로토타입으로부터 얻을 수 있다. 본 논문에서 제안한 방법으로 dual-band pass filter를 만들고 측정하였다. 측정 결과는 시뮬레이션 결과와 거의 일치했다. 그래서 이 논문에서 dual-band pass filter 설계에 대한 새로운 가능성을 제안한다.In recent years, dual-band filters have become important components for wireless communication products at microwave frequencies. IEEE 802.11b and IEEE 802.11g wireless local area networks (WLAN) products operate in the unlicensed industrial-scientific-medical (ISM) 2.4- GHz band. In particular, IEEE 802.11a products implement in the ISM 5- GHz band. Therefore, dual-band RF components such as dual-band filters, antenna, and amplifier are essential for the development of mobile communications to design more effective RF devices. This thesis presents a dual-band pass filter structure which consists of a wide-band pass filter and a band stop filter in a cascade connection. This method has been already proposed in some published paper. In this thesis, the band stop filter is implemented by using a serial-shunted structure, while the wide-band pass filter is constructed by employing three cascade ring resonators. Both two circuits are based on microstrip transmission line structure. In particular, the bandwidth of each pass band of the dual-band filter and the center frequency of the operation band are controllable by adjusting the characteristic impedance of both the wide-band pass filter and the band stop filter. The parameters of the wide-band pass filter are extracted by using Powell's least square method [14] which is a powerful method for calculating the optimum values, and the parameters of the band stop filter are obtained from the Chebyshev low pass prototype. A dual-band pass filter designed by the method proposed in this thesis has been fabricated and measured. The results agree well with the simulation results. Therefore, it was confirmed that the proposed design method of a dual-band filter for IEEE 802.11a/b/g is available.Contents i Nomenclature iii List of Tables iv List of Fig.s iv Abstract vi 요 약 viii CHAPTER 1 Introduction 1 1.1 Background and Purpose 2 1.2 Research Contents 2 CHAPTER 2 Wide-band Pass Filter 4 2.1 Introduction 4 2.2 Theoretical Analysis 6 2.2.1 Even-mode Analysis 7 2.2.2 Odd-mode Analysis 9 2.2.3 S-parameter Extraction from Even-odd Mode. 10 2.2.4 Analysis of 3-Stage Ring Resonators Circuit. 10 2.3 A design of 2.35-5.05 GHz Band Pass Filter. 11 2.4 Simulation Results. 14 CHAPTER 3 Band Stop Filter 17 3.1 Introduction 17 3.2 Theoretical Analysis 19 3.2.1 Theory Background 19 3.2.2 Optimum Formulas 23 3.3 A design of 2.45~4.95 GHz Band Stop Filter 24 3.4 Simulation. 26 CHAPTER 4 Dual-Band Pass Filter 29 4.1 Theoretical Analysis 29 4.2 A design of the Dual-Band Pass Filter and Simulation Results 32 4.3 Fabrication and Measurement. 35 CHAPTER 5 Conclusions 39 References 40 Appendix 42 Acknowledgements 4