[[alternative]]Design of a Novel Artificial Magnetic Conductor

碩士電信工程研究所[[abstract]]本論文提出一種新型人造磁導體，其工作原理是利用螺旋元件的電感性電抗與金屬盒的電容性電抗組成一LC並聯共振電路，因此位於共振頻率時會產生磁牆的特性。且因螺旋元件在金屬盒形成週期性排列，所以在特定頻帶內也具有電磁能隙效果。 在本研究中首先利用一個由平面波正向入射、完美匹配層與週期性邊界條件組成的數值分析模型，計算無窮大人造磁導體的反射相位正負45度以下對應之有效頻帶。再藉由半波長偶極天線置於人造磁導體與磁牆上方的模擬與量測之輻射場型比對，最後可驗證新型人造磁導體在位於正向入射平面波反射相位正負45度以下對應之有效頻帶內確實能夠產生磁牆的特性，可維持磁牆特性的有效頻寬約800MHz。且天線的增益也因磁牆特性影響而獲得大幅的提升，提升前之天線增益只有1.97dBi，提升後之天線增益可達4.98dBi~7.3dBi。 此外，本研究也利用懸浮微帶線法觀察新型人造磁導體的電磁能隙特性，最後量測出的其中一個能隙頻帶為2.765GHz~2.934GHz。[[abstract]]In this thesis, we propose a novel artificial magnetic conductor(AMC) structure using wire helix in a metal box. This structure is equivalent to a parallel resonant LC circuit resulting in some kinds of characteristics like the perfect magnetic conductor(PMC) at resonance frequency. Due to the periodic arrangement of this structure, the electromagnetic band-gap(EBG) effect will appear in this specific band. First, we calculate the effective AMC bandwidth with reflection phase between 45 degrees for AMC with infinite elements case by a numerical analysis model. Simulated radiation patterns for half-wavelength dipole antenna on the AMC is compared with those of the same half-wavelength dipole antenna on the PMC. Our proposed AMC structure is verified to have the characteristics of PMC from 1.95 GHz to 2.75 GHz. We also study the characteristics of EBG of this AMC structure by suspended microstrip method. One of the measured EBG band is from 2.765 GHz to 2.934 GHz