• 한국전기전자재료학회논문지
• /
• 제14권1호
• /
• pp.74-83
• /
• 2001

In this study, the optimum structure of a magnetic thin film inductor was designed for application of DC-DC converters. The Ni$\sub$81/Fe$\sub$19/ (at%) alloy was selected as a high-frequency($\geq$MHz) magnetic thin film magnetron sputtering system. As-deposited NiFe thin films show similar magnetic properties compared to bulk NiFe alloys, indicating that they have a good film quality. The optimum design of dolenoid-type magnetic thin film inductors was performed utilizing a Maxwell computer simulator (Ansoftt HFSS V7.0 for PC) and parameters obtained from the magnetic properties of magnetic core materials selected. The high-frequency characteristics of the inductance(L) and quality factor(Q) obtained for the designed inductors through simulation agreed well with those obtained by theoretical calculations, confirming that the simulated result is realistic. The optimum structure of high-performance (Q$\geq$60, L = 1${\mu}$H, efficiency $\geq$90%), high-frequency ($\geq$5MHz), and solenoid-type magnetic thin film inductors was designed successfully.

• Progress in Superconductivity
• /
• 제3권2호
• /
• pp.178-182
• /
• 2002

Superconducting four-element patch array antenna was designed and fabricated using $high-T_{c}$ superconducting (HTS) thin film. The array antenna has single-feed circularly polarization and a resonance frequency of 11.85 GHz fur satellite communication system. To fabricate this antenna $YBa_2$$Cu_3$$O_{7-x}$(YBCO) superconducting thin films were deposited using rf-magnetron sputtering technique. Sequential rotation technique based on radiation elements($0^{\circ}$ , $90^{\circ}$, 1$80^{\circ}$, $270^{\circ}$ phase delay) was utilized to achieve circularly polarization. Simulated and measured results, the analysis on resonant frequency(fr), return loss, and bandwidth are presented. The results show that 10 dB return loss bandwidth of the array antenna is 11.04 GHz~12.59 GHz (13.15%) and 3dB axial ratio bandwidth is 11.42~12.52 GHz (9.2%).).).

• 한국전기전자재료학회논문지
• /
• 제14권5호
• /
• pp.435-443
• /
• 2001

As power durable RF SAW filters, AL-(0∼2wt%)Cu alloy multi-layered thin electrodes were deposited on 42° LiTaO$_3$ piezoelectric substrates by magnetron sputtering process, and then ladder-type RF SAW filters, satisfying the electrical specification of CDMA transmission band, were fabricated through optimizing SAW resonator structures. The temperature of film electrodes in SAW filter was increased with RF power, and reached the maxima to cause a failure of SAW filters at the cut-off frequencies of the RF filter band. As RF power increases, the electrodes of Al-Cu alloy showed higher power durability than that of pure Al. The multi-layer laminated film of Al-1wt.% Cu/Cu/Al-1wt%Cu resulted in the best power durability up to 4W of RF power. Every film electrode, however, was destroyed within seconds whenever applying a critical RF power to SAW filters, regardless of the composition and structure of film electrodes. The breakdown of film electrodes under FR power seems to believe due to the fatigue of electrodes caused by repetitive cyclic stress of surface acoustic wave, which is amplified as RF power increases.

• 한국자기학회지
• /
• 제8권6호
• /
• pp.357-361
• /
• 1998

직류 및 고주파 마그네트론 스파터링 방법으로 제조한 CoZr/Ag/CoCr 삼층박막에 대해, 강자성 공명 실험을 수행하므로서 비자성층인 Ag 층의 두께변화가 CoZr층과 CoCr층 사이의 교환결합(Exchabge coupling)에 미치는 영향을 고찰했다. CoZr/Ag/CoCr 삼층박막에서 층간 결합세기(Coupling strength) K'은 Ag층의 두께가 증가함에 따라 급격히 증가하여 Ag 층의 두게가 10$\AA$일 때, 최대값 748 Oe을 보였다. Ag 층의 두께가 20~100$\AA$인 영역에서 K'은 진동하는 모습을 보이는데, 이와 같은 특성은 80Ni-Fe/Cu/Co 다층박막에 대해 H.Koizumi 등이 관측한 결과와 유사한 모습으로서, 스원인규명을 위해 지속적인 연구가 요망된다고 생각한다. 그리고, Ag층의 두께가 100$\AA$ 이상 증가하면 층간 상호작용은 0으로 수렴하는 모습이 보인다. 모든 시료에 대해 K'은 0보다 큰 특성을 보이므로, CoZr층과 CoCr층 사이의 상호작용은 강자성 결합으로 해석된다.