• Title/Summary/Keyword: RF phase

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Fatigue Properties of $SrBi_{2}Ta_{2}O_{9}$ Thin Film by RF Sputtering Method (RF Sputtering법에 의한 $SrBi_{2}Ta_{2}O_{9}$ 박막의 피로특성)

  • 오열기;조춘남;정일형;김진사;신철기;최운식;김충혁;이준웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.897-900
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    • 2000
  • Annealing dependencies of the fatigue properties of SrBi$_2$Ta$_2$$O_{9}$ thin films were observed as function of substrate temperature(400-50$0^{\circ}C$) by the rf magnetron sputtering method. With increasing annealing temperature from $600^{\circ}C$ to 85$0^{\circ}C$, flourite phase was crystalized to $650^{\circ}C$ and Bi-layered perovskite phase was crystalized above $700^{\circ}C$. The fatigue characteristics of SBT thin films deposited on Pt/TiO$_2$/SiO$_2$/Si substrate did not change up to 101o switching cycles.s.

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Quadrature VCO as a Subharmonic Mixer

  • Oh, Nam-Jin
    • International journal of advanced smart convergence
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    • v.10 no.3
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    • pp.81-88
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    • 2021
  • This paper proposes two types of subharmonic RF receiver front-end (called LMV) where, in a single stage, quadrature voltage-controlled oscillator (QVCO) is stacked on top of a low noise amplifier. Since the QVCO itself plays the role of the single-balanced subharmonic mixer with the dc current reuse technique by stacking, the proposed topology can remove the RF mixer component in the RF front-end and thus reduce the chip size and the power consumption. Another advantage of the proposed topologies is that many challenges of the direct conversion receiver can be easily evaded with the subharmonic mixing in the QVCO itself. The intermediate frequency signal can be directly extracted at the center taps of the two inductors of the QVCO. Using a 65 nm complementary metal oxide semiconductor (CMOS) technology, the proposed subharmonic RF front-ends are designed. Oscillating at around 2.4 GHz band, the proposed subharmonic LMVs are compared in terms of phase noise, voltage conversion gain and double sideband noise figure. The subharmonic LMVs consume about 330 ㎼ dc power from a 1-V supply.

RF Compatibility Test using RF Suitcase (이동형 RF 시험장비를 이용한 RF 호환성 시험)

  • Kim, Eung-Hyeon;Jeong, Dae-Won;Kim, Hui-Seop;Im, Jeong-Heum;Lee, Sang-Jeong
    • Journal of Satellite, Information and Communications
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    • v.1 no.2
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    • pp.45-50
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    • 2006
  • A satellite and ground stations which are developed in a program are tested whether the interface between the satellite and ground is well established before satellite operations. These compatibility tests are performed when the satellite is connected with the ground stations after all satellite and ground stations requirements are verified. The content of the RF compatibility test is to check whether the interface requirements which are described on the Interface Control Document are well developed. During the early operation phase and tentative contingency operations of the satellite, KARI ground station uses other oversea ground stations which are located worldwide according to contract between the KARI and the contractor. Since oversea ground stations were not developed for the designated space program, system integrator should check whether the oversea ground stations are satisfied with interface requirements. Using the RF suitcase, RF interface and the content of RF communication can directly be verified during RF compatibility test on oversea ground station without KARI ground station's support. The RF compatibility test using RF suitcase was performed oversea ground stations as well as KARI ground station located on Korea. The content of RF compatibility test was standardized in order to be used at any oversea ground stations, especially fitted for the operations concept of launch and early operations phase. The test content would be RF characteristics, protocol, command loop test, telemetry loop test, and ground station interface test.

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Preparation of Sr2FeMoO6 Thin Films by RF Magnetron Sputtering and Their Electrical Conduction Properties (RF 스퍼터법을 이용한 Sr2FeMoO6 박막 제조 및 전기전도 특성)

  • Ryu, Hee-Uk;Sun, Ho-Jung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.12
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    • pp.966-972
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    • 2010
  • Single-phase $Sr_2FeMoO_6$ thin films were produced by RF magnetron sputtering for use as electrodes in integrated sensors and found to be good conductors at room temperature. The films were deposited from a powder-type sputtering target under various conditions, and were crystallized by annealing. Elimination of $O_2$ gas during deposition, by the use of a solely Ar sputtering gas under a working pressure as low as possible, and vacuum annealing were important to promote the $Sr_2FeMoO_6$ phase. However, oxygen exclusion from sputtering and annealing was not enough to yield single-phase $Sr_2FeMoO_6$: hydrogen annealing was also required. Film production was optimized by varying the deposition parameters and hydrogen annealing conditions. The film had good electrical conduction, with a low resistivity of $1.6{\times}10^{-2}\Omega{\cdot}cm$ at room temperature.

The Thermoelectric Properties of Fe-Si Alloys Prepared by RF Induction Furnace (고주파 진공유도로로 제작한 Fe-Si계 합금의 열전변환특성)

  • 박형진;배철훈
    • Journal of the Korean Ceramic Society
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    • v.37 no.7
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    • pp.632-637
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    • 2000
  • Thermoelectric conversion properties of commercial Fe-Si2 and Fe-Si alloy ingots prepared by RF inductive furnace were investigated. As sintering temperature increased, density of the specimen increased and the phase transformation from metallic phases ($\varepsilon$-FeSi, ${\alpha}$-Fe2Si5) to semiconducting phase (${\beta}$-FeSi2) occurred more effectively. The FeSi phase was detected even after 100hrs of annealing treatment. For the Fesi1.95∼FeSi2.05 specimens prepared by RF inductive furnace, the thermoelectric property improved as the composition of the specimen approached to stoichiometric composition FeSi2. Electrical conductivity of the specimen increased with increasing temperatures showing typical semiconducting behavior. From the electrical conductivity measurements, activation energy in the intrinsic region (above about 700 K) was calculated to be approximately 0.46 eV. In spite of non-doping, the Seebeck coefficient for every specimen exhibited p-type conduction due to Si deficiency. Its maximum value was located at about 475 K, and then decreased abruptly with increasing temperatures. The power factor was governed by the Seebeck coefficient of the specimen more significantly than by electrical conductivity.

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Estimation of I/Q Imbalance Parameters for Repeater using Direct Conversion RF with Low Pass Filter Mismatch (저역 통과 필터 불일치를 포함한 직접 변환 RF 중계기의 I/Q 불균형 파라미터 추정)

  • Yun, Seonhui;Lee, Kyuyong;Ahn, Jaemin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.2
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    • pp.18-26
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    • 2015
  • In this paper, we studied the method for analyzing and estimating the parameters that induce I/Q imbalance in the repeater using direct conversion RF. In repeater, amplitude, phase, and filter mismatch are generated in the receiving-end which converts RF signal to baseband signal. And amplitude and phase mismatch are generated in the transmitting-end which converts baseband signal to RF signal. Accordingly, we modeled the parameters that cause I/Q imbalance in the structure of the repeater in order, and proposed a feedback test structure from the transmitting-end to the receiving-end for estimating the corresponding parameters. By comparing the test transmitting signal and received signal, it is possible to estimate the I/Q imbalance parameters which occurred from mixed components of real and imaginary part. And it was confirmed that I/Q imbalance phenomenon has been properly compensated with estimated parameters at the direct conversion RF repeater.

RF Compatibility Design & Verification for the SAR Satellite (SAR 위성의 고주파 호환성 설계 및 검증)

  • Won, Young-Jin;Park, Hong-Won;Moon, Hong-Youl;Woo, Sung-Hyun;Kim, Jin-Hee
    • Aerospace Engineering and Technology
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    • v.10 no.2
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    • pp.37-48
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    • 2011
  • Synthetic Aperture Radar(SAR) is a powerful and well established microwave remote sensing technique which enables high resolution measurement of Earth surface independent of weather conditions and sunlight illumination. KARI has been developing the first Korea SAR satellite which is scheduled to be launched in this year. The SAR satellite mainly consists of the bus platform and SAR payload. Most of all, the RF compatible design during the design phase and the verification of the RF compatibility during the testing phase is very important procedure for the in-orbit performance guarantee because the SAR payload radiates high power through the SAR antenna. In this study, the SAR satellite design criteria and verification procedure for the RF compatibility are described. In addition, this paper describes the RF full radiation testing (RF auto-compatibility testing) for the verification of the RF performance robustness, the testing configuration, and the test results.

RF Shimming Considering Coupling Effects for High-Field MRI

  • Heo, Hye-Young;Cho, Min-Hyoung;Lee, Soo-Yeol
    • Journal of Biomedical Engineering Research
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    • v.29 no.4
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    • pp.267-271
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    • 2008
  • The RF shimming technique has been used to improve the transmit RF field homogeneity in highfield MRI. In the RF shimming technique, the amplitude and phase of the driving currents in each coil element are optimized to get homogenous flip angle or uniform image intensity. The inductive and capacitive coupling between the coil elements may degrade the RF field homogeneity if not taken into account in the optimization procedure. In this paper, we have analyzed the coupling effects on the RF shimming using a sixteen-element TEM RF coil model operating at 300 MHz. We have found that the coupling effects on the RF shimming can be reduced by putting high dielectric material between the active rung and the shield.

Study of RF Impairments in Wideband Chirp Signal Generator (광대역 첩 신호 발생기를 위한 RF 불균형 연구)

  • Ryu, Sang-Burm;Kim, Joong-Pyo;Yang, Jeong-Hwan;Won, Young-Jin;Lee, Sang-Kon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.12
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    • pp.1205-1214
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    • 2013
  • Recently spaceborne SAR systems are increasing image resolution and frequency. As a high quality image resolution, the wider bandwidth is required and a wideband signal generator with RF component is very complicated and RF impairments of device is increased. Therefore, it is very important to improve performance by reducing these errors. In this study, the transmission signal of the wideband signal generator is applied to the phase noise, IQ imbalance, ripple gain, nonlinear model of high power amplifier. And we define possible structures of wideband signal generator and measure the PSLR and ISLR for the performance assesment. Also, we extract error of the amplitude and phase from the waveform and use a quadratic polynomial curve fitting and examine the performance change due to nonlinear device. Finally, we apply a high power amplifier predistortion method for non-linear error compensation. And we confirm that distortion in the output of the amplifier by intermodulation component is decreased by 15 dB.

The synthesis of high purity micro Ag particle using the rapid firing -liquid phase precursor method (RF-LPP법을 이용한 고순도 마이크로 Ag 입자 합성)

  • Lim, Byeong-Seok;Song, Young-Hyun;Lee, Min-Ji;Mang, Sung-Ryul;Yoon, Dae-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.25 no.3
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    • pp.93-97
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    • 2015
  • To synthesis of high purity micro silver particle, we extracted the silver from the waste by liquid-liquid extraction and used the rapid firing-liquid phase precursor (RF-LPP) method. The silver micro particle was synthesized at $500^{\circ}C$ for 3 hr in air atmosphere by RF-LPP method. As a result of the research, micro silver particle is measured X-ray diffraction (XRD), the main peak is nearly corresponded to the same as JCPDS card (No.87-0719). With using the RF-LPP method, the fine Ag micro particle indicated due to the control of nucleation site and the oxygen contents was decreased by reducing treatment. We expect this research contribute to advance in field of the recycling technology.