• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.35-39
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• 2006

In this study, in order to develop the multilayer piezoelectric actuator and ultrasonic resonator, PMN-PNN-PZT ceramics were fabricated by sintering with $Li_2CO_3-Na_2CO_3$ as sintering aids at $950^{\circ}C$ and their piezoelectric and dielectric characteristics were investigated as a function of PNN substitution. With increasing PNN substitution, dielectric constant(${\epsilon}_r$), electromechanical coupling factor(kp), and piezoelectric d constant($d_{33}$) were increased to $12 mol\%$ PNN substitution and then showed a tendency to decrease rapidly With increasing PNN substitution, crystal structure changed from tetragonal to rhombohedral at $12 mol\%$ PNN substitution and then secondary phase was appeared and its intensity was increased. At the $12 mol\%$ PNN substituted PMN-PZT composition ceramic sintered at $950^{\circ}C$, density, kp, $d_{33}$ and Qm showed the optimum value of $7.79 g/cm^3$, 0.599, 419 pC/N, and 894, respectively for multilayer piezoelectric actuator application.

• 전기학회논문지
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• 제57권7호
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• pp.1213-1217
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• 2008

Poling is an important process in fabricating PZT ceramic devices such as filters and resonators and activates piezoelectricity to sintered PZT ceramics. Tolerance of the operating frequency of these devices is tightly required in applications. And a factor to attribute the tolerance is the temperature dependence of the resonance frequency of PZT ceramics. In this paper the relationship of poling strength and temperature dependence of resonance frequency of PZT specimens was studied. The $Pb(Zr_{0.53}Ti_{0.47})O_3$ ceramics were fabricated and the poling strengths were chosen to be 0.5, 1.5, 2.5 and 3.5 [kV/mm]. The dielectric constant of the specimen poled in poling strength 0.5 [kV/mm] was less than that of unpoled specimen and the specimen poled in higher electric field had the higher dielectric constant. (002) peak in X-ray diffraction patterns of the specimens increased as poling strength increased. And the change of resonance frequency of the specimens according to the variation of temperature was measured. Resonance frequency of all specimens increased as the temperature increased. The specimen poled in higher electric field had the smaller positive temperature coefficient of resonance frequency. The effect that temperature coefficient of resonance frequency becomes smaller is obtained when Zr mole in PZT composition equation increase. Controlling the poling strength is believed to be a method to adjust the temperature stability of resonance frequency of the PZT ceramic devices.

• 한국세라믹학회지
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• 제40권3호
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• pp.268-272
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• 2003

직류 마그네트론 스퍼터링법을 이용하여 증착압력과 기판온도변화에 따른 텅스텐 박막의 미세구조 변화에 대하여 연구하였다. 기판온도 40$0^{\circ}C$에서 증착 압력의 감소에 따라 텅스텐 박막의 미세구조가 zone I에서 zone T로 변화하였다. 텅스텐 박막의 미세구조 비저항과 결정배향성은 상관관계를 보였으며. 미세구조가 zone T 영역에서 낮은 비저항(10$\times$$10^{-6}$ $\Omega$-cm) 과 99%의 (110)면 우선 배향성을 나타내었다. zone T 영역에 해당하는 미세구조를 지니는 텅스텐 박막을 이용한 박막형 공진기는 텅스텐 박막의 높은 탄성저항과 매끈한 표면으로 인해 494의 $Q_{s}$와 5.50%의 $K_{eff}$$^{2}$ 값의 우수한 공진특성을 보였다....

• Journal of electromagnetic engineering and science
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• 제10권1호
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• pp.28-34
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• 2010

This paper introduces a new U.S. ultra-wideband(UWB: 3.1~10.6 GHz) 1:2 power divider based on a single section Wilkinson type configuration. The divider provides very flat in-band power splitting, high isolation, low insertion loss, sharp roll-off bandpass filtering, and DC blocking characteristics. The circuit consists of a $\lambda$/4 Y resonator, three capacitively coupled $\lambda$/2 short-circuited lines, and a resistor between the two output ports. The circuit structure was simulated with ADS and HFSS, and realized with low-temperature co-fired ceramic(LTCC) green tape, which has a dielectric constant of 7.8. $|S_{11}|$ better than 10 dB, $|S_{21}|$ and $|S_{31}|$ less than 3.2 dB, with both $|S_{22}|$ and $|S_{32}|$ measured as better than 12 dB for the whole UWB band. Measurement results agree closely with HFSS simulation results. The power divider has a compact size of $4\times9\times0.6mm^3$.

• 수산해양기술연구
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• 제35권3호
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• pp.312-322
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• 1999

A ultrasonic transduce with a single acoustic matching layer has been designed as an attempt to increase the bandwidth of underwater transducer. The wideband resonance condition was accomplished by attaching a single matching layer on the front face of a ceramic resonator composed of a piezoelectric bar, a taper part and a head part. A modified Mason's model was used for the performance analysis and the design of transducers, and the constructed transducers were tested experimentally and numerically by changing the impedance and thickness of the matching layer in the water tank.The obtained results are summarized as follows:1. Measured resonant and antiresonant frequencies of the piezoelectric transducer with no matching layer in air were 24.7 kHz and 25.6 kHz, respectively. 2. Two resonant frequencies of the piezoelectric transducer with a single matching layer were 21.7 kHx and 26.9 kHz, respectively, in air and 21.4 kHz and 22.7 kHz, respectively, with a water load.3. Two distinct resonance peaks in the transmitting voltage response(TVR) of the developed transducer were observed at 22.0 kHz and 25.8 kHz, respectively, with center frequency of 24.0 kHz. The values of TVR at these frequencies were 130.1 dB re $1 \muPa$/V at 22.0 kHz and 128.5 dB re $1 \muPa$/V at 25.8 kHz, respectively.Reasonable agreement between the experimental results and the numerical values was achieved.

• 마이크로전자및패키징학회지
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• 제8권1호
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• pp.61-64
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• 2001

VCO(Voltage Controlled Oscillator)는 통신용 단말기의 크기, 성능 및 전력 소비를 결정하는 중요한 부품중의 하나이다. 통신용 기기의 크기가 점점 작아지고 있는 추세이기 때문에 VCO도 특성의 저하없이 점점 소형화 되고 있다. VCO 모듈을 개발하기에 앞서 회로에 사용되는 수동소자(L,C,R)들에 대한 연구가 진행되었다. 이 과정에서 작은 면적을 차지하면서도 동일한 특성을 나타낼 수 있는 패턴을 고안하였고 이를 적용하였다. 자체 개발된 수동소자 library를 가지고 2차원 simulation을 시행하였고 이를 바탕으로 3차원 회로를 구성하였다. 3차원 회로 구성시 VCO 전체 특성에 크게 영향을 주는 소자들은 trimming이 가능하도록 surface 쪽으로 배치하였다. 공진기 부분에서는 저손실의 stripline 구조를 적용하여 높은 Q값을 얻을 수 있었다. 이러한 과정을 통해 2.3~2.36 GHz에서 동작하는 적층형 VCO를 개발하였다.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.253-269
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• 1999

The development of telecommunication and information technology requires to develop new piezoelectric materials with small size, low impedance, wide pass band width and high thermal stability of frequency. Langasite (La3Ga5SiO14) single crystal has been researched substitute of quartz and LiNbO3 for the applications of SAW filter, BAW filter and resonator. Its single crystal growth has been carried out by Czochralski Method. So, in order to get single crystal with higher quality, in this study, lnagasite (La3Ga5SiO14) single crystal was grown by using Floating Zone (FZ) method and characterized. For the growth of langasite single crystals, the langasite powder was synthesized at 135$0^{\circ}C$ for 5hrs and the feed rod was sintered at 135$0^{\circ}C$ for 5hrs. The growing rate was 1.5mm/h and the rotation speed was 15 rpm for an upper rotation and 13 rpm for a lower rotation. In order to prevent the evaporation of gallium oxide, Ar and O2 gas mixture was flowed. The growth direction was analyzed by Laue back-scattered analysis. The composition of grown crystal was analyzed suing XRD and WDS. The electrical properties of grown crystal at various frequencies and temperature were discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1453-1455
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• 1998

$Ba(Mg,Ta)O_3-Ba(Co,Nb)O_3$ ceramics were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of 1500-$1575^{\circ}C$ for 5[hr.] in air. The crystal structure was investigated by the XRD. The microstructure of the ceramics were observed by SEM. The microwave properties of dielectric resonators were investigated as a function of composition and sintering temperature. $Ba(Mg,Ta)O_3-Ba(Co,Nb)O_3$ ceramics have a structure of complex perovskite type, and have peaks of (101),(102),(201),(202) and (212). In the case of the $0.7Ba(Mg,Ta)O_3-0.3Ba(Co,Nb)O_3$ ceramic resonator, dielectric constant, quality factor and temperature coefficient of resonant frequency(TCRF, ${\tau}_l$) were a good value of 26.5, 11.500 at 10[GHz] and -1.3[ppm/$^{\circ}C$] from $25^{\circ}C$ to $60^{\circ}C$, respectively.

• 마이크로전자및패키징학회지
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• 제11권1호
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• pp.71-76
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• 2004

무선 이동 통신에 응용할 수 있는 소형의 집적된 형태의 여파기를 LTCC기술과 인터디지털 커패시터 (Interdigital capacitor)를 가진 컴라인 타입(Combline type)의 구조를 이용해 구현했다. 또한 T 패턴을 가지는 마이크로스트립(Microstrip)타입의 공진기를 이용해 LTCC 기판의 전기적 성능을 측정했다. 구현된 여파기는 인터디지털과 컴라인 구조를 이용해 2.7mm${\times}$2.03mm의 비교적 소형으로 구현할 수 있었고 5.09 GHz의 중심주파수에서 1.8 dB의 삽입손실, 37.6 dB의 반사손실, 그리고 280 MHz의 대역폭을 가졌다. 제안된 여파기는 작은 크기와 간단한 구조로 인해 여러 가지 LTCC기판의 집적형 여파기로 응용될 수 있을 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.15-17
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• 2005

In this study, tunable dielectric materials are important for resonator, variable capacitor, phased array antenna and other devices application. In this paper, Dielectric constant increased and tuning range increased with the increased of $BaSrTiO_3/Li_{2}CO_{3}$ content, which probably can be explained by the substitution of Ba3+, Li1+ on BaTiO3 lattice. The tunability and dielectric loss of the $BaSrTiO_2/Li_{2}CO_{3}$ thick film, sintered at $1150^{\circ}C$, were about 43 % and 0.234 at 10$\sim$15 MHz, respectively. In case of BaSrTi/MgO, Dielectric constant decreased and tenability increased with the added of $BaSrTiO_3/MgO$. The ferroelectrics properties were distinct when adding Li to BST ceramic thick film, and paraelectrics pattern was distinct when adding Mg.