• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.166-166
• /
• 2009

에너지 하베스팅 소자용 압전 적층체를 제작하고 이에 대한 성능을 조사하였다. 최근 대부분 소형 소자들을 구동하는데 있어서 이에 필요한 소비 전력은 최소한 10~20 mW 이다. 이에 적합한 mm 크기의 압전 소자를 제작하고 외부 금속 기구물을 연결한 하베스팅 소자를 제작하였다. 이러한 소자의 공진 주파수를 120 Hz로 정하고 이에 적합한 무게추를 설정하였다. 120 Hz에서 1 g 가속도로 외부에서 진동을 가했을 때, 소자는 5 V, 20 mW의 전력을 발생하였다. 또한 이러한 소자에서 발생된 전력을 저장하기 위하여 간단한 정류 및 저장 장치를 제작하였다. 회로 제작시 압전 소자의 임피던스가 매우 적으므로 이에 적합하게 임피던스 매칭을 고려한 저 임피던스 회로를 제작하였으며, 이 회로는 약 80%의 효율을 나타내었다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.37 no.1
• /
• pp.37-43
• /
• 2017

Ultrasonic transducers with high resolution and resonant frequency are required to detect small defects (less than hundreds of ${\mu}m$) by ultrasonic testing. The resonance frequency and resolution of an ultrasonic transducer are closely related to the thickness of piezo-electric materials, backing materials, and the electric impedance matching technique. Among these factors, electrical impedance matching plays an important role because it can reduce the loss and reflection of ultrasonic energy differences in electrical impedance between an ultrasonic transducer and an ultrasonic defects detecting system. An LC matching circuit is the most frequently used electric matching method. It is necessary for the electrical impedance of an ultrasonic transducer to correspond to approximately $50{\Omega}$ to compensate the difference in electrical impedance between both connections. In this study, a 15 MHz immersion ultrasonic transducer was fabricated and an LC electrical impedance circuit was applied to that for having broad-band frequency characteristic.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.595-598
• /
• 2006

In this letter, a compact rectangular spiral antenna is proposed. Instead of a center excitation of conventional spiral antennas, the proposed antenna is adopted a modified feed network, feeding at the end of the spiral. The matching circuit of $'{\sqsupset}'$ shape is added at the feeding point. With this matching circuit, we can easily match the input impedance well, without the limit of the space. The parameter which determines the circular wave characteristic is explained, and the design guideline of the proposed antenna is presented. We design a proposed antenna operating at 9.5 GHz. Its size is only $0.6\lambda_g\times0.6\lambda_g$. The simulated bandwidth of the input impedance $(S11\leq-10)$ is 8.12% and that of $(AR\leq-3)$ is 4.62%, which is excellent characteristics as compared to its simple structure.

• Journal of Korea Society of Industrial Information Systems
• /
• v.6 no.4
• /
• pp.89-94
• /
• 2001

A new design method of the microwave multisection impedance transformer is proposed. This method is based on the inverse scattering theory using the frequency domain reflection coefficient of the transformer to be designed. In the first step, the permittivity profile of a virtual one-dimensional dielectric medium is reconstructed using the desired reflection coefficient. In the second step, the transformer which is equivalent to the reconstructed dielectric medium in view of reflection characteristics is synthesized. Theoretically, this method can be used to design the impedance matching transformers with arbitrary passband characteristics within the limit of the Bode-Fano criteria[1]. Our approach is examined for two design examples to show that it is valid.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.5
• /
• pp.462-475
• /
• 1997

In this paper, the accurate characterization of the input impedance of a rectangular waveguide with a conducting post and the other discontinuity is presented using mode matching method and the equivalent transmission line theory. By the proposed method, the input impedance of rectangular waveguide with a conducting post and the other discontinuity as a function of the radius and height of the post, the reflection coefficient of the other discontinuity, and the distance between the post and the other discontinuity is calculated. The simulated result shows good agreement with the experimental result by Marcuvitz.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.7
• /
• pp.3191-3196
• /
• 2013

Ultrasonic transducer is the sensor which is measuring distance. Piezo ceramic of ultrasonic sensor and adhesive technique of matching layer are the most core techniques. With the study of relation on matching layer which takes off the ultrasonic wave into the air, this paper aims to find the second useful frequency as the results which can be changed are extracted in case piezo ceramic and matching layer are bonded. And the experiment is done with piezo ceramic as real piezoelectric element and matching layer of chemical wood. OD of piezo ceramic has designed by ${\Phi}50{\times}3T$ and OD of matching layer is designed by ${\Phi}62{\times}12t$ with ${\lambda}=1/4$. Acoustic impedance is generated at the most optimum resonant frequency of 53 Khz. As experimental result, more available frequency can be generated by using the adhesive close to solid than the flexible one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.2 s.105
• /
• pp.193-197
• /
• 2006

Radiation properties of flush mounted circular patch antennas are investigated. The patch is fed axis-symmetrically by a coaxial cable. Rigorous analysis iscarried out using integral transform and mode matching techniques. The presented method can accommodate a radiating patch, integrated matching section and band pass filter.

• Proceedings of the KAIS Fall Conference
• /
• 2009.12a
• /
• pp.846-849
• /
• 2009

본 논문에서는 듀얼 밴드(UHF: 470-862 MHz, L: 1452-1492 MHz) DVB-H 안테나를 제작하였다. 제안된 안테나는 입력 임피던스 매칭 회로를 이용한 평판형 역 F 안테나(PIFA)로 구성되었다. 급전점에 구성된 매칭 회로는 안테나의 광대역(UHF: 470-862 MHz: 63%) 동작특성을 만족시킨다. 제시된 안테나는 전방향적 방사특성을 가지며 상용 모바일(PMP)에 적용가능한 충분한 이득(최대이득: 1.70dBi)을 보인다. 또한 안테나는 유전율($\varepsilon_r$ = 3.2)인 PMP 케이스에 부착되어 상용 모바일용으로 소형화 되었다.

• Proceedings of the KIEE Conference
• /
• 2006.07d
• /
• pp.2189-2190
• /
• 2006

본 논문에서는 Half Bridge Series Resonant Inverter 를 이용한 유도가열 시스템 설계를 하고 제작하여 구현하였다. 이러한 유도가열 시스템의 제작을 위해서는 공진탱크와 매칭 트랜스포머의 설계가 필수적이다. 따라서 이런 설계를 위해 Pspice 를 이용하여 공진탱크의 입력 임피던스 Bode Polt 을 그려 분석하고 이를 바탕으로 탱크회로를 설계 하였다. 매칭 트랜스포머의 설계는 출력 Power 와 1,2 차 회로 조건에 의해 설계 되어졌다. 이렇게 설계한 유도가열 시스템을 Pspice 를 이용해서 Simulation 함으로써 주파수에따른 출력 Power 의 변화를 볼수 있었으며, 유도가열 시스템을 실제 제작하여 구현함으로써 확인하였다.

• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.557-558
• /
• 2006

본 논문에서는 Half Bridge Series Resonant Inverter를 이용한 유도가열 시스템 설계를 하고 제작하여 구현하였다. 이러한 유도가열 시스템의 제작을 위해서는 공진탱크와 매칭 트랜스포머의 설계가 필수적이다. 따라서 이런 설계를 위해 PSpice를 이용하여 공진탱크의 입력 임피던스 Bode Plot 을 그려 분석하고 이를 바탕으로 탱크회로를 설계 하였다. 매칭 트랜스포머의 설계는 출력 Power 와 1,2 차 회로 조건에 의해 설계 되어졌다. 이렇게 설계한 유도가열 시스템을 PSpice 를 이용해서 Simulation 함으로써 주파수에 따른 출력 Power의 변화를 볼 수 있었으며, 유도가열 시스템을 실제 제작하여 구현함으로써 확인하였다.