• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.165-170
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• 2002

In order to solve the problem of system efficiency reduced on account of two stage power conversion, we propose a series resonant full bridge Inverter circuit for battery-fed microwave oven. This circuit has both a compact size and a light weight comparing with the conventional HVT(High Voltage Transformer) method. Also, it may be adjusted power levels of the microwave oven by a frequency control. In this paper, operational principles are explained in detail in order to understand the circuit operation. Also, a proto-type Inverter circuit with 1[kW] Power consumption is built and tested for verifying the operation.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.5
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• pp.463-468
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• 2017

One of the most critical part for magnetron driving in microwave oven is start-up control. For this, switching frequency of resonant inverter should be carefully controlled in order to supply sufficient power to the filament of the magnetron and to prevent rectifier diode from destruction caused by the excessive voltage across them. This paper proposes a novel start-up control strategy for LLC resonant inverter for microwave oven considering the non-oscillation mode time and the magnetron voltage during the start-up process. The validity of the proposed method is verified through the experiment with 1,200W microwave oven using LLC resonant inverter.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.21-25
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• 2017

Background: We are developing L-band and S-band microwave dielectric absorption systems aiming novel dosimetry using DNAs, such as plasmid DNA and genomic DNA, and microwave technology. Materials and Methods: Each system is composed of a cavity resonator, analog signal generator, circulator, power meter, and oscilloscope. Since the cavity resonator is sensitive to temperature change, we have made great efforts to prevent the fluctuation of temperature. We have developed software for controlling and measurement. Results and Discussion: By using this system, we can measure the resonance frequency, f, and ${\Delta}Q$ (Q is a dimensionless parameter that describes how under-damped an oscillator or resonator is, and characterizes a resonator's bandwidth relative to its center frequency) within about 3 minutes with high accuracy. Conclusion: This system will be expected to be applicable to DNAs evaluations and to novel dosimetric system.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.218.1-218.1
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• 2014

In order to measure the absolute plasma density, various probes are proposed and investigated and microwave probes are widely used for its advantages (Insensitivity to thin non-conducting material deposited by processing plasmas, High reliability, Simple process for determination of plasma density, no complicate assumptions and so forth). There are representative microwave probes such as the cutoff probe, the hairpin probe, the impedance probe, the absorption probe and the plasma transmission probe. These probes utilize the microwave interactions with the plasma-sheath and inserted structure (probe), but frequency range used by each probe and specific mechanisms for determining the plasma density for each probe are different. In the recent studies, behaviors of each microwave probe with respect to the plasma parameters of the plasma density, the pressure (the collision frequency), and the sheath width is abundant and reasonably investigated, whereas relative diagnostic characteristics of the probes by a comparative study is insufficient in spite of importance for comprehensive applications of the probes. However, experimental comparative study suffers from spatially different plasma characteristics in the same discharge chamber, a low-reproducibility of ignited plasma for an uncertainty in external discharge parameters (the power, the pressure, the flow rate and so forth), impossibility of independently control of the density, the pressure, and the sheath width as well as expensive and complicate experimental setup. In this paper, various microwave probes are simulated by finite-different time-domain simulation and the error between the input plasma density in FDTD simulations and the measured that by the unique microwave spectrums of each probe is obtained under possible conditions of plasma density, pressure, and sheath width for general low-temperature plasmas. This result shows that the each probe has an optimum applicable plasma condition and reliability of plasma density measurement using the microwave probes can be improved by the complementary use of each probe.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1279-1288
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• 2004

In this paper, the DMR(Digital Microwave Radio) system-based OFDM(Orthogonal Frequency Division Multiplexing) scheme in microwave channel environments has been proposed and system performances have been evaluated. The existing single carrier DMR system has a complex system structure due to using high-level QAM(Quadrature Amplitude Modulation) modulation scheme and so charmel capacity is limited by sensitive effects from fading. Therefore, in the proposed DMR system, it uses that the OFDM scheme for enhancement of fading distortion and also uses that the band-limited pulse shaping filter instead of windowing for no additional data such as GI/GB and for using efficient of IFFT/FFT block. The performance of OFDM/QPSK-DMR system and single carrier DMR system are analysed by computer simulation using two-ray model under the microwave channel environments The computer simulation results confirm that the fade margin of the proposed OFDM/QPSK-DMR system is highly increased as the number of sub-carriers is larger.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.11
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• pp.1721-1727
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• 1989

Carbon-ferrite microwave absorbers were designed experimentally and fabricated trialy, as a result of which the relative frequency bandwith of 7.3 to 8.2% were obtained under the tolerance limits of the reflection coefficients lower than -20 dB, and the matching thickness becomes 1.4 to 1.6mm, which is significantly thinner than that of the conventional ones. Furthermore, attenuation has been founded by measuring the material constants of the microwave absorbers for microwave oven and the results are compared and discussed.

• Journal of Magnetics
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• v.3 no.2
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• pp.64-67
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• 1998

Microwave absorbing properties of ferrite-epoxy composite (absorbing layer) attached on the carbon fiber polymer composite (reflective substrate) are analyzed on the basis of wave propagation theory. A modified equation for wave-impedance-matching at the front surface of absorbing layer including the effect of electrical properties of the quasi-conducting substrate is proposed. Based on this analysis, the frequency and layer dimension that produce zero-reflection can be estimated from the intrinsic material properties of the obsorbing layer and the substrate. It is demonstrated that the microwave reflectivity of carbon fiber composite has a strong influence on the microwave absorbance of front magnetic layer.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.90-94
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• 2000

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage capacitor(HVC). Though it is simple transformer is bulky heavy and has low-efficiency. To improve this defect a high frequency switching inverter-type power supply has been investigated an developed. in recent years. But because of it's additional circuit and devices inverter-type power supply is more expensive than conventional one. In this paper The design procedure of a novel HVC embedded high frequency transformer is proposed for down-sizing and cost reduction. Also transformer equivalent circuit model is derived by FEM analysis and parameter measurements. And the operation of proposed HVC embedded transformer is verified by simulation and experimental results.

• Current Optics and Photonics
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• v.2 no.1
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• pp.34-38
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• 2018

An X-band microwave photonic (MWP) filter using switch-based fiber-optic delay lines has been proposed and experimentally demonstrated. It is composed of two electro-optic modulators (EOMs) and $2{\times}2$ optical MEMS-switch-based fiber-optic delay lines. By changing time-delay difference and coefficients of each wavelength signal by using fiber-optic delay lines and an electro-optic modulator, respectively, a bandpass filter or a notch filter can be implemented. For an X-band MWP filter with four channel elements, fiber-optic delay lines with the unit time-delay of 50 ps have been experimentally realized and the frequency responses corresponding to the time-delays has been measured. The measured frequency response error at center frequency and the time-delay difference error were 180 MHz at 10 GHz and 3.2 ps, respectively, when the fiber-optic delay line has the time-delay difference of 50 ps.

• Journal of the Korean Ceramic Society
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• v.51 no.1
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• pp.32-36
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• 2014

The effects of an amphiphilic agent and the orientation of BN on the microwave dielectric properties of BN / polyvinyl butyral (PVB) composites were investigated as a function of the BN content in volume fractions from 0.1 to 0.5 ($V_f$). The plate-shaped BN samples were oriented in the PVB matrix by physical processes, in this case tape casting and laminate methods. With an increase in the BN content, the dielectric constant (K) increased because the K of BN was higher than that of the PVB. At the same BN content, composites with an in-plane orientation of the BN showed a higher dielectric constant than that of composites with a transverse orientation of the BN because the ceramics were oriented parallel to the electric field. All of the composites showed nearly constant K values ranging from 1 to 9.4 GHz, indicating good frequency stability over a wide frequency range. At the same frequency, the K values of the composites increased with an increase in the BN content.