• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.521-524
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• 2015

This letter presents a selective wireless power transfer architecture using a reconfigurable multi-port amplifier. The proposed wireless power transfer architecture is composed of a phase shifter part controlled by FPGA, two class-E power amplifiers, a four-port power combiner and two coil loads. Depending on the phase control of FPGA, the power ratio of outputs at the two coil loads becomes 1:1, 2:0 and 0:2. The manufactured system has delivered 1W DC power to loads at 125 kHz. The total DC-to-DC conversion efficiency shows more than 40 % including PA efficiency of 79 %.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.75-82
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• 2009

This paper proposes a method which increases the linearity using an improvement mechanism of Doherty power amplifier and compensates the decrement of efficiency due to improvement of linearity. To verify the method, a 20W power amplifier is designed and implemented. Compared with 2-way Doherty power amplifier, the implemented 3-way Doherty power amplifier with class F shows improved linearity about 10dBc and efficiency about 1.5%. Also, efficiency characteristic has been improved about 3.5% compared with the 2-way Doherty power amplifier while maintaining linearity. This results show that the proposed 3-way Doherty power amplifier with class F is shown to be adequate for improvement of efficiency and linearity. It is expected that the proposed amplifier can be used for various wireless communication system amplifiers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.3 s.333
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• pp.1-8
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• 2005

In this paper, design and implement 60W Doherty power amplifiers for 3GPP repeater and base station transceiver system. Efficiency improvement and high power property of Doherty power amplifier is distinguishable; however implementation of assistance amplifer is difficult, though. To solve the problem, therefore, GCHD (Gate Control Hybrid Doherty) power amplifier is embodied to gate bias adjusament circuit of assistance amplifier to General Doherty power amplifier. Experiment result shows that $2.11\~2.17GHz$, 3GPP operating frequency band, with 62.55 dB gain, PEP output is 50,76 dBm, W-CDMA average power is 47.81 dBm, and -40.05 dBc ACLR characteristic in 5MHz offset frequency band. Each of the parameter satisfied amplifier specification which we want to design. Especially, GCHD power amplifier shows proper efficiency performance improvement in uniformity ACLR than general power amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.54-58
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• 2011

In this paper a dual-band Class-E power amplifier using Composite Right-/Left-Handed transmission lines and PIN diode is proposed. Dual-band operation is achieved by the frequency offset and nonlinear phase slope of CRLH TL for the matching network of power amplifiers. The proposed power amplifier has been realized by using in the input and the output matching network for high power added efficiency. PIN diode has been used to obtain the dual-band of power amplifier. The measured results show that output powers of 42.17 dBm and 41.43 dBm were obtained at 800 MHz and 1900 MHz, respectively. At this frequency, we have obtained the power-added efficiency(PAE) of 67.84 % and 65.31 % in two operation frequencies, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.183-188
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• 2014

In this paper, the propagation effect of power supply uncertainty on the output of class-F power amplifier has been estimated. Also, a 1.9 GHz, 10 watt class-F power amplifier was measured to verify the estimation and to find the optimal biasing point. By approximating the propagation theory of uncertainties, the propagation effect of bias uncertainty was mathmatically calculated. As a result, the DC biases have propagated uncertainties of 15~70 mW. However, at the optimized bias point, the uncertainty in the output power could be dropped less than 15 mW while the output power has dropped by 0.37 dB.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.56-62
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• 2006

This paper describes the MMIC product qualification of the Ka band satellite transponder for the COMS(Communication, Ocean and Meteorological Satellite). Ka-band active equipment for the COMS communications transponder are being developed by using 12 kinds of MMICs which include low noise amplifiers, medium power amplifiers, frequency mixers, frequency multipliers, RF switch, and HEMT attenuator MMIC, Those MMICs had been fabricated at the MMIC production foundry of northrop Grumman Space Technology (Velocium) which is qualified for space application, and experienced in various space programs during past decades. For the MMIC product qualification, Visual inspection and SEM inspection had been performed, and burn-in test for 240 hours and accelerated life-test for 1000 hours had been done on test fixtures of individual MMIC products at $125^{\circ}C$. Additionally, infrared temperature scanning and finite element simulation were performed to analyze and confirm the channel temperature of semiconductor devices on several representatives of those MMIC products that os one of the most important factors in performance degradation and life reduction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.11
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• pp.16-23
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• 2009

A 12b 10MS/s pipelined ADC with low DC gain amplifiers is presented. The pipelined ADC using a reference scaling technique is proposed to compensate the gain error in MDACs due to a low DC gain amplifier. To minimize the performance degradation of the ADC due to amplifier offset, the proposed offset trimming circuit is employed m the first-stage MDAC amplifier. Additional reset switches are used in all MDACs to reduce the memory effect caused by the low DC gain amplifier. The measured differential and integral non-linearities of the prototype ADC with 45dB DC gain amplifiers are less than 0.7LSB and 3.1LSB, respectively. The prototype ADC is fabricated in a $0.35{\mu}m$ CMOS process and achieves 62dB SNDR and 72dB SFDR with 2.4V supply and 10MHz sampling frequency while consuming 19mW power.

• Publications of The Korean Astronomical Society
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• v.11 no.1
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• pp.109-123
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• 1996

We have developed a 5GHz continuum receiver system. The receiver is a direct type receiver. In order to reduce the noise due to the fluctuation of the gain in the amplifiers, the system employs the Dicke switching method. We made the 5GHz low-noise amplifier and the bandpass filter. The low-noise amplifier gives ${\sim}35dB$ gain and has ${\sim}210K$ noise temperature. The bandpass filter has a passband between 4.3 and 5.4GHz. We also made switch driver, video amplifiers, phase detector, and integrator. Using a 1.8 meter offset parabolic antenna, we measured the efficiency of the system. Since the antenna does not have a driver to track objects, observations were performed with the antenna fixed. The measured noise temperature of the system is ${\sim}650K$. From the observation of the blank sky, noise level was measured. It was found that the systematic noise(${\sim}0.5K$: peak to peak value) is much larger than the thermal noise. The systematic noise is possibly related to the stability of the DC power supplied to the receiver system. Besides the noise of the system, it was found that the airplanes are the very serious noise sources. We measured the radio flux of the Sun using the developed system. The observed radio flux of the Sun is ${\sim}10^6Jy$, which is close to the known value of the quiet Sun. The test observation of the Sun shows that the angular beam size of the antenna is ${\sim}2.2^{\circ}$.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.1
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• pp.61-70
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• 2016

This paper describes a new PMU(parametric measurement unit) design technique for automatic test equipment(ATE). Only one DDA(differential difference amplifier) is used to force the test signals to DUT(device under test), while conventional design uses two or more amplifiers to force test signals. Since the proposed technique does not need extra amplifiers in feedback path, the proposed PMU inherently guarantees stable operation. Moreover, to measure the response signals from DUT, proposed technique also adopted only one DDA amplifier as an IA(instrument amplifier), while conventional IA uses 3 amplifiers and several resistors. The DDA adopted two rail-to-rail differential input stages to handle full-range differential signals. Gain enhancement technique is used in folded-cascode type DDA to get open loop gain of 100 dB. Proposed PMU design enables accurate and stable operation with smaller hardware and lower power consumption. This PMU is implemented with 0.18 um CMOS process and supply voltage is 1.8 V. Input ranges for each force mode are 0.25~1.55 V at voltage force and 0.9~0.935 V at current force mode.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.754-763
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• 2002

This paper discusses the improved power performances of the size-reduced amplifier using defected ground structure (DGS). The slow-wave effect and enlarged electrical length occur due to the additional equivalent circuit elements of DGS. Using these properties, it is possible to reduce the length of transmission lines in order to keep the same original electrical lengths by inserting DGS on the ground plane. The matching and performances of the amplifier are preserved even after DGS patterns have been inserted. While there is no loss in the size-reduced transmission lines at the operating frequency, but there exists loss to some extent at harmonic frequencies. This leads to the more excellent inherent capability of harmonic rejection of the size-reduced amplifier. Therefore, it is expected tile harmonics of the size-reduced amplifier are smaller than those of the original amplifier. The measured second harmonic, third order intermodulation distortion (IMD3), and adjacent channel power ratio (ACPR) of the size-reduced amplifier are smaller than those of the original amplifier by 5 dB, 2~6 dB, and 1~4 dB, respectively, as expectation.