• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.7
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• pp.807-815
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• 2019

In this paper, we design a power amplifier to support quad-band in wireless communication devices using RF CMOS 180-nm process. The proposed power amplifier consists of low-band 0.9, 1.8, and 2.4 GHz and high-band 5 GHz. We proposed a structure that can support each input matching network without using a switch. For maximum linear output power, the output matching network was designed for impedance conversion to the power matching point. The fabricated quad-band power amplifier was verified using modulation signals. The long-term evolution(LTE) 10 MHz modulated signal was used for 0.9 and 1.8 GHz, and the measured output power is 23.55 and 24.23 dBm, respectively. The LTE 20 MHz modulated signal was used for 1.8 GHz, and the measured output power is 22.24 dBm. The wireless local area network(WLAN) 802.11n modulated signal was used for 2.4 GHz and 5.0 GHz. We obtain maximum linear output power of 20.58 dBm at 2.4 GHz and 17.7 dBm at 5.0 GHz.

• Journal of the Optical Society of Korea
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• v.19 no.3
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• pp.297-302
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• 2015

Terahertz (THz) wave generation from bulk and periodically poled $LiTaO_3$ (PPLT) with a Cherenkov phase matching scheme is numerically investigated. It is shown that by using the crystal birefringence of bulk $LiTaO_3$ and a grating vector of PPLT, THz waves can be efficiently generated by difference frequency generation (DFG) with a Cherenkov phase matching scheme. The frequency tuning characteristics of the THz wave via varying wavelength of difference frequency waves, phase matching angle, poling period of PPLT and working temperature are theoretically analyzed. The parametric gain coefficient in the low-loss limit and the absorption coefficient of the THz wave during the DFG process in the vicinity of polariton resonances are numerically analyzed. A THz wave can be efficiently generated by utilizing the giant second order nonlinearities of $LiTaO_3$ in the vicinity of polariton resonances.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1601-1602
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• 2006

A cascode low noise amplifier(LNA) for a 2.45GHz RFID reader is designed using 0.25um CMOS technology. There are four LNA design techniques applied to the cascode topology. In this paper, power-constrained simultaneous noise and input matching(PCSNIM) technique is used for low power consumption and achieving the noise matching and input matching simultaneously. Simulation results demonstrate a noise figure of 2.75dB, a power gain of 10.17dB, and a dissipation power of 8.65mW with 1V supply.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.480-486
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• 2012

In the design of electro acoustic transducer, power factor improvement circuit is more required rather than impedance matching if the driving power amplifier has little inner resistance. Many research results have been focused on the power matching circuit designing for transferring maximum power in the wideband. There are few results in the designing study on the power factor improvement for the wide band electro acoustic transducer. In this paper, we propose a new design method on the power factor improvement for the wide band electro acoustic transducer. The proposed method consists of two steps, the chebyschev matching method and the constrained optimization, respectively.

• ETRI Journal
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• v.38 no.3
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• pp.568-578
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• 2016

A wireless power transfer (WPT) system is usually classified as being of either a two-coil or four-coil type. It is known that two-coil WPT systems are suitable for short-range transmissions, whereas four-coil WPT systems are suitable for mid-range transmissions. However, this paper reveals that the two aforementioned types of WPT system are alike in terms of their performance and characteristics, differing only when it comes to their matching-network configurations. In this paper, we first find the optimum load and source conditions using Z-parameters. Then, we estimate the maximum power transfer efficiency under the optimum load and source conditions, and we describe how to configure the matching networks pertaining to both types of WPT system for the given optimum load and source conditions. The two types of WPT system show the same performance with respect to the coupling coefficient and load impedance. Further, they also demonstrate an identical performance in the two cases considered in this paper, that is, a strong-coupled case and a weak-coupled case.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.251-254
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• 2016

An energy-efficient object matching accelerator is proposed for mobile object recognition based on matching prediction scheme. Conventionally, vocabulary tree has been used to save the external memory bandwidth in object matching process but involved massive internal memory transactions to examine each object in a database. In this paper, a novel object matching accelerator is proposed based on matching predictions to reduce unnecessary internal memory transactions by mitigating non-target object examinations, thereby improving the energy-efficiency. Experimental results show a 26% reduction in power-delay product compared to the prior art.

• Journal of Information Processing Systems
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• v.16 no.6
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• pp.1343-1358
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• 2020

In the stagewise arithmetic orthogonal matching pursuit algorithm, the weak threshold used in sparsity estimation is determined via maximum iterations. Different maximum iterations correspond to different thresholds and affect the performance of the algorithm. To solve this problem, we propose an improved variable weak threshold based on the stagewise arithmetic orthogonal matching pursuit algorithm. Our proposed algorithm uses the residual error value to control the weak threshold. When the residual value decreases, the threshold value continuously increases, so that the atoms contained in the atomic set are closer to the real sparsity value, making it possible to improve the reconstruction accuracy. In addition, we improved the generalized Jaccard coefficient in order to replace the inner product method that is used in the stagewise arithmetic orthogonal matching pursuit algorithm. Our proposed algorithm uses the covariance to replace the joint expectation for two variables based on the generalized Jaccard coefficient. The improved generalized Jaccard coefficient can be used to generate a more accurate calculation of the correlation between the measurement matrixes. In addition, the residual is more accurate, which can reduce the possibility of selecting the wrong atoms. We demonstrate using simulations that the proposed algorithm produces a better reconstruction result in the reconstruction of a one-dimensional signal and two-dimensional image signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.401-410
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• 2014

This paper presents a high-efficiency concurrent dual-band Class-E power amplifier(PA) that is based on a multi-harmonic matching network(MHMN). The proposed MHMN controls the impedance at 1.3 GHz, 2.1 GHz, and their second and third harmonics, respectively, by using transmission lines only rather than switches or lumped components. The dual-band Class-E PA is implemented using Avago ATF-50189 GaAs p-HEMT. The PA exhibits a measured output power of 27.1 dBm and 25.7 dBm, a power gain of 6.1 dB and 4.7 dB, and a drain efficiency of 71.2 % and 60.1 % at 1.3 GHz and 2.1 GHz, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.661-668
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• 2012

A coaxial-cable impedance transformer that can be used in high power and wideband frequency range is an arbitrary impedance transformation ratio by an additional coaxial cable. The coaxial-cable impedance transformer to be 50-${\Omega}$ to 25-${\Omega}$ impedance transformation ratio is easily operated an wideband power divider by connecting two 50-${\Omega}$ lines at 25-${\Omega}$ impedance point. This wideband power divider has a poor output matching characteristic and a poor isolation characteristic between two output ports. In this paper, it proposes a coaxial-cable power divider to be a good output matching and isolation characteristics as it uses the singly terminated filter design theory. The odd-mode operation characteristic of the suggested power divider to use singly terminated low pass filter coefficient due to matching order and ripple value is examined by ADS program. And, it fabricates and measures the operation characteristic of 2-way power divider with 2nd-order and 4th-order matching circuit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.602-607
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• 2006

In this paper, the distributed network synthesis, which is useful to the design of wireless power amplifiers, is proposed, and a RF power amplifier is designed using the technique. The transfer function of distributed matching circuits is derived by Chebyshev approximation, and network element values for a specified topology are given as a function of minimum insertion losses and ripples. As an example, after a power transistor is modeled by load-pull data, the synthesis for distributed matching networks is applied to a power amplifier design, which has the electrical performance of 17dB gain and less IM3 than -43dBc at the 20W output power between 800 to 900MHz frequency range. Experimental results from a fabricated amplifier are shown to approach the design performance in the operating frequency range. The design of impedance matching networks by the transfer function synthesis is a useful method for the design of RF power amplifiers.