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Highly Efficient Dual-Switch Hybrid Switching Supply Modulator for Envelope Tracking Power Amplifier
Dongsu Kim,Daehyun Kang,Jooseung Kim,Yunsung Cho,Bumman Kim IEEE 2012 IEEE microwave and wireless components letters Vol.22 No.6
<P>This letter describes a highly efficient dual-switch hybrid switching supply modulator for an envelope tracking power amplifier (PA). The supply modulator has a combined structure of a linear amplifier and a switching amplifier. For an improved efficiency, the switching amplifier employs two buck converters and realizes an adaptive slew rate control of the switching amplifier's current. An implemented envelope tracking PA delivers an efficiency of 39.1% at an output power of 27 dBm for long term evolution signal with 10 MHz channel bandwidth.</P>
A Highly Integrated Triple-Band RF Front-End Module for WiMAX Applications
KIM, Dongsu,KIM, Dong Ho,RYU, Jong In,PARK, Chong-Dae,KIM, Jun Chul,PARK, Jong Chul The Institute of Electronics, Information and Comm 2010 IEICE transactions on electronics Vol.93 No.8
<P>This paper presents a compact and highly integrated triple-band RF front-end module (FEM) for worldwide interoperability for microwave access (WiMAX) applications using multilayer low temperature co-fired ceramic (LTCC) technology. The proposed RF FEM is composed of a TX triplexer, an RX triplexer, and a TX/RX switch. Both TX and RX triplexers are fully embedded in an LTCC substrate and the TX/RX switch is placed on the substrate. The TX triplexer consists of 2- and 5-GHz lowpass filters, a 3-GHz highpass filter, and a matching circuit. On the other hand, the RX triplexer consists of miniaturized 2-, 3-, 5-GHz coupled-resonator bandpass filters and a matching circuit, which are stacked up for space saving. In TX path, the RF FEM provides an insertion loss of 1.8dB, 2.1dB and 2.5dB at 2-, 3-, and 5-GHz band, respectively, with a high second-harmonic suppression characteristic. In RX path, the RF FEM also provides a low insertion loss at three passbands with high attenuation at other passbands. The size of the proposed RF FEM is only 4.0mm × 5.0mm with a substrate thickness of 0.73mm. The measured results are in good agreement with the simulated results.</P>
STRONG INFLUENCE OF THE GALACTIC MAGNETIC FIELD ON THE PROPAGATION OF ULTRA-HIGH ENERGY COSMIC RAYS
KIM, JIHYUN,KIM, HANG BAE,RYU, DONGSU The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
The galactic magnetic field (GMF) and the intergalactic magnetic field (IGMF) affect the propagation of ultra-high energy cosmic rays (UHECRs) from the source to us. Here we examine the influences of the GMF/IGFM and the dependence of their sky distribution on galactic latitude, b. We analyze the correlation between the arrival direction (AD) of UHECRs observed by the Pierre Auger Observatory and the large-scale structure of the universe in regions of sky divided by b. Specifically, we compare the AD distribution of observed UHECRs to that of mock UHECRs generated from a source model constructed with active galactic nuclei. Our source model has the smearing angle as a free parameter that reflects the deflection angle of UHECRs from the source. The results show that larger smearing angles are required for the observed distribution of UHECRs in lower galactic latitude regions. We obtain, for instance, a $1{\sigma}$ credible interval for smearing angle of $0^{\circ}{\leq}{\theta}_s{\leq}72^{\circ}$ at high galactic latitudes, $60^{\circ}$ < $\left|{b}\right|{\leq}90^{\circ}$, and of $75^{\circ}{\leq}{\theta}_s{\leq}180^{\circ}$, $-30^{\circ}{\leq}b{\leq}30^{\circ}$, at low galactic latitudes, respectively. The results show that the influence of the GMF is stronger than that of the IGMF. In addition, we can estimate the strength of GMFs by these values; if we assume that UHECRs would have heavier nuclei, the estimated strengths of GMF are consistent with the observational value of a few ${\mu}G$. More data from the future experiments may make UHECR astronomy possible.
SGX-Tor: A Secure and Practical Tor Anonymity Network With SGX Enclaves
Kim, Seongmin,Han, Juhyeng,Ha, Jaehyeong,Kim, Taesoo,Han, Dongsu Institute of Electrical and Electronics Engineers, 2018 IEEE/ACM transactions on networking Vol.26 No.5
<P>With Tor being a popular anonymity network, many attacks have been proposed to break its anonymity or leak information of a private communication on Tor. However, guaranteeing complete privacy in the face of an adversary on Tor is especially difficult, because Tor relays are under complete control of world-wide volunteers. Currently, one can gain private information, such as circuit identifiers and hidden service identifiers, by running Tor relays and can even modify their behaviors with malicious intent. This paper presents a practical approach to effectively enhancing the security and privacy of Tor by utilizing Intel SGX, a commodity trusted execution environment. We present a design and implementation of Tor, called SGX-Tor, that prevents code modification and limits the information exposed to untrusted parties. We demonstrate that our approach is practical and effectively reduces the power of an adversary to a traditional network-level adversary. Finally, SGX-Tor incurs moderate performance overhead; the end-to-end latency and throughput overheads for HTTP connections are 3.9% and 11.9%, respectively.</P>
A Triplexer Module with a GPS SAW Filter and a Cellular SAW Duplexer
Dongsu Kim,Jong In Ryu,Jun Chul Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This paper presents a compact and high integrated triplexer module for cellular/GPS/USPCS applcations using multilayer low temperature co-fired ceramic (LTCC) technology. The proposed triplexer module consists of two fully embedded diplexers, a quarterwave- length stripline, a GPS SAW filter, and a cellular SAW duplexer. The overall size of the triplexer is 4.5 ㎜ × 3.2 ㎜. The measured result of the triplexer module shows that the insertion losses are less than 0.4 ㏈ and 0.9 ㏈ in cellular and USPCS bands, respectively. The insertion loss at GPS path is about 2.2 ㏈ including a loss of GPS SAW filter. Also, this module provides an insertion loss of 2.5 ㏈ and 4.7 ㏈ in cellular Tx and Rx bands, respectively.