• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.39-46
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• 2016

This paper describes the third order feedforward delta-sigma modulator with inverter-based integrators and a 1.5bit comparator for the application of audio signal processing. The proposed 3rd-order delta-sigma modulator is multi-bit structure using 1.5 bit comparator instead of operational amplifier. This delta-sigma modulator has high SNR compared with single-bit 4th-order delta-sigma modulator in a low OSR. And it minimizes power consumes and simplified circuit structure using inverter-based integrator and using inverter-based integrator as analogue adder. The modulator was designed with 0.18um CMOS standard process and total chip area is $0.36mm^2$. The measured power cosumption is 28.8uW in a 0.8V analog supply and 66.6uW in a 1.8V digital supply. The measurement result shows that the peak SNDR of 80.7 dB, the ENOB of 13.1bit and the dynamic range of 86.1 dB with an input signal frequency of 2.5kHz, a sampling frequency of 2.56MHz and an oversampling rate of 64. The FOM (Walden) from the measurement result is 269 fJ/step, FOM (Schreier) was calculated as 169.3 dB.

• Progress in Superconductivity
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• v.7 no.1
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• pp.28-35
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• 2005

We propose a method to measure atrial arrhythmias (AA) such as atrial fibrillation (Afb) and atrial flutter (Afl) with a SQUID magnetocardiograph (MCG) system. To detect AA is one of challenging topics in MCG. As the AA generally have irregular rhythm and atrio-ventricular conduction, the MCG signal cannot be improved by QRS averaging; therefore a SQUID MCG system having a high SNR is required to measure informative atrial excitation with a single scan. In the case of Afb, diminished f waves are much smaller than normal P waves because the sources are usually located on the posterior wall of the heart. In this study, we utilize an MCG system measuring tangential field components, which is known to be more sensitive to a deeper current source. The average noise spectral density of the whole system in a magnetic shielded room was $10\;fT/{\surd}Hz(a)\;1\;Hz\;and\;5\;fT/{\surd}Hz\;(a)\;100\;Hz$. We measured the MCG signals of patients with chronic Afb and Afl. Before the AA measurement, the comparison between the measurements in supine and prone positions for P waves has been conducted and the experiment gave a result that the supine position is more suitable to measure the atrial excitation. Therefore, the AA was measured in subject's supine position. Clinical potential of AA measurement in MCG is to find an aspect of a reentry circuit and to localize the abnormal stimulation noninvasively. To give useful information about the abnormal excitation, we have developed a method, separative synthetic aperture magnetometry (sSAM). The basic idea of sSAM is to visualize current source distribution corresponding to the atrial excitation, which are separated from the ventricular excitation and the Gaussian sensor noises. By using sSAM, we localized the source of an Afl successfully.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.45-50
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• 2017

We investigated effect of Zn content on shear strengh of Sn-0.7Cu-xZn and OSP surface finished solder joints. Five pastes of Sn-0.7Cu-xZn (x=0, 0.5, 1.0, 1.5, 2.0 wt.%) solders were fabricated by mixing of solder powder and flux using planatary mixer. $180{\mu}m$ diameter solder balls were formed on OSP surface finished Cu electrodes by screen print method, and the reflow process was performed. The shear strength was evaluated with two high shear speeds; 0.01 and 0.1 m/s. The thickness of the intermetallic compound(IMC) layer was decreased with increasing Zn content in Sn-0.7Cu-xZn solder. The highest shear strength was 3.47 N at the Zn content of 0.5 wt.%. As a whole, the shear strength at condition of 0.1 m/s was higher than that of 0.01 m/s because of impact stress. Fracture energies were calculated by F-x (Force-displacement) curve during high speed shear test and the tendency of fracture energy and that of shear strength were good agreement each other. Fracture took place within solder matrix at lower Zn content, and fracture occured near the interface of OSP surface finished Cu electrode and solder at higher Zn content.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.5 s.335
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• pp.61-68
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• 2005

In this paper, low conversion loss 94 GHz MIMIC resistive mixer was designed and fabricated. The $0.1{\mu}m$ InGaAs/InAlAs/GaAs Metamorphic HEMT, which is applicable to MIMIC's, was fabricated. The DC characteristics of MHEMT are 665 mA/mm of drain current density, 691 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 189 GHz and the maximum oscillation frequency(fmax) is 334 GHz. A 94 GHz resistive mixer was fabricated using $0.1{\mu}m$ MHEMT MIMIC process. From the measurement, the conversion loss of the 94 GHz resistive mixer was 8.2 dB at an LO power of 10 dBm. P1 dB(1 dB compression point) of input and output were 9 dBm and 0 dBm, respectively. LO-RF isolations of resistive mixer was obtained 15.6 dB at 94.03 GHz. We obtained in this study a lower conversion loss compared to some other resistive mixers in W-band frequencies.

• Journal of Sensor Science and Technology
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• v.14 no.1
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• pp.33-41
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• 2005

For more convenient electrode-electrolyte interface impedance analysis in biosensor, a stand-alone impedance measurement system is required. In our study, we developed a PC-based portable system to analyze impedance of the electrochemical cell using microprocessor. The devised system consists of signal generator, programmable amplifiers, A/D converter, low pass filter, potentiostat, I/V converter, microprocessor, and PC interface. As a microprocessor, PIC16F877 which has the processing speed of 5 MIPS was used. For data acquisition, the sampling rate at 40 k samples/sec, resolution of 12 bit is used. RS-232 with 115.2 kbps speed is used for the PC communication. The square wave was used as stimuli signal for impedance analysis and voltage-controlled current measurement method of three-electrode-method were adopted. Acquired voltage and current data are calculated to multifrequency impedance signal after Fourier transform. To evaluate the implemented system, we set up the dummy cell as equivalent circuit of which was composed of resistor, parallel circuit of capacitor and resistor connected in parallel and measured the impedance of the dummy cell; the result showed that there exist accuracy within 5 % errors and reproduction within 1 % errors compared to output of Hioki LCR tester and HP impedance analyzer as a standard product. These results imply that it is possible to analyze electrode-electrolyte interface impedance quantitatively in biosensor and to implement the more portable high speed impedance analysis system compared to existing systems.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.1
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• pp.38-46
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• 1999

o.25${\mu}m$ T-shaped gate P-HEMT is fabricated and used for design of X0band three stage monolithic microwave integrated circuit(MMIC) low noise amplifier(LNA). The fabricated P-HEMT exhibits an extrinsis transconductance of 400mS/mm and a drain current of 400mA/mm. The RF and noise characteristics show that the current gain cut off frequency is 65GHz and minimum noise figure(NFmin) of 0.7dB with an associated gain of 14.8dB at 9GHz. In the design of the three stage LNA, we have used the inductive series feedback circuit topology with the short stub. The effects of series feedback to the noise figure, the gain, and the stability have been investigated to find the optimal short stub length. The designed three staage LNA showed a gain of above 33dB, a noise figure of under 1.2dB, and ainput/output return loss of under 15dB and 14dB, respectively. The results show that the fabricated P-HEMT is very suitable for a X-band LNA with high gain.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.143-149
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• 2008

A novel compact model for a five-port transformer balun is proposed for the efficient circuit design of hybrid balun. Compared to the conventional model, the proposed model provides much faster computation time and more reasonable values for the extracted parameters. The hybrid balun, realized in $0.18\;{\mu}m$ CMOS, achieves 2.8 dB higher gain and 1.9 dB lower noise figure than its passive counterpart only at a current consumption of 0.67 mA from 1.2 V supply. By employing the hybrid balun, a differential zero-IF receiver is designed in $0.18\;{\mu}m$ CMOS for IEEE 802.15.4 ZigBee applications. It is composed of a differential cascode LNA, passive mixers, and active RC filters. Comparative investigations on the three receiver designs, each employing the hybrid balun, a simple transformer balun, and an ideal balun, clearly demonstrate the advantages of the hybrid balun in fully differential CMOS RF receivers. The simulated results of the receiver with the hybrid balun show 33 dB of conversion gain, 4.2 dB of noise figure with 20 kHz of 1/f noise corner frequency, and -17.5 dBm of IIP3 at a current consumption of 5 mA from 1.8 V supply.

• Korean Journal of Biological Psychiatry
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• v.25 no.2
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• pp.38-43
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• 2018

Objectives Dopamine dysregulation has been regarded as one of the core pathologies in patients with schizophrenia. Since dopamine synthesis capacity has found to be inconsistent in patients with schizophrenia, current classification of patients based on clinical symptoms cannot reflect the neurochemical heterogeneity of the disease. Here we performed new subtyping of patients with first-episode psychosis (FEP) through biotype-based cluster analysis. We specifically suggested basal ganglia structural changes as a biotype, which deeply involves in the dopaminergic circuit. Methods Forty FEP and 40 demographically matched healthy participants underwent 3T T1 MRI. Whole brain parcellation was conducted, and volumes of total 6 regions of basal ganglia have been extracted as features for cluster analysis. We used K-means clustering, and external validation was conducted with Positive and Negative Syndrome Scale (PANSS). Results K-means clustering divided 40 FEP subjects into 2 clusters. Cluster 1 (n = 25) showed substantial volume decrease in 4 regions of basal ganglia compared to Cluster 2 (n = 15). Cluster 1 showed higher positive scales of PANSS compared with Cluster 2 (F = 2.333, p = 0.025). Compared to healthy controls, Cluster 1 showed smaller volumes in 4 regions, whereas Cluster 2 showed larger volumes in 3 regions. Conclusions Two subgroups have been found by cluster analysis, which showed a distinct difference in volume patterns of basal ganglia structures and positive symptom severity. The result possibly reflects the neurobiological heterogeneity of schizophrenia. Thus, the current study supports the importance of paradigm shift toward biotype-based diagnosis, instead of phenotype, for future precision psychiatry.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.1
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• pp.28-37
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• 2010

In this paper, the IC (Integrated Circuit) for multi-channel asynchronous communication was designed by using FPGA and VHDL language. The existing chips for asynchronous communication that has been used commercially are composed of one to two channels. Therefore, when communication system with two channels or more is made, the cost becomes high and it becomes complicated for communication system to be realized and also has very little buffer, load that is placed into Microprocessor increases heavily in case of high speed communication or transmission of high-capacity data. The designed IC was improved the function and performance of communication system and reduced costs by designing 8 asynchronous communication channels with only one IC, and it has the size of transmitter/receiver buffer with 256 bytes respectively and consequently high speed communication became possible. To detect errors between communications, it was designed with digital filter and check-sum logic and channel MUX logic so that the malfunction can be prevented and errors can be detected more easily and input/output port regarding each communication channel can be used flexibly and consequently the reliability of system was improved. It was composed and simulated logic of VHDL described by using Cyclone II Series EP2C35F672C8 and QuartusII V8.1 of ALTERA company. In order to show the performance of designed IC, the test was conducted successfully in QuartusII simulation and experiment and the excellency was compared with TL16C550A of TI (Texas Instrument) company and ATmegal28 general-purpose micro controller of ATMEL company that are used widely as chips for asynchronous communication.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.100-105
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• 2021

Recently, all-solid-state batteries have attracted much attention to improve safety of rechargeable lithium batteries, but the solid-state batteries of conductive ceramics or solid polymer electrolytes show poor electrochemical properties because of several problems such as high interfacial resistance and undesired reactions. To solve the problems of the reported all-solid-state batteries, a hybrid solid electrolyte is suggested, in this study, NASICON-type nanoparticle Li_1.5Al_0.5Ti_1.5P₃O₁₂ (LATP) conductive ceramic, PVdF-HFP, and a carbonate-based liquid electrolyte were composited to prepare a quasi-solid electrolyte. The hybrid solid electrolyte has a high voltage stability of 5.6 V and shows an suppress effect of lithium dendrite growth in the stripping-plating test. The LiNi_0.83Co_0.11Mn_0.06O₂ (NCM811)-based battery with the hybrid solid electrolyte exhibits a high discharge capacity of 241.5 mAh/g at a high charge-cut-off voltage of 4.8V and stable electrochemical reaction. The NCM811-based battery also shows 139.4 mAh/g discharge capacity without short circuit or explosion at 90℃. Therefore, the LATP-based hybrid solid electrolyte can be an effective solution to improve the safety and electrochemical properties of rechargeable lithium batteries.