• ETRI Journal
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• v.42 no.4
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• pp.491-504
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• 2020

We present AB9, a neural processor for inference acceleration. AB9 consists of a systolic tensor core (STC) neural network accelerator designed to accelerate artificial intelligence applications by exploiting the data reuse and parallelism characteristics inherent in neural networks while providing fast access to large on-chip memory. Complementing the hardware is an intuitive and user-friendly development environment that includes a simulator and an implementation flow that provides a high degree of programmability with a short development time. Along with a 40-TFLOP STC that includes 32k arithmetic units and over 36 MB of on-chip SRAM, our baseline implementation of AB9 consists of a 1-GHz quad-core setup with other various industry-standard peripheral intellectual properties. The acceleration performance and power efficiency were evaluated using YOLOv2, and the results show that AB9 has superior performance and power efficiency to that of a general-purpose graphics processing unit implementation. AB9 has been taped out in the TSMC 28-nm process with a chip size of 17 × 23 ㎟. Delivery is expected later this year.

• Journal of electromagnetic engineering and science
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• v.11 no.1
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• pp.16-26
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• 2011

This paper presents high power and high efficiency Doherty amplifiers for 2.345 GHz wireless broadband (WiBro) applications that use a Nitronex 125-W ($P_{3dB}$) GaN high electron mobility transistor (HEMT). Two- and three-way Doherty amplifiers and a saturated Doherty amplifier using Class-F circuitry are implemented. The measured result for a center frequency of 2.345 GHz shows that the two-way Doherty amplifier attains a high $P_{3dB}$ of 51.5 dBm, a gain of 12.5 dB, and a power-added efficiency (PAE) improvement of about 16 % compared to a single class AB amplifier at 6-dB back-off power region from $P_{3dB}$. For a WiBro OFDMA signal, the Doherty amplifier provides an adjacent channel leakage ratio (ACLR) at 4.77 MHz offset that is -33 dBc at an output power of 42 dBm, which is a 9.5 dB back-off power region from $P_{3dB}$. By employing a digital pre-distortion (DPD) technique, the ACLR of the Doherty amplifier is improved from -33 dBc to -48 dBc. The measured result for the same frequency shows that the three-way Doherty amplifier, which has a $P_{3dB}$ of 53.16 dBm and a gain of 10.3 dB, and the saturated Doherty amplifier, which has a $P_{3dB}$ of 51.1 dBm and a gain of 10.3 dB, provide a PAE improvement of 11 % at the 9-dB back-off power region and 7.5 % at the 6-dB back-off region, respectively, compared to the two-way Doherty amplifier.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.853-859
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• 2007

This paper presents a microstrip patch array antenna having transmission feed and reception feed for satellite communication in the Ku band. In this paper, the element of the patch array antenna is a three-stacked structure consisting of one radiation patch and two parasitic patches for high gain and wide bandwidth characteristics. To obtain higher gain, the unit elements are expanded into a $1{\times}8$ may using a mixture of series and parallel feeds. The proposed antenna has horizontal polarization for the Rx band and vertical polarization for the Tx band. To verify the practicality of this antenna, we fabricated a three-stacked patch array antenna and measured its performance. The gain of the array antenna in the Rx and Tx bands exceeds 17 and 18 dBi, respectively. The impedance bandwidth is over 10 % in both bands. The cross-polarization level is below -25 dB, and the sidelobe level is below -9.4 dB.

• Korean Journal of Remote Sensing
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• v.23 no.2
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• pp.137-144
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• 2007

In KORDI (Korea Ocean Research and Development Institute), the KOSC (Korea Ocean Satellite Center) construction project is being prepared for acquisition, processing and distribution of sensor data via L-band from GOCI (Geostationary Ocean Color Imager) instrument which is loaded on COMS (Communication, Ocean and Meteorological Satellite); it will be launched in 2008. Ansan (the headquarter of KORDI) has been selected for the location of KOSC between 5 proposed sites, because it has the best condition to receive radio wave. The data acquisition system is classified into antenna and RF. Antenna is designed to be $\phi$ 9m cassegrain antenna which has 19.35 G/T$(dB/^{\circ}K)$ at 1.67GHz. RF module is divided into LNA (low noise amplifier) and down converter, those are designed to send only horizontal polarization to modem. The existing building is re-designed and arranged for the KOSC operation concept; computing room, board of electricity, data processing room, operation room. Hardware and network facilities have been designed to adapt for efficiency of each functions. The distribution system which is one of the most important systems will be constructed mainly on the internet. and it is also being considered constructing outer data distribution system as a web hosting service for offering received data to user less than an hour.

• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.135-142
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• 2001

Recently, plastic optical fiber draws a lot of attention as a new transmission medium for local area network (LAN) and home network applications. As PMMA based GI-POF (Graded Index Plastic Optical Fiber) has very low loss at about 500 nm and 650 nm wavelengths, it is very important to have a compact ultra short optical pulse source at these wavelength windows. In this paper, we have investigated detailed characteristics of gain switched laser system by using a commercially available low cost RF devices and an InGaAlP Fabry Perot semiconductor laser operating at 650 nm wavelength. The shortest optical 'pulse obtained was 33 psec with 1 GHz repetition rate. Depending on the DC bias current and the modulation frequency, the FWHM and the pulse energy of the gain switched pulses show 33.3-82.8 psec and 0.97-9.69 pI respectively. Also, the spectral bandwidths for CW and gain switched operations are 0.44 nm and 1.50 nm. We believe that these results are quite useful for high bit rate optical transmission applications with PMMA based plastic optical fibers in addition to estimate properties of ultra fast optical components and electro-optic devices. vices.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.9
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• pp.459-463
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• 2004

In this study, the (l-x)$TiTe_3O_{8}$-x$MgTiO_3$ ceramics were investigated to obtain the improved dielectric properties of a high temperature stability and a sintering temperature of less than $900^{\circ}C$ which was necessary for the LTCC. According to the X-ray diffraction patterns of the (l-x)$TiTe_3O_{8}$-x$MgTiO_3$(x=0∼1) ceramics, the columbite structure of $TiTe_3O_{8}$ and ilmenite structure of $MgTiO_3$ were coexisted. Increasing the $MgTiO_3$ mole ratio(x), the density and dielectric constant were decreased and temperature coefficient of resonant frequency was moved to the negative direction and the quality factor was increased. In the case of the 0.6$TiTe_3O_{8}$-0.4$MgTiO_3$ ceramics sintered at $830^{\circ}C$ for 3hr., the microwave dielectric properties were $\varepsilon_{\gamma}$=29.3, Q${\times}$$f_{\gamma}$=39.600GHz and $\tau$$_{f}$=+9.3ppm/$^{\circ}C$.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.1
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• pp.46-52
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• 2009

This paper design QHA(quadrifilar helical antenna) to receive efficiently Satellite-Digital Multimedia Broadcasting video signal. It is designed as quadrifilar structure with phase variation $0^{\circ}C$, $90^{\circ}C$, $180^{\circ}C$, $270^{\circ}C$ to obtain circular polarization. Upper gap, turn number and height of QHA are varied to obtain optimization dimensions. Optimization dimensions are gap=2.2mm, turn number=0.9, height=42mm and input reflection coefficient is approximately -5.8dB. Designed QHA can be applied to Satellite-DMB terminal.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.28-34
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• 2010

This paper introduces a new U.S. ultra-wideband(UWB: 3.1~10.6 GHz) 1:2 power divider based on a single section Wilkinson type configuration. The divider provides very flat in-band power splitting, high isolation, low insertion loss, sharp roll-off bandpass filtering, and DC blocking characteristics. The circuit consists of a $\lambda$/4 Y resonator, three capacitively coupled $\lambda$/2 short-circuited lines, and a resistor between the two output ports. The circuit structure was simulated with ADS and HFSS, and realized with low-temperature co-fired ceramic(LTCC) green tape, which has a dielectric constant of 7.8. $|S_{11}|$ better than 10 dB, $|S_{21}|$ and $|S_{31}|$ less than 3.2 dB, with both $|S_{22}|$ and $|S_{32}|$ measured as better than 12 dB for the whole UWB band. Measurement results agree closely with HFSS simulation results. The power divider has a compact size of $4\times9\times0.6mm^3$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.14-24
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• 2001

An active MMIC L-band down converting mixer was designed by using GaAs FET with 0.5 ${\mu}$m gate length and 300 ${\mu}$m gate width. Main circuit topology was cascoded two active FETs. It consumed only 7.5 mA with 3V DC voltage supply. Conversion gain of 6.63 dB, minumium noise figure of 5.06 dB and Input $3^{rd}$ Order Intercept Point of 6.4 dBm were obtained. The chip size is 1.86 mm ${\times}$ 1.28 mm.

• ETRI Journal
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• v.28 no.1
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• pp.9-16
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• 2006

In this paper, we analyzed and measured the electrical crosstalk characteristics of a 1.25 Gbps triplexer module for Ethernet passive optical networks to realize fiber-tothe-home services. Electrical crosstalk characteristic of the 1.25 Gbps optical triplexer module on a resistive silicon substrate should be more serious than on a dielectric substrate. Consequently, using the finite element method, we analyze the electrical crosstalk phenomena and propose a silicon substrate structure with a dummy ground line that is the simplest low-crosstalk layout configuration in the 1.25 Gbps optical triplexer module. The triplexer module consists of a laser diode as a transmitter, a digital photodetector as a digital data receiver, and an analog photodetector as a cable television signal receiver. According to IEEE 802.3ah and ITU-T G.983.3, the digital receiver and analog receiver sensitivities have to meet -24 dBm at $BER=10^{-12}$ and -7.7 dBm at 44 dB SNR. The electrical crosstalk levels have to maintain less than -86 dB from DC to 3 GHz. From analysis and measurement results, the proposed silicon substrate structure that contains the dummy line with $100\;{\mu}m$ space from the signal lines and 4 mm separations among the devices satisfies the electrical crosstalk level compared to a simple structure. This proposed structure can be easily implemented with design convenience and greatly reduce the silicon substrate size by about 50 %.