• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.19-25
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• 2008

In this paper, the front end module (FEM) was proposed for 2.4GHz WLAN band by LTCC multilayer application. The FEM was composed of power amplifier IC, switch IC, and LTCC module. LTCC module consists of output matching circuit and lowpass filter as Tx part, bandpass filter as Rx part. Design of output matching circuit for LTCC was used matching parameter from output matching circuit based on lumped circuit on the PCB board. The dielectric constant of LTCC substrate is 9. The substrate was composed of total 26 layers with each 30um thickness. Ag paste was used for the internal pattern as the conductor material. The size of the module is $4.5mm{\times}3.2mm{\times}1.4mm$. The fabricated FEM showed the gain of 21dB, ACPR of less than -31dBc first side lobe and Less than -59dBc second side lobe and the output power of 23Bm at P1dB.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.186-188
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• 2008

The wireless communication revolution has spawned a revival of interest in the design and optimization of radio transceivers. Radio transmit modules continue to shrink in die size and cost, requiring novel approaches for integration of the numerous passive elements of the radio front-end. A 3 dB Wilkinson power divider based on GaAs substrates, for DCS 1710-1880 MHz band was designed and fabricated showing excellent performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.638-646
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• 2005

In recent wireless communications, direct conversion transceiver or If sampling SDR-based receivers have being designed as an alternative to conventional transceiver topologies. In direct conversion receiver a.chitectu.e, the 1.equency/phase offset between the RF input signal and the local oscillator signal is a major impairment factor even though the conventional AFC/APC compensates the service deterioration due to the offset. To rover the limited tracking range of the conventional method and effectively aid compensation scheme in terms of I/Q channel imbalances, the frequency/phase offset compensation in RF-front end signal stage is proposed in this paper. In RF-front end, the varying phase offset besides the fixed large frequency/phase offset are corrected by using early-late phase compensator. A more simple frequency and phase tacking function in digital signal processing stage of direct conversion receiver is effectively available by an ingenious frequency/phase offset tracking method in RF front-end stage.

• Journal of Semiconductor Engineering
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• v.2 no.1
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• pp.109-118
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• 2021

This review paper describes the overall operating principle of a discrete-time delta-sigma modulator (DTDSM) and a continuous-time delta-sigma modulator (CTDSM) using a switched-capacitor (SC). In addition, research that has solved the problems related to each delta-sigma modulator (DSM) is introduced, and the latest developments are explained. This paper describes the chopper-stabilization technique that mitigates flicker noise, which is crucial for the DSM. In the case of DTDSM, this paper addresses the problems that arise when using SC circuits and explains the importance of the operational transconductance amplifier performance of the first integrator of the DSM. In the case of CTDSM, research that has reduced power consumption, and addresses the problems of clock jitter and excess loop delay is described. The recent developments of the analog front end, which have become important due to the increasing use of wireless sensors, is also described. In addition, this paper presents the advantages and disadvantages of the three-opamp instrumentation amplifier (IA), current feedback IA (CFIA), resistive feedback IA, and capacitively coupled IA (CCIA) methods for implementing instrumentation amplifiers in AFEs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1078-1085
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• 2011

In this paper, we analyze the relationship between energy per bit and the data rate with the variation of the system bandwidth. A existing power model is mathematical model to express power consumption of each device. In this paper, we have to investigate the system level energy model for the RF front-end of a wireless transceiver. Also, the effects of the signal bandwidth, PAR, date rate, modulation level, transmission distance, specific attenuation of frequency band, and the signal center frequency on the RF front-end energy consumption and system capacity are considered. Eventually, we analyze the relationship between energy per bit and the data rate with the variation of the system bandwidth so that we simulate the minimum energy per bit in the several Gbps data rate using Shannon capacity theory.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.2
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• pp.54-61
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• 1999

This paper describes the design of a 4-Mbps wireless infrared data transceiver chip. The receiver consits of the analog front-end, clock recovery and frame generator, and demodulator. The transmitter consists of the demodulator and LED driver. The versatile analog front- end consisting of multiple amplifiers makes it possible for the chip to be applied to various infrared environments by compensating DC and offset signal components. A 4PPM (pulse position modulation) scheme is used for data transfer in order to meet the IrDA standards. The chip was fabricated in a $0.8-{\mu}m$ 2-poly, 2-metal CMOS technology and dissipates 122mW for ${\pm}2.5V$ supply.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.123-129
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• 2023

In this paper, the frequency synthesis(FS) MMIC and the receive MMICs were developed for a Ka-band compact radar. Also a compact Ka-band frequency synthesizer and a receiver were developed based on those MMICs. The FS MMIC and the wireless-receiver(WR) MMIC to receive the baseband frequency were manufactured by a 65 nm CMOS process and the front-end(FE) MMIC to receive the Ka-band frequency was manufactured by a 150 nm GaN process. Linear frequency modulation waveform and pulse waveform for the transmit signal were measured by output signal of frequency synthesizer. The measured performance of developed receiver including the FE MMICs and the WR MMIC were ≧ 80 dB gain, ≦ 6 dB noise figure and ≧ 10 dBm at OP1dB. The measurement results of the developed frequency synthesizer and the receiver including the manufactured MMICs showed that they could be applied to Ka-band compact radar.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.173-177
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• 1998

Under indoor environment, in case that wireless optical LAN does not obtain the line-of-sight between transmitter and receiver, hemi-spherical lens or reflector must be adopted to get broader beam width. The beam tilt and the fluctuations in amplitude and phase of optical signal through indoor-space occur due to the turbulene. This fading often results in unacceptably large bit error probabilities and thus performance degradation of wireless optical communications. In this paper, when the spherical filter at the front-end of transmitter and receiver is used for wireless optical channel not satisfying line-of-sight, the signal-to-noise ratio as to zenithal angle and the effect from the turbulence due to indoor temperature are investigated.

• Journal of the Korea Society of Computer and Information
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• v.15 no.9
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• pp.129-136
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• 2010

With mobile computing, wireless sensor network and sensor technologies, ubiquitous computing services are being realized and could satisfy the feasibility of ubiquitous healthcare to everyone. This u-Healthcare service can improve life quality of human since medical service can be provided to anyone, anytime, and anywhere. To confirm the vision of u-Healthcare service, we've implemented a healthcare system for heart disease patient which is composed of two components. Front-end collects various signals such as temperature, blood pressure, SpO2, and electrocardiogram, etc. As a backend, medical information server accumulates sensing data and performs back-end processing. To simply transfer these sensing values to a medical team may be too trivial. So, we've designed a model based on context awareness for more improved medical service which is based on artificial neural network. Through rigid experiments, we could confirm that the proposed system can provide improved medical service.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.2
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• pp.355-360
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• 2024

In this paper, in implementing a 4-coil resonant wireless power transmission system, we studied the discharge phenomenon that occurs at the end of the transmitting resonance coil. Resonant wireless power transmission consists of a power supply coil, a transmitting resonance coil, a power receiving resonance coil, and a load coil. The transmitting resonance coil serves to amplify the magnetic field generated from the power supply coil and transmits it to the front receiving resonance coil. When a high current flows through the power supply coil in order to transmit large power, a high voltage is induced at the end of the transmitting resonance coil. It causes line-to-line discharge. Line-to-line discharge phenomenon damages the transmitter case and renders the transmitter unusable. Therefore, in order to eliminate this line-to-line discharge phenomenon, the voltage induced in the transmitting resonance coil that causes line-to-line discharge was analyzed and a solution was proposed.