• The Journal of the Korea institute of electronic communication sciences
• /
• v.5 no.2
• /
• pp.180-184
• /
• 2010

In this paper, the filter design and simulation are performed to construct the multi-channel cardiac activation main amplifier. The main amplifier consists of sample and holder, variable high pass filter, notch filter, variable low pass filter. The general 64 channel configuration is expanded into 128 channels to enhance the spatial resolution and the filter is designed for 128 channels cardiac activation main amplifier.

• Journal of Korea Society of Industrial Information Systems
• /
• v.18 no.5
• /
• pp.15-18
• /
• 2013

This paper presents an analog front-end for electroencephalogram(EEG) signal processing. Since EEG signals are typically weak and located at very low frequencies, it is imperative to implement an amplifier with high gain, high common-mode rejection ratio(CMRR) and good noise immunity at very low frequencies. The analog front-end of this paper consists of a programmable-gain instrumentation amplifier and a band-pass filter. A frequency chopping technique is employed to remove the low-frequency noise. The circuits were fabricated in 0.18um CMOS technology and measurements showed that the analog front-end has the maximum gain of 60dB and >100dB CMRR over the programmable gain range.

• Journal of Korea Society of Industrial Information Systems
• /
• v.18 no.5
• /
• pp.1-8
• /
• 2013

This paper presents a variable gain amplifier(VGA) without passive devices. This VGA employes the architecture of current feedback amplifier and variable gain can be achieved by using the GM ratios of two trans-conductance(gm) circuits. To obtain linearity and high gain, it uses current division technique and source degeneration in feedback GM circuits. Input trans-conductance(GM) circuit was biased by using a tunable voltage controller to obtain variable gain. The prototype of the VGA is designed in $0.35{\mu}m$ CMOS technology and it is operating in sub-threshold region for low power consumption. The the gain of proposed VGA is varied from 23dB to 43dB, and current consumption is $2.82{\mu}A{\sim}3{\mu}A$ at 3.3V. The area of VGA is 1$120{\mu}m{\times}100{\mu}m$.

• 한국정보통신설비학회:학술대회논문집
• /
• 2007.08a
• /
• pp.11-14
• /
• 2007

CMOS technology 기반의 고주파 직접회로에서는 충분한 이득과 안정성을 얻기 위하여 inductor, capacitor와 같은 수동 소자를 적절히 사용하여 설계하여야 한다. 이와 같은 수동 소자는 CMOS 집적회로에서 넓은 면적을 차지하는 단점이 있다. 고주파 증폭기의 부하를 능동 소자로 대체하게 되면 작은 크기로 회로의 제작이 가능하게 되나, 능동 소자는 수동 소자에 비하여 선형 특성이 좋지 않기 때문에 실제로 고주파 증폭기 설계에 사용하지 않는다. 본 논문에서는 이와 같은 능동 소자의 비선형성을 억제하면서, 동시에 회로의 크기를 줄일 수 있는 기능성 능동 부하를 적용한 고주파 증폭기를 설계하였다. 기능성 능동 부하는 2개의 MOSFET은 대칭으로 연결된 구조를 가지며, 하나의 MOSFET은 일반적인 load로 동작하며, 다른 MOSFET은 gate에 가변 전압을 인가함으로써, 증폭기의 전달함수를 변화시킬 수 있다. 이와 같은 특성을 이용하여 고주파 증폭기의 선형성을 보상할 수가 있다.

• Proceedings of the KIPE Conference
• /
• 2011.07a
• /
• pp.232-233
• /
• 2011

수중에서는 대기와는 달리 매질의 차이로 인하여 통신의 제약이 따르므로 초음파를 이용하여 정보를 송 수신한다. 수중통신을 하기 위해서는 초음파를 발생시키는 트랜스듀서와 신호를 증폭시키는 전력증폭기가 필요하다. 전력증폭기는 선형적인 출력이 보장되어야 하며, 수중에서의 연료문제로 인하여 높은 효율로 동작하여야한다. 하지만 출력의 선형성과 시스템의 효율은 Trade off의 관계이기 때문에 두 가지 모두를 만족시키는 연구가 요구된다. 그러므로 본 논문에서는 Class B push-pull 증폭기를 사용하여 선형 출력 특성을 보장하며, 신호의 크기에 따라 증폭기의 인가전압을 가변하는 ET(Envelope Tracking) 기술을 적용하여 향상된 효율 특성을 갖는 넓은 대역폭의 전력증폭기를 설계하고 실험을 통해 특성을 확인하였다.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1996.06a
• /
• pp.226-229
• /
• 1996

• Korean Journal of Optics and Photonics
• /
• v.18 no.1
• /
• pp.66-73
• /
• 2007

The various output characteristics of a pulsed Ti:sapphire laser oscillator with a plane-parallel resonator, pumped longitudinally by the second harmonic wave of a Nd:YAG laser, and the output of a Ti:sapphire laser amplifier operated along the single path of the oscillator beam were investigated and analyzed. In the case of the oscillator, we measured the spectrum, the pulse buildup time, the temporal duration time of the pulse, and the output energy according to the variation of the pumping energy, resonator length, and the reflectance of the output coupler. And, in the case of the amplifier, we investigated and analyzed the output energy of the amplifier as a function of the time difference between the two pump beams of the oscillator and the amplifier, the pumping energy of the oscillator, and the pumping energy of the amplifier When pump energies of both the oscillator and the amplifier were 18 mJ/pulse, we could find that the output energy of the amplifier increased linearly and gradually up to the time difference of 35 ns. Finally, we determined that the slope efficiencies of the oscillator and the amplifier were 23.5 % and 11.6 %, respectively.

• Korean Journal of Optics and Photonics
• /
• v.8 no.1
• /
• pp.58-62
• /
• 1997

A new, simple lasing loop configuration employing a fiber grating was proposed and demonstrated for all-optical gain control of erbium-doped fiber amplifier. The lasing loop was designed such that the fiber grating acts as a notch filter to cutoff the lasing light as well as selects the lasing wavelength. The operating gain was clamped to the same level as the loop loss and it could be varied with a tunable directional coupler in the loop. It is believed that this type of gain-controlled erbiumdoped fiber amplifier can have several advantages when used in wavelength-division-multiplexed transmission systems.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.8
• /
• pp.1847-1853
• /
• 2014

The PAPR of the input signal is increased due to OFDMA signal in a mobile communication system. High efficiency of a power amplifier, which accounts for power consumption, is a very important key technology. Digital Pre-Distortion techniques were used to improve the linearity of the power amplifier. The Asymmetric Doherty scheme was used to improve the efficiency of the power amplifier. In this paper, we propose a new structure of Asymmetric Doherty. Drive power amplifier part is separated as main path and peak path, and phase shifter is employed to improve power combine characteristics of the Doherty Amplifier. Also, envelope tracking technology for drive gate bais in drive peak amplifier is used to improve efficiency.

• Journal of Navigation and Port Research
• /
• v.27 no.2
• /
• pp.209-215
• /
• 2003

In this paper. We tested and fabricated the error amplifier for the 15 Watt linear power amplifier for the IMT-2000 baseband station. The error amplifier was comprised of subtractor for detecting intermodulation distortion, variable attenuator for control amplitude, variable phase shifter for control phase, low power amplifier and high power amplifier. This component was designed on the RO4350 substrate and integrated the aluminum case with active biasing circuit. For suppression of spurious, the through capacitance was used. The characteristics of error amplifier measured up to 45 dB gain, $\pm$0.66 dB gain flatness and -15 dB input return loss. Results of application to the 15 Watt feedforward Linear Power Amplifier, the error amplifier improved with 27 dB cancellation from 34 dBc to 61 dBc IM$_3$.