• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.295-302
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• 2014

OFDM technique uses multiple sub-carriers for the data transmission. Therefore, inter carrier interference is generated because of nonlinear high power amplifier and carrier frequency offset. Wireless OFDM transmission over Doppler fading channels also causes inter carrier interference. The interference increases the bit error rate in receiver. Sub-carrier allocation methods in LTE and WiMAX standards are different. The performance of OFDM systems using different sub-carrier allocation, gauged by the bit error rate, is analyzed considering the nonlinear high power amplifier, carrier frequency offset and Doppler fading channels.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.185-191
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• 2018

In this paper, an improved Norton amplifier is proposed and the problems caused by the current input in the Norton amplifier, which has advantages in current transmission, are analyzed. The output of the voltage follower consisting of an operational-amplifier with constant output voltage characteristics is used as an input terminal of the proposed circuit. It is configured to detect the power supply current passing through the voltage follower and extract the current from the input terminal. The performance of the improved Norton amplifier is verified at experiment according to the input current. The results are compared with conventional Norton amplifier. Consequently, the input offset voltage, which is a problem in the conventional Norton amplifier, was removed in the proposed circuit. In addition, the average error of the output voltage with respect to the input current was reduced to 4.755%. It is verified that the characteristics of the proposed circuit are improved.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.868-871
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• 2005

In this article, presents an analog multiplier using a general-purpose operational amplifier (opamp). The realization method is based on the quarter-square technique, which utilize the square-law characteristic of the class AB output stage of the opamp. The experimental results verifying the proposed multiplier performances are also included. The linearity error and the total harmonic distortion is about 0.8% and 1.6%, respectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.13-21
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• 1998

In this paper, we analyze the main-carrier cancellation characteristics of the nulling loop control circuit which is used for the main-carrier cancellation circuit of the feedforward linear power amplifier. A new nulling loop error control method is proposed to improve the linear power amplifier characteristics. With this analysis, the main carrier cancellation ratio can be estimated and the required specifications of the main and auxiliary amplifiers can be optimized for the economic and power efficiency.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.87-90
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• 2003

In this paper, A feedforward linear power amplifier is analyzed for imperfect signal cancellation and negative feedback for basestaion of IMT2000 band. the distortion generatied by the error amplifier is reduced using an imperfect signal cancellation for a 1-carrier WCDMA source by 4.3dB at 2.5MHz offset and 6dB at 5MHz offset of IMSR(intermodulation signal power ratio) compared to a perfect signal cancellation system. additionally, An imperfect signal cancellation using negative feedback improved 1.3dB and 8.2dB at 2.5MHz and 5MHz offset of IMSR compared to an imperfect signal cancellation.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.563-566
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• 1988

A current-controlled CMOS operational transconductance amplifier(OTA), whose transconductance is directly proportional to the DC bias current, has been developed for many electronic circuit applications. It features that its transconductance is insensitive to temperature unlike that of the bipolar OTA. This property makes it possible to use the proposed OTA as a basic buliding block in electrically variable circuit design. The SPICE simulation shows that the conversion sensitivity of the circuit is 44.62 mv /${\mu}A$ and the linearity error less than 0.54 % over a bias current range from 2 ${\mu}A$ to 120 ${\mu}A$ when the output is loaded with a 1${\Omega}$ resistor.

• ETRI Journal
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• v.26 no.1
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• pp.57-60
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• 2004

We propose an inductive compensation method for a surface-mountable 10 Gbps photoreceiver module. Since many typical 10 Gbps photoreceiver modules consist of a photodetector and low-noise pre-amplifier, the impedance mismatch between the photodetector and pre-amplifier, as well as package parasitics, may reduce the frequency bandwidth. In this paper, we inserted an inductive component between the photodetector and pre-amplifier in order to create frequency bandwidth expansion. From the measurement results, we have found that the proposed technique can increase the -3 dB bandwidth about 4.2 GHz wider compared with an uncompensated module. And, from a bit-error rate (BER) test, we observed -15.7 dB sensitivity at $10^{-12}$ BER. This inductive compensation can be implemented easily and is compatible with common manufacturing processes of photoreceiver modules.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.389-391
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• 2011

This paper has been studied about design of linear 25Watt Power amplifier for VDR(VHF Data Radio). VDR's frequency band is 117.975~137MHz, and CSMA(Carrier Sense Multiple Access), D8PSK(Differential Eight Phase Shift Keyed), 25KHz's channel bandwidth use. It also stated in DO-281A MOPS output power, symbol constellation error, spurious emissions, adjacent channel power must be met. HPA is designed to meet DO-281A standard.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.118-123
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• 2001

For multi-carrier communication system, power amplifier generate intermodulation products caused by their nonlinear characteristics. Intermodulation products arised around the carrier frequency cannot be filtered out, operate as noise source for tile adjacent channel and thus degrades the quality of communication. In this paper, the 1850MHz-band RF linear power amplifier has been designed and fabricated with feedforward loop. The error signal loop consists of several key components such as phase shifter and attenuator, subtracter. The proposed Linearizer was tested with two-tone signals separated 10MHz apart at the center frequency of 1850MHz. The experimental results show C/I improvement by 14.5${\~}$20dB over 15dB dynamic range(33${\~}$47.8dBm) which gave IMD of 53.25${\~}$59dBc for the designed LPA.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.11
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• pp.41-47
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• 2011

A novel digital instrumentation amplifier(DIA) converting universal signal inputs into 5V voltage-output for industry standard sensor signal processing was designed. The circuit consists of a commercial instrumentation amplifier, seven analog switches, two voltage references of 1.0V and -10.0V, and four resistors. The converting principle is the circuit reconstruction by switches for resistor values and reference voltages according to input signals. The simulation result shows that the DIA has a good output voltage characteristics of 0~5V for the input voltage of 0V~5V, 1V~5V, -10V~+10V, and 4mA~20mA. The nonlinearity error was less than 0.1% for the four type signal inputs.