• Current Optics and Photonics
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• v.7 no.1
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• pp.33-37
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• 2023

Real-time adaptive control of laser output polarization is presented in a 10-W-level non-polarization-maintaining (non-PM) fiber amplifier. While the output polarization from a non-PM fiber amplifier tends to be irregular, depending on output power, time, and perturbation, closed-loop polarization control can maintain the polarization extinction ratio at higher than 20 dB. Real-time polarization control can attain the target linear polarization mostly within 1.4-25 ms and shows stability against external perturbations. This approach can satisfy both linear polarization and high output power in a non-PM amplifier, and facilitates optimization of laser performance and maintenance-free operation.

• ETRI Journal
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• v.33 no.5
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• pp.679-688
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• 2011

A new discrete-amplitude pulse width modulation (DAPWM) scheme for a high-efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low-frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching-mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.

• ETRI Journal
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• v.30 no.1
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• pp.158-160
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• 2008

A highly linear and efficient GaN HEMT Doherty amplifier for wideband code division multiple access (WCDMA) repeaters is presented. For better performance, the adaptive gate bias control of the peaking amplifier using the power tracking circuit and the shunt capacitors is employed. The measured one-carrier WCDMA results show an adjacent channel leakage ratio of -43.2 dBc at ${\pm}2.5$-MHz offset with a power added efficiency of 40.1% at an average output power of 37 dBm, which is a 7.5 dB back-off power from the saturated output power.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.9
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• pp.39-46
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• 2007

This paper presents a programmable single-phase ac power source that provides a sinusoidal output voltage with an adjustable output amplitude and frequency over a wide range as well as an arbitrary waveform. The ac power source under consideration have a linear power amplifier. The desired output values can be programmed with a personal computer. The power source operates at 220[V]/60[Hz] mains and the output voltage is isolated from the input circuit. The system consists mainly of a power converter to generate and amplify the waveform signal, a controller to control the desired output signal and measure the output parameters, and a control program to set the desired output and display the values. The prototype ac power source was constructed and tested with the results demonstrating a good performance.

• 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.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.81-86
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• 2005

In this paper, the high linear Doherty amplifier has been realized by employing the PBG(Photonic Band Gap) structure. The PBG structure has been employed on the output matching network of the power amplifier. The proposed Doherty amplifier has been improved in PAE and IMD. The PAE has been $36.4\%$ and the IMD has been -24.5 dBc, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.538-545
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• 2006

In this paper, an asymmetric high power extended Doherty amplifier for WCDMA base-station applications is presented. The amplifier has an extended peak efficiency over 9 dB of output power and a linear dynamic range characteristic. To realize the peak efficiency extension and linear dynamic range characteristic, a two times larger peaking device compared to the main device, and an unequal power divider are used. From the experimental results of 1FA WCDMA signal, this amplifier has an efficiency of 31 % and an ACLR of -35 dBc is achieved at 9 dB back-off from P1 dB.

• Journal of Navigation and Port Research
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• v.26 no.3
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• pp.295-302
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• 2002

Currently digital communication system adapt various digital modulation schemes. All these communication systems are required to cause the minimum interference to adjacent channels, they must therefore employ the linear power amplifiers. In respect to linear power amplifiers, there are many linearization techniques. Feedforward power amplifier represent very wide bandwidth and high linearization capability. In the feedforward systems overall efficiency is reduced due to the loss of delay line. In this paper, delay filter instead of transmission delay line adapted to get more high efficiency. Experimental results showed that ACLR has improved 17.04dB which is added 2.54dB by using the delay filter.

• ETRI Journal
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• v.19 no.2
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• pp.35-47
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• 1997

A power amplifier operating at 3.3 V has been developed for CDMA/AMPS dual-mode cellular phones. It consists of linear GaAs power MESFET's, a new gate bias control circuit, and an output matching circuit which prevents the drain terminal of the second MESF from generating the harmonics. The relationship between the intermodulation distortion and the spectral regrowth of the power amplifier has been investigated with gate bias by using the two-tone test method and the adjacent channel leakage power ratio (ACPR) method of CDMA signals. The dissipation power of the power amplifier with a gate bias control circuit is minimized to below 1000 mW in the range of the low power levels while satisfying the ACPR of less than -26 dBc for CDMA mode. The ACPR of the power amplifier is measured to be -33 dBc at a high output power of 26 dBm.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.4
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• pp.42-51
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• 2003

In this paper, we are going to analyze on relation of an output spectrum along phase distortion of power amplifier in wireless LAN system, and then considered an ACPR characteristic of power amplifier and consideration of an OFDM method for this. Also, we did implementation for OFDM modulation and transmission section of an IEEE 802.11a standard to have transmission speed of the maximum 54Mbps in order to know an OFDM modulation method and relation of non-linear characteristic of power amplifier. The non-linear characteristic of power amplifier did modeling with AM-to-AM and AM-to-PM, and we analyzed an output spectrum characteristic along phase distortion composed input signal supply for power amplifier. When output spectrum analysis results phase distortion increased, and an AM-to-PM characteristic of power amplifier in 5 degrees, the output spectrum was satisfied with a demand spectrum in P1 dB, but 10-20 degrees were able to confirm what cannot be satisfied with a demand spectrum in phase distortion. Also, an output spectrum of power amplifier by frequency re-growth generated by a non-linear characteristic of power amplifier did not satisfied in P1dE. therefore, a back-off value was requested according to an AM-to-PM distortion degree, and smaller back-off value were able to know what demand became in case of modulation section that used OFDM.