• The Magazine of the IEIE
• /
• v.29 no.4
• /
• pp.39-47
• /
• 2002

기존의 아날로그 통신 방법이 디지털 통신 시스템으로 바뀌면서 신호 전송방법에 많은 변화를 일으키고 있다. 특히 이동통신 기기 중에서 통신 품질과 장비의 효율을 결정하는 고출력 전력증폭기는 기존의 전력증폭기에 비하여 더욱더 많은 기술들이 요구되어지고 있다. 본 고에서는 이러한 고출력 증폭기의 고유한 특성들과 이를 보상할 수 있는 선형화기술들에 관하여 고찰하고 이러한 기술의 동향에 관하여 살펴보았다.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.38 no.1
• /
• pp.20-26
• /
• 2001

Predistorter linearizer having small size and good efficiency is frequently used in High Power Amplifier linearizer system. In this paper, the amount of IMD signal cancellation according to amplitude and phase of predistorter in predistorter type lincarizer is investigated by new experiment method. In the combining method of predistorter type, IMD signal is combined at the amplifier input port, the magnitude and phase of combining signals cannot be easily expected due to different magnitude and phase of incoming signals. By experiment, it is measured that Predistorter linearizer has lower amount of lMD signal cancellation than thoce of Feedforward linearizer at the same condition (amplitude and phase).

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.40 no.1
• /
• pp.24-36
• /
• 2003

The digital mobile communication will be developed till getting multimedia service in anyone, any where, any time. Theses requiring items are going to be come true via IMT-2000 system. Transmitting signal bandwidth of IMT-2000 system is 3 times as large as IS-95 system. That is mean peak to average of signal is higher than IS-95A system. So we have to design it carefully not to effect in adjacent channel. HPA(High Power Amplifier) located in the end point of system is operated in 1-㏈ compression point(Pl㏈), then it generates 3rd and 5th inter modulation signals. Theses signals affect at adjacent channel and RF signal is distorted by compressed signal which is operated near by Pl㏈ point. Then the most important design factor is how we make HPA having high linearity. Feedback, Pre-distorter and Feed-forward methods are presented to solve theses problems. Feed-forward of these methods is having excellent improving capacity, but composed with complex structure. Generally, Linearity and Efficiency in power amplifier operate in the contrary, then it is difficult for us to find optimal operating point. In this paper we applied algorithm which searches optimal point of linear characteristics, which is key in Power Amplifier, using minimum current point of error amplifier in 1st loop. And we made 2nd loop compose with new structure. We confirmed fabricated LPA is operated by having high linearity and minimum current condition with ACPR of -26 ㏈m max. @ 30㎑ BW in 3.515㎒ and ACLR of 48 ㏈c max@${\pm}$㎒ from 1W to 40W.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.179-182
• /
• 1999

전력 증폭기의 3차나 5차 비선형성은 인접 통신 채널에 직접적인 영향을 미치므로 선형화 기법을 이용하여 출력단의 혼변조 신호를 감쇄시켜야 한다. 본 논문에서는 전력 증폭기의 입력 신호를 기저대역에서 왜곡시켜 전력 증폭기를 선형화 시키는 디지털 사전 왜곡기를 구현하였다. 측정에 앞서, 모의실험을 통하여 시스템 변수에 따른 선형화기의 성능을 예측하고, 1차원 참조표(look-up table)를 사용한 사전 왜곡기의 측정 결과, 약 9 dB의 ACPR 개선 효과를 얻을 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.12
• /
• pp.1289-1295
• /
• 2012

An adaptive digital predistortion (PD) technique is proposed for linearization of power amplifiers (PAs) in multiple-input multiple-output (MIMO) transmitters. We consider a PD structure equipped with only one combined feedback path while conventional systems have multiple feedback paths. Hence, the proposed structure is much simpler than that of multiple feedback paths. Based on the structure, a new PD algorithm is derived. The simulation results show that linearization performance of the proposed method is almost the same as the conventional multiple feedback technique while the former is much simpler to implement than the latter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.2
• /
• pp.146-154
• /
• 2002

This paper presents a linearization technique up to the saturation region of power amplifiers. The predistorter gain polynomials which have optimum coefficients are introduced. Power amplifiers are most efficient when operated near the saturation region. Compensating the amplifier nonlinearities with these predistorter gain polynomials, the efficiency of the amplifier can be maximized. Simulation results demonstrate that the adjacent channel power ratio (ACPR) is improves by about 63 ㏈ at the band edge. The convergence and reconvergence characteristics of the linearizer are also satisfactory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.05a
• /
• pp.681-684
• /
• 2015

Power amplifier is an essential component for transmitting signals to a remote receiver in wireless communication systems. Power amplifier is a non-linear device in general, and the nonlinear distortion becomes severer as the output power increases. The nonlinearity results in spectral regrowth, which leads to adjacent channel interference, and decreases the transmit signal quality. To linearize power amplifiers, many techniques have been developed so far. Among the techniques, digital pre-distortion is known as the most cost and performance effective technique. However, the linearization performance falls down abruptly when the power amplifier operates in its saturation region. This is because of the severe nonlinearity. To relieve this problem, this paper proposes a new adaptive predistortion technique. The proposed technique controls the adaptive algorithm based on the power amplifier input level. Specifically, for small signals, the adaptive predistortion algorithm works normally. On the contrary, for large signals, the adaptive algorithm stops until small signals occur again. By doing this, wrong coefficient update by severe nonlinearity can be avoided. Computer simulation results show that the proposed method can improve the linearization performance compared with the conventional digital predistortion algorithms.

• The Journal of the Acoustical Society of Korea
• /
• v.23 no.4
• /
• pp.303-308
• /
• 2004

In this Paper a transmitter system for IMr-2000 using feed-forward linearization method was Proposed to linearize power amplifier. The feed-forward structure needs a reference signal to compare and neutralize distortion : this is achieved through the second modulator which is operated at very low input level to obtain a signal with a negligible distortion. Therefore, this structure can reduce distortion of modulator as well as Power amplifier. This is the advantage over the existing system structure. The Proposed transmitter system is designed and simulated by Agilent ADS ver.2002. A two tone test for the system is done at 1.98GHz center frequency with frequency spacing of 2MHz. The reduction of Inter-Modulation Distortion(IMD) is around 49.95dB. This proposed system offers an excellent combination of linearity and simplicity.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.7 no.4
• /
• pp.76-85
• /
• 2008

In this paper, a 800 MHz 1 W cartesian feedback linearized power amplifier is designed and fabricated for TETRA handset application. For amplification of TETRA signal with 200 kHz narrow bandwidth, amplifier linearization performance of more than 30 dBc is improved through the cartesian feedback linearizer at the offset Sequency of ${\pm}25$ kHz. It is clear that the linearization performance is affected by imbalance of gain and phase between I/Q signals and also DC offset. The linearization performance can be maximized by the compensation of those influences. Cartesian feedback is suitable for a liearization technique of narrow band signal with QAM and another modulation signals, as well.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.2
• /
• pp.127-133
• /
• 2004

A feedforward amplifier, which is composed of several components, is an open loop system. Therefore, feedforward amplifiers are apt to deteriorate its performance according to the environmental changes even though the cancellation performance and the linearization bandwidth of feedforward systems are superior to other linearization methods. A control method is needed for maintaining the original performance of feedforward amplifiers or to keep the desired performance within a little error bounds. In this paper, an adaptive control method using the steepest descent algorithm, which has a good convergence characteristic and is easy to implement, is suggested. The characteristics of the suggested control method compare with the characteristics of other control methods and the simulation results are presented.