Linear Amplification With Nonlinear Components System Research Articles

Design of high efficient 3-level LINC transmitter using a 9-point finite difference method

An efficiency of linear amplification with nonlinear components (LINC) system is degraded due to the low efficiency of a power combiner for high peak-to-average power ratio signals such as long-term evolution signal. A multi-level LINC system can be used to improve the performance of the conventional LINC system. In this paper, a novel 9-point finite difference method to determine the optimal threshold values for 3-level LINC system is suggested. Instead of solving the complicated differential equation, the proposed method can extract optimal threshold values efficiently by numerical method. The 3-level LINC system adopting the proposed scheme and dynamic biasing significantly improves the power efficiency and linear performance simultaneously. The proposed system is verified by comparing the performance of the 3-level system with those of the conventional and 2-level LINC systems.

Mismatch Detection and Compensation Method for the LINC System Using a Closed-Form Expression

This paper proposes a simple and straightforward path mismatch detection method with a closed-form expression for linear amplification with nonlinear components (LINC) system implementation. In this work, a test vector signal set with three phase differences and one amplitude difference is employed to detect the amplitude and phase mismatches at the same time. The proposed method can predict the exact mismatch value without any iterations, because the mismatch value has a unique solution with a closed-form expression with the proposed test signal set. Moreover, the sensitivity of the proposed method to the measurement noise is also analyzed for practical implementation of LINC system. The LINC system is realized with the proposed mismatch detection method and the performance is evaluated with a IEEE 802.16 WiMAX signal, which has 7 MHz channel bandwidth and 16-QAM. The error vector magnitude (EVM) of -37.4 dB is obtained through performance testing, which meets the performance requirement of -24 dB EVM. The proposed mismatch detection method is validated to improve the LINC system performance.

LINC 시스템 구현을 위한 닫힌 해를 갖는 크기 위상 오차 검출 기법

본 논문에서는 linear amplification with nonlinear components(LINC) 시스템의 두 신호 경로에 발생하는 크기와 위상 오차를 자동으로 검출하여 보상하는 알고리즘을 제안하였다. LINC 시스템은 첨두 대 평균 전력비가 큰 non-constant envelop 신호를 constant envelop 신호로 바꿔주어 고효율 전력 증폭기를 사용할 수 있는 장점이 있다. 그러나 LINC 시스템은 두 전력 증폭기의 경호에서 발생하는 매우 작은 경로 오차에 민감하게 성능이 열화된다는 단점이 있다. 본 논문에서는 4개의 테스트 신호를 이용하여 두 경로의 크기와 위상 오차를 검출하는 알고리즘을 제안하였다. 제안된 오차 검출 기법은 닫힌 해(closed form solution)를 가지며, 반복 계산이 필요하지 않아, 빠르고 효율적으로 오차를 검출할 수 있다. 본 논문에서는 제안된 기법을 적용하여 오차 검출과 검출된 결과를 반영하여 신호의 왜곡을 보상하는 digital-IF 형태를 갖는 LINC 시스템을 구현하였다. 구현된 LINC 시스템은 7 MHz 채널 대역을 갖고 16-QAM으로 변조된 IEEE 802.16 WiMAx 기저 대역 신호를 이용하여 성능을 분석하였으며, 제안된 기법을 이용하여 EVM이 -37.37 dB까지 개선되었으며, 이로서 LINC 시스템 구현시 제안된 오차 검출 및 보상 기법의 적용 타당성을 확인하였다. This parer proposed the path mismatch detection and compensation algorithm with closed form for linear amplification with non-linear components(LINC) system implementation. The LINC system has a merit of using the high efficient amplifier by transferring the non-constant envelop signal which is high peak to average signal ratio into constant envelop signal. However, the performance degradation is very sensitive to the path mismatch such as an amplitude mismatch and a phase mismatch. In order to improve the path mismatch, the error detection and compensation method is introduced by the use of four test signals. Since the presented method has the closed form solution, the efficient and fast detection is available. The digital-IF structure of LINC system applied by the proposed error detection and compensation algorithm was implemented. The performance was evaluated with the IEEE 802.16 WiMAX baseband sinal which has 7 MHz channel bandwidth and 16-QAM. The Error Vector Magnitude(EVM) of -37.37 dB was obtained through performance test, which meets performance requirement of -24 dB EVM. As a result, the introduced error detection and compensation method was verified to improve the LINC system performance.

Power Amplifier Selection for LINC Applications

Linear amplification with nonlinear components (LINC) using a nonisolating combiner has the potential for high efficiency and good linearity. In past work, the interaction between two power amplifiers has been interpreted as a time-varying load presented at the output of amplifiers, and the linearity and efficiency of the LINC system has been evaluated according to how the power amplifiers respond to the time-varying load. In this paper, it is shown that power amplifiers in LINC are more directly affected by their common output current. Time-varying load is just a result of the interaction. A new approach to analyze the behavior of power amplifiers in a LINC system is introduced in which the amplifier output current-voltage relationship can be used to predict how well a particular type of amplifier will perform in this configuration. Complete analysis and comparison between different types of power amplifiers are presented

Integrated antenna for LINC systems

AbstractThis letter presents a novel concept of integrated antenna for LINC (linear amplification with nonlinear components) systems. In this approach, the power combiner involved in the conventional LINC system is removed, and the power combination is realized within a microstrip antenna. This is a significant advance on current LINC systems, where the circuit‐level power combiner losses degrade overall efficiency. The configuration of the integrated antenna is described and an example antenna is designed at 2.0 GHz. The simulated results based on moment method which validate the concept, are presented. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 93–95, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10240

Gain/phase imbalance-minimization techniques for LINC transmitters

Two simple calibration schemes for the correction of the path imbalance in a linear amplification with nonlinear components (LINC) transmitter have been demonstrated. In the foreground algorithm, a baseband digital signal processor (DSP) evaluates the gain and phase imbalance with a set of calibration signals, while in the background algorithm, the imbalance is characterized by exchanging the two LINC vector components. In both cases, the compensation of the path imbalance is accomplished within the DSP by introducing a predistortion term. A prototype LINC system has been tested for CDMA IS-95 baseband input, and -38 and -35-dBc adjacent channel interference were achieved for the foreground and background schemes, respectively. The quadrature errors of the in-phase/quadrature modulators set a limit on the overall performance of both algorithms.