In this paper, the design of a broadband, high-efficiency, and high-linearity Class-J GaN HEMT RF power amplifier (PA) over 1.6-2.6 GHz is explained. The source impedance is conjugatematched to the input impedance of the device resulted from small signal simulation to make a high-gain power amplifier. The load impedance related to the maximum power added efficiency (PAE) and maximum output power is obtained by pulling the only fundamental and second harmonic components over frequency bandwidth. Thus, not only a high-efficiency PA but also a high-linearity PA is formed. The input and output matching networks are implemented by microstrip transmission lines. The theoretical PA designed is optimized using computer-aided simulations. The fabricated PA provides output power in the range of 38-39.9 dBm with 60%-73% PAE and 15-16.3 dB power gain across the band. The worst measured ACLR1 as the PA is fed by the CDMA signal with 1.2288 MHz bandwidth is at a level of −38.6 dBc. A close agreement between the measured and simulation results is observed due to the use of high-order harmonic balance simulator and high-accuracy implementation procedure.
Abstract:Modern day cellular networks are driven by the need to provide ubiquitous connectivity with very high spectral efficiency to both indoor and outdoor users, hence the need to deploy small cells over conventional macrocells in a Heterogeneous Network (Hetnet) deployment. To alleviate the resulting inter-cell and cross-tier interference, effective intercell interference coordination (ICIC) schemes such as Fractional Frequency Reuse (FFR) are employed, and have been widely studied in perfect geometry network scenarios which are too idealistic and not easily adaptable to the complexity of Hetnets. This work provides an analytical framework for the performance of such FFR schemes in Hetnets with antenna sectorization employed at the macro tier, by leveraging stochastic geometry tools to model base station locations of both macro and femto tiers using the Poisson Point Process (PPP). We study the effects of varying system parameters and consider cross-tier femto interference commonly ignored in many analytical works in literature. Furthermore, the femtocells employ a sensing algorithm to minimize spectrum sharing with macro users in close proximity, especially at the transition areas of center and edge region where cross-tier interference could be monumental. Numerical simulations are used to evaluate performance of the proposed framework in terms of coverage probability and average user rate, and results are compared with traditional FFR schemes and the No-FFR deployment. To the best of the author's knowledge, this is the first analytical framework characterizing sectored-FFR schemes using stochastic geometry tools in Hetnets.
This paper demonstrates a systematic approach for the design of broadband, high efficiency, high power, Class-AB RF amplifiers with high gain flatness. It is usually difficult to simultaneously achieve a high gain flatness and high efficiency in a broadband RF power amplifier, especially in a high power design. As a result, the use of a computer-aided simulation is most often the best way to achieve these goals; however, an appropriate initial value and a systematic approach are necessary for the simulation results to rapidly converge. These objectives can be accomplished with a minimum of trial and error through the following techniques. First, signal gain variations are reduced over a wide bandwidth using a proper pre-matching network. Then, the source and load impedances are satisfactorily obtained from small-signal and load-pull simulations, respectively. Finally, two highorder Chebyshev low-pass filters are employed to provide optimum input and output impedance matching networks over a bandwidth of 100 MHz-500 MHz. By using an EM simulation for the substrate, the simulation results were observed to be in close agreement with the measured results.Keywords: Broadband, Class-AB, Matching network, Power amplifier. Manuscript received June 28, 2016; revised Oct. 7, 2016; accepted Oct. 17, 2016. Seyed Alireza Mohadeskasaei (corresponding author, alireza.kasaee@gmail.com), Jianwei An (ajw626@126.com), Yueyun Chen (chenyy@ustb.edu.cn), Zhi Li (lizhi870218@gmail. com), Sani Umar Abdullahi (umarsani@gmail.com), and Tie Sun (suntie1605@163.com) are with the Department of Communication, School of Computer and Communication, University of Science and Technology Beijing, China. This is an Open Access article distributed under the term of Korea Open Government License (KOGL) Type 4: Source Indiction + Commercial Use Prohibition + Change Prohibition (http://www.kogl.or.kr/news/dataFileDown.do?dataIdx=71&dataFileIdx=2). I. IntroductionPower amplifiers (PAs) are one of the most significant ingredients of many communication systems. Four important requirements, namely, the efficiency, linearity, low noise, and broadband frequency response, must be considered when designing PAs [1]- [3]. For broadband power amplifiers, one of the most difficult challenges lies in determining how to achieve a high signal gain and high power level while maintaining a low power dissipation. In other words, how to achieve high efficiency. At the same time, gain variation throughout the band causes more challenges for modern signal modulation techniques, such as quadrature amplitude modulation.In wideband applications, linear classes, such as Class-A, Class-B, and Class-AB, are widely employed because they provide appropriate bandwidths and acceptable signal gains [4]- [5], but their efficiency is not as high as that of harmonictuned classes, such as Class-E and Class-F [6]- [7]. Various aspects resulting from recent research on broadband PAs are summarized in Table 1. According to this table, a Class-F PA exhibits a high power-added efficiency (P...
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