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Power amplifiers (PAs) are inherently nonlinear elements and digital predistortion is a highly cost-effective approach to linearize them. Although most existing architectures assume that the PA has a memoryless nonlinearity, memory effects of the PAs in many applications ,such as wideband code-division multiple access (WCDMA) or orthogonal frequenc...
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Context 1
... summary of utilized resources for implementing our proposed predistorter is presented in Table 2. As it can be seen in Table 2, the proposed predistorter consumes fewer resources than the predistorter in [23]. ...
Context 2
... summary of utilized resources for implementing our proposed predistorter is presented in Table 2. As it can be seen in Table 2, the proposed predistorter consumes fewer resources than the predistorter in [23]. Not only the proposed design does not need any BRAM block, but also it needs 40% less DSP48 instances than the previous one. ...
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Citations
... Dimana Masukan struktur Hammerstein, x(k) adalah input model linear dan y(k) adalah model linear yang menjadi output struktur Hammerstein. Pemodelan Hammerstein dapat digambarkan pada Gambar 3 [9] : ...
Abstrak: Teknik OFDM mempunyai kelemahan, salah satunya adalah tingginya PAPR yang akan menyebabkan distorsi non-linear pada Power Amplifier (PA), dikarenakan PA membatasi keluaran dengan nilai tertentu yang dapat mengurangi efisiensi daya amplifier. Dalam mengatasi masalah tersebut maka diperlukan teknik reduksi PAPR. Untuk teknik reduksi PAPR efisien yang digunakan adalah Selective Mapping (SLM). Teknik Reduksi PAPR SLM sendiri tidak dapat untuk memperbaiki daerah non-linear pada Power Amplifier, oleh karena itu diterapkan teknik pemodelan HPA Predistorsi untuk meningkatkan efisiensi dari PA dengan memperluas jangkauan linear dan mencegah sinyal jatuh ke wilayah saturasi PA. Untuk pemodelan HPA yang digunakan yaitu pemodelan Hammerstein. Model Hammerstein ini sederhana namun efektif untuk menggambarkan kinerja PA dan kinerja predistorter non-linear akan berlawanan dengan PA dengan menggunakan efek memori. Hasil kerja dari teknik gabungan tersebut dapat dianalisa berdasakan kurva BER dan kurva CCDF yang dihasilkan. Performansi BER dapat diperbaiki ketika menggunakan teknik reduksi SLM yang dikombinasikan dengan teknik predistorsi, dimana pada nilai SNR sebesar 15 dB sudah mampu mengatasi probabilitas BER. Namun, ketika tanpa teknik predistorsi baru bisa mengatasi probabilitas BER pada nilai SNR sebesar 22 dB. Untuk teknik reduksi SLM dan teknik predistorsi dengan subblok 16 mampu menghasilkan nilai lebih baik daripada saat menggunakan subblok 4 dan 8 yaitu dapat mencapai probabilitas BER hingga 10-6 dengan nilai SNR 14 dB, dan sudah dapat mengatasi probabilitas BER pada SNR 15 dB. Dengan teknik predistorsi ini mampu meningkatkan linearisasi pada PA. Sehingga dapat dibuktikan untuk dapat melewati HPA, sinyal dengan reduksi menggunakan subblok 4 sudah dapat melewati HPA yang mempunyai linearisasi tinggi.
... Various linearization procedures, such as predistortion, feedforward, and feedback methods, are thus employed to enhance the linearity of nonlinear power amplifiers and transmitters. Among these approaches, one of the most cost-effective and promising is the predistortion technique [1]. Predistortion is accomplished by finding the transfer function of the power amplifier, G, and modulating the incoming signal by F = G −1 , such that the output of the power amplifier when applying the predistorted signal becomes linear (Fig. 1). ...
... The digital predistortion approach is commonly applied in modern communication systems to linearize transmitters and power amplifiers [1,[9][10][11][12][13]. Due to its digital hardware implementation, flexible structure, and very low cost, digital predistortion is one of the most promising methods for transmitter linearization. ...
A high-performance model with a gravitational search algorithm (GSA)-based generalized parallel two-box (GPTB) structure is suggested for digital predistortion in modern transmitters exhibiting memory effects, where the GSA is applied to identify the minimum dimension for the GPTB model. An indirect learning structure in conjunction with the GSA method is employed to identify the coefficients of the GSA-based GPTB model. The GPTB–GSA method is verified using simulations of a transmitter excited by quadrature amplitude modulation (QAM) signals in ADS software and simulations of the GSA in MATLAB software. The MATLAB results demonstrate the ability of the GSA to determine the dimension of the GPTB model efficiently. Also, the adjacent channel power ratio (ACPR) measure is decreased by about 16 dB according to the simulation. The proposed model and algorithm can reduce the number of coefficients by approximately 25% in comparison with the memory polynomial model.
... For this reason, several linearization techniques, such as feedback, feedforward, and predistortion, have been proposed to improve the linearity of the transmitter and the power amplifier without sacrificing efficiency [26]. The predistortion method has suitable performance and low cost among the linearization techniques [2]. Figure 1 shows the conceptual diagram of the predistortion linearization process. ...
... As a result, the relationship between the input and output of the system will be linear. The predistortion can be classified into two types in accordance with the techniques used: (1) analog predistortion (APD) (2) digital predistortion (DPD). ...
... For example, Seo proposed an analog predistorter based on a Schottky diode, but the improvement in the adjacent channel power ratio is very small [30]. One of the linearization procedures commonly utilized in advanced communication systems is the digital predistortion method [2,9,12,15,26,35]. ...
This paper presents a generalized parallel two-box structure that is proposed for modeling and digital predistortion of power amplifiers and wireless transmitters exhibiting memory effects. The proposed predistortion scheme consists of two separable boxes; the first is utilized to model the static behavior of the power amplifier, while the second is proposed to consider the memory effect and nonlinear distortion of the power amplifier. The coefficients of the proposed model are identified by applying an indirect learning structure and a least square method. The validation of the proposed model is carried out using the simulation of the power amplifier and the digital predistortion excited by a 64QAM signal in the advanced design system software. According to the simulation results, the criterion of adjacent channel power ratio reduced by about 16 dB. The simulation results reveal an adjacent channel power ratio of almost − 48 dB. Indeed, the proposed model leads to a better performance in terms of spectral regrowth in comparison with the memory polynomial model, and it also reduces the number of coefficients by approximately 22%. This proposed model enables a more accurate modeling of nonlinear distortion and memory effects compared to previous linearization methods.
... According to the designed Wiener model for the power amplifier, the characteristic of the proposed predistorter must be totally the opposite of the behavior of the modeled power amplifier. The proposed predistorter model is the Hammerstein structure consisting of the memoryless nonlinear block and the linear filter (Fig. 2) [39]. The part of the linear filter in the predistorter model must be fully the reverse of the filter in the Wiener model. ...
In this paper, a novel digital predistorter design based on the Hammerstein structure is proposed in order to linearize radio frequency power amplifiers. A genetic algorithm optimization method has been proposed to accurately identify the coefficients of a Wiener model for the power amplifier. Digital predistorter design based on the proposed Hammerstein model has been carried out according to the accurate Wiener model. The validation of the suggested model is carried out using the simulation of the power amplifier and the digital predistortion excited by 64QAM signals in the advanced design system software. According to the simulation results, the criterion of an adjacent channel power ratio decreased by about 16 dB. The simulation results show the adjacent channel power ratio of almost − 46 dBc. In order to assess the feasibility of the proposed predistorter, it is completely implemented in the Kintex FPGA using Vivado HLS. This proposed model enables a more accurate modeling of nonlinear distortion and memory effects compared to the previous linearization methods. This paper presents the new linearization method using the genetic algorithm based Hammerstein structure.
... In order to remove the compromise in the design of power amplifiers, several linearization techniques, such as feedback, feedforward and predistortion, can be employed to improve the linearity of power amplifiers without sacrificing efficiency [6]. Among the linearization techniques, the predistortion method has good performance and low cost [7]. Inserting a nonlinear model which has reverse transfer characteristic of the power amplifier before the power amplifier is the principal idea of linearization in the predistortion method as depicted in Fig. 1. ...
... As an example, Mincheol Seo has proposed analog predistorter based on a Schottky diode but the improvement in spectral regrowth is very low [15]. One of the linearization methods always utilized in modern communication systems is the digital predistortion method [6,7,[16][17][18][19]. Digital predistortion is one of the most effective methods of linearization, with low cost and high flexibility due to digital hardware implementation. ...
In this paper, an adaptive digital predistortion based on a memory polynomial model is proposed in order to
linearize the power amplifier with memory effect. The coefficients of the power amplifier model have been
extracted using a least square method and those of predistortion have been identified by applying an indirect
learning structure. Finally, the performance of digital predistortion has been demonstrated using the simulation
of the power amplifier and the digital predistortion excited by a modulated 16 QAM signal in Matlab software.
According to the simulation results, the criterion of adjacent channel power ratio (ACPR) declined by around
15 dB and the input/output power spectrum density of the power amplifier has quite similar curves. The
linearized power amplifier output spectrum demonstrates the superiority of the proposed predistorter in
eliminating the spectral regrowth which is caused by the memory effect in comparison to the other linearization
methods
... Several linearization techniques, such as feedforward, feedback and predistortion, can be employed to improve the linearity of power amplifiers without losing of DC power in order to eliminate the compromise in the design of power amplifiers [5]. Among the linearization techniques, the predistortion approach has good performance and low cost [6]. As seen in Fig. 1, a complete nonlinear model which has reverse transfer characteristic of the power amplifier and places before the power amplifier is the main idea of linearization in the digital predistortion method. ...
... Because the predistortion operates at a high frequency, it has low performance and limited adaptability, although the implementation of the analog predistortion is so straightforward [7]. The digital predistortion approach is one of the linearization methods always utilized in advanced communication systems [5], [6]. The digital predistortion method is one of the most effective methods of linearization, with low cost, low power and high flexibility due to digital hardware implementation. ...
In this paper, a novel generalized two-box model is proposed to model digital predistortion and radio frequency power amplifiers in modern wireless transmitters and intelligent systems. The new model consists of two boxes that the first box emulates the static behavior of the power amplifier and the second box introduces more FIR filters considering linear and nonlinear memory effects. The coefficients of a Volterra power amplifier model have been exactly extracted using a least square method and those of predistortion have been identified by applying an indirect learning structure. Finally, the performance of digital predistortion has been demonstrated using the simulation of the power amplifier and the digital predistortion excited by a 5MHz LTE signal in the advanced design system software. According to the simulation results, the criterion of adjacent channel power ratio (ACPR) has been declined around 35dB and the spectral regrowth of the power amplifier has been reduced. The proposed generalized two-box model has achieved the better performance compared to state of the art digital predistortion models.
Different power amplifier (PA) models have their own effects on PA linearization. In this paper, the nonlinear characteristic of the radio frequency power amplifier (RF PA) is simulated based on the two models combining predistortion technology, and the nonlinear effects of the two models are analyzed, respectively. The simulation results show that Power Series model normalized mean square error (NMSE) is −37.8 dB, which is less than Power Series model −30.4 dB before loading predistortion technology. NMSE of the two systems are −23.4 dB and −26.0 dB respectively, while Saleh model compensates better than the Power Series model combing predistortion technology. The error vector magnitude (EVM) of Power Series model is only 6.75%, whereas the Saleh model EVM is 9.99%, indicating that Power Series model can better describe the nonlinear characteristic of PA. It will have a positive effect on improving the power utilization of wireless communication system.
