Abstract-One of the severe drawbacks of orthogonal frequency division multiplexing (OFDM) is high Peak-to-Average Power Ratio (PAPR) of transmitted OFDM signals. During modulation the sub-carriers are added together with same phase which increases the value of PAPR, leading to more interference and limits power efficiency of High Power Amplifier (HPA), it's requires power amplifier's (PAs) with large linear operating ranges but such PAs are difficult to design and costly to manufacture. Therefore, to reduce PAPR various methods have been proposed. As a promising scheme, partial transmit sequences (PTS) provides an effective solution for PAPR reduction of OFDM signals. In this paper, we propose a PAPR reduction method for an OFDM system with variation of phases based on PTS schemes and Solid State Power Amplifiers (SSPA) of Saleh model in conjunction with digital predistortion (DPD), in order to improve the performance in terms of PAPR, the HPA linearity and for the sake of mitigating the in-band distortion and the spectrum regrowth. The simulation results show that the proposed algorithm can not only reduces the PAPR significantly, but also improves the out-of-band radiation and decreases the computational complexity.

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In this paper, a 3.1–11 GHz ultra-wideband low noise amplifier with low noise figure, high power gain S21, low reverse gain S12, and high linearity using the OMMIC ED02AH process, which employs a 0.18 μm Pseudomorphic High Electron Mobility Transistor is presented. This Low Noise Amplifier (LNA) was designed with the Advanced Design System simulator in distributed matrix architecture. For the low noise amplifier, four stages were used obtaining a good input/output matching. An average power gain S21 of 11.6 dB with a gain ripple of ±0.6 dB and excellent noise figure of 3.55 to 4.25 dB is obtained in required band with a power dissipation of 48 mW under a supply voltage of 2 V. The input compression point 1 dB and third-order input intercept point are −1.5 and 23 dBm respectively. The core layout size is 1.8 × 1.2 mm2.

Introduction:This paper focuses on improving the power amplifier linearity for wireless communications. The use of a single branch of a power amplifier can produce high distortion with low efficiency.Method:In this paper, the Linear Amplification with Nonlinear Components (LINC) technique is used to improve the linearity and efficiency of the power amplifier. The LINC technique is based on converting the envelope modulation signal into two constant envelope phase-modulated baseband signals. After amplification and combining the resulting signals, the required linear output signal is obtained. To validate the proposed approach, LINC technique is used for linearizing an amplifier based on a GaAs MESFET (described by an artificial neural network Model).Conclusion:Good results have been achieved, and an improvement of about 40.80 dBc and 47.50 dBc respectively is obtained for the Δlower C/I and Δupper C/I at 5.25 GHz.

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