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Summary: The nonlinear power amplifier and the analogue output channel filter with nonconstant group delay add nonlinear and linear distortions to the satellite transmitted signal, respectively. Recently, there has been growing interest in using Wiener predistorters, consisting of separate nonlinear and linear components, to compensate for these distortions in the satellite downlinks. The Wiener predistorter has been shown to effectively deal with signal distortions and has lower complexity compared to other state‐of‐the‐art methods. In this paper, we argue that fully compensating the nonconstant group‐delay distortion degrades the overall performance of the Wiener predistortion systems. This is primarily due to the increased peak‐to‐average power ratio of the signal at the output of the linear predistorter. We show that the overall performance of the Wiener predistorter can be improved by undercompensating the group‐delay distortion. We propose two optimizations to address the PAPR growth problem and show using simulations that our approach leads to significant improvement in predistortion performance. Using our Wiener predistorter, the total degradation gap to the ideal limiter channel can be reduced to merely 0.34 dB for 64‐APSK modulated signals. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a practical non‐linear equalizer with iterative distortion cancellation in a satellite receiver is studied. Assuming no prior satellite channel knowledge, distortion estimation and cancellation are performed at the receiver by means of a memory polynomial model used for channel estimation. A data packet transmission scenario over a single‐carrier satellite transponder is simulated, using the not‐linearized amplifier and onboard filter characteristics similar to the direct‐to‐home broadcast DVB‐S2X reference scenario. Varying the memory depth and the non‐linear order of the memory polynomial model trained in the receiver, we compared the packet‐error rate performance of the practical non‐linear equalizer to the standard fractionally spaced linear adaptive equalizer, as well as to an implementation of the non‐linear equalizer with ideal channel knowledge at the receiver. The improved receiver demonstrates superior performance as compared with the standard linear equalizer with up to 5.48‐dB energy efficiency gain for 64‐amplitude and phase‐shift keying for a practical memory polynomial set‐up, and it approaches consistently the packet‐error rate performance of the implementation with ideal channel knowledge when increasing the memory depth and the non‐linear order. Furthermore, it enables the use of high‐order modulation up to 256‐amplitude and phase‐shift keying in the studied scenario, improving significantly the spectral efficiency of the air interface. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear autoregressive with exogenous inputs (NARX) digital pre-distortion scheme to linearize power amplifiers is proposed. The proposed NARX digital pre-distortion gives better accuracy and spectral leakage suppression compared with other commonly used Volterra-based techniques. The stability criterion of the NARX digital pre-distortion is derived from the frequency domain analysis. Simulation is carried out with a 20 MHz single carrier long-term evolution signal and two-carrier long-term evolution signal and instantaneous to average ratio of 6.2 dB at 0.01% complementary cumulative distribution function (CCDF). The results of simulation analysis show a slight improvement in adjacent channel leakage ratio performance with 30% reduction in the number of floating point operations compared with conventional pre-distortion techniques. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A baseband digital predistortion (DPD) technique based on a feed‐forward neural network (FFNN) is presented. The process of memory polynomial (MP) DPD is time consuming because of the large number of mathematical calculations. The FFNN is adopted to realise the mathematical calculations in MP DPD with direct learning architecture (DLA). The training samples of the FFNN are derived from MP DPD with DLA. It guarantees the accuracy of imitating the MP DPD. Although the training of the FFNN is time consuming, the trained FFNN DPD is less time consuming than MP DPD. This solution is validated based on a power amplifier (PA) ZFL‐2500 driven by a wideband code division multiple access (WCDMA) signal with 3.84 MHz bandwidth. The experimental results show that the FFNN can mimic the behaviour of the MP DPD. The proposed DPD achieves a significant improvement in linearity and is stable. [ABSTRACT FROM AUTHOR]