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实践已经证明,射频线性化技术和数字预失真技术都可以有效地抵消大功率放大器工作在饱和点附近时由非线性特性产生的失真。由于数字预失真器成本低、实现简单,这使之成为昂贵的、高功耗射频线性化器的一种非常有希望的备选方案。数字预失真器根据输入信号的大小调整信号幅度和进行移相,其调整系数取决于放大器的非线性特性,这些系数既可以直接通过网络分析仪测量放大器的特性而获取,也可以藉由自适应调整初始估计值获得,从而使得误差减少到最小。误差通常是指发射信号和取样信号之间的差异。自适应可使用标准的梯度下降算法,如最小均方(LMS)来完成。本文比较了两种方法的测试结果,这些测试是针对航天级行波管放大器(TWTA)进行的。结果表明自适应方法具有更好的频域特性(肩部减小),然而在改善信噪比和误码率方面,这两种方法的性能几乎是一样的。
Practice has proved that RF linearization and digital predistortion techniques can effectively offset the non-linear distortion caused by the high-power amplifier operating near the saturation point. Due to the low cost and simplicity of the digital predistorter, this makes it a very promising alternative to expensive, high-power RF linearizers. Digital predistorter according to the size of the input signal to adjust the signal amplitude and phase shift, the adjustment coefficient depends on the nonlinear characteristics of the amplifier, these coefficients can be obtained directly through the network analyzer to measure the characteristics of the amplifier to obtain, but also by adaptive Adjust the initial estimate obtained, so that the error is reduced to a minimum. The error is usually the difference between the transmitted signal and the sampled signal. Adaptive can be done using standard gradient descent algorithms, such as Least Mean Squares (LMS). This article compares the results of two approaches that were tested for space-grade TWTs. The results show that the adaptive method has better frequency-domain characteristics (shoulder reduction), however, the performance of these two methods is almost the same in terms of improving signal-to-noise ratio and bit error rate.