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为更好地抑制带外噪声 ,减小信道间的干扰 ,在对Eureka 147DAB(数字音频广播 )信号调制过程进行介绍后 ,从频谱扩展的角度分析了 HPA (高功率放大器 )对 DAB信号的影响。分析过程中 ,HPA采用典型的 TWTA(行波管放大器 )模型 ,其非线性程度用输出功率回退 B描述。分析结果表明 ,随着 B线性增加 ,带外噪声幅度线性减小。在不加滤波器的情况下 ,离中心频率较近的带外噪声欲满足DAB发射信号频谱标准 ,B至少要在 9d B以上。分析结果为 DAB发射系统的设计提供了必要的参考依据
In order to better suppress the out-of-band noise and reduce the interference between channels, after analyzing the Eureka 147DAB signal modulation process, the influence of HPA (high power amplifier) on the DAB signal is analyzed from the perspective of spectrum spreading . During the analysis, the HPA uses a typical TWTA (traveling wave tube amplifier) model, whose degree of non-linearity is described by the output power back-off B. The analysis results show that as B increases linearly, the out-of-band noise amplitude decreases linearly. Without filter, out-of-band noise closer to the center frequency would satisfy the DAB emission signal spectrum criteria, with B being at least 9dB. The analysis results provide the necessary reference for the design of DAB launch system