HPA的非线性对DAB信号的影响

Effects of HPA nonlinearities on DAB signals

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

The out of band noises of Eureka 147 DAB (digital audio broadcasting) signals produced by HPA (high power amplifier) nonlinearities were analyzed to reduce the interference to adjacent channels. The analysis used a typical TWTA (traveling wave tube amplifier) model with B (output backoff) to describe its nonlinearities. The results show that the linear increase of the B results in a linear decrease of the out of band noise power. Without a RF filter, B should be more than 9dB so that the out of band noises near the central frequency can achieve the DAB transmitting signal criterion. This result provides a necessary improvement for the design of DAB transmitting systems.