Unwanted Emissions of Multi-Carrier Transmitter in Spurious Domain
Unwanted Emissions of Multi-Carrier Transmitter in Spurious Domain
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杂散域中多载波发射机的无用发射
DOI：
10.2514/6.2008-5464
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
Yukiharu Kitayama
中科院分区：
文献类型：
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作者：
Masayoshi Tanaka;H. Sakamoto;M. Kobayashi;Yukiharu Kitayama
我们从理论和实验上分析了用于卫星通信的多载波发射机在ITU WRC-03中定义的杂散域中产生的杂散发射。在多通道或多载波发射机/应答器中产生杂散发射的机制特别复杂，其中多个载波可能同时从最终输出转发器发射。我们特别关注了由于高功率放大器（HPA）的非线性而产生的杂散发射，因为HPA是产生杂散发射的主要元件。特别需要确定HPA系统既有效又满足推荐杂散发射水平的发射水平和条件。因此，我们研究了多载波发射机的理论和实际特性。我们发现，杂散发射水平几乎是相同的，当载波的数量是超过八个，因此，我们可以估计最坏的杂散发射水平从八个载波的结果。此外，我们还研究了它对非线性的敏感性和它对HPA工作点的依赖性，以及系统设计的信号带宽。我们开发了一种简单且具有成本效益的评估方法，该方法使用一个未调制（CW）测量和一个简单的计算来确定系统是否与建议兼容，而无需执行复杂的多载波测试。分析和我们提出的评估方法将有助于可能的功率效率的卫星多载波系统的建设。
We analyzed theoretically and experimentally the spurious emissions that a multicarrier transmitter used for satellite communications produces in the spurious domain defined in ITU WRC-03. The mechanism that generates spurious emissions in multichannel or multi-carrier transmitters/transponders—where several carriers may be transmitted simultaneously from a final output amplifier—is particularly complex. We paid particular attention to the spurious emissions generated due to the nonlinearity of a high-power amplifier (HPA) because the HPA is a dominant component in generating spurious emissions. It is particularly desirable to determine the emission level and conditions under which an HPA system is both efficient and meets recommended spurious emission levels. Therefore, we investigated the theoretical and actual characteristics of a multi-carrier transmitter. We found that the spurious emission levels are almost the same when the number of carriers is beyond eight and, therefore, we can estimate the worst spurious emission level from the eight-carrier result. Furthermore, we also studied its sensitivity to the nonlinearity and its dependence on the operating point of HPA, and the signal bandwidth for the purpose of system design. We developed a simple and cost effective evaluation method that uses one un-modulated (CW) measurement and a simple calculation to determine whether a system is compatible with the recommendations without performing complex multi-carrier tests. The analysis and our proposed evaluation method will help make possible the construction of powerefficient satellite multi-carrier systems.