VHF/UHF波段发射机互调抑制比测试方法研究

Intermodulation attenuation ratio test methods for VHF/UHF band transmitters

建立了发射机射频电路简化模型,并利用该模型和非线性多项式模型,研究了发射机互调(IM)发射电平与射频前端滤波器插入损耗、干扰信号功率和频率偏差之间的关系,对当前发射机互调抑制比的定义进行了修正;分析了传统发射机互调抑制比测试方法的局限性,设计了一种新型的发射机互调测试链路配置,分析了测试链路关键物理参数间的关联关系,建立了测试数据处理模型,该方法扩宽了测试带宽和功率范围,降低了对测试器件的要求。对实际电台的测试结果表明,本文提出的理论分析结论和发射机互调抑制比测试方法正确有效。

The simplified model of transmitter RF circuit was established.Using this model and the nonlinear polynomial model,we studied the relationship of transmitter intermodulation（IM） level between the insertion loss of RF filter,the power and the frequency offset of interference signal.According to results of the theoretical analysis,we found the imperfection of the definition of current transmitter IM attenuation ratio,and also propounded the new definition.We analyzed the limitation of the transmitter IM attenuation ratio test method.In order to get more accurate test data of transmitter IM level,we designed the new configuration of transmitter IM level test link.A new test method was proposed after analyzing the relationship between key physical parameters of the link.We provided the processing model of test data.The new method expands the frequency test band,relaxes the restrictions of transmitter power,and reduces the performance requirement of test device.The new method was used in IM test of a substantial broadcasting station,the test result and the theory analysis are validated,and the rationality and accuracy of the test methods are proved.