Intermodulation attenuation ratio test methods for VHF/UHF band transmitters

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.