| In the process of microwave measurement, adjusting the level of the measured signal is an important part. In the automatic measurement process, programmable attenuator is often used for signal adjusting. The attenuation of signals in different levels is facilitating to measurement.This design is a suit of signal control system which works on the level of -140dBm, and the interference on the level of -50dBm, the incremental attenuation accuracy reach to 0.1dB, attenuation range is 0.1dB to 60dB. However, in the electromagnetic interference environment, electromagnetic interference will couple into the attenuator and makes the attenuation lift more than 10dB, so the attenuator can not produce 0.1dB incremental. Then, the goal of this design is to makes the attenuator which works in the environment with interference level up to -50dBm and the working-level low to -140dBm can accurately produce 0.1dB attenuation incremental. According to the principles of electromagnetic compatibility, according to the computation by electromagnetic simulation software HFSS, at last, by the ways of shielding, absorbing, and grounding to ensure the system can produce 0.1dB incremental and works well. Finally, designed a suit of signal control system and tested to meet the requirements. Both the two frequencies points can produce 0.1dB incremental.The main topics including:According to EMC technical theory and engineering technology, combined with the characteristics of this device, work out the implementation methods of signal control according to the simulation of metallic shield and absorbing materials absorb the interference with HFSS software.According to the results of simulation, assess the feasibility of components, then design and produce a signal control system.Assemble and install the signal control system, assess the performance of the system through ComparativeAnalyze the problems and possible improvement method in the experiment. Propose further improvements. |
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