The Study Of Band-stop Filter In Radio Disturbance Measurement System For GSM Mobile Station

Today's world, the rapid development of wireless communication technology resulted in our daily lives become increasingly harsh electromagnetic environment which is particularly the most widely used in the mobile phone (mobile station). In such cases, wireless communications products such as mobile phones' Electromagnetic Compatibility (EMC) testing are very necessary. In this paper, the most frequently used by GSM900 mobile phone as an example to study the electromagnetic compatibility test, radiated emission (RE) Measurement System and its components. Then we will study the band-stop filter in the measuring system, including its parameters, the design and the use of electromagnetic simulation software ADS and Microwave Office simulation.According to Electromagnetic Compatibility Standards, the EUT during the EMC tests shall be working in the typical working condition. For the GSM phone as an EUT, its typical operating state is in a communication state, the test should also be simulated in such a condition, which is different from the traditional measurement. The uplink frequency band of GSM900 is 890MHz-915MHz, which in the RE measurement system can be controlled by the tester. It's usually near the center of the channel about the frequency of 900MHz. For the power of GSM900 around 900MHz is very strong, it's necessary to insert a band-stop filter in the path of RE system to avoid damage from EUT.In the filter part, by studying of lumped, semi-lumped, distributed parameter filters, we get the simulation results and the filter indicators. Lumped parameter structure is relatively simple, but the use of these filters is in lower frequency and it's quite difficult to achieve high Q value. Distribution parameters structure is very widely used, and new filters are emerging, in this thesis I study the Microstrip Line, the frequency is appropriate and processing is simple, but its Q value is very low, too; The semi-lumped parameter is designed with small size, light weight, in order to achieve a high Q value, the capacitance in the circuit is not used, because the Q value of capacitors reduced while the frequency increases. The Q values can be up to 500 or more while the frequency is around 900MHz. The 3dB bandwidth of filter is 898MHz-907MHz, The attenuation of filter can be 35dB or more,700MHz-1400MHz range of the return loss in the range from 700MHz to 1400MHz can be greater than 17dB, its performance in the RE Measurement System will be great.