Research On Some Problems In Mobile Terminal Testing Enclosure

In recent years, because the transmission line theory is simple and its physical meaning is clear, and its application in the shielding field is gradually developed. More and more people interest in the transmission line analysis for its simplicity. Some try to build a shielding chamber with a load and a hole using transmission line model. The traditional calculation of shielding effectiveness is to calculate voltage ratio of the same point with and without shielding box. The advantages of this method is very easy to calculate the value, but only suitable for low frequency electric and magnetic fields. In the high-frequency, when the size of the shielding box is comparable with the wavelength, the attenuation of the electromagnetic field must take into account, so we need a new definition of shielding effectiveness of the method:The power method to calculate shielding effectiveness.As the development and improvement of the electromagnetic compatibility testing technology, people are aimed at a more simple and coventent testing method for different electrical and electronic products, especially for small electronic products such as:integrated circuits, mobile phones, automotive electronics parts. Because the electromagnetic performance of the device's integrated modules can cause a problem with the corresponding functions of the device. To slove electromagnetic interference problems well, it must be accurate detect electromagnetic interference of each module, such as the ETS-Lindgren Shielding Box Test system and the Sony Ericsson's Cobra test systems are the systems to slove the above problem.This paper begins with the basic theory of shielging box, put forward to using power to calculate the shielding effectiveness of cavity with a hole. And simulate the method's validation. Then further study of the built-in shielding effectiveness of PCB board. It has analysed and simulated the shielding box for mobile terminal EMC testing. The test box uses the superior performance ultra-wideband antenna as testing antenna which with small size, bandwidth and testing a wide range with high sensitivity. There is absorber in the shielding box. This testing box can detect as low as-120dBm signal, is much better than the existing testing box. This paper provides a reference to electromagnetic compatibility testing.