Microwave dielectric ceramic as a new type of electronic materials, in the modern communication is used as a resonator, filter, medium substrate, dielectric antenna, dielectric guided wave circuit, etc., are widely used in many fields of microwave technology, such as mobile phones, car phone, cordless telephone, television, satellite receivers, satellite radio, radar, wireless remote control, etc.

　　As 5G is officially put into commercial use, 5G base stations will be covered by continuous patches throughout the country, and microwave dielectric ceramics as filters are also widely used in 5G base station construction. Ceramic filter can not only ensure high power output, but also have lightweight, good temperature resistance performance, long service life, miniaturization characteristics are more suitable for the 5G base station highly integrated and miniaturized development requirements.

　　High purity magnesium oxide has high surface activity, high temperature characteristics and high purity, so magnesium oxide is generally used in ceramic filters to ensure that the filters have good conductivity, mechanical strength and high temperature resistance.

　　Magnesium oxide generally affects three parameters of the filter:

　　1. Relative permittivityεr

　　The size of the resonator is inversely proportional to the square root of the dielectric constant of the dielectric material.

　　2. Quality factor Q

　　The Q value of microwave dielectric material is inversely proportional to the dielectric loss tand.The higher the Q value, the lower the insertion loss of the filter.

　　3. The resonant frequency temperature coefficient is tauτf

　　The resonant frequency of microwave dielectric material varies greatly with the temperature, and the carrier signal of the filter will drift at different temperatures. Therefore, microwave dielectric material has a high requirement on temperature.