Microwave dielectric ceramics are mainly used as resonators, filters, dielectric antennas, dielectric guided wave circuits and other microwave components. The advantages of microwave dielectric filter are miniaturization, low loss, low frequency temperature coefficient, high dielectric constant and low cost. Compared with the metal resonator filter, it has the advantage of miniaturization, and its volume is only a few tenths of the former; compared with the acoustic surface filter, it uses high frequency and low cost. Microwave filters are widely used in microwave communications, radar navigation, electronic countermeasures, satellite relay, missile guidance, test instrumentation and other systems, is an indispensable device in microwave and millimeter wave systems, its performance often directly affects the performance of the entire communication system. It has a wide range of applications. Take mobile phones as an example. In 2005, the annual sales volume of mobile phones in China was 64 million, and the Chinese mobile phone market will grow at an annual rate of 20%, reaching 0.1 billion in two or three years. It can be seen that microwave dielectric ceramics have great development space and market in commercial applications.

Research, Development and Application of Foreign Countries

At present, there are corresponding companies abroad in the mass production of micro-filter devices, the more famous companies have the United States DLI, TRANS-TECH, Japan's MURATA, the United Kingdom's FILTRONIC companies. They produce a variety of microwave dielectric ceramic filters, duplexers, resonators, dielectric antennas and other products have been used in microwave base stations, mobile phones and cordless phones and other products, and achieved significant economic and social benefits.

The most mature in the field of dielectric filter production is the MB series integrated dielectric filter produced by Murata in Japan. Although this filter is made of ordinary ceramic dielectric materials and electrodes, based on high-frequency circuit design technology, it has greatly promoted the development of the mobile communication terminal market. In order to reduce the size, Murata has developed an MB-type chip dielectric filter, which is composed of 2-3 coaxial resonators as a whole, without the need for circuit substrates, couplers, covers, etc. The smallest 2-stage band-pass filter used in PHSl900 is only 3.8 × 4.3 × 2.0 mm3, while the corresponding 2-stage coupled dielectric filter can only reach 7.0 × 8.0 × 3.7 mm3.