Wireless communication base station (referred to as base station, macro base station) is a wireless interface device for mobile devices to access the Internet. In a certain radio signal coverage area, information is transmitted between the mobile communication switching center and the mobile terminal equipment, so the mobile communication base station can also be called a radio station. The construction of mobile communication base station is an important part of the communication network of mobile communication operators, and the construction of mobile communication base station is generally carried out around the signal coverage, call quality, construction difficulty, maintenance convenience, investment benefits and other factors. With the increase of the number of mobile terminal users, the amount of data is also doubling, and users have higher and higher requirements for operators. In this case, operators in addition to the continuous optimization of base stations, but also the mobile communication network to the direction of data and packet development, the development trend of mobile communication base stations is also bound to be broadband, large coverage construction and IP development.
When it comes to the base station, we have to say that the multi-service distribution system (MDAS), is a multi-service distribution system, can support multiple operators, multi-standard, multi-carrier, and integrated WLAN system, one step to solve the voice and data service needs, compared with the traditional analog distribution system, and has hybrid networking, delay compensation, automatic carrier tracking, uplink bottom noise low characteristics. MDAS provides 2G, 3G, 4G mobile communication services, but also integrated WLAN system, used to meet the user's high-speed wireless data transmission needs.
The filter in the 4G era, the metal coaxial cavity filter is the absolute mainstream, its working principle is to oscillate through electromagnetic waves of different frequencies in the cavity, retain the electromagnetic waves that reach the resonant frequency of the filter, and the electromagnetic waves of other frequencies dissipate in the oscillation, to achieve the function of filtering. This filter technology is mature, low production cost, should be a good choice for 5G, but in 5G communication, the remote radio frequency unit (RRU) and the antenna will be integrated into the active antenna unit (AAU) together with the tower, the highly integrated and miniaturized development of the base station has higher requirements for the size, weight, power and heating performance of the filter. The metal coaxial cavity filter has the characteristics of large volume, large weight, large heat and so on, and the price is relatively expensive, which will be unfavorable to the installation and commissioning and the tower load while increasing the cost. In order to solve the above problems, the industry began to pay attention to the two solutions of small metal cavity filters and ceramic medium filters.
Small metal cavity filter is a rapid commercial solution to reduce the volume and weight of the filter under the premise of maintaining basic stability through process optimization, but the solution is limited by the process bottleneck, currently mainly used in the low frequency band below 2.66GHz, the future will not be covered by large specifications, only as compensation.
Ceramic dielectric filter is made of ceramic material, no metal cavity, electromagnetic wave resonance occurs in the dielectric material, with high dielectric constant, high Q value, low insertion loss, small volume, light weight, low cost, good temperature drift resistance and other characteristics, can withstand high power, has a good frequency selection effect, easy to large-scale integration. However, the production accuracy of ceramic filter is high, and the current cost has not come down, due to the low price of ceramic powder raw materials, once mass production is achieved, the cost can be greatly reduced, so the future ceramic filter will occupy the main market of 5G filter.
