Design And Manufacture Of High Temperature Superconducting Filters For Trunking Communication

With the development of high-temperature superconducting technology becoming more and more mature,many industries have begun to apply high-temperature superconducting technology and superconducting products have greatly improved compared with the previous performance,especially in the field of electronic information and communication.The surface resistance of the superconducting material is almost zero,and the filter made from it has the characteristics of low insertion loss,high band edge steepness and out-of-band suppression and has higher selectivity to the desired signal and thus reduces the neighboring and the interference of the channel signal.The high temperature superconducting filter can effectively reduce the system noise figure and improve the ability to detect weak signals.Moreover,the superconducting filter can increase the order of the filter without sacrificing the insertion loss.Thereby effectively increasing the edge steepness and making the frequency response curve of the filter closer to the ideal rectangle and is applied to the reception of the communication base station.The front end of the machine further improves the anti-interference ability of the base station equipment.Among them,the trunking communication system is an extremely professional mobile communication system,which is the development direction of today's dedicated mobile communication.Domestic public communication facilities are inseparable from the construction of trunk communications,including public security Trunking systems and railway trunking systems.However,trunking communication as one of communication systems will inevitably have problems such as coverage blind spots,poor voice quality,dropped calls,and so on.The filter made of high-temperature superconducting material can easily make the frequency band of the filter narrow,and the size of the receiving end can be miniaturized in the case of a very low frequency band,reduce the call drop,improve the coverage and the Detection of weak signals and other issues,thereby greatly improving the efficiency of the cluster communication system.Based on the technical requirements of the Radio Frequency communication front-end receiving filter in the trunking communication system,this paper develops a high-temperature superconducting filter suitable for the trunking communication system.Considering the working frequency band and required parameters of the filter to determine the type of the filter,the design theory model of the superconducting filter is given,the theoretical response curve is obtained by the filter synthesis technique,and the coupling matrix parameters are extracted.In addition,the physical circuit structure of the filter is designed by co-simulation technology,and the superconducting filter chip is fabricated by plane fine processing techniques such as exposure,development,etching and cutting.At the same time,the filter is assembled and tested at low temperature to obtain the actual frequency response curve of the filter.In this paper,two kinds of base materials,magnesium oxide?MgO?and lanthanum aluminate?LaAlO₃?were used as the microstrip circuit for designing the filter.The simulation was carried out with SONNET software,and then the two filters were actually tested and compared.The performance of the two filters is then analyzed to compare the performance differences between the different substrates and the reasons for the difference.The final two filters are designed to have a center frequency of 353.5 MHz and an insertion loss of no more than 0.1 dB.The return loss is higher than 18dB,the out-of-band rejection is higher than 80dB,the actual test result of the filter is expected,and the design result meets the technical requirements of the trunking communication system.