Design And Implementation Of The Rf Front-end In Broadband Real-time Surveillance & Direction-finding And Localization System

Electromagnetic spectrum monitoring and localization are the main technical means of the radio management. With the rapid development of the radio technology, the signal modulation is becoming complex and the bandwidth is also growing. Existing monitoring system has been unable to deel with the detect needs of the complex high-speed broadband radio signals effectively. Carry out the research of the broadband real-time monitoring technology, develop new equipments and systems of surveillance and localization, improve the regulatory capacity of the electromagnetic spectrum, protect the normal social order of informatization and digitization are particularly urgent.The broadband real-time surveillance & direction-finding and localization system based on software radio architecture, it realizes the direction finding of broadband signals with dual-channel and the algorithm of correlation interferometer. Its frequency measurement range covers HF, VHF, UHF and conventional wireless communications band, achieves wide analysis bandwidth and high dynamic range. The RF receiver front-end discussed in this thesis includes surveillance receiver module and direction-finding & localization module, both modules are made of high sensitivity, good selectivity superheterodyne receiver scheme, where DF antenna array using double five-uniform arryay, RF signals enter the dual-channel superheterodyne receiver, then through three frequency-conversion unit down to the last IF frequency of 76 MHz. The surveillance receiver module uses a broadband linear phase characteristic of superheterodyne receiver with surveillance antennas in the input termination to realize signals receiving.First of all, the thesis researches the basic needs of spectrum monitoring and localization system and introduces the hardware structure. With the current domestic and international product metrics and the need of measurement tasks, then gives the overall index of the RF front-end of radio surveillance & direction-finding and localization system, and mainly analyzes the superheterodyne circuit structure and implementation of the receiver front-end.Secondly, the thesis introduces the basic concepts related to the frequency and power in the RF front-end design process, discusses the characteristics of different types filter function, analyses the consistency of amplitude and phase of the superheterodyne receiver in the system of the related interference.Lastly, it studies the design process of RF receiver front-end: make frequency conversion plan, analyse harmonics of every frequency conversion unit; decompose the overall index, determine the form of every unit circuits and their corresponding RF indicators, verify the feasibility of the project through simulation; complete design of each unit circuit and RF front-end, finish parts selection and PCB layout; carry through the standard test for each unit circuit and the RF receiver front-end, and then continue to modify and optimize the RF circuit and the scheme of receiver refer to the test results.The front-end of the RF receiver has the characteristics of wide measurement frequency, wide analysis bandwidth, high SFDR and small size, the indicators of the RF front-end meet the system requirements, it can be used as the radio frequency receiver in monitoring and direction-finding system.