Design And Realization Of Shortwave High Dynamic Digital AGC RF Front-end

With rapid development of radio navigation technology, RF receiver technology as an important component of wireless communications technology has been constantly enhanced and improved. RF front-end completed signal pre-filter, power amplifier, gain control and downconversion capabilities. Implementation of this project "high dynamic digital AGC RF front-end" worked in the short-wave spectrum for broadband, large dynamic range, low noise figure and has better interference rejection capability.Based on reference to a large number of relevant information at home and abroad, this paper described and analyzed the RF front-end architecture. According to the technical indicators issues and taking into account the requirements of existing devices, the system uses double-conversion of the superheterodyne architecture. Through double-conversion the structure output low-IF, and got higher image rejection and stable power amplification. The RF front-end circuit consists of three parts, including the former access circuit, the vibration signal source circuit and digital AGC circuit. Former access circuit completed signal amplication, filtering and frequency conversion; the vibration signal source using digital frequency synthesis technology to achieve both the vibration signal and clock signal with high accuracy and low spurious frequency synthesis; digital AGC circuit with double channel sampling capability to achieve three digital AGC. The digital demodulation algorithm and the AGC control algorithm to achieve in the CPLD. This paper presented a case comparison, CIC filter and orthogonal transformation detection method, and compared their advantages and disadvantages through simulation. Digital AGC finally adopted the orthogonal transformation detection method and multi-threshold value judgments control algorithm to achieve a high dynamic AGC.According to the overall system architecture, designed and produced the corresponding RF front-end circuits, and gave the test results through actual testing and debugging.