Research And Implementation Of Multi-Channel Digital Down-Conversion

Multi-target telemetry and tracking systems is made up of multi-targets telemetryand multi-target tracking. The systems are dedicated to telemetry, reconnaissance andtracking multi targets in air including aircraft, small satellite and so on. Comparing totraditional national system, multi-target telemetry and tracking systems have goodperformance and simplified system structure. The role of digital down conversiontechnology is translate digital IF signal into baseband signal, and the change inmulti-target telemetry and tracking systems are an indispensable part, so digital downconversion technology has important practical significance.The paper is based on multi-target telemetry and tracking systems to design multi-channel digital down-conversion. Two kind of multi-channel digital down-conversionrealization methods based on FPGA (Field Programmable Gate Array) and ASIC(Application Specific Integrated Circuit) are researched, and program of two differentmethods to achieve the digital down-conversion are designed on the same hardwareplatform. In the paper, the followings are the mainly content:Firstly, the significance and application of Multi-target telemetry and trackingsystems has introduced. The development and research situation of software radio anddigital down-conversion are also presented. The basic theory of the digitaldown-conversion is further studied, including sampling theory, multi-rate signalprocessing theory, digital orthogonal frequency mixing theory and architecture of digitaldown-conversion. Key technologies of the digital down-conversion are studiedparticularly, including Principle and method of NCO and decimation filter.Secondly, the system structure of multi-channel digital down-conversion in themulti-channel system structure is studied, the system structure is made of RF to IFconversion module and digital down-conversion. A multi-channel digital down-conversion hardware platform is designed and realized, the hardware platform is made ofpower module, ADC sampling module, down-conversion module, MCU configurationmodule and FPGA control module. The schematic of the various modules are designed byAltium Designer software and finished hardware circuit debugging. Realization ofhardware circuit provides a basis for software.Thirdly, the realization of two different methods has proposed. The first methodimplementation process based FPGAs including: NCO module, Mixer module and decimation filter module are designed by programming based on Quartus Ⅱsoftware andcalling IP core. The digital down-conversion function is verified by hardware andsoftware co-simulation. The second method implementation process based GC5016including: Decimation filter in GC5016is designed by Matlab software and GC5016isconfigured by MCU, then digital down-conversion function is verified byQuartus Ⅱsoftware.Finally, the simulation results of the two methods indicate that the method based onGC5016is superior in performance, but less flexible than the method using FPGAs.Therefore, the solution proposed in this thesis is not only suitable for the occasions wherea high performance is required, but also suitable for the occasions where performance isrelatively less demanding.