摘要
无人机着陆采用微波着陆系统(MLS)作导航系统具有很大优势,针对MLS信号高精度2DPSK解调和AM解调的要求,提出了一种基于FPGA的中频数字化解调方案;分析了改进科斯塔斯环法(Costas)实现载波同步及数字正交AM解调的原理;重点介绍了利用坐标旋转数字式计算机(CORDIC)算法实现数控振荡器(NCO)、鉴相、AM解调关键模块的设计过程。该算法采用流水线结构,只有加法和移位,资源消耗低、效率高、易于FPGA实现。应用VHDL硬件语言进行编程,采用同一电路完成了2DPSK解调和AM解调。仿真结果证明了方案的可行性和准确性,该方案可广泛应用于多种数字中频接收机,具有广阔的应用前景。
The Microwave Landing System （MLS） is advantageous when used as the navigation system of Unmanned Aerial Vehicles （UAV）. To achieve high-precision 2DPSK demodulation and AM demodulation of MLS signal, a FPGA-based digital intermediate frequency demodulation scheme is presented. The principle of carrier synchronizer based on improved Costas and digital quadrature AM demodulation are analyzed. The design of NCO, phase detector and key module of AM demodulation based on CORDIC algorithm are introduced in detail. The algorithm adopts pipeline architecture, and has only addition and shift, thus less resource is consumed, the efficiency is high and it＇s easy to implement in FPGA. The programe is finished in VHDL. The 2DPSK demodulation and AM demodulation are completed using the same circuit. The simulation results prove the feasibility and accuracy of the scheme. The acheme can be applied in a variety of digital intermediate frequency receivers, and has broad application prospects.
出处
《电光与控制》
北大核心
2012年第6期92-96,共5页
Electronics Optics & Control
