Research On Acquisition And Tracking Of Weak Signal Under High Dynamic Condition Of Radio Altimeter

Current radio altimeter system,there are two major categories,a pulse system,one continuous wave system.These two types of operating modes they use a simulation method,a large number of discrete components,resulting in the type of radio altimeter is very heavy,very bulky,made the now popular card type altimeter very difficult,resulting in a difficult integration The problem.In recent years,the rapid development of microelectronic technology,a variety of new radio altimeter has emerged.They have their own characteristics.Based on the way pseudo-code Ranging widely used in various fields of science,it has matured,has been widely used,I plant developed a new digital radio altimeter uses a pseudo-code ranging mode,all-digital processing platform,with the popular FPGA + DSP architecture model.Radio altimeter excellent performance of this system,small size,light weight,low power consumption,wide altimeter range,high precision,anti-interference ability,stability and good shielding characteristics,and allows multiple signals to occupy the same frequency spectrum.Firstly,the research status radio altimeter,the direction of development,the application to do a simple introduction;and describes the characteristics of the radio altimeter sea surface reflected signal and analyzed opened echo signal analysis and calculation of the radio altimeter radar the general formula of the equation,given the continuous wave and pulsed institutional system of each radar equation.Secondly,it introduces the principle of PN ranging PN code phase modulation system and radio altimeter principles and implementation,where the radio altimeter consists of an antenna,antenna feeder cable,a transmitter,a receiver and a digital signal part,radio altimeter functional components will be described.Then,focus on the high dynamic weak signal tracking method was captured.Cited uncertainties capture and its impact,the advantages and disadvantages of sliding correlation analysis method and the digital matched filter method,by comparison algorithm,the radio altimeter uses a serial code acquisition eventually sliding correlation method,it discusses the code acquisition the best detection method,in order to improve the ability to capture weak signals and reduce the false alarm rate,signal processing,respectively,using the accumulated detector and dual threshold detector,and ultimately given code acquisition parameters through the analysis.In order to achieve rapid capture carriers,where the use of the FFT algorithm,this paper analyzes the FFT algorithm resolution and dynamic range,the ability to capture weak signals,and verify the correctness of the algorithm through MATLAB simulation,tired eventually given a specific carrier acquisition Implementation.For high dynamic tracking of weak signals,the detailed analysis of the code tracking loop and carrier tracking loop,code tracking loop using a delay locked loop,the loop filter using the second-order phase-locked loop and delay locked loop discriminator algorithm performed the analysis and optimization of the noise bandwidth of the loop filter of a selection is made,the carrier tracking loop using Costas loop,the loop filter using the second-order phase-locked loop frequency-locked-for-assisted 3-order mode,and the discriminator algorithm analysis and optimization of the noise bandwidth of the loop filter is a selection.Finally,the PN code phase modulation radio altimeter system application a brief description of the laboratory test conditions and test out a brief analysis of experiments,it was found that the altimeter system stable and reliable.