雷达系统分析chapter three.ppt

1、XIDIAN UniversityRadar Systems Analysis and Design Using MATLAB2024/11/12National Lab of Radar Signal ProcessingZhang Juan(张娟张娟)8820258088202580北校区新科技楼北校区新科技楼15091509Liu Nan(刘楠刘楠)N8820258088202580北校区新科技楼北校区新科技楼15091509Table of Contents2024/11/12National Lab of Radar Signal ProcessingP2Chapter 1:Rada

2、r FundamentalsChapter 1:Radar FundamentalsChapter 2:Signal ProcessingChapter 2:Signal ProcessingChapter 3:Continuous Wave and Pulsed RadarsChapter 3:Continuous Wave and Pulsed RadarsChapter 4:Radar DetectionChapter 4:Radar DetectionChapter 5:Radar Waveforms AnalysisChapter 5:Radar Waveforms Analysis

3、Chapter 6:Matched Filter and the Radar AmbiguityChapter 6:Matched Filter and the Radar AmbiguityChapter 7:Pulse CompressionChapter 7:Pulse CompressionTable of Contents2024/11/12National Lab of Radar Signal ProcessingP3Chapter 8:Radar Wave PropagationChapter 9:Clutter and Moving Target Indicator(MTI)

4、Chapter 10:Radar AntennasChapter 11:Target TrackingChapter 12:Synthetic Aperture Radar(optional)Chapter 13:Radar Cross Section(optional)3.1.Functional Block Diagram of Continuous Wave(CW)Radar2024/11/12National Lab of Radar Signal ProcessingP43.2.CW Radar EquationThe NBF bank(Doppler filter bank)can

5、 be implemented using a Fast Fourier Transform(FFT).The dwell interval determines the frequency resolutionIf the Doppler filter bank is implemented using an FFT of size ,the effective radar Doppler bandwidth is .The factor 2 is needed to account for both positive and negative Doppler shifts.The CW r

6、adar equation can now be derived from the high PRF radar equation 2024/11/12National Lab of Radar Signal ProcessingP53.3.Frequency ModulationAn FM waveform can be expressed by The phase is given by where is the FM modulation index given by is the radar operating frequency(carrier frequency),is the m

7、odulating signal,is a constant,and ,where is the peak frequency deviation.2024/11/12National Lab of Radar Signal ProcessingP62024/11/12National Lab of Radar Signal ProcessingP7 Bessel function Using the complex exponential Fourier series Make the change of variable ,2024/11/12National Lab of Radar S

8、ignal ProcessingP82024/11/12National Lab of Radar Signal ProcessingP9The bandwidth of FM signals is infinite.However,the magnitudes of spectral lines of the higher orders are small,and thus the bandwidth can be approximated using Carsons rule,For small (),the Bessel functions ,other .Measure range 2

9、024/11/12National Lab of Radar Signal ProcessingP103.4.Linear FM(LFM)CW RadarCW radars may use LFM waveforms so that both range and Doppler information can be measured.Stationary target2024/11/12National Lab of Radar Signal ProcessingP11modulating frequencyrate of frequency changebeat frequency2024/

10、11/12National Lab of Radar Signal ProcessingP12 Non-stationary target:When the target is not stationary the received signal will contain a Doppler shift term in addition to the frequency shift due to the time delay.beat frequencyduring the positive portions of the slopeduring the negative portions o

11、f the slopeRange MeasureDoppler Measure2024/11/12National Lab of Radar Signal ProcessingP13In practice,for non-stationary target the maximum time delay is normally selected as .Thus,the maximum range is given byThe maximum unambiguous range will correspond to a shift equal to .No ambiguity within th

12、e maximum range.3.5.Multiple Frequency CW RadarSingle frequencyp The maximum unambiguous range occurs when .A radar with two CW signals(two frequecies)p The maximum unambiguous range occurs when .2024/11/12National Lab of Radar Signal ProcessingP143.6.Functional Block Diagram of Pulsed Radar2024/11/

13、12National Lab of Radar Signal ProcessingP15Carrier frequencyPulse widthModulationPulse repetition frequency (RPF)+detector3.7.Range and Doppler AmbiguitiesRange measureDoppler measureRange ambiguous:A second pulse is transmitted prior to the return of the first pulse.Doppler ambiguous2024/11/12Nati

14、onal Lab of Radar Signal ProcessingP163.8.Resolving Range Ambiguity2024/11/12National Lab of Radar Signal ProcessingP17We choose and such that they are relatively prime with respect to one another.One choice is and .Within one period of the desired PRI()the two PRFs coincide only at one location,whi

15、ch is the true unambiguous target position.2024/11/12National Lab of Radar Signal ProcessingP18Let be the number of PRF1 intervals between transmit of a pulse and receipt of the true target return.Similarly for .It follows that,over the interval 0 to ,the only possible results are or .When andWhen a

16、nd ,3.9.Resolving Doppler AmbiguityThe same methodology can be used to resolve Doppler ambiguity.and respectively denote the number of ambiguities for and .Here assume .If and ,If and 2024/11/12National Lab of Radar Signal ProcessingP192024/11/12National Lab of Radar Signal ProcessingP20It follows t

17、hat the minimum that may satisfy the above three relations are ,and .3.10.MATLAB Program“range_calc.m”The program“range_calc.m”solves the radar range equation of the formCode package for this book can be downloaded from CRC Press Web site“”.2024/11/12National Lab of Radar Signal ProcessingP21Summary

18、Functional block diagrams of CW radar and pulsed radarBasic theory and methods of range and Doppler measure for CW radarp FMp LFMp Multiple frequenciesRange and Doppler ambiguities and resolving methods for pulsed radar2024/11/12National Lab of Radar Signal ProcessingP22End of Chapter 3Thank You!2024/11/12National Lab of Radar Signal ProcessingP23