Post on 17-Dec-2015
ECEN5633 Radar TheoryECEN5633 Radar TheoryLecture #22 2 April 2015Lecture #22 2 April 2015Dr. George ScheetsDr. George Scheetswww.okstate.edu/elec-eng/scheets/ecen5633www.okstate.edu/elec-eng/scheets/ecen5633
ECEN5633 Radar TheoryECEN5633 Radar TheoryLecture #22 2 April 2015Lecture #22 2 April 2015Dr. George ScheetsDr. George Scheetswww.okstate.edu/elec-eng/scheets/ecen5633www.okstate.edu/elec-eng/scheets/ecen5633
Read 4.3Read 4.3 Problems 4.10, Web 8 & 9Problems 4.10, Web 8 & 9 Design Problem due 7 April (Live), 9 April (DL)Design Problem due 7 April (Live), 9 April (DL)
Late turn in fee = -1 per working dayLate turn in fee = -1 per working day Reworked exams due 14 April (Live)Reworked exams due 14 April (Live) Quiz #2 ResultsQuiz #2 Results
Hi = 13.6, Low = 6.50, Ave = 11.33, Hi = 13.6, Low = 6.50, Ave = 11.33, σσ =2.71 =2.71
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Coherent DetectionCoherent Detection RCVR Local OscillatorRCVR Local Oscillator
PLL seeks echo frequency & phase lockPLL seeks echo frequency & phase lockttpp = 1 = 1 μμsec, fsec, fcc = 10 GHz → 10,000 cycles = 10 GHz → 10,000 cycles
Will take some time Will take some time Some echo energy is lost Some echo energy is lost Matched Filter fed sinusoid until lockMatched Filter fed sinusoid until lock
Area around zeroArea around zero
Locked → Matched Filter fed baseband pulse Locked → Matched Filter fed baseband pulse Best Potential PerformanceBest Potential Performance
Non-coherent DetectionNon-coherent Detection
RCVR Local Oscillator at transmitted fRCVR Local Oscillator at transmitted fcc
Stationary target with respect to radarStationary target with respect to radarZero doppler, baseband pulse to Matched FilterZero doppler, baseband pulse to Matched Filter
Moving target with respect to radarMoving target with respect to radarWide variety of signals fed to Matched FilterWide variety of signals fed to Matched Filter
May get almost nothing when sampledMay get almost nothing when sampled Quadrature DetectionQuadrature Detection
If energy not in I channel, it's in Q channelIf energy not in I channel, it's in Q channel
Ambiguity FunctionAmbiguity Function
X(X(ττ,,νν) = g(t)g*(t - ) = g(t)g*(t - ττ) e) ej2j2πνπνt t dtdt
X(X(ττ,0) = Autocorrelation ,0) = Autocorrelation of complex envelope g(t)of complex envelope g(t)
= Matched Filter output envelope= Matched Filter output envelope at Zero dopplerat Zero doppler
X(0,X(0,νν) = F.T. of signal's magnitude (AM)) = F.T. of signal's magnitude (AM)
∫-∞
+∞
Ambiguity FunctionAmbiguity Function
X(X(ττ,,νν) = g(t)g*(t - ) = g(t)g*(t - ττ) e) ej2j2πνπνt t dtdt
For most accurate range estimatesFor most accurate range estimates Want narrow width along Want narrow width along ττ (time) axis (time) axis
For most accurate radial velocity estimateFor most accurate radial velocity estimate Want narrow width along Want narrow width along νν (frequency) axis (frequency) axis
Since X(0,0) = 1 &Since X(0,0) = 1 &Volume of |X(Volume of |X(ττ,,νν)|)|22 = 1 (if complex E = 1) = 1 (if complex E = 1)May not be able to do both May not be able to do both
∫-∞
+∞
Selected e IntegralsSelected e Integrals
Gaussian Pulse Ambiguity FunctionGaussian Pulse Ambiguity Function ttpp = 1.0 = 1.0
source: west 5633 notes
Matched Filter Outputs as fd ↑ Matched Filter Outputs as fd ↑
fd = 1
fd = 2fd = 3
fd = 5
Rectangular Pulse Ambiguity FunctionRectangular Pulse Ambiguity Function
source: skolnik, Introduction to Radar Systems