1. ECEN5633 Radar Theory Lecture #29 28 April 2015 Dr. George Scheets www.okstate.edu/elec-eng/scheets/ecen5633 n Read 6.2 n Problems 6.2, Web 17 & 18 n Exam #2 Final Stats Hi = 90, Low = 45, Average = 78.50, σ = 16.98 A > 85, B > 73, C > 61, D > 50 n Design Problem Rework u Due by midnight, 28 April (Live); midnight, 29 April (DL) n Quiz Rework u Due by midnight, 30 April (Live); 1 week after return (DL) n Final Exam u 0800 – 0950, Thursday, 7 May u No Later than Thursday, 14 May

2. ECEN5633 Radar Theory Lecture #30 28 April 2015 Dr. George Scheets www.okstate.edu/elec-eng/scheets/ecen5633 n Read 6.3 n Quiz Rework u Due by midnight, 30 April (Live) u 1 week after return (DL) n Final Exam u 0800 – 0950, Thursday, 7 May u No Later than Thursday, 14 May

3. Frequency Hopped Radar n Slow Hop u Multiple pulses on same carrier frequency u Standard P(Hit) equations apply n Fast Hop u Multiple frequencies per pulse F Spreads pulse energy around, aids stealthiness u SNR may change u Standard P(Hit) equations apply u Want |f i – f j | large relative to t h F Include expected doppler shift F Can estimate shape of Ambiguity Function

4. Coherent PLL Carrier Recovery nSnSnSnSpectrum: need a delta function at fc nPnPnPnPSK signal doesn't have one upupupup(t) = c(t)cosωct; c(t) = +1 or -1 chips nSnSnSnSquare p(t) uYuYuYuYields cos2ωct = (1/2)[cos0 + cos2ωct] nBnBnBnBandpass filter uYuYuYuYields (1/2)cos2ωct nHnHnHnHard limit uYuYuYuYields a square wave at 2fc Hertz nRnRnRnRun through a divide by 2 counter uYuYuYuYields a square wave at fc Hertz nNnNnNnNarrow bandpass filter (Pass fundamental frequency) uYuYuYuYields a cosωct at carrier frequency

5. Phase Coded Radar n Vary phase of transmitted signal u Transmit PSK u Could be + π Doesn't have to be u Spreads the spectrum Can increase steathiness n Ideal "thumbtack" Ambiguity Function u Can be approached with Frequency Hopping… u … or Phase Coding

6. Random Sequence, 20 chips/pulse

8. Example Noise Jamming n Unjammed Stats

9. Example Noise Jamming n Noise Power Doubled

10. Example Noise Jamming n P(False Alarm) threshold adjusted 500(.001905) = 9.525 false alarms/second = 34,290 per hour

11. Unchirped Signal Expected ∑ = -63.66

12. Chirped Signal Expected ∑ = -4.164

13. Unchirped Signal Expected ∑ = 0.00000019

14. Chirped Signal Expected ∑ = -14.38