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Staggered PRT and Phase Coding Algorithms on the KOUN Research Radar

NEXRAD Range-Velocity Ambiguity Mitigation. Staggered PRT and Phase Coding Algorithms on the KOUN Research Radar. Sebastian Torres. Part One. Research RDA (RRDA) Capabilities. VCP Definitions. Legacy VCP definition RPG Message 7 ICD RDA/RPG (Doc. # 2620002A) Provision for

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Staggered PRT and Phase Coding Algorithms on the KOUN Research Radar

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  1. NEXRAD Range-Velocity Ambiguity Mitigation Staggered PRT andPhase Coding Algorithms on the KOUN Research Radar Sebastian Torres

  2. Part One Research RDA (RRDA) Capabilities

  3. VCP Definitions • Legacy VCP definition • RPG Message 7 • ICD RDA/RPG (Doc. # 2620002A) • Provision for • Waveform Type • Constant or Random Phase • Waveform Configuration • Staggered Pulse Pair • Not supported on the WSR-88D! • No provision for systematic phase codes • No provision for staggered pattern definition

  4. VCP Definitions • RRDA VCP definition • Concurrent with NPI and Homeland Security Experiment • High-resolution data • Horizontal raster, vertical raster, searchlight scans • Backward compatible with Legacy definition for supported modes • R/V mitigation techniques are specified on a scan-by-scan basis • Proposed VCP for R/V

  5. VCP Definitions • Phase Coding Features • Can specify phase coding sequence number for each scan • Standard (or predefined) • Downloadable • Proposed new RPG Message to define phase coding sequence • Sequence length • Phases specified as multiples of 2p/128

  6. VCP Definitions • Staggered PRT Features • Can specify patterns using • Up to 3 PRI’s • A pulse count (M) for each PRI • An overall pattern count (Mp) • Examples • Standard staggered pattern: T1, T2, T1, T2, … • PRI1 = 1, M1 = 1, PRI2 = 2, M2 = 1, Mp = 32 • Block staggered pattern: T4, T4, T2, T2, T2, T4, T4, T2, T2, T2, … • PRI1 = 4, M1 = 2, PRI2 = 2, M2 = 3, Mp = 10

  7. Hardware Enhancements • Synchronizer • Phase coding of transmitted pulses • Uses legacy phase shifter (7 bits) • Generation of staggered pulse patterns • Generation of expanded set of PRTs • Legacy has limited set • Requirements for precise T1/T2 ratios • Requirements for different ra • Resolution given by 9.6 MHz clock

  8. Software Enhancements • Archive I Recorder • Handling of variable range-sweep sizes • Associated tools to handle phase-coded and staggered PRT data • Signal Processing • SimSPS model • Rapid prototyping • Real-time implementation • Phase coding: 1st trip decoding • Staggered PRT: full processing with simple GCF

  9. Part Two RRDA Implementation of the Staggered PRT Algorithm

  10. Assumptions • Transmission sequence alternates two PRT’s for a total of M pulses • N1 and N2 are range gates for T1 and T2 • No echoes beyond max(ra1, ra2) • Overlay of “short” into “long” • Echoes extending beyond max(ra1,ra2) can be censored • Does not assume: • M is even • T1/T2 is rational • T1 < T2 • In what follows T1 < T2 for clarity

  11. Inputs • Time-series data V(n,m) = I(n,m) + jQ(n,m)0 <m < M0 <n < N1 for even m0 <n < N2 for odd m • Associated metadata • GCF Maps • Adaptation Data As in legacy PSP

  12. Outputs • Base data • ReflectivityZ(n), for 0 <n < N2 • Doppler velocityv(n), for 0 <n < N1 • Doppler spectrum withw(n), for 0 <n < N1 • Z is computed through ra2 • v and w are computed through ra1 • Could include censored data up to ra2

  13. T1 T1 T2 Algorithm • Suppress interference • Legacy PSP algorithm • Compute powers and correlations • P1, R1 for short range sweeps • P2, R2 for long range sweeps

  14. Algorithm • Apply GCF: DC removal • Compute time-series mean: Vm • Remove |Vm |2 from P1, P2, R1, and R2 • Use bypass map • Could use Sachidananda’s GCF (Rep. 3 & 4) • Suppress point clutter • Legacy PSP algorithm • Compute Doppler velocities • v1 based on R1 • v2 based on R2

  15. Algorithm • De-alias v1 using v2 • Use v1 and v2 to determine Nyquist interval • De-alias v1 • Close to MMSE for SD(v1) >> SD(v2) • Compute Doppler spectrum widths • w based on P2 and R2(Zrnić and Mahapatra, 1985)

  16. T1 T2 Algorithm • Compute combined Echo power (N2) • Compute Reflectivity • Legacy PSP algorithm • Determine Significant Returns for Z • Use reflectivity threshold

  17. T1 T2 Algorithm • Compute individual Echo powers (N1, N2) • Determine overlaid echoes • Overlaid echoes do not bias v, but act as noise • Use overlaid threshold • Could use Sachidananda’s overlaid resolution scheme • Determine Significant Returns for v and w • Use velocity and width thresholds

  18. Algorithm Performance Staggered PRT Velocity De-aliasing va1 = 22.58m s-1, va2 = 15.06m s-1, va = 45.17 m s-1

  19. Algorithm Performance

  20. Future Work • Sophisticated GCF • Spectral (Reports 3 and 4) • Others (Regression?) • One-overlaid resolution • Sachidananda and Zrnic, 2003 • Extension beyond ra2 • For T1/T2 = 2/3 up to 2ra1

  21. Part Three Preliminary Case Studies

  22. Case Data • Data acquired with RRDA archive I recorder • Staggered PRT • Custom VCP’s alternating uniform and staggered PRT scans at 3 elevations • Phase Coding • ROC/NSSL VCP’s alternating non-phase-coded and phase-coded scans at 2 elevations • Proposed VCP for R/V Ambiguity Mitigation • Phase coding at lower elevations, staggered PRT at higher elevations (Report 6)

  23. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 02/13/2003 20:58 GMT

  24. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466Recalibrated 02/13/2003

  25. EL = 0.5 deg KTLXVCP 11Needs Split Cut KOUNStaggered 336/466No need for Split Cut va = 28.08 m s-1 va = 31.96 m s-1 02/13/2003

  26. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 02/13/2003

  27. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 336/466 02/13/2003 20:58 GMT

  28. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 336/466 va = 28.08 m s-1 va = 31.96 m s-1 02/13/2003

  29. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 02/13/2003 22:42 GMT

  30. KOUNStaggered 336/466GCF OFF KOUNStaggered 336/466GCF ON KOUNStaggered 336/466GCF ON w/censoring 02/13/2003

  31. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 va = 28.08 m s-1 va = 31.96 m s-1 02/13/2003

  32. KOUNStaggered 336/466GCF OFF KOUNStaggered 336/466GCF ON KOUNStaggered 336/466GCF ON w/censoring 02/13/2003

  33. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 02/13/2003

  34. KOUNStaggered 336/466GCF OFF KOUNStaggered 336/466GCF ON KOUNStaggered 336/466GCF ON w/censoring 02/13/2003

  35. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 336/466 02/13/2003 22:42 GMT

  36. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 336/466 va = 28.08 m s-1 va = 31.96 m s-1 02/13/2003

  37. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 184/276 03/17/2003 21:39 GMT

  38. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 184/276 va = 28.08 m s-1 va = 45.17 m s-1 03/17/2003

  39. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 184/276 03/17/2003

  40. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 184/276 va = 28.08 m s-1 va = 45.17 m s-1 03/17/2003

  41. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 184/276 03/17/2003

  42. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 03/17/2003 21:44 GMT

  43. EL = 0.5 deg KTLXVCP 11 KOUNStaggered 336/466 va = 28.08 m s-1 va = 31.96 m s-1 03/17/2003

  44. EL = 2.5 deg KTLXVCP 11 KOUNStaggered 240/360 03/17/2003 22:44 GMT

  45. EL = 2.5 deg KTLXVCP 11 KOUNStaggered 240/360 va = 28.08 m s-1 va = 34.63 m s-1 03/17/2003

  46. EL = 2.5 deg KTLXVCP 11 KOUNStaggered 240/360 03/17/2003

  47. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 184/276 04/06/2003 04:37 GMT

  48. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 184/276 va = 28.08 m s-1 va = 45.17 m s-1 04/06/2003

  49. 04/06/2003 KOUNLegacy sv computation KOUNR(T2)/R(T1) sv computation

  50. EL = 1.5 deg KTLXVCP 11 KOUNStaggered 240/360 04/06/2003 04:42 GMT

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