• Cho, J. Y. N., 2005: Multi-PRI signal processing for the Terminal Doppler Weather Radar. Part II: Range–velocity ambiguity mitigation. J. Atmos. Oceanic Technol., 22, 15071519, https://doi.org/10.1175/JTECH1805.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chu, D. C., 1972: Polyphase codes with good periodic correlation properties. IEEE Trans. Inf. Theory, 18, 531532, https://doi.org/10.1109/TIT.1972.1054840.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Doviak, R. J., and D. S. Zrnić, 2006: Doppler Radar and Weather Observations. 2nd ed. Academic Press, 562 pp.

  • Fang, M., R. J. Doviak, and V. Melnikov, 2004: Spectrum width measured by WSR-88D: Error sources and statistics of various weather phenomena. J. Atmos. Oceanic Technol., 21, 888904, https://doi.org/10.1175/1520-0426(2004)021<0888:SWMBWE>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Frush, C., R. J. Doviak, M. Sachidananda, and D. S. Zrnić, 2002: Application of the SZ phase code to mitigate range–velocity ambiguities in weather radars. J. Atmos. Oceanic Technol., 19, 413430, https://doi.org/10.1175/1520-0426(2002)019<0413:AOTSPC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Galati, G., and G. Pavan, 1995: Computer simulation of weather radar signals. Simul. Pract. Theory, 3, 1744, https://doi.org/10.1016/0928-4869(95)00009-I.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Laird, B. G., 1981: On ambiguity resolution by random phase processing. 20th Conf. on Radar Meteorology, Boston, MA, Amer. Meter. Soc., 327–331.

  • Mead, J. B., and A. L. Pazmany, 2019: Quadratic phase coding for high duty cycle radar operation. J. Atmos. Oceanic Technol., 36, 957969, https://doi.org/10.1175/JTECH-D-18-0108.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sachidananda, M., and D. S. Zrnić, 1999: Systematic phase codes for resolving range overlaid signals in a Doppler weather radar. J. Atmos. Oceanic Technol., 16, 13511363, https://doi.org/10.1175/1520-0426(1999)016<1351:SPCFRR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sachidananda, M., D. S. Zrnić, R. J. Doviak, and S. Torres, 1998: Signal design and processing techniques for WSR-88D ambiguity resolution: Part 2. NOAA/NSSL Rep., 105 pp., www.nssl.noaa.gov/publications/rv-ambiguity/Report_2.pdf.

  • Siggia, A., 1983: Processing phase coded radar signals with adaptive digital filters. 21st Conf. on Radar Meteorology, Edmonton, AB, Canada, Amer. Meteor. Soc., 163–166.

  • Torres, S. M., and D. Zrnić, 2006: Evolution of the SZ-2 Algorithm. Part 10, Signal design and processing techniques for WSR-88D ambiguity resolution, NOAA/NSSL Rep., 71 pp., https://cimms.ou.edu/~torres/Documents/NSSL%20Ambiguity%20Report%20-%20Part%2010.pdf.

  • Zrnić, D. S., 1975: Simulation of weather like Doppler spectra and signals. J. Appl. Meteor., 14, 619620, https://doi.org/10.1175/1520-0450(1975)014<0619:SOWDSA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zrnić, D. S., 1979: Estimation of spectral moments for weather echoes. IEEE Trans. Geosci. Electron., 17, 113128, https://doi.org/10.1109/TGE.1979.294638.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zrnić, D. S., and P. Mahapatra, 1985: Two methods of ambiguity resolution in pulsed Doppler weather radars. IEEE Trans. Aerosp. Electron. Syst., AES-21, 470483, https://doi.org/10.1109/TAES.1985.310635.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zrnić, D. S., and A. V. Ryzhkov, 1999: Polarimetry for weather surveillance radars. Bull. Amer. Meteor. Soc., 80, 389406, https://doi.org/10.1175/1520-0477(1999)080<0389:PFWSR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 172 172 34
Full Text Views 58 58 5
PDF Downloads 73 73 7

Phase Codes for Mitigating Ambiguities in Range and Velocity

View More View Less
  • 1 NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma
  • | 2 School of Meteorology, University of Oklahoma, Norman, Oklahoma
  • | 3 School of Electrical and Computer Engineering, University of Oklahoma, Norman, Oklahoma
  • | 4 Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

We review cubic phase codes for mitigating ambiguities in range and velocity before introducing two specific codes. The two have periodicities of 5 and 7 samples for both the transmitted and the modulation code sequences. The short periods are suitable for generating codes of arbitrary length starting with about 15. We abbreviate the two codes with L5 and L7 and describe generation of the codes starting with kernels (i.e., minimum length sequences that repeat to generate the codes of desired lengths). The L5 modulation code produces 5 spectral replicas of the coded signal and the L7 produces 7. We apply the L7 code to a sinusoid and reveal spectra of the modulated signals from several ambiguous range intervals. Through simulation, we show application to weatherlike signals and construct examples whereby two weather signals and ground clutter are overlaid. Using theory, we define the operating region of the codes in the signal parameter space. The region covers a wide range of overlaid returned powers and spectrum widths; it is obtained from simulations involving the L codes and the SZ(8/64) code. The technique is effective in distinguishing the returns from two trip regions separated by no more than L − 2 ambiguous range intervals and reconstructing the corresponding spectral moments. The L5 and L7 codes protect from trip returns up to the fifth and seventh, making them suitable for short-wavelength (3 and 5 cm) radars as their PRTs must be relatively short to accommodate the expected spread of velocities in storms.

SIGNIFICANCE STATEMENT

We propose improved phase codes to mitigate the ambiguities in range for pulsed Doppler weather radars. The currently implemented code SZ(8/64) on the WSR-88D resolves signals from up to 4 range ambiguous intervals 4ra (typically 460 km). The proposed codes extend this to 5ra or 7ra, suitable for scans at elevation angles ≤ 0°. More significant improvements are for radars with shorter wavelengths, like the Terminal Doppler Weather Radar because their ra values are much shorter than on the WSR-88D. The new codes enable equal optimum retrieval (in errors and region of recovery) of Doppler velocities from each ra; the SZ(8/64) yields optimum performance for the first, second, and fourth ra intervals. The next step is their demonstration/validation on weather radars.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Dusan Zrnić, dusan.zrnic@noaa.gov

Abstract

We review cubic phase codes for mitigating ambiguities in range and velocity before introducing two specific codes. The two have periodicities of 5 and 7 samples for both the transmitted and the modulation code sequences. The short periods are suitable for generating codes of arbitrary length starting with about 15. We abbreviate the two codes with L5 and L7 and describe generation of the codes starting with kernels (i.e., minimum length sequences that repeat to generate the codes of desired lengths). The L5 modulation code produces 5 spectral replicas of the coded signal and the L7 produces 7. We apply the L7 code to a sinusoid and reveal spectra of the modulated signals from several ambiguous range intervals. Through simulation, we show application to weatherlike signals and construct examples whereby two weather signals and ground clutter are overlaid. Using theory, we define the operating region of the codes in the signal parameter space. The region covers a wide range of overlaid returned powers and spectrum widths; it is obtained from simulations involving the L codes and the SZ(8/64) code. The technique is effective in distinguishing the returns from two trip regions separated by no more than L − 2 ambiguous range intervals and reconstructing the corresponding spectral moments. The L5 and L7 codes protect from trip returns up to the fifth and seventh, making them suitable for short-wavelength (3 and 5 cm) radars as their PRTs must be relatively short to accommodate the expected spread of velocities in storms.

SIGNIFICANCE STATEMENT

We propose improved phase codes to mitigate the ambiguities in range for pulsed Doppler weather radars. The currently implemented code SZ(8/64) on the WSR-88D resolves signals from up to 4 range ambiguous intervals 4ra (typically 460 km). The proposed codes extend this to 5ra or 7ra, suitable for scans at elevation angles ≤ 0°. More significant improvements are for radars with shorter wavelengths, like the Terminal Doppler Weather Radar because their ra values are much shorter than on the WSR-88D. The new codes enable equal optimum retrieval (in errors and region of recovery) of Doppler velocities from each ra; the SZ(8/64) yields optimum performance for the first, second, and fourth ra intervals. The next step is their demonstration/validation on weather radars.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Dusan Zrnić, dusan.zrnic@noaa.gov
Save