Polarization and frequency diverse radar system for complete polarimetric characterization of scatterers with increased scanning speed

• US 7,355,546 B2
• Filed: 01/03/2006
• Issued: 04/08/2008
• Est. Priority Date: 01/03/2006
• Status: Expired due to Fees

• Current Assignee: Advanced Radar Corp. (New Port Group Holdings, Inc.)
• Original Assignee: Advanced Radar Corp. (New Port Group Holdings, Inc.)
• Inventors: Randall, Mitch
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US11/325,262
• Publication Number:
  US 20070152867A1
• Time in Patent Office: 826 Days
• Field of Search: 342/26.R, 342/26.A, 342/26.B, 342/26.C, 342/26.D, 342/104, 342/188, 342/189, 342/195
• US Class Current: 342/26.00R
• CPC Class Codes: G01S 13/426 Scanning radar, e.g. 3D radar G01S13/66 takes precedence
• CPC Class Codes: G01S 13/951 ground based
• CPC Class Codes: G01S 7/024 using polarisation effects in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

A method and apparatus is provided, whereby a scanning, polarization and frequency diverse radar system measures the complete polarimetric characterization of weather targets without loss of scanning speed and without an additional ambiguity in the Doppler velocity beyond that given by Nyquist'"'"'s sampling theorem. In one embodiment, a linear combination of a horizontally and a vertically polarized signal are transmitted at a predetermined first frequency. Cotemporaneously or nearly cotemporaneously with the transmitted signal of the first frequency, a horizontally polarized signal is transmitted at a predetermined second frequency. Horizontal and vertical receive channels receive echoes at the predetermined first frequency to determine, but not limited to determine, the co-polar elements of the scattering matrix. Horizontal and vertical receive channels receive echoes at the predetermined second frequency to determine, but not limited to determine, the cross-polar elements of the polarization matrix. The predetermined first and second frequencies are selected to maximize isolation yet allow practical implementation.

Claims

1. A polarization diverse radar for estimating scattering matrix parameters of scatterers in a volume, comprising:

a transmitter operating at a predetermined first frequency and feeding an antenna to produce a radiated signal comprising a linear combination of a first polarization, and a second polarization orthogonal to said first polarization;

a transmitter operating at a predetermined second frequency and feeding an antenna to produce a radiated signal at said first polarization;

a plurality of receivers, tuned to said predetermined first frequency, and an antenna to receive echo signals of a plurality of substantially orthogonal polarizations returned from scatterers in a volume illuminated by said radiated signal at said predetermined first frequency; and

a plurality of receivers, tuned to said predetermined second frequency, and an antenna to receive echo signals of a plurality of substantially orthogonal polarizations returned from scatterers in a volume illuminated by said radiated signal at said predetermined second frequency.

2. The polarization diverse radar of claim 1, wherein a processor system uses said echo signals to estimate scattering matrix parameters for said scatterers in a volume.

3. The polarization diverse radar of claim 1, wherein a processor system uses said echo signals to estimate the radial velocity of said scatterers in a volume.

4. The polarization diverse radar of claim 1, wherein a processor system uses said echo signals, samples of said transmitted signal at a predetermined first frequency, and samples of said transmitted signal at a predetermined second frequency to estimate the radial velocity of said scatterers in a volume.

5. The polarization diverse radar of claim 1, wherein a processor system uses said echo signals, samples of said transmitted signal at a predetermined first frequency, and samples of said transmitted signal at a predetermined second frequency to estimate scattering matrix parameters for said scatterers in a volume.

6. A method of estimating the radial velocity of scatterers in a volume, comprising:

Applying a covariance algorithm to a linear combination of said echo signals received at a predetermined first frequency to obtain a first estimate of the first moment of echo statistics of said scatterers in a volume;

Applying a covariance algorithm to a linear combination of said echo signals received at a predetermined second frequency to obtain a first estimate of the first moment of echo statistics of said scatterers in a volume; and

Applying a weighted average of said first estimate and said second estimate of the first moment of echo statistics of said scatterers in a volume to compute a velocity estimate of said scatterers in a volume.

7. A method of estimating the radial velocity of scatterers in a volume, comprising:

Correcting incoherent echo signals received at said predetermined first frequency using samples of said transmitted signal at said predetermined first frequency, to obtain coherent echo signals received at said predetermined first frequency;

Applying a covariance algorithm to a linear combination of said coherent echo signals received at a predetermined first frequency to obtain a first estimate of the first moment of echo statistics of said scatterers in a volume;

Correcting incoherent echo signals received at said predetermined second frequency using samples of said transmitted signal at said predetermined second frequency, to obtain coherent echo signals received at said predetermined second frequency;

Applying a covariance algorithm to a linear combination of said coherent echo signals received at a predetermined second frequency to obtain a second estimate of the first moment of echo statistics of said scatterers in a volume; and

Applying a weighted average of said first estimate and said second estimate of the first moment of echo statistics of said scatterers in a volume to compute a velocity estimate of said scatterers in a volume.

8. A method of estimating scattering matrix parameters of scatterers in a volume, comprising:

Computing predetermined first frequency co-polar powers P_HH1 and P_VV1 using said echo signals received at said predetermined first frequency;

Estimating differential reflectivity (Z_DR) from said predetermined first frequency co-polar powers P_VV1 and P_HH1;

Computing predetermined second frequency co-polar power P_HH2 and cross-polar power P_HV2 using said echo signals received at said predetermined second frequency;

Estimating linear depolarization (L_DR) from said predetermined second frequency co-polar power P_HH2 and cross-polar power P_HV2.

9. The method of claim 8, wherein the reflectivity of scatterers in a volume is estimated from a weighted average of said predetermined first frequency co-polar power P_HH1 and said predetermined second frequency co-polar power P_HH2.

10. The method of claim 8, wherein differential phase (Φ

_DP) of scatterers in a volume is estimated from said echo signals received at said predetermined first frequency.

11. The method of claim 8, wherein correlation of scatterers in a volume is estimated from said echo signals.

12. The method of claim 8, wherein correlation of scatterers in a volume is estimated from said echo signals and said samples of the transmitted signals.