Retrieval of Parameters in Networked Radar Environments

• US 20080012755A1
• Filed: 07/13/2006
• Published: 01/17/2008
• Est. Priority Date: 07/13/2006
• Status: Active Grant

• Current Assignee: Colorado State University Research Foundation
• Original Assignee: Colorado State University Research Foundation
• Inventors: Venkatachalam, Chandrasekaran, Lim, Sang Hun
• Granted Patent: US 7,518,544 B2
• Time in Patent Office: Days
• US Class Current: 342/26R
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/95 for meteorological use
• 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

Radar beams are generated with radars disposed at different positions within an environment that attenuates at least a portion of one of the radar beams. A measured reflectivity of the environment is determined along a path of each of the radar beams. An intrinsic reflectivity is determined from different volume elements within the environment from the measured reflectivity.

Claims

1. A method of operating a radar network, the method comprising:

generating respective radar beams with each of a plurality of radars disposed at different positions within an environment;

determining a respective measured reflectivity of the environment along a respective path of each of the respective radar beams from the generated respective radar beams, wherein the respective measured reflectivity is attenuated along at least a portion of the respective path of at least one of the respective radar beams; and

determining an intrinsic reflectivity for different volume elements within the environment from the respective measured reflectivity along the respective path of each of the respective radar beams.

2. The method recited in claim 1 wherein determining the intrinsic reflectivity for different volume elements comprises:

identifying the different volume elements;

retrieving an estimate of the intrinsic reflectivity for each of the different volume elements;

calculating a cost function defined in terms of the estimate of the intrinsic reflectivity of the different volume elements; and

varying the estimate to find an extremum of the cost function.

3. The method recited in claim 2 wherein the extremum of the cost function is a local minimum of the cost function.

4. The method recited in claim 2 wherein retrieving the estimate of the intrinsic reflectivity of each of the different volume elements comprises:

setting an initial seed value of the estimate of the intrinsic reflectivity for a selected one of the volume elements; and

retrieving the estimate of the intrinsic reflectivity for a remainder of the volume elements from the initial seed value and from the measured reflectivity of the environment along the respective path of a selected one of the radar beams.

5. The method recited in claim 4 wherein calculating the cost function comprises:

retrieving an estimate of a specific attenuation along the respective path of the selected one of the radar beams from the initial seed value and from the measured reflectivity of the environment along the respective path of the selected one of the radar beams; and

retrieving an estimate of a specific attenuation along the respective paths of the remainder of the radar beams from the seed value and from the retrieved estimate of the intrinsic reflectivity for the remainder of the volume elements.

6. The method recited in claim 5 wherein the cost function is

$\delta$





k ≡

1 N 

∑

i = 1 N 



∑

radars 



α

^ h 

( V i ) - α

_ h 

( V i ) 

α

_ h 

( V i ) / ∑

j = 1 N 



α

_ h 

( V j ) ,

where N is the number of different volumes along the respective path of the selected one of the radar beams, {circumflex over (α

)}_h(V_i) is the retrieved estimate of the specific attenuation along the respective path of a respective one of the radars at volume element V_i, and α

_h(V_i) is a mean of {circumflex over (α

)}_h(V_i) over the plurality of radars.

7. The method recited in claim 1 wherein the different volume elements are grouped into a plurality of sets of common volume elements, each set of common volume elements comprising different volume elements disposed along the respective paths of the respective radar beams at an approximately common spatial position within the environment.

8. The method recited in claim 7 wherein each of the different volume elements comprised by each set of common volume elements has substantially the same spatial volume.

9. The method recited in claim 1 wherein at least two of the respective radar beams have different frequencies.

10. The method recited in claim 1 wherein at least one of the respective radar beams has an X-band frequency.

11. The method recited in claim 1 further comprising:

moving a physical position of at least one of the plurality of radars; and

repeating the steps of generating respective radar beams, determining the respective measured reflectivity, and determining the intrinsic reflectivity after moving the physical position.

12. A networked-radar evaluation system comprising:

a communications device;

a storage device;

a processor in communication with the communications device and with the storage device; and

a memory coupled with the processor, the memory comprising a computer-readable medium having a computer-readable program embodied therein for directing operation of the processing system to retrieve an intrinsic reflectivity from an environment, the computer-readable program comprising;

instructions for receiving, with the communications device, a respective measured reflectivity of the environment along a respective path of each of a plurality of radar beams generated from respective ones of a plurality of radars disposed at different positions within the environment, wherein the respective measured reflectivity is attenuated along at least a portion of the respective path of at least one of the respective radar beams; and

instructions for determining, with the processor, the intrinsic reflectivity for different volume elements within the environment from the respective measured reflectivity along the respective path of each of the plurality of radar beams.

13. The networked-radar evaluation system recited in claim 12 wherein the instructions for determining the intrinsic reflectivity for different volume elements comprises:

instructions for identifying the different volume elements;

instructions for retrieving an estimate of the intrinsic reflectivity for each of the different volume elements;

instructions for calculating a cost function defined in terms of the estimate of the intrinsic reflectivity of the different volume elements; and

instructions for varying the estimate to find an extremum of the cost function.

14. The networked-radar evaluation system recited in claim 13 wherein the extremum of the cost function is a local minimum of the cost function.

15. The network-radar evaluation system recited in claim 13 wherein the instructions for retrieving the estimate of the intrinsic reflectivity of each of the different volume elements comprises:

instructions for setting an initial seed value of the estimate of the intrinsic reflectivity for a selected one of the volume elements; and

instructions for retrieving the estimate of the intrinsic reflectivity for a remainder of the volume elements from the initial seed value and from the measured reflectivity of the environment along the respective path of a selected one of the radar beams.

16. The networked-radar evaluation system recited in claim 15 wherein the instructions for calculating the cost function comprise:

instructions for retrieving an estimate of a specific attenuation along the respective path of the selected one of the radar beams from the initial seed value and from the measured reflectivity of the environment along the respective path of the selected one of the radar beams; and

instructions for retrieving an estimate of a specific attenuation along the respective paths of the remainder of the radar beams from the seed value and from the retrieved estimate of the intrinsic reflectivity for the remainder of the volume elements.

17. The networked-radar evaluation system recited in claim 16 wherein the cost function is

$\delta$





k ≡

1 N 

∑

i = 1 N 



∑

radars 



α

^ h 

( V i ) - α

_ h 

( V i ) 

α

_ h 

( V i ) / ∑

j = 1 N 



α

_ h 

( V j ) ,

where N is the number of different volumes along the respective path of the selected one of the radar beams, {circumflex over (α

)}_h(V_i) is the retrieved estimate of the specific attenuation along the respective path of a respective one of the radars at volume element V_i, and α

_h(V_i) is a mean of {circumflex over (α

)}_h(V_i) over the plurality of radars.

18. The networked-radar evaluation system recited in claim 12 wherein the different volume elements are grouped into a plurality of sets of common volume elements, each set of common volume elements comprising different volume elements disposed along the respective paths of the respective radar beams at an approximately common spatial position within the environment.

19. The networked-radar evaluation system recited in claim 18 wherein each of the different volume elements comprised by each set of common volume elements has substantially the same spatial volume.

20. The networked-radar evaluation system recited in claim 12 wherein at least two of the respective radar beams have different frequencies.

21. The networked-radar evaluation system recited in claim 12 wherein at least one of the respective radar beams has an X-band frequency.

22. A radar network comprising:

a plurality of radars disposed at different positions within an environment; and

a computational unit interfaced with the plurality of radars, the computational unit having instructions to determine an intrinsic reflectivity for different volume elements within the environment from a respective measured reflectivity along a respective path of each of a plurality of respective radar beams, wherein the respective measured reflectivity is attenuated along at least a portion of the respective path of at least one of the respective radar beams.

23. The radar network recited in claim 22 wherein at least two of the respective radar beams have different frequencies.

24. The radar network recited in claim 22 wherein at least one of the respective radar beams has an X-band frequency.

25. The radar network recited in claim 22 wherein the plurality of radars are disposed on cellular-telephone towers.

26. The radar network recited in claim 22 wherein at least one of the radars is in motion relative to another of the radars.

27. The radar network recited in claim 22 wherein at least one of the radars is disposed on a moving vehicle.

28. The radar network recited in claim 22 wherein the computational unit further has instructions to determine a velocity from Doppler information embodied in the respective measured reflectivity along the respective path of each of the plurality of respective radar beams.

29. The radar network recited in claim 22 wherein the instructions to determine the intrinsic reflectivity comprise:

instructions for identifying the different volume elements;

instructions for retrieving an estimate of the intrinsic reflectivity for each of the different volume elements;

instructions for calculating a cost function defined in terms of the estimate of the intrinsic reflectivity of the different volume elements; and

instructions for varying the estimate to find an extremum of the cost function.

30. The radar network recited in claim 29 wherein the instructions for retrieving the estimate of the intrinsic reflectivity of each of the different volume elements comprise:

instructions for setting an initial seed value of the estimate of the intrinsic reflectivity for a selected one of the volume elements; and

instructions for retrieving the estimate of the intrinsic reflectivity for a remainder of the volume elements from the initial seed value and from the measured reflectivity along the respective path of a selected one of the radar beams.

31. The radar network recited in claim 30 wherein the instructions for calculating the cost function comprise:

instructions for retrieving an estimate of a specific attenuation along the respective path of the selected one of the radar beams from the initial seed value and from the measured reflectivity along the respective path of the selected one of the radar beams; and

instructions for retrieving an estimate of a specific attenuation along the respective paths of the remainder of the radar beams from the seed value and from the retrieved estimate of the intrinsic reflectivity for the remainder of the volume elements.

32. The radar network recited in claim 31 wherein the cost function is

$\delta$





k ≡

1 N 

∑

i = 1 N 



∑

radars 



α

^ h 

( V i ) - α

_ h 

( V i ) 

α

_ h 

( V i ) / ∑

j = 1 N 



α

_ h 

( V j ) ,

where N is the number of different volumes along the respective path of the selected one of the radar beams, {circumflex over (α

)}_h(V_i) is the retrieved estimate of the specific attenuation along the respective path of a respective one of the radars at volume element V_i, and α

_h(V_i) is a mean of {circumflex over (α

)}_h(V_i) over the plurality of radars.