SYSTEMS AND METHODS FOR CALIBRATING DUAL POLARIZATION RADAR SYSTEMS

• US 20140210661A1
• Filed: 01/31/2013
• Published: 07/31/2014
• Est. Priority Date: 04/07/2011
• Status: Active Grant

• Current Assignee: Cartwright R. Darrin, John R. Ellis Jr, Mrinal Singh Balaji, William H. Walker
• Original Assignee: John R. Ellis Jr
• Inventors: Balaji, Mrinal Singh, Ellis, John R. Jr., Cartwright, R. Darrin, Walker, William H.
• Granted Patent: US 9,261,583 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: G01S 13/95 for meteorological use
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: G01S 7/4004 of parts of a radar system
• CPC Class Codes: G01S 7/4021 of receivers
• CPC Class Codes: G01S 7/411 Identification of targets based on measurements of radar reflectivity G01S7/415 takes precedence
• 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 dual polarization radar system is calibrated based on real-time data measurements, such as measured horizontal and vertical reflectivities, Z_H and Z_V. In this regard, the radar system analyzes the reflected power measurements to identify which measurements are associated with reflections from a respective spherical object. Using such measurements, the system determines a system differential reflectivity value, and combines such value with reflected power measurements for calibration. Since the calibration is based on real-time data measurements, the calibration process may run simultaneously with the collection of weather data. Thus, it is unnecessary to suspend weather monitoring activities in order to perform the calibration, and the calibration can be run as often as is desired without interfering with such weather monitoring activities. Further, the calibration process is immune to the weather events within range of the radar system. Accordingly, it is possible for the calibration to be performed at any time and without interfering with the weather monitoring activities regardless of the types of weather events occurring within the vicinity of the radar system.

Claims

1. A dual polarization radar system, comprising:

memory;

a transmission system configured to wirelessly transmit pulses;

a receive system configured to store, in the memory, measurement data indicative of returns from the transmitted pulses, the measurement data defining a plurality of bins comprising power values indicative of the returns; and

logic configured to identify which of the bins are indicative of returns from spherical objects, wherein the logic is further configured to calibrate the dual polarization radar system based on the identified bins.

2. The dual polarization radar system of claim 1, wherein each of the pulses comprises a horizontally polarized waveform and a vertically polarized waveform.

3. The dual polarization radar system of claim 1, wherein each of the pulses comprises a first waveform and a second waveform, and wherein the first and second waveforms have polarization states perpendicular to each other.

4. The dual polarization radar system of claim 3, wherein the logic is configured to calculate, for each of the identified bins, a difference between a reflectivity value for the first waveform and a reflectivity value for the second waveform. The dual polarization radar system of claim 3, wherein the logic is configured to calculate, for each of the identified bins, a difference between a reflectivity value for the first receive channel and a reflectivity value for the second receive channel.

5. The dual polarization radar system of claim 1, wherein the logic is configured to determine a system differential reflectivity value based on the identified bins and to combine the system differential reflectivity value with at least one differential reflectivity value measured by the receive system.

6. The dual polarization radar system of claim 5, wherein each of the pulses comprises a first waveform and a second waveform, wherein the logic is configured to define a histogram of calculated differences between reflectivity values of the identified bins for the first waveform and vertical reflectivity values of the identified bins for the second waveform.

7. The dual polarization radar system of claim 6, wherein the logic is configured to identify a peak of the histogram and to determine the system differential reflectivity value based on the identified peak.

8. The dual polarization radar system of claim 1, wherein the plurality of bins comprise phase angle values for the returns, wherein the logic is configured to determine a system differential phase angle value based on the phase angle values of the plurality of bins, and wherein the logic is configured to identify which of the plurality of bins are indicative of returns from spherical objects based on the system differential phase angle value.

9. The dual polarization radar system of claim 8, wherein the logic is configured to define a histogram of calculated differences between the phase angle values for the returns.

10. The dual polarization radar system of claim 9, wherein the logic is configured to identify a peak of the histogram and to identify which of the plurality of bins are indicative of returns from spherical objects based on the identified peak.

11. A method for use in a dual polarization radar system, comprising:

wirelessly transmitting pulses;

storing, in memory, measurement data indicative of returns from the transmitted pulses, the measurement data defining bins comprising reflectivity values indicative of the returns;

identifying a plurality of the bins that are indicative of returns from spherical objects; and

calibrating the dual polarization radar system based on the identifying.

12. The method of claim 11, wherein each of the pulses comprises a first waveform and a second waveform, and wherein the first and second waveforms have polarization states perpendicular to each other.

13. The method of claim 11, wherein each of the pulses comprises a first waveform and a second waveform, wherein the method further comprises calculating for at least one of the bins a difference between a reflectivity value for the first waveform and a reflectivity value for the second waveform, and wherein the identifying is based on the calculating.

14. The method of claim 11, further comprising determining a system differential reflectivity value based on the identified bins, wherein the calibrating comprises combining the system differential reflectivity value with at least one differential reflectivity value measured by the dual polarization radar system.

15. The method of claim 14, wherein each of the pulses comprises a first waveform and a second waveform, and wherein the method further comprises defining a histogram of calculated differences between reflectivity values of the identified bins for the first waveform and vertical reflectivity values of the identified bins for the second waveform.

16. The method of claim 15, further comprising identifying a peak of the histogram, wherein the identifying the plurality of the bins is based on the peak.

17. The method of claim 11, wherein the bins defined by the measurement data comprise phase angle values for the returns, wherein the method further comprises determining a system differential phase angle value based on the phase angle values for the returns, and wherein the identifying is based on the system differential phase angle value.

18. The method of claim 17, further comprising defining a histogram of calculated differences between the phase angle values for the returns.

19. The method of claim 18, further comprising identifying a peak of the histogram, wherein the determining is based on the identified peak.

20. A method for use in a dual polarization radar system, comprising:

wirelessly transmitting pulses;

measuring returns from the transmitted pulses thereby providing a plurality of measurements;

storing, in memory, data indicative of the measurements;

determining, based on the data, whether each of the measurements is indicative of a respective spherical object;

identifying a plurality of the measurements indicative of spherical objects based on the determining; and

calibrating the dual polarization radar system based on the identifying.

21. The method of claim 20, wherein each of the pulses comprises a first waveform and a second waveform, and wherein the method further comprises:

calculating, for the identified measurements, differences between reflectivity values for the first waveform and reflectivity values for the second waveform; and

determining a system differential reflectivity value based on the calculating, wherein the calibrating comprises combining the system differential reflectivity value with the at least one differential reflectivity value measured by the dual polarization radar system.