Phase shifted transmitted signals in a simultaneous dual polarization weather system

• US 7,551,123 B2
• Filed: 03/22/2006
• Issued: 06/23/2009
• Est. Priority Date: 03/22/2006
• Status: Active Grant

• Current Assignee: Enterprise Electronics
• Original Assignee: Enterprise Electronics
• Inventors: Alford, James Larry, Helvin, James Rogers, Stagliano, James J. Jr., Nelson, Dean A.
• Primary Examiner(s): Gregory; Bernarr E
• Application Number:
  US11/386,613
• Publication Number:
  US 20070222661A1
• Time in Patent Office: 1,189 Days
• Field of Search: 342 26 R- 26 D, 342/27, 342/28, 342 82-103, 342/175, 342188-197, 342361-366, 342146-157, 343850-853
• US Class Current: 342/188
• 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 7/285 Receivers
• 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 system for simultaneously propagating dual polarized signals in a polarimetric radar system includes a system for shifting the phase of one of the two signals. The simultaneous dual polarization weather radar transmits signals in both the horizontal and vertical orientations at the same time. Upon reception, the signals in each channel are isolated and a number of standard and polarimetric parameters characterizing atmospheric conditions are determined. The accuracy upon which these parameters can be determined depends partially upon the interference between these two channels. The system and method isolates the vertical and horizontal channels by using the phase information from the signals to minimize the interference.

Claims

1. A radar system, comprising:

a. a sole arbitrary waveform generator configured to generate a first signal and a second signal, said first signal having a different phase from said second signal;

b. a pair of signal mixers, one said signal mixer electrically coupled to an output of said waveform generator and said other mixer electrically coupled to an output of said waveform generator;

c. a local oscillator electrically coupled to said pair of signal mixers such that said first and second signals are heterodyned with a signal from said local oscillator;

d. a pair of amplifiers configured to amplify the output from said pair of signal mixers;

e. a single orthogonal horn and antenna assembly coupled to said pair of amplifiers and configured to simultaneously propagate said amplified and heterodyned first signal in a first plane and said amplified and heterodyned second signal in a second plane angularly rotated from said first plane;

f. a second pair of mixers electrically coupled to and arranged with said orthogonal horn and antenna assembly such that said second pair of mixers receives orthogonally oriented reflectivity signals received from said horn and antenna assembly, wherein each of said second pair of mixers is electrically coupled to said local oscillator such that said second pair of mixers mixes said orthogonally oriented reflectivity signals with said local oscillator signal;

g. a pair of intermediate frequency filters each coupled to one of said second pair of mixers; and

,

h. a receiver coupled to both of said intermediate frequency filters, said receiver including means for resolving the scattering matrix associated with said orthogonally oriented received reflectivity signals and wherein said resolving means is configured to produce polarimetric data from reflectivity signals having a phase of said first signal and reflectivity signals having a phase of said second signal.

2. The radar system of claim 1, wherein said resolving means further comprises means to calculate the phase relationship between the first and second signals in accordance with the equation:

|Ψ

_H−

Ψ

_V|=π

/2.

3. The radar system of claim 1, wherein said arbitrary waveform generator is configured to shift said first signal orthogonally relative to said second signal at random intervals.

4. The radar system of claim 1, wherein said arbitrary waveform generator is configured to generate a first arbitrary waveform comprising said first signal and a second arbitrary waveform comprising said first signal, each waveform formed at an intermediate frequency less than the frequency of said propagated first and second signals, and wherein said waveform generator is further configured such that said first and second arbitrary waveforms are different from one another.

5. The radar system of claim 1, wherein said receiver is further configured to receive said first and second signals from said waveform generator.

6. The radar system of claim 5, wherein said receiver includes means for isolating said first and second reflected signals by comparing said first and second received signals to said first and second signals received from said waveform generator.

7. The radar system of claim 6 wherein:

a. said orthogonal horn and antenna assembly is further configured to receive a first planar signal including a portion of said first reflected signal and a portion of said second reflected signal;

b. said orthogonal horn and antenna assembly is further configured to receive a second planar signal including a portion of said first reflected signal and a portion of said second reflected signal; and

c. said receiver is further configured to calculate an angular rotation of said first and second reflected signal from said first and second plane.

8. A method for processing simultaneous dual polarized signals from a radar system, comprising the steps of:

a. generating horizontal and vertical pulses;

b. shifting said vertical pulse signals relative to said horizontal pulse signals such that said signals have disparate phases;

c. mixing said shifted signals with a local oscillator signal;

d. propagating said mixed vertical and horizontal pulse signals through an orthogonal horn and antenna assembly into space;

e. receiving a first signal from a reflected source, said first received signal including a portion of said mixed vertical pulse signal and a portion of a said mixed horizontal pulse signal, wherein said vertical pulse signal is shaped differently than said horizontal pulse signal;

f. receiving a second signal from a reflected source, said second received signal including a portion of said first mixed vertical pulse signal and a portion of said mixed horizontal pulse signal; and

g. decoding said first and second received signals by comparing said first mixed vertical pulse signal and said mixed horizontal pulse with said first and second received signals.

9. The method of claim 8, further comprising the step of comparing said second transmitted signal with said first and second received signals.

10. The method of claim 9, further comprising receiving said first and second received signals simultaneously.

11. The method of claim 8 wherein said first transmitted signal is orthogonal to said second transmitted signal.

12. The method of claim 11, wherein said first transmitted signal and said first received signal are located in a first plane and said second transmitted signal and said second received signal are located in a second plane.

13. The method of claim 12, wherein said first plane is orthogonal to said second plane.

14. A radar system comprising:

a. a sole local oscillator configured to generate a low power signal;

b. an amplifier configured to amplify said low power signal to a high power signal;

c. a power divider configured to split said high power signal into a first signal and a second signal;

d. a high powered shifting device configured to shift said first signal;

e. an orthogonal horn and antenna assembly coupled to said power divider and configured to simultaneously propagate said first signal in a first plane and said second signal in a second plane angularly rotated from said first plane, wherein said first plane is orthogonal to said second plane; and

f. a second pair of mixers electrically coupled to and arranged with said orthogonal horn and antenna assembly such that said second pair of mixers receives orthogonally oriented reflectivity signals received from said horn and antenna assembly, wherein each of said second pair of mixers is electrically coupled to said local oscillator such that said second pair of mixers mixes said orthogonally oriented reflectivity signals with said local oscillator signal;

g. a pair of intermediate frequency filters each coupled to one of said second pair of mixers; and

,

h. a receiver coupled to both of said intermediate frequency filters, said receiver including means for resolving the scattering matrix associated with said orthogonally oriented received reflectivity signals and wherein said resolving means is configured to receive a first reflected signal having the shape of said first signal and a second reflected signal having a shape of said second signal.

15. The radar system of claim 14, wherein said receiver further comprises means to calculate the phase relationship between the first and second signals in accordance with the equation:

|∩

_H−

∩

_V|=π

/2.

16. The radar system of claim 14, wherein said local oscillator is configured to shift said first amplified signal from said second amplified signal.

17. The radar system of claim 14, further comprising a second high powered shifting device configured to shift said second amplified signal wherein said oscillator generates said first and second signals at an intermediate frequency less than the frequency of said propagated first and second signals.

18. The radar system of claim 14, wherein said first and second phase shifts are sent to said receiver.

19. The radar system of claim 14, wherein said receiver is coupled to said high powered shifting and further configured to receive said phase shifts from said high powered shifting device.

20. The radar system of claim 19, wherein said receiver isolates said first and second reflected signals by comparing said first and second received signals to said phase shift.

21. The radar system of claim 20 wherein:

a. said orthogonal horn and antenna assembly is further configured to receive a first planar signal including a portion of said first reflected signal and a portion of said second reflected signal;

b. said orthogonal horn and antenna assembly is further configured to receive a second planar signal including a portion of said first reflected signal and a portion of said second reflected signal; and

c. said receiver is further configured to calculate an angular rotation of said first and second reflected signal from said first and second plane.

22. A method for propagating simultaneous dual polarized signals from a radar system, comprising the steps of:

a. generating a first signal and a second signal;

b. shifting said first signal such that said first signal and said second signal are phased differently;

c. heterodyning said first and second signals with a local oscillator; and

,

d. propagating said first signal on a first plane and said second signal on a second plane through an orthogonal horn and antenna assembly into space, wherein said second plane is rotated from said first plane.

23. The method of claim 22, wherein said first plane is orthogonal to said second plane.

24. The method of claim 22, further comprising propagating said first and second signals simultaneously.

25. The method of claim 22 wherein said first signal is orthogonal to said second signal.

26. The method of claim 25, wherein said first signal and a first received signal are located in said first plane and said second signal and a second received signal are located in said second plane.

27. The method of claim 26, wherein said first plane is orthogonal to said second plane.

28. The method of claim 27, further comprising:

a. decoding said first and second received signals by comparing said first signal with said first and second received signals,

b. wherein said first received signal includes a portion of a first transmitted signal and a portion of a second transmitted signal; and

c. said second received signal includes a portion of said first transmitted signal and a portion of said second transmitted signal.

29. The method of claim 28, further comprising the step of comparing said second transmitted signal with said first and second received signals.

30. The method of claim 29, further comprising receiving said first and second received signals simultaneously.