Enchanced interference cancellation and telemetry reception in multipath environments with a single paraboic dish antenna using a focal plane array

• US 8,022,860 B1
• Filed: 07/20/2007
• Issued: 09/20/2011
• Est. Priority Date: 07/24/2006
• Status: Expired due to Fees

• Current Assignee: US Government As Represented By The Director National Security Agency
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Vilnrotter, Victor A., Mukai, Ryan
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US11/781,022
• Time in Patent Office: 1,523 Days
• Field of Search: 342/52, 342/58, 342/60, 342 73- 81, 342104-116, 342159-164, 342/175, 342192-197, 342368-384, 342/89, 244 31- 33, 343753-755, 343757-766, 343/772, 343/781.R, 343/782, 343/781.P, 343/781.CA, 343832-840, 343/846, 343878-892, 343/907, 343912-916, 343/700.MS, 343/720, 343725-728, 343/776, 343/779
• US Class Current: 342/60
• CPC Class Codes: G01S 3/72 Diversity systems specially adapted for direction-finding
• CPC Class Codes: H01Q 1/125 Means for positioning
• CPC Class Codes: H01Q 19/17 the primary radiating source comprising two or more radiating elements H01Q19/15, H01Q25/00 take precedence
• CPC Class Codes: H01Q 3/02 using mechanical movement of antenna or antenna system as a whole

Abstract

An Advanced Focal Plane Array (“AFPA”) for parabolic dish antennas that exploits spatial diversity to achieve better channel equalization performance in the presence of multipath (better than temporal equalization alone), and which is capable of receiving from two or more sources within a field-of-view in the presence of multipath. The AFPA uses a focal plane array of receiving elements plus a spatio-temporal filter that keeps information on the adaptive FIR filter weights, relative amplitudes and phases of the incoming signals, and which employs an Interference Cancelling Constant Modulus Algorithm (IC-CMA) that resolves multiple telemetry streams simultaneously from the respective aero-nautical platforms. This data is sent to an angle estimator to calculate the target'"'"'s angular position, and then on to Kalman filters FOR smoothing and time series prediction. The resulting velocity and acceleration estimates from the time series data are sent to an antenna control unit (ACU) to be used for pointing control.

Claims

1. A focal plane array antenna and processing system comprising:

a parabolic dish antenna;

a focal plane array comprising a plurality of focal plane antenna elements in the focal plane of said parabolic dish antenna;

a processing system for reception of multiple telemetry streams simultaneously in the presence of multipath.

2. The focal plane array antenna and processing system according to claim 1, wherein said processing system includes a spatio-temporal filter.

3. The focal plane array antenna and processing system according to claim 2, wherein said spatio-temporal filter comprises a digital FIR filter for executing a constant modulus algorithm with interference cancelling and multiple beamforming.

4. The focal plane array antenna and processing system according to claim 1, wherein said processing system includes a downconverter connected to said focal plane array, a spatio-temporal FIR filter connected to said downconverter, an angle estimator connected to said spatio-temporal FIR filter, and a Kalman filter.

5. The focal plane array antenna and processing system according to claim 1, wherein the plurality of focal plane antenna elements further comprise seven antenna elements.

6. The focal plane array antenna and processing system according to claim 5, wherein the antenna elements of said focal plane array are arranged in a substantially hexagonal geometry.

7. The focal plane array antenna and processing system according to claim 1, wherein said processing system further comprising a spatio-temporal filter for deriving information on adaptive FIR filter weights, relative amplitudes and phases of the signals from said focal plane array.

8. The focal plane array antenna and processing system according to claim 7, further comprising an angle estimator connected to said spatio-temporal filter for computing a target'"'"'s angular position with respect to the antenna'"'"'s pointing axis.

9. A focal plane array antenna system comprising:

a parabolic dish antenna;

a focal plane array comprising a plurality of focal plane antenna elements in the focal plane of said parabolic dish antenna;

a spatio-temporal filter for deriving information on adaptive FIR filter weights, relative amplitudes and phases of the signals from said focal plane array;

an angle estimator connected to said spatio-temporal filter for computing a target'"'"'s angular position with respect to the antenna'"'"'s pointing axis;

a filter in communication with said angle estimator for extracting velocity and acceleration estimates from the time series data;

and an antenna control unit, in communication with said filter, used for pointing control of said parabolic dish antenna.

10. The focal plane array antenna system according to claim 9, wherein the antenna elements of said focal plane array are arranged in a substantially hexagonal geometry.

11. The focal plane array antenna system according to claim 9, wherein said filter for extracting velocity and acceleration estimates from the time series data comprises a Kalman filter.

12. The focal plane array antenna system according to claim 11, wherein said Kalman filter comprises a pair of 3-state Kalman filters.

13. A method of processing telemetry received from a target at a parabolic antenna in the presence of multipath, comprising the steps of:

receiving telemetry at a multi-receiving element radio frequency focal plane array positioned in a focal plane of said parabolic antenna to create a plurality of input signals having spatial diversity;

downconverting each of said plurality of input signals to complex baseband signal components;

combining each of said plurality of complex baseband signal components using adaptive filters and retaining information on the adaptive filter weights, relative amplitudes and phases of the complex baseband signal components;

computing instantaneous estimates of the target'"'"'s angular position with respect to a pointing axis of said parabolic antenna;

producing time series data based on said computed target position estimates; and

predicting angular velocity and acceleration of said target based on said time series data.

14. The method of claim 13, wherein said step of receiving telemetry at said multi-receiving element radio frequency focal plane array further comprises receiving telemetry from two or more sources within the field-of-view of said parabolic antenna.

15. The method of claim 13, further comprising a step of using the extracted angular velocity and acceleration estimates from the time series data to provide pointing control for said parabolic antenna.

16. The method of claim 13, wherein said step of combining each of said plurality of complex baseband signal components using filters further comprises using adaptive Finite Impulse Response (FIR) filters and retaining information on the adaptive FIR filter weights, relative amplitudes and phases of the complex baseband signal components.

17. The method of claim 13, wherein said step of combining each of said plurality of complex baseband signal components using filters further comprises coherently combining.

18. The method of claim 13 for processing telemetry received from multiple targets at a single parabolic antenna in the presence of multipath, wherein said step of receiving telemetry at a multi-receiving element radio frequency focal plane array comprises creating a plurality of input signals from each target each having spatial diversity, and said step of downconverting each of said plurality of input signals comprises downconverting to complex baseband signal components for each of said plurality of input signals, and said step of computing instantaneous estimates comprises computing estimates of each of said targets angular position with respect to a pointing axis of said parabolic antenna.