# US 6,720,918 B2 · Antenna distortion estimation and compensation

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- Number: US 6,720,918 B2
- Document ID: US6720918B2
- Status: Granted
- Kind: B2
- Application number: 10/244,944
- Filed: 2002-09-17
- Published: 2004-03-18
- Granted: 2004-04-13
- Earliest claimed: 2002-09-17
- Assignees: Space Systems/Loral, Inc.
- Inventors: Keith Reckdahl; Lawrence McGovern
- Web page: https://patentgrep.com/patent/US6720918B2

## CPC

- H01Q 1/02: Arrangements for de-icing; Arrangements for drying-out {; Arrangements for cooling; Arrangements for preventing corrosion}
- H01Q 1/288: {Satellite antennas}
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)

## Abstract

A thermal distortion estimation system for delivering thermal time varying distortion of various spacecraft antenna is provided which includes a measurement signal outage indicator and a storage device containing time varying distortion data. A signal is generated indicating an outage for the system received by the spacecraft and then a generated time varying distortion of the system from a previous measurement history to predict the error resulting from the thermal distortion is employed to estimate the error.

## Claims

### Claim 1

A thermal distortion estimation system for determining thermal time varying distortion of spacecraft antenna comprising:
a) an error position sensor which determines the time varying distortion of the antenna;
b) a sensor that determines a signal outage for the system; and
c) a generated time varying distortion of the system from a previous measurement history.

### Claim 2

A system for estimating the thermal time varying distortion of spacecraft antenna comprising:
a) a measurement signal outage indicator; and
b) a storage device which contains time varying distortion data.

### Claim 3 (depends on 2)

The system as defined in claim 2 wherein said outage sensor measures the magnitude of a signal to detect an outage.

### Claim 4 (depends on 2)

The system as defined in claim 2 wherein said system may be mathematically expressed as a Fourier series for which the constants are determined by empirical data.

### Claim 5 (depends on 4)

The system as defined in claim 4 wherein said empirical data comprises historical thermal distortion data compiled over a period of a year.

### Claim 6 (depends on 5)

The system as defined in claim 5 wherein said data is concentrated to more closely correspond in time to the outage.

### Claim 7 (depends on 4)

The system as defined in claim 4 wherein said Fourier series may be expressed as: T ⁡ ( t ) = A 0 ⁡ ( t ) + ∑ n = 1 N ⁢ A n ⁡ ( t ) ⁢ cos ⁢ ⁢ ω 0 ⁢ t + ∑ n = 1 N ⁢ B n ⁡ ( t ) ⁢ sin ⁢ ⁢ ω 0 ⁢ t .

### Claim 8

A method for estimating the thermal distortion of spacecraft antenna comprising:
a) generating a signal that determines an outage for the system received by the spacecraft and employing a generated time varying distortion of the system from a previous measurement history to predict the error resulting from the thermal distortion.

### Claim 9 (depends on 8)

The method as defined in claim 8 wherein said outage signal is received from a tracking receiver which measures the output of the automatic gain control loop.

### Claim 10 (depends on 8)

The method as defined in claim 8 wherein said generated time varying distortion is expressed mathematically by a Fourier series.

### Claim 11 (depends on 10)

The method of claim 10 wherein said Fourier series may be expressed mathematically as: T ⁡ ( t ) = A 0 ⁡ ( t ) + ∑ n = 1 N ⁢ A n ⁡ ( t ) ⁢ cos ⁢ ⁢ ω 0 ⁢ t + ∑ n = 1 N ⁢ B n ⁡ ( t ) ⁢ sin ⁢ ⁢ ω 0 ⁢ t .