Calibration apparatus and method

• US 20100164782A1
• Filed: 03/24/2009
• Published: 07/01/2010
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Astrium Limited (Airbus SE)
• Original Assignee: Astrium Limited (Airbus SE)
• Inventors: Chana, Satwinder Singh, Bishop, Andrew Mark, Saha, Mrinal Kanti, Ruiz Jerez, Ana Belen
• Granted Patent: US 8,604,975 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04B 7/18519 Operations control, administration or maintenance
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

Abstract

There is provided an apparatus for calibrating a multi-beam satellite system comprising a beam forming network providing a plurality of signal paths, the apparatus comprising a calibration processor for determining the phase and amplitude shift of a test path of the plurality of signal paths by correlating a calibration tone extracted from the test path with a reference calibration signal, the calibration processor being configured to determine the phase and amplitude shifts of the test path for at least two calibration tones of at least two different frequencies. The apparatus also comprises means for applying a correction based on the determined phase and amplitude shift to the test path in the beam forming network. The two calibration tones of at least two different frequencies may be calibration tones injected at two different frequencies but also calibration tones translated into two different frequencies by the beam forming network. The invention allows a phase and amplitude shift for any path through the beam forming network to be calculated for any frequency in an operational frequency range of the multi-beam satellite system and corrections to be applied to form or interpret the required downlink or uplink beams of the multi-beam satellite system.

Claims

1. Apparatus for calibrating a multi-beam satellite system comprising a beam forming network providing a plurality of signal paths, the apparatus comprising

a calibration processor for determining the phase and amplitude shift of a test path of the plurality of signal paths by correlating a calibration tone extracted from the test path with a reference calibration signal,

the calibration processor being configured to determine the phase and amplitude shift of the test path for at least two calibration tones of at least two different frequencies to allow a phase and amplitude offset of the test path for a signal of any frequency within an operational frequency range of the multi-beam satellite system to be calculated.

2. Apparatus according to claim 1, wherein the apparatus further comprises a coupler for injecting a calibration tone into the test path and the at least two calibration tones comprise two calibration tones of different frequencies at the times of injection.

3. Apparatus according to claim 2, further comprising a digital signal processor for translating the frequency of a calibration tone in the test path and wherein the at least two calibration tones comprise at least two calibration tones translated into two different frequencies.

4. Apparatus according to claim 3, wherein the calibration processor is further configured to, for a calibration tone of a specific injection frequency and frequency translation, sequentially select each of the paths from a group of paths of the plurality of paths as the test path to allow the phase and amplitude offset of each path from the group of paths to be determined.

5. Apparatus according to claim 4, wherein the apparatus comprises a beam forming network having a plurality of inputs and a plurality of outputs and the group of paths is selected from all paths through a specific input or all paths through a specific output.

6. Apparatus according to claim 1, wherein the beam forming network is configured to apply corrections to said test path based on the determined phase and amplitude shifts of the test path for the at least two calibration tones of the at least two different frequencies

7. Apparatus according to claim 1, wherein the reference calibration signal comprises a calibration tone extracted from a reference path of said plurality of paths.

8. Apparatus according to claim 1 wherein the reference calibration signal comprises a pure calibration tone at a frequency of a calibration tone extracted from the test path.

9. Apparatus according to claim 1 further comprising a transmitter for transmitting the determined phase and amplitude shifts to a ground station and a receiver for receiving corrections to be applied to the beam forming network from the ground station based on the determined phase and amplitude shifts.

10. Apparatus according to claim 1, further comprising

a beam splitter for forwarding a signal to a beam forming network;

an amplifier for amplifying signals from the beam forming network, the test path comprising a path from the beam splitter to the amplifier;

a coupler for injecting a calibration tone into the beam splitter; and

a switch unit for forwarding said signal from said test path from the amplifier to the calibration processor.

11. Apparatus according to claim 1, further comprising

an amplifier for amplifying a signal for a beam forming network;

a signal combiner for combining a signal received from the beam forming network, said test path comprising a path from the amplifier to the combiner;

a switch unit for injecting a calibration tone into the test path in the amplifier; and

a coupler for forwarding said signal from said test path from said signal combiner to the calibration processor.

12. A multi-beam satellite system comprising the apparatus of claim 1.

13. A system comprising the multi-beam satellite system of claim 12 and a ground station configured to receive phase and amplitude shift measurements from the multi-beam satellite system, calculate corrections for a path of the plurality of signal paths and transmit the corrections to the multi-beam satellite system.

14. A system according to claim 13, further comprising a processor for adjusting the determined phase and amplitude shifts and corrections based on the determined phase and amplitude shifts for phase and amplitude shifts introduced by equipment having non-linear phase and amplitude characteristics in the plurality of paths.

15. A method of calibrating a multi-beam satellite system having a beam forming network providing a plurality of signal paths, the method comprising

extracting calibration tones from a test path of the plurality of paths;

and

determining the phase and amplitude shifts of the test path for the calibration tones by correlating the extracted calibration tones with reference calibration signals, wherein the calibration tones comprise at least two calibration tones of different frequencies to allow a phase and amplitude offset of the test path for a signal of any frequency within an operational frequency range of the multi-beam satellite system to be calculated from the determined phase and amplitude shifts.

16. A method according to claim 15, wherein extracting calibration tones comprises extracting a first calibration tone of the at least two calibration tones of different frequencies and subsequently extracting a second calibration tone of the at least two calibration tones of different frequencies.

17. A method according to claim 16, further comprising injecting calibration tones into the test path and wherein the at least two calibration tones of different frequencies comprise two calibration tones of different frequencies at the times of injection.

18. A method according to claim 17, further comprising translating the frequency of the calibration tone in the test path and wherein the at least two calibration tones of different frequencies comprise two calibration tones translated into different frequencies.

19. A method according to claim 18, further comprising, for a calibration tone of a specific injection frequency and frequency translation, sequentially selecting each of the paths from a group of paths of the plurality of paths as the test path to allow the phase and amplitude of each path from the group of paths to be determined.

20. A method according to claim 19, wherein the group of paths is selected from all paths through a specific input to a beam forming network or all paths through a specific output from a beam forming network.

21. A method according to claim 15 further comprising extracting a calibration tone from a reference path of the plurality of paths and providing the extracted calibration tone as one of said reference calibration signals for said extracted calibration tones from the test path.

22. A method according to claim 15 wherein the calibration reference signals comprise a pure calibration tone at the frequency of one of the calibration tones extracted from the test path.

23. A method according to claim 15 further comprising applying a correction to the beam forming network based on the determined phase and amplitude shifts for the at least two calibration tones of different frequencies.

24. A method according to claim 23, further comprising

transmitting the determined phase and amplitude shifts to a ground station and receiving said correction from the ground station.

25. A method according to claim 24, further comprising adjusting the determined phase and amplitude shifts and corrections determined based on the determined phase and amplitude shifts for amplitude and phase shifts introduced by non-linear equipment in the plurality of paths.

26. A computer program for calibrating a multi-beam satellite system having a beam forming network providing a plurality of signal paths, the computer program comprising instructions that when executed by a processor cause the processor to

extract calibration tones from a test path of the plurality of paths;

and

determine the phase and amplitude shifts of the test path for the calibration tones by correlating the extracted calibration tones with reference calibration signals, wherein the calibration tones comprise at least two calibration tones of different frequencies to allow a phase and amplitude offset of the test path for a signal of any frequency within an operational frequency range of the multi-beam satellite system to be calculated from the determined phase and amplitude shifts.

27. Apparatus for calibrating a multi-beam satellite system comprising a beam forming network providing a plurality of signal paths, the apparatus comprising

a digital signal processor for translating a signal in a test path of said plurality of paths from a first frequency to a second frequency, the signal comprising a calibration tone;

a calibration processor for determining the phase and amplitude shift of the test path by correlating a calibration tone extracted from the test path with a reference calibration signal, the calibration processor being configured to determine the phase and amplitude shift of the test path for at least two calibration tones of different frequencies and the digitals signal processor being configured to apply a correction, based on the determined phase and amplitude shifts for the at least two calibration tones, to the test path.