Frequency-Dependent Filtering for Wireless Communications Transmitters

• US 20070021059A1
• Filed: 07/17/2006
• Published: 01/25/2007
• Est. Priority Date: 07/20/2005
• Status: Active Grant

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: ATC Technology Corporation (FedEx Corporation)
• Inventors: Dutta, Santanu, Karabinis, Peter
• Granted Patent: US 8,190,114 B2
• Time in Patent Office: Days
• US Class Current: 455/12.100
• CPC Class Codes: H04B 7/185 Space-based or airborne stations; Stations for satellite systemsH04B7/204 takes precedence
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00

Abstract

A method of transmitting information in a wireless communications system can be provided by selectively applying filtering to transmission of a carrier signal of a first band of frequencies of a wireless communications system based on a frequency separation distance between a frequency content of the carrier signal and a second band of frequencies allocated to a communications system other than the wireless communications system.

Claims

1. A method of transmitting information in a wireless communications system comprising:

selectively applying filtering to transmission of a carrier signal of a first band of frequencies of a wireless communications system based on a frequency separation distance between a frequency content of the carrier signal and a second band of frequencies allocated to a communications system other than the wireless communications system.

2. A method according to claim 1 wherein selectively applying filtering to transmission of a carrier signal comprises:

including the filtering in the transmission of the carrier signal when the frequency separation distance is less than a predetermined threshold; and

removing the filtering from the transmission of the carrier signal when the frequency separation distance is greater than the predetermined threshold.

3. A method according to claim 1 wherein selectively applying filtering to transmission of a carrier signal comprises:

providing the filtering when the frequency separation distance is greater than a predetermined threshold; and

changing the filtering when the frequency separation distance is less than the predetermined threshold to reduce interference in the second band from the carrier signal.

4. A method according to claim 3 wherein changing the filtering comprises changing at least one characteristic of a filter that provides the filtering.

5. A method according to claim 3 wherein changing the filtering comprises including/removing at least one component in/from the filter.

6. A method according to claim 1 wherein the carrier signal of the first band of frequencies comprises a carrier signal for a wireless communications system forward link or a wireless communications system return link and the second band of frequencies comprises a GPS frequency band or a GLONASS frequency band.

7. A method according to claim 1 wherein selectively applying filtering to transmission of a carrier signal comprises:

applying low-pass filtering to transmission of the carrier signal when the frequency content of the carrier signal is below the second band of frequencies and the frequency separation distance is less than a predetermined threshold;

applying high-pass filtering to transmission of the carrier signal when the frequency content of the carrier signal is above the second band of frequencies and the frequency separation distance is less than the predetermined threshold;

applying band-pass filtering to transmission of the carrier signal when the frequency content of the carrier signal is below a first portion of the second band of frequencies and is above a second portion of the second band of frequencies and respective frequency separation thresholds for the first and second portions are both less than the predetermined threshold; and

applying band-stop filtering to transmission of the carrier signal when a first frequency content of the carrier signal is below the second band of frequencies and a second frequency content of the carrier signal is above the second band of frequencies and respective frequency separation thresholds for the first and second frequency contents are both less than the predetermined threshold.

8. A method according to claim 1 wherein selectively applying filtering to transmission of a carrier signal comprises:

applying first filtering to transmission of the carrier signal when the frequency separation distance is less than a first predetermined threshold; and

applying second filtering to transmission of the carrier signal when the frequency separation distance is less than a less than a second predetermined threshold.

9. A method according to claim 8 where the first and second filtering differ by at least one filtering characteristic.

10. A method according to claim 9 wherein the filtering characteristic comprises a frequency response amplitude characteristic and/or a phase characteristic.

11. A method according to claim 1 wherein the second band of frequencies is specified to have a predetermined level of interference protection.

12. A method according to claim 1 wherein the first band of frequencies comprises one of a plurality of air interfaces supported by the wireless communications system.

13. A communications circuit in an Ancillary Terrestrial Component (ATC) of a wireless communications system, the circuit comprising:

a transmitter circuit configured to selectively filter transmission of a carrier signal for a first band of frequencies based on a frequency separation distance between a frequency content of the carrier signal and a second band of frequencies allocated to a communications system other than the wireless communications system.

14. A communications circuit according to claim 13 wherein the transmitter circuit comprises:

a power amplifier circuit configured to amplify radiofrequency communications signals for transmission from the transmitter circuit;

a filter circuit configured to filter the transmission of the carrier signal when coupled to the power amplifier circuit; and

a switch circuit configured to selectively couple the filter circuit to the power amplifier circuit when the frequency separation distance is less than a predetermined threshold and configured to decouple the filter circuit from the power amplifier circuit when the frequency separation distance is greater than the predetermined threshold.

15. A communications circuit according to claim 13 wherein the transmitter circuit comprises:

a power amplifier circuit configured to amplify radiofrequency communications signals for transmission from the transmitter circuit;

a filter circuit configured to filter the transmission of the carrier signal when coupled to the power amplifier circuit; and

a switch circuit configured to couple the filter circuit to the power amplifier circuit when the frequency separation distance is greater than a predetermined threshold and configured to change the filter circuit when the frequency separation distance is less than the predetermined threshold to reduce interference in the second band from the carrier signal.

16. A communications circuit according to claim 15 wherein the switch circuit is further configured to change at least one characteristic of the filter circuit or to include/remove at least one component in/from the filter circuit when the frequency separation distance is less than the predetermined threshold.

17. A communications circuit according to claim 16 wherein the at least one characteristic of the filter circuit comprises a frequency response amplitude characteristic and/or a phase characteristic.

18. A communications circuit according to claim 14 wherein the filter circuit is selectively coupled to an input of the power amplifier circuit, an output of the power amplifier circuit, and/or internal to the power amplifier circuit when the frequency separation distance is less than the predetermined threshold.

19. A communications circuit according to claim 15 wherein the filter circuit comprises a low-pass filter circuit when the frequency content of the carrier signal is below the second band of frequencies and the frequency separation distance is less than a predetermined threshold.

20. A communications circuit according to claim 15 wherein the filter circuit comprises a high-pass filter circuit when the frequency content of the carrier signal is above the second band of frequencies and the frequency separation distance is less than the predetermined threshold.

21. A communications circuit according to claim 15 wherein the filter circuit comprises a band-pass filter circuit when the frequency content of the carrier signal is below a first portion of the second band of frequencies and is above a second portion of the second band of frequencies and respective frequency separation thresholds for the first and second portions are both less than the predetermined threshold.

22. A communications circuit according to claim 15 wherein the filter circuit comprises a band-stop filter circuit when a first frequency content of the carrier signal is below the second band of frequencies and a second frequency content of the carrier signal is above the second band of frequencies and respective frequency separation thresholds for the first and second frequency contents are both less than the predetermined threshold.

23. A communications circuit according to claim 13 wherein the carrier signal comprises a carrier signal for a wireless communications system forward link or a wireless communications system return link and the second band of frequencies comprises a GPS frequency band or a GLONASS frequency band

24. A communications circuit according to claim 13 wherein the second band of frequencies is specified to have a predetermined level of interference protection.

25. A communications circuit according to claim 13 wherein the first band of frequencies comprises one of a plurality of air interfaces supported by the wireless communications system.

26. A communications circuit according to claim 25 wherein the one of a plurality of air interfaces supported by the wireless communications system comprises TDMA, CDMA, GSM, WiMAX, and/or WCDMA.

27. A communications circuit according to claim 13 wherein the transmitter circuit is included in an ATC radioterminal, a wireless communications system space based component, or a ATC base station.

28. A transmitter circuit in an Ancillary Terrestrial Component (ATC) of a wireless communications system, the circuit comprising:

a power amplifier circuit configured to amplify radiofrequency communications signals for transmission;

a filter circuit configured to filter the transmission of the carrier signal when coupled to the power amplifier circuit;

a switch circuit coupled to an input and/or output of the filter circuit;

an antenna coupled to the output of the filter circuit and/or the power amplifier circuit; and

a control circuit coupled to the switch circuit, the control circuit configured to operate the switch based on a frequency content of a carrier signal transmitted by the transmitter circuit.

29. A transmitter circuit according to claim 28 wherein the control circuit is further configured selectively couple the filter circuit to the power amplifier circuit and/or antenna to filter transmission of the carrier signal of a first band of frequencies of the wireless communications system based on a frequency separation distance between the frequency content of the carrier signal and a second band of frequencies allocated to a communications system other than the wireless communications system.

30. A transmitter circuit according to claim 29 wherein the switch circuit is coupled to the input and output of the filter circuit, wherein the control circuit is configured to couple the power amplifier circuit to the input of the filter circuit and couple the output of the filter to the antenna via the switch circuit if the frequency separation distance is less than a predetermined threshold and configured to decouple the filter circuit from the power amplifier circuit and from the antenna if the frequency separation distance is greater than the predetermined threshold.

31. A transmitter circuit according to claim 29 wherein the switch circuit is coupled to the output of the filter circuit, wherein the control circuit is configured to couple the power amplifier circuit to the antenna through the filter circuit if the frequency separation distance is less than a predetermined threshold and configured to decouple the output of the filter circuit from the antenna if the frequency separation distance is greater than the predetermined threshold.

32. A transmitter circuit according to claim 29 wherein the switch circuit is coupled to the input of the filter circuit, wherein the control circuit is configured to couple the power amplifier circuit to the antenna through the filter circuit if the frequency separation distance is less than a predetermined threshold and configured to decouple an input of the filter circuit from the power amplifier circuit if the frequency separation distance is greater than the predetermined threshold.