Frequency shifting a communications signal(s) in a multi-frequency distributed antenna system (DAS) to avoid or reduce frequency interference

• US 9,184,960 B1
• Filed: 09/25/2014
• Issued: 11/10/2015
• Est. Priority Date: 09/25/2014
• Status: Active Grant

• Current Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Original Assignee: Corning Optical Communications Wireless Ltd. (Corning Incorporated)
• Inventors: Harel, Dror
• Primary Examiner(s): Tran, Khai
• Application Number:
  US14/496,349
• Time in Patent Office: 411 Days
• Field of Search: 375/334, 375/260, 375/347, 375/349, 370/254, 370/312, 370/328, 370/329, 370/344
• US Class Current: 1/1
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference
• CPC Class Codes: H04L 27/14 Demodulator circuits; Receiver circuits

Abstract

Frequency shifting a communications signal(s) in a multiple frequency (multi-frequency) distributed antenna system (DAS) to avoid or reduce frequency interference is disclosed. Related devices, methods, and DASs are disclosed. Non-limiting examples of frequency interference include frequency band interference and frequency channel interference. As a non-limiting example, frequency interference in a multi-frequency DAS may result from non-linearity of a signal processing component generating an out-of-band harmonic of a first, in-use communications signal in a first frequency band, within different frequency band(s) of other in-use communications signal(s). To avoid or reduce such interference, embodiments disclosed herein involve predicting frequency interference that may result from processing received, in-use communications signals in multiple frequency bands to be distributed in a multi-frequency DAS. Frequency shifting is performed to avoid or reduce any interfering signal products produced from the signal processing of any in-use communications signals, from interfering in the frequencies of other in-use communications signals.

Claims

1. A frequency interference prediction system in a multiple frequency (multi-frequency) distributed antenna system (DAS), comprising:

a communications signal interface, comprising;

a first communications signal interface configured to receive at least one first communications signal in at least one first frequency range; and

a second communications signal interface configured to receive at least one second communications signal in at least one second frequency range different from the at least one first frequency range;

a first communications signal path communicatively coupled to the first communications signal interface, the first communications signal path comprising;

a first frequency shifting circuit configured to frequency shift the at least one first communications signal from a first frequency in the at least one first frequency range to a shifted first communications signal at a shifted first frequency based on a first frequency control signal;

a second communications signal path communicatively coupled to the second communications signal interface and configured to provide the at least one second communications signal as an output second communications signal to a second communications signal path output;

a combiner communicatively coupled to a first communications signal path output and the second communications signal path output, the combiner configured to combine an output first communications signal and the output second communications signal into a combined multi-frequency communications signal; and

a controller configured to;

predict frequency interference in the combined multi-frequency communications signal; and

if frequency interference is predicted in the combined multi-frequency communications signal;

determine the shifted first frequency to shift the at least one first communications signal in the combined multi-frequency communications signal; and

set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency.

2. The frequency interference prediction system of claim 1, wherein:

the controller is configured to;

predict the frequency interference in the combined multi-frequency communications signal based on a first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS, interfering in the at least one second frequency range of the at least one second communications signal; and

if frequency interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, the controller is configured to determine the shifted first frequency to shift the at least one first communications signal in the combined multi-frequency communications signal so that the first interfering signal product does not interfere with the at least one second frequency range of the at least one second communications signal.

3. The frequency interference prediction system of claim 1, wherein:

the controller is configured to;

predict the frequency interference in the combined multi-frequency communications signal, based on a second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS interfering in the at least one first frequency range of the at least one first communications signal; and

if frequency interference from the second interfering signal product is predicted in the combined multi-frequency communications signal, the controller is configured to determine the shifted first frequency to shift the at least one first communications signal in the combined multi-frequency communications signal so that the second interfering signal product does not interfere with the at least one first frequency range of the at least one first communications signal.

4. The frequency interference prediction system of claim 2, wherein the second communications signal path comprises a second frequency shifting circuit configured to frequency shift the at least one second communications signal from a second frequency to a shifted second communications signal at a shifted second frequency based on a second frequency control signal.

5. The frequency interference prediction system of claim 2, further comprising a first selector circuit configured to selectively provide the at least one first communications signal or the shifted first communications signal as the output first communications signal to the first communications signal path output, in response to a first selector control signal;

the controller further configured to, if frequency interference is predicted in the combined multi-frequency communications signal, generate the first selector control signal to cause the first selector circuit to provide the shifted first communications signal as the output first communications signal to the first communications signal path output.

6. The frequency interference prediction system of claim 5, further comprising a second selector circuit configured to selectively provide the at least one second communications signal or a shifted second communications signal as the output second communications signal to the second communications signal path output, in response to a second selector control signal.

7. The frequency interference prediction system of claim 6, wherein:

if frequency interference from a first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS is predicted in the combined multi-frequency communications signal, the controller is further configured to generate the second selector control signal to cause the second selector circuit to provide the at least one second communications signal as the output second communications signal to the second communications signal path output.

8. The frequency interference prediction system of claim 4, wherein the controller is further configured to:

predict frequency interference in the combined multi-frequency communications signal based on a second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS, interfering in the at least one first frequency range of the at least one first communications signal;

if frequency interference from the second interfering signal product is predicted in the combined multi-frequency communications signal;

determine the shifted second frequency to shift the at least one second communications signal based on the predicted frequency interference in the combined multi-frequency communications signal so that the second interfering signal product does not interfere with the at least one first frequency range of the at least one first communications signal.

9. The frequency interference prediction system of claim 2, wherein:

the at least one first communications signal is in a first frequency band;

the at least one second communications signal is in a second frequency band;

the first frequency shifting circuit is configured to frequency shift the at least one first communications signal from the first frequency band to the shifted first communications signal at a shifted first frequency band based on the first frequency control signal; and

the controller is configured to;

predict frequency band interference in the combined multi-frequency communications signal, based on the first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS interfering in the second frequency band of the at least one second communications signal;

if the frequency band interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the second frequency band of the at least one second communications signal.

10. The frequency interference prediction system of claim 9, wherein the controller is configured to:

predict the frequency band interference in the combined multi-frequency communications signal by being configured to;

calculate at least one first spurious interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS; and

determine if a frequency of the at least one first spurious interfering signal product is contained in the second frequency band of the at least one second communications signal; and

if the frequency of the at least one first spurious interfering signal product is contained in the second frequency band of the at least one second communications signal, the controller is configured to set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the second frequency band of the at least one second communications signal.

11. The frequency interference prediction system of claim 3, wherein:

the at least one first communications signal is in a first frequency band;

the at least one second communications signal is in a second frequency band;

the first frequency shifting circuit is configured to frequency shift the at least one first communications signal from the first frequency band to the shifted first communications signal at a shifted first frequency band based on the first frequency control signal; and

the controller is configured to;

predict frequency band interference in the combined multi-frequency communications signal based on the second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS, interfering in the first frequency band of the at least one first communications signal;

if the frequency band interference from the second interfering signal product is predicted in the combined multi-frequency communications signal, set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of a frequency of the second interfering signal product and outside of the second frequency band of the at least one second communications signal.

12. The frequency interference prediction system of claim 11, wherein the controller is configured to:

predict the frequency band interference in the combined multi-frequency communications signal by being configured to;

calculate at least one second spurious interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS; and

determine if a frequency of the at least one second spurious interfering signal product is contained in the first frequency band of the at least one first communications signal; and

if the frequency of the at least one second spurious interfering signal product is contained in the first frequency band of the at least one first communications signal, the controller is configured to set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the frequency of the second interfering signal product and outside of the second frequency band of the at least one second communications signal.

13. The frequency interference prediction system of claim 2, wherein:

the at least one first communications signal is in at least one first frequency channel;

the at least one second communications signal is in at least one second frequency channel;

the first frequency shifting circuit is configured to frequency shift the at least one first communications signal from the at least one first frequency channel to the shifted first communications signal at a shifted first frequency channel based on the first frequency control signal; and

the controller is configured to;

predict frequency channel interference in the combined multi-frequency communications signal based on the first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS, interfering in the at least one second frequency channel of the at least one second communications signal;

if the frequency channel interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency channel outside of the at least one second frequency channel of the at least one second communications signal.

14. The frequency interference prediction system of claim 3, wherein:

the at least one first communications signal is in at least one first frequency channel;

the at least one second communications signal is in at least one second frequency channel;

the first frequency shifting circuit is configured to frequency shift the at least one first communications signal from the at least one first frequency channel to the shifted first communications signal at a shifted first frequency channel based on the first frequency control signal; and

the controller is configured to;

predict frequency channel interference in the combined multi-frequency communications signal based on the second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS, interfering in the at least one first frequency channel of the at least one first communications signal;

if the frequency channel interference from the second interfering signal product is predicted in the combined multi-frequency communications signal, set the first frequency control signal to cause the first frequency shifting circuit to frequency shift the at least one first communications signal to the shifted first communications signal at the shifted first frequency channel outside of a frequency of the second interfering signal product and outside of the at least one second frequency channel.

15. The frequency interference prediction system of claim 1, wherein the controller is further configured to provide a synchronization control signal based on the first frequency control signal in the combined multi-frequency communications signal.

16. The frequency interference prediction system of claim 1, further comprising an electrical-to-optical converter configured to convert the combined multi-frequency communications signal into an optical combined multi-frequency communications signal.

17. The frequency interference prediction system of claim 1, wherein the first frequency shifting circuit comprises:

a first synthesizer configured to receive the first frequency control signal and generate a first mixing frequency signal based on the received first frequency control signal; and

a first mixer configured to receive the first mixing frequency signal and the at least one first communications signal, and mix the first mixing frequency signal with the at least one first communications signal to generate the shifted first communications signal.

18. A method of avoiding or reducing frequency interference in a multiple frequency (multi-frequency) distributed antenna system (DAS), comprising:

receiving at least one first communications signal in at least one first frequency range in a first communications signal path comprising a first communications signal path output;

receiving at least one second communications signal in at least one second frequency range different from the at least one first frequency range in a second communications signal path comprising a second communications signal path output;

predicting frequency interference in a combined multi-frequency communications signal comprising the at least one first communications signal combined with the at least one second communications signal, as a result of an interfering signal product produced as a result of signal processing at least one of the at least one first communications signal and the at least one second communications signal;

if frequency interference is predicted in the combined multi-frequency communications signal;

determining a shifted first frequency to shift the at least one first communications signal in the combined multi-frequency communications signal;

frequency shifting the at least one first communications signal to a shifted first communications signal at the shifted first frequency; and

providing the shifted first communications signal as an output first communications signal to the first communications signal path output; and

combining the first communications signal path output and the second communications signal path output to provide the combined multi-frequency communications signal.

19. The method of claim 18, wherein:

predicting the frequency interference in the combined multi-frequency communications signal comprises predicting the frequency interference in the combined multi-frequency communications signal based on a first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS, interfering in the at least one second frequency range of the at least one second communications signal; and

if frequency interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, determining the shifted first frequency by determining the shifted first frequency to shift the at least one first communications signal in the combined multi-frequency communications signal so that the first interfering signal product does not interfere with the at least one second frequency range of the at least one second communications signal.

20. The method of claim 18, wherein:

predicting the frequency interference in the combined multi-frequency communications signal comprises predicting the frequency interference in the combined multi-frequency communications signal based on a second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS interfering in the at least one first frequency range of the at least one first communications signal; and

if frequency interference from the second interfering signal product is predicted in the combined multi-frequency communications signal, determining the shifted first frequency by determining the shifted first frequency to shift the at least one first communications signal in the combined multi-frequency communications signal so that the second interfering signal product does not interfere with the at least one first frequency range of the at least one first communications signal.

21. The method of claim 19, wherein if frequency interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, not frequency shifting the at least one second communications signal on the second communications signal path output.

22. The method of claim 20, further comprising:

predicting frequency interference in the combined multi-frequency communications signal based on the second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS, interfering in the at least one first frequency range of the at least one first communications signal;

if frequency interference from the second interfering signal product is predicted in the combined multi-frequency communications signal;

determining a shifted second frequency to shift the at least one second communications signal based on the predicted frequency interference in the combined multi-frequency communications signal so that the second interfering signal product does not interfere with the at least one second frequency range of the at least one second communications signal; and

frequency shifting the at least one second communications signal to a shifted second communications signal at the shifted second frequency.

23. The method of claim 19, wherein:

frequency shifting the at least one first communications signal comprises frequency shifting the at least one first communications signal from a first frequency band of the at least one first communications signal to the shifted first communications signal at a shifted first frequency band based on a first frequency control signal;

predicting the frequency interference comprises predicting frequency band interference in the combined multi-frequency communications signal based on the first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS interfering in a second frequency band of the at least one second communications signal; and

if the frequency band interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, frequency shifting the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the second frequency band of the at least one second communications signal.

24. The method of claim 23, wherein:

predicting the frequency band interference in the combined multi-frequency communications signal comprises;

calculating at least one first spurious interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS; and

determining if a frequency of the at least one first spurious interfering signal product is contained in the second frequency band of the at least one second communications signal; and

if the frequency of the at least one first spurious interfering signal product is contained in the second frequency band of the at least one second communications signal, frequency shifting the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the second frequency band of the at least one second communications signal.

25. The method of claim 20, wherein:

frequency shifting the at least one first communications signal comprises frequency shifting the at least one first communications signal from a first frequency band of the at least one first communications signal to the shifted first communications signal at a shifted first frequency band based on a first frequency control signal;

predicting the frequency interference comprises predicting frequency band interference in the combined multi-frequency communications signal based on the second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS, interfering in the first frequency band of the at least one first communications signal; and

if the frequency band interference from a first interfering signal product is predicted in the combined multi-frequency communications signal, frequency shifting the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of a frequency of the second interfering signal product and outside of a second frequency band of the at least one second communications signal.

26. The method of claim 25, wherein:

predicting the frequency band interference in the combined multi-frequency communications signal comprises;

calculating at least one second spurious interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS; and

determining if a frequency of the at least one second spurious interfering signal product is contained in the first frequency band of the at least one first communications signal; and

if the frequency of the at least one second spurious interfering signal product is contained in the first frequency band of the at least one first communications signal, frequency shifting the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the frequency of the second interfering signal product and outside of the second frequency band of the at least one second communications signal.

27. The method of claim 19, wherein:

frequency shifting the at least one first communications signal comprises frequency shifting the at least one first communications signal from a first frequency channel to the shifted first communications signal at a shifted first frequency channel based on a first frequency control signal;

predicting the frequency interference comprises predicting frequency channel interference in the combined multi-frequency communications signal based on the first interfering signal product generated from signal processing of the at least one first communications signal in the multi-frequency DAS, interfering in a second frequency channel of the at least one second communications signal; and

if the frequency interference from the first interfering signal product is predicted in the combined multi-frequency communications signal, frequency shifting the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of the second frequency channel of the at least one second communications signal.

28. The method of claim 20, wherein:

frequency shifting the at least one first communications signal comprises frequency shifting the at least one first communications signal from a first frequency channel to the shifted first communications signal at a shifted first frequency channel based on a first frequency control signal;

predicting the frequency interference comprises predicting frequency channel interference in the combined multi-frequency communications signal based on the second interfering signal product generated from signal processing of the at least one second communications signal in the multi-frequency DAS, interfering in the first frequency channel of the at least one first communications signal; and

if the frequency interference from the second interfering signal product is predicted in the combined multi-frequency communications signal, frequency shifting the at least one first communications signal to the shifted first communications signal at the shifted first frequency outside of a frequency of the second interfering signal product and outside of a second frequency channel.