Method and system for equalizing cable losses in a distributed antenna system
View Patent ↗The invention is directed to a method and system for equalizing the signal losses over cable runs in a Distributed Antenna System (DAS). In a DAS, two or more antennae are connected to the system by cable runs that can vary widely in length. As a result, the signal loss over a given cable run can also vary widely which can impact the design and deployment of the DAS and reduce antenna spacing. In addition, for a broadband DAS that supports many frequency bands or ranges using a common antenna unit, the signal losses vary with respect to frequency further making it difficult to equalize the cable losses. According to one embodiment of the invention, the method and system provide for measuring and adjusting the signal losses of each cable run to be a predefined value. According to another embodiment of the invention, the DAS can include a hybrid passive-active antenna unit which includes a frequency multiplexer that separates the signal into frequency bands or ranges that are connected to an antenna element associated with a particular frequency band or range. Where a single frequency band needs to be amplified (or attenuated), a single band amplification block (SBAB) can be inserted in the connection between the frequency multiplexer and the antenna element to amplify (or attenuate) the desired frequency band. Where more than one frequency band need to be amplified (or attenuated), a multiband amplification block (MBAB) can be inserted in the connection between the frequency multiplexer and the appropriate antenna element to amplify (or attenuate) the desired frequency bands.
1. A distributed antenna system comprising:
a plurality of wireless sources coupled to at least one wiring closet unit;
a first cable run connecting a first wiring closet unit to a first antenna unit;
a second cable run connecting a second wiring closet unit to a second antenna unit;
a first signal measurement component located at a first end of the first cable run and a first equalization component coupled to the first cable run, the first signal measurement component being adapted for receiving a first received signal over the first cable run, wherein the first received signal is generated at a second opposite end of the first cable run by a first measurement signal generation component remotely positioned from the first signal measurement component, and the first signal measurement component for controlling the first equalization component to adjust an amplitude of a signal transferred over the first cable run as a function of the received signal; and
a second signal measurement component and a second equalization component coupled to the second cable run, the second signal measurement component being adapted for receiving a second received signal over the second cable run and for controlling the second equalization component to adjust an amplitude of a signal transferred over the second cable run as a function of the second received signal.
2. A distributed antenna system according to claim 1 , wherein the first equalization component adjusts the amplitude of the signal transferred over the first cable run to be substantially the same as the amplitude of the signal transferred over the second cable run as adjusted by the second equalization component.
3. A distributed antenna system according to claim 1 , wherein the first antenna unit includes the first measurement signal generation component and a first RF coupler, connecting the first measurement signal generation component to the first cable run.
4. A distributed antenna system according to claim 1 , wherein the second antenna unit includes a second measurement signal generation component and a second RF coupler, connecting the second measurement signal generation component to the second cable run.
5. A distributed antenna system according to claim 4 , wherein the first antenna unit includes a first RF coupler, connecting the first measurement signal generation component to the first cable run.
6. A distributed antenna system according to claim 1 , wherein the first signal measurement component includes
a first power detector adapted to measure a signal power level of the first signal;
a first controller adapted to receive the measure of signal power level of the first signal and for determining a signal level adjustment for the signal transferred over the first cable run.
7. A distributed antenna system according to claim 6 , wherein the first equalization component includes a first gain adjustment component for adjusting the signal level of the signal transferred over the first cable run.
8. A distributed antenna system according to claim 6 , wherein the second signal measurement component includes
a second power detector adapted to measure a signal power level of the second signal;
a second controller adapted to receive the measure of signal power level of the second signal and for determining a signal level adjustment for the signal transferred over the second cable run.
9. A distributed antenna system according to claim 8 , wherein the second equalization component includes a second gain adjustment component for adjusting the signal power level of the signal transferred over the second cable run.
10. A distributed antenna system according to claim 1 , wherein the first equalization component is part of the first wiring closet unit.
11. A distributed antenna system according to claim 1 , wherein the second equalization component is part of the second wiring closet unit.
12. A distributed antenna system according to claim 1 , wherein the first equalization component is part of the first antenna unit.
13. A distributed antenna system according to claim 1 , wherein the second equalization component is part of the second antenna unit.
14. A distributed antenna system according to claim 1 , wherein the first antenna unit includes
a first passive antenna element adapted for transferring signals corresponding to a first frequency range;
a second passive antenna element adapted for transferring signals corresponding to a second frequency range;
a frequency multiplexer connected to the first passive antenna element by a first connection and connected to the second passive antenna element by a second connection; the frequency multiplexer being adapted for receiving broadband signals and separating the broadband signals into first frequency range signals and second frequency range signals and sending the first frequency range signals over the first connection to the first passive antenna element and sending the second frequency range signals over the second connection to the second passive antenna element; and
wherein the second connection includes an amplification block adapted to amplify signals communicated between the frequency multiplexer and the second passive antenna element.
15. A method of equalizing signal losses over cable runs in a distributed antenna system, the system comprising two or more antenna units, each connected to an associated wiring closet unit by a cable run, the method comprising:
generating a measurement signal at a first end of at least one of the cable runs;
transmitting the measurement signal over at least a portion of the at least one of the cable runs;
receiving the measurement signal at a second opposite end of the at least a portion of the at least one of the cable runs;
determining a measure of signal loss over the portion of the at least one cable run; and
adjusting signal gain of a signal transferred over at least one of the cable runs as a function of the signal loss.
16. A method according to claim 15 , wherein the signal gain adjusts an amplitude of the signal transferred over at least one of the cable runs to a predefined signal amplitude at a selected location over the cable run.
17. A method according to claim 15 , wherein the signal gain adjusts an amplitude of the signal transferred over at least one of the cable runs to a predefined signal amplitude at an input to one of the antenna units.
18. A method according to claim 15 , further comprising
adjusting the signal gain over two or more cable runs to adjust a signal amplitude at two or more associated antenna units to be substantially a same predefined amplitude.
19. A method according to claim 15 , wherein the signal gain adjusts an amplitude of the signal transferred over at least one of the cable runs to a predefined signal amplitude at an input to one of the associated wiring closet units.
20. A method according to claim 15 , further comprising
adjusting the signal gain over two or more cable runs to adjust a signal amplitude at two or more associated wiring closet units to be substantially a same predefined amplitude.
21. The distributed antenna system of claim 1 , wherein the first received signal is generated by the first measurement signal generation component periodically.
22. The distributed antenna system of claim 1 , wherein the first received signal is generated by the first measurement signal generation component after power up.
23. The distributed antenna system of claim 1 , wherein the first received signal and the second received signal are in different frequency bands.