Reduce, in a receive signal, interference caused by a simultaneous transmit signal in a same frequency band as the receive signal
In an embodiment, a remote antenna unit includes a transmitter, a receiver, an antenna array, and first and second interference circuits. The transmitter is configured to generate at least one transmit signal, and the receiver is configured to process at least one receive signal. The antenna array includes one or more antennas, each of at least one of the one or more antennas coupled to the transmitter and configured to radiate a respective downlink signal in response to a respective one of the at least one transmit signal, and each of at least one of the one or more antennas coupled to the receiver and configured to generate a respective one of the at least one receive signal in response to an uplink signal. And the first and second interference circuits are each coupled to the transmitter and to the receiver and are each configured to reduce interference in each of the at least one receive signal.
1. A remote antenna unit, comprising:
a first transmitter configured to generate at least one first transmit signal;
a first receiver configured to process at least one receive signal;
a first antenna array including one or more first antennas each coupled to at least one of the first transmitter and the first receiver,
each of at least one of the first antennas configured to radiate a respective downlink signal in response to a respective one of the at least one first transmit signal, and
each of at least one of the first antennas configured to generate a respective one of the at least one receive signal in response to an uplink signal; and
first and second interference circuits each coupled to the first transmitter and the first receiver and each configured to reduce, in each of the at least one receive signal, interference caused by one or more of the at least one first transmit signal, at least one downlink signal radiated by one of the one or more first antennas, and at least one interfering downlink signal radiated by one of one or more other antennas;
wherein at least one of the first and second interference circuits is configured to receive an analog signal from the first transmitter.
2. The remote antenna unit of claim 1 , further comprising:
a second transmitter;
a second receiver; and
wherein the first antenna array includes a multiple-input-multiple-output antenna array having at least two antennas respectively coupled to the first and second transmitters and to the first and second receivers.
3. The remote antenna unit of claim 1 , wherein the first antenna array includes a single antenna.
4. The remote antenna unit of claim 1 , wherein one of the first and second interference circuits includes an isolation circuit configured to electrically isolate the first receiver from the first transmitter.
5. The remote antenna unit of claim 1 , wherein:
one of the first and second interference circuits includes an analog interference-cancellation circuit configured to generate, for each receive signal, a corresponding correction signal; and
the first receiver is configured to generate, for each receive signal, a respective interference-cancelled receive signal in response to the receive signal and the corresponding correction signal.
6. The remote antenna unit of claim 5 , wherein the analog interference-cancellation circuit includes a finite-impulse-response filter.
7. The remote antenna unit of claim 5 , wherein the analog interference-cancellation circuit includes:
an electro-optic converter configured to generate an optical transmit signal in response to the at least one first transmit signal;
an optical filter configured to configured to generate, in response to the optical transmit signal for each receive signal, a corresponding optical correction signal; and
an opto-electric converter configured to generate each corresponding correction signal in response to a corresponding optical correction signal.
8. The remote antenna unit of claim 1 , wherein:
one of the first and second interference circuits includes an analog interference-cancellation circuit configured to generate, for each receive signal, a corresponding correction signal; and
the first receiver includes, for each receive signal, a respective signal combiner configured to generate an interference-cancelled receive signal in response to the receive signal and the corresponding correction signal.
9. The remote antenna unit of claim 1 , wherein:
one of the first and second interference circuits includes a digital interference-cancellation circuit configured to generate, for each receive signal, a corresponding correction signal;
the first receiver includes, for each receive signal, an analog-to-digital converter configured to generate a respective digital receive signal in response to the receive signal; and
the first receiver is configured, for each receive signal, to generate a respective interference-cancelled receive signal in response to the respective digital receive signal and the corresponding correction signal.
10. The remote antenna unit of claim 1 , wherein:
one of the first and second interference circuits includes a digital interference-cancellation circuit configured to generate, for each receive signal, a corresponding correction signal; and
the first receiver includes, for each receive signal,
an analog-to-digital converter configured to generate a respective digital receive signal in response to the receive signal, and
a respective signal combiner configured to generate an interference-cancelled receive signal in response to the respective digital receive signal and the corresponding correction signal.
11. The remote antenna unit of claim 1 , further comprising:
an interference receiver configured to process at least one interfering receive signal;
an interference antenna array including one or more interference antennas each coupled to the interference receiver and each configured to generate a respective one of the at least one interfering receive signal in response to one or more of the at least one interfering downlink signal; and
wherein each of at least one of the first and second interference circuits is coupled to the interference receiver and is configured to reduce, in each of the at least one receive signal, interference caused by one or more of the at least one interfering downlink signal.
12. The remote antenna unit of claim 1 , further comprising:
a second transmitter configured to generate at least one second transmit signal;
a second antenna array including one or more second antennas each coupled to the second transmitter and configured to radiate a respective second downlink signal in response to a respective one of the at one second transmit signal; and
wherein each of at least one of the first and second interference circuits is coupled to the second transmitter and is configured to reduce, in each of the at least one receive signal, interference caused by the respective second downlink signals.
13. The remote antenna unit of claim 1 , wherein the at least one transmit signal and the at least one receive signal are in a same frequency band.
14. The remote antenna unit of claim 1 , wherein the at least one transmit signal and the at least one receive signal include at least one same frequency.
15. The remote antenna unit of claim 1 , wherein each respective downlink signal and the uplink signal are in a same frequency band.
16. The remote antenna unit of claim 1 , wherein each respective downlink signal and the uplink signal include at least one same frequency.
17. The remote antenna unit of claim 1 , wherein the downlink signal radiated by one of one or more other antennas and the uplink signal are in a same frequency band.
18. A distributed antenna system, comprising:
a master unit; and
at least one remote antenna unit coupled to the master unit, each of the at least one remote antenna unit including
a respective transmitter configured to generate at least one transmit signal;
a respective receiver configured to process at least one receive signal;
a respective antenna array including one or more antennas each coupled to at least one of the transmitter and the receiver,
each of at least one of the antennas configured to radiate a respective downlink signal in response to a respective one of the at least one transmit signal, and
each of at least one of the antennas configured to generate a respective one of the at least one receive signal in response to an uplink signal; and
first and second interference circuits each coupled to the transmitter and the receiver and each configured to reduce, in each of the at least one receive signal, interference caused by one or more of the at least one transmit signal, at least one downlink signal radiated by one of the one or more antennas, and at least one interfering downlink signal radiated by one of one or more other antennas;
wherein at least one of the first and second interference circuits is configured to receive an analog signal from the transmitter.
19. The distributed antenna system of claim 18 , further comprising:
at least one base station coupled to the master unit and each configured
to generate one or more respective downlink data signals, and
to receive one or more respective uplink data signals;
wherein each transmitter is configured to generate the respective at least one transmit signal in response to a respective one of the one or more downlink data signals; and
wherein each receiver is configured to generate a respective one of the one or more uplink data signals in response to the respective at least one received signal.
20. The distributed antenna system of claim 19 , wherein at least one of the at least one base station is configured to cause each transmitter of at least one of the at least one remote antenna unit to generate a transmit signal only while the receiver of a same remote antenna unit is not processing a receive signal.
21. The distributed antenna system of claim 18 , wherein one of the at least one remote antenna unit includes:
an interference receiver configured to process at least one interfering receive signal;
an interference antenna array including one or more interference antennas each coupled to the interference receiver and each configured to generate a respective one of the at least one interfering receive signal in response to one or more of the at least one interfering downlink signal from another one of the remote antenna units; and
wherein each of at least one of the first and second interference circuits is coupled to the interference receiver and is configured to reduce, in each of the at least one receive signal, interference caused by one or more of the at least one interfering downlink signal from the other one of the remote antenna units.
22. A method, comprising:
reducing, with a first interference circuit, interference in a receive signal caused by at least one of a transmit signal generated by a remote antenna unit and a downlink signal radiated by the remote antenna unit, wherein the first interference circuit is coupled to a transmitter and configured to receive an analog signal from the transmitter; and
further reducing, with a second interference circuit, interference in the receive signal caused by at least one of the transmit signal and the downlink signal, wherein the second interference circuit is coupled to the transmitter.
23. The method of claim 22 , further comprising:
generating the receive signal with an antenna in response to an uplink signal; and
coupling the transmit signal to the antenna while generating the receive signal with the antenna.
24. The method of claim 22 , further comprising:
generating the receive signal with an antenna; and
radiating the downlink signal with another antenna while generating the receive signal with the antenna.
25. The method of claim 22 , wherein reducing, with the first interference circuit, interference in the receive signal includes electrically isolating the receive signal from the transmit signal with the first interference circuit.
26. The method of claim 22 , further comprising:
generating the downlink signal in response to a different transmit signal; and
wherein reducing, with the first interference circuit, interference in the receive signal includes
generating a cancelling signal in response to the different transmit signal, and
generating a corrected receive signal in response to the receive signal and the cancelling signal.
27. The method of claim 22 , wherein reducing, with the first interference circuit, interference in the receive signal includes:
generating a cancelling signal in response to the downlink signal, and
generating a corrected receive signal in response to the receive signal and the cancelling signal.
28. The method of claim 22 , further comprising:
generating the downlink signal in response to a different transmit signal; and
wherein further reducing, with the second interference circuit, interference in the receive signal includes
generating a cancelling signal in response to the different transmit signal, and
generating a corrected receive signal in response to the receive signal and the cancelling signal.
29. The method of claim 22 , wherein further reducing, with the second interference circuit, interference in the receive signal includes:
generating a cancelling signal in response to the downlink signal, and
generating a corrected receive signal in response to the receive signal and the cancelling signal.