Method and apparatus for transmitter noise cancellation in an RF communications system
First Claim
1. A method in a RF communications system for improving a received communications signal during full duplex operation, wherein said RF communications system comprises a transmitter circuit and a receiver circuit, said method comprising:
- determining a first estimation of a signal leakage from said transmitter circuit, when said received communications signal is not being received by said receiver circuit;
when said RF communications system is in full duplex operation and said transmitter circuit is generating a transmit communication signal, determining a second estimation of said signal leakage based on said first estimation and said transmit communication signal; and
combining said second estimation with said received communications signal, such that said signal leakage is substantially cancelled in said received communications signal.
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Accused Products
Abstract
A method and apparatus is provided for reducing or eliminating the transmitter signal leakage, i.e., transmitter noise, in the receiver path of an RF communications system operating in full duplex mode. In an embodiment of the present invention, a noise cancellation loop produces an estimated transmitter signal leakage and cancels it from the receiver path to produce a received signal with little or no transmitter noise. Some of the advantages are that there is significant improvement in the isolation between the transmitter/receiver circuits, the size of the RF communications circuitry may be reduced, and the RF transmit module along with the RF receive module may be incorporated into a single RF IC chip.
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Citations
31 Claims
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1. A method in a RF communications system for improving a received communications signal during full duplex operation, wherein said RF communications system comprises a transmitter circuit and a receiver circuit, said method comprising:
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determining a first estimation of a signal leakage from said transmitter circuit, when said received communications signal is not being received by said receiver circuit;
when said RF communications system is in full duplex operation and said transmitter circuit is generating a transmit communication signal, determining a second estimation of said signal leakage based on said first estimation and said transmit communication signal; and
combining said second estimation with said received communications signal, such that said signal leakage is substantially cancelled in said received communications signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
generating a calibration signal based on a pseudo-random noise sequence;
splitting said calibration signal into a first signal and a second signal, wherein said first signal is sent to an estimation circuit and said second signal is further divided into a third signal sent to a dummy antenna load and a fourth signal sent to said estimation circuit; and
cross correlating said first signal and said fourth signal in said estimation circuit to produce said first estimation.
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7. The method of claim 6 wherein said determining said second estimation based on said first estimation comprises:
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splitting said transmit communication signal into a fifth signal and a sixth signal, wherein said fifth signal is sent to said estimation circuit and said sixth signal is sent to an antenna; and
using parameters from said first estimation, determining in said estimation circuit said second estimation from said fifth signal.
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8. A method in an RF IC communications system for substantially canceling transmitter noise during full duplex operation, wherein said RF IC communications system comprises a transmitter and a receiver, said method comprising:
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generating a predetermined calibration signal;
calibrating said RF IC communications system by sending said calibration signal to a transmit noise cancellation loop circuit;
determining loop parameters for said transmit noise cancellation loop circuit;
when in full duplex operation, estimating a transmit noise signal based on said loop parameters; and
substantially canceling said transmit noise signal from a received signal during full duplex operation. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A method in an RF IC communications system for substantially canceling transmitter noise during full duplex operation, wherein said RF IC communications system comprises a transmitter and a receiver, said method comprising:
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calibrating said RF IC communications system by disconnecting an antenna of said RF IC communications system and sending a calibration signal to a transmit noise cancellation loop circuit;
determining loop parameters for said transmit noise cancellation loop circuit;
when in full duplex operation, estimating a transmit noise signal based on said loop parameters; and
substantially canceling said transmit noise signal from a received signal during full duplex operation.
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17. A method in an RF IC communications system for substantially canceling transmitter noise during full duplex operation, wherein said RF IC communications system comprises a transmitter and a receiver, said method comprising:
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calibrating said RF IC communications system by sending a calibration signal to a transmit noise cancellation loop circuit, wherein the power of said calibration signal is increased relative to any received signal so that calibration is done without disconnecting an antenna of said RF IC communications system;
determining loop parameters for said transmit noise cancellation loop circuit;
when in full duplex operation, estimating a transmit noise signal based on said loop parameters; and
substantially canceling said transmit noise signal from a received signal during full duplex operation.
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18. A RF communications system that substantially cancels transmitter noise during full duplex operation, comprising:
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a transmit path coupled to a noise cancellation loop, and further coupled to an antenna when said RF communications system is in full duplex mode;
a received path coupled to said noise cancellation loop and further coupled to said antenna and said transmit path when said RF communications system is in full duplex mode;
said noise cancellation loop using a predetermined calibration signal to approximate a transmit noise signal from said transmit path and to cancel said transmitter noise from a received signal coupled to said received path. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A method in a RF communications system for reducing transmit noise in a received communications signal during full duplex operation, wherein said RF communications system comprises a transmitter circuit, a duplexer, and a receiver circuit, said method comprising:
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determining a first estimation of transmit noise from said transmitter circuit, when said received communications signal is not being received by said receiver circuit;
when said RF communications system is in full duplex operation and said transmitter circuit is generating a transmit communication signal, determining a second estimation of transmit noise based on said first estimation and said transmit communication signal; and
combining said second estimation with said received communications signal, such that said transmit noise is substantially cancelled in said received communications signal. - View Dependent Claims (26, 27, 28, 29)
generating a calibration signal;
splitting said calibration signal into a first signal and a second signal, wherein said first signal is sent to an estimation circuit and said second signal is further divided into a third signal sent to a dummy antenna load via said duplexer and a fourth signal sent to said estimation circuit; and
cross correlating said first signal and said fourth signal in said estimation circuit to produce said first estimation.
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27. The method of claim 25 wherein said step of determining said second estimation based on said first estimation comprises:
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splitting said transmit communication signal into a fifth signal and a sixth signal, wherein said fifth signal is sent to an estimation circuit and said sixth signal is sent to an antenna via said duplexer; and
using parameters from said first estimation, determining in said estimation circuit said second estimation from said fifth signal.
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28. The method according to claim 27 wherein said parameters include a phase and a gain.
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29. The method of claim 25 wherein said step of combining said second estimation with said received communications signal, such that said transmit noise is substantially cancelled in said received communications signal, comprises:
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obtaining a seventh signal from said duplexer comprising said received communications signal and transmit noise from said duplexer; and
combining said second estimation with said seventh signal, such that said transmit noise is substantially cancelled in said received communications signal.
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30. A RF IC chip that substantially cancels transmitter noise during full duplex communications, comprising:
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a calibration path, comprising a transmit path coupled to a noise cancellation loop and via a duplexer to an antenna dummy load, said calibration path for determining parameters associated with an estimate of a first transmitter noise signal from said duplexer, when a calibration signal is sent to said antenna dummy load; and
a full duplex operation path, comprising;
a first path comprising a transmit path coupled to said duplexer and an antenna for transmitting a first communications signal;
a second path comprising a transmit path coupled to said noise cancellation loop for determining an estimate of a second transmitter noise signal, using said parameters and a portion of said first communications signal; and
a third path coupled to said antenna and said duplexer for receiving a second communications signal; and
a fourth path coupled to said duplexer and a receive path for canceling transmitter noise added by said duplexer to said second communications signal by using said estimate of said second transmitter noise signal. - View Dependent Claims (31)
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Specification