TRANSMIT LEAKAGE CANCELLATION IN A WIDE BANDWIDTH DISTRIBUTED ANTENNA SYSTEM

• US 20150303984A1
• Filed: 04/28/2015
• Published: 10/22/2015
• Est. Priority Date: 08/25/2010
• Status: Active Grant

• Current Assignee: Richard Neil Braithwaite
• Original Assignee: Richard Neil Braithwaite
• Inventors: Braithwaite, Richard Neil
• Granted Patent: US 9,698,861 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/48 in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter H04B1/46 takes precedence
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 2001/485 inhibiting unwanted transmission
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

A system and methods for cancelling transmission leakage signals in a wide bandwidth Distributed Antenna System (“DAS”) having remote units is disclosed. An internal cancellation circuit within the remote unit is employed to reduce the transmitted leakage signals by generating a cancellation signal. This cancellation signal is added to the received signal to cancel the transmission leakage signal in the receiving signal path. A pilot signal generation circuit is employed to optimize the cancellation circuit operating parameters. The frequency of the pilot signal is swept over a range to determine the pilot frequency having the highest electromagnetic coupling. The amplitude and phase of the cancellation signal is then optimized to minimize the level of transmission leakage in the receiving transmission path.

Claims

1-20. -20. (canceled)

21. A radio-frequency (RF) module for use in a wireless communication device configured for interference cancellation, the RF module comprising:

a transmit signal path to be coupled to a transmit antenna for full-duplex communications;

a receive signal path to be coupled to a receive antenna for full-duplex communications and

cancellation circuitry coupled to the receive and transmit signal paths,

wherein the cancellation circuitry is configured to generate a pilot signal for self-interference estimation, and

wherein the cancellation circuitry is configured to receive a transmuted signal and generate a cancellation signal for the receive signal path to cancel self-interference based at least on receipt of the pilot signal.

22. The RF module of claim 21 wherein the cancellation circuitry is configured to inject the pilot signal into the transmit signal path for transmission by the transmit antenna for self-interference estimation and generation of the cancellation signal.

23. The RF module of claim 22 wherein the cancellation circuitry is configured to generate an estimate of self-interference for interference between the transmit antenna and the receive antenna based on receipt of the pilot signal by the receive antenna, the estimate based on a presence of the pilot signal in the receive signal path.

24. The RF module of claim 23 wherein the RE module is configured to operate over a plurality of frequency bands, and

wherein the cancellation circuitry is configured to generate the pilot signal in each of the plurality of frequency bands and generate a corresponding cancellation signal for each of the frequency bands.

25. The RF module of claim 23 wherein the cancellation circuitry is configured to sweep the pilot signal across a plurality of frequency bands and generate a cancellation signal at a frequency having a greatest coupling between the transmit and receive signal paths.

26. The RF module of claim 23 wherein the wireless communication device is configured for operation in a full-duplex communication system,

wherein the transmit signal path comprises a transmitter including a power amplifier;

wherein the receive signal path comprises a receiver including a low-noise amplifier; and

wherein the cancellation circuitry comprises interference cancellation circuitry.

27. The RF module of claim 23 wherein the transmit signal path further comprises a variable voltage attenuator provided in the transmit signal path prior to a power amplifier;

and

wherein the receive signal path further comprises a variable voltage attenuator provided in the receive signal path after a low-noise amplifier.

28. The RF module of claim 23 wherein the cancellation circuitry comprises non-linear circuity including at least one bandpass filter operating as part of a feedback loop to provide non-linear positive feedback for generation of the cancellation signal, the at least one bandpass filter to limit a cancellation signal bandwidth.

29. The RF module of claim 28 wherein the non-linear positive feedback is used to determine a frequency within a bandwidth of the at least one bandpass filter having greater levels of coupling between the transmit and receive antennas.

30. The RF module of claim 28 wherein the cancellation circuitry comprises a vector modulator configured to generate the cancellation signal, the vector modulator configured to adjust amplitude and phase of the cancellation signal,

wherein the cancellation signal is combined with a received signal prior to the low-noise amplifier in the receive signal path.

31. The RF module of claim 21 wherein the pilot signal is configured as a self-interference signal to be received through the receive antenna from the transmit antenna, and wherein the cancellation circuitry is configured to provide the cancellation signal to the receive signal path to cancel the self-interference signal, and

wherein the cancellation circuitry is configured to output the cancellation signal comprising in-phase (I) and quadrature-phase (Q) signals to the receive signal path to cancel the self-interference signal.

32. The RF module of claim 24 wherein the transmit signal path is configured to be coupled to a plurality of transmit antennas and the receive signal path is configured to be coupled to a plurality of receive antennas,

wherein the cancellation circuitry is configured to estimate interference paths between transmit-receive antenna pairs by generation of a pilot signal for each of the interference paths, the pilot signals being injected into the transmit signal paths, and

wherein the RF module is configured for multiple-input multiple-output communication using the plurality of transmit and receive antennas.

33. The RF module of claim 24 wherein the wireless communication device is configured for frequency division duplexing (FDD) operations.

34. An apparatus for a wireless communication device, the apparatus comprising:

a transmit signal path to be coupled to a transmit antenna for full-duplex communications;

a receive signal path to be coupled to a receive antenna for ex communications; and

cancellation circuitry coupled to the receive and transmit signal paths,

wherein the cancellation circuitry is configured to generate a pilot signal for se f-interference estimation, and

wherein the cancellation circuitry is configured provide a cancellation signal to the receive signal path to cancel self-interference based on receipt of the pilot signal, the cancellation circuitry comprising non-linear circuity including at least one bandpass filter operating as part of a feedback loop to provide non-linear positive feedback for generation of the cancellation signal.

35. The apparatus of claim 34 wherein the cancellation circuitry is configured to inject the pilot signal into the transmit signal path for transmission by the transmit antenna for self-interference estimation and generation of the cancellation signal, the phase and amplitude of the pilot signal being adjusted as part of the feedback loop.

36. The apparatus of claim 35 wherein the cancellation circuitry is configured to generate an estimate of self-interference for interference between the transmit antenna and the receive antenna based on receipt of the pilot signal by the receive antenna, the estimate based on a presence of the pilot signal in the receive signal path

37. A method for interference cancellation performed by cancellation circuitry of an apparatus for a wireless communication device that includes a transmit signal path to be coupled to a transmit antenna for full-duplex communications and a receive signal path to be coupled to a receive antenna for full-duplex communications, the method comprising:

generating a pilot signal for self-interference estimation, and

providing a cancellation signal to the receive signal path to cancel self-interference based on receipt of the pilot signal, the cancellation circuitry comprising non-linear circuity including at least one bandpass filter operating as part of a feedback loop to provide non-linear positive feedback for generation of the cancellation signal.

38. The method of claim 37 further comprising:

injecting the pilot signal into the transmit signal path for transmission by the transmit antenna for self-interference estimation and generation of the cancellation signal; and

adjusting the phase and amplitude of the pilot signal as part of the feedback loop.