Self-interference cancellation antenna systems and methods

• US 9,660,674 B2
• Filed: 12/29/2015
• Issued: 05/23/2017
• Est. Priority Date: 07/16/2015
• Status: Active Grant

• Current Assignee: LGS Innovations LLC (CACI International Incorporated)
• Original Assignee: LGS Innovations LLC (CACI International Incorporated)
• Inventors: Baker, Benjamin Joseph, Brannon, Alan Scott, Pack, Riley Nelson
• Primary Examiner(s): GONZALES, APRIL GUZMAN
• Application Number:
  US14/982,423
• Publication Number:
  US 20170019132A1
• Time in Patent Office: 511 Days
• Field of Search: 455 78
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/0042 Digital filtering H04B1/0035 takes precedence; digital filters per se H03H17/00
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/401 for selecting or indicating operating mode
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04B 1/715 Interference-related aspects
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 15/02 Reducing interference from electric apparatus by means located at or near the interfering apparatus
• CPC Class Codes: H04B 2001/0408 with power amplifiers
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/025 using least-mean-square [LMS] method
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/1461 Suppression of signals in the return path, i.e. bidirectional control circuits

Abstract

The present application describes systems and methods of performing self-interference cancellation. Such systems may include generating a transmit signal along a transmit path of a transceiver, where the transmit signal can be sent through a circulator to isolate the transmit signal from a receiver. The transmit signal may be transmitted from an antenna, and a signal may be reflected from the antenna, where the reflected signal may be at less power than an incident power to the antenna, and where the reflected signal may include a transmitter carrier signal and a transmitter noise. A received signal may be routed from the antenna to the receiver, the reflected signal may be routed through a filter and a phase shifter, and the signal may be combined with the received signal in the receive path to cancel the portion of the transmit signal that entered the receive path towards the receiver from the circulator.

Claims

1. A self-interference cancellation system, comprising:

a transmitter power amplifier configured to amplify a transmit signal;

a first circulator coupled to the transmitter power amplifier, the first circulator being coupled to a transmission-reception path of the self-interference cancellation system;

a second circulator coupled to the first circulator;

an antenna at an end of the transmission-reception path, the antenna being configured to transmit the transmit signal and receive a receive signal;

a receiver amplifier coupled to a reception path of the self-interference cancellation system;

a phase shifter coupled to the reception path and the second circulator; and

a filter coupled to the phase shifter, the filter being located between the phase shifter and an electrical load.

2. The system of claim 1, wherein the phase shifter is located between the antenna and the first circulator along the transmission-reception path.

3. The system of claim 1, wherein the second circulator is located between the antenna and the first circulator along the transmission-reception path.

4. The system of claim 1, wherein the second circulator is located between the first circulator and the receiver amplifier along the reception path.

5. The system of claim 1, further comprising:

an electrical ground, wherein the electrical load is located between the filter and the electrical ground.

6. The system of claim 1, further comprising:

an attenuator coupled to the phase shifter.

7. The system of claim 1, wherein the filter is a transmitter bandpass filter or a receiver notch filter.

8. The system of claim 1, wherein the electrical load includes a resistor.

9. The system of claim 1, wherein the system is a wireless communication base station or a mobile wireless device.

10. A method of performing self-interference cancellation comprising the steps of:

generating a transmit signal along a transmit path of a transceiver;

sending the transmit signal through a circulator to substantially isolate the transmit signal from a receiver, wherein at least a portion of the transmit signal enters a receive path towards the receiver;

generating a reflected signal from the antenna, wherein the reflected signal from the antenna is at substantially less power than an incident power to the antenna, wherein the reflected signal includes a transmitter carrier signal and a transmitter noise;

routing a received signal from the antenna to the receiver;

routing the reflected signal through a phase shifter in the receive path; and

combining the reflected and phase shifted transmitter noise with the received signal in the receive path to cancel the portion of the transmit signal that entered the receive path towards the receiver from the circulator.

11. The method of claim 10, further comprising:

routing the reflected signal through a transmitter bandpass filter to remove the transmitter carrier signal in the receive path.

12. The method of claim 10, further comprising:

routing the reflected signal through a receiver notch filter to reflect the received signal in the receive path.

13. The method of claim 10, wherein the phase shifter is coupled to a variable attenuator, where the variable attenuator adjusts an amplitude of the reflected signal.

14. The method of claim 10, further comprising a second circulator coupled to the circulator, wherein the circulator is a first circulator.

15. The method of claim 14, wherein the second circulator is located between the antenna and the first circulator along a transmission-reception path.

16. The method of claim 14, wherein the second circulator is located between the first circulator and a receiver amplifier along a reception path.

17. The method of claim 14, wherein the phase shifter shifts the phase of the reflected signal from the antenna a number of degrees to cancel the portion of the transmit signal that entered the receive path towards the receiver from the circulator.