All-analog and hybrid radio interference cancellation using cables, attenuators and power splitters

• US 9,906,262 B2
• Filed: 06/27/2014
• Issued: 02/27/2018
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Hua, Yingbo
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US14/998,177
• Publication Number:
  US 20160285504A1
• Time in Patent Office: 1,341 Days
• Field of Search: 375254, 375346, 375284-285, 375296, 375348
• CPC Class Codes: H04B 1/1018 noise filters connected between the power supply and the receiver suppression or limitation of noise from electric apparatus H04B15/00; demodulation H03D; ripple filters H02M1/14; filters in general 95G, H03H; power supplies H04B1/1607
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/52 Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A radio interference cancellation device that cancels self-interference from a transmitter to a receiver that includes a 2N-way RF power splitter having an input and 2N outputs, a power combiner having 2N+1 inputs and an output, and 2N adaptively controllable attenuators. Each adaptively controllable attenuator is coupled by cables between a different output of the 2N-way RF power splitter and a different input of the power combiner, each cable having a total length selected to provide a delay equal to a different one of mT(m=1,N) and mT+δ(m=1,N), where T is a delay smaller than the inverse of a bandwidth of the transmitter and receiver, and δ is ¼f_c, where f_c is the carrier frequency of an RF signal transmitted by the transmitter.

Claims

1. A radio interference cancelation device that cancels self-interference from a transmitter to a receiver, the system comprising:

a 2N-way RF power splitter having an input and 2N outputs, wherein N is an integer;

a power combiner having 2N+1 inputs and an output; and

2N adaptively controllable attenuators, each adaptively controllable attenuator coupled by cables between a different output of the 2N-way RF power splitter and a different input of the power combiner, each cable having a total length selected to provide a delay equal to a different one of mT(m=1,N) and mT+δ

(m=1,N), where T is a delay smaller than the inverse of a bandwidth of the transmitter and receiver, and δ

is ¼

f_c, where f_c is the carrier frequency of an RF signal transmitted by the transmitter.

2. The device of claim 1 wherein N is chosen such that NT is larger than the delay spread of an interference channel of the transmitter and receiver.

3. The device of claim 1, wherein the adaptively controllable attenuators each have a static phase-shift.

4. The device of claim 3, where the adaptively controllable attenuators has a phase shift of one of 0°

or 180°

.

5. The device of claim 1, further comprising an additional length of cable having a relative delay equal to 2δ

=1/(2f_c) in selected cables to produce a 180-degree phase shift.

6. The device of claim 1, wherein the adaptively controllable attenuators are controlled with a tuning algorithm.

7. The device of claim 6, wherein the tuning algorithm comprises analog circuits configured to calculate y=Pa+v, where y is a vector constructed from an output waveform y(n), P is a random matrix, a is a vector of chosen parameters A_1, B_1, . . . , A_N, B_N, and v is a random vector.

8. The device of claim 7, wherein y is sampled every 10 to 100 micro-seconds.

9. The device of claim 7, where v comprises additional noise from a receiver coupled to the device and from radio frequency received from remote nodes.

10. The device of claim 1, wherein the adaptively controllable attenuators are digital step attenuators.

11. The device of claim 9, wherein digital steps of the digital step attenuators are at least 0.5 dB steps.

12. The device of claim 1, further comprising:

a radio frequency transmitter coupled to a transmit antenna through an output of an RF power amplifier,

an input attenuator having an input coupled to the output of the RF power amplifier and an output coupled to the input to the 2N-way RF power splitter; and

a receive antenna coupled to an input of the power combiner.

13. A method for canceling self-interference from a transmitter to a receiver at a radio frequency frontend, the method comprising:

splitting an output RF signal from the transmitter into 2N analog signal paths;

providing in each signal path an adaptively controllable attenuator and a delay element, each delay element providing a delay equal to a different one of mT (m=1,N) and mT+δ

(m=1,N), where T is a delay smaller than the inverse of a bandwidth of the transmitter and receiver, and δ

is ¼

f_c, where f_c is the carrier frequency of an RF signal transmitted by the transmitter, and

combining outputs of all of the adaptively controllable attenuators delay elements with an RF signal received from the transmitter on a receive antenna.

14. The method of claim 13 wherein N is chosen such that NT is larger than the delay spread of an interference channel of the transmitter and receiver.

15. The method of claim 13, wherein the adaptively controllable attenuators each have a static phase-shift.

16. The method of claim 15, where the adaptively controllable attenuators has a phase shift of one of 0°

or 180°

.

17. The method of claim 13, further comprising controlling the adaptively controllable attenuators with a tuning algorithm.

18. The method of claim 17, wherein the tuning algorithm comprises calculating y=Pa+v, where y is a vector constructed from an output waveform y(n), P is a random matrix, a is a vector of chosen parameters A_1, B_1, . . . , A_N, B_N, and v is a random vector.

19. The method of claim 13, further comprising tuning the adaptively controllable attenuators in digital steps.

20. A radio interference cancelation system that cancels self-interference from a transmitter to a receiver, the system comprising:

a radio frequency transmitter coupled to a transmit antenna through an output of an RF power amplifier,

an input attenuator coupled to the output of the RF power amplifier;

a 2N-way RF power splitter;

a receive antenna;

a power combiner having 2N+1 inputs, one input of the power combiner coupled to the receive antenna;

a low noise amplifier for a radio frequency receiver coupled to an output of the power combiner;

2N adaptively controllable attenuators, each adaptively controllable attenuator coupled by cables between a different output of the 2N-way RF power splitter and a different input of the power combiner, each cable having a total length selected to provide a delay equal to a different one of mT(m=1,N) and mT+δ

(m=1,N), where T is a delay smaller than the inverse of a bandwidth of the transmitter and receiver, and δ

is ¼

f_c, where f_c is the carrier frequency of an RF signal transmitted by the transmitter.