Techniques to simultaneously transmit and receive over the same radiofrequency carrier

• US 9,537,543 B2
• Filed: 12/20/2011
• Issued: 01/03/2017
• Est. Priority Date: 12/20/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Choi, Yang-Seok
• Primary Examiner(s): Phung, Luat
• Assistant Examiner(s): Waqas, Saad A
• Application Number:
  US13/976,423
• Publication Number:
  US 20140376416A1
• Time in Patent Office: 1,841 Days
• Field of Search: 370/277
• US Class Current: 1/1
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04B 7/015 Reducing echo effects
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex

Abstract

An apparatus may include an antenna and a transceiver coupled to the antenna, the transceiver including a receiver operative to receive a radio-frequency (RF) signal and a transmitter operative to transmit a RF signal. The apparatus may also include an RF echo cancellation module coupled to the receiver and the transmitter, the RF echo cancellation module operative to generate an analog echo cancellation signal for the received RF signal based on a delayed version of the transmit RF signal. Other embodiments are disclosed and claimed.

Claims

1. An apparatus, comprising:

an antenna;

a transceiver coupled to the antenna, the transceiver comprising;

a receiver operative to receive a radio-frequency (RF) signal via an RF carrier over a time interval; and

a transmitter operative to transmit an upconverted signal x(t) over the RF carrier during the time interval;

a two-tap filter having first and second respective delays τ

₁ and τ

₂, the two-tap filter being arranged to receive the upconverted signal x(t) and generate first and second delayed upconverted signals x(t−

τ

₁) and x(t−

τ

₂), the unconverted signal x(t) to comprise a bandwidth BW, a product of the bandwidth and an absolute value of a difference of the first and second delays BW|(τ

₁−

τ

₂)| being less than 0.2; and

an RF echo cancellation module coupled to the receiver and the transmitter, the RF echo cancellation module operative to generate an analog echo cancellation signal for the received RF signal based on the first and second delayed unconverted signals x(t−

τ

₁) and x(t−

τ

₂).

2. The apparatus of claim 1, the receiver comprising a multiplier operative to receive as input the received RF signal and the analog echo cancellation signal, multiply the received RF signal and the analog echo cancellation signal, and output an echo cancelled RF signal.

3. The apparatus of claim 2, the receiver comprising a low noise amplifier coupled to the multiplier, the low noise amplifier operative to receive the echo cancelled RF signal and amplify the echo cancelled RF signal.

4. The apparatus of claim 1, the RF echo cancellation module comprising a vector modulator to:

receive a filtered component signal x(t−

τ

) of the upconverted signal to be transmitted; and

output an echo cancellation signal based on a transform of the filtered component signal.

5. The apparatus of claim 1, the RF echo cancellation module comprising a weight calculator to:

receive in phase and quadrature echo cancelled received signal components z_i(t) and z_q(t);

receive in phase and quadrature downconverted transmit signals {tilde over (x)}_1,i(t) and {tilde over (x)}_1,q(t), respectively;

add products {tilde over (x)}_1,i(t) z_i(t) and {tilde over (x)}_1,q(t) z_q(t) to form an in phase weight vector w_1,i; and

add products {tilde over (x)}_1,i(t) z_q(t) and {tilde over (x)}_1,q(t) z_i(t) to form the quadrature weight vector w_1,q.

6. The apparatus of claim 5, the vector modulator comprising:

a delay module to apply a delay to a first portion of the filtered component signal;

a Hilbert transform module to output a Hilbert transform of a second portion of the filtered component signal {circumflex over (x)}(t−

τ

₁);

a first multiplier to output a product of the delayed filtered component multiplied by the in-phase weight vector for estimating echo w_1,ix(t−

τ

₁); and

a second multiplier to output a product of the delayed filtered component multiplied by the quadrature weight vector for estimating echo w_1,qx(t−

τ

₁).

7. The apparatus of claim 1, comprising a baseband echo cancellation module arranged to:

determine a weight vector W for a two-tap Wiener filter to minimize power of a baseband echo cancelled signal Z(t) from a received signal Y(t), where Z(t)=Y(t)−

W₁X(t−

τ

₁)e<sup>jω

τ

1</sup>−

W₂X(t−

τ

₂)e<sup>jω

τ

2</sup>=Y(t)X(t), where W_k=W_k,i+jw_k,q and W=[W₁ W₂]^T and where τ

₁ and τ

₂ are delays of the two-tap Wiener filter.

8. The apparatus of claim 7, the baseband echo cancellation module arranged to update W according to W=W+μ

X*(t)Z(t), where μ

equals step size.

9. The apparatus of claim 1, comprising a digital display to present information received in a received echo-cancelled signal derived from the analog echo cancellation signal.

10. A method, comprising:

receiving a radio-frequency (RF) signal Y(t) via an RF carrier over a time interval; and

generating a first echo cancellation signal to provide echo cancellation after the received RF signal Y(t) is downconverted to a baseband signal Z(t) in a baseband frequency range;

generating an upconverted signal x(t) to be transmitted over the RF carrier during the time interval;

filtering the upconverted signal x(t) using a two-tap filter comprising a first delay τ

₁ and second delay τ

₂ to generate first and second delayed upconverted signals x(t−

τ

₁) and x(t−

τ

₂), where a product BW|(τ

₁−

τ

₂)| is set to equal less than 0.2, where BW represents a bandwidth of the upconverted signal x(t) and |(τ

₁−

τ

₂)| represents an absolute value of a difference between the first and second delays τ

₁ and τ

₂; and

generating a second analog echo cancellation signal based on the first and second delayed upconverted signals x(t−

τ

₁) and x(t−

τ

₂), the second echo cancellation signal to provide echo cancellation between the upconverted signal x(t) and the received RF signal Y(t).

11. The method of claim 10, comprising:

applying a delay to a first portion of a filtered component signal;

performing a Hilbert transform on a second portion of the filtered component signal;

outputting a product of the delayed filtered component signal multiplied by an in-phase weight vector for estimating echo;

and outputting a product of the delayed filtered component signal multiplied by a quadrature weight vector for estimating echo.

12. The method of claim 10, comprising:

generating in phase and quadrature echo cancelled received baseband signal components z_i(t) and z_q(t), respectively;

generating in phase and quadrature downconverted transmit signals {tilde over (x)}_1,i(t) and {tilde over (x)}_1,q(t), respectively;

adding products {tilde over (x)}_1,i(t) z_i(t) and {tilde over (x)}_1,q(t) z_q(t) to form an in phase weight vector w_1,i; and

adding products {tilde over (x)}_1,i(t) z_q(t) and {tilde over (x)}_1,q(t) z_i(t) to form a quadrature weight vector w_1,q; and

applying w_1,i and w_1,q to the upconverted signal x(t).

13. At least one non-transitory computer-readable storage medium comprising a plurality of instructions that, when executed, cause a system to:

generate a transmit radio-frequency (RF) signal for transmission over an RF carrier, the transmit RF signal to be transmitted over the RF carrier during a time interval, the transmit RF signal to comprise an unconverted signal x(t);

filter the upconverted signal x(t) using a two-tap filter comprising a first delay τ

₁ and second delay τ

₂ to generate first and second delayed upconverted signals x(t−

τ

₁) and x(t−

τ

₂), where a product BW|(τ

₁−

τ

₂)| is set to equal less than 0.2, where BW represents a bandwidth of the upconverted signal x(t) and |(τ

₁−

τ

₂)| represents an absolute value of a difference between the first and second delays τ

₁ and τ

₂; and

generate an analog echo cancellation signal for a received radio-frequency (RF) signal based on the first and second delayed upconverted signals x(t−

τ

₁) and x(t−

τ

₂), the received RF signal to be received via the RF carrier over the time interval.

14. The at least one computer-readable storage medium of claim 13 comprising instructions that, when executed, cause a system to:

receive a filtered component signal of the upconverted signal to be transmitted; and

output an echo cancellation signal based on a transform of the filtered component signal.

15. The at least one computer-readable storage medium of claim 13 comprising instructions that, when executed, cause a system to:

receive in phase and quadrature echo cancelled received signal components z_i(t) and z_q(t);

receive in phase and quadrature downconverted transmit signals {tilde over (x)}_1,i(t) and {tilde over (x)}_1,q(t), respectively;

add products {tilde over (x)}_1,i(t) z_i(t) and {tilde over (x)}_1,q(t) z_q(t) to form an in phase weight vector w_1,i; and

add products {tilde over (x)}_1,i(t) z_q(t) and {tilde over (x)}_1,q(t) z_q(t) to form the quadrature weight vector w_1,q.

16. The at least one computer-readable storage medium of claim 14 comprising instructions that, when executed, cause a system to:

apply a delay to a first portion of the filtered component signal;

output a Hilbert transform of a second portion of the filtered component signal;

output a product of the delayed filtered component signal multiplied by an in-phase weight vector for estimating echo;

and output a product of the delayed filtered component signal multiplied by a quadrature weight vector for estimating echo.