Apparatus and method for cancellation of partially overlapped crosstalk signals

• US 7,640,000 B2
• Filed: 11/28/2006
• Issued: 12/29/2009
• Est. Priority Date: 12/10/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Lee, Yong-Hwan, Park, Hyeong-Jun, Cheong, Min-Ho
• Primary Examiner(s): Le; Lana N
• Application Number:
  US11/604,898
• Publication Number:
  US 20070133815A1
• Time in Patent Office: 1,127 Days
• Field of Search: 455295-296, 4552261-2264, 455 6711- 6714, 455/307, 375/324, 375/326, 375/346, 375/349, 381/71.1, 381/17
• US Class Current: 455/295
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence

Abstract

The present invention is related to a partially overlapped single-carrier crosstalk signal cancellation method and an apparatus using the same. For this purpose, the present invention provides a crosstalk canceller including a pre-processor for frequency down-shifting an input signal, a crosstalk signal cancellation module for canceling the crosstalk signal by dividing the input signal by an interpolation ratio, a post-processor for converting an output of the crosstalk signal cancellation modulation into a passband signal, and an error feedback processor for performing a decimation operation on a residual crosstalk signal and feeding backing the decimated residual crosstalk signal to the crosstalk signal cancellation module. In addition, the present invention provides a crosstalk signal cancellation method for performing interpolation and filtering operations by frequency down-shifting an input signal including a crosstalk signal to a baseband and decimating a residual crosstalk signal by frequency-shifting to an original signal frequency.

Claims

1. An apparatus for canceling a crosstalk signal that is generated due to overlapping of a transmit frequency and a receive frequency in a mobile communication system, the apparatus comprising:

a pre-processor for frequency down-shifting an input signal having the crosstalk signal to a baseband;

a crosstalk signal cancellation module for canceling the crosstalk signal from the input signal by dividing the frequency down-shifted input signal by an interpolation ratio;

a post-processor for converting an output of the crosstalk signal cancellation module into a passband signal; and

an error feedback processor for receiving a residual crosstalk signal generated during a crosstalk signal cancellation process of the crosstalk signal cancellation module from the post-processor, performing a decimation operation, and feeding a result of the decimation operation back to the crosstalk signal cancellation module.

2. The apparatus of claim 1, wherein the post-processor comprises:

an interpolation module for receiving an output of the crosstalk signal cancellation module and performing an interpolation operation on the output;

an interpolation filter for filtering the interpolated signal; and

a multiplier for converting the filtered intermediate signal into the passband signal.

3. The apparatus of claim 2, wherein the interpolation module uses a value R as a factor for the interpolation operation, the value R being obtained by dividing a polyphase interpolation ratio L by an interpolation ratio K that is used for crosstalk signal cancellation.

4. The apparatus of claim 1, wherein the error feedback processor comprises:

a multiplier for frequency-shifting the residual crosstalk signal to a baseband equivalent band;

a decimation filter for performing a filtering operation to decimate the frequency-shifted residual crosstalk signal received from the multiplier; and

a decimation module for decimating the residual crosstalk signal filtered by the decimation filter and transmitting a decimation result to the crosstalk signal cancellation module.

5. The apparatus of claim 1, wherein the apparatus uses a filtered-X algorithm comprising:

a first auxiliary filter for filtering a signal interpolated by the post-processor and filtering a signal decimated by the error feedback processor;

a baseband crosstalk signal processor for processing a baseband-equivalent crosstalk signal; and

a second auxiliary filter for filtering the crosstalk signal processed by the baseband crosstalk signal processor.

6. The apparatus of claim 5, wherein the second auxiliary filter has an inverse relationship with the first auxiliary filter.

7. A method for canceling a crosstalk signal that is generated due to overlapping of a transmit frequency and a receive frequency in a mobile communication system, the method comprising:

(a) frequency down-shifting an input signal having a crosstalk signal to a baseband;

(b) converting the frequency down-shifted input signal into a passband signal by performing an interpolation operation;

(c) filtering the interpolated signal and frequency-shifting to an original signal frequency; and

(d) decimating a residual crosstalk signal generated during the interpolation and filtering processes, and repeating from step (b).

8. The method of claim 7, wherein (d) comprises:

(d1) frequency down-shifting the residual crosstalk signal to a baseband;

(d2) filtering the frequency-shifted residual crosstalk signal by using a decimation filter;

(d3) decimating the filtered residual crosstalk signal; and

(d4) repeating from step (b).

9. The method of claim 8, wherein, in (d1), the residual crosstalk signal is frequency down-shifted by an amount of f₀ by multiplying the residual crosstalk signal by

$e^{}$

- j2π

⁡

( f C L - f o ) ⁢

π

⁢

⁢

T L .

10. The method of claim 8, wherein, in (d3), the decimation operation is performed by using a value (R) as a factor, the value (R) being obtained by dividing an interpolation ratio (L) of a polyphase structure by an interpolation ratio (K) that is used for crosstalk signal cancellation.

11. The method of claim 7, wherein, in (a), the input signal is frequency down-shifted by an amount of f_o by multiplying the input signal by

$e^{}$

- j2π

⁡

( f C L - f o ) ⁢

π

⁢

⁢

T L ,

where

$f_o=\{\begin{array}{cc}{f}_{C_L}-f_e;<br><br>& \mathrm{in}<br><br><br><br>\mathrm{the}<br><br><br><br>\mathrm{premises}\\ f_{C_H}-f_e;<br><br>& \mathrm{in}<br><br><br><br>\mathrm{the}<br><br><br><br>\mathrm{central}<br><br><br><br>\mathrm{office}.\end{array},\mathrm{and}<br><br><br><br>\mathrm{herein}$

f_CL denotes a carrier frequency of a low-band signal, and f_CH denote a carrier frequency of a high-band signal.

12. The method of claim 7, wherein, in (c), the filtered interpolation signal is multiplied by

$e^{}$

j2π

⁡

( f C L - f o ) ⁢

π

⁢

⁢

T L

so as to frequency-shift to an original signal frequency.

13. The method of claim 7, wherein, in (b), the interpolation operation is performed by using a value (R) as a factor, the value (R) being obtained by dividing an interpolation ratio (L) of a polyphase structure by an interpolation ratio (K) that is used for crosstalk signal cancellation.

14. The method of claim 7, wherein the method comprises:

filtering the interpolated signal and the decimated signal by using a filtered-X algorithm including a pre-processing filter and a post-processing filter; and

filtering the crosstalk signal by using the filtered-X algorithm.