Apparatus and methods for compensating for signal imbalance in a receiver

• US 8,537,925 B2
• Filed: 10/04/2011
• Issued: 09/17/2013
• Est. Priority Date: 11/20/2006
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Levi, Zak, Shusterman, Eliyahu
• Primary Examiner(s): NGUYEN, LEON VIET Q
• Application Number:
  US13/252,385
• Publication Number:
  US 20120093244A1
• Time in Patent Office: 714 Days
• Field of Search: 370/208, 375/147, 375/267, 375/316, 375/344, 375/350, 375/355, 455/517, 455/522
• US Class Current: 375/267
• CPC Class Codes: H03D 3/009 Compensating quadrature phase or amplitude imbalances
• CPC Class Codes: H04L 27/2649 Demodulators
• CPC Class Codes: H04L 27/266 Fine or fractional frequency offset determination and synchronisation
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal

Abstract

Apparatus, methods and systems for compensating for an I/Q imbalance may include compensating for an imbalance between a first component of a data signal and a second component of the data signal. The data signal may be modulated by a carrier signal having a frequency error. The first component may be characterized by at least one parameter. The method may include receiving the data and carrier signals; selecting a value for the parameter such that the frequency domain energy at negative frequencies is reduced; and modifying at least one of the components based on the value.

Claims

1. A method for compensating for an imbalance between a first component of a data signal and a second component of the data signal, the data signal having a positive-valued frequency and being modulated by a carrier signal having a frequency error, the method comprising:

receiving the data and carrier signals;

selecting a value for a time domain parameter such that a frequency domain energy corresponding to a negative-valued frequency is minimized;

modifying in the time domain at least one of the components based on the value,

estimating a carrier signal frequency corresponding to the carrier signal;

estimating a residual carrier frequency error; and

modifying an estimate of the carrier frequency based on the residual carrier frequency error;

wherein the modifying in the time domain comprises;

identifying a first value corresponding to a signal amplitude multiplier for the component; and

identifying a second value corresponding to a phase shift for the component.

2. The method of claim 1 wherein the selecting includes recording a first frequency domain parameter and a second frequency domain parameter for each of a first tone, a second tone and the carrier signal.

3. The method of claim 2 wherein:

for at least one of the first tone, the second tone and the carrier signal, the first and second frequency domain parameters correspond, respectively to first and second bins in a discrete-valued frequency spectrum; and

the first bin is sequentially adjacent the second bin.

4. The method of claim 2 further comprising transmitting an output signal that depends on the first and second frequency domain parameters.

5. The method of claim 2 wherein:

the receiving comprises receiving an orthogonal frequency division multiplexing (OFDM) symbol; and

in the selecting the value corresponds to the OFDM symbol; and

the modifying is performed with respect to the OFDM symbol.

6. The method of claim 2 wherein:

the receiving comprises receiving a plurality of orthogonal frequency division multiplexing (OFDM) symbols;

the selecting is performed for each of the OFDM symbols; and

the modifying is performed for each of the OFDM symbols.

7. The method of claim 2 wherein:

one of the first and second components is an in-phase signal;

the other of the first and second components is a quadrature signal; and

the imbalance is an in-phase/quadrature imbalance.

8. A system operative to record complex parameters corresponding to frequency components of a received signal, the signal carrying at least one orthogonal frequency division multiplexing (OFDM) symbol, the parameters corresponding to:

a carrier frequency having a frequency error;

a first tone; and

a second tone,

the system configured to estimate a frequency bin corresponding to each of the carrier frequency, the first tone and the second tone;

wherein there are first and second complex parameters corresponding to each of the carrier frequency, the first tone and the second tone, the system is further operative to;

estimate a second frequency bin corresponding to each of the carrier frequency, the first tone and the second tone; and

record the first and second complex parameters for each of the carrier frequency, the first tone and the second tone;

the system further operative to record both of the complex parameters for each of the carrier frequency, the first tone and the second tone based upon an estimated value for each of the carrier frequency, the first tone and the second tone;

wherein all of the estimated values correspond to a single OFDM symbol.

9. The system of claim 8 wherein, when the received signal carries a plurality of OFDM symbols, further operative to estimate values of each of the carrier frequency, the first tone and the second tone for each of the OFDM symbols.

10. A method using one or more non-transitory computer-readable media storing computer-executable instructions which, when executed by a processor on a computer system, instruct the method to record complex parameters during a MoCA Probe2 burst reception, the parameters corresponding to frequency components of a received signal, the signal carrying at least one orthogonal frequency division multiplexing (OFDM) symbol, the parameters corresponding to:

a carrier frequency having a frequency error;

a first tone; and

a second tone;

the method further operative to estimate values of each of the carrier frequency, the first tone and the second tone for each of the OFDM symbols when the received signal during the MoCA Probe2 burst reception carries a plurality of OFDM symbols;

wherein there are first and second complex parameters corresponding to each of the carrier frequency, the first tone and the second tone, the method is further operative to;

estimate a second frequency bin corresponding to each of the carrier frequency, the first tone and the second tone; and

record the first and second complex parameters for each of the carrier frequency, the first tone and the second tone;

method further operative to record both of the complex parameters for each of the carrier frequency, the first tone and the second tone based upon an estimated value for each of the carrier frequency, the first tone and the second tone;

wherein all of the estimated values correspond to a single OFDM symbol.

11. The media of claim 10 further configured to estimate a frequency bin corresponding to each of the carrier frequency, the first tone and the second tone.