Method and system for a second order input intercept point (IIP2) correction

• US 7,421,260 B2
• Filed: 10/29/2004
• Issued: 09/02/2008
• Est. Priority Date: 10/29/2004
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Darabi, Hooman
• Primary Examiner(s): Maung; Nay
• Assistant Examiner(s): Chan; Richard
• Application Number:
  US10/976,977
• Publication Number:
  US 20060094361A1
• Time in Patent Office: 1,404 Days
• Field of Search: 455/130, 455/136, 455/317, 375/298
• US Class Current: 455/130
• CPC Class Codes: H03D 3/008 Compensating DC offsets
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/0294 Provision for current-mode coupling
• CPC Class Codes: H04L 25/0296 Arrangements to ensure DC-balance
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296

Abstract

In RF transceivers, a method and system for a second order input intercept point (IIP2) correction are provided. A DC offset sensor may detect DC offset voltages produced by blocker signals in “I” and “Q” signal component paths in an RF receiver. The DC offset sensor may generate control signals which may be utilized by a first and second injection circuits to generate DC offset currents that compensate for the DC offset voltages in the signal component paths. An injection circuit may utilize current drivers to generate binary weighted currents which may be added together to produce a DC offset current. The polarity of the DC offset current and the selection of which current drivers to use may be determined by the control signals. A calibration voltage may also be utilized to correct or adjust the gain in the injection circuit.

Claims

1. A method for a wireless receiver signal processing, the method comprising:

detecting a DC offset voltage;

generating a plurality of current driver control signals based on said detected DC offset voltage, wherein said generated plurality of current driver control signals comprise a polarity selection signal, a plurality of current driver selection signals, and a current bias signal;

generating a plurality of weighted offset currents based on said generated plurality of current driver control signals and an input voltage; and

generating a DC offset current to compensate for said detected DC offset voltage, wherein said DC offset current is based on said generated plurality of weighted offset currents.

2. The method according to claim 1, comprising selecting a number of current drivers to generate said plurality of weighted offset currents based on said plurality of current driver selection signals.

3. The method according to claim 1, comprising selecting a polarity for said plurality of weighted offset currents based on said polarity selection signal.

4. The method according to claim 1, comprising generating a reference current based on said current bias signal.

5. The method according to claim 1, comprising generating a positive polarity control signal in said plurality of current drivers by ANDing said polarity selection signal and a portion of said plurality of current driver selection signals that corresponds to each of said plurality of current drivers.

6. The method according to claim 1, comprising generating a negative polarity control signal in said plurality of current drivers by inverting said polarity selection signal and ANDing said inverted polarity selection signal and a portion of said plurality of current driver selection signals that corresponds to each of said plurality of current drivers.

7. A system for a wireless receiver signal processing, the system comprising:

a DC offset sensor that detects a DC offset voltage;

said DC offset sensor generates a plurality of current driver control signals based on said detected DC offset voltage, wherein said generated plurality of current driver control signals comprise a polarity selection signal, a plurality of current driver selection signals, and a current bias signal;

a circuit comprising a plurality of current drivers;

said DC offset sensor transfers said generated plurality of current driver control signals and an input voltage to said plurality of current drivers in said circuit;

said plurality of current drivers generate a plurality of weighted offset currents in said circuit based on said transferred generated plurality of current driver control signals and said transferred input voltage; and

said circuit generates a DC offset current to compensate for said detected DC offset voltage, wherein said DC offset current is based on said generated plurality of weighted offset currents.

8. The system according to claim 7, wherein said circuit selects a number of current drivers from said plurality of current drivers to generate said DC offset current based on said plurality of current driver selection signals.

9. The system according to claim 7, wherein said circuit selects a polarity for said plurality of weighted offset currents in said plurality of current drivers based on said polarity selection signal.

10. The system according to claim 7, wherein said plurality of current drivers generate a reference current based on said current bias signal.

11. The system according to claim 7, wherein said plurality of current drivers generate a positive polarity control signal by ANDing said polarity selection signal and a portion of said plurality of current driver selection signals that corresponds to each of said plurality of current drivers.

12. The system according to claim 7, wherein said plurality of current drivers generate a negative polarity control signal by inverting said polarity selection signal and ANDing said inverted polarity selection signal and a portion of said plurality of current driver selection signals that corresponds to each of said plurality of current drivers.

13. A system for a wireless receiver signal processing, the system comprising:

a DC offset sensor that detects a DC offset voltage;

said DC offset sensor generates a plurality of current driver control signals based on said detected DC offset voltage;

a circuit comprising a plurality of current drivers, wherein an injection circuit selects said input voltage by turning ON a third switch and a fourth switch and turning OFF a first switch and a second switch in said circuit and where said selected input voltage corresponds to a calibration signal;

said DC offset sensor transfers said generated plurality of current driver control signals and an input voltage to said plurality of current drivers in said circuit;

said plurality of current drivers generate a plurality of weighted offset currents in said circuit based on said transferred generated plurality of current driver control signals and said transferred input voltage; and

said circuit generates a DC offset current to compensate for said detected DC offset voltage, wherein said DC offset current is based on said generated plurality of weighted offset currents.

14. The system according to claim 13, wherein said circuit generates a calibration DC offset current based on said calibration signal.

15. The system according to claim 14, wherein said DC offset sensor detects a calibration DC offset voltage produced by said generated calibration DC offset current.

16. The system according to claim 15, wherein said DC offset sensor stores said detected calibration DC offset voltage.