Adaptive IIP2 calibration

• US 8,150,350 B2
• Filed: 09/27/2011
• Issued: 04/03/2012
• Est. Priority Date: 10/09/2008
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Pratt, Patrick, Sobchak, Charles Leroy
• Primary Examiner(s): LE, NHAN T
• Application Number:
  US13/246,538
• Publication Number:
  US 20120015616A1
• Time in Patent Office: 189 Days
• Field of Search: 455 77- 79, 455132-135, 455/151.1, 455/205, 455/208, 455/209, 455/313, 455/323, 455/334, 455/550.1
• US Class Current: 455/209
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements

Abstract

A radio frequency transceiver (102), including a transmitter (104), a duplexer (108) and a direct-conversion receiver (106) including a mixer (140 and 141). An IIP2 calibration system (170), coupled to the transceiver, includes an IIP2 coefficient estimator (172) for calculating an estimate of second-order distortion intermodulation distortion, and an IIP2 controller (174) for adjusting an IIP2 tuning port of the mixer in the receiver to minimize second-order distortion intermodulation distortion in the receiver that may be caused by the receiver receiving a transmit RF signal leaking through the duplexer.

Claims

1. A method of tuning a input-related, second-order intercept point (IIP2) of a mixer in a receiver of a transceiver including a transmitter, comprising the steps of:

determining whether power output of the transmitter is greater than a predetermined power output level;

determining whether a received signal strength indication of the receiver is less than a predetermined received signal strength indication level;

providing values for a gain of an IIP2 estimator and an update rate of a IIP2 controller;

using the gain of the IIP2 estimator, performing an optimization algorithm for estimating an estimated value of an IIP2 coefficient that is proportional to second-order intermodulation distortion occurring in the mixer;

using the update rate of the IIP2 controller and the estimated value of the IIP2 coefficient, performing an optimization algorithm for changing a tuning voltage of the mixer;

waiting a period for a change to occur in one or both of the power output level of the transmitter and a received signal strength indication of the receiver;

after waiting the period, determining whether a change in one or both of the gain of the IIP2 estimator and the update rate of the IIP2 controller has occurred;

based upon one of or both the change of the power output level and the received signal strength indication, determining whether a change in one or both of the gain of the IIP2 estimator and the update rate of the IIP2 controller are required; and

if any such change is required, making a change in one or both of the gain of the IIP2 estimator and the update rate of the IIP2 controller, based upon information stored in a look-up table.

2. The method of claim 1, wherein the step of performing the optimization algorithm for estimating the estimated value of the IIP2 coefficient includes a step of compensating for DC offset in the receiver, thereby reducing any degradation of the estimate caused by the presence of the DC offset.

3. The method of claim 2, wherein the values for the gain of the IIP2 estimator and the update rate of the IIP2 controller are obtained from respective look-up tables, based upon the power output of the transmitter and the receiver signal strength indication of the receiver.

4. The method of claim 1, wherein the optimization algorithm is a sign-sign least means squared optimization algorithm.

5. The method of claim 4, wherein the sign-sign least means squared optimization algorithm has a variable step size, the variable step size depending on a magnitude of the IIP2 coefficient estimation.