WIDEBAND QUADRATURE ERROR CORRECTION

• US 20150030102A1
• Filed: 07/25/2013
• Published: 01/29/2015
• Est. Priority Date: 07/25/2013
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Hormis, Raju, Bal, Steven R., Gard, Kevin Glenn, Fan, Jianxun, McLaurin, David J., Montalvo, Antonio
• Granted Patent: US 9,300,444 B2
• Time in Patent Office: Days
• US Class Current: 375/296
• CPC Class Codes: H03F 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H03F 2203/45512 the FBC comprising one or more capacitors, not being switched capacitors, and being coupled between the LC and the IC
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 17/17 Detection of non-compliance or faulty performance, e.g. response deviations H04B17/18 takes precedence
• CPC Class Codes: H04B 17/18 Monitoring during normal operation
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04L 1/243 at the transmitter, using a loop-back
• CPC Class Codes: H04L 27/364 Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels
• CPC Class Codes: H04L 27/366 Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator

Abstract

A transmission module is provided that includes a transmitter, a loopback receiver, and a QEC controller. In a first state, the QEC controller calibrates the loopback receiver to remove quadrature imbalance in the loopback receiver. In a second state, a communication pathway is provided between the transmitter and the loopback receiver, and the QEC controller identifies quadrature imbalance in the transmitter based at least one a comparison of the data signals at the output of the loopback receiver with data signals at the input of the transmitter. Based on the comparison, the QEC controller can adjust one or more characteristics of the transmitter to correct quadrature errors in the transmitter.

Claims

1. A transmission module comprising:

a switching module;

a transmitter communicatively coupled to the switching module;

a loopback receiver communicatively coupled to the switching module;

a calibration module communicatively coupled to the switching module; and

a controller communicatively coupled to the loopback receiver and the transmitter;

wherein in a first state, the switching module is configured to provide a communication pathway between an output of the calibration module and an input of the loopback receiver, and the controller is configured to identify and correct quadrature imbalance in the loopback receiver based at least on a comparison of the output of the loopback receiver with an expected output;

wherein in a second state, the switching module is configured to provide a communication pathway between an output of the transmitter and an input of the loopback receiver, and the controller is configured to;

identify quadrature imbalance in the transmitter based at least partly on a comparison of a data signal received from the loopback receiver with a buffered data signal that corresponds to a data signal received by the transmitter, and

adjust one or more characteristics of the transmitter to correct the identified quadrature imbalance present in the transmitter based at least partly on the comparison.

2. A transmission module comprising:

a transmitter;

a loopback receiver; and

a controller configured to;

calibrate the loopback receiver to account for quadrature imbalance in the loopback receiver,

receive a data signal from the calibrated loopback receiver that corresponds to a data signal received by the transmitter,

identify quadrature imbalance in the transmitter based at least partly on a comparison of the data signal received from the calibrated loopback receiver with a buffered data signal that corresponds to the data signal received by the transmitter, and

adjust one or more characteristics of the transmitter to correct the identified quadrature imbalance based at least partly on the comparison.

3. The transmission module of claim 2, further comprising:

a switching module communicatively coupled between an output of a calibration module, an input of the loopback receiver and an output of the transmitter,

wherein in a first state, the switching module is configured to provide a communication pathway between the output of the calibration module and the input of the loopback receiver;

wherein in a second state, the switching module is configured to provide a communication pathway between the output of the transmitter and the input of the loopback receiver;

wherein during calibration of the loopback receiver, the switching module is configured to operate in the first state.

4. The transmission module of claim 3, wherein the switching module further comprises:

at least one of a first buffer and a first switch in a signal path between the output of the calibration module and the input of the loopback receiver; and

at least one of a second buffer and a second switch in a signal path between the output of the transmitter and the input of the loopback receiver.

5. The transmission module of claim 4, wherein the switching module further comprises a loopback filter configured to filter higher-order harmonic signals in data signals received from the transmitter.

6. The transmission module of claim 2, wherein the controller is configured to:

identify the quadrature imbalance present in the loopback receiver based at least partly on a comparison of a data signal received from the output of the loopback receiver with an expected output data signal, and

adjust one or more characteristics of the loopback receiver based at least partly on the identified quadrature imbalance.

7. The transmission module of claim 6, wherein the controller is further configured to adjust at least one of a local oscillator delay of the loopback receiver and one or more filters of the loopback receiver to adjust one or more characteristics of the loopback receiver.

8. The transmission module of claim 2, wherein the quadrature imbalance in the transmitter comprise phase error and amplitude error.

9. The transmission module of claim 8, wherein the phase error comprises baseband frequency independent phase error and baseband frequency dependent phase error.

10. The transmission module of claim 9, wherein to correct the baseband frequency independent phase error, the controller is configured to adjust at least one of a complex digital filter and a local oscillator delay in a local oscillator circuit.

11. The transmission module of claim 10, wherein to adjust the local oscillator delay, the controller is further configured to adjust at least one of a variable capacitor, a variable resistor, and a current starved inverter.

12. The transmission module of claim 9, wherein to correct baseband frequency dependent phase error, the controller is configured to adjust at least one of a complex digital filter and a baseband filter delay.

13. The transmission module of claim 12, wherein to adjust a baseband filter delay the controller is configured to adjust at least one of a variable capacitor, a variable resistor, a digital filter, and a voltage controlled varactor.

14. An electronically-implemented method for quadrature error correction comprising:

calibrating a loopback receiver to account for quadrature imbalance in the loopback receiver;

receiving, from the calibrated loopback receiver, a data signal that has been processed by the calibrated loopback receiver and that corresponds to a data signal received by a transmitter communicatively coupled with the loopback receiver;

identifying quadrature imbalance in the transmitter based at least partly on a comparison of the data signal received from the calibrated loopback receiver with a buffered data signal that corresponds to the data signal received by the transmitter, and

adjusting one or more characteristics of the transmitter to correct the identified quadrature imbalance based at least partly on the comparison.

15. The method of claim 14, wherein calibrating the loopback receiver comprises:

providing a communication pathway between an output of a calibration module and an input of the loopback receiver;

processing a data signal received from the calibration module using the loopback receiver;

identifying quadrature imbalance in the loopback receiver based at least partly on a comparison of the processed data signal with an expected output of the loopback receiver; and

adjusting one or more characteristics of the loopback receiver based at least partly on the identified quadrature imbalance in the loopback receiver.

16. The method of claim 15, wherein adjusting one or more characteristics of the loopback receiver comprises adjusting at least one of a local oscillator delay of the loopback receiver and one or more filters of the loopback receiver.

17. The method of claim 16, wherein the quadrature imbalance in the transmitter comprises phase error and amplitude error.

18. The method of claim 17, wherein the phase error comprises baseband frequency independent phase error and baseband frequency dependent phase error.

19. The method of claim 18, further comprising adjusting a local oscillator delay in a local oscillator circuit to correct the baseband frequency independent phase error.

20. The method of claim 18, further comprising adjusting a baseband filter delay to correct baseband frequency dependent phase error.

21. The method of claim 20, wherein adjusting the baseband filter delay comprises adjusting at least one of a variable capacitor, a variable resistor, a digital filter, and a voltage controlled varactor.