Direct-conversion transceiver enabling digital calibration

• US 20040106380A1
• Filed: 09/02/2003
• Published: 06/03/2004
• Est. Priority Date: 09/03/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Yamanaka, Akira, Vassiliou, Iason, Plevridis, Sofoklis, Vavelidis, Konstantinos, Georgantas, Theodore
• Granted Patent: US 7,715,836 B2
• Time in Patent Office: Days
• US Class Current: 455/73
• CPC Class Codes: H04B 1/38 Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 17/20 of receivers

Abstract

A transceiver for transmitting and receiving signals includes a transmitter operative to up-convert baseband signals from a baseband frequency into RF signals at a radio frequency (RF) frequency and output the RF signals, a receiver operative to receive RF signals and down-convert the RF signals into baseband signals having the baseband frequency, and a plurality of calibration paths coupling the transmitter to the receiver. Any of the calibration paths can be selected to be active when calibrating components of the transceiver. Tunable components can use calibration information to optimize transceiver performance.

Claims

1. A transceiver for transmitting and receiving signals, the transceiver comprising:

a transmitter operative to up-convert baseband signals from a baseband frequency into RF signals at a radio frequency (RF) frequency and output the RF signals;

a receiver operative to receive RF signals and down-convert the RF signals into baseband signals having the baseband frequency; and

a plurality of calibration paths coupling the transmitter to the receiver, wherein any of the calibration paths can be selected to be active when calibrating components of the transceiver.

2. The transceiver of claim 1 wherein the transceiver is a direct up-conversion and down-conversion architecture, and includes baseband analog transmit filters having responses which can be measured for calibration using one of the calibration paths.

3. The transceiver of claim 2 wherein one of the calibration paths includes a loopback connection that couples the transmitter to the receiver.

4. The transceiver of claim 3 further comprising digital-to-analog converters (DACs) coupled to the transmit filters, and controllable to tune the transmit filters based on the measurements of the transmit filters over the calibration path.

5. The transceiver of claim 1 further comprising baseband analog receive filters which have responses which can be measured for calibration using the one of the calibration paths.

6. The transceiver of claim 5 further comprising digital-to-analog converters (DACs) coupled to the receive filters, and controllable to tune the receive filters based on the measurements of the receive filters over the calibration path.

7. The transceiver of claim 1 wherein the selected calibration path is selected to be active by a processor coupled to the transceiver and which controls the calibrations of the components of the transceiver.

8. The transceiver of claim 7 wherein one of the calibration paths includes a loopback connection connected from the RF output of the transmitter to the processor controlling the calibrations, wherein the loopback connection includes an envelope detector to allow transmit I/Q mismatch to be measured by the processor.

9. The transceiver of claim 8 wherein the loopback connection is active only when the I/Q mismatch measurement is occurring.

10. The transceiver of claim 8 wherein the loopback connection and envelope detector allow estimation of leakage of a local oscillator (LO) included in the transceiver.

11. The transceiver of claim 8 wherein the measured transmit I/Q mismatch is removed from signals that are transmitted by the transmitter by using digital pre-distortion.

12. The transceiver of claim 8 wherein the estimated LO leakage is compensated in signals that are transmitted by the transmitter by using digital pre-distortion.

13. The transceiver of claim 7 wherein one of the calibration paths includes a loopback connection connected from the RF output of the transmitter to the input of the receiver, wherein the loopback connection allows receive I/Q mismatch to be measured by the processor.

14. The transceiver of claim 13 wherein the processor provides a calibration signal to the transmitter to measure the receive I/Q mismatch, wherein the calibration signal is digitally pre-distorted by the processor to remove transmit I/Q mismatch.

15. The transceiver of claim 13 wherein the measured receive I/Q mismatch is removed from signals that are received by the receiver by using digital post-distortion.

16. The transceiver of claim 1 wherein the receiver includes a plurality of digital-to-analog converters (DACs) which are controllable to remove baseband path DC offset independently for I and Q paths of the receiver.

17. The transceiver of claim 1 wherein the transmitter and the receiver each include baseband analog filters, and wherein the filter responses can be measured such that residual mismatch between two filters can be removed by digital pre-distortion of a signal to be transmitted.

18. The transceiver of claim 1 wherein the transceiver is implemented as a Complementary Metal Oxide Semiconductor (CMOS) integrated circuit chip.

19. The transceiver of claim 1 wherein the transceiver is a dual-band transceiver capable of receiving RF signals in two different RF frequency bands.

20. A method for implementing a transceiver for transmitting and receiving signals, the method comprising:

(a) calibrating components of the transceiver by using a plurality of calibration paths of the transceiver, wherein each of the calibration paths can be selected to be active when calibrating associated components of the transceiver and to be inactive when not calibrating the associated components;

(b) transmitting radio frequency (RF) signals with a transmitter by up-converting baseband signals having a baseband frequency into the RF signals and outputting the RF signals; and

(c) receiving RF signals with a receiver and down-converting the RF signals into baseband signals having the baseband frequency.

21. The method of claim 20 wherein the up-conversion and down-conversion are direct, and wherein the calibration of components includes measuring the responses of baseband analog transmit filters for calibration using one of the calibration paths.

22. The method of claim 21 wherein one of the calibration paths includes a loopback connection that couples the transmitter to the receiver.

23. The method of claim 22 further comprising converting digital control signals to analog signals using digital-to-analog converters (DACs) coupled to the transmit filters, and tuning the transmit filters using the analog signals based on the measurements of the transmit filters over the calibration path.

24. The method of claim 21 wherein the calibration of components includes measuring the responses of baseband analog receive filters for calibration using one of the calibration paths.

25. The method of claim 24 further comprising digital-to-analog converters (DACs) coupled to the receive filters, and controllable to tune the receive filters based on the measurements of the receive filters over the calibration path.

26. The method of claim 20 wherein the calibration of components includes selecting one of the calibration paths to be active by a processor coupled to the transceiver and which controls the calibrations of the components of the transceiver.

27. The method of claim 26 wherein the calibration of components includes measuring transmit I/Q mismatch using one of the calibration paths that includes a loopback connection connecting the transmitter to the processor controlling the calibrations.

28. The method of claim 27 wherein the measuring of transmit I/Q mismatch includes providing a calibration signal and detecting an envelope of the calibration signal at the output of the transmitter.

29. The method of claim 28 wherein the calibration of components includes removing the measured transmit I/Q mismatch from signals that are transmitted by the transmitter by using digital pre-distortion.

30. The method of claim 28 wherein the calibration of components includes estimating the leakage of a local oscillator (LO) included in the transceiver.

31. The method of claim 30 wherein LO leakage is estimated from the detected envelope of the calibration signal.

32. The method of claim 31 wherein the calibration of components includes compensating for the LO leakage in signals that are to be transmitted by the transmitter by using digital pre-distortion.

33. The method of claim 26 wherein the calibration of components includes measuring receive I/Q mismatch using at least one calibration path that includes a loopback connection connecting the transmitter to the processor controlling the calibrations.

34. The method of claim 33 wherein the measuring of receive I/Q mismatch includes providing a calibration signal to the transmitter, wherein the calibration signal is digitally pre-distorted by the processor to remove transmit I/Q mismatch.

35. The method of claim 34 wherein the calibration of components includes removing the measured receive I/Q mismatch from signals that are received by the receiver by using digital post-distortion.

36. The method of claim 20 wherein the calibration of components includes removing baseband path DC offset independently for I and Q paths of the receiver.

37. The method of claim 36 wherein the removing of DC offset includes providing analog correction signals to adjust the voltage added at the output of a demodulator of the transceiver using a plurality of digital-to-analog converters (DACs).

38. The method of claim 20 wherein the calibration of components includes removing residual mismatch between two analog filters included in transceiver by measuring the filter responses and providing digital pre-distortion variations to signals that are to be transmitted.

39. The method of claim 20 wherein the calibration of components includes fine tuning gain mismatch between two analog filters included in transceiver by measuring the filter responses at different gain settings and providing digital post-distortion variations to signals that are received.

40. A method for calibrating a transceiver, the method comprising:

(a) selecting one of a plurality of available calibration paths on the transceiver to be active;

(b) providing a calibration signal to the transceiver;

(c) receiving the calibration signal after it has passed through the selected calibration path; and

(d) measuring characteristics of the transceiver using the received calibration signal, wherein the measured characteristics are used in the calibration of the transceiver.

41. The method of claim 40 wherein the calibration paths on the transceiver are not active when the transceiver is not being calibrated.

42. The method of claim 41 wherein the selecting a calibration path includes setting at least one switch on the transceiver.

43. The method of claim 40 wherein the selected calibration path connects the output of a transmitter on the transceiver to an envelope detector, and wherein the selected calibration path is used to calibrate transmit I/Q mismatch and local oscillator leakage.

44. The method of claim 40 wherein the selected calibration path connects the output of a transmitter on the transceiver to the input of a receiver on the transceiver, and wherein the selected calibration path is used to calibrate receive I/Q mismatch.

45. The method of claim 40 wherein the selected calibration path connects the output of analog filters of a transmitter on the transceiver to a processor controlling the calibration signal, and wherein the selected calibration path is used to calibrate the transmitter filters.

46. The method of claim 40 wherein the selected calibration path connects a processor controlling the calibration signal to the input of analog filters of a receiver on the transceiver, and wherein the selected calibration path is used to calibrate the receiver filters.

47. The method of claim 40 further comprising adjusting digital-to-analog converters (DACs) on the transceiver to calibrate components of the transceiver.

48. The method of claim 47 wherein the adjustment of the DACs is used to calibrate transmit and receive filters and DC offset of the receiver baseband path.