System and method for adaptive antenna impedance matching

• US 6,845,126 B2
• Filed: 04/25/2003
• Issued: 01/18/2005
• Est. Priority Date: 01/26/2001
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Dolman, Rodney A., Dent, Paul W.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US10/423,713
• Publication Number:
  US 20030193997A1
• Time in Patent Office: 634 Days
• Field of Search: 375/219, 375/316, 375/295, 375/296, 375/285, 375/346, 455/73, 455/83, 455/324, 455/84, 455/85, 455/86, 455/87
• US Class Current: 375/219
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/0057 using diplexing or multiplexing filters for selecting the desired band
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

A transceiver includes a transmitter and a homodyne receiver, wherein the receiver is used to process both antenna-received and antenna-reflected signals. Thus, during a receive mode, for example, the receiver downconverts antenna-received signals to baseband signals, which are then processed to recover receive signal information. Then, during a transmit mode for example, antenna-reflected transmit signals are fed back to the receiver, which is retuned to the desired transmit frequency, and thus downconverts the reflected transmit signals to baseband signals. These baseband signals are then processed to obtain a characterization of impedance mismatch between the transceiver'"'"'s transmitter and the associated antenna. An adjustable matching network disposed in the transmit signal path thus may be adjusted based on the characterization to reduce the mismatch. Such configurations may be used with either single-band or multi-band embodiments of the transceiver, and the transceiver may be used in both TDMA and CDMA communication systems.

Claims

1. In a transceiver comprising a transmitter and a homodyne receiver, a method of characterizing an impedance mismatch between the transmitter and an associated antenna, the method comprising:

configuring the homodyne receiver to receive and downconvert antenna-received signals to baseband signals during a first mode of transceiver operation and to receive and downconvert antenna-reflected signals to baseband signals during a second mode of transceiver operation; and

processing the baseband signals generated by the homodyne receiver in the first mode to obtain received signal data and processing the baseband signals generated by the homodyne receiver in the second mode to characterize an impedance mismatch between the transmitter and the associated antenna.

2. The method of claim 1, further comprising defining the first mode of transceiver operation as a receive mode, and the second mode of transceiver operation as a transmit mode, such that the antenna-reflected signals downconverted by the homodyne receiver during the second mode of operation comprise transceiver transmit signals reflected by the associated antenna.

3. The method of claim 2, operating the transceiver in the first mode during a designated receive time slot and operating the transceiver in the second mode during a designated transmit time slot.

4. The method of claim 3, comprising alternating transceiver operation between the first and second modes over a succession of alternating receive and transmit time slots.

5. The method of claim 1, wherein configuring the homodyne receiver to receive and downconvert antenna-received signals to baseband signals during a first mode of transceiver operation comprises generating a mixing signal at a receive frequency to be used for downconverting the antenna-received signals to baseband.

6. The method of claim 5, wherein configuring the homodyne receiver to receive and downconvert antenna-reflected signals to baseband signals during a second mode of transceiver operation comprises generating the mixing signal at a transmit frequency to be used for downconverting the antenna-reflected signals to baseband, and to be used for generating a transmit signal at the transmit frequency.

7. The method of claim 6, further comprising modulating the mixing signal during the second mode of transceiver operation according to desired transmit signal information such that the antenna-reflected signals are downconverted to baseband signals coherently with transmit signal modulations.

8. The method of claim 7, further comprising generating a transmit signal for transmission from the associated antenna based on amplifying the modulated mixing signal.

9. The method of claim 1, further comprising downconverting the antenna-received signals using an unmodulated mixing signal at a receive frequency, and downconverting the antenna-reflected signals using a modulated mixing signal at a transmit frequency, the modulated mixing signal being modulated according to desired transmit signal information.

10. The method of claim 1, wherein the transceiver is included in a mobile station operating according to the Wideband CDMA (WCDMA) standards.

11. The method of claim 1, wherein the transceiver is included in a mobile station operating according to the Global Standard for Mobile communications (GSM) standards.

12. The method of claim 1, further comprising adjusting an impedance matching circuit in a transmit signal path based on the characterized impedance mismatch obtained by processing the baseband signals generated by the homodyne receiver in the second mode.

13. The method of claim 1, wherein processing the baseband signals generated by the homodyne receiver in the second mode to characterize an impedance mismatch between the transmitter and the associated antenna comprises computing an averaged impedance mismatch value over two or more transmit symbol times defined for the transmit signal.

14. The method of claim 1, wherein processing the baseband signals generated by the homodyne receiver in the second mode to characterize an impedance mismatch between the transmitter and the associated antenna comprises compensating the baseband signals using a stored phase shift value that characterizes a receiver-to-transmitter phase shift experience by the antenna-reflected signals relative to the transmit signal.

15. The method of claim 1, further comprising determining whether the baseband signal is affected by any dc errors, storing one or more values to characterize dc errors, if any, and compensating the baseband signals for dc errors using the stored values.

16. A transceiver to transmit and receive signals from an associated antenna, the transceiver including:

a homodyne receiver to generate a baseband signal by downconverting antenna-received signals in a first transceiver mode and by downconverting antenna-reflected signals in a second transceiver mode, said antenna-reflected signals being reflected transmit signals of the transceiver; and

a processing and control circuit to characterize an impedance mismatch between a transmitter portion of the transceiver and the associated antenna based on processing the baseband signal in the second transceiver mode.

17. The transceiver of claim 16, wherein the homodyne receiver includes a first receiver input coupled to the associated antenna and operative to receive the antenna-received signals and a second receiver input coupled to an output of the transmitter portion of the receiver and operative to receive the antenna-reflected signals.

18. The transceiver of claim 17, wherein a directional coupler provides the antenna-reflected signals to the second receiver input of the homodyne receiver.

19. The transceiver of claim 16, wherein the homodyne receiver includes a selectable input amplifier that amplifies the antenna-received signals in the first transceiver mode and amplifies the antenna-reflected signals in the second transceiver mode.

20. The transceiver of claim 19, wherein the control and processing circuit controls the selectable input amplifier.

21. The transceiver of claim 16, wherein the transmitter portion of the transceiver includes a directional coupler positioned in a transmitter output signal path to obtain the antenna-reflected signals as reflected transmit signals resulting from an impedance mismatch between the transmitter portion of the transceiver and the associated antenna.

22. The transceiver of claim 21, wherein the homodyne receiver includes a receiver input filter coupled to a homodyne receiver input to filter the antenna-received signals, and wherein the antenna-reflected signals bypass the receiver input filter.

23. The transceiver of claim 22, further comprising a second directional coupler to couple the antenna-reflected signals to the homodyne receiver input.

24. The transceiver of claim 16, further comprising a local oscillator circuit that generates a non-modulated mixing signal at a receive frequency for downconverting the antenna-received signals in the first transceiver mode, and generates a modulated mixing signal at a transmit frequency for downconverting the antenna-reflected signals in the second transceiver mode.

25. The transceiver of claim 24, wherein the control and processing circuit generates a modulation signal to control generation of the modulated mixing signal.

26. The transceiver of claim 25, wherein the transmitter portion of the transceiver generates the transmit signals by amplifying the modulated mixing signal, such that transmit signal modulations are substantially removed from the baseband signal generated by the homodyne receiver during operation in the second transceiver mode, thereby simplifying characterization of impedance mismatches.

27. The transceiver of claim 26, wherein the control circuit averages the baseband signal over a number of modulation symbol periods of the modulated mixing signal to reduce effects of any dc offsets in the homodyne receiver that affect generation of the baseband signal.