Methods and Systems for Near-Field MIMO Communications

• US 20130101005A1
• Filed: 05/26/2011
• Published: 04/25/2013
• Est. Priority Date: 06/29/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Rambus Inc.
• Inventors: Aryanfar, Farshid
• Granted Patent: US 9,319,105 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H01Q 1/2291 used in bluetooth or WI-FI devices of Wireless Local Area Networks [WLAN] H01Q1/241 takes precedence; WLAN in general H04W
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/70 specially adapted for specific purposes
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0469 taking special antenna structures, e.g. cross polarized antennas into account
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A near-field communication (NFC) system supports increased data rates using a multiple-input-multiple-output (MIMO) interface. Multiple receive antennas are positioned within the near field of multiple transmit antennas. The NFC system uses a combination of antenna spacing and polarizations to reduce correlation between channels, and thus improves performance by creating closer to ideal MIMO operation. Such system can also be operated as parallel SISO links with reduced cross-channel interference resulting in low power consumption.

Claims

1. A communication system comprising:

a transmitter circuit comprising;

a data mapping unit to divide a data signal into parallel data streams;

a plurality of transmitters connected to the data mapping unit, each transmitter tuned to a center frequency f and wavelength λ

, each transmitter to transmit a respective data stream as a respective modulated signal; and

a plurality of transmit antennas, each of a largest dimension D_i and connected to one or more respective transmitters to transmit the respective modulated signal, the transmit antennas collectively transmitting the modulated signals of the wavelength λ

;

wherein a greatest of dimensions D_i is a maximum dimension D; and

a receiver circuit comprising a plurality of receive antennas, the receive antennas to receive the signals, wherein each receive antenna is spaced from a closest one of the transmit antennas by a distance less than the greater of 2D²/λ and

λ

/2π

.

2. The system of claim 1, wherein the transmit antennas are oriented to transmit the modulated signals at respective polarizations.

3. The system of claim 2, wherein the receive antennas are oriented to receive the modulated signals at the respective polarizations.

4. The system of claim 1, wherein the receiver circuit further comprises:

a plurality of receivers, each receiver tuned to the center frequency f and wavelength λ

, each receiver connected to one or more respective receive antennas to recover the data streams from the modulated signals; and

a data recovery unit connected to the receivers to recover the data signal from the received signals.

5. The system of claim 1, wherein the transmitter circuit further comprises polarization selection logic to control the polarization selection among the plurality of transmitters and to the transmit antennas.

6. The system of claim 5, wherein each transmit antenna comprises multiple signal feeds, each feed on a given transmit antenna providing a different polarization of the respective transmitted signal, and wherein the polarization selection logic selects from among the signal feeds.

7. The system of claim 5, further comprising control circuitry connected to the polarization select logic to select from among combinations of transmit polarizations for the transmitted signals.

8. The system of claim 5, wherein the receiver circuit further comprises second polarization selection logic to select different combinations of receive polarizations for different ones of the received signals.

9. The system of claim 8, further comprising test circuitry to issue a quality measure based on the received signals.

10. The system of claim 9, further comprising control logic connected to the first and second polarization select logic to select the different transmit and receive polarizations based on the quality measure.

11. The system of claim 1, wherein ones of the transmit and receive antennas are selected from the group consisting of patch antennas and wirebond antennas.

12. The system of claim 1, wherein the number of transmit antennas equals the number of receive antennas.

13. The system of claim 1, wherein the data mapping unit is adapted to use a MIMO mapping scheme in a high performance mode and a de-multiplexing scheme in a low-power mode.

14. The system of claim 13, wherein the receiver circuit further comprises:

a plurality of receivers, each receiver tuned to the center frequency f and wavelength λ

, each receiver connected to one or more respective receive antennas to recover the data streams from the modulated signals; and

a data recovery unit connected to the receivers to recover the data signal from the received signals using a MIMO de-mapping scheme in the high-performance mode and a multiplexing scheme in the low-power mode.

15. A method comprising:

transmitting a plurality of differently polarized signals, including;

dividing a data signal into parallel data streams using a MIMO mapping scheme,

transmitting each data stream using a respective transmitter tuned to a center frequency f and wavelength λ

to produce modulated signals,

feeding the modulated signals to a plurality of transmit antennas, each transmit antenna having a largest dimension D_i, and

transmitting each of the modulated signals using a respective polarization;

wherein a greatest of the largest dimensions is a maximum dimension D; and

receiving the plurality of differently polarized signals using a plurality of receive antennas, wherein each receive antenna is spaced from a closest one of the transmit antennas by a distance of less than the greater of 2D²/λ and

λ

2/π

.

16. The method of claim 15, further comprising combining the received signals from the receive antennas to recover the data signals and analyzing the recovered data signal for signal quality.

17. The method of claim 16, further comprising adjusting the polarizations of the modulated signals based on the signal quality.

18. The method of claim 17, further comprising adjusting second polarizations of the receive antennas based on the signal quality.

19. The method of claim 15, wherein analyzing the signal quality includes measuring a bit-error rate.

20. The method of claim 15, further comprising dividing a second data signal into second parallel data streams using a de-multiplexing scheme in a low-power mode and transmitting the second parallel data streams using the transmitters.

21. A communication system comprising:

a MIMO transmitter comprising transmit antennas, each of a largest dimension D_i, to transmit a respective modulated signal of wavelength λ

;

wherein a greatest of dimensions D_i is a maximum dimension D; and

a MIMO receiver comprising receive antennas to receive the transmitted signals, wherein each receive antenna is spaced from a closest one of the transmit antennas by a distance less than the greater of 2D²/λ and

λ

/2π

.

22. The communication system of claim 21, wherein each receive antenna is spaced from a farthest one of the transmit antennas by the distance of less than the greater of 2D²/λ

and λ

/2π

.

23. The communication system of claim 22, wherein at least a subset of the transmit antennas transmit the respective radio-frequency signals at different polarizations.

24. The communication system of claim 23, wherein at least a subset of the receive antennas receive the respective radio-frequency signals at different polarizations.

25. The communication system of claim 21, further comprising means for adjusting polarizations for at least some of the transmit and receive antennas.

26. The communication system of claim 21, wherein the MIMO transmitter maps a first data signal using a MIMO mapping scheme in a high-performance mode and maps a second data signal using a parallel SISO scheme in a low-power mode.

27. The communication system of claim 26, wherein the non-MIMO mapping scheme comprises demultiplexing.

28. A communication system comprising:

a transmitter circuit comprising;

a data mapping unit to divide a data signal into parallel data streams using a MIMO mapping scheme;

a plurality of transmitters connected to the data mapping unit, each transmitter to transmit a respective data stream as a respective modulated signal of a wavelength; and

a plurality of transmit antennas connected to one or more respective transmitters to transmit the respective modulated signal, the transmit antennas collectively transmitting the modulated signals and having a near field defined by the wavelength and antenna size; and

a receiver circuit comprising a plurality of receive antennas within the near field of the transmit antennas to receive the signals.

29. The system of claim 28, wherein the transmit antennas are oriented to transmit the modulated signals at respective polarizations.

30. The system of claim 29, wherein the receive antennas are oriented to receive the modulated signals at the respective polarizations.

31. The system of claim 28, wherein the data mapping unit alternatively divides the data signal into parallel data stream using a demultiplexing scheme.