System for reducing multipath fade of RF signals in a wireless data application

• US 20020147031A1
• Filed: 01/26/2001
• Published: 10/10/2002
• Est. Priority Date: 01/26/2001
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Hood, Charles D. III
• Granted Patent: US 6,778,844 B2
• Time in Patent Office: Days
• US Class Current: 455/562.1
• CPC Class Codes: H01Q 1/2258 used with computer equipment
• CPC Class Codes: H01Q 3/06 over a restricted angle
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity

Abstract

In a wireless LAN, a technique for mitigating the effects of signal fading that results from multipath propagation. The wireless LAN includes a number of portable clients that, in one embodiment, may be notebook computers. An access point, or hub, couples the clients to a wired network and/or to each other. Multipath effects are mitigated in one embodiment by continually varying the radiation pattern of a transmitting antenna system associated with the access point. In an alternative embodiment, the radiation pattern of a receiving antenna system is continually varied. The invention contemplates numerous approaches to continually varying the radiation pattern of the respective antenna system, including, but not limited to, switching between two or more antennas in an array, adjusting the physical positioning of a single or multiple antennas, adjusting the effective length of the antenna, and adjusting the respective gain and/or phase of each of one or more of the signals coupled to antennas in an array.

Claims

1. A wireless communication system comprising:

a plurality of client devices, each of the client devices comprising a receiver for receiving a wireless communications signal;

an access point comprising a transmitter and a connector for coupling the transmitter to an antenna system;

an antenna system coupled to the access point; and

an antenna controller coupled to the antenna system, the antenna controller operable to continually vary the radiation pattern of the antenna system.

2. In a wireless communications system for coupling a plurality of client devices to a network, an access point comprising;

a transmitter;

an antenna system; and

an antenna system controller coupled to the antenna system and comprising a mechanism for causing substantially continual variation of the radiation pattern of the antenna system.

3. An access point as defined in claim 2, wherein the antenna system consists essentially of a single antenna.

4. An access point as defined in claim 3, wherein the antenna system controller comprises a mechanism that substantially continually varies the spatial position of the single antenna.

5. An access point as defined in claim 4, wherein the mechanism substantially continually rotates the antenna about an axis.

6. An access point as defined in claim 4, wherein the mechanism substantially continually varies the position of the antenna along a substantially linear path.

7. An access point as defined in claim 4, wherein the mechanism substantially varies the antenna around a substantially circular path.

8. In a wireless LAN, a method of mitigating the effects of multipath signal propagation between an access point and a receiving client, the method comprising:

transmitting a wireless signal from the access point to the receiving client, and

continually varying a radiation pattern of an antenna system during transmission of the wireless signal.

9. A method as defined in claim 8, wherein the radiation pattern of an antenna system associated with the access point is continually varied.

10. A method as defined in claim 9, wherein the radiation pattern of the antenna system is varied by varying orientation of an antenna element in the antenna system.

11. A method as defined in claim 10, wherein the radiation pattern of the antenna system is varied by rotating an antenna element in the antenna system.

12. A method as defined in claim 10, wherein the radiation pattern of the antenna system is varied by moving an antenna element in the antenna system along a substantially linear path.

13. A method as defined in claim 10, wherein the radiation pattern of the antenna system varied by moving an antenna element in the antenna system along a substantially circular path.

14. A method as defined in claim 9, the radiation pattern of the antenna system is continuously varied by continuously varying at least the phase of signals coupled to individual antennas included in the antenna system.

15. A method as defined in claim 14, wherein the radiation pattern of the antenna system is continuously varied by varying at least the gain of respective signals coupled to individual antennas included in the antenna system.

16. A method as defined in claim 9, wherein the radiation pattern of the antenna system is continuously varied by varying the gain and phase of respective signals coupled to individual antennas included in the antenna system.

17. A method as defined in claim 9, wherein the radiation pattern of the antenna system is continuously varied by varying the length of an antenna included in the antenna system.

18. A method as defined in claim 17, wherein the length of the antenna is varied by switching between two or more antennas with different lengths.

19. A method as defined in claim 18, wherein the length of the antenna is varied by sequentially adding one or more discrete lengths of antenna to a fixed length of antenna.

20. A method as defined in claim 9, wherein the radiation pattern of the antenna system is continuously varied by:

providing an antenna system that includes a plurality of antennas, each of the antennas exhibiting a respective radiation pattern; and

selectively sequentially coupling the wireless signal to a first antenna, decoupling the wireless signal from the first antenna, and coupling the wireless signal to a second antenna.

21. In a wireless LAN, an antenna system for continually varying the propagation pattern of a wireless signal that is transmitted from an access point to a client, the antenna system comprising:

an antenna array;

means for coupling the antenna array to the access point; and

and antenna controller coupled to the antenna array for continually varying the radiation pattern of the antenna array so as to continually vary the wireless signal received by the client.

22. A computer system comprising:

a portable computer;

a network server;

an access point coupled to the network server via a wired communications link and coupled to the portable computer via a wireless communications link;

an antenna system coupled to the access point; and

an antenna controller coupled to the antenna system for continually varying the radiation pattern of the antenna system while a wireless signal is transmitted from the access point to the portable computer.

23. A computer system as defined in claim 22, wherein the antenna controller varies the radiation pattern of the antenna system by varying the physical position of an antenna in the antenna system.

24. A computer system as defined in claim 22, wherein the antenna controller varies the radiation pattern of the antenna system by varying the physical orientation of an antenna in the antenna system.

25. A computer system as defined in claim 24, wherein the antenna controller rotates an antenna in the antenna system about an axis of the antenna.

26. A computer system as defined in claim 22, wherein the antenna controller varies the length of an antenna in the antenna system.

27. A computer system as defined in claim 22, wherein the antenna controller varies the gain and/or phase of a signal to be applied to at least one antenna included in the antenna system.

29. A computer system as defined in claim 28, wherein the control means operates to vary the radiation pattern of the antenna system by continually varying the spatial orientation of at least an antenna in the antenna system.

30. A computer system as defined in claim 28, wherein the control means operates to vary the radiation pattern of the antenna system by sequentially selecting one or more antennas for operation from an array of antennas that individually exhibit mutually different radiation patterns.

31. A computer system as defined in claim 28, wherein the control means operates to vary the radiation pattern of the antenna system by continually varying the gain and/or phase of a signal that is applied to at least one antenna in the antenna system for transmission to the client device.

32. A computer system as defined in claim 28, wherein the control means comprises an antenna controller that is coupled to the communications device to receive a T_x signal that indicates that the communications device is engaged in a transmitting session.

33. A computer system as defined in claim 32, wherein the antenna system consists essentially of a single antenna and wherein the antenna controller operates to cause the radiation pattern of the antenna to vary continually during a transmitting session by continually varying the spatial orientation of the antenna.

34. A computer system as defined in claim 33, wherein the antenna controller effects open-loop control of the radiation pattern of the antenna system.

35. A computer system as defined in claim 28, wherein the antenna system comprises a plurality of antennas, each of which is characterized by a respective radiation pattern, and wherein the control means comprises an antenna controller that is coupled to the communications device to receive a T_x signal that indicates that the communications device is operating in a transmit mode.

36. A computer system as defined in claim 35, wherein the antenna controller comprises:

a signal splitter having an input coupled to a signal provided by the communications device for transmission to the client;

having a plurality of outputs;

a plurality of gain/phase modules, each of the gain/phase modules having a signal input coupled to an output of the signal splitter and having an output; and

a gain/phase controller having a plurality of outputs, each respective coupled to a control input of one of the gain/phase modules, the gain/phase controller for adjusting the gain and/or phase imparted to the signals applied to the signal inputs of the gain/phase modules.

28. A computer system comprising:

a client device;

a communications device coupled to the client device via a wireless first communications link and coupled to a source of networked resources via a second communications link;

an antenna system coupled to the communications device in a manner that enables the communications device to transmit signals to and to receive signals from the client device; and

control means coupled to the antenna system for varying the radiation pattern of the antenna system as information is transmitted from the communications device to the client device.