METHOD AND APPARATUS FOR TRANSMIT POWER MODULATION IN A WIRELESS COMMUNICATIONS SYSTEM

• US 20040203979A1
• Filed: 04/01/2002
• Published: 10/14/2004
• Est. Priority Date: 04/01/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wheatley, Charles E. III, Attar, Rashid A.
• Granted Patent: US 6,873,831 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04B 7/0491 using two or more sectors, i.e. sector diversity
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0617 for beam forming

Abstract

An apparatus according to one embodiment of the invention includes a transmitter. The transmitter receives an RF signal and produces at least two modulated signals based on the RF signal. Each of the modulated signals is coupled to a respective antenna. The combined radiation pattern of the antennas varies in an angular direction over time. In a system according to one embodiment of the invention, a base station including such an apparatus receives channel quality indications from mobile units and schedules data transmissions to the mobile units accordingly.

Claims

1. A transmitter comprising:

a first gain element configured and arranged to modulate a radio-frequency signal according to a first gain factor to produce a first output signal; and

a second gain element configured and arranged to modulate the radio-frequency signal according to a second gain factor to produce a second output signal,

wherein a magnitude of the first gain factor varies over time, and

wherein a magnitude of the second gain factor varies over time with respect to the magnitude of the first gain factor.

2. The transmitter according to claim 1, wherein the magnitude of the first gain factor varies over time according to a periodic function.

3. The transmitter according to claim 1, wherein a phase of at least one among the first and second gain factors varies over time.

4. The transmitter according to claim 1, wherein at least one among a magnitude and a phase of at least one among the first and second gain factors varies over time according to a periodic function, and

wherein a period of the periodic function is not less than one-half second, and

wherein the period of the periodic function is not more than four seconds.

5. The transmitter according to claim 1, said transmitter further comprising a value generator configured and arranged to generate the first and second gain factors.

6. The transmitter according to claim 5, wherein the value generator includes a lookup table configured and arranged to store values of at least one among the first and second gain factors.

7. The transmitter according to claim 1, said transmitter further comprising an antenna array including:

a first antenna configured and arranged to radiate a signal based on the first output signal; and

a second antenna configured and arranged to radiate a signal based on the second output signal,

wherein the first and second antennas are configured and arranged such that the radiation pattern of one antenna substantially overlaps the radiation pattern of the other antenna.

8. The transmitter according to claim 7, wherein a value of at least one among the first and second gain factors at a moment of time is based on a boresite azimuth angle of the antenna array.

9. The transmitter according to claim 1, said transmitter further comprising an antenna array including:

a first antenna configured and arranged to radiate a signal based on the first output signal; and

a second antenna configured and arranged to radiate a signal based on the second output signal,

wherein the first and second antennas are separated by a distance equal to a few wavelengths of the radio-frequency signal.

10. The transmitter according to claim 1, wherein a sum of the magnitudes of the first and second gain factors is substantially constant over time.

11. The transmitter according to claim 1, said transmitter comprising at least one additional gain element, each additional gain element being configured and arranged to modulate the radio-frequency signal according to a corresponding additional gain factor to produce a corresponding additional output signal,

wherein a sum of the magnitudes of the first, second, and additional gain factors is substantially constant over time.

12. A transmitter comprising:

a first gain element configured and arranged to modulate a radio-frequency signal according to a first gain factor to produce a first output signal; and

a second gain element configured and arranged to modulate the first output signal according to a second gain factor to produce a second output signal,

wherein a magnitude of the first gain factor varies over time, and

wherein a magnitude of the second gain factor varies over time with respect to the magnitude of the first gain factor.

13. The transmitter according to claim 12, wherein the magnitude of the first gain factor varies over time according to a periodic function.

14. The transmitter according to claim 12, wherein a phase of at least one among the first and second gain factors varies over time.

15. The transmitter according to claim 12, wherein at least one among a magnitude and a phase of at least one among the first and second gain factors varies over time according to a periodic function, and

wherein a period of the periodic function is not less than one-half second, and

wherein the period of the periodic function is not more than four seconds.

16. The transmitter according to claim 12, said transmitter further comprising a value generator configured and arranged to generate the first and second gain factors.

17. The transmitter according to claim 16, wherein the value generator includes a lookup table configured and arranged to store values of at least one among the first and second gain factors.

18. The transmitter according to claim 12, said transmitter further comprising an antenna array including:

a first antenna configured and arranged to radiate a signal based on the first output signal; and

a second antenna configured and arranged to radiate a signal based on the second output signal,

wherein the first and second antennas are configured and arranged such that the radiation pattern of one antenna substantially overlaps the radiation pattern of the other antenna.

19. The transmitter according to claim 18, wherein a value of at least one among the first and second gain factors at a moment of time is based on a boresite azimuth angle of the antenna array.

20. The transmitter according to claim 12, said transmitter further comprising an antenna array including:

a first antenna configured and arranged to radiate a signal based on the first output signal; and

a second antenna configured and arranged to radiate a signal based on the second output signal,

wherein the first and second antennas are separated by a distance equal to a few wavelengths of a carrier signal of the radio-frequency signal.

21. The transmitter according to claim 12, wherein a sum of the magnitudes of the first and second gain factors is substantially constant over time.

22. The transmitter according to claim 12, said transmitter comprising at least one additional gain element, each additional gain element being configured and arranged to modulate the first output signal according to a corresponding additional gain factor to produce a corresponding additional output signal,

wherein a sum of the magnitudes of the first, second, and additional gain factors is substantially constant over time.

23. An apparatus for data transmission, said apparatus comprising:

a transmitter including an RF unit configured and arranged to output a radio-frequency signal, a first power amplifier configured and arranged to output a first amplified signal based on the radio-frequency signal, and a second power amplifier configured and arranged to output a second amplified signal based on the radio-frequency signal, and

an antenna array including a first antenna configured and arranged to receive and radiate the first amplified signal and a second antenna configured and arranged to receive and radiate the second amplified signal,

wherein a distance between the first and second antennas is a few wavelengths of a carrier signal of the radio-frequency signal, and

wherein a magnitude of the power of the first amplified signal varies over time, and

wherein a magnitude of the power of the second amplified signal varies over time with respect to the magnitude of the power of the first signal.

24. The apparatus for data transmission according to claim 23, wherein said transmitter is further configured and arranged to radiate a signal whose field intensity varies periodically over time with respect to angle in a portion of a horizontal plane centered at the antenna array.

25. The apparatus for data transmission according to claim 24, wherein a period of the variation of the field intensity is not less than one-half second and not greater than four seconds.

26. The apparatus for data transmission according to claim 23, wherein the radio-frequency signal is encoded using a CDMA scheme.

27. The apparatus for data transmission according to claim 23, said apparatus further comprising a data queue configured and arranged to store data,

wherein the RF unit is further configured and arranged to output a paging message directed to a mobile unit when the data queue stores data directed to the mobile unit.

28. The apparatus for data transmission according to claim 23, said apparatus further comprising a receiver configured and arranged to receive a channel quality indication from a mobile unit,

wherein said apparatus is further configured and arranged to transmit data directed to the mobile unit based on a value of the channel quality indication.

29. The apparatus for data transmission according to claim 28, said apparatus further comprising a scheduler configured and arranged to normalize a value of the channel quality indication by a history of data transmissions to the mobile unit.

30. The apparatus for data transmission according to claim 28, said apparatus further comprising a decoder configured and arranged to remove from the channel quality indication a predetermined code that is at least nearly orthogonal.

31. A method for data transmission, said method comprising:

applying a first gain factor to a radio-frequency signal to produce a first output signal; and

applying a second gain factor to one among the radio-frequency signal and the first output signal to produce a second output signal,

wherein said applying a first gain factor includes varying a magnitude of the first gain factor over time, and

wherein said applying a second gain factor includes varying a magnitude of the second gain factor over time with respect to the magnitude of the first gain factor.

32. The method for data transmission according to claim 31, wherein at least one among said applying a first gain factor and said applying a second gain factor includes varying at least one of a magnitude and a phase of the corresponding gain factor over time according to a periodic function, and

wherein a period of the periodic function is not less than one-half second, and

wherein the period of the periodic function is not more than four seconds.

33. The method for data transmission according to claim 31, said method further comprising retrieving a value of at least one among the first and second gain factors from a lookup table.

34. The method for data transmission according to claim 31, said method further comprising:

radiating a signal based on the first output signal over a spatial region with a first antenna of an antenna array; and

radiating a signal based on the second output signal over substantially the spatial region with a second antenna of an antenna array.

35. The method for data transmission according to claim 34, wherein at least one among said applying a first gain factor and said applying a second gain factor includes varying a magnitude of the corresponding gain factor based on a boresite azimuth angle of the antenna array.

36. The method for data transmission according to claim 31, said method further comprising:

radiating a signal based on the first output signal over a spatial region with a first antenna from a first location; and

radiating a signal based on the second output signal over substantially the spatial region with a second antenna from a first location,

wherein the first and second locations are separated by a distance equal to a few wavelengths of a carrier signal of the radio-frequency signal.

37. The method for data transmission according to claim 31, wherein a sum of the magnitudes of the first and second gain factors is substantially constant over time.

38. The method for data transmission according to claim 31, said method further comprising encoding the radio-frequency signal using a CDMA scheme.

39. The method for data transmission according to claim 31, said method further comprising:

storing data directed to a mobile unit; and

outputting a paging message directed to the mobile unit.

40. The method for data transmission according to claim 31, said method further comprising:

receiving a channel quality indication from a mobile unit; and

transmitting data directed to the mobile unit based on a value of the channel quality indication.

41. The method for data transmission according to claim 40, said method further comprising normalizing a value of the channel quality indication by a history of data transmissions to the mobile unit.

42. The method for data transmission according to claim 40, said method further comprising removing from the channel quality indication a predetermined code that is at least nearly orthogonal.