What is claimed is:
1. A method of performing diversity antenna selection, comprising the steps of:
taking measurements from L different antenna branches n antenna branches at a time;
using the measurements to identify a group of n of the L different antenna branches that minimizes an approximate bit error probability of a signal that will eventually be constructed from sub-carriers that are each received by any one of the n antenna branches in the identified group of n antenna branches; and
selecting the identified group of n antenna branches.
2. A method in accordance with claim 1, wherein the measurements comprise power measurements of each of K sub-carriers.
3. A method in accordance with claim 2, wherein the step of using the measurements to identify a group of n of the L different antenna branches further comprises the step of:
computing an approximate bit error probability for each of the K sub-carriers for each of the L antenna branches n antenna branches at a time.
4. A method in accordance with claim 3, wherein the step of using the measurements to identify a group of n of the L different antenna branches further comprises the steps of:
forming different groupings of n antenna branches from among the L different antenna branches; and
for each different grouping of n antenna branches, selecting a minimum one of the approximate bit error probabilities for each one of the K sub-carriers.
5. A method in accordance with claim 4, wherein the step of using the measurements to identify a group of n of the L different antenna branches further comprises the step of:
for each different grouping of n antenna branches, summing the minimum ones of the approximate bit error probabilities that were selected for each one of the K sub-carriers.
6. A method in accordance with claim 5, wherein the step of using the measurements to identify a group of n of the L different antenna branches further comprises the steps of:
determining which sum of the minimum ones of the approximate bit error probabilities has a smallest value; and
selecting the grouping of n antenna branches that produced the sum of the minimum ones of the approximate bit error probabilities having the smallest value.
7. A method in accordance with claim 1, further comprising the step of:
calibrating a gain between n radio frequency (RF) receive paths.
8. A method in accordance with claim 7, wherein the step of calibrating a gain between n RF receive paths further comprises the steps of:
measuring a signal power received by a first one of the L antenna branches with a first receive path; and
measuring the signal power received by the first one of the L antenna branches with a second receive path.
9. A method in accordance with claim 3, wherein the step of computing an approximate bit error probability for each of the K sub-carriers for each of the L antenna branches n antenna branches at a time further comprises the step of:
computing an approximate power magnitude for each of the K sub-carriers for each of the L antenna branches n antenna branches at a time based on the power measurements.
10. A method in accordance with claim 9, wherein the step of computing an approximate bit error probability for each of the K sub-carriers for each of the L antenna branches n antenna branches at a time further comprises the step of:
approximating a Q-function for each of the K sub-carriers for each of the L antenna branches n antenna branches at a time with a corresponding approximate power magnitude comprising an argument thereof.
11. A method in accordance with claim 3, wherein the step of using the measurements to identify a group of n of the L different antenna branches further comprises the step of:
storing the computed approximate bit error probabilities.
12. A method in accordance with claim 4, wherein the step of forming different groupings of n antenna branches from among the L different antenna branches comprises the step of:
multiplexing approximate bit error probabilities corresponding to n antenna branches.
13. A method in accordance with claim 2, wherein the K sub-carriers form an orthogonal frequency division multiplexing (OFDM) signal.
14. A method in accordance with claim 1, wherein the step of taking measurements from L different antenna branches n antenna branches at a time comprises the steps of:
receiving a frame that includes a diversity selection portion comprising one or more antenna branch probing portions; and
taking measurements from n antenna branches during one of the antenna branch probing portions.
15. A method in accordance with claim 14, wherein the step taking measurements from n antenna branches during one of the antenna branch probing portions comprises the step of:
taking measurements from each one of the n antenna branches with a separate one of n radio frequency receivers.
16. A method in accordance with claim 1, further comprising the step of:
constructing an output signal from sub-carriers that are each received by any one of the n antenna branches in the selected identified group of n antenna branches.
17. A method in accordance with claim 16, wherein the step of constructing an output signal from sub-carriers comprises the steps of:
computing an approximate power magnitude for each of K sub-carriers for each of the n antenna branches in the selected identified group of n antenna branches; and
comparing the approximate power magnitudes for each of the K sub-carriers for each of the n antenna branches in the selected identified group of n antenna branches with the approximate power magnitudes for each of the respective K sub-carriers for each of the other n antenna branches in the selected identified group of n antenna branches.
18. A method in accordance with claim 17, wherein the step of constructing an output signal from sub-carriers further comprises the step of:
based on results of the comparing step, selecting sub-carriers from one or more of the n antenna branches in the selected identified group of n antenna branches to form the output signal.
19. A method in accordance with claim 18, wherein the step of constructing an output signal from sub-carriers further comprises the step of:
storing results of the comparing step.
20. An apparatus that includes a diversity antenna selection module, wherein the diversity antenna selection module comprises:
a first computation stage configured to compute an approximate bit error probability for each of K sub-carriers for each of L different antenna branches n antenna branches at a time; and
a second computation stage configured to process the approximate bit error probabilities to identify a group of n of the L different antenna branches that minimizes an approximate bit error probability of a signal that will eventually be constructed from sub-carriers that are each received by any one of the n antenna branches in the identified group of n antenna branches.
21. An apparatus in accordance with claim 20, wherein the second computation stage further comprises:
a multiplexer configured to form different groupings of n antenna branches from among the L different antenna branches; and
a minimum function stage configured to select a minimum one of the approximate bit error probabilities for each one of the K sub-carriers for each different grouping of n antenna branches.
22. An apparatus in accordance with claim 21, wherein the second computation stage further comprises:
a summation stage configured to sum the minimum ones of the approximate bit error probabilities that were selected for each one of the K sub-carriers for each different grouping of n antenna branches.
23. An apparatus in accordance with claim 22, wherein the second computation stage further comprises:
a minimum metric selection stage configured to determine which sum of the minimum ones of the approximate bit error probabilities has a smallest value; and
a diversity antenna decision stage configured to select the grouping of n antenna branches that produced the sum of the minimum ones of the approximate bit error probabilities having the smallest value.
24. An apparatus in accordance with claim 20, wherein the second computation stage further comprises:
memories for storing the computed approximate bit error probabilities.
25. An apparatus in accordance with claim 20, wherein the first computation stage further comprises:
n power measurement stages each configured to compute an approximate power magnitude for each of K sub-carriers.
26. An apparatus in accordance with claim 25, wherein the first computation stage further comprises:
n Q-function stages each configured to process approximate power magnitudes.
27. An apparatus in accordance with claim 20, further comprising:
n radio frequency receivers coupled to the diversity antenna selection module.
28. An apparatus in accordance with claim 20, further comprising:
an antenna selection stage configured to allow each of n different radio frequency receivers to be coupled to any one of the L different antenna branches.
29. An apparatus in accordance with claim 20, further comprising:
a diversity antenna structure having L different antenna branches.
30. An apparatus in accordance with claim 20, further comprising:
a sub-carrier selection diversity module configured to construct an output signal from sub-carriers that are each received by any one of the n antenna branches in the identified group of n antenna branches.
31. An apparatus in accordance with claim 30, wherein the sub-carrier selection diversity module comprises:
n power measurement stages each configured to compute an approximate power magnitude for each of K sub-carriers for one of the n antenna branches in the identified group of n antenna branches; and
a comparator configured to compare the approximate power magnitudes for each of the K sub-carriers for each of the n antenna branches in the identified group of n antenna branches with the approximate power magnitudes for each of the respective K sub-carriers for each of the other n antenna branches in the identified group of n antenna branches.
32. An apparatus in accordance with claim 31, wherein the sub-carrier selection diversity module further comprises:
a multiplexer configured to select sub-carriers from one or more of the n antenna branches in the identified group of n antenna branches based on data generated by the comparator to form the output signal.
33. An apparatus in accordance with claim 32, wherein the sub-carrier selection diversity module further comprises:
a memory configured to store the data generated by the comparator.
34. A diversity antenna selection module, comprising:
means for taking measurements from L different antenna branches n antenna branches at a time;
means for using the measurements to identify a group of n of the L different antenna branches that minimizes an approximate bit error probability of a signal that will eventually be constructed from sub-carriers that are each received by any one of the n antenna branches in the identified group of n antenna branches; and
means for selecting the identified group of n antenna branches.
35. A diversity antenna selection module in accordance with claim 34, wherein the measurements comprise power measurements of each of K sub-carriers.
36. A diversity antenna selection module in accordance with claim 35, wherein the means for using the measurements to identify a group of n of the L different antenna branches further comprises:
means for computing an approximate bit error probability for each of the K sub-carriers for each of the L antenna branches n antenna branches at a time.
37. A diversity antenna selection module in accordance with claim 36, wherein the means for using the measurements to identify a group of n of the L different antenna branches further comprises:
means for forming different groupings of n antenna branches from among the L different antenna branches; and
means for selecting a minimum one of the approximate bit error probabilities for each one of the K sub-carriers for each different grouping of n antenna branches.
38. A diversity antenna selection module in accordance with claim 37, wherein the means for using the measurements to identify a group of n of the L different antenna branches further comprises:
means for summing the minimum ones of the approximate bit error probabilities that were selected for each one of the K sub-carriers for each different grouping of n antenna branches.
39. A diversity antenna selection module in accordance with claim 38, wherein the means for using the measurements to identify a group of n of the L different antenna branches further comprises:
means for determining which sum of the minimum ones of the approximate bit error probabilities has a smallest value; and
means for selecting the grouping of n antenna branches that produced the sum of the minimum ones of the approximate bit error probabilities having the smallest value.
40. A diversity antenna selection module in accordance with claim 34, further comprising:
means for calibrating a gain between n radio frequency (RF) receive paths.
41. A diversity antenna selection module in accordance with claim 40, wherein the means for calibrating a gain between n RF receive paths comprises:
means for measuring a signal power received by a first one of the L antenna branches with a first receive path; and
means for measuring the signal power received by the first one of the L antenna branches with a second receive path.
42. A diversity antenna selection module in accordance with claim 34, wherein the means for taking measurements from L different antenna branches n antenna branches at a time comprises:
means for receiving a frame that includes a diversity selection portion comprising one or more antenna branch probing portions; and
means for taking measurements from n antenna branches during one of the antenna branch probing portions.
43. A diversity antenna selection module in accordance with claim 42, wherein the means for taking measurements from n antenna branches during one of the antenna branch probing portions comprises:
n radio frequency receivers with each one being configured to take measurements from one of the n antenna branches during one of the antenna branch probing portions.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A hammer-type, hand-operated striking tool, comprising:
a gripping handle;
a striking head;
an intermediate shaft extending through the handle and supporting the head; and
an intermediate link part,
the handle comprising a tube in which the shaft partially extends, the shaft and the tube being respectively made from first and second rigid materials each presenting a hardness within a first hardness range,
the shaft having a radial area that bears against the tube via the link part, the link part being positioned between the tube and the shaft and being made from a flexible material presenting a second hardness lower than the first hardness range so as to absorb vibrations,
the shaft having a free terminal area that is not covered by the link part, that spans from the link part to a terminal end of the shaft, and that is radially separated from the tube so as to be able to vibrate freely in an internal volume of the tube, and the tool being configured so that an air volume fills the entire space between the free terminal area and the tube.
2. The tool according to claim 1, wherein the first and second rigid materials present a hardness of between 30and 60Rockwell C.
3. The tool according to claim 1, wherein the flexible material presents a hardness of between 60and 80Shore D.
4. The tool according to claim 1, wherein (1) the bearing area of the shaft and the link part and (2) the link part and the tube are in tight contact.
5. The tool according to claim 1, wherein a functional clearance exists between the bearing area of the shaft and the link part at the level of at least a front surface of the tool.
6. The tool according to claim 1, wherein, at the level of at least a front surface of the tool, the link part is slotted or presents a strip of soft material having a hardness of between 0and 50Shore A.
7. The tool according to claim 1, wherein the link part comprises a sheath surrounding the bearing area of the shaft, and a neck designed to be axially inserted between the handle and the shaft.
8. The tool according to claim 1, wherein the handle, link part and shaft are mutually secured by a fixing part extending in the direction of a vibration node of the tool.
9. The tool according to claim 2, wherein:
the first rigid material forming the shaft presents a hardness of between 42and 50Rockwell C; and
the second rigid material forming the shaft presents a hardness of between 38and 42Rockwell C.
10. The tool according to claim 9, wherein the first and second rigid materials are made from metal.
11. The tool according to claim 10, wherein the first and second rigid materials are made from steel.
12. The tool according to claim 3, wherein the flexible material presents a hardness of between 65and 75Shore D.
13. The tool according to claim 12, wherein the flexible material is a plastic material.
14. The tool according to claim 13, wherein the flexible material is polypropylene.
15. The tool according to claim 1, wherein a ratio between (i) the depth of penetration of the shaft into the tube and (ii) the length of the tube is between 0.22and 0.45.
16. A method for manufacturing a hammer-type, hand-operated striking tool, the method comprising: providing the tool comprising:
a gripping handle;
a striking head;
an intermediate shaft extending through the handle and supporting the head; and
an intermediate link part,
the handle comprising a tube in which the shaft partially extends, the shaft and the tube being respectively made from first and second rigid materials each presenting a hardness within a first hardness range,
the shaft having a radial area that bears against the tube via the link part, the link part being positioned between the tube and the shaft and being made from a flexible material presenting a second hardness lower than the first hardness range so as to absorb vibrations,
the shaft having a free terminal area that is not covered by the link part, that spans from the link part to a terminal end of the shaft, and that is radially separated from the tube so as to be able to vibrate freely in an internal volume of the tube, and
the tool being configured so that an air volume fills the entire space between the free terminal area and the tube, and the method comprising the steps of:
mutually securing the head and the shaft;
fitting the link part in place on the shaft in the final position that the link part and the shaft are to take; and
engaging the shaft and the link part inside the tube.
17. The method according to the claim 16, wherein:
the head and the shaft are secured by crimping a barrel of the shaft in a housing of the head, and
a hardening and tempering operation is previously performed on the whole of the shaft with the exception of the barrel.
18. A hammer-type, hand-operated striking tool, comprising:
a gripping handle;
a striking head;
an intermediate shaft extending through the handle and supporting the head; and
an intermediate link part,
the handle comprising a tube in which the shaft partially extends, the shaft and the tube being respectively made from first and second rigid materials each presenting a hardness within a first hardness range,
the shaft having a radial area that bears against the tube via the link part, the link part being positioned between the tube and the shaft and being made from a flexible material presenting a second hardness lower than the first hardness range so as to absorb vibrations,
the shaft having a free terminal area that is not covered by the link part, and that is radially separated from the tube so as to be able to vibrate freely in an internal volume of the tube, and
an air volume filling the entire internal volume of the tube in which the shaft freely vibrates.