Integrated antenna assemblies including multiple antennas for wireless communications devices

Information

  • Patent Grant
  • 6505054
  • Patent Number
    6,505,054
  • Date Filed
    Wednesday, July 7, 1999
    25 years ago
  • Date Issued
    Tuesday, January 7, 2003
    21 years ago
Abstract
A wireless communications device includes an integrated antenna assembly that provides signals associated with multiple functions to the wireless communications device. The integrated antenna assembly includes an integrated antenna housing coupled to a radiotelephone housing and multiple antennas. The integrated antenna housing can include a first antenna that provides GPS signal reception for a GPS receiver and a second antenna that provides communications signals to and from a radiotelephone processor in the radiotelephone housing. The first and second antennas can be mounted on an antenna backing having a first face and a second face. The first and second antennas may be located on the same face of the antenna backing or on opposite faces of the antenna backing. The integrated antenna assembly also can include a third antenna located between the first and second antennas. In this case, the first and second antennas are high-band antennas and the third antenna, located therebetween, is a low-band antenna which can reduce the electromagnetic coupling between the first and second high-band antennas.
Description




FIELD OF THE INVENTION




The present invention relates to the field of communications in general and more particularly to antennas.




BACKGROUND OF THE INVENTION




A wireless communication device, such as a cellular radiotelephone, may include an antenna to enable the wireless communication device to receive and/or transmit signals associated with a wireless service. For example, a GSM type cellular radiotelephone may include an antenna which allows the cellular radiotelephone to function in a GSM system. Such antennas may be adapted for connection to the enclosure of the wireless communications device. However, the physical characteristics of the antenna (such as size) may affect the cost of the wireless communications device.




As wireless services become more popular, there may be a desire to support multiple wireless services using one wireless communications device. For example, it is known to provide Global Positioning System (GPS) functionality along with the radiotelephone functionality described above in a single wireless communication device. Such wireless communications devices are described, for example, in copending U.S. patent application Ser. No. 09/193,587 to Camp, Jr. entitled “Portable Radio Telephones Including Patch Antennas ” and assigned to the assignee of the present application which is incorporated herein by reference. Unfortunately, supporting both GPS and radiotelephone functionalities may further increase the cost of the wireless communications device. Consequently, there is a need to provide wireless communications devices that support both GPS and radiotelephone functionalities while reducing the cost associated with supporting the additional wireless services in the wireless communications device.




SUMMARY OF THE INVENTION




It is, therefore, an object of the present invention to provide improved wireless communications devices.




It is another object of the present invention to further reduce the cost of supporting both GPS and communications functionalities in a wireless communications device.




These and other objects of the present invention are provided by a wireless communications device having an integrated antenna housing that includes a GPS antenna and a first antenna. The GPS antenna provides reception of GPS signals at the wireless communications device which are used to determine a location of the wireless communications device. The first antenna provides reception and transmission of communications signals, such as those used in a PCS or DCS cellular radiotelephone system. Integrating the GPS antenna and the first antenna into the same antenna housing can reduce the cost of manufacturing a wireless communications device that supports multiple functionalities. In addition, as the sizes of wireless communications devices are reduced it may be increasingly difficult to couple multiple antenna housings to a wireless communications device without affecting the functionality and/or aesthetics of the wireless communications device.




In a further aspect of the present invention, the antennas in the integrated antenna assembly are mounted on a common antenna backing in the integrated antenna housing. The antenna backing can include first and second faces, and the GPS antenna and the first antenna can be mounted on a common face of the antenna backing or on opposite faces. The antenna backing may comprise a dielectric material.




In another aspect of the present invention, a second antenna is included in the integrated antenna assembly. Accordingly, the user may operate the wireless communications device in one of multiple communications systems. The second antenna can be mounted between the GPS and first antenna. The first, second, and GPS antennas can each be mounted on any face of the antenna backing.




In an unexpected aspect of the invention, the integrated antenna housing can include a first high-band antenna, a second high-band antenna, and a low-band antenna located therebetween. Locating the low-band antenna between the first high-band antenna and the second high-band antenna may reduce electromagnetic coupling between the first and second high-band antennas in the integrated antenna assembly. For example, if a GPS antenna operates in a frequency range between about 1574 to 1576 MHz and the first antenna operates in a frequency range between about 1710 to 1880 MHz and the second antenna operates in a range between about 880 to 960 MHz, locating the second antenna between the first antenna and the GPS antenna may reduce the electromagnetic coupling between the first antenna and the GPS antenna.




The integrated antenna housing of the present invention can thus reduce the cost of a radiotelephone that provides multiple functions such as cellular communications and GPS functionality. The integrated antenna housing can also reduce the size of a radiotelephone and increase the aesthetic appeal.











BRIEF DESCRIPTION IF THE FIGURES





FIG. 1

is a diagram of a wireless communications device that receives GPS signals and communications signals according to the present invention;





FIG. 2

is a block diagram of a radiotelephone including an integrated antenna assembly according to the present invention;





FIG. 3

is a cross-sectional diagram of an antenna backing according to the present invention taken along section line


3


-


3


′ of

FIGS. 4A and 4B

;





FIGS. 4A and 4B

are diagrams of a first embodiment of an integrated antenna assembly according to the present invention;





FIG. 5A

is a cross-sectional diagram of an antenna backing according to the present invention taken along section line


5


-


5


′ of

FIG. 5B

; and





FIG. 5B

is a diagram of a second embodiment of an integrated antenna assembly according to the present invention.











DETAILED DESCRIPTION OF THE INVENTION




The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.




Embodiments of the present invention are disclosed herein by reference to a wireless communications device including cellular antennas and GPS antennas operating in a cellular communications system and providing GPS functionality. However, it will be understood that the scope of the present invention includes any antennas adapted for use with a wireless communications device and is not limited to cellular antennas or GPS antennas.




As used herein, the phrases “low band antenna” and “high band antenna” include antennas that provide respective low and high frequency communications signals to and from a wireless communications device. Low band antennas allow for the operation of the wireless communications device in frequency ranges which are lower than the frequency ranges in which the high band antennas allow for the operation of the wireless communications device. High band antennas allow for the operation of the wireless communications device in frequency ranges which are higher than the frequency ranges in which the low band antennas allow for the operation of the wireless communications device.





FIG. 1

is a diagram that illustrates a cellular communications system and a Global Positioning System (GPS)


102


which provide communications signals and GPS signals respectively to a wireless communications device


100


. The cellular communications system provides service which enables the wireless communications device


100


to originate and receive calls by transmitting and receiving communications signals to and from a base station


110


coupled to a Public Switched Telephone Network (PSTN)


115


via a Mobile Switching Center


114


. The GPS system


102


provides GPS signals which enable the wireless communications device


100


to determine a location of the wireless communications device. The wireless communications device


100


includes an integrated antenna assembly


111


that provides signal reception for the cellular and GPS signals provided to the wireless communications device


100


.




GPS systems are described, for example, in U.S. Pat. No. 5,884,214 to Krasner entitled GPS Receiver and Method for Processing GPS Signals which is incorporated herein by reference. Cellular communication systems are described, for example, in U.S. Pat. No. 5,867,765 to Nilsson entitled Non-geostationary Satellite Mobile Communication System Integration with Network Principles for Terrestrial Cellular which is incorporated herein by reference.





FIG. 2

is a block diagram of a wireless communications device


100


according to an embodiment of the present invention. As shown in

FIG. 2

, the integrated antenna assembly


111


can include three antennas: a first cellular antenna


215


, a second cellular antenna


210


, and a GPS antenna


205


in an antenna housing


113


, wherein the second cellular antenna


210


is located between the first cellular antenna


215


and the GPS antenna


205


. The first cellular antenna


215


can be a high-band cellular antenna such as, for example, a DCS antenna which operates in a frequency range between about 1710 and 1880 MHz or a PCS antenna which operates in a frequency range between about 1850 and 1990 MHz. The second cellular antenna


210


can be a low-band antenna such as a GSM antenna which operates in a frequency range between about 880 and 960 MHz, or an IS


136


antenna which operates in a frequency range between about 824 and 894 MHz. The GPS antenna


205


can be a high-band antenna operating in a frequency range between about 1574 and 1576 MHz. For example, the wireless communications device


100


may use the second cellular antenna


210


to operate in a GSM or IS


136


system and use the first cellular antenna


215


to operate in a DCS or PCS system and use the GPS antenna


205


to determine its location using a GPS. According to the present invention, locating the low-band second cellular antenna


210


between the high-band first cellular antenna


215


and the high-band GPS


205


antenna may reduce electromagnetic coupling between the high-band first cellular antenna


215


and the high-band GPS antenna


205


.




The integrated antenna assembly


111


is adapted for coupling to the enclosure of the wireless communications device


100


and can be enclosed in a covering layer to improve mechanical robustness of the integrated antenna assembly


111


. In one embodiment, the integrated antenna assembly


111


has an arcuate shape. For example, the integrated antenna assembly


111


may have a parabolic shape such that the base of the integrated antenna assembly


111


coupled to wireless communications device


100


is wider than the tip of the integrated antenna assembly


111


. In one embodiment, the integrated antenna assembly


111


can be covered by a soft overmold material which may reduce the force translated to the case of the wireless communications device


100


such as when it is dropped.




The first and second cellular antennas


215


,


210


provide for the transmission/reception of the first and second communications signals by a cellular telephone transceiver


220


. The cellular telephone transceiver


220


receives signals from and provides signals to a radiotelephone processor


225


. The radiotelephone processor


225


processes the received communications signals to provide data to a user interface


250


and processes data from the user interface


250


to provide the communications signals to be transmitted from the wireless communications device


100


. Radiotelephone communications can thus be provided. It will be understood that the first and second antennas


215


,


210


can be electrically coupled in the integrated antenna assembly


111


as shown in

FIG. 1

or electrically coupled inside the wireless communications device


100


.




The GPS antenna


205


provides for the reception of GPS signals at a GPS receiver


230


. The received GPS signals are provided to a GPS processor


235


which can determine a location of the wireless communications device


100


. The GPS processor


235


can accept data from the user interface


250


, and can provide data to the user interface


250


, such as location data.




The user interface


250


can also include a keypad


240


which can be used to initiate calls in the cellular communications system or interact with the GPS processor


235


. During the call, the user speaks into a microphone


245


which causes the radio telephone processor


225


and cellular telephone transceiver


220


to generate communication signals which are transmitted from the wireless communications device


100


. The user may listen to a speaker


260


that reproduces audio data generated by the radiotelephone processor


225


from communication signals received at the wireless communications device


100


. During operation, the user may refer to a display


255


to determine location information from the GPS processor


235


or other information relevant to the operation of the wireless communications device


100


. The display


255


may also be used in conjunction with the keypad


240


such as when the user dials a number to place a call. The microphone


245


, speaker


260


, keypad


240


, and display


255


are coupled to the radiotelephone processor


225


processor that controls operations of the wireless communications device


100


.





FIG. 3

is a cross-sectional diagram of the integrated antenna assembly


111


according to the present invention taken along section line


3


-


3


′ of

FIGS. 4A and 4B

. According to

FIG. 3

, the integrated antenna assembly


111


includes an antenna backing


305


upon which the GPS antenna


205


and the first and second cellular antennas


215


,


210


are mounted in the antenna housing


113


. The antenna backing


305


has a first face


310


and a second face


315


.




In a preferred embodiment of the present invention, the antenna backing


305


comprises a planar dielectric material. The GPS antenna


205


and the first and second cellular antennas


215


,


210


can comprise planar conductors formed on the dielectric material such as conductive etch on a printed circuit board. In another embodiment, the antenna backing


305


can have a curved surface such as when it is desired to conform the antenna backing


305


to a non-planar shape. For example, the antenna backing


305


may comprise a flexible dielectric circuit board having the GPS antenna


205


and the first and second cellular antennas


215


,


210


formed thereon and curved to conform to a cylindrical shape.




In a first embodiment of the present invention, the GPS antenna


205


′ and the first and second cellular antennas


215


′,


210


′ are located on opposite faces of the antenna backing


305


as shown in

FIGS. 4A and 4B

, respectively. As shown in

FIG. 4A

, the GPS antenna


205


′ is located on the first face


310


of the antenna backing


305


, and the first and second cellular antennas


215


′,


210


′ are located on the second face


315


of the antenna backing


305


as shown in FIG.


4


B.




In an alternate embodiment of the present invention, the GPS antenna


205


″ and the first and second cellular antennas


215


″,


210


″ are located on the same face of the antenna backing


305


as shown in

FIGS. 5A and 5B

.

FIG. 5A

is a cross-sectional diagram of an antenna backing according to the present invention taken along section line


5


-


5


′ of FIG.


5


B. As shown in

FIG. 5B

, The GPS antenna


205


″ may be located on the first face


310


near a first edge


320


of the antenna backing


305


and the first cellular antenna


215


″ may be located on the first face


310


near a second edge


325


of the antenna backing


305


. The second cellular antenna


210


″ is located on the first face


310


of the antenna backing


305


between the GPS antenna


205


″ and the first cellular antenna


215


″. It will be understood that the first cellular antenna


215


″, the second cellular antenna


210


″, and the GPS antenna


205


″ can each be located on either the first face


310


or the second face


315


of the antenna backing.




Locating the second cellular antenna


210


between the GPS antenna


205


and the first cellular antenna


215


may reduce the electromagnetic coupling between the GPS antenna


205


and the first cellular antenna


215


. It will be understood that the first cellular antenna


215


, the second cellular antenna


210


, and the GPS antenna


205


may be mounted on the antenna backing


305


.




According to the present invention, the GPS antenna


205


and the first and second cellular antennas


215


,


210


are included in the integrated antenna assembly


111


, thereby reducing the need for a GPS antenna in a second housing connected to the wireless communications device. Consequently, the cost of providing multiple functionalities, such as cellular communications functionality and GPS functionality, in the wireless communications device


100


may be reduced by eliminating additional parts that would otherwise be needed to provide a separate GPS antenna.




In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.



Claims
  • 1. A wireless communications device comprising:a radiotelephone housing; a GPS receiver in the radiotelephone housing, wherein the GPS receiver generates GPS location information; a radiotelephone transceiver in the radiotelephone housing wherein the radiotelephone transceiver provides radiotelephone communications; and an integrated antenna assembly comprising, an integrated antenna housing coupled to and mounted on the radiotelephone housing, a first antenna in the integrated antenna housing and coupled to the GPS receiver wherein the first antenna provides GPS signal reception for the GPS receiver; a second antenna in the integrated antenna housing and coupled to the radiotelephone transceiver wherein the second antenna provides transmission and reception of communications signals for the radiotelephone transceiver, wherein the wireless communications device further comprises a third antenna in the integrated antenna housing, wherein the third antenna provides transmission and reception of second communications signals for the wireless communications device.
  • 2. The antenna assembly of claim 1, wherein the third antenna comprises a low-band antenna.
  • 3. A wireless communications device comprising:a radiotelephone housing; a GPS receiver in the radiotelephone housing, wherein the GPS receiver generates GPS location information; a radiotelephone transceiver in the radiotelephone housing wherein the radiotelephone transceiver provides radiotelephone communications; and an integrated antenna assembly comprising, an integrated antenna housing coupled to and mounted on the radiotelephone housing, a first antenna in the integrated antenna housing and coupled to the GPS receiver wherein the first antenna provides GPS signal reception for the GPS receiver; a second antenna in the integrated antenna housing and coupled to the radiotelephone transceiver wherein the second antenna provides transmission and reception of communications signals for the radiotelephone transceiver, wherein the wireless communications device further comprises an antenna backing in the integrated antenna housing, wherein the first and second antennas are located on the antenna backing.
  • 4. The antenna assembly of claim 3, wherein the antenna backing includes first and second faces, wherein the first antenna is on the first face of the antenna backing and the second antenna is on the second face of the antenna backing.
  • 5. The antenna assembly of claim 3, wherein the antenna backing includes a face, wherein the first and second antennas are on the face the antenna backing.
  • 6. The antenna assembly of claim 3 further comprising:a third antenna on the antenna backing between the first and second antennas.
  • 7. The antenna assembly of claim 3, wherein the antenna backing comprises a dielectric material.
  • 8. A wireless communications device comprising:a radiotelephone housing; a GPS receiver in the radiotelephone housing, wherein the GPS receiver generates GPS location information; a radiotelephone transceiver in the radiotelephone housing wherein the radiotelephone transceiver provides radiotelephone communications; and an integrated antenna assembly comprising, an integrated antenna housing coupled to and mounted on the radiotelephone housing, a first antenna in the integrated antenna housing and coupled to the GPS receiver wherein the first antenna provides GPS signal reception for the GPS receiver, and a second antenna in the integrated antenna housing and coupled to the radiotelephone transceiver wherein the second antenna provides transmission and reception of communications signals for the radiotelephone transceiver wherein the integrated antenna housing comprises a flat blade shape.
  • 9. An integrated antenna assembly for a wireless communications device, the antenna assembly comprising:an integrated antenna backing adapted to couple to and mount on the wireless communications device; a first antenna on the integrated antenna backing, wherein the first antenna provides Global Positioning System signals for the wireless communications device; and a second antenna on the integrated antenna backing, wherein the second antenna provides transmission and reception of first communications signals for the wireless communications device.
  • 10. The antenna assembly of claim 9 further comprising:a third antenna on the antenna backing, wherein the third antenna provides second communications signals to and from the wireless communications device.
  • 11. The antenna assembly of claim 10, wherein the antenna backing includes a first face and a second face; and wherein the third antenna is on the first face of the antenna backing between the second and first antennas.
  • 12. The antenna assembly of claim 10, wherein the antenna backing includes a first face and a second face, wherein the first antenna is on the first face of the antenna backing and the second and third antennas are on the second face of the antenna backing.
  • 13. The antenna assembly of claim 9, wherein the second antenna comprises an antenna chosen from the group consisting of a high-band antenna and a low-band antenna.
  • 14. The antenna assembly of claim 10, wherein the third antenna comprises a low-band antenna.
  • 15. The antenna assembly of claim 10, wherein the antenna backing comprises a dielectric material.
  • 16. The antenna assembly of claim 9, wherein the second antenna comprises a quarter-wavelength monopole antenna.
  • 17. The antenna assembly of claim 9, wherein the second antenna comprises a planar conductor on the antenna backing.
  • 18. The antenna assembly of claim 9, wherein the antenna backing comprises a dielectric layer.
  • 19. The antenna assembly of claim 10, wherein the third antenna comprises a quarter-wavelength monopole antenna.
  • 20. The antenna assembly of claim 10, wherein the third antenna comprises a planar connector on the antenna backing.
  • 21. The antenna assembly of claim 9, wherein the first antenna comprises a quarter-wavelength monopole antenna.
  • 22. The antenna assembly of claim 9, wherein the first antenna comprises a planar conductor on the antenna backing.
  • 23. The antenna assembly of claim 9, wherein the first and second antennas on the antenna backing are in a single integrated antenna housing connected to the wireless communications device.
  • 24. The antenna assembly of claim 9, wherein the antenna backing includes a curved surface.
  • 25. An integrated antenna assembly for a wireless communications device, the antenna assembly comprising:an integrated antenna housing adapted to couple to and mount on the wireless communications device; a first antenna in the integrated antenna housing, wherein the first antenna provides Global Positioning System signals for the wireless communications device; and a second antenna in the integrated antenna housing, wherein the second antenna provides transmission and reception of first communications signals for the wireless communications device, wherein the wireless communications device further comprises an antenna backing in the antenna housing, wherein the first and second antennas are located on the antenna backing.
  • 26. An integrated antenna assembly for a wireless communications device, the antenna assembly comprising:an integrated antenna housing adapted to couple to and mount on the wireless communications device; a first antenna in the integrated antenna housing, wherein the first antenna provides Global Positioning System signals for the wireless communications device; and a second antenna in the integrated antenna housing, wherein the second antenna provides transmission and reception of first communications signals for the wireless communications device, wherein the wireless communications device further comprises a third antenna in the integrated antenna housing, wherein the third antenna provides transmission and reception of second communications signals for the wireless communications device.
  • 27. The antenna assembly of claim 25, wherein the antenna backing includes a face, wherein the first and second antennas are on the face the antenna backing.
  • 28. The antenna assembly of claim 27 further comprising:a third antenna on the face of the antenna backing between the first and second antennas.
  • 29. The antenna assembly of claim 25, wherein the antenna backing includes first and second faces, wherein the first antenna is on the first face of the antenna backing and the second antenna is on the second face of the antenna backing.
  • 30. A wireless communications device comprising:a radiotelephone housing; a GPS receiver in the radiotelephone housing, wherein the GPS receiver generates GPS location information; a radiotelephone transceiver in the radiotelephone housing wherein the radiotelephone transceiver provides radiotelephone communications; and an antenna backing configured to mount to the radiotelephone housing comprising, a first antenna on the antenna backing and coupled to the GPS receiver wherein the first antenna provides GPS signal reception for the GPS receiver, and a second antenna on the antenna backing and coupled to the radiotelephone transceiver wherein the second antenna provides transmission and reception of communications signals for the radiotelephone transceiver.
  • 31. The antenna backing of claim 30, wherein the antenna backing includes first and second faces, wherein the first antenna is on the first face of the antenna backing and the second antenna is on the second face of the antenna backing.
  • 32. The antenna backing of claim 30, wherein the second antenna comprises an antenna chosen from the group consisting of a high-band antenna and a low-band antenna.
  • 33. The antenna backing of claim 30 wherein the first communications signals comprise radiotelephone communications signals.
  • 34. The antenna backing of claim 30 further comprising:a third antenna on the antenna backing, wherein the third antenna provides transmission and reception of second communications signals for the wireless communications device.
  • 35. The antenna backing of claim 34, wherein the third antenna comprises a low-band antenna.
  • 36. The antenna backing of claim 35, wherein the antenna backing comprises a dielectric material.
  • 37. The antenna backing of claim 30, wherein the antenna backing includes a face, wherein the first and second antennas are on the face the antenna backing.
  • 38. The antenna backing of claim 37 further comprising:a third antenna on the face of the antenna backing between the first and second antennas.
  • 39. A wireless communications device comprising:a radiotelephone housing; a radiotelephone processor in the radiotelephone housing wherein the radiotelephone processor provides radiotelephone communications; and an integrated antenna assembly comprising, an integrated antenna housing coupled to and mounted on the radiotelephone housing, a first antenna in the integrated antenna housing and coupled to the radiotelephone processor, wherein the first antenna provides transmission and reception of first high-band communications signals for the radiotelephone processor, a second antenna in the integrated antenna housing and coupled to the radiotelephone processor, wherein the second antenna provides transmission and reception of second high-band communications signals for the radiotelephone processor, and a third antenna located between the first and second antennas in the integrated antenna housing, wherein the third antenna provides transmission and reception of low-band communications signals for the radiotelephone processor.
  • 40. The wireless communications device of claim 39, wherein the first and second high band communications signals are in a range between about 1574 MHz and 1990 MHz and wherein the low-band communications signals are in a range between about 824 and 960 MHz.
  • 41. The wireless communications device of claim 39 further comprising an antenna backing in the integrated antenna housing, wherein the first, second and third antennas are on the antenna backing.
  • 42. The wireless communications device of claim 41, wherein the antenna backing includes opposing first and second faces, wherein the first, second, and third antennas are mounted on either face of the antenna backing.
  • 43. The wireless communications device of claim 39, wherein the first antenna comprises a quarter-wavelength monopole antenna.
  • 44. The wireless communications device of claim 39, wherein the first antenna comprises a planar conductor on the antenna backing.
  • 45. The wireless communications device of claim 39, wherein the second antenna comprises a quarter-wavelength monopole antenna.
  • 46. The wireless communications device of claim 39, wherein the second antenna comprises a planar conductor on the antenna backing.
  • 47. The wireless communications device of claim 39, wherein the third antenna comprises a quarter-wavelength monopole antenna.
  • 48. The wireless communications device of claim 39, wherein the third antenna comprises a planar conductor on the antenna backing.
  • 49. The wireless communications device of claim 39, wherein the first antenna comprises a GPS antenna that provides GPS signal reception.
  • 50. The wireless communications device of claim 39, wherein the second antenna comprises a first cellular antenna.
  • 51. The wireless communications device of claim 39, wherein the third antenna comprises a second cellular antenna.
  • 52. The wireless communications device of claim 39 wherein the integrated antenna housing is rigidly mounted on the radiotelephone housing.
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5977928 Ying et al. Nov 1999 A
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Entry
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