Polarization diversity antenna system for cellular telephone

• US 6,326,924 B1
• Filed: 05/19/1999
• Issued: 12/04/2001
• Est. Priority Date: 05/19/1998
• Status: Expired due to Term

• Current Assignee: Kokusai Electric Co., Ltd., Conexant Systems Incorporated (Synaptics Incorporated)
• Original Assignee: Kokusai Electric Co., Ltd.
• Inventors: Onishi, Naoki, Sasaki, Kanemi, Muramoto, Mitsuru, Saito, Hirotaka
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): NGUYEN, HOANG V
• Application Number:
  US09/314,890
• Time in Patent Office: 930 Days
• Field of Search: 343/702, 343/700.MS, 343/725, 343/727, 343/728, 343/729, 343/730
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/242 specially adapted for hand-held use
• CPC Class Codes: H01Q 1/243 with built-in antennas
• 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: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00

Abstract

Radio communication systems, e.g. cellular telephones, have employed a space diversity antenna system which includes a plurality of antennas. In the space diversity antenna system for use in the cellular telephone, since two antennas are positioned adjoining each other, the space diversity effect cannot be adequately provided. To solve this problem, the polarization diversity antenna system according to this invention incorporates a first antenna, a second antenna, and a conductive board on which the second antenna is fixed at a given position, thus preventing the current flowing in the conductive board from causing the reception characteristic of the second antenna to deteriorate.

Claims

1. A polarization diversity antenna system comprising:

a first antenna configured to receive a first polarized wave;

a second antenna including a centerline and being configured to receive a second polarized wave, the second polarized wave being perpendicular to the first polarized wave; and

a conductive circuit board on which the second antenna is provided, the conductive circuit board producing (i) a number of current portions when one of the first and second polarized waves is received, and (ii) including a centerline, the second antenna centerline being perpendicular to a lengthwise dimension of the conductive circuit board;

wherein the second antenna centerline is positioned proximate the conductive circuit board centerline and is generally longitudinally aligned therewith.

2. A polarization diversity antenna system as set forth in claim 1, wherein:

the conductive circuit board is rectangular, and

the second antenna is provided symmetrically with respect to a center of the conductive circuit board in a longitudinal direction of the conductive circuit board.

3. A polarization diversity antenna system as set forth in claim 1,

wherein the first antenna is provided on the conductive circuit board symmetrically with respect to a centerline.

4. A polarization diversity antenna system as set forth in claim 1, wherein the second antenna has a built-in antenna.

5. A polarization diversity antenna system as set forth in claim 1, wherein the second antenna has an inverted F antenna.

6. A polarization diversity antenna system as set forth in claim 1, wherein the second antenna has an inverse L antenna.

7. A polarization diversity antenna system as set forth in claim 1, wherein the second antenna has a loop antenna.

8. A polarization diversity antenna system as set forth in claim 1, wherein:

the conductive circuit board is rectangular, and

the second antenna has a first antenna element and a second antenna element, the first antenna element and the second antenna element being provided on the conductive board symmetrically with respect to a center of the conductive circuit board in a longitudinal direction of the conductive circuit board.

9. A polarization diversity antenna system as set forth in claim 8, wherein the first and second antenna elements have substantially the same shape.

10. A polarization diversity antenna system as set forth in claim 8, wherein the second antenna has a built-in antenna.

11. A polarization diversity antenna system as set forth in claim 8, wherein the second antenna has an inverted F antenna.

12. A polarization diversity antenna system as set forth in claim 8, wherein the second antenna has an inverse L antenna.

13. A polarization diversity antenna system as set forth in claim 8, wherein the second antenna has an M-shaped antenna.

14. A polarization diversity antenna system as set forth in claim 8, wherein the second antenna has a loop antenna.

15. A polarization diversity antenna system as set forth in claim 1, wherein said second antenna centerline is positioned within 15% of the lengthwise dimension of said conductive circuit board relative to said circuit board centerline.

16. A polarization diversity antenna system for use in a portable telephone, the antenna system comprising:

a whip antenna configured to receive vertically polarized waves;

a built-in antenna configured to receive horizontally polarized waves, the built-in antenna including a centerline, the built-in antenna centerline being parallel to a lengthwise dimension of the built-in antenna; and

a rectangular conductive circuit board on which the built-in antenna is mounted, the circuit board (i) producing a number of current portions when one of the vertically and horizontally polarized waves is received, and (ii) including a centerline, the circuit board centerline being perpendicular to a lengthwise dimension of the circuit board;

wherein the built-in antenna centerline is positioned proximate the circuit board centerline and is generally longitudinally aligned therewith.

17. A polarization diversity antenna system as set forth in claim 16, wherein said built-in antenna centerline is positioned within 15% of the lengthwise dimension of said circuit board relative to said circuit board centerline.

18. A portable telephone comprising:

a whip antenna configured to receive vertically polarized waves;

a built-in antenna configured to receive horizontally polarized waves, the built-in antenna including a centerline, the built-in antenna centerline being parallel to a lengthwise dimension of the built-in antenna;

a rectangular conductive circuit board on which the built-in antenna is mounted, the circuit board (i) producing a number of current portions when one of the vertically and horizontally polarized waves is received, and (ii) including a centerline, the circuit board centerline being perpendicular to a lengthwise dimension of the circuit board;

a switch circuit disposed on the board configured (i) to receive the vertically polarized waves and the horizontally polarized waves and (ii) to selectively output one of the vertically polarized waves and the horizontally polarized waves; and

a receiver operatively arranged with the switch circuit and configured to receive the output therefrom;

wherein the built-in antenna centerline is positioned proximate the circuit board centerline and is generally longitudinally aligned therewith.

19. A polarization diversity antenna system as set forth in claim 18, wherein said built-in antenna centerline is positioned within 15% of the lengthwise dimension of said circuit board relative to said circuit board centerline.