Antenna coupling device

• US 6,611,235 B2
• Filed: 03/04/2002
• Issued: 08/26/2003
• Est. Priority Date: 03/07/2001
• Status: Expired due to Fees

• Current Assignee: Smartag Wireless AB
• Original Assignee: Smarteq Wireless AB (Amphenol Corporation)
• Inventors: Lindberg, Peter, Barna, Zsolt
• Primary Examiner(s): NGUYEN, HOANG V
• Application Number:
  US10/086,416
• Publication Number:
  US 20020154066A1
• Time in Patent Office: 540 Days
• Field of Search: 343/702, 343/905, 343/906, 343/846, 343/848, 343/711, 343/713, 343/841
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 5/371 Branching current paths
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40

Abstract

The present invention relates to an antenna coupling device (14) for coupling radio frequency signal from a communication device (10) having an internal first antenna, the communication device (10) operable in n frequency bands, where n>1 and n is an integer. The antenna coupling device (14) comprises a port (16) connected/connectable to a transmission line (18). A conducting surface of said antenna coupling device (14) has a geometric shape in the form of a tree structure (20) connected to said port (16). The tree structure (20) comprises a number, m, of branches, where m≧n, wherein said tree structure (20) comprises at least one branch b_ix for each frequency band I of said communication device (10), wherein I is an integer and 1≦I≦n, and x is an integer and 1≦x≦k (i), and the total number, m, of branches satisfy the following expression $\sum _{i=1}^nk\left(i\right)=m$

wherein k (i) is a function of I, which only can obtain an integer value and is the total number of branches for frequency band.

Claims

1. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna, the communication device (10) operable in n frequency bands, where n>

1 and n is an integer, wherein said antenna coupling device (14) comprises a port (16) connected/connectable to a transmission line (18), characterized in that a conducting surface of said antenna coupling device (14) has a geometric shape in the form of a tree structure (20) connected to said port (16), wherein said tree structure (20) comprises a number, m, of branches, where m≧

n, wherein said tree structure (20) comprises at least one branch b_ix for each frequency band i of said communication device (10), wherein i is an integer and 1≦

i≦

n, and x is an integer and 1≦

x≦

k(i), and the total number, m, of branches satisfy the following expression $\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>k<br><br>\left(i\right)=m$

wherein k(i) is a function of i, which only can obtain an integer value and is the total number of branches for a frequency band i.

2. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that at least one branch b_ix for each frequency band i fulfils the condition;

a length of said branch b_ix, as measured form said port (16) to a free end of said branch b_ix is not less than about ⅛

of λ

_i, where λ

_i is the wavelength in the medium at the frequency band i.

3. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that said at least one branch b_ix for said frequency band i of said communication device (10) is/are placed, when said antenna coupling device (14) is in operation, above a domain D_i of said internal first antenna, wherein a current causing electromagnetic fields in said at least one branch b_ix is intended to pick up a considerable part of an electromagnetic wave in said frequency band i.

4. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 3, characterized in that said domains D_i are at least in part disjoint.

5. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that each branch b_ix has a constant width.

6. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 5, characterized in that the widths of at least two branches b_ix are equal.

7. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that at least one of said branches b_ix has a variable width along said branch b_ix .

8. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that at least one of said branches b_ix has a part in the form of a meander line 1≦

x≦

k(i), and the total number, m, of branches satisfy the following expression $\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>k<br><br>\left(i\right)=m$

wherein k(i) is a function of i, which only can obtain an integer value (28).

9. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that different branches b_ix can intersect each other.

10. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that further branches can be used to improve matching of impedance to a characteristic impedance of said transmission line (18).

11. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that said antenna coupling device has an open ground plane (24).

12. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that said antenna coupling device (14) has a closed ground plane (30).

13. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that said tree structure (20) of said antenna coupling device (14) is placed on a printed circuit board.

14. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that said tree structure of said antenna coupling device (14) is in the form of plating.

15. An antenna coupling device (14) for coupling radio frequency signals from a communication device (10) having an internal first antenna according to claim 1, characterized in that said tree structure (20) of said antenna coupling device (14) is in the form of conducting ink.