1. Field of the Invention
The present invention relates to antenna duplexers mounted on portable telephones, etc.
2. Description of Related Art
As shown in
Furthermore interposed between the branchpoint 10 and the receiving filter 41 is a phase-matching strip line 7 for phase rotation, to match the phases between the transmitting filter 51 and the receiving filter 41 (JP-A-307383/2000). Incidentally the phase-matching strip line 7 is interposed between the branchpoint 10 and the filter having a higher pass band of the transmitting filter 51 and the receiving filter 41.
With the antenna duplexer, when a signal is to be transmitted, the signal received by the transmitting signal terminal Tx passes through the transmitting filter 51 and thereafter is fed from the antenna terminal ANT to an antenna. In this case there occurs a phenomenon that the signal received by the transmitting signal terminal Tx sneaks around to the receiving signal terminal Rx, so that there is a need to take sufficient isolation measures against the phenomenon.
Accordingly with the conventional antenna duplexer, various isolation measures are heretofore taken to a signal path from the transmitting signal terminal Tx to the receiving signal terminal Rx via the transmitting filter 51 and the receiving filter 41. However, the conventional antenna duplexer has not yet achieved the sufficient isolation effect, and therefore there is still room for more improvement.
An object of the present invention is to provide an antenna duplexer for achieving a further higher isolation effect than conventionally.
We have conducted intensive research and found the cause of failing to achieve sufficient isolation effect with the conventional antenna duplexer. Based on the result we have succeeded in developing an antenna duplexer for achieving a further higher isolation effect than conventionally.
With the conventional antenna duplexer, as shown in
An antenna duplexer embodying the present invention comprises a package 83 having a plurality of ceramic layers 81 superposed, and a transmitting filter 51 and a receiving filter 41 which are mounted on a surface of the package 83. A phase-matching strip line 7 is formed on a surface of at least one ceramic layer 81 providing the package 83.
Further, grounding layers 61, 71 are formed respectively on surfaces of upper and lower ceramic layers 81, 81 of the package 83 with the aforementioned phase-matching strip line 7 interposed therebetween. A plurality of conductor lines are formed around the phase-matching strip line 7 for connecting the two grounding layers 61, 71 to each other.
With the antenna duplexer embodying the present invention, a plurality of conductor lines are formed around the phase-matching strip line 7, and opposite ends of each of the conductor lines are respectively connected to the upper and the lower grounding layers 61, 71. This provides a shield around the phase-matching strip line 7, blocking a signal sneak path from the transmitting signal terminal Tx to the receiving signal terminal Rx via the phase-matching strip line 7, thus achieving a higher isolation effect.
Stated more specifically, the plurality of conductor lines comprise via holes 4 each provided by forming conductor film on an inner peripheral surface of a hole vertically extending through the ceramic layers 81 between the two grounding layers 61, 71, or by filling the hole with conductor. Further, formed on side surfaces of the package 83 are a plurality of castellations 84 including an antenna terminal ANT, transmitting signal terminal Tx and receiving signal terminal Rx. The conductor lines are interposed between the transmitting signal terminal Tx and the phase-matching strip line 7, and/or between the receiving signal terminal Rx and the phase-matching strip line 7.
According to the specific construction, a shield is provided between the transmitting signal terminal Tx and the phase-matching strip line 7, or a shield is provided between the receiving signal terminal Rx and the phase-matching strip line 7, thus blocking a signal transmission path from the transmitting signal terminal Tx to the receiving signal terminal Rx via the phase-matching strip line 7, improving the isolation characteristics.
Stated more specifically, the plurality of conductor lines are arranged so as to surround entirely an area in which the phase-matching strip line 7 is formed. This provides the shield all around the phase-matching strip line 7, whereby unnecessary signals from the outside can be interrupted.
As described above, the antenna duplexer of the present invention can achieve a higher isolation effect than conventionally.
a) and
An embodiment of the present invention will be described below with reference to the drawings. An antenna duplexer embodying the present invention, as shown in
As shown in
As shown in
As shown in
The castellation 84 can be formed, as shown in
As discussed above, with the antenna duplexer 8 of the present invention, the plurality of via holes 4 are arranged so as to surround the phase-matching strip line 7, whereby the higher isolation effect can be achieved. Furthermore, the upper and the lower grounding layers 61, 71 are connected to each other by the castellations 84 and by the plurality of via holes 4, to thereby strengthen the grounding.
The device of the invention is not limited to the foregoing embodiment in construction but can be modified variously by one skilled in the art without departing from the spirit of the invention as set forth in the appended claims. For example, the via holes 4 are not limitedly arranged so as to surround entirely the phase-matching strip line 7, as shown in
Number | Date | Country | Kind |
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2003-397971 | Nov 2003 | JP | national |
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6351194 | Takahashi et al. | Feb 2002 | B2 |
6781479 | Ikada et al. | Aug 2004 | B2 |
6919778 | Iwamoto et al. | Jul 2005 | B2 |
20020109561 | Iwamoto et al. | Aug 2002 | A1 |
20050206477 | Cheema et al. | Sep 2005 | A1 |
Number | Date | Country |
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6-97761 | Apr 1994 | JP |
11-340781 | Dec 1999 | JP |
2000-307383 | Nov 2000 | JP |
2003-298462 | Oct 2003 | JP |
Number | Date | Country | |
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20050116790 A1 | Jun 2005 | US |