Wave transmission lines and networks – Plural channel systems – Having branched circuits
Patent
1988-06-06
1990-12-25
Lee, Benny T.
Wave transmission lines and networks
Plural channel systems
Having branched circuits
333132, 333134, 333207, 455 78, 455 82, 455 83, 370 38, 370 32, H03H 746, H01P 1213, H04B 148
Patent
active
049806602
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
TECHNICAL FIELD
The present invention relates to an antenna sharing apparatus for use in a communication system, for example, an automobile telephone or the like in which the transmitting frequency and receiving frequency are different and which uses an antenna in common with the transmission and the reception.
BACKGROUND ART
As shown in FIG. 1, a conventional antenna sharing apparatus comprises a combination of two band pass filters. That is, a transmitting filter 3 for passing a transmission band is provided between a transmitting terminal 1 and an antenna terminal 2. A receiving filter 5 or passing a reception band is provided between a receiving terminal 4 and the antenna terminal 2. FIG. 2 shows transmitting characteristics of the conventional antenna sharing apparatus. A transmission band 6 and a reception band 7 are provided. The isolation in the reception band 7 of the transmission band 6 is indicated by a point 8. The isolation in the transmission band 6 of the reception band 7 is indicated by a point 9.
In the conventional antenna sharing apparatus, in the case where the transmission band 6 and reception band 7 are wide or where the transmission band 6 and reception band 7 are close to each other, it is difficult to set the transmission and reception isolation with large isolation points 8 and 9. And, when the transmission and reception bands are adjacent to each other, transmission and reception isolations cannot be obtained.
SUMMARY OF THE INVENTION
According to the invention, an antenna sharing apparatus comprises a combination of two or more filters and is constituted such that the pass bands of the filters are switched by switching means. Therefore, each of the transmission and reception bands of the antenna sharing apparatus are divided into halves and the transmission side low band, transmission side high band, reception side low band, and reception side high band are switched by the switching means, so that the transmission and reception band widths can be narrowed. An antenna sharing apparatus which can easily obtain large-transmission/reception-isolation points is thereby provided.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a conventional antenna sharing apparatus, FIG. 2 is a transmission characteristic diagram of the conventional antenna sharing apparatus, FIG. 3 is a block diagram of an antenna sharing apparatus in an embodiment of the present invention, FIGS. 4a and 4b are transmission characteristic diagrams of the antenna sharing apparatus of FIG. 3, FIG. 5 is an electric circuit diagram showing a practical example of the antenna sharing apparatus of FIG. 3, FIG. 6 is an exploded perspective view showing a practical filter structure, FIG. 7 is a perspective view showing a dielectric coaxial resonator used in the antenna sharing apparatus of the invention, FIG. 8 is an equivalent circuit diagram of the dielectric coaxial resonator, FIG. 9 is a circuit diagram showing an embodiment of a circuit using a varactor diode as a filter for use in the antenna sharing apparatus, and FIG. 10 is a circuit diagram of an embodiment of the circuit using a PIN diode as a filter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A block diagram of an antenna sharing apparatus in an embodiment of the present invention is shown in FIG. 3. A transmitting terminal 11 is connected to a transmission side low pass filter 14 and to a transmission side high pass filter 15 through a transmission side switch 18. The other terminals of the filters 14 and 15 are connected to an antenna side switch 19. Similarly, a receiving terminal 12 is connected to a reception side low pass filter 16 and to a reception side high pass filter 17 through a reception side switch 20. The other terminals of the filters 16 and 17 are connected to the antenna side switch 19. The antenna side switch 19 is connected to an antenna 13. In such an arrangement, the high band and low band filters 14, 15, 16, and 17 for transmission and reception are switched by the switches 18,
REFERENCES:
patent: 3293644 (1966-12-01), Loss et al.
patent: 4087751 (1978-05-01), Kato et al.
patent: 4349799 (1982-09-01), Blocksome et al.
patent: 4502029 (1985-02-01), Reed
"Patent Abstracts of Japan," vol. 9, No. 165, (E-327) [1888], Jul. 10, 1985.
Communication News, vol. 12, No. 12, Dec. 1951; D. J. Braak: "Mobile Radio Equipment, Type SRR 178," pp. 57-67.
Miyake Hideyuki
Nagata Takashi
Nakamura Toshiaki
Takimoto Nobuhiro
Lee Benny T.
Matsushita Electric - Industrial Co., Ltd.
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