Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1997-10-28
2001-10-30
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S895000, C343S901000
Reexamination Certificate
active
06310578
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to antenna design for portable communication devices. More particularly, the present invention relates to a multiple band telescoping antenna.
BACKGROUND OF THE INVENTION
Many different digital systems, such as GSM, DCS, PCS, D-AMPS, are used for cellular networks, frequently within the same service area. These systems typically operate in different frequency ranges—for example, the GSM system operates at 890-960 MHZ, and the DCS system operates at 1710-1880 MHZ. In service areas where multiple frequency ranges are used, a dual mode mobile telephone or mobile data terminal which can operate in different systems is desirable. Dual mode phones have been developed which require dual band miniature antennas.
Some efforts on the dual band antennas design has been done. The Japanese patent (6-37531) discloses a helix which contains an inner parasitic metal rod. In this antenna, the antenna can be tuned to dual resonant frequencies by adjusting the position of the metal rod. Unfortunately, the band width for this design is too narrow for use in cellular communications. Dual band printed monopole antennas are known in which dual resonance is achieved by the addition of a parasitic strip in close proximity to a printed monopole antenna. While such an antenna has enough bandwidth for cellular communication, it requires the addition of a parasitic strip. Moteco AB in Sweden has designed a coil matching dual band whip antenna and coil antenna, in which dual resonance is achieve by adjusting the coil matching component (¼&lgr; for 900 MHZ and ½&lgr; for 1800 MHZ). While this antenna has relatively good band width and radiation performances, its length is only about 40 mm. A non uniform helical dual band antenna which is relatively small in size is disclosed in Applicant's copending, commonly assigned application entitled “Multiple Band Non-Uniform Helical Antennas”, Ser. No. 08/725,507, now U.S. Pat. No. 6,112,102, the entirety of which is incorporated by reference.
It is known that an extended whip antenna has a higher efficiency when the phone is relatively close to a human head. Typical dual band extendable whip antennas, such as those mentioned above, require a complicated matching network to match the whip antenna impedance to the two bands within 50 ohms. A dual band retractable antenna is disclosed in Applicant's copending, commonly assigned application entitled “Retractable Multi-Band Antennas”, Ser. No. 08/725,504,now U.S. Pat. No. 5,963,871 the entirety of which is incorporated by reference. Such an antenna requires two ports, one for a helical antenna and another for a whip antenna. A means for switching between the ports for the different modes is required.
SUMMARY OF THE INVENTION
It would be desirable for a multiple band antenna to avoid complexities such as switching between ports, additional parasitic strips, and complicated impedance matching networks while having a bandwidth suitable for cellular communications. It would also be desirable for such an antenna to achieve high-quality communication performance while being compact in size so as to require relatively little storage space within a hand-held portable communication device.
The present invention overcomes the above-mentioned problems, and achieves other advantages, by providing for an extendable dual band antenna which has a single port for both extended and retracted whip positions. The single port is made possible by using an electromagnetic coupling technique in which metal-to-metal contact between the extendable whip antenna and the base antenna is avoided. A branch antenna or a non uniform helical antenna can be used as a base antenna. The telescoping whip antenna operates as a passive antenna when the whip is in an extended position, while a fixed base antenna operates as an active antenna. The total length of the whip is selected to optimize the radiation efficiency for multiple bands (i.e., for the GSM and DCS bands). When the phone is used close to a user's head, the extended whip can decrease body loss, thereby increasing radiation efficiency.
REFERENCES:
patent: 676332 (1901-06-01), Marconi
patent: 4868576 (1989-09-01), Johnson, Jr.
patent: 5317325 (1994-05-01), Bottomley
patent: 5446469 (1995-08-01), Makino
patent: 5467096 (1995-11-01), Takamoro et al.
patent: 5546094 (1996-08-01), Egashira
patent: 5548827 (1996-08-01), Hanawa et al.
patent: 5550820 (1996-08-01), Baran
patent: 5594457 (1997-01-01), Wingo
patent: 5612704 (1997-03-01), Cole
patent: 5635943 (1997-06-01), Grunwell
patent: 5661496 (1997-08-01), Baek et al.
patent: 5945953 (1999-08-01), Tsuda et al.
patent: 5945964 (1999-08-01), DeGroot et al.
patent: 6031493 (2000-02-01), Tsuda et al.
patent: 3129045 A (1982-10-01), None
patent: 0511 577 A2 (1992-11-01), None
patent: 2664749 A (1992-01-01), None
patent: 6-37531 (1994-02-01), None
patent: H10173430 A (1998-06-01), None
Patent Abstracts of Japan, JP-0236602, Sep. 30, 1994.
“Antennas” by J.D. Kraus, (McGraw-Hill Book Co., Inc.) pp. 173-178 (1950).
“Microwave Scanning Antennas” edited by R.C. Hansen, Peninsula Publishing, pp. 116-122 (1950).
Burns Doane Swecker & Mathis L.L.P.
Telefonaktiebolaget LM Ericsson (publ)
Wimer Michael C.
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