Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1999-11-24
2001-04-03
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C455S090300
Reexamination Certificate
active
06211829
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to an antenna means for a radio device provided with a radio transfer or radio communication facility. An antenna means of this kind is for radio communications. Specifically, the invention relates to an antenna means for a device that is mobile or portable. More specifically, the invention relates to an antenna means for a personal (cellular) telephone having a small internal depth for receiving the antenna means. Such a telephone may be a terminal in, e.g., a GSM, an AMPS, or a JDC cellular telephone system.
In a radio device, such as a personal telephone, it is advantageous to achieve an antenna means that has an effective radiation distribution and a high degree of efficiency. These parameters of the antenna means effect its ability to transfer electro-magnetic radiation energy between the radio device, being a first terminal, and a radio communication means. The radio communication means may be a second terminal or a base station, e.g., in any of the above-mentioned cellular telephone systems, with the capacity of establishing a communication connection between the telephone and a second terminal.
The telephone may function in different operating modes. Two different operating modes are a stand-by mode and a call (talk) mode. In these two operating modes there may be different demands upon the antenna means. For example, if the telephone is carried in the stand-by mode, the carrier (a person) may require a small-size and compact configuration of the telephone. An antenna means configuration extending outward from the telephone may be inconvenient in this case.
The reception and transmission performance of an antenna means depends not only on the antenna means itself, but also on a radiation path between the telephone and the radio communication means. Obstacles in the radiation path will lower the antenna performance. In personal telephones it is important that the body of the user does not excessively obstruct the radiation path. Therefore, an antenna means extending sufficiently from the housing of the telephone is required. Demands for performance are higher in the call mode.
PRIOR ART
A type of antenna means that has been used on personal telephones to provide satisfactory performance is disclosed in, e.g., U.S. Pat. No. 4,868,576, WO 94/10720, and WO 94/28593. These antenna means use a helical antenna mounted on a housing of a telephone. Movably through the helical antenna there is provided an elongated radiator that is extendable to increase antenna performance when needed. The disclosed antenna means use extendable antennas with a non-conductive top portion. This requires that the telephones are able to receive all of a radiating portion of the elongated radiator in its retracted position. This creates problems in modern small-size telephones. The above-mentioned documents are incorporated by reference.
OBJECTS AND SUMMARY OF THE INVENTION
The invention is particularly directed toward providing an antenna means that overcomes the deficiencies of the above-mentioned prior art antenna means when an elongated radiator thereof is in a retracted position.
Thus, an object of the invention is to provide a small-size antenna means for a small-size radio communication device. It is desirable to provide an antenna means that is short in overall length compared to the total length of radiator elements combined in the antenna means (at given electrical radiator lengths).
Another object of the invention is to provide an antenna means that occupies a small space inside the radio communication device. For example, as the length of a portable telephone housing is reduced there is a demand for an antenna means with less length inside the housing.
Another object of the invention is to provide an antenna means maintaining high efficiency in order to keep up operating range of a radio communication device and, if the radio communication device is output power controlled, to reduce output power in transmitting from the radio communication device, especially in a battery-powered personal telephone.
Another object of the invention is to provide an antenna means, whose elongated radiator is has an improved ability to resume an original shape after bending, especially when the elongated radiator is retracted in a curved path.
Another object of the invention is to provide an antenna means is not particularly sensitive to a variation in the upper end position of the elongated radiator in its retracted position. Such variations may be caused by variations in manufacturing or by operator handling.
The extendable elongated radiator of the antenna means, when in a retracted position, extends at least partially inside the helical radiator in order to reduce the total length of the antenna means. When mounted on a radio communication device this antenna means does not extend as far into the device as prior art antenna means of this type. The antenna means of the invention also allows a shorter portion of insulating material between the elongated radiator and the knob, thus giving the extendable whip more of the mechanically resilient properties of the elongated radiator. Further, this antenna is suitable for keeping low the sensitivity to variations in the upper end position of the elongated radiator when retracted.
Preferably, in order for the antenna means to function efficiently when the elongated radiator is retracted, the electrical parameters of helical antenna have to diverge from those of helical antenna without influence from an elongated radiator. Firstly, the coupling (coupling mismatch) between the helical antenna and the retracted elongated radiator is minimized, by increasing the ratio of the diameter of the helical antenna (within design limits) to the diameter of the elongated radiator, as well as by selecting a suitable material for the dielectric body. Secondly, the length of the helical antenna of the invention is adapted in order to achieve satisfactory resonance in spite of the retracted elongated radiator. Other parameter alterations, such as other geometrical changes, especially arranging the elongated radiator to co-extend only partially with the helical radiator, are possible and advantageous for compensating the capacitance and inductance introduced on the helical antenna. A matching unit may also be used to improve performance of the radiators.
In case a conductive sleeve is used as conventionally to fasten the helical radiator and the movable elongated radiator onto the housing of the radio communication device, it is advantageous to arrange the sleeve so that a capacitance formed between the sleeve and the elongated radiator compensates for a mainly inductive coupling between the lower and middle portion of the helical radiator and elongated radiator, in order to increase impedance between the elongated radiator and helical radiator, hence reducing the coupling between them.
There may advantageously be arranged means inside the housing of the radio communication device to limit the influence of the elongated radiator on the helical radiator.
Preferably, the retracted radiator may be coupled to signal ground a distance of approximately one quarter of a wavelength from said a feed point, essentially being the conductive sleeve, of said helical radiator.
The antenna means of the invention is advantageously used where a prior art antenna of the above-described type is desired, but the receiving depth of the radio communication device is too small.
It is possible to arrange the antenna means according to the invention such that the extendable elongated radiator extends to a position wherein it is coupled galvanically or inductively capacitively via the helical antenna to the circuitry of the radio communication device. In this case the elongated radiator may extend partially inside the helical radiator.
REFERENCES:
patent: 4868576 (1989-09-01), Johnson, Jr.
patent: 5343213 (1994-08-01), Kottke et al.
patent: 5353036 (1994-10-01), Baldry
patent: 5389938 (1995-02-01), Harrison
patent: 5467097 (1995-11-01), Toko
pa
Lofgren Stefan
Saldell Ulf
Allgon AB
Clinger James
Jacobson Price Holman & Stern PLLC
Wong Don
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