Telecommunications – Transmitter and receiver at same station – Having particular housing or support of a transceiver
Reexamination Certificate
1999-05-18
2001-12-25
Maung, Nay (Department: 2681)
Telecommunications
Transmitter and receiver at same station
Having particular housing or support of a transceiver
C455S575100, C343S702000, C343S853000, C343S895000
Reexamination Certificate
active
06334048
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a system including an antenna device and feed device for transmitting and receiving RF waves. Specifically, it relates to a system for a mobile radio communication device, e.g., a hand-portable telephone, which is capable of both transmitting and receiving on multiple separate frequency bands.
In the communication services today it is an increasing demand for availability and small sizes of the user units. A user of a hand-portable communication unit wishes to be reached wherever his location may be. This puts requirements on the operators to provide for good coverage of their mobile networks. For areas with few users, e.g. in low-populated areas, at the countryside, or at sea, it is uneconomical or impossible to provide for good coverage by means of terrestrial mobile phone systems. For such areas, good coverage can be obtained by means of communication via satellites. Since communication with linearly polarized RF waves, which are used in the terrestrial mobile communication systems, requires a certain degree of alignment between the transmitting and receiving antennas, this type of signals are unsuitable for satellite communication. Instead circularly polarized RF waves are used. This means that a special type of antenna has to be used. It is practical when the same mobile telephone can be used for both satellite communication and terrestrial communication. To obtain this, telephones have been provided with two antennas.
This does not comply with the demands on antennas for hand-portable telephones, to be compact, and to occupy a small space.
RELATED ART
U.S. Pat. No. 5,628,057 discloses a radiotelephone transmitter having an antenna for satellite communication. The antenna is attached to the telephone at a pivot point. This antenna only operates in a circular polarization mode, and is not provided with means for operation in a linear polarization mode.
Each of WO 96/06468, WO 97/37401 and EP 0 791 978 discloses an antenna for receiving circularly polarized RF waves in a satellite positioning system (GPS). Each of the antennas includes a ceramic core having four helical radiating elements. A feeder line passes through the core from the bottom of the antenna, and is connected to the radiating elements at the top of the antenna. The self phasing structure of the antenna and the feeding thereof makes the antenna operable in a very narrow frequency band, viz. a relative bandwidth of a few tenths of a percent. This is sufficient since the antenna is designed for receiving GPS signals. It is not suitable for two way radio communication, where a relative bandwidth of a few or up to ten percent is required.
Further, U.S. Pat. No. 5,600,341 discloses an antenna operating with circular polarization and linear polarization. A QHA (quadrifilar helical antenna) for circular polarization is stacked on a linear antenna fed by a two wire helix. The linear antenna operates with linear polarization and a part of the antenna function is performed by the two wire helix, although some coupling to the feed line will occur. This document does not teach how the quadrifilar helical antenna should operate with linear polarization. No phasing network is described, and the helix is therefore supposed to be self-phased although this is not mentioned. A self-phased helix is an antenna operating in a very narrow frequency-band, and usually limited to GPS service where <0.2% bandwidth is required. For most satellite telephone bands a self-phased QHA has a quite insufficient bandwidth. Due to the stacking of the antennas for circular polarization and for linear polarization, the disclosed antenna means is space demanding, and uses the antenna volume in an inefficient way.
JP-A-09219621 discloses an antenna for linear polarization stacked on a helical antenna for circular polarization. Since a helical antenna having less then three helices normally need to have a circumference of &lgr; to give circular polarization, this antenna must be very space demanding or work in some other way which is not explained. No phasing network is present, and is not needed if the helices are self-phased, but then a very narrow frequency band is achieved.
JP-A-08298410 discloses an antenna including two helices, one inside the other. The inner helix is extendable, and when extended it acts as an antenna for circular polarization. Since only one helical element is present the circumference has to be &lgr; in order to give circular polarization, why also this antenna must be very space demanding. In the retracted state of the inner helix the antenna acts as an antenna for linear polarization. No phasing network is needed since only one helical element is employed for achieving the circular polarization.
RELATED PATENT APPLICATIONS
The following patent applications are related to the same technical field as the invention of this application, and are hereby incorporated herein by reference:
the Swedish patent application SE 9801755-1 having the title “Antenna device comprising capacitively coupled radiating elements and a hand held radio communication device for such antenna device”, filed in Sweden the same day as this application, May 18, 1998, applicant Allgon A B,
the Swedish patent application SE 9801753-6 having the title “Antenna device comprising feeding means and a hand held radio communication device for such antenna device”, filed in Sweden the same day as this application, May 18, 1998, applicant Allgon A B, and
the Swedish patent application SE 9704938-1, filed Dec. 30, 1997, applicant Allgon A B, having the title “Antenna system for circularly polarized radio waves including antenna means and interface network”.
SUMMARY OF THE INVENTION
A main object of the invention is to provide an antenna system including an antenna device and feed device for transmission/reception of circularly polarized RF waves in a first mode of operation and for transmission/reception of linearly polarized RF waves in a second mode of operation.
It is also an object of the invention to provide an antenna system which can be used for satellite communication and terrestrial mobile communication, and occupies a small space.
It is also an object of the invention to provide an antenna system providing good isolation between the radiating structure for circularly polarized waves and the means for excitation of said radiating structure for operation with linearly polarized waves, in order to avoid that the high transmission power for one polarization mode will damage the sensitive receiver of the other polarization mode.
Another object of the invention is to provide an antenna system which exhibits high efficiency in different frequency bands and modes of operation, and advantageous radiation lobe pattern.
It is a further object of the invention to provide an antenna system that exhibits broad band characteristics, necessary for radio telephone use within most systems.
These and other objects are attained by an antenna means according to the appended claims.
By the features of claim
1
it is achieved an antenna system having a good antenna function, since the current maximum in linear polarization mode can be located high above a telephone.
Through the arrangement of a central radiator in the radiating structure, it is achieved an efficient and uniform excitation of the helical radiating elements in order to provide for transmission/reception of linearly polarized RF waves in a second mode of operation.
Through the arrangement of the centrally arranged radiator protruding beyond the second end of the radiating structure for circularly polarized RF waves, it is achieved an improved antenna operation in the linear polarization mode.
REFERENCES:
patent: 4011567 (1977-03-01), Ben-Dov
patent: 5600341 (1997-02-01), Thill et al.
patent: 5628057 (1997-05-01), Phillips et al.
patent: 5721557 (1998-02-01), Wheeler et al.
patent: 5986619 (1999-11-01), Grybos et al.
patent: 0791978 (1997-08-01), None
patent: WO96/06468 (1996-02-01), None
patent: WO97/37401 (1997-10-01), None
Patent Abstracts
Barone Gianni
Bohannan Richard
Edvardsson Olov
Norén Per
Allgon AB
Jacobson & Holman PLLC
Maung Nay
Vuong Quochien B.
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