Communications: radio wave antennas – Antennas – Plural diverse-type antennas using same active element
Reexamination Certificate
1995-01-30
2001-05-22
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Plural diverse-type antennas using same active element
C343S770000
Reexamination Certificate
active
06236374
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an antenna arrangement in which at least two frequencies can be transmitted by means of a single antenna.
In the mobile radio communication field, there is a need to be able to transmit signals in different frequency bands. Furthermore, it is desirable, in satisfying this need, to be able to use a single antenna arrangement. An antenna arrangement for transmitting AM/FM and microwave, is described in U.S. Pat. No. 4,968,991. The solution described in U.S. Pat. No. 4,968,991 can, at most, be utilised for frequencies up to 3 GHz. This antenna arrangement also comprises inner and outer conductors and tubes.
The requirement for transmitting several frequencies in, for example, mobile radio traffic, is combined with the requirement of speech communication and, respectively, the transmission of traffic information. It is intended to transmit traffic information in a higher frequency band than the one utilised for normal radio communication.
It is possible to arrange different antennas for different frequencies. These antennas can be placed, for example, on the roof of a vehicle, such as a car, on its rear view mirrors, or at the front of the vehicle. When microwaves are transmitted by an antenna, it is desirable that the range is limited. This can be done, for example, by mounting the antenna element at the front of the vehicle. One difficulty with such an arrangements is that both the antenna element and the feed line for the antenna element become soiled by dirt, and the like, from the roadway. Soiling causes shielding of the radio waves and thereby gives rise to impaired transmission efficiency for the antenna. There is, therefore, a requirement for an antenna arrangement for vehicles, which is not affected by dirt from the roadway.
It is considered that frequencies in the GHz range are suitable for the transmission of traffic information. The relevant frequency ranges are of the order of 10 GHz and higher.
It is an object of the present invention to provide an antenna arrangement for simultaneously transmitting UHF and the X and K frequency bands utilizing a single coaxial antenna arrangement. Antenna arrangements adapted for transmission in the 10 GHz frequency range have not, hitherto, been available.
SUMMARY OF THE INVENTION
The present invention provides an antenna arrangement for transmitting at least two frequencies comprising a waveguide antenna element that is of a length matched to a fraction of the wavelength of the lower of the said at least two frequencies, that is short circuited at one end thereof, and that has slots formed in the wall of the waveguide, at the short circuited end thereof, for the transmission of the higher of the said at least two frequencies; first waveguide means for feeding the said higher frequency directly to the antenna element at the other end thereof; and second waveguide means for capacitively coupling the said lower frequency to the antenna element.
According to one aspect of the present invention, the first waveguide means include a first waveguide feed line, which is formed integrally with the antenna element to provide a single waveguide unit, the internal structure of the single waveguide unit being used as a waveguide for the higher frequencies that are transmitted via the slots in the wall of the waveguide.
According to another aspect of the present invention, the second waveguide means include a second waveguide feed line, and a capacitor connected between the antenna element and one end of the second waveguide feed line.
According to a further aspect of the present invention, the said other end of the antenna element is at earth potential.
With the present invention, no special balun or high-pass filter is required for feeding the higher frequencies to the antenna arrangement.
An advantage of the present invention is that it provides a very simple and inexpensive antenna arrangement.
Furthermore, it is possible with the present invention to transmit frequencies in excess of 3 GHz, which, as stated above, is probably the highest frequency that can be transmitted by known antenna arrangements.
The antenna arrangement according to the present invention is adapted to transmit frequencies up to the range of 100 GHz, the higher frequencies transmitted by the antenna element being greater than 1 GHz.
The foregoing and other features according to the present invention will be better understood from the following description with reference to
FIG. 1
of the accompanying drawings, which illustrates an antenna arrangement according to the invention that is adapted to transmit at least two frequencies and has an antenna of a length that is matched to a fraction, for example, ⅝ths, of the wavelength of the lowest of the said at least two frequencies.
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Moxon, “HF Antennas For All Locations”, published by RSGB, Pitman Press, Bath, 1984, pp. 114,115,161 and 162.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Televerket
Wimer Michael C.
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