Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Reexamination Certificate
2003-02-03
2004-08-10
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
C343S757000, C343S893000
Reexamination Certificate
active
06774863
ABSTRACT:
This invention relates to an antenna system and, more particularly, to an antenna system including a plurality of antennas which can be combined in various ways to provide a variety of directivities for the antenna system.
BACKGROUND OF THE INVENTION
A prior antenna system of this type is disclosed in, for example, Japanese Patent Application Publication No. 2001-36327 A laid open for public inspection on Feb. 9, 2001, which corresponds to U.S. Pat. No. 6,498,589 which issued on Dec. 24, 2002 to S. Horii, one of the co-inventors of the present application, and assigned to the same assignee of the present application.
The antenna system disclosed in the above publication includes four unit antennas A, B, C and D which are oriented differently in such a manner that the directivity of each unit antenna is angularly spaced by 90° from adjacent antennas. Selecting means is provided to select one of outputs of the individual unit antennas and adjacent pairs of the unit antennas. A directivity control pulse generator provides a four-bit selection control signal to the selecting means to achieve the selection. The directivity control pulse generator is provided with a directivity selecting switch, which changes the value of the selection control signal cyclically, from, for example, “1000” through “1100”, “0100”, “0110”, “0010”, “0011”, “0001”, and “1001” back to “1000”, each time it is operated. In response to such changes of the selection control signal, the output of the antenna system changes from, for example, the output of the unit antenna A, the combined outputs of the unit antennas A and B, the output of the unit antenna B, the combination of the outputs of the unit antennas B and C, the output of the unit antenna C, the combination of the outputs of the unit antennas C and D, the output of the antenna D, and the combination of the outputs of the unit antennas A and D, back to the output of the unit antenna A. In this way, the directivity of the antenna system is successively switched, for example, clockwise about the antenna system.
The directivity control pulse generator of the described antenna system can change the value of the four-bit control signal only in the above-described order. In other words, the switching of the directivity can be done only in one direction. Accordingly, when the directivity of the antenna system is being changed in the prescribed order to select the best directivity for receiving a desired radio wave, it is not possible to return back in the reverse order if the previous directivity is found to be better than the current one, but it is necessary for the four-bit control signal value to lap in the forward direction in the prescribed order to the previous value. Therefore, it has been required some time to attain the best directivity.
In the described antenna system, no correlation is established between the switching of directivity and the frequency of a desired radio wave. If the antenna directivity is different from one radio wave to another, the directivity selecting switch must be operated each time a different radio wave is to be received, in order to select a desired directivity for the antenna system. Therefore, it is troublesome to set the antenna system in the state to obtain the best directivity.
An object of the present invention is to provide an antenna system which can be rapidly set to have a desired directivity.
SUMMARY OF THE INVENTION
In an antenna system according to a first embodiment of the present invention, a plurality of directivities of an antenna system are successively scanned in a desired direction or order in order to find an optimum directivity to receive a desired radio wave. This scanning is done by operating first and second operating elements.
The antenna system according to the first embodiment has an antenna main body. A plurality of first angularly spaced antennas are disposed within the body in such a manner as to provide the antenna system with a plurality of directivities that enable the antenna system to receive radio waves in a first frequency-band coming toward the body from different first directions around the body. Radio waves in the first frequency band may be, for example, radio waves in the UHF band or the VHF band. The radio waves may be television broadcast radio waves in the UHF or VHF band.
By combining the directivities of the first angularly spaced antennas, it is possible to provide the antenna system with a plurality of directivities that enable the antenna system to receive radio waves in the first frequency band coming toward the body from second different directions which are between adjacent ones of the respective first directions.
First selecting means is disposed within the body. The first selecting means operates to select one output from the outputs of the individual ones and combinations of the first antennas.
Control means is provided separate from the main body. The control means provides a selection control signal to the first selecting means. The control means has first and second operating elements. Each time the first operating element is operated, the control means provides such a selection control signal as to successively scan, in the clockwise direction around the main body, the directivities. Each time the second operating element is operated, the control means provides such a selection signal as to successively scan the directivities of the antenna system in the counterclockwise direction around the main body.
Through the operation of the first operating element, the directivity of the antenna system can be successively switched or rotated clockwise, and, through the operation of the second operating element, the directivity can be successively switched counterclockwise. When an operator is switching the directivity successively clockwise, for example, he or she may find that a desired radio wave can be received most efficiently with the previously selected directivity, and, therefore, may try to reverse the directivity scanning direction to the counterclockwise direction. According to the present invention, such reversal is easy.
Level adjusting means may be disposed within the main body for enabling level adjustment of the output from an individual antenna or combination of individual antennas selected by the first selecting means. An amplifier or a variable attenuator, for example, may be used as the level adjusting means. The control means has a third operating element, in addition to the first and second operating elements, which, when operated, provides a signal commanding the level adjusting means to operate in an operating state represented thereby.
With this arrangement, when the radio wave receiving level is too high or too low, the third operating element may be operated to adjust the signal receiving level to an appropriate one.
The control means may include operating means for transmitting an optical signal in response to operation of the operating elements, and transmitting means provided separately from the operating means. The transmitting means receives the optical signal from the operating means and transmits the selection control signal to the main body. The operating means may include the third operating element in addition to the first and second operating elements.
With this arrangement, the operating means with the operating elements can be disposed at a location remote from the transmitting means, which makes it possible to provide remote controlling of the antenna system.
A plurality of second antennas may be disposed within the body, which are arranged to receive radio waves in a second frequency band coming from the first directions to the body. The second frequency band may be the UHF or VHF band, and the radio waves may be television broadcast signals. The second antennas also have respective directivities, which may be combined in various ways to provide the antenna system with directivities that enable the antenna system to receive radio waves coming to the body from the second directions between adjacent ones of the first directions.
Seco
Fujisawa Shingo
Horii Shotaro
Shibuya Eiji
Shirosaka Toshiaki
Tatekawa Kiyotaka
Duane Morris LLP
DX Antenna Company Limited
Tran Thuy Vinh
Wong Don
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