Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
1999-08-12
2001-02-06
Issing, Gregory C. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
Reexamination Certificate
active
06184828
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to beam scanning antennas used for radar antennas, mobile communication antennas, satellite broadcasting receiving antennas, satellite-installed-antennas, and so forth.
2. Description of the Related Art
In antennas used for radars, mobile communications, satellite broadcasting reception, and so forth, a function which freely scans a beam in a desired direction is important. For example, when a mobile communication is performed, a mobile station (for example, an automobile or an airplane) is usually moving. Thus, a beam radiated from the antenna of the mobile station is not always directed to a predetermined direction. In this case, the beam of the antenna should be tracked to the predetermined direction (namely, the direction of an objective station which receives and/or transmits radio waves). As a means for scanning the beam of an antenna, the following methods have been employed.
As a first method, a beam is scanned by a mechanical driving means.
FIG. 103
shows the construction of an example of a mechanical driving means which scans a beam. The mechanical driving means for scanning the beam requires an elevation (vertical plane) driving member and an azimuth (horizontal plane) driving member. In the mechanical driving means, the beam scanning process does not adversely affect the electric characteristics (such as radiation directivity) of an antenna
1
.
However, the construction of the driving mechanism becomes complicated. In addition, there is a problem on durability of the rotary joint used for the driving mechanism. In particular, in a mobile communication, a lower and flat antenna is required. Thus, the mechanical driving method is disadvantageous.
As a second method, an electrical beam-scanning method is known.
FIG. 104
shows the construction of an example of an electrical beam-scanning method. As shown in the figure, a plurality of antenna elements
2
are electrically connected to corresponding phase shifters
3
. In the receiving operation, signals received from the antenna elements are combined by a feeding circuit
4
. In the transmitting operation, a signal is distributed to the antenna elements
2
by the feeding circuit
4
. The exciting phases of the antenna elements are adjusted by the phase shifters so as to scan the beam in a desired direction. In this method, since all the antenna elements
2
, the phase shifters
3
, and the feeding circuit
4
are disposed on the same plane, the beam scanning antenna can be thinly formed.
However, in this method, since each antenna element requires a phase shifter, the size of the beam scanning antenna becomes large. In addition, the cost of the antenna increases. Moreover, to control the phases of the phase shifters
3
, a control circuit is required. Thus, the construction of the antenna becomes complicated.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a beam scanning antenna whose feeding system is simply constructed.
A second object of the present invention is to provide a beam scanning antenna which is easily produced.
A third object of the present invention is to provide a beam scanning antenna which is produced at low cost.
A fourth embodiment of the present invention is to provide a beam scanning antenna which is very effective for an antenna installed in a mobile station.
To solve the above problems, the present invention is a beam scanning antenna, comprising: a plurality of unit radiation elements for receiving or transmitting radio waves, a radiation direction of each of said unit radiation elements being discretely selected so as to be along a conical plane, the conical plane being composed of a set of lines which are disposed with a predetermined angle to a reference direction, the radiation elements being disposed so that the received or transmitted radio waves are strengthen by each other.
The present invention is an array antenna having a plurality of antenna elements, each of which has a means for scanning a beam in the direction of a tilt angle &thgr; from a boresight of the beam scanning antenna and electrically varying the direction of a rotation angle &phgr; of the beam. By arraying the antenna elements, the beam is formed in the direction of the angle &thgr; to the boresight of the antenna. The rotation angle &phgr; of the beam on an antenna element pattern can be electrically varied. The present invention is an array antenna having a plurality of antenna elements which form a plurality of antenna arrays, wherein the optical path difference of radio waves transmitted or received by each of the antenna arrays in the directions of a plurality of direction angles &phgr; on the plane tilted for an angle &thgr; to a boresight of the beam scanning antenna is nearly a multiple of the wave length. Thus, when the antenna elements are excited in the same phase, the gains in these directions can be increased.
The present invention is a beam scanning antenna having a means for shifting the exciting phases of signals of the radiation elements for every 180 degrees or 90 degrees.
The present invention is an array antenna comprising a plurality of antenna elements, each of which has a means for electrically varying the direction of a beam, the direction of the beam can be controlled for each antenna element. When these antenna elements are arrayed, under the control of one-bit or two-bit variable phase shifters connected thereof, the exciting phase can be varied for every 180 degrees or 90 degrees. Thus, the beam of the composite radiation field of the array antenna can be scanned to the desired direction.
The present invention is a beam scanning antenna, comprising a plurality of antenna elements, each of which has a plurality of operation modes, wherein the antenna elements are microstrip antenna members or horn antenna members, wherein each of the antenna element is connected to a low-bit variable phase shifter, and wherein a feeding circuit or a distributing circuit Us formed for each of the modes, the feeding circuit or the distributing circuit being connected to a high-bit variable phase shifter, so as to combine or distribute radio waves of each of the modes. Thus, the beam direction can be controlled for each antenna element. In addition, the phase of each mode for each antenna element can be coarsely varied. In the receiving operation, the signals received from all the antenna elements are combined by the feeding circuit. In the transmitting operation, the signal is distributed to all the antenna elements. The signal which has been combined or the signals which have not been distributed are precisely phase-shifted. Signals with a phase difference in each mode can be combined or distributed by the combining device or distributing device. Thus, the direction of the beam can be controlled for each element antenna. Consequently, the phase of each mode for each antenna element can be coarsely varied. In addition, when a sub array is constructed of at least two antenna elements, the direction of a beam can be controlled for the sub array. When an array antenna has a plurality of such sub arrays, each of which has a means for shifting the exciting phase thereof for every 180 degrees or 90 degrees, the beam of the composite radiation field of the array antenna can be scanned to a desired direction.
According to the present invention, a beam scanning antenna which electrically varies the direction of the rotation angle &phgr; on the plane tilted for the elevation angle &thgr; from the boresight can be provided. In comparison with the conventional electrically scanning antenna, the number of phase shifters can be remarkably reduced. Thus, the construction of the feeding system can be simplified, thereby decreasing the production steps of the antenna. Since the number of phase shifters is reduced, the production cost is also decreased. Since the antenna which electrically scans the beam can be formed in a plane shape, it is very effective for an antenna installed in a mobile station.
Accordin
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Issing Gregory C.
Kabushiki Kaisha Toshiba
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