Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-08-24
2001-10-02
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S776000
Reexamination Certificate
active
06297783
ABSTRACT:
The present invention relates to a method of, in an antenna arrangement which comprises a feeder network, a radiating element and a reflector system and scans space in a first plane, bringing about increased resolution in a second plane at right angles to the first plane. The invention also relates to an antenna arrangement forming part of an auxiliary system, working according to radar principles, for vehicles, which arrangement is connected to a signal source and/or a signal receiver and comprises a feeder network, a radiating element and also a reflector system for distributing output power from the radiating element or, respectively, focusing incoming radiation from space onto the radiating element.
An antenna arrangement according to the above is previously known from our earlier Swedish Patent 505 599. The antenna has a disc-shaped lobe and is intended to scan an area in the horizontal plane of the order of 10-15 degrees. This is brought about by rotating the main reflector in a reflector system of the Cassegrain type.
The known antenna arrangement has no resolution in the elevation direction. It has, however, become desirable to be able to equip the known type of antenna arrangement with some form of elevation resolution. By introducing elevation resolution, the antenna arrangement can be used in order to distinguish stationary objects on the roadway, e.g. cars, from objects above the roadway, e.g. bridges and road signs.
The object of the present invention is to produce a method and an antenna arrangement which not only afford resolution in a first plane, preferably the horizontal plane, but also afford at least limited resolution in a plane at right angles to the first plane, preferably the vertical plane. The object of the invention is achieved by a method characterized in that the phase center of the radiating element is moved relative to the reflector system in the elevation plane by dividing the radiating element and feeding the divided radiating element according to at least a first and a second power distribution model, and also an antenna arrangement characterized in that the radiating element is designed so as to be divided into at least two radiating part-elements and in that the feeder network comprises a distribution network adapted to distribute the signal power between the radiating part-elements according to at least two different power distribution models.
In this context, phase center means a point in space, which is fixed in relation to the antenna. For this point, it is ideally true that the wave radiated from the antenna has the same phase position on all spheres with their center point at this point. The point can also be regarded as the point where radiation takes place, i.e. the origin of the radiation. For the great majority of antennas, there is no such point but, if the phase position is constant over that part of the sphere which is delimited by the main lobe, the center point of the sphere is still called the phase center of the antenna. For a more detailed description of the phase center, refer to IEEE Standard Test Procedures for Antennas, ANSI/IEEE Std 149-1979, ISBN 0-471-08032-2.
The two power distribution models result in the generation of two different lobes in elevation. In this connection, it is possible to make one lobe, the normal lobe, point absolutely horizontally, while the second lobe, the elevation lobe, can point slightly upwards, e.g. 2-4 degrees above the horizontal plane. Both the lobes can be scanned in azimuth.
The distribution of power between the divided radiating elements can be effected stepwise or continuously according to the desired type of sweep of the lobe(s) of the antenna arrangement. According to a preferred embodiment, the power is distributed between the radiating part-elements so that, for generating the elevation lobe, all the power is assigned to only one radiating part-element while, for the normal lobe, the power is distributed between two radiating part-elements so that both part-elements receive power.
The embodiment of the radiating element of the antenna arrangement may vary in many respects. For example, according to an envisaged embodiment, the antenna arrangement may comprise a separate radiating element for receiving and a separate one for transmitting and either one radiating element or both can be divided into two radiating part-elements. The possibility of varying the design of the radiating elements within wide limits allows, inter alia, the cost of the total number of components that are required to be kept down.
According to an advantageous embodiment, the radiating part-elements consist of horns. The reflector system of the antenna arrangement can be of the Cassegrain type for distributing or, respectively, focusing the radiation, and a combination of horns as radiating part-elements with a reflector system of the Cassegrain type has proved to be advantageous.
In order to distribute the signal power between the radiating part-elements according to two power distribution models, the distribution network comprises, according to another advantageous embodiment, a first and a second hybrid and a phase rotator, one output on the first hybrid being connected directly to one input on the second hybrid and the other output on the first hybrid being connected to the other input on the second hybrid via the phase rotator. The phase rotator can be variable. By varying the phase rotation in the variable phase rotator, the power can be distributed arbitrarily between two associated radiating part-elements. Advantageously, the phase rotator can be assigned a first and a second fixed position so that, in the first position, the power is distributed between the radiating part-elements and, in the second position, all the power is fed to one of the radiating elements.
Advantageously, the phase rotator consists of a third hybrid provided with a first and a second waveguide on the output side and a short circuit which can be introduced into each waveguide. So as to allow introduction of the short circuits into the waveguides, the latter are preferably provided with slots in two opposite delimiting surfaces at those ends of the waveguides which are distant from the hybrid. According to the proposed embodiment, the short circuits can be introduced by a linear movement or by a movement following the arc of a circle. According to a specific preferred embodiment, the short circuits are arranged in association with the periphery of a rotatable circular disc, the peripheral part of which passes through the slots of the waveguides during rotation. In this connection, the circular disc can constitute a part of the rotor in a motor included for rotating the disc. The material in the disc should have a low dielectric constant. Expediently, the short circuits consist of metal strips, such as copper strips.
By virtue of the embodiment according to the previous paragraph, the short circuits can be made very much alike in the two waveguides and good matching is achieved automatically. Integration of motor and disc has proved to be advantageous, inter alia with regard to moment of inertia, power requirement and heat generation.
The hybrids can consist of 90 degree hybrids, but it is also possible to introduce another hybrid type, for example 180 degree hybrids.
REFERENCES:
patent: 3611396 (1971-10-01), Jones, Jr.
patent: 3955202 (1976-05-01), Young
patent: 4308538 (1981-12-01), Albersheim
patent: 5467072 (1995-11-01), Michael
patent: 5963174 (1999-10-01), Larsson et al.
patent: WO 96/36088 (1996-11-01), None
IEEE Standard, “Test Procedures for Antennas”, ANSI/IEEE std. 149-1979, ISBN 0-471-08032-2.
Bäck Ingemar
Forslund Ola
Olofsson Joakim
Sjöstrand Per
Celsiustech Electronics AB
Connolly Bove Lodge & Hutz
Nguyen Huang
Wong Don
LandOfFree
Antenna arrangement and a method in connection with the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Antenna arrangement and a method in connection with the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antenna arrangement and a method in connection with the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2605852