Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Reexamination Certificate
1999-11-03
2001-11-27
Lobo, Ian J. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
C342S071000
Reexamination Certificate
active
06323802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radar apparatus for use on a vehicle, which is used while being mounted on a vehicle, and, more particularly, to a scanning on-vehicle radar apparatus arranged to scan a scanning area with a radar beam and detect an object in the scanning area accurately without an error.
2. Related Background Art
An example of the scanning on-vehicle radar apparatus is the “scanning radar apparatus for use on vehicle” disclosed in Japanese Patent Application Laid-open No. 9-145833. This radar apparatus is provided with measures for accurately detecting individual objects, based on a history of detected data.
SUMMARY OF THE INVENTION
This conventional apparatus is, however, provided with no countermeasures against improper detection called a ghost.
The ghost is a result of improper detection of an absent object as if to exist. In other words, the ghost is a detected object image having no corresponding object existing actually.
This ghost is created by a sidelobe of the radar beam.
Signal intensities of reflected waves from an object existing in a direction of the sidelobe of the radar beam are sufficiently weaker than those of reflected waves from an object existing in a direction of the main lobe of the radar beam.
Therefore, the reflected waves of low signal intensities are normally ignored on the occasion of creating the detected object image, whereby the detected object image can be created substantially using only the reflected waves from the object in the main lobe.
However, if there exists an object with relatively high reflectance in the direction of the sidelobe the apparatus can receive the reflected waves strong enough to recognize it as an effective object in some cases. In such cases, the radar apparatus recognizes that there exists the object in the direction of the main lobe. Namely, the ghost appears in the direction of the main lobe.
For avoiding it, it is conceivable to employ an antenna forming as small sidelobes as possible. In general, the greater the antenna size, the smaller the sidelobes. However, the compact and lightweight structure is an important factor for the radar apparatus for use on the vehicle, and there is a limit to increase of the antenna size.
There were thus desires for the on-vehicle radar apparatus without improper detection based on the ghost and without increase in the antenna size.
Particularly, where the detection result of the radar apparatus is utilized for automatic tracking control or the like, it is important to remove the ghost appearing ahead on the currently running lane, and there were thus desires for the on-vehicle radar apparatus that can accomplish it.
The present invention has been accomplished in order to solve the above problem, and a radar apparatus of the present invention comprises radar beam scanning means for scanning a scan area with a radar beam substantially in parallel to a road surface on which a vehicle is running, and object detecting means for receiving reflected waves of the radar beam and creating a detected object image, based on the reflected waves, wherein the object detecting means comprises ghost determination means for determining whether a detected object image created is a ghost.
Thanks to provision of the ghost determination means, it becomes possible to remove a detected object image determined as a ghost from detected object images created.
The ghost determination means is desirably one for determining whether a first detected object image is a ghost, based on a second detected object image. The first detected object image stated herein is a detected object image appearing at a position assumed to be on the currently running lane, and the second detected object image is a detected object image appearing at a position assumed to be on an adjacent lane to the currently running lane.
The size and direction of each sidelobe to the main lobe are defined corresponding to the antenna used. Therefore, supposing that the first detected object image is a ghost originating in an object on another lane (adjacent lane), a predetermined relation can be established between the position, the relative velocity, etc. of the existing object on the adjacent lane, which produces the ghost, and the position, the relative velocity, etc. of the ghost.
Then the ghost determination means can determine that the first detected object image is a ghost in a high probability when the first detected object image satisfies a predetermined relation to the second detected object image.
Particularly, when the distance and relative velocity of the second detected object image are approximately equal to the distance and relative velocity, respectively, of the first detected object image, there is a high probability that the first detected object image is a ghost. Therefore, this is desirably employed as a necessary condition to determine that the first detected object image is a ghost.
In addition, the first detected object image is a ghost in a high probability when an angle between the direction of the first detected object image and the direction of the second detected object image is within a predetermined range. Therefore, this is desirably adopted as a necessary condition to determine that the first detactad object image is a ghost.
Further, there is a probability that the first detected object image is a ghost, if the distance of the first detected object image is in a predetermined range. Therefore, this is desirably adopted as a necessary condition to determine that the first detected object image is a ghost.
Moreover, it is desirable to carry out the object detection process without interruption and determine that the first detected object image is not a ghost, with a higher priority than the other determination conditions, when it is determined that the first detected object image is the same as the detected object image in the preceding detection process.
This means that the ghost determination is admitted only when the first detected object image emerges suddenly. This can considerably lower the probability of misjudging an actually existing object as a ghost.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5670963 (1997-09-01), Kubota et al.
patent: 5734344 (1998-03-01), Yamada
patent: 5793325 (1998-08-01), Yamada
patent: 3314 363 (1983-04-01), None
patent: 6-174821 (1994-06-01), None
patent: 9-145833 (1997-06-01), None
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Lobo Ian J.
Toyota Jidosha & Kabushiki Kaisha
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