Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Patent
1997-12-11
1999-09-28
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
342145, 342146, G01S 1393
Patent
active
059595710
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a radar device which receives a reflected wave of a transmitted wave, reflected from an object, thereby measuring a relative speed, a distance and an azimuth of an object, and particularly to a radar device for use in a vehicle.
BACKGROUND ART
As a radar device of the aforementioned kind, there is conventionally known a device as shown, for example, in Japanese Patent Application No. Hei 7-271514 (filed Oct. 19, 1995, published as Japanese Patent Preliminary Publication No. Hei 8-278362), which obtains, utilizing the spread spectrum modulation technique, correlation between a received signal from an object and a pseudonoise signal (hereunder referred to as "PN code") consisting of a sequence of pseudonoise codes, and detects an object and measures a relative speed thereof and a distance thereto, utilizing a peak value of that correlation. However, measurement of an azimuth of an object is not referred to in this kind of radar device.
As a radar device which performs measurement of an azimuth of an object, there is known, for example, a device using a beam switching system, which arranges a plurality of receiving antennas having a narrow beamwidth, capable of determining an azimuth easily and having a differently oriented beam from each other, and connects those receiving antennas sequentially one by one. There is also known a radar device, for example, using a mechanical system, which swings a single receiving antenna mechanically, thereby to change the direction of a beam. Further, there is known, for example, a radar device using a electronic system, which uses a phased array antenna and changes the direction of a beam electronically. In conventional radar devices, an azimuth of an object is measured utilizing the above mentioned systems to receive a reflected wave from an object.
The case in which a radar device performing azimuth measurement is used, for example, as a radar device installed in a vehicle will be explained hereunder. First, explanation will be given of an example of a radar device using a beam switching system, where the range of azimuth of measurement, it is necessary to arrange planar antennas having a determine an azimuth of an object uniquely. Therefore, ten antennas are needed in all.
Generally, there lies the following relation between directivity and dimension of an antenna: feeding method
As is clear from the above, directivity of an antenna is inversely proportional to the dimension of an antenna, if the same frequency and the same feeding method are used. When a planar array antenna as described above is used and the half power beamwidth coefficient k and used side are needed as receiving antennas.
As described above, a radar device using a beam switching system needs to arrange many antennas when a wide range of azimuth measurement is desired. Therefore, a radar device using a beam switching system is not suited to be installed in a vehicle which has only limited space for installation, and the range of application of this kind of radar device is limited. A radar device using any of the other systems mentioned above is not suited to be installed in a vehicle, if it likewise needs to arrange many antennas.
In addition, a radar device using a mechanical system as mentioned above needs a motor, an actuator and their power supply in order to swing an antenna. Thus, a radar device of this kind takes a long time to change an antenna, and takes high manufacturing cost in order to ensure reliability in precision of its mechanical parts. On the other hand, a radar device using an electronic system as mentioned above needs a phase controller for each antenna element, which controls an electric wave so that it may have a phase calculated according to a predetermined operation, and thereby controls directivity. However, a phase controller for a band of micro wave or millimeter wave, which is the band used by a vehicle, is expensive, so that a radar device using an electronic system is not suitable for a vehicle.
As a system for use in a
REFERENCES:
patent: 4219812 (1980-08-01), Rittenbach
patent: 5731781 (1998-03-01), Reed
Aoyagi Yasushi
Fukuchi Toshihide
Inoue Kiyoshi
Kohno Ryuji
Sotomayor John B.
The Furukawa Electric Co. Ltd.
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