Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
1999-09-13
2001-09-11
Lobo, Ian J. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S368000
Reexamination Certificate
active
06288672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a holographic radar having a plurality of reception antennas for receiving reflection waves of a radio wave transmitted from transmission antennas, and especially to such a holographic radar in which radar signals are acquired in a time-shared manner by the connections of the plurality of reception antennas switched in sequence to a receiver.
2. Description of the Related Art
An example of conventional holographic radar is disclosed in Japanese Patent Laid-open Publication No. Sho 63-256879. In that example, a single transmission antenna is provided to transmit a radio wave, with a plurality of reception antennas receiving reflection waves of the radio wave transmitted. The plurality of reception antennas are then connected via a switch to a single receiver. The plurality of reception antennas are switched in sequence for the connection to the receiver so that radar signals obtained for each reception antenna can be acquired in a time-shared manner.
Such a configuration enables the number of receiver for a plurality of reception antennas to be single and achieves a reduction in size and production cost of the device. It is to be noted that this example includes a reception antenna array consisting of multiple reception antennas, which are associated with a single receiver in groups of four antennas.
The radio wave used herein are in a high-frequency band of, for example, 76 GHz. For this reason, signals handled in the transmission line from the reception antennas to the receiver are signals belonging to the high-frequency band. The switch for switching such high-frequency signals typically has two or three throws.
Because of the above configuration, a plurality of switches are often required for the switching of four or more reception antennas. For example, multi-switching can be implemented through a combination of single pole double throw (SPDT) switches or single pole triple throw (SP3T) switches in a tournament form. Unit switches used therein can be planar circuit type high-frequency switches such as MMICs (microwave monolithic integrated circuits) or HICs (hybrid integrated circuits).
Use of switches in multi-stage connection, however, may cause a degradation in reception sensitivity since a signal will be attenuated every time it passes through each switch.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide a holographic radar capable of preventing any degradation in reception sensitivity with a relatively simple configuration.
The present invention provides a holographic radar having a plurality of reception antennas for receiving reflection waves of a radio wave transmitted from transmission antennas, the connection of the plurality of reception antennas to a receiver being switched in sequence to thereby acquire radar signals in a time-shared manner, wherein a plurality of transmission antennas are provided and switched in sequence for the transmission of the radio wave.
According to the present invention, the number of reception antennas can be reduced by switching the plurality of transmission antennas. It is thus possible to reduce the number of switches for switching the reception antennas and to enhance the reception sensitivity. Furthermore, the reduction in the number of the antennas and switches leads to lowered production costs of the device.
REFERENCES:
patent: 4924235 (1990-05-01), Fujisaka et al.
patent: 5455590 (1995-10-01), Collins et al.
patent: 5583511 (1996-12-01), Hulderman
patent: 5859609 (1999-01-01), Sheen et al.
patent: 63-256879 (1988-10-01), None
patent: 07-210073 (1995-08-01), None
Kuniyoshi Yamane, et al. “A Holographic Imaging Method for automotive Radar”, Electronic Information Communication Academy Institute Memoir B-II, vol. J81-B-II, No. 8, Aug. 1998, pp. 805-813 (with English Abstract).
Asano Yoshikazu
Harada Tomohisa
Kabushiki Kaisha Toyota Chuo Kenkyusho
Lobo Ian J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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