Monitor

A monitoring apparatus of the present application includes: a transmission antenna section that transmits a radio wave of single beam having a wide angle or alternatively a radio wave having a narrower (angular) range in a plurality of beam directions. A receiving antenna section receives the radio wave transmitted by the transmission antenna section and then reflected by a target. A beam switching instrument performs a switching operation such that power is fed to either a first power feed section or a second power feed section, which thereby controls the beam directions of the radio waves to monitor a specified area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase application of PCT International Patent Application No. PCT/JP2005/16952, filed Sep. 14, 2005, claiming the benefit of priority of Japanese Patent Application Nos. 2004-268615 filed Sep. 15, 2004 and 2005-056484 filed Mar. 1, 2005, all of which are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a monitoring apparatus for sending out a radio wave, then receiving a reflected reflection signal, and thereby detecting a material body, a person, and the like in the surroundings.

BACKGROUND ART

In an example of a prior art vehicle surroundings monitoring apparatus for monitoring the surroundings of a vehicle, an ultrasonic sensor is attached at a corner of the front or the rear of the vehicle so that a surrounding obstacle is detected or its distance is measured. Then, in case of danger of contact, the situation is reported to the driver (see, for example, Japanese Patent Publication No. 3232162).

FIG. 27is a plan view showing a prior art vehicle surroundings monitoring apparatus described in Japanese Patent Publication No. 3232162. InFIG. 27, ultrasonic detectors3FR,3FL,3RR,3RL,3BR, and3BLare installed at the corners of the front or the rear of a vehicle body1. Ultrasonic waves are transmitted in such timing that mutual interference is avoided. By virtue of this, a surrounding obstacle is detected, so that the distance to the obstacle is measured. Then, when the distance to the obstacle is reduced so that danger is expected, an alarm signal is outputted from an alarm unit.

Here, such ultrasonic sensors have a short detection distance and poor environmental resistance such as erroneous detection caused when raindrops are attached to the sensors. Thus, radar sensors employing radio waves also have begun to be adopted widely in vehicle surroundings monitoring apparatuses. A prior art radar apparatus for vehicle is installed in the front of a vehicle and used for measuring the car-to-car distance and the relative velocity to a vehicle located ahead by using an extremely narrow beam of 10 degrees or less, and thereby controlling the own vehicle. Thus, the monitoring area is limited to an extremely narrow and elongate region in front of the vehicle.

DISCLOSURE OF THE INVENTION

Nevertheless, since the detection (angular) range of a radar sensor is determined by the directivity of an antenna, a plurality of sensors need be arranged in order to cover a wider (angular) range. This causes the problem of an increase in the overall system cost.

FIG. 28shows the attachment positions of radar sensors and their monitoring areas in a case that the radar sensor are used for monitoring the rearward direction of a vehicle without a gap. As such, a large number of radar sensors 2801-2806 are necessary.

Another method of covering a wide (angular) range is scanning. Nevertheless, this method requires mechanical rotation, and hence causes an extremely large cost increase. Yet another method is a phased array antenna in which the antenna lobe is rotated electronically. Nevertheless, in order to achieve a sharp convergence, a large number of phase-controlled active transmission/receiving elements are necessary. This causes comparatively high implementation cost.

That is, the monitoring of a wide (angular) range of vehicle surroundings by using radar sensors has the problem of extremely high cost.

The present invention solves the above-mentioned problem in the prior art. An object of the invention is to provide a monitoring apparatus capable of monitoring a wide (angular) range of vehicle surroundings or the like by using a small number of radar sensors or the like.

A first aspect of the present invention is a monitoring apparatus for being installed on a vehicle, sending out a radio wave, then receiving a radio wave generated by reflection of the radio wave, and thereby detecting a target including a material body and/or a human body, said apparatus comprising:

a transmission antenna section for sending out a radio wave having directivity of a predetermined (angular) range, or alternatively for sending out in different beam directions a radio wave having directivity of an (angular) range narrower than said predetermined (angular) range;

a receiving antenna section for receiving in each different beam direction the radio wave transmitted by said transmission antenna section and then reflected by said target;

a transmission section for transmitting to said transmission antenna section a signal to be sent out as said radio wave;

a receiving section to which the radio wave received by said receiving antenna section is transmitted as a signal from said receiving antenna section;

beam switching instrument which switches the beam direction sequentially when said receiving antenna section receives said radio wave in said each different beam direction, and which thereby controls a monitoring area; and a running information storing section for storing running state information of said vehicle, wherein

said receiving antenna section includes a first power feed section and a second power feed section, and wherein

on the basis of said running state information stored in said running information storing section, said beam switching instrument performs switching such that power is fed to either said first power feed section or said second power feed section.

A second aspect of the present invention is a monitoring apparatus according to the first aspect of the present invention, wherein when said transmission antenna section sends out said radio wave in different beam directions, said beam switching instrument which sequentially switches the beam direction of the transmitted radio wave and thereby controls the monitoring area.

A third aspect of the present invention is a monitoring apparatus according to the second aspect of the present invention, comprising transmission and reception switching instrument which switches a signal transmitted from said transmission section and a signal transmitted to said receiving section, wherein

said receiving antenna section serves also as said transmission antenna section, while transmission or reception of the radio wave is switched by said transmission and reception switching instrument.

A fifth aspect of the present invention is a monitoring apparatus according to the first aspect of the present invention, wherein

said receiving antenna section includes a reflector plate and a rectangular antenna element parallel to said reflector plate, and wherein

said rectangular antenna element retains said first power feed section and said second power feed section at a pair of two opposing corners thereof and detour elements at the other opposing corners.

A sixth aspect of the present invention is a monitoring apparatus according to the fifth aspect of the present invention, wherein said rectangular antenna element has a substantially square shape, while one side thereof has a length of substantially ⅓ of a wavelength of an operating frequency, and while each of said detour elements has a length of substantially ¼ of the wavelength of the operating frequency.

A seventh aspect of the present invention is a monitoring apparatus according to the fifth aspect of the present invention, wherein

said rectangular antenna element is a slot loop antenna having a slot section where a conductor on a conductor face of a dielectric substrate is removed in a rectangular shape, while said detour elements are detour slot parts located at a pair of opposing corners of said slot section, and wherein

each of the other pair of opposing corners of said slot section receives power fed by electromagnetic coupling from an end of one of microstrip lines formed on a surface opposite to the conductor face of said dielectric substrate, while the other end of one of said microstrip lines is said first power feed section, and while the other end of the other of said microstrip lines is said second power feed section.

An eighth aspect of the present invention is a monitoring apparatus according to the seventh aspect of the present invention, wherein the surface opposite to the conductor face of said dielectric substrate faces said reflector plate.

A ninth aspect of the present invention is a monitoring apparatus according to the first aspect of the present invention, further comprising a first target position determination section for determining a distance to said target on the basis of the signal transmitted to said receiving section, then determining a direction toward said target on the basis of a value obtained when a difference of amplitudes of two signals among a plurality of signals corresponding to a plurality of radio waves received from said different beam directions is normalized by a sum of the amplitudes of said two signals, and thereby determining a position of said target on the basis of said distance and said direction toward said target.

A tenth aspect of the present invention is a monitoring apparatus according to the first aspect of the present invention, wherein

at least said transmission antenna section and said receiving antenna section are provided in a front central part and/or a rear central part of said vehicle, and wherein

among said different beam directions, one is directed leftward of said vehicle, while another one is directed rightward of said vehicle.

An eleventh aspect of the present invention is a monitoring apparatus according to the first aspect of the present invention, wherein

at least said transmission antenna section and said receiving antenna section are provided within a side mirror of said vehicle, and wherein

among said different beam directions, one is directed forward of said vehicle, while another one is directed rearward of said vehicle.

A twelfth aspect of the present invention is a surroundings monitoring system wherein a plurality of said monitoring apparatuses according to the first aspect of the present invention are provided and aligned so that a larger region becomes a monitoring area in comparison with the case that said monitoring apparatus is employed in stand-alone.

A thirteenth aspect of the present invention is a surroundings monitoring system according to the twelfth aspect of the present invention, wherein a timing that all of a plurality of said monitoring apparatuses monitor the same predetermined side and a timing that all of a plurality of said monitoring apparatuses monitor the side opposite to said same predetermined side are switched and controlled in time sharing.

A fourteenth aspect of the present invention is a surroundings monitoring system according to the twelfth aspect of the present invention, comprising a second target position determination section of determining a position of a target on the basis of a distance from one monitoring apparatus, among a plurality of said monitoring apparatuses having been aligned, to said target determined by said one monitoring apparatus and a distance from another monitoring apparatus to said target determined by said another monitoring apparatus arranged distant from said one monitoring apparatus.

A fifteenth aspect of the present invention is a monitoring control method in a vehicle-installed monitoring apparatus of sending out a radio wave, then receiving a radio wave generated by reflection of the radio wave, and thereby detecting a target including a material body and/or a human body, wherein

said method includes the step of determining which monitoring area among a plurality of monitoring areas that can be monitored when a beam direction of the radio wave is switched should be activated at which timing on the basis of running state information of said vehicle, and of thereby controlling the monitoring area.

The present invention provides a monitoring apparatus capable of monitoring a wide (angular) range of vehicle surroundings or the like by using a small number of radar sensors or the like.

DESCRIPTION OF REFERENCE NUMERALS

d1Distance between radiating element and reflecting element

d2Distance between radiating element and waveguide element and distance between waveguide elements

101Timing control section

1970Central control arithmetic operation section

1971Central timing control section

1972Central processing section

1980Running status information storing section

1981Vehicle speed sensor

100,1100,1700,1710,1800,1810,1820,1830,1910,1920,1930Vehicle surroundings monitoring apparatus

2201Timing control section

2211Timing control section

2212Power feed changing switch

2513Receiving antenna section

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1is a block configuration diagram of a vehicle surroundings monitoring apparatus according to Embodiment 1 of the present invention.

InFIG. 1, a vehicle surroundings monitoring apparatus100comprises: a timing control section101; a transmission section102of transmitting a radio wave; a transmission antenna103having a plurality of beams; a receiving antenna104; beam direction specifying instrument105which switches the beam direction of the antenna; a receiving section106of receiving a reflection signal; and a processing section107. The transmission section102, the beam direction specifying instrument105, the receiving section106, and the processing section107are controlled on the basis of timing signals from the timing control section101. Here, the vehicle surroundings monitoring apparatus100is an example of the monitoring apparatus of the present invention. The transmission antenna103and the receiving antenna104are examples of the transmission antenna section and the receiving antenna section of the present invention, respectively. Further, the beam direction specifying instrument105is an example of the beam switching instrument of the present invention.

The transmission antenna103includes a first antenna110and a second antenna120each provided with one feed element111and a plurality of non-feed elements. The first antenna110and the second antenna120share the feed element111.

The receiving antenna104has the same configuration as the transmission antenna103, and includes a first antenna130and a second antenna140. The first antenna130and the second antenna140share the feed element111.

Next, the operation of the vehicle surroundings monitoring apparatus100of the present Embodiment 1 is described below with reference toFIG. 1.

Each non-feed element112includes an open-short switch113. Then, the beam direction specifying instrument105performs control such that in the transmission antenna103, when the open-short switches113of all the non-feed elements112owned by the first antenna110are open, the open-short switches of all the non-feed elements112owned by the second antenna120should be short-circuited, and that when the open-short switches of all the non-feed elements112owned by the first antenna110are short-circuited, the open-short switches of all the non-feed elements112owned by the second antenna120should be open. The beam direction specifying instrument105performs similar control also in the receiving antenna104.

On the basis of timing signals from the timing control section101, the beam direction specifying instrument105controls the open-short switch113of each non-feed element112such that a beam should be formed in a predetermined direction.

Similarly, on the basis of a timing signal, the signal transmitted from the transmission section102is sent out from the transmission antenna103. When a detection target is present in the surroundings, the sent-out signal is reflected by the detection target. Here, the detection target indicates a vehicle, a material body, or a human body located in the surroundings of a vehicle in which this vehicle surroundings monitoring apparatus100is installed.

The reflection signal from such a detection target is transmitted to the receiving section106through the receiving antenna104and then processed in the processing section107, so that information on the presence or absence of a detection target, the distance to the detection target, and the speed of the detection target is obtained. Then, output instrument108connected to the vehicle surroundings monitoring apparatus100outputs such information in the form of display, voice output, or the like.

Next, the configuration of the transmission antenna103and the receiving antenna104of the vehicle surroundings monitoring apparatus100of the present Embodiment 1 is described below for the case of a configuration based on a Yagi-Uda array antenna.

FIG. 2is a configuration diagram of an antenna employing a configuration based on a Yagi-Uda array antenna.FIG. 2(a) is a perspective view, whileFIG. 2(b) is a top plan view. The following description is given for the case that the operating frequency of the antenna is 24 GHz. Further, coordinate axes are defined as shown inFIG. 2, for convenience of description.

The antenna shown inFIG. 2includes: a first Yagi-Uda array antenna composed of a radiating element201, a reflecting element202, and a plurality of waveguide elements203; and a second Yagi-Uda array antenna composed of a radiating element201, a reflecting element212, and a plurality of waveguide elements213. As shown inFIG. 2, these two Yagi-Uda array antennas share the radiating element201, and are arranged around the radiating element201on the Y-axis, in opposite and tilted directions with respect to the Y-axis. As for the tilt relative to the Y-axis, when the X-axis is adopted as the reference, the first Yagi-Uda array antenna is arranged along a direction tilted from the X-axis direction by an angle φ=α. Further, the second Yagi-Uda array antenna is arranged along a direction tilted from the X-axis direction by an angle φ=180−α.

The radiating element201is a half wavelength dipole antenna having a length of 6 mm. Each of the reflecting elements202and212is a line-shaped element having a length of 6 mm arranged at a position of distance d1from the radiating element201. A plurality of the waveguide elements203and213are arranged at a position of distance d2from the radiating element201. These intervals are d2each. At that time, the length of the waveguide elements203and213is set to be 5 mm each.

As shown inFIG. 2(b), the reflecting element202and a plurality of the waveguide elements203are arranged on a straight line in parallel to the radiating element201, and thereby constitute the first Yagi-Uda array antenna. Similarly, the reflecting element212and a plurality of the waveguide elements213are arranged on a straight line in parallel to the radiating element201, and thereby constitute the second Yagi-Uda array antenna. Here, the direction of the first Yagi-Uda array antenna in which the reflecting element202, the radiating element201, and a plurality of the waveguide elements203are arranged on a straight line is an example of the predetermined direction of the present invention. Further, the direction of the second Yagi-Uda array antenna in which the reflecting element212, the radiating element201, and a plurality of the waveguide elements213are arranged on a straight line is an example of the direction different from the predetermined direction of the present invention.

Each of the reflecting elements202and212and the waveguide elements203and213is provided with a switching element using a PIN diode or the like in the center of the element. Thus, when a forward bias is applied to the PIN diode so that the switching element is turned ON, each of these reflecting elements and waveguide elements operates as a reflecting element or a waveguide element. When a reverse bias is applied to the PIN diode so that the switching element is turned OFF, a state is established that each reflecting element or waveguide element is separated at the center, so that the element does not operate as a reflecting element or a waveguide element. Here, these switching elements correspond to the open-short switches113shown inFIG. 1.

The correspondence relation of the directivity of the first and the second antennas that constitute the transmission antenna103and the receiving antenna104shown inFIG. 1with the direction of the above-mentioned Yagi-Uda array antenna is as follows. That is, the first antenna110of the transmission antenna103and the first antenna130of the receiving antenna104have the same directivity (seeFIGS. 3(a) and3(b)), and each of these is constructed from the first Yagi-Uda array antenna shown inFIGS. 2(a) and2(b). Further, the second antenna120of the transmission antenna103and the second antenna140of the receiving antenna104have the same directivity (seeFIGS. 4(a) and4(b)), and each of these is constructed from the second Yagi-Uda array antenna shown inFIGS. 2(a) and2(b).

Next, the operation is described below for the antenna having the configuration shown inFIG. 2.

Switching control is performed such that when the switching elements mounted in the element centers of the reflecting element202and the waveguide elements203constituting the first Yagi-Uda array antenna are turned ON, the switching elements mounted in the element centers of the reflecting element212and the waveguide elements213constituting the second Yagi-Uda array antenna should be turned OFF. Similarly, switching control is performed such that when the switching elements mounted in the element centers of the reflecting element212and the waveguide elements213constituting the second Yagi-Uda array antenna are turned ON, the switching elements mounted in the element centers of the reflecting element202and the waveguide elements203constituting the first Yagi-Uda array antenna should be turned OFF. When the states of the switching elements are switched as described here, the first Yagi-Uda array antenna and the second Yagi-Uda array antenna can be switched with each other. Thus, the direction of the main beam can be switched. Here, an example of the “different beam directions” of the present invention is that the directions of main beams are different when attention is focused on the directions of main beams.

FIG. 3is a diagram showing directivity in a case that the first Yagi-Uda array antenna is solely operated that is located at φ=50 degrees which is tilted from the Y-axis direction by 40 degrees.FIG. 3(a) shows directivity in the horizontal (XY) plane.FIG. 3(b) shows directivity in the vertical plane at an azimuthal angle φ=50 degrees.

As a result of the switching control in the beam direction specifying instrument105described above, at the timing of ON (or OFF) of the first antenna110of the transmission antenna103, the first antenna130of the receiving antenna104goes ON (or OFF). After that, at the timing of ON (or OFF) of the second antenna120of the transmission antenna103, the second antenna140of the receiving antenna104goes ON (or OFF). As such, switches sequentially the antenna to be turned ON

InFIG. 3(a), directivity301indicates the directivity of the vertically polarized wave (Eθ) component. This shows that a main beam is obtained that is tilted in the direction of an azimuthal angle φ=50 degrees.

Further, inFIG. 3(b), similarly to the directivity301, directivity302indicates the directivity of the vertically polarized wave (Eθ) component. This shows that the main beam is directed in a horizontal direction.

FIG. 4is a diagram showing directivity in a case that the second Yagi-Uda array antenna is solely operated that is located at φ=130 degrees which is tilted from the Y-axis direction by 40 degrees toward the direction opposite to the first Yagi-Uda array antenna.FIG. 4(a) shows directivity in the horizontal (XY) plane.FIG. 4(b) shows directivity in the vertical plane at an azimuthal angle φ=+130 degrees.

InFIG. 4(a), directivity401indicates the directivity of the vertically polarized wave (Eθ) component. This shows that a main beam is obtained that is tilted in the direction of an azimuthal angle φ=130 degrees.

Further, inFIG. 4(b), similarly to the directivity401, directivity402indicates the directivity of the vertically polarized wave (Eθ) component. This shows that the main beam is directed in a horizontal direction.

FIG. 5is a diagram showing an example of arrangement and monitoring areas of a vehicle surroundings monitoring apparatus according to Embodiment 1 of the present invention.FIG. 5(a) is a diagram showing the arrangement of a vehicle surroundings monitoring apparatus.FIG. 5(b) is a diagram showing its monitoring areas viewed from the above.

InFIG. 5(a), a vehicle surroundings monitoring apparatus1100is installed near the center of the front part of a vehicle, for example, inside a bumper composed of resin and hence transmitting radio waves, in such a manner that the Z-axis inFIG. 2should be perpendicular to the ground surface and that the Y-axis should be in the forward direction of the vehicle. Here, the vehicle surroundings monitoring apparatus1100is the same as the vehicle surroundings monitoring apparatus100shown inFIG. 1.

Further, the beam of the antenna is tilted as largely as possible relative to the Y-axis direction (φ=90 degrees), that is, tilted into a state that the azimuthal angle φ should approach 0 or 180 degrees as much as possible. By virtue of this, two monitoring areas consisting of a monitoring area1101and a monitoring area1102as shown inFIG. 5(b) can be monitored using one vehicle surroundings monitoring apparatus1100. This permits monitoring of short-distance regions in the right and left directions of the vehicle when the vehicle runs through a blind crossing, a blind T junction, or the like.

According to this configuration, using merely one vehicle surroundings monitoring apparatus, the (necessity of) entering of a vehicle into the crossing, the T junction, or the like is minimized, while the check of approaching vehicles, bicycles, and passersby is assisted.

In the above-mentioned description, the vehicle surroundings monitoring apparatus has been arranged at the position shown inFIG. 5. However, the entire configuration of the vehicle surroundings monitoring apparatus100shown inFIG. 1need not be arranged at the position shown inFIG. 5. It is sufficient that only the transmission antenna103and the receiving antenna104are arranged at the position ofFIG. 5. The other components of the vehicle surroundings monitoring apparatus100may be arranged at other positions of the vehicle.

Further, in the configuration of the vehicle surroundings monitoring apparatus100shown inFIG. 1of the present Embodiment 1, the beam of the transmission antenna103has been switched similarly to the case of the receiving antenna104. However, the transmitting side may be constructed from an arbitrary antenna such as a patch antenna.

FIG. 6is a configuration diagram of a vehicle surroundings monitoring apparatus1200in a case that the transmitting side is constructed from a patch antenna. The only difference is that the part of the transmission antenna103of the vehicle surroundings monitoring apparatus100shown inFIG. 1is replaced by a transmission antenna1203. The transmission antenna1203is a patch antenna having a wide directivity. Here, like components toFIG. 1are designated by like numerals.

The radio wave sent out from the transmission antenna1203shown inFIG. 6is an example of the “radio wave having directivity of a predetermined (angular) range” of the present invention. The radio wave in a plurality of directions sent out from the transmission antenna103of the vehicle surroundings monitoring apparatus100shown inFIG. 1is an example of the “radio wave having directivity of an (angular) range narrower than said predetermined (angular) range” and the radio wave “sent out in different beam directions”.

InFIG. 6, the signal transmission (angular) range of the transmission antenna1203is an (angular) range including both of the region monitored using the beam direction of the first antenna130and the region monitored using the beam direction of the second antenna140. As such, it is sufficient that the antenna on the transmitting side is an antenna capable of sending out a radio wave over an (angular) range including a plurality of the monitoring areas of the antenna on the receiving side.

Further, in the configuration of the vehicle surroundings monitoring apparatus100shown inFIG. 1, the transmission antenna103and the receiving antenna104have been provided separately. However, an antenna may be shared for transmission and reception, while transmission and reception of signals may be switched.

FIG. 7is a configuration diagram of a vehicle surroundings monitoring apparatus1450in a case that the transmission antenna and the receiving antenna are constructed in the form of a shared antenna. The difference from the vehicle surroundings monitoring apparatus100shown inFIG. 1is that a transmission and reception changing switch1400is provided so that the transmission antenna and the receiving antenna are constructed in the form of a shared antenna. Here, like components toFIG. 1are designated by like numerals.

The transmission and receiving antenna1404shown inFIG. 7has the same configuration as the receiving antenna104shown inFIG. 1. The transmission and reception changing switch1400performs control such as to switch the connection of the feed element ill in correspondence to the timing of transmission and reception of the radio wave through the transmission and receiving antenna1404.

The transmission and reception changing switch1400performs control such that when a radio wave is to be sent out from the transmission and receiving antenna1404, the transmission section102should be connected to the feed element111, and that when a radio wave is to be received by the transmission and receiving antenna1404, the receiving section106should be connected to the feed element111. As such, the transmission and receiving antenna1404is shared in transmission and reception. Here, the transmission and reception changing switch1400is an example of the transmission and reception switching instrument of the present invention.

Further, in the present Embodiment 1, a dipole antenna has been employed for each of the elements constituting the transmission antenna and the receiving antenna. However, the invention is not limited to this.

Further, in the present Embodiment 1, description has been given for the case of a front monitoring apparatus in which a vehicle surroundings monitoring apparatus is arranged in the front part of a vehicle. However, a rear monitoring apparatus may be implemented in which a vehicle surroundings monitoring apparatus is arranged in the rear part of a vehicle.

In addition, an array configuration may be employed in which a plurality of antennas (of the vehicle surroundings monitoring apparatus) of the present Embodiment 1 are arranged in the Z-direction of the antenna shown inFIG. 2while power is fed respectively to a plurality of the antennas, so that a narrow beam configuration may be realized in the Z-axis direction. By virtue of this, the monitoring area may be of long distance. In this case, when the apparatus is installed in a car, the influence of reflection from the ground surface can also be reduced.

FIG. 8is a block configuration diagram of a vehicle surroundings monitoring apparatus according to Embodiment 2 of the present invention.

The vehicle surroundings monitoring apparatus500of the present Embodiment 2 has a configuration different from that of the vehicle surroundings monitoring apparatus100of Embodiment 1 shown inFIG. 1in the point that each of the transmission antenna and the receiving antenna has a plurality of power feed ports while power feed to the power feed ports is switched so that a plurality of beam directions are realized. Here, the vehicle surroundings monitoring apparatus500is an example of the monitoring apparatus of the present invention.

A timing control section501, a transmission section502, a receiving section506, a processing section507, and an output instrument508shown inFIG. 8have respectively the same function as the timing control section101, the transmission section102, the receiving section106, the processing section107, and the output instrument108shown inFIG. 1.

The transmission antenna section503includes: a transmission antenna element511; and two power feed sections consisting of a first power feed section512and a second power feed section513of feeding power to the transmission antenna element511. Similarly, the transmission antenna section504includes: a transmission antenna element521; and two power feed sections consisting of a first power feed section522and a second power feed section523of feeding power to the transmission antenna element521.

On the basis of timing signals from the timing control section501, the beam direction specifying instrument505controls the power feed changing switches510and520, so that the case that power is fed to the first power feed sections512and522and the case that power is fed to the second power feed sections513and523are switched with each other such that a beam should be formed in a predetermined direction. Here, the beam direction specifying instrument505is an example of the beam switching instrument of the present invention.

Next, the configuration of the transmission antenna503and the receiving antenna504of the vehicle surroundings monitoring apparatus500of the present Embodiment 2 is described below for the case of a configuration based on a Yagi-Uda array antenna.

FIG. 9is a configuration diagram of an antenna employing a configuration based on a Yagi-Uda array antenna.FIG. 9(a) is a perspective view, whileFIG. 9(b) is a top plan view. The following description is given for the case that the operating frequency of the antenna is 24 GHz. Further, coordinate axes are defined as shown inFIG. 9, for convenience of description.

The antenna shown inFIG. 9includes: a first Yagi-Uda array antenna composed of a radiating element601, a reflecting element602, and a plurality of waveguide elements603and604; and a second Yagi-Uda array antenna composed of a radiating element611, a reflecting element612, and a plurality of waveguide elements613and604. These two Yagi-Uda array antennas share the radiating element604at the extreme end, and are arranged around the radiating element604on the Y-axis, in opposite and tilted directions with respect to the Y-axis. As for the tilt relative to the Y-axis, when the X-axis is adopted as the reference, the first Yagi-Uda array antenna is arranged along a direction tilted from the X-axis direction by an angle φ=α′. Further, the second Yagi-Uda array antenna is arranged along a direction tilted from the X-axis direction by an angle φ=180−α′.

The radiating elements601and611are half wavelength dipole antennas having a length of 6 mm. The reflecting elements602and612are line-shaped elements having a length of 6 mm arranged at a position of distance d1from the radiating elements601and611, respectively. A plurality of the waveguide elements603,604, and613are arranged at a position of distance d2from the radiating elements601and611. These intervals are d2each. At that time, the length of the waveguide elements603,604, and613is set to be 5 mm each.

As shown inFIG. 9(b), the reflecting element602and the waveguide elements603and604are arranged on a straight line in parallel to the radiating element601, and thereby constitute the first Yagi-Uda array antenna. Similarly, the reflecting element612and the waveguide elements613and604are arranged on a straight line in parallel to the radiating element611, and thereby constitute the second Yagi-Uda array antenna. Here, the direction of the first Yagi-Uda array antenna in which the reflecting element602, the radiating element601, and the waveguide elements603and604are arranged on a straight line is an example of the predetermined direction of the present invention. Further, the direction of the second Yagi-Uda array antenna in which the reflecting element612, the radiating element611, and the waveguide elements613and604are arranged on a straight line is an example of the direction different from the predetermined direction of the present invention.

A power feed section is provided in the central part of each of the radiating elements601and611. The power feed section of the radiating element601corresponds to the first power feed section512or522shown inFIG. 8. The power feed section of the radiating element611corresponds to the second power feed section513or523shown inFIG. 8.

Next, the operation is described below for the antenna having the configuration shown inFIG. 9.

Switching operation is performed such that when power is fed to the radiating element601constituting the first Yagi-Uda array antenna, the radiating element611constituting the second Yagi-Uda array antenna should be open. Similarly, switching operation is performed such that when power is fed to the radiating element611constituting the second Yagi-Uda array antenna, the radiating element601constituting the first Yagi-Uda array antenna should be open.

When the radiating element to be fed is switched as described here, the first Yagi-Uda array antenna and the second Yagi-Uda array antenna can be switched with each other. Thus, the direction of the main beam can be switched.

FIG. 10is a diagram showing directivity in a case that the first Yagi-Uda array antenna is solely operated that is located at φ=50 degrees which is tilted from the Y-axis direction by 40 degrees.FIG. 10(a) shows directivity in the horizontal (XY) plane.FIG. 10(b) shows directivity in the vertical plane at an azimuthal angle φ=50 degrees.

InFIG. 10(a), directivity701indicates the directivity of the vertically polarized wave (Eθ) component. This shows that a main beam is obtained that is tilted in the direction of an azimuthal angle φ=50 degrees.

Further, inFIG. 10(b), similarly to the directivity701, directivity702indicates the directivity of the vertically polarized wave (Eθ) component. This shows that the main beam is directed in a horizontal direction.

FIG. 11is a diagram showing directivity in a case that the second Yagi-Uda array antenna is solely operated that is located at φ=130 degrees which is tilted from the Y-axis direction by 40 degrees toward the direction opposite to the first Yagi-Uda array antenna.FIG. 11(a) shows directivity in the horizontal (XY) plane.FIG. 11(b) shows directivity in the vertical plane at an azimuthal angle φ=130 degrees.

InFIG. 11(a), directivity801indicates the directivity of the vertically polarized wave (Eθ) component. This shows that a main beam is obtained that is tilted in the direction of an azimuthal angle φ=130 degrees.

Further, inFIG. 11(b), similarly to the directivity801, directivity802indicates the directivity of the vertically polarized wave (Eθ) component. This shows that the main beam is directed in a horizontal direction.

Next, the configuration of the transmission antenna503and the receiving antenna504of the vehicle surroundings monitoring apparatus500of the present Embodiment 2 is described below for the case that an antenna is employed that has a configuration different from the above-mentioned Yagi-Uda array antenna.

FIG. 12is a detailed example of another configuration of the antenna section.FIG. 12(a) is a top view of this antenna section, whileFIG. 12(b) is a side view. This antenna is described in detail in “The Institute of Electronics, Information and Communication Engineers Technical Report (Shingaku Gihou), A-P2003-157(2003-11)”.

As shown inFIG. 12(a), this antenna element900includes: a loop element901of square shape having a side length of approximately ⅓ wavelength; detour elements902of folded shape having a length of approximately ¼ wavelength, connected to a set of opposing vertices of the loop element901; and a first power feed port903and a second power feed port904provided at the other two vertices. Here, the antenna element900is an example of the rectangular antenna element of the present invention.

Further, as shown inFIG. 12(b), a reflector plate905(for example, having a side length of approximately2wavelengths) is arranged at a position of a predetermined distance h from the antenna element900in parallel to the antenna element900. For example, when the operating frequency of the antenna system is set to be 24 GHz while the element is formed on a substrate having a dielectric constant of 2.26, the side length of the loop element901is set to be approximately 3.3 mm. Further, the detour element902has a folded shape generated by folding an approximately 2.5-mm length, while angle β is set to be approximately 90 degrees.

Next, the operation of the antenna section shown inFIG. 12is described below. InFIG. 12(a), when one power feed port (for example, the first power feed port903) is excited while the other power feed port (for example, the second power feed port904) is short-circuited, the current amplitude reaches a peak at each port. At that time, a current phase difference arises between the peak points. Thus, similarly to the case ofFIG. 10, the radiating pattern of this antenna becomes a main beam tilted in the −X direction by virtue of the phase difference between the peak points.

Here, inFIG. 12(a), the detour elements902have been arranged in a manner protruding to the outside of the loop in order to reduce mutual coupling with the loop element901. However, the detour elements902may be arranged inward of the loop.

FIG. 13shows a detailed example of yet another configuration of the transmission antenna section503and the receiving antenna section504of the vehicle surroundings monitoring apparatus500of the present Embodiment 2, and illustrates a slot configuration in a detour-element installed slot loop antenna.

FIG. 13(a) is a general configuration diagram of a detour-element installed slot loop antenna.FIG. 13(b) is a top view of a dielectric substrate viewed from the +Z axis side.FIG. 13(c) is a bottom view of a dielectric substrate viewed from the −Z axis side.

The slot element of this antenna is fabricated by cutting a copper foil on the +Z surface side of a dielectric substrate1007. Then, power is fed by electromagnetic coupling with microstrip lines (MSLs)1005formed on the −Z surface side. Here, this slot element is an example of the slot loop antenna of the present invention.

The black slot portion shown inFIG. 13is a hole where the copper foil is cut off. That is, the gray portions inside and outside the black slot portion on the ground surface1006side shown inFIG. 13(b) are conductor portions where the copper foil is remained. Then, the black slot part is a portion where the copper foil is cut off. On the ground surface1006side, the gray portion inside the slot is separated from the portion outside the slot by the slot. Thus, as shown inFIG. 13(c), on the bottom face side of the dielectric substrate1007, the portion inside the slot is connected to the conductor portion outside the slot through short-circuiting lines1009connected to short-circuiting pins1008in the conductor portion.

As shown inFIG. 13(a), the slot part has such a shape that detour slots1002of folded shape connected to a set of opposing vertices of the loop slot1001are connected to the loop slot1001of square shape. Then, a first power feed port1003and a second power feed port1004are provided at the ends of the MSLs1005opposite to the side of power feed to the slot.

The MSLs1005are open at a position of length L1from the coupling part with the loop slot1001. When the length L1is adjusted, impedance matching is achieved. Further, in order that the power feed port to be excited should be switched so that the direction of the main beam should be controlled similarly to the case of the line-shaped elements shown inFIG. 9, the coupling part between the loop slot1001and the MSL1005on the unexcited power feed port side need be open in the slot configuration shown inFIG. 13. For the purpose of this, the MSL1005may be power-fed at a position where the length L2from the coupling part is an integer multiple of ¼ wavelength.

Here, inFIG. 13, the detour slots1002have been arranged in a manner protruding to the outside of the loop in order to reduce mutual coupling with the loop slot1001. However, the detour slots1002may be arranged inward of the loop.

Here, in the configuration of the vehicle surroundings monitoring apparatus500shown inFIG. 8of the present Embodiment 2, the beam of the transmission antenna503has been switched similarly to the case of the receiving antenna504. However, the transmitting side may be constructed from an arbitrary antenna such as a patch antenna.

FIG. 14is a configuration diagram of a vehicle surroundings monitoring apparatus1300in a case that the transmitting side is constructed from a patch antenna. The only difference is that the part of the transmission antenna503of the vehicle surroundings monitoring apparatus500shown inFIG. 8is replaced by a transmission antenna1303. The transmission antenna1303is a patch antenna having a wide directivity. Here, like components toFIG. 8are designated by like numerals.

Further, in the configuration of the vehicle surroundings monitoring apparatus500shown inFIG. 8, the transmission antenna503and the receiving antenna504have been provided separately. However, an antenna may be shared for transmission and reception, while transmission and reception of signals may be switched.

FIG. 15is a configuration diagram of a vehicle surroundings monitoring apparatus1550in a case that the transmission antenna and the receiving antenna are constructed in the form of a shared antenna. The difference from the vehicle surroundings monitoring apparatus500shown inFIG. 8is that a transmission and reception changing switch1500is provided so that the transmission antenna and the receiving antenna are constructed in the form of a shared antenna. Here, like components toFIG. 8are designated by like numerals.

The transmission and receiving antenna1504shown inFIG. 15has the same configuration as the receiving antenna504shown inFIG. 8. The transmission and reception changing switch1500performs control such as to switch the connection of a power feed changing switch1520in correspondence to the timing of transmission and reception of the radio wave through the transmission and receiving antenna1504.

The transmission and reception changing switch1500performs control such that when a radio wave is to be sent out from the transmission and receiving antenna1504, the transmission section502should be connected to the power feed changing switch1520, and that when a radio wave is to be received by the transmission and receiving antenna1504, the receiving section506should be connected to the power feed changing switch1520. As such, the transmission and receiving antenna1504is shared in transmission and reception.

Further, in the present Embodiment 2, each antenna element constituting the transmission antenna section and the receiving antenna section has been constructed from a dipole antenna or a loop antenna provided with detour elements. However, the invention is not limited to this.

Further, similarly to Embodiment 1, the vehicle surroundings monitoring apparatus of the present Embodiment 2 may be used as a vehicle surroundings monitoring apparatus shown inFIG. 5.

FIG. 16is a block configuration diagram of a vehicle surroundings monitoring apparatus1650according to Embodiment 3 of the present invention.

The vehicle surroundings monitoring apparatus1650of the present Embodiment 3 differs from the vehicle surroundings monitoring apparatus500of Embodiment 2 shown inFIG. 8in the point that running status information storing section1600of storing running state information of a vehicle is provided. InFIG. 16, like components toFIG. 8are designated by like numerals, and hence description is omitted. Here, the running status information storing section1600is an example of the running information storing section of the present invention.

The running status information storing section1600stores running state information of a vehicle obtained from a vehicle speed sensor1601, a steering angle sensor1602, and a switch1603such as a turn indicator provided in the vehicle. Then, on the basis of the running status information stored in the running status information storing section1600, the beam direction specifying instrument1605determines the beam direction of the transmission antenna section503and the receiving antenna section504.

FIG. 17is a diagram showing an example of arrangement and monitoring areas of a vehicle surroundings monitoring apparatus1650of the present Embodiment 3.

InFIG. 17, the vehicle surroundings monitoring apparatus is installed in side faces of the vehicle, more specifically, for example, in door mirrors. The vehicle surroundings monitoring apparatuses1700and1710shown inFIG. 17are the same as the vehicle surroundings monitoring apparatus1650shown inFIG. 16. The beam of the transmission antenna section503and the receiving antenna section504of each of the vehicle surroundings monitoring apparatuses1700and1710is tilted into a state close to φ=90 degrees or −90 degrees.

Specifically, in the configuration shown inFIG. 9, the first Yagi-Uda array antenna is arranged around the waveguide element604in a manner tilted at an angle slightly less than −90 degrees from the Y-axis direction toward the +X direction. The second Yagi-Uda array antenna is arranged in a manner tilted at an angle slightly less than +90 degrees from the Y-axis direction toward the −X direction.

Further, in the configuration shown inFIG. 12, the distance of the antenna element900to the reflector plate905is set to be 0.4-0.5 wavelength (5.00-6.25 mm for the operating frequency of 24 GHz). In this antenna, when the distance of the antenna element to the reflector plate is changed, the beam direction can be changed.

Thus, the vehicle surroundings monitoring apparatus1700installed on the left-hand side of the vehicle monitors the left forward region1701and the left rear region1702. The vehicle surroundings monitoring apparatus1710installed on the right-hand side of the vehicle monitors the right front region1711and the right rear region1712.

According to this configuration, in the monitoring of vehicle side areas in which vehicle surroundings monitoring apparatuses can be installed merely at limited positions, two directions (forward and rearward directions) can be covered by one vehicle surroundings monitoring apparatus.

Here, the door mirror is an example of the side mirror of the present invention. The side mirror may be a fender mirror or the like other than a side mirror.

Next, a procedure is described below in which a plurality of monitoring areas are brought into a monitored state.

In general, power feed to the vehicle surroundings monitoring apparatus1700and the vehicle surroundings monitoring apparatus1710is switched alternately for every predetermined time, so that the monitoring area1701and the monitoring area1702are monitored alternately, or the monitoring area1711and the monitoring area1712are monitored alternately. However, depending on the running scene, the region to be monitored may be controlled by an input provided from the driver through a switch or the like.

For example, when the running is in a cruise control state at a low speed, control is performed such that the forward directions consisting of the monitoring area1701of the vehicle surroundings monitoring apparatus1700and the monitoring area1711of the vehicle surroundings monitoring apparatus1710should solely be brought into a monitored state. This permits immediate detection of a cutting-ahead vehicle, and hence realizes appropriate vehicle control.

On the contrary, when the running is based on the driver's intention and at a high speed, control is performed such that the rearward directions consisting of the monitoring area1702of the vehicle surroundings monitoring apparatus1700and the monitoring area1712of the vehicle surroundings monitoring apparatus1710should solely be brought into a monitored state. This permits immediate recognition of vehicles located in the rearward direction and vehicles present within dead angles. Then, when the situation is notified to the driver, wind-up at the time of right and left turns and collision at the time of lane change can be avoided. In particular, when the driver intends lane change toward right or left and displays the direction by means of a turn indicator, the rearward direction of that direction may solely be monitored. That is, when the lane change is rightward, the monitoring area1712may solely be activated, while when the lane change is leftward, the monitoring area1702may solely be activated.

Further, when the vehicle moves forward in a state that the steering wheel is turned left, the vehicle surroundings monitoring apparatus1700monitors the monitoring area1701and the monitoring area1702alternately, while the vehicle surroundings monitoring apparatus1710brings solely the monitoring area1711into a monitored state. In contrast, when the vehicle moves forward in a state that the steering wheel is turned right, the vehicle surroundings monitoring apparatus1710monitors the monitoring area1711and the monitoring area1712alternately, while the vehicle surroundings monitoring apparatus1700brings solely the monitoring area1701into a monitored state.

By virtue of this, the rearward part of the turn direction can be monitored, so that wind-up accidents can be prevented. Further, a forward part of the direction opposite to the direction of the driver's attention is monitored by the sensor. This reduces the possibility of collision caused by careless mistakes at the time of right and left turns.

According to this configuration, power feed to the vehicle surroundings monitoring apparatuses is controlled depending on the running state of the vehicle, so that the monitoring area can be switched. That is, the monitoring area can be set up in a direction of higher possibility of collision.

FIG. 18is a diagram showing another example of arrangement and monitoring areas of a vehicle surroundings monitoring apparatus of the present Embodiment 3.

InFIG. 18, vehicle surroundings monitoring apparatuses1800,1810,1820, and1830are installed at the corners of the vehicle. The vehicle surroundings monitoring apparatuses1800,1810,1820, and1830are the same as the vehicle surroundings monitoring apparatus1650shown inFIG. 16.

According to this arrangement, the vehicle surroundings monitoring apparatus1800installed on the left forward side of the vehicle monitors a monitoring area1801on the forward left side and a monitoring area1802on the left forward side. The vehicle surroundings monitoring apparatus1810installed on the right forward side of the vehicle monitors a monitoring area1811on the forward right side and a monitoring area1812on the right forward side. The vehicle surroundings monitoring apparatus1820installed on the right rearward side of the vehicle monitors a monitoring area1821on the rearward right side and a monitoring area1822on the right rearward side. The vehicle surroundings monitoring apparatus1830installed on the left rearward side of the vehicle monitors a monitoring area1831on the rearward left side and a monitoring area1832on the left rearward side.

When the vehicle runs at a high speed, power feed to each vehicle surroundings monitoring apparatuses is controlled such that the monitoring area1801, the monitoring area1811, the monitoring area1821, and the monitoring area1831should be monitored.

Further, when the steering wheel is turned, the monitoring area to be activated may be changed depending on the turn direction and the turn angle. For example, when the steering wheel is turned left slightly during forward running, the monitoring area1801is brought into a monitored state. When turned larger, the monitoring area1802is brought into a monitored state. In this case, the1822may simultaneously be brought into a monitored area. The operation is similar to other directions of turn.

When the entire surroundings is desired to be monitored and checked once as much as possible, like at the time of departure, the1801and the1812are simultaneously activated as monitoring areas. After that, the1802and the1811are simultaneously activated as monitoring areas.

This configuration permits efficient monitoring of a wide (angular) range of vehicle surroundings without mutual interference between the vehicle surroundings monitoring apparatuses.

Here, the vehicle surroundings monitoring apparatuses have been installed in the inside of side mirrors in the case ofFIG. 17and in the corner parts of the vehicle in the case ofFIG. 18. However, it is sufficient that at least the antenna parts of the vehicle surroundings monitoring apparatuses are arranged at these installation positions. That is, at least the transmission antenna section503and the receiving antenna section504shown inFIG. 16are installed at these installation positions. The other components of the vehicle surroundings monitoring apparatuses may be installed at other positions of the vehicle.

FIG. 19is a block configuration diagram of a vehicle surroundings monitoring system according to Embodiment 4 of the present invention. The configuration and the operation of a vehicle surroundings monitoring system of the present Embodiment 4 is described below with reference toFIG. 19. Here, the vehicle surroundings monitoring system shown inFIG. 19is an example of the surroundings monitoring system of the present invention.

InFIG. 19, the vehicle surroundings monitoring system of the present Embodiment 4 comprises: a plurality of vehicle surroundings monitoring apparatuses, for example, six vehicle surroundings monitoring apparatuses1910,1920, . . . ,1960; a central control arithmetic operation section1970; a running status information storing section1980of storing running state information of the vehicle obtained from a vehicle speed sensor1981, a steering angle sensor1982, and a switch1983such as a turn indicator; and a display section1990.

The vehicle surroundings monitoring apparatuses1910and1920, . . . ,1960are the same as the vehicle surroundings monitoring apparatus100ofFIG. 1, the vehicle surroundings monitoring apparatus1200ofFIG. 6, or the vehicle surroundings monitoring apparatus1450ofFIG. 7of Embodiment 1, or alternatively the vehicle surroundings monitoring apparatus500ofFIG. 8, the vehicle surroundings monitoring apparatus1300ofFIG. 14, or the vehicle surroundings monitoring apparatus1550ofFIG. 15of Embodiment 2. InFIG. 19, the same configuration as the vehicle surroundings monitoring apparatus500ofFIG. 8is adopted as an example.

The central control arithmetic operation section1970includes a central timing control section1971, a central processing section1972, and central beam direction specifying instrument1973.

The central timing control section1971is connected to the timing control sections (101,1401,501, or1501) of the vehicle surroundings monitoring apparatuses1910-1960. The central beam direction specifying instrument1973is connected to the beam direction specifying instrument (105or505). Further, in the configuration ofFIG. 7or15, the central beam direction specifying instrument1973is connected also to the transmission and reception changing switches (1400or1500). These sections and instruments operate on the basis of control signals from the central timing control section1971.

Further, the central processing section1972is connected to the receiving sections (106or506) or the processing sections (107or507) of the vehicle surroundings monitoring apparatuses1910-1960. Then, the receiving sections (106or506) or the processing sections (107or507) send received signals or results of processing of the received signals to the central processing section1972.

On the basis of information of detection of a target obtained from the receiving sections (106or506) or the processing sections (107or507) of the vehicle surroundings monitoring apparatuses1910-1960, the central processing section1972determines the degree of danger of collision with an obstacle, a person, or another vehicle in the surroundings. Then, the central processing section1972processes the data into a form easily recognizable to the driver, and then reports the result to the driver through the display section1990.

The central beam direction specifying instrument1973sends signals to the beam direction specifying instrument (105or505) of the vehicle surroundings monitoring apparatuses1910-1960, and thereby determines the beam direction.

FIG. 20is an example of arrangement and monitoring areas of the vehicle surroundings monitoring apparatuses1910-1960in the vehicle surroundings monitoring system of the present Embodiment 4.

InFIG. 20, the vehicle surroundings monitoring apparatuses1910,1920, and1930are installed, for example, in the inside of a bumper in the rear part of the vehicle. Further, although not shown inFIG. 20, the vehicle surroundings monitoring apparatuses1940,1950, and1960are similarly installed in a bumper in the front part of the vehicle. The following description is given for the vehicle surroundings monitoring apparatuses1910,1920, and1930installed in the rear part of the vehicle.

InFIG. 20, the vehicle surroundings monitoring apparatuses1910,1920, and1930are respectively installed at three places consisting of the left end, the center, and the right end of the rear part of the vehicle. Each of the vehicle surroundings monitoring apparatuses1910,1920, and1930covers two directions (for example, the vehicle surroundings monitoring apparatus1910covers monitoring areas2001and2002). Thus, six directions, that is, monitoring areas2001,2002,2011,2012,2021, and2022, are covered in total.

In this case, in order that the beam of the receiving antenna section should have a detecting region in the center of the vehicle surroundings monitoring apparatus, a null point should not arise here. Thus, large tilt is avoided relative to one beam. Specifically, the tilt angle of the main beam is set to be in the order of the half angle of the beam. By virtue of this, in contrast to the prior art in which vehicle surroundings monitoring apparatuses having the same beam width are employed so that six vehicle surroundings monitoring apparatuses are necessary as shown inFIG. 28, the same area can be covered using the three vehicle surroundings monitoring apparatuses1910,1920, and1930in the present Embodiment 4.

According to this configuration, a wide (angular) range of vehicle rearward direction can be monitored using a small number of vehicle surroundings monitoring apparatuses.

Next, a procedure is described below in which a plurality of monitoring areas are brought into a monitored state.

In general, when the monitoring areas are activated in time sharing, mutual interference is avoided. However, in case that interference has no influence or the influence is within an allowable (angular) range, when the number of regions simultaneously activated as monitoring areas is increased, the surroundings of the vehicle can be monitored more efficiently so that the system response speed is improved.

Specifically, the central beam direction specifying instrument1973controls the beam direction specifying instrument (105or505) of the vehicle surroundings monitoring apparatuses1910-1960at timings shown inFIG. 21, and thereby performs detection in the monitoring areas.FIG. 21is a diagram showing an example of time-dependent change of activation of the vehicle surroundings monitoring apparatuses1910-1930shown inFIG. 20, that is, an example of timing of transmitting pulses in the vehicle surroundings monitoring apparatuses1910-1930in an exemplary case that the vehicle surroundings monitoring apparatuses1910-1930are constructed from pulse radars of transmitting and receiving pulses.

As shown inFIG. 21, when the monitoring area2001is activated, the monitoring areas2011and2021are simultaneously activated. When the monitoring area2002is activated, the monitoring areas2012and2022are simultaneously activated. According to this operation, detection of an obstacle can be performed efficiently without mutual interfere.

According to this configuration, when power feed to the vehicle surroundings monitoring apparatuses is controlled so that the monitoring areas are switched, efficient monitoring of a wide (angular) range of vehicle surroundings is achieved without mutual interference between the vehicle surroundings monitoring apparatuses.

Here, the present Embodiment 4 has been described solely for the case that the vehicle surroundings monitoring apparatuses are installed in the rear part of the vehicle. However, similar control is performed also for the vehicle surroundings monitoring apparatuses installed in the front part of the vehicle. Further, the vehicle surroundings monitoring apparatuses may be installed only in the rear part or only in the front part of the vehicle.

Here, in the present Embodiment 4 shown inFIG. 19, each of the vehicle surroundings monitoring apparatuses1910-1960has been provided with the timing control section (101,1401,501, or1501). However, the central timing control section1971of the central control arithmetic operation section1970may serve also as these timing control sections.

Further, each of the vehicle surroundings monitoring apparatuses1910-1960has been provided with the processing section (107or507). However, the central processing section1972of the central control arithmetic operation section1970may serve also as these processing sections.

Further, the configuration of each of the vehicle surroundings monitoring apparatuses1910-1960shown inFIG. 19may be divided into a transmitting module and a receiving module.FIG. 22is a configuration diagram of a vehicle monitoring system of the present Embodiment 4 in which a transmitting module and a receiving module are provided in a separated manner.

The vehicle monitoring system ofFIG. 22comprises one transmitting module2200and a plurality of receiving modules2210-2260.

The transmitting module2200may have the configuration of the transmission section of the vehicle surroundings monitoring apparatus, for example, shown inFIGS. 1,6,7,8,14, and15. The receiving modules2210-2260may have the configuration of the receiving section of the vehicle surroundings monitoring apparatus, for example, shown inFIGS. 1,6,7,8,14, and15.

InFIG. 22, as an example, the configuration of the transmitting section of the vehicle surroundings monitoring apparatuses1300shown inFIG. 14is adopted in the transmitting module2200. Further, the configuration of the receiving section is adopted in the receiving modules2210-2260.

The transmission section2202, the transmission antenna2203, the power feed changing switch2212, and the receiving antenna section2213shown inFIG. 22have respectively the same configuration as the transmission section502, the transmission antenna1303, the power feed changing switch520, and the receiving antenna section504shown inFIG. 14. Further, the timing control section2201has the function of performing timing control on the transmitting side of the timing control section501ofFIG. 14. The timing control section2211has the function of performing timing control on the receiving side of the timing control section501ofFIG. 14.

Further, the display section2290, the running status information storing section2280, the vehicle speed sensor2281, the steering angle sensor2282, and the switch2283have respectively the same configuration as the display section1990, the running status information storing section1980, the vehicle speed sensor1981, the steering angle sensor1982, and the switch1983shown inFIG. 19. Furthermore, the central timing control section2271and the central processing section2272provided in the central control arithmetic operation section2270have respectively the same function as the central timing control section1971and the central processing section1972ofFIG. 19.

In this case, the receiving module2210-2260employs an antenna of switching the beam direction, and hence includes the power feed changing switch2212. In contrast, the transmitting module2200may employ an arbitrary antenna, for example, a patch antenna or the like.

Next, described below are a vehicle surroundings monitoring apparatus and a vehicle surroundings monitoring system of Embodiment 5 of the present invention.

The vehicle surroundings monitoring apparatus and the vehicle surroundings monitoring system of the present Embodiment 5 have the same configuration as the vehicle surroundings monitoring apparatus and the vehicle surroundings monitoring system described in Embodiments 1-4, but can more accurately detect the position of a detection target.

As described in Embodiments 1-4, since the beam direction of the receiving antenna is switched in the vehicle surroundings monitoring apparatus of these embodiments, monitoring areas in two different directions can be monitored using a single vehicle surroundings monitoring apparatus. Further, as described above, the angle between these two directions can be set up arbitrarily depending on the situation of surroundings and the application. In a case that the angle between these two directions are set up such that the two monitoring areas should partly overlap with each other, when a detection target is located in the overlap region of the two monitoring areas, the detection target is detected in both monitoring areas.

For example, in a case that the two beam directions of the receiving antenna are set up such that two monitoring areas2021and2022should partly overlap with each other as in the vehicle surroundings monitoring apparatus1930shown inFIG. 20, when a detection target is located in the overlap region of the monitoring areas, the direction in which the detection target is present can be detected as two separate directions. Here, the direction of presence of the detection target relative to the vehicle surroundings monitoring apparatus1930is an example of the direction toward a target of the present invention.

The vehicle surroundings monitoring apparatus of the present Embodiment 5 treats, as a set, two monitoring areas (for example, the monitoring areas2021and2022of the vehicle surroundings monitoring apparatus1930) that have approximately the same beam emission position and partly overlap with each other. By virtue of this, the angle of direction of presence of a detection target is calculated with finer angular resolution, so that accurate position of the detection target is recognized.

Next, a method of calculating the angle of direction of presence of a detection target in the vehicle surroundings monitoring apparatus of the present Embodiment 5 is described below with reference toFIG. 23.

In the following description, the vehicle surroundings monitoring apparatus100having the configuration ofFIG. 1is used as the vehicle surroundings monitoring apparatus1930shown inFIG. 20.

FIG. 23(a) shows the patterns of two switching beams that partly overlap with each other and correspond to the two monitoring areas2021and2022. The processing section107retains reflection signals from these two switching beams, and thereby generates a sum signal (Σ) and a difference signal (Δ) from their amplitudes.FIG. 23(b) shows the patterns of the sum signal (Σ) and the difference signal (Δ) generated from the two beam patterns ofFIG. 23(a) by the processing section107.

Then, the processing section107generates an angle error voltage ∈ generated by normalizing the difference signal (Δ) with the sum signal (Σ). That is, the angle error voltage ∈ is obtained by an arithmetic operation according to formula (1).
∈=Δ/Σ  (1)

FIG. 23(c) show the relation between the angle error voltage ∈ generated by normalizing the difference signal (Δ) with the sum signal (Σ) and the angle. As such, the angle error voltage ∈ has an approximate S-shape, and permits the detection of deviation from the center direction between the two beams. The reason of the normalization with the sum signal (Σ) is that if the angle were measured using only the difference signal (Δ), the signal could vary notably depending on the size and the distance of a target.

When the center direction of the two beams is denoted by θ0while the angle obtained from the angle error voltage ∈ is denoted by Δθ, the direction θ of presence of a target is expressed by formula (2).
θ=θ0+Δθ  (2)

The processing section107acquires the direction θ of presence of the detection target from this formula (2).

Here, the sum signal (Σ) and the difference signal (Δ) may be generated, for example, by digital processing of digital signals obtained by AD conversion of the reflection signals, or alternatively by passing the reflection signals itself through a pre-comparator.

FIG. 24is a flow chart of calculating the direction θ of presence of a target.

First, the beam direction specifying instrument105sets up the antenna beam such that the monitoring area should become2021. When a detection target is present, the receiving section106acquires a reflection signal (A) reflected and returned from the detection target, and then retains the signal in a storage area in the receiving section106(S2401).

Next, the beam direction specifying instrument105sets up the antenna beam such that the monitoring area should become2022. When a detection target is present, the receiving section106acquires a reflection signal (B) reflected and returned from the detection target, and then retains the signal in a storage area in the receiving section106(S2402).

Then, the processing section107generates a sum signal (Σ) of the reflection signal (A) and the reflection signal (B) (S2403), and generates a difference signal (Δ) of the reflection signal (A) and the reflection signal (B) (S2404). Then, the processing section107divides and normalizes the obtained difference signal (Δ) with the sum signal (Σ), and thereby calculates an angle error voltage (∈) (S2405).

Further, with referring to the data retained already in the memory, the processing section107derives a corresponding angle (Δθ) from the angle error voltage (∈), and thereby acquires the direction θ of presence of the detection target (S2406). On the basis of the obtained direction θ and the distance obtained from the time of arrival (time from the send-out) of the reflection signal, the processing section107acquires accurate position of the detection target.

Here, the processing section107is an example of the first target position determination section of the present invention.

FIG. 25is a diagram showing an example of display contents concerning the situation of the surroundings of a vehicle provided to a driver, in a vehicle surroundings monitoring system employing a vehicle surroundings monitoring apparatus of the present Embodiment 5 described here.

FIG. 25(b) is a diagram showing an exemplary scene in which a child is present in a rearward direction of a vehicle.FIG. 25(a) shows the display contents displayed in the case of such a scene, on a display unit of the vehicle surroundings monitoring system of the present Embodiment 5 installed in the vehicle.

As such, the driver can recognize accurate position of the child who is present in a rearward direction of the vehicle where direct checking is difficult.

Further, since such fine angular resolution is obtained so that the position of a detection target can be detected accurately, more fine-tuned warning can be performed in which, for example, an expected running area is determined on the basis of steering angle data obtained by the steering angle sensor, so that when no collision is expected, no alarm should be generated even when a detection target is present in a rearward direction.

FIG. 26is a diagram showing an example of performing alarm control on the basis of such steering angle data.FIG. 26(a) is a diagram showing a situation that an unavoidable detection target is present.FIG. 26(b) is a diagram showing a situation that an avoidable detection target is present.

InFIG. 26, vehicle surroundings monitoring apparatuses1650having the configuration ofFIG. 16incorporating the steering angle sensor1602are provided as the vehicle surroundings monitoring apparatuses1910,1920, and1930shown inFIG. 20. These vehicle surroundings monitoring apparatuses1910,1920, and1930have the function of the vehicle surroundings monitoring apparatus of the present Embodiment 5 capable of acquiring accurate position of a detection target on the basis of fine angular resolution.

Dotted lines shown inFIGS. 26(a) and26(b) indicate the path of the vehicle body when the vehicle moves rearward.

InFIG. 26(a), a detection target is present at a position where the vehicle body could collide if the vehicle would straightly move rearward. In this case, the processing section507of the vehicle surroundings monitoring apparatus1930acquires accurate position of the detection target located in the overlap region of the two monitoring areas2021and2022. Further, on the basis of the information obtained from the steering angle sensor1602, the processing section507recognizes that the vehicle straightly moves rearward. From these pieces of information, the processing section507determines that if the vehicle would continue to move rearward in this state, the vehicle body could collide with the detection target. Thus, the processing section507generates warning.

In contrast, in a case that a detection target is located at the position shown in the upper part ofFIG. 26(b), even when the vehicle straightly moves rearward, the vehicle body does not collide with the detection target. Thus, no warning is generated.

In the lower part ofFIG. 26(b), a detection target is present in the same position as that ofFIG. 26(a). However, in this case, the vehicle moves rearward while turning the steering wheel to the left. Thus, even when the vehicle continues to move rearward, the vehicle body does not collide with the detection target. On the basis of the information obtained from the steering angle sensor1602, the processing section507recognizes that the vehicle moves rearward while turning to the left, and hence determines that the vehicle body does not collide with the detection target. Thus, no warning is generated in this case.

Here, in the description given above, the vehicle surroundings monitoring apparatus1930has been employed as the vehicle surroundings monitoring apparatus1650shown inFIG. 16, so that the processing section507of the vehicle surroundings monitoring apparatus1930has performed the determination of the position of a detection target and the determination of necessity or non-necessity of generation of warning. However, the vehicle surroundings monitoring system as shown inFIG. 19may be employed so that the central processing section1972may perform these determinations. In this case, the central processing section1972is an example of the first target position determination section of the present invention.

When the angle between the two beam directions of the vehicle surroundings monitoring apparatus is narrowed so that the overlap of the two monitoring areas is enhanced, the (angular) range where accurate position of a detection target can be obtained can be enhanced.

Alternatively, accurate position of a detection target may be detected on the basis of plural pieces of information obtained from a plurality of surroundings monitoring apparatuses arranged at different positions. That is, as shown inFIG. 20, different vehicle surroundings monitoring apparatuses1910,1920, and1930maybe arranged at distant positions. Then, when a detection target is present at a position where monitoring areas of the different vehicle surroundings monitoring apparatuses overlap with each other, the position of the detection target may be determined on the basis of the information obtained from the two vehicle surroundings monitoring apparatuses.

A method of determining the position of a detection target of this case is described below for an example of the vehicle surroundings monitoring system of the configuration ofFIG. 19where different vehicle surroundings monitoring apparatuses1910,1920, and1930are arranged at distant positions as shown inFIG. 20.

When a detection target is present at a position where the monitoring areas of the vehicle surroundings monitoring apparatus1920and the vehicle surroundings monitoring apparatus1930overlap with each other (a region where the monitoring area2012and the monitoring area2021overlap with each other), the processing section of the vehicle surroundings monitoring apparatus1920acquires the distance from the vehicle surroundings monitoring apparatus1920to the detection target. Similarly, the processing section of the vehicle surroundings monitoring apparatus1930acquires the distance from the vehicle surroundings monitoring apparatus1930to the detection target.

The processing sections of the vehicle surroundings monitoring apparatus1920and the vehicle surroundings monitoring apparatus1930transmit each information on the distance to the detection target, to the central processing section1972. Then, the central processing section1972calculates accurate position of the detection target on the basis of these two pieces of information on the distance by the triangulation method, that is, according to a formula of relation between the side lengths and the angles of a triangle.

In this case, the vehicle surroundings monitoring apparatus1920is an example of the one monitoring apparatus of the present invention. The vehicle surroundings monitoring apparatus1930is an example of the another monitoring apparatus of the present invention. Further, the central processing section1972is an example of the second target position determination section of the present invention.

When the above-mentioned method in which the position of a detection target is determined on the basis of two beam directions of one vehicle surroundings monitoring apparatus and the method described here in which the position of a detection target is determined in a region where monitoring areas of different vehicle surroundings monitoring apparatuses overlap with each other are employed together, accurate position of the detection target can be acquired over a wider (angular) range.

As described above, when the vehicle surroundings monitoring apparatus and the vehicle surroundings monitoring system of the present Embodiment 5 are employed, a reliable collision warning system is implemented.

The above-mentioned embodiments have been described for the case that the monitoring apparatus of the present invention is installed in a vehicle. However, the apparatus may be installed in other places. For example, when installed in the inside or outside of a building, the apparatus is applicable in security use, counting of the number of entering and exiting persons, and the like.

The program of the present invention is a program which causes a computer to perform the operation of the step of determining which monitoring area among a plurality of monitoring areas that can be monitored when a beam direction of the radio wave is switched should be activated at which timing on the basis of running state information of said vehicle, and of thereby controlling the monitoring area, in the monitoring control method of the above-mentioned invention, and which operates in cooperation with the computer.

Further, the recording medium of the present invention is a computer-readable recording medium which carries a program of causing a computer to perform the operation of the step of determining which monitoring area among a plurality of monitoring areas that can be monitored when a beam direction of the radio wave is switched should be activated at which timing on the basis of running state information of said vehicle, and of thereby controlling the monitoring area, in the monitoring control method of the above-mentioned invention, wherein said program having been read out is utilized in cooperation with said computer.

Further, a mode of use of the program according to the present invention may be that the program is recorded in a computer-readable recording medium and operates in cooperation with a computer.

Further, the scope of the recording medium includes a ROM.

Further, the above-mentioned computer according to the present invention is not restricted to genuine hardware such as a CPU, and may be firmware, an OS, and a peripheral device.

As described above, the configuration according to the present invention may be implemented by software or hardware.

As such, the present invention disclosed in this specification, the drawings, and the like relates to a surroundings monitoring system, a vehicle, and a monitoring control method for a monitoring apparatus that send out a radio wave, then receive a reflected reflection signal, and thereby detect a material body and a person present in the surroundings. These inventions are listed as follows. Here, it should be noted that these inventions provide a surroundings monitoring system, a vehicle, and a monitoring control method for a monitoring apparatus capable of monitoring a wide (angular) range of vehicle surroundings or the like using a small number of radar sensors.

A first aspect of the invention is a monitoring apparatus for sending out a radio wave, then receiving a radio wave generated by reflection of the radio wave, and thereby detecting a target including a material body and/or a human body, said apparatus comprising:

a transmission antenna section for sending out a radio wave having directivity of a predetermined (angular) range, or alternatively of sending out in different beam directions a radio wave having directivity of an (angular) range narrower than said predetermined (angular) range;

a receiving antenna section for receiving in each different beam direction the radio wave transmitted by said transmission antenna section and then reflected by said target;

a transmission section for transmitting to said transmission antenna section a signal to be sent out as said radio wave;

a receiving section to which the radio wave received by said receiving antenna section is transmitted as a signal from said receiving antenna section; and

beam switching instrument which switches the beam direction sequentially when said receiving antenna section receives said radio wave in said each different beam direction, and which thereby controls a monitoring area.

A second aspect of the invention is a monitoring apparatus of the above-mentioned first aspect of the invention, wherein when said transmission antenna section sends out said radio wave in different beam directions, said beam switching instrument sequentially switches the beam direction of the transmitted radio wave and thereby controls the monitoring area.

A third aspect of the invention is a monitoring apparatus of the above-mentioned second aspect of the invention, comprising transmission and reception switching instrument which switches a signal transmitted from said transmission section and a signal transmitted to said receiving section, wherein

said receiving antenna section serves also as said transmission antenna section, while transmission or reception of the radio wave is switched by said transmission and reception switching instrument.

A fourth aspect of the invention is a monitoring apparatus of the above-mentioned first aspect of the invention, wherein

said receiving antenna section includes one feed element and a plurality of non-feed elements each having a switching element in a central part thereof, and wherein

said beam switching instrument opens or short-circuits each of a plurality of said switching elements individually, and thereby switches the beam direction of the radio wave received by said receiving antenna section.

A fifth aspect of the invention is a monitoring apparatus of the above-mentioned fourth aspect of the invention, wherein

each of said feed element and a plurality of said non-feed elements has a bar shape, and wherein

a part of a plurality of said non-feed elements are aligned in line in a predetermined direction in parallel to said feed element, while

the other part of a plurality of said non-feed elements are aligned in line in a direction different from said predetermined direction, in parallel to said feed element.

A sixth aspect of the invention is a monitoring apparatus of the above-mentioned second aspect of the invention, wherein

said transmission antenna section includes one feed element and a plurality of non-feed elements each having a switching element in a central part thereof, and wherein

said beam switching instrument opens or short-circuits each of a plurality of said switching elements individually, thereby switches the beam direction of the radio wave, and thereby sends out the radio wave from said transmission antenna section in different beam directions.

A seventh aspect of the invention is a monitoring apparatus of the above-mentioned first aspect of the invention, wherein

said receiving antenna section includes a first power feed section and a second power feed section, and wherein

said beam switching instrument performs switching such that power should be fed to either said first power feed section or said second power feed section, and thereby forms beam directions of two radio waves.

An eighth aspect of the invention is a monitoring apparatus of the above-mentioned seventh aspect of the invention, wherein

said receiving antenna section includes: a first feed element having said first power feed section; a second feed element having said second power feed section; and a plurality of non-feed elements, wherein

each of said first feed element, said second feed element, and a plurality of said non-feed elements has a bar shape, wherein

a part of a plurality of said non-feed elements are aligned in line in a predetermined direction in parallel to said first feed element, while

the other part of a plurality of said non-feed elements are aligned in line in a direction different from said predetermined direction, in parallel to said second feed element, and wherein

one non-feed element among said part of a plurality of said non-feed elements serves also as one non-feed element among said other part of a plurality of said non-feed elements.

A ninth aspect of the invention is a monitoring apparatus of the above-mentioned seventh aspect of the invention, wherein

said receiving antenna section includes a reflector plate and a rectangular antenna element parallel to said reflector plate, and wherein

said rectangular antenna element retains said first power feed section and said second power feed section at a pair of two opposing corners thereof and detour elements at the other opposing corners.

A tenth aspect of the invention is a monitoring apparatus of the above-mentioned ninth aspect of the invention, wherein said rectangular antenna element has a substantially square shape, while one side thereof has a length of substantially ⅓ of a wavelength of an operating frequency, and while each of said detour elements has a length of substantially ¼ of the wavelength of the operating frequency.

An eleventh aspect of the invention is a monitoring apparatus of the above-mentioned seventh or ninth aspect of the invention, wherein

said rectangular antenna element is a slot loop antenna having a slot section where a conductor on a conductor face of a dielectric substrate is removed in a rectangular shape, while said detour elements are detour slot parts located at a pair of opposing corners of said slot section, and wherein

each of the other pair of opposing corners of said slot section receives power fed by electromagnetic coupling from an end of one of microstrip lines formed on a surface opposite to the conductor face of said dielectric substrate, while the other end of one of said microstrip lines is said first power feed section, and while the other end of the other of said microstrip lines is said second power feed section.

A twelfth aspect of the invention is a monitoring apparatus of the above-mentioned eleventh aspect of the invention, wherein the surface opposite to the conductor face of said dielectric substrate faces said reflector plate.

A thirteenth aspect of the invention is a monitoring apparatus of the above-mentioned first aspect of the invention, further comprising a first target position determination section for determining a distance to said target on the basis of the signal transmitted to said receiving section, then determining a direction toward said target on the basis of a value obtained when a difference of amplitudes of two signals among a plurality of signals corresponding to a plurality of radio waves received from said different beam directions is normalized by a sum of the amplitudes of said two signals, and thereby determining a position of said target on the basis of said distance and said direction toward said target.

A fourteenth aspect of the invention is a monitoring apparatus of the above-mentioned first aspect of the invention, wherein said monitoring apparatus is installed on a vehicle.

A fifteenth aspect of the invention is a monitoring apparatus of the above-mentioned fourteenth invention, further comprising a running information storing section for storing running state information of said vehicle, wherein

said receiving antenna section includes a first power feed section and a second power feed section, and wherein

on the basis of said running state information stored in said running information storing section, said beam switching instrument performs switching such that power is fed to either said first power feed section or said second power feed section.

A sixteenth aspect of the invention is a monitoring apparatus of the above-mentioned fourteenth aspect of the invention, wherein

at least said transmission antenna section and said receiving antenna section are provided in a front central part and/or a rear central part of said vehicle, and wherein

among said different beam directions, one is directed leftward of said vehicle, while another one is directed rightward of said vehicle.

A seventeenth aspect of the invention is a monitoring apparatus of the above-mentioned fourteenth aspect of the invention, wherein

at least said transmission antenna section and said receiving antenna section are provided within a side mirror of said vehicle, and wherein

among said different beam directions, one is directed forward of said vehicle, while another one is directed rearward of said vehicle.

An eighteenth aspect of the invention is a surroundings monitoring system wherein a plurality of said monitoring apparatuses of the above-mentioned first or fourteenth aspect of the invention are provided and aligned so that a larger region becomes a monitoring area in comparison with the case that said monitoring apparatus is employed in stand-alone.

A nineteenth aspect of the invention is a surroundings monitoring system of the above-mentioned eighteenth aspect of the invention, wherein a timing that all of a plurality of said monitoring apparatuses monitor the same predetermined side and a timing that all of a plurality of said monitoring apparatuses monitor the side opposite to said same predetermined side are switched and controlled in time sharing.

A twentieth aspect of the invention is a surroundings monitoring system of the above-mentioned aspect of the eighteenth invention, comprising a second target position determination section for determining a position of a target on the basis of a distance from one monitoring apparatus, among a plurality of said monitoring apparatuses having been aligned, to said target determined by said one monitoring apparatus and a distance from another monitoring apparatus to said target determined by said another monitoring apparatus arranged distant from said one monitoring apparatus.

A twenty-first aspect of the invention is a vehicle carrying the surroundings monitoring system of the above-mentioned aspect of the eighteenth, nineteenth, or the twentieth invention.

A twenty-second aspect of the invention is a monitoring control method in a vehicle-installed monitoring apparatus for sending out a radio wave, then receiving a radio wave generated by reflection of the radio wave, and thereby detecting a target including a material body and/or a human body, wherein

said method includes the step of determining which monitoring area among a plurality of monitoring areas that can be monitored when a beam direction of the radio wave is switched should be activated at which timing on the basis of running state information of said vehicle, and of thereby controlling the monitoring area.

A twenty-third aspect of the invention is a monitoring control method of the above-mentioned twenty-second aspect of the invention, wherein said step of controlling the monitoring area includes the steps of:

individually opening or short-circuiting each of a plurality of switching elements of a receiving antenna section including one feed element and a plurality of non-feed elements each having a switching element in a central part thereof, and thereby setting the beam direction of the received radio wave to be a predetermined direction; and

switching the open or short circuit of a plurality of said switching elements, and thereby setting the beam direction of the received radio wave to be a direction different from said predetermined direction.

A twenty-fourth aspect of the invention is a program of causing a computer to execute the step of determining which monitoring area among a plurality of monitoring areas that can be monitored when a beam direction of the radio wave is switched should be activated at which timing on the basis of running state information of said vehicle, and of thereby controlling the monitoring area, in the monitoring control method of the above-mentioned twenty-second aspect of the invention.

A twenty-fifth aspect of the invention is a recording medium which carries the program of the above-mentioned twenty-fourth aspect of the invention and which can be processed by a computer.

A monitoring apparatus has an effect that a wider (angular) range of vehicle surroundings can be monitored using a small number of monitoring apparatuses, and hence is useful as a surroundings monitoring apparatus for a car or the like. Further, the apparatus maybe installed inside or outside a building instead of a car. In this case, the apparatus is applicable in security use, counting of the number of entering and exiting persons, and the like.