JPH0484794A - Rear watching radar for automobile - Google Patents

Abstract

PURPOSE:To obtain the information of the presence of a rear reflecting object with minimum parts by equipping directional antennas, change-over switches, transmitters, mixers, filters alarm lamps and the like in the number of N(N>=2) to receive an FM-CW wave. CONSTITUTION:Movable contacts of second-fourth change-over switches 21-23 are connected to first-third alarm lamps 41-43 provided in accordance with first-third antennas. The first alarm lamp 41 has displays l1, m1, n1 corresponding to first-third filters 34-36 and also the second alarm lamp 42 posesses displays l2, m2, n2 corresponding to the filters 34-36. The alarm lamp 43 has displays l3, m3, n3 corresponding to the filters 34-36. The displays l1, m1, n1 are connected to the movable contacts a1-a3 of the second-fourth change-over switches 21-23, also the displays l2, m2, n2 are coupled to the movable contacts b1-b3 of the switches 21-23 and the displays l3, m3, n3 are connected thereto. A switch controller 25 is cynchronized with a change-over switch 20 to control first-fourth change-over switches 21-23.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is attached to a car, and uses an FM-CW radar to detect another car approaching from behind the car and warn the driver of the car. The present invention relates to a rear warning radar device for automobiles.

[Conventional technology]

Conventionally, this type of automobile rear warning radar device has antennas installed toward the rear of the vehicle, such as the left, rear, and right sides, and a transmitter/receiver and display are provided for each antenna. The system detects whether another vehicle is approaching behind the vehicle and notifies the driver.

[Problem to be solved by the invention]

For this reason, conventional rear warning radar devices for automobiles have been large-scale. Therefore, there is a drawback that it takes up a lot of space for installation inside a car. Moreover, since many microwave parts are used, it becomes expensive. Furthermore, since detection sensitivity and other adjustments must be made for each transceiver, manufacturing costs increase.

[Means to solve the problem]

The rear warning radar device for an automobile according to the present invention is mounted at a predetermined position on the body of an automobile toward the rear of the automobile,
N (N22) directional antennas for transmitting and receiving FM-CW waves; a first changeover switch that sequentially selects one of the N directional antennas at an appropriate speed;
a transmitter connected to the switching switch Sochi and transmitting an FM-CW transmission wave to the directional antenna selected by the first switching switch Sochi, and connected to the first switching switch and the transmitter; and received by the selected directional antenna.
a mixer that mixes the M-CW reflected wave and the FM-CW transmitted wave and outputs a beat signal;
≧2) M filters outputting filter output signals, and M indicators provided corresponding to the N directional antennas, each corresponding to the M filters.
between the M filters and the N warning lights, each having N output contacts;
M filter output signals are sent to M indicators of warning lights corresponding to the sequentially selected directional antenna among the N warning lights in synchronization with a changeover switch of the M warning lights. A second changeover switch.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a rear warning radar device for an automobile according to an embodiment of the present invention has first to third transmitting/receiving antennas 11, 12, and 13 for transmitting and receiving FM-CW waves.

Referring to FIG. 2, the first to third transmitting and receiving air 1ul
12.13 are attached to the left side, rear side, and right side of the car body, respectively. The directivity of the first to third transmitting/receiving antennas 11, 12.13 is B ll+, respectively.
812+ Like B13, FM on left rear, rear, right rear
- Installed to emit CW waves.

Returning to FIG. 1, the first to third transmitting and receiving antennas 11.1
2 and 13 are movable contacts a of the first changeover switch 20, respectively. + b O+ Connected to CO. Fixed contact d of the first changeover switch 20. has circulator 3
1 is connected. The first changeover switch 20 is configured to switch between the first to third transmitting and receiving antennas 1 under the control of the changeover controller 25.
1, 12, and 13 in sequence.

A transmitter 30 and a mixer 32 are connected to the circulator 31 . The transmitter 30 connects to the first changeover switch 2 via the circulator 31 and the first changeover switch 20.
The FM-CW transmission wave is sent to the transmitting/receiving antenna selected in 0. That is, the FM-CW transmission waves sent out from the transmitter 30 are sequentially transmitted to the first to third transmitting/receiving antennas 11, 12.1.
3, and is radiated as radio waves to the rear left, rear, and rear right of the car.

If there is a reflective object such as a following vehicle on the left rear, rear, or right rear of the vehicle, the first to third transmitting and receiving antennas 11.12.13
Radio waves emitted from the antenna are reflected by the reflecting object, and the reflected waves are received as received waves by the first to third transmitting/receiving antennas 11, 12, and 13.

These received waves are sent to the mixer 32 via the first changeover switch 20 and the circulator 31. mixer 32
is connected to the transmitter 30.

The mixer 32 mixes the received wave sent from the circulator 31 and the FM-CW transmitted wave from the transmitter 30, and outputs a beat signal.

It is well known to those skilled in the art that the frequency of this beat signal is proportional to the distance from the first to third transmitting/receiving antennas 11°12.13 to the reflecting object based on the principle of FM-CW radar. . Therefore, here no more F
A detailed explanation of the principle of the M-CW radar will be omitted.

The amplifier 33 amplifies the beat signal from the mixer 32 and passes the amplified beat signal to first to third filters 34 .
Delivered on 35.36.

Referring to FIG. 3, the first filter 34 passes only the low frequency components below the frequency f1 in the amplified beat signal, and outputs a first filter output signal. The second filter 35 passes only the middle frequency components 1 to f2 in the amplified beat signal, and outputs a second filter output signal.

The third filter 36 passes only high frequency components of the frequency f2 or higher in the amplified beat signal, and outputs a third filter output signal.

Returning to FIG. 1, the first to third filter output signals are:
Second to fourth changeover switches 21, 22, and 23, respectively.
Fixed contact dl+ d2. di. The second changeover switch 21 has three movable contacts aI + bl
+ Equipped with CI. The third changeover switch 22 includes three movable contacts a2 + b2 *-C2. The fourth changeover switch 23 has three movable contacts a3 + b31
Equipped with C3. Second to fourth changeover switches 21.2
2.23 performs a switching operation at an appropriate speed in synchronization with the first changeover switch 20 under the control of the changeover controller 25. More specifically, the first changeover switch 20 is a movable contact a. When selecting the first antenna 11 connected to the
Fixed contacts d,, d2. d3 are movable contacts al
Connected to +82 +83. Similarly, the first changeover switch 20 is a movable contact. When the second antenna 12 connected to the second antenna 12 is selected, the fixed contacts d, d2 . d,
are respectively movable contacts b+.

b2. b. When the first changeover switch 20 or the third antenna 13 connected to the movable contact C8 is selected, the second to fourth changeover switches 21, 22 .
23 fixed contacts 'l+d2+d3 are respectively movable contacts C
Connected to I+ C2+ C3. Each of the second to fourth changeover switches is sometimes referred to as a second changeover switch.

To describe a specific example, while the first selector switch 20 selects the first antenna 11, the first filter 3
If there is an output at 4, it indicates that there is a reflective object near the left rear of the car. Similarly, the first changeover switch 2
If the first filter 34 has an output while o selects the second antenna 12, this indicates that there is a reflective object at a short distance behind the vehicle. If the first filter 34 has an output while the first selector switch 2o selects the third antenna 13, this indicates that there is a reflective object at a short distance to the right rear of the vehicle. Second and third filters 35
．． The same applies to the case where there is an output from 36.

Based on these facts, the position of the reflective object behind the automobile is detected as shown in FIG.

The movable contacts of the second to fourth changeover switches 21, 22, and 23 are connected to Ml provided corresponding to the first to third antennas.
It is connected to third rear warning lights 41, 42, 43. The first rear warning light 41 is connected to the first to third filters 3.
4,35.36 compatible display II I + l
It has r n +. Similarly, the second rear warning light 42
are indicators I2. corresponding to the first to third filters 34, 35, 36. It has m2゜n2. Third rear warning light 43
are the display devices 13, m3., corresponding to the first to third filters 34, 35, 36. Has n3. First rear warning light 41
The indicators i), ml, and n are the movable contacts al + of the second to fourth changeover switches 21, 22, and 23, respectively.
Connected to a2 + a3. Similarly, the second
indicator 12 of the rear warning light 42. m2. n2 are movable contacts of the second to fourth changeover switches 21, 22, 23, b2. Connected to b3. Indicator of third rear warning light 43 N3゜m3. n3 are connected to movable contacts S, b2b3 of the second to fourth changeover switches 21, 22, and 23, respectively.

As described above, the switching controller 25 controls the second and fourth switching circuits 21, 22 . . . in synchronization with the first switching switch 20.
23. The connection situation is shown in FIG. As a result, the positions of the reflective objects displayed by the indicators of the first to third rear warning lights 41, 42, and 43 become as shown in FIG.

First changeover switch 20 and second and fourth changeover circuits 21
．． Switching of 2223 is performed periodically. This cycle is selected to be short enough so that rear monitoring is not hindered.

In the embodiments described above, the case where the rear warning lights 41, 42, 43 are turned on with alternating current by the outputs of the first to third filters 34, 35, 36 has been described.

However, the angle between the first to third filters is 34°35.
36 and the second to fourth changeover switches 21, 22, and 23, respectively, to detect the envelopes of the first to third filter output signals. Alternatively, instead of the first to third filter output signals, the first to third envelope detection signals may be sent to the second to fourth changeover switches, respectively.

Further, in the above embodiment, the rear warning lights 41, 42, 43 are turned on only for one-third of a cycle due to the periodic selection operation of the second to fourth changeover switches. However, in order to make it easier for the driver to see, the light may be turned on continuously. For this purpose, the movable contacts aira2+ a3+ bIn b2* of the second to fourth changeover switches 21, 22, 23
b3r CI+ C2+C1 and rear warning light 41
, 42.43 indicator 11 +m1. n,, J72.
m2. n2,473. One cycle period between m3゜n3,
Nine memories may be inserted to hold the previous first to third filter output signals appearing at the output contacts (movable contacts) selected by the second to fourth changeover switches 21, 22, and 23. .

Further, the frequencies of the first to third filter output signals are decreased between the first to third filters and 34.35° 36 and the second to fourth changeover switches 21 and 22° 23, respectively. It is also possible to provide a means for emitting an output only at certain times. With this configuration, the rear warning light 41 is activated only when there is a high degree of danger, such as when the distance between the rear reflecting object and the vehicle becomes close.
, 42°43 lights up.

Furthermore, each of the first to third directional antennas 11, 12, 13 may have an antenna dedicated to transmission and an antenna dedicated to reception.

Further, the rear warning lights 41 to 43 may be displayed together on one CRT or the like.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to inform the driver of the presence of a rear reflecting object using a minimum number of microwave parts and circuit parts, so that a small and low-cost rear warning radar device for automobiles can be constructed. can. Furthermore, since a single transmitter/receiver can perform left/right rear and backward warning, there is no variation in detection sensitivity depending on the warning area, and an inexpensive rear warning radar device for automobiles that is stable and requires little adjustment cost can be constructed.

11.12.13...Antenna, 20, 21, 22°2
3... Changeover switch, 25... Changeover controller, 30.
...Transmitter, 31...Circulator, 32...Mixer, 33...Amplifier, 34, 35.36...Filter, 41.42.43...Rear warning light.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a rear warning radar device for an automobile according to an embodiment of the present invention, and FIG. 2 shows how the directional antenna used in the rear warning radar device for an automobile shown in FIG. 1 is attached to an automobile. Fig. 3 is a diagram showing an example of the characteristics of the filter used in the automotive rear warning radar system shown in Fig. 1, and Fig. 4 is a diagram showing the characteristics of the filter used in the rear warning radar system for automobiles shown in Fig. 1. FIG. 5 is a diagram showing the relationship of detecting the position of a reflective object, and is a diagram for explaining the operation of the switching controller used in the automobile rear warning radar device of FIG. 1.

Claims (1)

[Scope of Claims] 1. In a rear warning radar device for an automobile that uses an FM-CW radar to detect another vehicle approaching from behind the automobile, a device installed at a predetermined position on the body of the automobile to the rear of the automobile. N (N≧
2) a first selector switch that sequentially selects one of the N directional antennas; a transmitter that sends an FM-CW transmission wave to the selected directional antenna; and an FM-CW reflected wave that is connected to the first changeover switch and the transmitter and is received by the selected directional antenna; a mixer that mixes the FM-CW transmission wave and outputs a beat signal; and M (M≧2) filter output signals that are connected to the mixer and pass only mutually different frequencies in the beat signal. M filters that output , N warning lights provided corresponding to the N directional antennas and each having M indicators corresponding to the M filters; provided between the filter and the N warning lights,
each having N output contacts, in synchronization with the first changeover switch, to the M indicators of the warning lights corresponding to the sequentially selected directional antenna of the N warning lights. Said M
A rear warning radar device for an automobile, comprising: M second changeover switches for transmitting M filter output signals. 2. Connected between the M filters and the M second changeover switches, detecting the envelopes of the M filter output signals, and detecting the envelopes of the M filter output signals instead of the M filter output signals. 2. The automobile rear warning radar system according to claim 1, further comprising an envelope detector that sends M envelope detection signals to the M second changeover switches. 3. Output contacts of the M second changeover switches and the N
The previous M filter output signals that appear at the output contacts selected by the M second selector switches are held between the M warning lights and the M second selector switches until the next M filter output signals appear. 2. The rear warning radar device for an automobile according to claim 1, comprising N×M memory devices. 4. The device according to claim 1, further comprising means provided between the M filters and the M second changeover switches, and outputting the output only when the frequency of the M filter output signals decreases. Rear warning radar device for automobiles. 5. The automobile rear warning radar system according to claim 1, wherein each of the N directional antennas has an antenna dedicated to transmission and an antenna dedicated to reception. 6. The automobile rear warning radar system according to claim 1, further comprising a display device that collectively displays the N warning lights having the M indicators.