JPS624669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radar device for preventing collisions in automobiles and the like. A description will be given below using a radar device for automobile collision prevention as an example.

As a result of double-driving cars and faster speeds, the number of collisions has increased dramatically, with many accidents resulting in loss of human life. In order to prevent these accidents as much as possible, the system detects obstacles, measures the distance to them, and relative speed, and also takes into account driving information such as the own vehicle's steering angle and vehicle speed to detect the risk of collision. However, progress is being made in the development of automobile collision prevention radar devices that issue a warning to the driver or automatically operate a brake mechanism.

FIG. 1 is a block diagram showing an example of the high frequency section of a conventional device of this kind. In the figure, 1 is an antenna, 2 is a hybrid coupler, 3a, 3b are switches, 4a, 4b are mixers, and 5 is a frequency modulator. ,
FM gun oscillator, 6 is the FM gun oscillator, varactor driver that drives the varactor diode of 5, 7
8 is a trigger oscillator that drives the varactor driver 6 and switch driver 7, and 9 is an intermediate frequency IF obtained by mixers 4a and 4b. An IF amplifier amplifies the signal, and 10 is an IF signal output terminal.

Figure 2 is a waveform diagram for explaining the operation of the oscillation part. Shows the transmit signal output. As shown, a varactor driver 6 and a switch driver 7 supply drive pulses as shown in FIG. 2A to an FM gun oscillator 5 and switches 3a and 3b, respectively. The FM gun oscillator 5 oscillates at frequency ₁ during period T ₁ and oscillates at frequency _L during period T ₂ as shown in FIG. On the other hand, the switches 3a and 3b are driven to be short-circuited during period _T1 and open during period _T2 . Therefore, during period T ₁ the frequency
The oscillation output of switch ₁ is applied to switches 3a and 3b through hybrid coupler 2, but switch 3
Since the wires a and 3b are short-circuited, the antenna 1 is connected again through the hybrid coupler 2 as shown in FIG. 2C.
Sent from. During period T ₂ , the oscillation output of frequency _L passes through hybrid coupler 2 and switches to switch 3.
a, 3b, but in this case switch 3
Since a and 3b are open, this frequency _L
The oscillation output is sent to mixers 4a and 4b and operates as a local oscillation output for receiving reflected waves, which will be described later, and is not substantially emitted from the antenna 1.

Frequency ₁ transmitted from antenna 1 during period T ₁
The radio waves are reflected from the target object, are received from the antenna 1 after entering the period _T2 , and are further transmitted to the open switches 3a and 3 via the hybrid coupler 2.
It is added to mixers 4a and 4b without being hindered by b. On the other hand, in this case, the FM
Since the oscillation output of frequency _L from Gunn oscillator 5 is applied to mixers 4a and 4b as local oscillation output, IF = _IF =
An intermediate frequency IF signal with a frequency of ₁ − _L is obtained. IF obtained from these mixers 4a and 4b
The signals are summed and amplified by an IF amplifier 9,
The signal is output to the IF signal output terminal 10.

Next, a conventional device for obtaining Doppler waves that provide velocity information of a target from this IF signal is shown in the block diagram shown in Fig. 3, the operating waveform diagrams at various phases shown in Figs. 4A to D, and Fig. 5. This will be explained using a combined waveform diagram.

In the figure, 11 is an IF signal input terminal, 12 is an input terminal for the transmission trigger a obtained from the trigger oscillator 8 in FIG. The first comparator that outputs c, 14 is a negative set value -E2
15 is an OR circuit which obtains a signal e which is the logical sum of the signal c and the signal d. 16 is an OR circuit which is set by the signal a and reset by the signal e and outputs the signal. -S flip-flop circuit, 17 is an AND circuit that outputs a signal g which is the logical product of the signal c and the signal, 18 is an AND circuit that generates the signal h which is the logical product of the signal d and the signal, and 19 is set by the signal g. An RS flip-flop circuit which is reset by a signal h and outputs a signal i shown in FIG. 5, 20 is a signal i which is a desired Doppler wave.
This is the terminal to take out.

IF shown in b of each of Figures 4A to D
The rising phase of the signal changes sequentially, but this is caused by the transmission trigger a at predetermined time intervals.
The IF signal obtained by receiving the reflected waves of the transmitted pulses sent out one after another is shown along the flow of time, and is due to the Doppler effect accompanying the relative movement of the target. Therefore, by plotting this rising phase, a Doppler waveform can be obtained.

FIG. 3 shows a device based on such a principle, in which the flip-flop 16 is set by the transmission trigger a and reset when the rising edge of the IF signal b reaches a predetermined amplitude, whether positive or negative. There is an operation delay of the logic circuit between the signals c, d and the signal e, and between the rise of the signal e and the rise of the signal (reset of the flip-flop 16).
AND circuits 17, 18 and flip-flop 1
From the configuration of 9, the IF signal b as shown in Fig. 4 A and B
starts from positive polarity, a signal g is obtained, and the fourth
When starting from negative polarity as shown in Figures C and D, the signal h
is obtained, the flip-flop 19 is inverted at the boundary, and it is easy to understand that a Doppler signal as shown in FIG. 5i is obtained. However, it should be noted that FIG. 5 shows the time axes of FIG. 4 A, B, C, and D compressed.

In principle, this method is an excellent method for obtaining a Doppler signal with an extremely simple circuit, but if there are fluctuations in the level of the received signal, it will not work as shown in Figure 5, and for example, as shown in Figure 6. The waveforms become as shown in g', h', and i', making it impossible to obtain a normal Doppler signal. Furthermore, with the above method, it was impossible to determine the moving direction of the target object.

This invention was made in view of the above points,
By individually using the two IF signals obtained from the mixer, a correct Doppler signal can be obtained even if the received signal level fluctuates, and the radar can be developed to have the ability to determine the moving direction of a target. The purpose is to obtain a device.

FIG. 7 is a block configuration diagram showing an embodiment of the present invention. In the figure, from the antenna 1 to the mixer 4a,
4b and from the FM gun oscillator 5 to the trigger oscillator 8 are the same as the conventional device shown in FIG.
a, 9b, and terminals 10a, 10, respectively.
Output to b.

This invention was made by focusing on the fact that the two IF signals obtained in this way have a phase difference of 90 degrees from each other. It will be appreciated that the Doppler signals included in the signal also have a 90° phase difference at the Doppler frequency. This invention is
Using the phase difference between two Doppler signals, abnormal waveforms based on fluctuations in reception level as shown in Figure 6 are generated.
The aim is to obtain a normal Doppler signal even when g' and h' are obtained. The operation of the apparatus of this embodiment will be explained below with reference to FIG. 8, which shows waveforms of various parts.

Now, the IF signals amplified by the IF amplifiers 9a and 9b in this way are each sent to the Doppler generator 21.
a, 21b. This Doppler generator 21
Both a and 21b are similar to the conventional device shown in FIG. For example, with respect to the Doppler generator 21a, signals g and h are changed as shown in FIG.
g' and h', the output i _a becomes as shown in FIG. 8 i _a ', and the Doppler generator 21b
The output has a waveform i _b ' in FIG. 8 having a phase difference of 90° at the Doppler frequency as described above.
22a and 22b are Doppler generators 21a and 22b, respectively.
This is a differentiating circuit that obtains time-differentiated waveforms of the outputs i _a and i _b of the differentiating circuit 21b.
Only _a is shown. 23a and 23b are double-wave detection circuits, and 24a and 24b are monostable multivibrators that generate pulses of a predetermined width triggered by the output pulses of the double-wave detection circuits 23a and 23d, respectively, and their output waveforms are shown in FIG. Shown in _a and k _b . 25 is an RS flip-flop which is set by signal k _a and reset by signal k _b and outputs an output waveform m; 26 is a signal i _b when the signal waveform m is at a high potential.
and when the signal waveform m is at a low potential, the signal i _a
A switch circuit 27 switches to output a signal n having a desired accurate Doppler period at the output terminal of this switch circuit 26. I believe that the operation of this device can be understood from the above explanation, but in short, in this invention, the reflected reception microwave and the local oscillation frequency output are combined by a hybrid coupler, and this is added to a balanced mixer to generate two IF signals. Therefore, there is a 90° phase difference between the two IF signals. Therefore, by taking advantage of the fact that there is a 90° phase difference in the Doppler signals included in both IF signals, each Doppler signal is obtained individually, and if an abnormal waveform appears in one of them, the other is used. By doing this, a signal with a normal Doppler period can be obtained, and by counting the wave numbers within a predetermined time, velocity information of the target object can be obtained. To explain in more detail, abnormal waveforms occur in the vicinity of the period when the state of the Doppler signal reverses, but during the period in which there is ambiguity in the state of one Doppler signal (unstable period), the state of the Doppler signal is ambiguous. 90〓 This is a stable period in a Doppler signal having a phase difference, and an abnormal waveform does not necessarily occur in the unstable period of one Doppler signal of the other Doppler signal. Therefore, the timing at which the state of each Doppler signal inverts is detected, and the other Doppler signal is used for the unstable period in the vicinity.

Next, a portion A surrounded by a dashed line in FIG. 7 will be explained using the waveform diagram for explaining the operation shown in FIG. 9. By adding this portion A, a signal for determining the moving direction of the target object can be obtained. In the figure,
28 is a frequency divider which divides the signal m by 1/2 and outputs the signal p, and 29 obtains the exclusive OR Ex-OR signal q of this signal p and the signal n obtained at the output terminal 27.
In the Ex-OR circuit, 30 is an output terminal that outputs a direction determination signal q.

That is, when the target is approaching the radar device and when it is moving away from the radar device, the phase relationship between the output signals i _a and i _b obtained from the Doppler generators 21a and 21b is as follows. It will be the opposite. The signals i _a ' and i shown in FIG. 8 and also shown in FIG.
If the relationship with _b ' is the phase relationship when the target is approaching, the relationship when the target is moving away is the relationship between the signals i _a ' and i _b ' _r in Figure 9. become that way. (In the figure, the subscript r is added to this latter case and all are indicated by broken lines.) As can be seen from FIG. 9, the output signal p of the frequency divider 28
is constant regardless of the moving direction of the target, and Ex
- In the OR circuit 29, the output q is connected to the signal n.
However, the output signals p and n _r have exactly the same waveform, and the output q _r is always zero. Information on the moving direction of the target object can be obtained from this signal output q.

As described in detail above, in this invention, the reflected reception wave of the radar pulse from the target object and the local oscillation frequency wave are combined by a hybrid coupler, a balanced mixer is provided on the output side of the hybrid coupler, and two Get each IF signal at the output, and
By obtaining Doppler signals from each signal, the phase difference between the two Doppler signals is used, and when one Doppler signal is unstable, the other Doppler signal is adopted, so that a normal Doppler signal can be obtained. can get.

Further, by determining the phase of the Doppler signal obtained in this way, a signal indicating the moving direction (approach or departure) of the target object can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block configuration diagram showing an example of the high frequency section of a conventional radar device, Figure 2 is a waveform diagram to explain the operation of the oscillation section, and Figure 3 is a diagram of a conventional Doppler generator. The block configuration diagram, Figures 4A to 4D are operational waveform diagrams of each part of this Doppler generator at various phases, Figure 5 is a combined waveform diagram, and Figure 6 is a Doppler diagram when there is a fluctuation in the received signal level. A diagram showing an example of an output waveform, FIG. 7 is a block configuration diagram showing an embodiment of the present invention, FIG. 8 is a waveform diagram of each part to explain its operation, and FIG. 9 is a diagram showing information on the moving direction of a target. It is a waveform diagram of each part for explaining the operation of the obtained part. In the figure, 1 is an antenna, 2 is a hybrid coupler, 3a, 3b are switches, 4a, 4b are mixers, 21a, 21b are Doppler generators, 22a, 2
2b is a differential circuit, 23a and 23b are double wave detectors,
24a, 24b are monostable multivibrators, 2
5 is a bistable circuit, 26 is a switch circuit, 27 is a Doppler signal output terminal, 28 is a frequency divider, 29 is an exclusive OR circuit, and 30 is a moving direction determination signal output terminal. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A hybrid coupler that combines a received wave reflected from a target object of a transmitted high-frequency pulse radio wave and a local oscillation frequency wave, and a hybrid coupler provided on the output side of the hybrid coupler and having a phase difference of 90° from each other. first and second balanced mixers for obtaining first and second intermediate frequency signals having the following characteristics; for each of the intermediate frequency signals, detecting the polarity of the first half cycle of each intermediate frequency pulse that changes at the period of the Doppler frequency; first and second Doppler generators that obtain first and second Doppler signals having a phase difference of 90 degrees from each other, and a detection means for detecting unstable periods near the rising and falling edges of each of the above Doppler signals. , and A radar device comprising: a switching circuit that outputs a Doppler signal by replacing the unstable period of each Doppler signal with the other Doppler signal. 2 The detection means includes first and second differentiating circuits that differentiate the first and second Doppler signals obtained from the first and second Doppler generators, and outputs of these differentiating circuits into both waves. A first and second double-wave detection circuit that rectifies and shapes the waveform, and is set by the waveform shaping output obtained from the first Doppler signal and reset by the waveform shaping output obtained from the second Doppler signal. the switching circuit outputs the second Doppler signal when the bistable circuit is set;
2. The radar device according to claim 1, further comprising a switch circuit that outputs the first Doppler signal when the radar device is reset. 3. A hybrid coupler that combines the reflected reception wave from the target of the transmitted high-frequency pulse radio wave and the local oscillation frequency wave, a first and a first coupler that are provided on the output side of this hybrid coupler and have a phase difference of 90 degrees from each other. The first and second balanced mixers obtain two intermediate frequency signals, and for each of the above intermediate frequency signals, detect the polarity of the first half cycle of each intermediate frequency pulse that changes with the period of the Doppler frequency, and first and second Doppler generators that obtain first and second Doppler signals having a phase difference; detection means for detecting unstable periods near the rising and falling edges of each of the Doppler signals; A switching circuit that outputs a Doppler signal by replacing the unstable period with another Doppler signal, and a phase determination circuit that determines the phase of the Doppler signal obtained from the switching circuit to obtain a moving direction determination signal of the target object. A radar device characterized by: 4 The detection means includes first and second differentiating circuits that differentiate the first and second Doppler signals obtained from the first and second Doppler generators, and outputs of these differentiating circuits into both waves. A first and second double-wave detection circuit that rectifies and shapes the waveform, and is set by the waveform shaping output obtained from the first Doppler signal and reset by the waveform shaping output obtained from the second Doppler signal. the switching circuit outputs the second Doppler signal when the bistable circuit is set;
It is a switch circuit that switches to output the first Doppler signal when it is reset, and the phase determination circuit includes a frequency divider that divides the output of the bistable circuit by 1/2, and this frequency divider. 4. The radar device according to claim 3, further comprising an exclusive OR circuit that takes an exclusive OR of the output signal of the switch and the Doppler signal obtained from the switching circuit.