JPS591986B2 - radar couch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radar device that obtains both distance and velocity information.

With radars that obtain both distance and speed information, pulse radars and other methods generally measure distance and differentiate it on the time axis to calculate speed, while continuous wave radars use a two-subwave modulation signal. The common method was to calculate the distance from the phase difference between two Doppler signals, and obtain the velocity from either Doppler signal.

In all of these methods, if you try to improve the accuracy of either distance or speed information, the accuracy of the other information will decrease, or
Ambiguity arises.

Not only that, but obtaining one piece of information from another generally requires a fairly complex circuit configuration.

The present invention proposes an improved radar device that can detect both distance information and speed information with high accuracy, and can also sufficiently detect these information even in the case of interference.

FIG. 1 shows an embodiment of the inventive device.

In the figure, 1 is a trigger generator that generates a trigger signal St, 2 is a modulation signal generator that generates a modulation signal Sm, and 3 is a frequency modulation oscillator whose frequency is modulated by the modulation signal Sm. The well-known varactor modulated Gunn oscillator is used, which includes a Gunn diode and a varactor diode.

4 is a coupler that receives the output So of the frequency modulation oscillator 3, and supports the first and second output sections 41 and 42.

A circulator 5 has three terminal parts 51, 52 and 53, and the terminal part 51 is coupled to the output part 41 of the coupler 4.

6 is a transmitting/receiving antenna coupled to the terminal section 52 of the circulator 5; 7 is a mixer for mixing the output obtained from the terminal section 53 of the circulator 5 and the output obtained from the output section 42 of the coupler 4; 8; is an intermediate river wave amplifier connected to the output part of this mixer γ, and the output part is connected to a distance determination circuit 10 via a video amplifier 9.

11 is a Doppler amplifier connected to the output part of the mixer 1, and the output part is connected to the speed determination circuit 12.

14 is a speed judgment output terminal.

15 is a code signal generator that outputs a code signal Sc.

The modulation signal generator 2 includes a pulse generation circuit 21 that receives a trigger signal St, and an adder 22.

This adder 22 adds the pulse signal Sp from the pulse generator 21 and the code signal Sc to generate a modulation signal Sm.

The distance determination circuit 10 performs determination processing on the output of the video amplifier 9 using the trigger signal St, and outputs a determination output to the output terminal 13.

The speed determination circuit 12 performs determination processing on the output signal (Doppler signal) Sd of the Doppler amplifier 11 with reference to the code signal Sc, and outputs a determination output to the output terminal 14 .

The circuit from the intermediate frequency amplifier to the distance determination circuit 10 constitutes the distance determination output circuit 16, and the circuit from the Doppler amplifier 11 to the speed determination circuit 12 constitutes the speed determination output circuit 1.
Configure γ.

The pulse signal Sp is the first frequency control signal for the oscillator 3, and the code signal Sc is the second frequency control signal for the oscillator 3.
These are frequency control signals, and the entire frequency of the oscillator 3 is controlled by each of these control signals.

Now, the operation will be explained with reference to FIG.

In the figure, a shows the trigger signal St, b shows the pulse signal Sp, and C shows the trigger signal St.
is the code signal Sc, d is the modulation signal Sm, e is the frequency change of the oscillation output So, f is the output power of the oscillation output So, g is the output signal SIF of the intermediate river wave amplifier 8, and h is the Doppler amplifier 11. The output signal Sd of is shown.

Note that each horizontal axis in FIG. 2 is a time axis. The trigger generator 1 generates a trigger signal St with a repetition period (operation period) T as shown in FIG. 2a.

This operation cycle T is the maximum detection distance by the radar device R
When, T>2R/C is set.

However, C is the propagation speed of radio waves. The pulse generator 21 generates a pulse signal Sp (FIG. 2b) having a pulse width τ every time the trigger signal St is generated.

The pulse width τ is set to be (1/10 to 1/1000)T, the period of the pulse width τ is the first time segment of the operating period T, and the (T-τ) period is the second time segment. It is a time division.

The code signal Sc has two levels Sc1°S in this example.
C2, (SC2>5CI).

In the one shown in FIG. 2C, the first period TA up to time tc
, level Sc1, second period TB after time tc
It has a level Sc in .

TA during this period. TB is configured to repeat alternately, for example.

However, N consecutive periods T A t T B +
T O......Different levels S for TN
c1, Sc2.

It can also be configured to have Sc3...Scn.

The amplitude of the modulation signal Sm is as shown in FIG.
p and the signal Sc, and the same wave number modulation generator 3 undergoes inter-wave number modulation by this modulation signal Sm.

The modulation signal Sm is applied to a barrack diode of a barrack modulated Gunn oscillator, for example.

The modulation signal Sm has a level Sma1 for the period TA.
! Sma2 (Sma2>Smal) and period TB
Regarding the level Smb 1, Smb 2 (S
mb2>Smb1).

Levels Smal, Smbl in the second time segment
are the levels Scl and Sc without the pulse signal Sp being added.
Sma2.2, which depends only on the level Sma2.2 in the first time segment. Smb2 sends a pulse signal Sp to it.
This is the level when .

As shown in FIG. 2e, the frequency of the oscillation output So of the oscillator 3 is the same wave number f1□l f12(f
l□>fll) f2□t f22 in period TB
(f22>f21).

However, f21>fil. Frequency fil j f21
depends on the level Sma1, Smbl, and the frequency f12
°f22 is level Sma2. Depends on Smb2.

During the period when the frequency is f12 + f22, the pulse width τ
This is the period of

As shown in Figure 2 f, the power (amplitude) of the oscillation output So is kept at a nearly constant value regardless of changes in its frequency, but the performance of the oscillator 3 may vary somewhat depending on the oscillation frequency. .

Now, the operation as a pulse radar will be explained.

Now, let's think about period TA. In the first time segment, the transmission signal oscillated at the frequency f1□ passes through the coupler 4, enters the circulator 5, and is radiated from the antenna 6.

The signal reflected from the target is received by an antenna 6 and enters a mixer 7 via a circuit radar 5.

At this time, the frequency modulation oscillator 3 is in the second time segment and is oscillating at the frequency fll, and a part of its output is applied from the output section 42 of the coupler 4 to the mixer γ, and is at the frequency f12. mixed with the received signal f 12' f I+
An intermediate frequency signal SIF with a frequency fIF equal to is generated.

v Here 022f12+-fl.

It is. Note that ■ is the relative speed between the target and the radar.

The pulse width of the intermediate in-wave signal SIF is equal to the width τ of the transmitted pulse.

This intermediate frequency signal SIF is
It is delayed by the round trip time t from the antenna 6 to the target.

(If circuit propagation time is not taken into account for simplicity of explanation).

Of the output signal of the mixer 7, the component of the frequency fIF is the second
It will look like figure g.

This intermediate frequency signal SIP is amplified by an intermediate wave control amplifier 9, then detected and amplified by a video amplifier 8, and sent to a distance determination circuit 10.

The distance determination circuit 10 uses the trigger signal St from the trigger generator 1 as a reference on the time axis, and measures the delay time of the video signal from it.

Distance information is obtained at the output terminal 13.

The radar device shown in FIG. 1 operates as a pulse radar as described above, and at the same time, it also operates as a Doppler radar.

The operation of this Doppler radar will be explained.

As explained above, the frequency modulation oscillator 3 oscillates at the same wave number f12 in the first time segment, and then continues to oscillate at the same wave number f12 in the first time segment.
It oscillates at wave number f11 in the time division of , and a part of this frequency fil signal is used as a local oscillation signal for the pulse radar, but at the same time, the rest is sent to coupler 4.
, and is radiated from the antenna 6 as a transmission signal as a Doppler radar through the circulator 5.

This signal radiated at the frequency fil is received by the antenna 6 at the same wave number (f11±fd) when reflected by the moving target.

In this case, it is given by f d --f 11.

Here, the + of ±fd is - when the target approaches the radar.
This is when it moves away.

A received signal having a frequency of (f11 to fd) enters the circulator 5 from the antenna 6 and enters the mixer 1.

At this time, mixer 1 uses fil as in the explanation of the pulse radar.
is injected from the coupler 4 and serves as a reference signal for homodyne detection, so that the mixer 1 obtains a Doppler signal Sd having a frequency fd.

This Doppler signal Sd is amplified by a Doppler amplifier 11 and sent to a speed determination circuit 12.

In the speed determination circuit 12, target moving speed information is obtained from an output terminal 14 that measures the frequency of fd.

The above is an explanation of how this device works simultaneously as a pulse radar and a Doppler radar, but further explanation will be given on how the pulse and Doppler radars influence each other.

First, when operating as a pulse radar, the difference from a normal pulse radar is that even after the transmission pulse with the pulse width τ and the same wave number f12 is sent out, it continues to be repeated at the frequency of fll until the next scoopless signal sp. The point is that it is being transmitted continuously.

However, among the reflected signals from the target, the 'ftt component or (
When the component of f11±fd) is mixed with the local oscillation signal of the same wave number fl+ in the mixer 1, it becomes a DC component or a component of fd, and f1□, so that fl2-fl, ”:>fd.
If fl2 is selected, the intermediate frequency signal fIF""ft□-flll will be only the received signal with pulse width τ and frequency f12. Since the intermediate frequency amplifier 8 selectively amplifies only fIF, it will be used as the transmission pulse. frequency f12,
Even if the pulse is continuously transmitted at the frequency fil following the transmission pulse having the pulse width τ, the pulse does not affect the operation of the radar at all.

Next, when operating as a Doppler or radar, we will examine the influence from pulses and radar.

The difference between normal Doppler and radar and the operation of this device as Doppler and radar is that the transmitted signal at frequency fll is
Both the reference signal and the received signal of frequency (f1□±fd) have a ratio of τ/T, f1□ and (f,2±f
d') signals are mixed.

v Here, f'd knee f12.

However, since the duration of the fl2 signal is τ, a bandwidth of approximately 1/τ is required to pass the signal component associated with fl2.

Therefore, if τ is selected such that f d << 1 /τ, the influence of the f12 component will not appear on the output of the Doppler amplifier.

In this case, it is desirable that τ/T is also as small as possible.

The above is an explanation about the period TA, but for the period T-B, fil in the above explanation is changed to f21, and fl2 is changed to f2.
The same thing happens if you replace it with □.

In addition, the periods TA and TB each include a plurality of periods T, specifically, the Doppler signal Sd of at least one cycle
is obtained in each period, usually 10 to
The size is chosen as 100OT.

It should be noted that the same wave numbers fIF of the intermediate frequency signals SIF obtained for the periods TA and TB are the same.

Frequency fIF=f+□-fil obtained in period TA,
The same wave number fIF"f2□-f21 obtained in the period TB both depends only on the magnitude of the pulse signal Sp,
It does not depend on changes in levels Sc11 and Sc2.

Therefore, by keeping the magnitude of the pulse signal Sp constant, the intermediate frequency amplifier 8 can detect any of them.

Regarding the frequency fd of the Doppler signal Sd, filf21
Therefore, its value changes during the period TAtTB, but
There is no problem because the speed determination circuit 12 performs speed determination with reference to the level Scl + SC2 that determines flll + f21.

Of course, if f21 is set during flll, the signal Sc is sent to the determination circuit 12.
It is also possible to perform speed determination without introducing.

It should be noted that as a result of changing the level of the code signal Sc for the periods TA and TB, it becomes more resistant to interference.

For example, even if it becomes impossible to judge distance and speed in period TA due to interference waves of frequency fil or f1□, the transmission frequency is f21 + f22 in period TB.
, so distance and velocity determinations can be achieved regardless of this interference.

As another example, the code signal Sc is a function F(
It can be tl.

FIG. 3C shows an example of such a code signal Sc.

The modulation signal Sm in this case is shown in Figure 3d, and the oscillation output S
The frequency changes of o are shown in e of the same figure.

The power of the oscillation output So is kept approximately constant as shown in FIG. 3f, but may vary within a range that does not affect the radar detection distance.

In the example of FIG. 3, the frequency of the oscillation output So is (f(tJ
+f, ), and then in the second time interval (T-τ) when sp disappears, it becomes (f(t)+f2). However, the pulse signal Sp is independent, and when it occurs, the frequency f
1. It was thought that when it disappears, a frequency f2 (f2<fl) is generated.

In this case, the frequency flF' of the intermediate frequency signal SIF' is I
t(t)+tt)−(f(t)+f2)=f
l−f22fIF, which can be kept constant regardless of F(t) and can always be detected by the intermediate frequency amplifier 8.

Regarding the Doppler frequency fd, since it has a sufficiently lower frequency than the Doppler frequency fd at which the function F(tl is obtained, the same wave number change f based on the function F(tJ) for each cycle of the sequentially obtained Doppler signal Sd (
tJ can be virtually ignored.

In other words, a function F(tl) having such the same wave number is selected.

Therefore, sufficiently accurate speed information can be obtained.

Of course, the same wave number of the Doppler signal 8d changes when viewed from the low same wave number of the function F (tl), but there is no problem because the speed determination circuit 12 determines the speed by referring to the function F(t).

In the case of using this function F(l, the transmission frequency changes sequentially, so it becomes more resistant to interference.

FIG. 4 exemplifies the case where a sine wave function is used as the function F (tl).

FIG. 4 shows the function code signal 5c=F(tl) during the cycle.

FIG. 5 shows another embodiment of the radar device of the present invention.

In this embodiment, as shown in FIG. 6C, the code signal Sc is a signal that becomes "L" level in period TA and becomes "H" level in period TB, and this period TA and TB appear alternately. It is configured as follows.

The modulation signal generator 2 has a voltage level setting circuit 23 that receives the code signal Sc;
When c is at the "L" level, the voltage level VL is set to the voltage level VL, and when it is at the "H" level, the voltage output V is set to the voltage level VH (VH>VL).

(Figure 6a).

This voltage level difference (VHVL) is the same as the magnitude of the pulse signal Sp.

The modulation signal generator 2 further includes an inversion control circuit 24, which controls the polarity of the pulse signal Sp in accordance with the code signal Sc and outputs a converted pulse signal Sp'.

Specifically, the inversion control circuit 24 controls the code signal Sc to be “H”.
FIG. 6e shows a conversion to invert the polarity of the pulse signal Sp when the N5-less signal Sp' is at the "N5 level."

In this embodiment, in the period TA, the modulation signal Sm has a voltage level of 1 when the pulse signal Sp is generated.
, when the pulse signal Sp disappears, the voltage level V2 is set, and in the period TB, when the pulse signal Sp disappears, the voltage level ■1 is set, and when it occurs, the voltage level V2 is set. It will have .

1i pressure level V, is ■□+Sp2■.

, and the voltage level v2 is v2=vH-8p-v□.

The oscillation output Sc has a frequency f1 when the modulation signal Sm has a voltage level v1, and a frequency h (when it has a voltage level ■2).
f,>h) (Fig. 6g).

The power, that is, the amplitude of the oscillation output So is kept almost constant as shown in Figure 6.

This embodiment also operates as a pulse radar and a Doppler radar in the same way as described with reference to FIGS. 1 and 2.

For period TA, replace fl2 with fl and fil with f2, and for period TB, replace f22 with f2 and replace f21 with f21.
If you replace fl with fl, the same operation description applies as is.

Also in this embodiment, the intermediate frequency fIF is
A and TB are the same and can be detected together by the intermediate frequency amplifier 8.

The Doppler frequency fd is the frequency f2 during the period TA, and the Doppler frequency fd is the frequency f2 during the period TA.
In case B, it depends on the same wave number f1, but there is no problem because the speed determination circuit 12 outputs speed information by referring to the code signal Sc.

Regarding interference waves, even if speed information cannot be detected during period TA due to interference at frequency f2, this can be detected during period TB.

Note that in each embodiment, the periods TA and TB do not necessarily have to be the same time length;

The time point tc at which TB is switched does not necessarily have to coincide with the time point at which the trigger signal St is generated.

Overall, the radar device of the present invention is a type of frequency agility radar, but it differs from conventional frequency agility radars in that it uses a conventional transmitter corresponding to the period τ of the pulse signal Sp, and a period (T-τ). A conventional local oscillator corresponding to the conventional local oscillator is shared by the oscillator 3, and although it is not a so-called amplification type agility radar, but a final stage oscillation type (magnetron type) agility radar, the oscillator for the local oscillator is used in common. The advantage is that a wave number tracking circuit is not required.

The radar device according to the present invention can be applied to cases where a large number of radars of the same type are used in the same area by making use of the characteristic of being resistant to interference, and even in this case, the probability of mutual interference between the radars of the same type can be sufficiently reduced.

Specifically, it can be widely applied to trains, airplanes, automobiles, etc., but is particularly effective as an automobile radar.

As described above, according to the present invention, it is possible not only to obtain both distance information and speed information with high precision and in a simple manner, but also to be able to reliably obtain such information even in the event of interference.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the device of this invention, FIGS. 2, 3, and 4 are operation explanatory diagrams, FIG. The figure is an explanatory diagram of the operation. In the figure, 1 is a trigger generator, 2 is a modulation signal generator, 21 is a first frequency control circuit (pulse generation circuit), 22 is an adder, 23 is a voltage level setting circuit, 24 is an inversion control circuit,
3 is a frequency modulation oscillator, 4 is a coupler, 5 is a circulator, 6 is an antenna, 1 is a mixer, 8 is an intermediate frequency amplifier,
9 is a video amplifier, 10 is a distance determination circuit, 11 is a Doppler amplifier, 12 is a speed determination circuit, 13 and 14 are output terminals,
15 is a second frequency control circuit (code signal generator);
6 is a distance judgment output circuit, and 1γ is a speed judgment output circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a radar device that obtains the distance and speed of a target, a first time segment of a short time corresponding to the transmission pulse width as a pulse radar for obtaining distance information about sequentially repeated operation cycles and a second time segment of the remaining time are used. a first frequency control circuit that generates a first control signal that changes the oscillation output frequency of the frequency modulation oscillator in the first time segment; In addition, the same wave number of the oscillation output of the frequency modulation oscillator in the second time segment is also different so that the difference in frequency of the oscillation output in each time segment of each operation cycle becomes a predetermined intermediate frequency signal. a second frequency control circuit that generates a second control signal that changes the operating cycle; a received wave obtained by transmitting the oscillation output in the first time segment; a distance information output circuit that outputs distance information based on intermediate frequency signals having different frequencies, and a received wave obtained by transmitting the oscillation output in the second time segment and the oscillation output in the second time segment. the second control signal has a frequency that is optically lower than the frequency of the Doppler signal, and the second control signal has a frequency that is optically lower than the frequency of the Doppler signal; A radar device characterized in that the frequency of the oscillation output in the first time segment and the frequency of the oscillation output in the second time segment are sequentially changed.