JPS62179681A - Phase synchronous tracking radar - Google Patents

Abstract

PURPOSE:To enhance the discrimination capacity of a moving target and a fixed target, by combining a double frequency converting loop and a phase synchronous loop. CONSTITUTION:The outputs 55a, 55b of a second two-phase voltage control oscillator (reference signal oscillator) 58 and the output 61 of a third polarity change-over device 60 are inputted to a modulator 56 to input modulation output 57 to second and sixth mixers 32, 38 as a reference signal. The output 21 of a transmission source 20 is mixed with the output 57 by a mixer 32 to form mixed output 33 which is, in turn, mixed with the output 15 of a receiving antenna 14 in a fifth mixer 34 to form mixed output 35. This output 35 is inputted to a third intermediate-frequency amplifier 36 and the output thereof is mixed with the output by a mixer 38 to obtain the output 41 of a video amplifier 40. This output 41 is subjected to phase detection by a phase detector 44 using output 55a as a reference signal to be inputted to the oscillator 54. The output 41 is further subjected to synchronous detection by a synchronous detector 42 using output 55b as a reference signal to be inputted to a sweep oscillator 52 but, when frequency and a phase coincide, the sweeping of the oscillator 52 is stopped to hold the DC signal of output 53. By this constitution, because the amplifier 36 acts as a narrow-band Doppler gate, resolving power is high.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention irradiates radio waves from a radar to a moving target such as an aircraft or a flying object, and the frequency of the reflected wave from the target is higher than that of the transmitted wave. Continuous-wave Doppler radar or pulsed radar that distinguishes between fixed and moving targets by using characteristics such as high frequency for approaching targets and low frequency for moving targets, depending on the speed of the target. -Relates to Doppler radar, and relates to a phase-locked tracking radar that combines double frequency conversion and a phase-locked loop to improve the ability to discriminate between moving targets and fixed targets, and to improve target detection performance by increasing sensitivity.

(Prior Art) First, the conventional example of the Doppler radar shown in FIG. 2 will be discussed. In this figure, a transmission source output 21, which is an output of a transmission source 20, is input to a power divider 22 and becomes a power divider first output 23a and a second power divider output 23b, one of which is a power divider second output 23b. is input to the second mixer 26, and the other power divider first output 23a is input to the transmission antenna 12 and becomes the transmission signal 13.

A received signal 11, which is a reflected wave from a moving target, is received by a receiving antenna 14 and becomes a receiving antenna output 15. 1 mixer 16
is frequency-converted to become the first mixer output 17,
The signal is input to the first intermediate frequency amplifier 18 and becomes the first intermediate frequency amplifier output 19.

The power divider second output 23b is mixed together with the first local oscillator output 25 in the second mixer 26 and Pj! , 2 mixer output 27, which is input to the second intermediate frequency amplifier 28 and becomes the second intermediate frequency amplifier 29.

The first intermediate frequency amplifier 19 and the fjS2 intermediate frequency amplifier output 29 are respectively input to a PA3 mixer 30 and mixed to become a third mixer output 31, which becomes a Doppler signal of the target reflected wave.

(Problem to be Solved by the Invention) By the way, when an aircraft or a flying object with a small radar reflection area moves at low altitude, a moving target and a fixed target such as the ground or sea surface may be included in the main beam of the radar antenna. The Doppler frequency, which is the frequency difference between the transmitting frequency and the receiving frequency, exists only in reflected waves from moving targets. It is distinguished from a certain clutter reflected wave.

Various improvement measures have been proposed to improve the performance of target detection when targets with small radar reflected waves move at low speeds and low altitudes. They can be summarized as follows.

(a) Distinguish between moving targets and fixed targets by using the Doppler frequency. (b) Narrowing the band of the intermediate frequency amplifier in the previous stage improves the ability to distinguish between moving targets and fixed targets. (c) Transmission By combining circuits, we reduce the inherent phase noise of the machine and local oscillator, which causes a decrease in sensitivity. (i) Differentiate between positive and negative Doppler frequencies to distinguish between approaching targets and receding targets; (i) Increase sensitivity by using synchronous detection when detecting signals. , − (ki) The center frequency of the reference oscillator necessary for demodulating the signal is
In order not to deteriorate the signal-to-noise ratio, in the high frequency section (<) placed outside the signal passband of the intermediate frequency amplifier,
There is no need for a filter with high selectivity. If it is possible to simultaneously realize the above measures, it should be possible to significantly improve the performance compared to the existing Dotsupura radar, and if it can be realized by a simpler method, the economic effect should further increase. .

(Means for Solving the Problems) In view of the above points, the present invention provides a continuous wave Doppler radar or a pulsed Doppler radar by modifying double frequency conversion and a phase locked loop.
The present invention aims to provide a phase-locked tracking radar that improves target detection performance by improving the ability to discriminate between moving targets and fixed targets and by increasing sensitivity.

The present invention irradiates radio waves from a transmitting antenna to a moving target,
In a phase-locked tracking radar that tracks reflected radio waves, the phase of the reference signal for the first frequency conversion, which is created from the signal of the reference signal oscillator and the signal of the two-phase voltage-controlled oscillator or the injection-locked oscillator, is expressed by the following formula % (Formula %)] (where ωC: angular frequency of the transmission signal, φc(t): phase noise of the transmission signal, ωr: angular frequency of the reference signal oscillator, φ
v: phase noise of the reference signal oscillator, ωd: angular frequency of the two-phase voltage-controlled oscillator or injection-locked oscillator, φv: phase control amount, t: time), and furthermore, the signal from the reference oscillator. The Doppler signal is tracked by performing a second frequency conversion using the Doppler signal and inputting the Doppler signal to the two-phase voltage controlled oscillator or injection locking oscillator. The shortcomings of the prior art are solved by means of this method.

(Operation) Since FIG. 3 is a mathematical representation of the signal flow of the embodiment of the present invention shown in FIG. 1, the operation of the present invention will be described using FIG.

In FIG. 3, the two-phase oscillator first output 59a (which is the output of the two-phase oscillator 58 (which acts as a reference signal oscillator)
Xssa) and two-phase oscillator second output 59b (Xssb
) can be expressed as follows.

X56a=sin(a+rt+φr)
−(1)Xssb=cos(ωrt+φr)
.=(2) However, ωr is the angular frequency of the two-phase oscillator 58, φv is its phase noise, and is time.

The two-phase voltage controlled oscillator mi output 55 a (xssa) which is the output of the two-phase voltage controlled oscillator 54 and the two-phase voltage controlled oscillator second output 551 + (X, b) are each X5s.
a=sin(ωdt±φv) ・(3)X
ssb=cos(ωdt±φv) ・(4
). However, ωd is the first output 55a (Xssa) and the second output 55b (Xss) of the two-phase voltage controlled oscillator 54.
b) is the angular frequency, and φv is the phase control amount. Decoding is in the same order. In the following description, the symbols above the decoding relate to the case of an approaching target signal, and the symbols below the decoding relate to the signal of a receding target.

Switch output 61 (X6
□) is X6. from formula (1). =±5in(ωrt+φr) ・(5
).

The modulator output 57 ('X S?) is calculated as follows: X57=XS! +) ・X5sb+Xs+ ・X5sa
=cos(ωrt+φr)cos(ωdt±φv)±5
in(ω“t+φr)Sin(ωdt±φv)=co
s[ωrt+φr壬(ωdt±φv)]=C08(ωr
t+φr壬ωdt−φv) (6).

The transmission signal 13 (X, 3) and the power divider tjIJ2 output 23b (X2.L+) are X13=X2zb=sin[ωct+φC(t)
] ・(7) becomes. However, ωC is the transmission signal 13 (X
13), and φC is its phase noise. Therefore, the received signal 11 (X, ,) and the receiving antenna output 15 (Xl,) are expressed as Xz=X+5=sin[ωc(t-'r)+φc(t
T)]=sin[ωct±ωdt+φ2+φc(t
T)]...(8) However, T is the delay time from transmission to reception. In addition, in the decoding of ωd in equation (8), +ωd is the outer Doppler angular frequency of the approaching target, -ωd is the negative angular frequency when the target is moving away, and φ2 is the Doppler angular frequency when the radio wave is reflected by the target itself. This is phase noise generated from

The fourth mixer output 33 (X:13) is the power divider second output 23 b (X 2sb) and the modulator output 57 (XS, )
X, , = sin[ωat-ωrt±ωdi+φc(L
)−φr+φv1...(9
).

The tIS5 mixer output 35 (X3S) and the third intermediate frequency amplifier output 37 (X, ,) are the receiving antenna output 15 (X,
) and @44 mixer output 33 (X3.), so Xzs=Xst=sin(ωrt+φZ+Δφ+φr−
φv)...(10) However, Δφ=φc(t-T)-φc(t)...
(11).

The phase term of dog (10) contains the angular frequency ω of the Doppler signal.
Since it does not include d, it is a narrowband signal, indicating that the third intermediate frequency amplifier 36 can be made narrowband.

Is it a Dotsupura signal? 1fJ6 mixer output 39 (X, 9
) and video amplifier output 41 (X4.) are connected to the third intermediate frequency amplifier output 37 (X:17) and the modulator output 57 (X5.
)), so it is made by mixing with
...(12) becomes.

2-phase voltage controlled oscillator first output 55ali - input to second polarity switch 50, second polarity switch output 51 (X5
．． ) is X3. =壬5in(ωdt±φv) −(1
3). In the phase detector 44, the video amplifier output 41 (X4.) is phase detected using the second polarity switch output 51 (X51) as a reference signal, and the phase detector output 45 (
X, 5) is obtained.

X 45” S!n (Δφ+φZ−φv)
-(14) The two-phase voltage controlled oscillator 54 is expressed by the formula (
14) so that the phase detector output 45 (X=s) becomes zero.

In Equation (14), Δφ is the phase noise of the transmission source 20 (corresponding to the distance to the vote, which is a small amount of high-frequency phase noise), and φZ is the phase noise that occurs when the radio wave is reflected from the target. Since the phase noise is generated by itself, equation (14) shows that the transmitter/receiver has extremely low phase noise.Furthermore, equation (14) does not include the phase noise of the two-phase oscillator 58. This is also one of the excellent features of the present invention.

In the synchronous detector 42, a two-phase voltage controlled oscillator second
Using the output 55b (X5.b) as a reference signal, the video amplifier output 41 (X4.) is synchronously detected and the synchronous detector output 43
(X43) is obtained.

X 43” cos(Δφ 1φ2−φv)
- (15) From equation (15), synchronous detector output 43 (X
43) can be used to detect the presence or absence of a signal, so it can be used as a signal to stop or start the sweep oscillator 52 (if a signal is present and cosO=1, the sweep stops).

The basic signal flow has been described, and the equivalent block shown in FIG. 4, which will be described later, is created from this signal flow.

From the above explanation, although the amplifier has one channel, it has two channels.
The principle of the Doppler frequency of an approaching target and the Doppler frequency of a receding target can be tracked by using two polarity switchers 48 and 50.

Next, FIG. 6, which shows the signal flow of the second embodiment of FIG. 5, which is a modification of the eleventh embodiment according to the present invention shown in FIG. 1, will be described.

The third polarity switch output 61 (X'a+) is X'6. as in equation (5). =±5in(ω'rt+φ'r) =(1
6). Two-phase oscillator second output 59b (X'5.b
) is similar to equation (2), X's, b=cos(ω'rt+φ'r) −(
17). Modulator output 57 (X'S7) is expressed by formula (6)
Similarly, X'57 = cos (ω'rt + φ'r + ωdt - φv)
...(18) becomes. The third reference signal oscillator output 83 (X83> is the output of the third reference signal oscillator 82)
L+φm) −(19). However, ω is the third reference signal oscillator output 83 (X, ,
), and φ is the phase noise.

The tenth mixer output 81, which is the output of the tenth mixer 80, is sent to the modulator output 57 (X5.) and the signal output 83 (
X83), so X s + = Co
5(QJ rt+φr壬(ddt-φv)-(20>. However, ωr=ωr-ω1...(21
)φv=φ′r−φ, ...(2
2). Modulator output 57 (L7) of equation (6) and equation (
Since the ptS10 mixer output 81 (X8.) of 20) has the same format, the following explanation is the same as in FIG.

Furthermore, FIG. 8, which is a signal flow diagram of the tItJ3 embodiment in FIG. 7, will be explained. Since the third embodiment in FIG. 7 is a modification of the first embodiment in FIG. Only the differences will be explained.

The second reference signal oscillator 71 (X, ,) which is the output of the second reference signal oscillator 70 is X, , = sin (ω + nt + φ111)
・(23) becomes. However, ω[fl is the angular frequency of the second reference signal oscillator output cuff 1 (X?+), and φm is the phase noise. The seventh mixer output 63 (X6.), which is the output of the jll't7 mixer 62, is the modulator output 57 (XS7.
) and mixed with
φv±φ"0)...(24) However, when decoding ωIff, when mixing in the seventh mixer 62, the frequency term of the sum of the modulator output 57 and the second reference signal oscillator output cuff 1 is used. This shows that either difference frequency term is possible.

Eighth mixer output 65 (X6
s) and the fourth intermediate frequency amplifier output 67 (X,,) which is the output of the fourth intermediate frequency amplifier 66 is X65=X5t
= sin(±ωIIIt+φ2+Δφ±ωdt±φIo
)...(25).

The ninth mixer output 69 (Xi
s) and video amplifier 41 (X, l) are X5s=X4
1=cos(±ωdt+φZ+Δφ)...(26), and the video amplifier output 41 (L+) of equation (12)
Therefore, the following explanation is the same as the embodiment shown in FIG.

FIG. 4, which is an equivalent block diagram of the fjS1 diagram, will be explained. Video amplifier output 4.1(X,,) phase 85(
X, 5) is X8. =Δφ+φ2 (27), and the difference from the integrator output cuff 9 is taken by the adder 72, resulting in the adder output cuff 3 (X, , ).

X73=Δφ 1φ2−φv ・
...(28) Sine generator output cuff 5 which is the output of the sine generator 74 (
X7S) is Xys”5in (Δφ10φ2−φv)
-...(29), which is the phase detector output 45
It will be the same as (X, S). The sine generator output cuff 5 (X, , ) is input to the convolution integrator 76 and becomes the convolution integrator output cuff 7, and is input to the integrator 78 and becomes the integrator output cuff 9, thereby closing the negative feedback loop. This loop has been shown to function well as a phase-locked loop.

(Example) Hereinafter, an example of a phase-locked tracking radar according to the present invention will be described with reference to the drawings.

The principle explanation of the @1 embodiment of the fiS1 diagram has already been explained in f! ,3
The first embodiment shown in FIG. 1 will be further described, although some of the explanation will be made using figures.

The modulator 56 includes a two-phase voltage controlled oscillator first output 55a which is the output of the two-phase voltage controlled oscillator 54, a two-phase voltage controlled oscillator tJfJ2 output 55b, and a two-phase oscillator 58 (
The third polarity switch output 61, which is a signal whose polarity has been switched by the Pt53 polarity switch 60, of the two-phase oscillator first output 59a, which is the output of the 2-phase oscillator (working as a reference signal oscillator), and the two-phase oscillator second output 59b are input. The output signal becomes the modulator output 57, and is input to the fourth mixer 32 and the sixth mixer 38 as a reference signal.

A transmission source output 21, which is the output of the transmission source 20, is input to the power divider 22, becomes the power divider first output 23a, and is transmitted by the transmitting antenna 12 toward the target. The power divider second output 23b is connected to Pt54 along with the modulator output 57.
The mixture is mixed in the mixer 32 and becomes the fourth mixer output 33.

The received signal 11 is received by the receiving antenna 14, becomes the receiving antenna output 15, is mixed with the fourth mixer output 33 in the fifth mixer 34, becomes the fifth mixer output 35, and is sent to the third intermediate frequency amplifier 36. It is input to the fJS3 intermediate frequency amplifier output 37, mixed with the modulator output 57 in the sixth mixer 38 to become the sixth mixer output 39, and input to the video amplifier 40 to become the video amplifier output tl.

The other output of the two-phase voltage controlled oscillator first output 55a is input to the second polarity switch 50 and becomes the ptS2 polarity switch output 51. The video amplifier output 41 is phase-detected using the second polarity switch output 51 as a reference signal, becomes the phase detector output 45, is input to the low-pass filter 46, becomes the low-pass filter output 17, and becomes the phase detector output 45. The signal is input to the 1-polarity switch 48, becomes the first polarity switch output 49, and is input to the 2-phase voltage controlled oscillator 54.

The other video amplifier output 41 is connected to a synchronous detector 42t using the two-phase voltage controlled oscillator second output 55b as a reference signal.
Here, it is synchronously detected and becomes the synchronous detector output 43, which is input to the sweep oscillator 52. However, when the frequency and phase match and a DC signal is output to the synchronous detector output 13, the sweep of the sweep oscillator 52 is performed. is stopped, and the DC signal of the sweep oscillator output 53 is held and input to the two-phase voltage controlled oscillator 54.

The second embodiment shown in FIG. 5 will be described (the same parts as in FIG. 1 are given the same numbers). FIG. 6, which is a principle diagram of the second embodiment shown in FIG. 5, has already been explained. tS
Since FIG. 5 is a modification of FIG. 1, only the differences from the first embodiment shown in FIG. 1 will be described.

In the tenth mixer 80, the modulator output 57 and the PI3 reference signal oscillator output 8 which is the output of the third reference signal oscillator 82
3 is mixed and becomes the tenth mixer output 81. below,
The explanation is the same as in FIG.

The third embodiment of fjS7 diagram (the same parts as in Figure 151 are given the same numbers) will be explained.
FIG. 8, which is a principle diagram of the third embodiment, has already been explained, and since the third embodiment shown in FIG. 7 is a modification of the first large embodiment shown in FIG. 1, it is similar to the first embodiment shown in FIG. I will only discuss the differences between

In the seventh mixer 62, the modulator output 57 and the second basic parrot signal oscillator output cuff 1 are mixed to form a seventh mixer output 63 which can be either the sum or difference frequency, and the third intermediate frequency amplifier It is used as a reference signal for frequency converting the output 37. The third intermediate frequency amplifier output 37 and the seventh mixer output 63 are mixed in the eighth mixer 64 to become the eighth mixer output 65, and are amplified in the fourteenth intermediate frequency amplifier 66 to produce the fourth intermediate frequency amplifier output. 67, f
52 reference reference oscillator output cuff 1 is used as a reference signal and mixed in a ninth mixer 68 to become a ninth mixer output 69.

The following explanation is the same as in FIG.

Next, a supplementary explanation of the embodiment will be given. Although the transmitting antenna 12 and the receiving antenna 14 have been described separately in each embodiment shown in FIG. 1, the transmitting antenna 12 and the receiving antenna 14 may be used in common.

Further, in each embodiment, an injection-locked oscillator may be used instead of the two-phase voltage controlled oscillator and its associated circuit.

(Effects of the Invention) Various excellent effects of the present invention are summarized as follows.

(A) The third intermediate frequency amplifier 36 is a narrow band Doppler amplifier.
Since it is a date, the resolution of the target speed is high.

(b) The combination of circuits reduces the inherent phase noise of the oscillator, and furthermore, it is achieved without using an expensive local oscillator that is close to the frequency of the transmission source.

(c) The video amplifier output 41 folds positive and negative clutter and Doppler signals from moving targets and fixed targets.

As mentioned above, since only the signal of the moving target is filtered through the narrow band third intermediate frequency amplifier 36, high sensitivity and high resolution are achieved.

(e) Since the positive and negative speeds of a moving target can be detected with one channel, the economical effect is great.

(E) Since the signal is detected by the synchronous detector 42,
It is highly sensitive and is not affected by noise.

(l) Because of the filtering effect of the video amplifier 40 and the fact that the two-phase voltage controlled oscillator 54 does not oscillate near zero frequency, the self-synchronization current 3L due to direct looping of the transmitted signal 13, which tends to occur in this type of receiver, is Hard to happen.

(i) Since the video amplifier 40 is in the loop, the effect of removing noise around zero Doppler is great.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a first embodiment of a phase-locked tracking radar using a phase-locked loop according to the present invention, Fig. 2 is a block diagram of a conventional Doppler radar, and Fig. 3 is a block diagram of Fig. 1. 4 is a mathematical representation of the explanatory diagram in FIG. 13, FIG. 5 is a block diagram of the second embodiment, and FIG. 6 is a diagram of the second embodiment. An explanatory diagram showing the flow of signals in the block diagram, f:JSV diagram is a block diagram of the third embodiment, and FIG. 8 is an explanatory diagram showing the flow of signals in the block diagram of FIG. 11... Reception signal (X,,), 12... Transmission antenna, 13... Transmission signal (X,,), 14... Receiving antenna, 1... Receiving antenna output (Xl,) , 16
...first mixer, 17...first mixer output, 18.
...first intermediate frequency amplifier, 19...first intermediate frequency amplifier output, 20...transmission source, 21...transmission source output, 2
2...Power divider, 23a...Power divider fjIJ
1 output, 23b...Power divider 2nd output, 24...
First local oscillator, 2, . . ., first local oscillator output, 26
... f: tS2 mixer, 27... second mixer output,
28...12 intermediate frequency amplifier, 29...fJS2 intermediate frequency amplifier output, 30...3rd mixer, 31...
3rd mixer output, 32...4th mixer, 33...4th mixer output (X, 3), 34...5th mixer, 3...ttS5 mixer output (X3s ), 36...3rd
Intermediate frequency amplifier, 37... third intermediate frequency amplifier output,
38... Sixth mixer, 39... f: tS6 mixer output (X3.), 40-... Video amplifier, 41... Video amplifier output (X,,), 42... Synchronous detection vessel, 4
3... Synchronous detector output (X43), 44... Phase detector, 4... Phase detector output (X4.), 46...
・Low pass filter, 47...Low pass filter output, 4
8...First polarity switch, 4''9...First polarity switch output, 50...Second polarity switch, 51...Second polarity switch output (X7.), 52 ...Sweep oscillator, 53.
...Sweep oscillator output, 54...2-phase voltage controlled oscillator, 55a...2-phase voltage controlled oscillator first output (X 5
sa), 55b...2-phase voltage controlled oscillator second output (
X, 5b), 56...Modulator, 57...Modulator output (XS7), 58...2-phase oscillator, 59a...2
Phase oscillator first output (X 5sa), 59b...2 phase oscillator! @2 output (X 5sb), 60...Third polarity switch, 61...Third polarity switch output (X,,),
62...tjl, 7 mixer, 63...7th mixer output (X63), 64...! @8 mixer, 6... 8th mixer output, 66... 4th intermediate frequency amplifier, 67...
...Fourth intermediate frequency amplifier output (X6.), 68...f
jIJ9 mixer, 69...9th mixer output (X6.)
, 70... Second reference signal oscillator, 71... Second reference signal oscillator output (X?+), 72... Adder, 73...
...Adder output (X7.), 74...Sine generator, 7,
... Sine generator output (X7S), 76... Convolution integrator, 77... Convolution integrator output, 78... Integrator,
79 -- Integrator output, 80 -- 10th mixer, 81
...10th mixer output (X, l,), 82...3rd
Reference signal oscillator, 83...Third reference signal oscillator output (
Xs3), 8, ... Video amplifier output phase (X, 5
), ANT...antenna, MIX...mixer, IF
...Intermediate frequency amplifier, V, AMP...Video amplifier, 5DET...Synchronous detector, PSD...Phase detector, LPF...Low pass filter °, ±.壬...Polarity switch, 5WEEP...Sweep oscillator, ■
CO: 2-phase voltage controlled oscillator, MOD: modulator, O20: oscillator.

Claims (1)

[Claims] (1) In a phase-locked tracking radar that emits radio waves from a transmitting antenna to a moving target and tracks the reflected radio waves,
The phase of the reference signal required for the first frequency conversion, which is equipped with a receiver of two or more frequency conversion methods and is generated from the signals of the reference signal oscillator and the two-phase voltage controlled oscillator or the injection locking oscillator, is expressed by the following formula: X_3_3=sin [ωct−ωrt±ωdt+φc(
t)-φr+φv] (where ωc: angular frequency of the transmission signal, φc(t): phase noise of the transmission signal, ωr: angular frequency of the reference signal oscillator, φ
r: phase noise of the reference signal oscillator, ωd: angular frequency of the two-phase voltage-controlled oscillator or injection-locked oscillator, φv: phase control amount, t: time), and furthermore, the signal from the reference oscillator. A phase-locked tracking radar characterized in that the Doppler signal is tracked by performing a second frequency conversion using the second frequency converter, obtaining the Doppler signal, and inputting the Doppler signal to the two-phase voltage controlled oscillator or the injection-locked oscillator.