JPS63144279A - Radat system - Google Patents

Abstract

PURPOSE:To suppress unnecessary waves such as a 2nd turn-around signal by switching the phase of a radar-sent signal, pulse by pulse, and also performing phase detection based upon the sent wave at the time of reception, and performing coherent integration processing. CONSTITUTION:A sent intermediate frequency signal generated by a coherent oscillator 1 is modulated by a pulse modulator 2 with a transmission trigger signal from a transmission controller 4 and then led to a frequency converter 3. A pulse-modulated high-frequency signal of the sum frequency of said signal and a local signal from a local oscillator 5 is amplified 10 in terms of power and radiated from an antenna 12. A received reflection wave is amplified 13 at a high frequency and inputted to a phase detector 14. The phase detector 14 while maintaining the phase relation between a received high-frequency signal and the local signal outputs a received intermediate frequency signal whose frequency is equal to the difference between both frequencies. This signal is amplified 15 at the intermediate frequency and then inputted to a mixer 16 togetyher with a sent intermediate-frequency signal from the oscillator 1, and the output is inputted as a bipolar video signal to an integral processor 17 to perform the coherent integration processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to pulse radar, and particularly to improvement of unnecessary wave suppression performance by coherent integration processing.

[Conventional technology]

Conventionally, as this type of unnecessary wave suppression radar system, there has been a system (% Kosho 52-45479 interference signal removal radar apparatus) in which the time correlation of unnecessary received waves is suppressed by changing the transmission pulse interval to deteriorate the time correlation of the unnecessary received waves.

In these radars, for a target reflected signal within a fixed distance range that is received within one sweep from one transmitted pulse to the next transmitted pulse, a reflected signal corresponding to the transmitted pulse wave one week earlier (long-distance Second-Time-Aro signal from target; Second-Time-Aro
Interfering radio waves from other radio wave application devices were thought to be the cause. FIG. 5 shows the temporal relationship between the transmission pulse train of the conventional unwanted wave suppression radar system and the second-time answer signal reception pulse train. As shown in the figure, the transmission pulse t! , 21 [pulse intervals T1 and T0 are repeated for each pulse]. Regarding the reflected wave for this transmitted pulse, the interval between the transmitted pulse and the received pulse will be a constant value for targets that are received within the subsequent 1 sweeps. On the other hand, in the received pulse train for the second time 7 land signal that is an unnecessary wave, the elapsed time from the corresponding transmitted pulse before the sweep is a constant value to (=2R/C, R: The distance from the radar to the target, C: speed of light), but the elapsed time from the previous transmitted pulse in the same sweep as the received pulse is tl (
=to-Tz) and tz(to-'h). Therefore, the elapsed time from the transmission pulse immediately before the target reception signal is compared between multiple sweeps, and if they show the same value, the true target signal is output as is, and
If each pulse has a different value, it is removed as a second time-around signal which is an unnecessary wave. By performing such processing, it is possible to prevent interference from interference radio waves from other devices, not only from asynchronous interference waves, but also from time-synchronized interference waves when the device is sufficiently far away. Unwanted waves are also removed for received waves in the time domain whose pulse wave arrival time is similar to the second time around received wave shown in FIG.

[Problem that the invention seeks to solve]

In the conventional unwanted wave suppression radar method described above, it is necessary to measure the elapsed time from the transmitted pulse for each pulse of the received pulse train, so it is necessary to determine the presence of a target signal using only a single pulse. No. 01188 required a large value for the noise ratio. For this reason, it has the disadvantage that it cannot employ the integral processing that ordinary radars employ to detect targets with small signal levels.

[Means for solving problems]

In order to solve the above problems, the radar system of the present invention is a coherent pulse radar in which the phase relationship of the radar transmission waves is maintained between successive transmission pulses. , means for phase-detecting the radar reception pulse signal so that the phase of the corresponding transmission pulse wave becomes a reference, and coherent integration processing means for the reception pulse train after the phase detection.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram showing one embodiment of the present invention.

In FIG. 1, the transmission intermediate frequency signal generated by the coherent oscillator l is sent to the pulse converter V4 2, and after being modulated by the transmission trigger signal from the transmission controller 4, frequency conversion is performed. Guided by Vessel 3.

- The local signal generated by the local oscillator 5 is guided to the switch 6, and is alternately switched to the terminal 7 or 8 by a switching signal from the transmission controller 4 for each transmission pulse. When the local signal tone is switched to terminal 7, it is not subjected to phase delay, and when it is switched to terminal 8, the phase shifter 9 receives a phase M ground of only Δφ. 1 frequency & converter 3. The frequency converter 3 receives the transmission intermediate frequency signal and the local signal as input, and outputs a pulse modulated high frequency signal having a frequency equal to the sum of the image frequencies. The high frequency signal is then passed through a power amplifier l.
The power is amplified at O, guided to the antenna 12 via the transmitter/receiver switch l, and radiated into space as a radar transmission pulse. At this time, the cylindrical frequency signal is generated by a highly stable coherent oscillator l.
Since the output signal of the local oscillator 2 and the output signal of the local oscillator 2 are used as a stock, it is a coherent high-frequency signal in which the phase relationship between the transmitted pulses is preserved.

Next, the reflected wave from the radar target is received as a received high-frequency signal via the airborne Mlz, is switched to the receiving side by the transmitter/receiver switch 11, is guided to the high-frequency amplifier 13, and is amplified. , are input to the phase detector 14 together with the local signal. The phase transverse transducer 14 outputs a received intermediate frequency signal equal to the frequency of the difference between the wave numbers of both parts while preserving the phase relationship between the received high frequency signal and the local signal, and after this received intermediate frequency signal is amplified by the intermediate frequency amplifier 15. , are input to the mixer 16 together with the transmission intermediate frequency signal from the coherent oscillator 1. The mixer 16 generates a bipolar self-video signal having a positive or negative voltage depending on the phase difference of the meat input signal, and then the video signal is input to the integral processor 17. After accumulating a predetermined number of successive video signals, the integral processor 17 performs coherent integral processing and outputs the integrated signal for subsequent processing.

Next, Fig. 2 shows the transmission pulse trains Ps, Pg, ... transmitted by the radar of the system shown in Fig. 1, and the received pulse train (1) Ss.
, Sx, ..., and received pulse train (2) FO*" r
. . is a diagram showing the temporal relationship between time t1. t2
The target reflected waves of the transmitted pulses Ps, Pt,... are in the Unambiguous Range.
), the received pulse (t) SttS depth *
..., and the distance uncertainty region (Ambiguou
For targets in the ss Range), the reception pulse (23Flt
Fs*... indicates that each is received as Fs*....

Now, suppose that the switch 6 in FIG. 1 is connected to the terminal 7 from time t1 to 1g, and connected to the terminal 8 from time t3 to t3, and thereafter is switched alternately every time a pulse is transmitted.
Transmission pulse PI, voltage corresponding to P intention Vt eVz I
According to the d complex demonstration, Vt=AeJ(ωt+α) Vz=Aej(ωt+α−Δφ) Here, A==Signal amplitude ω=Transmission direction angular frequency=Time α==Phase of signal wave with respect to a certain reference value Hereinafter, the transmission pulses Ps, P4,...
Regarding the voltages Vs, Va, ... corresponding to
s = Vs =... Va = V4 =... It is expressed by the same formula as curvature.

On the other hand, received pulses (1) sl, Ss, Ss,...
The voltage X 1eXzeX''# corresponding to .

X*=Xs= ・-= Be J ("t+α-β
)Xz=Xa=...= Be J (ωt+α−
β) Here, B: Reception amplitude and voltages corresponding to the reception pulse (2) Fl, Fz, Fs, ... It is expressed by the following equation, where r is the delay phase shift corresponding to the distance.

Y1=Ys=-=CeJ(ωt+α-r)Y2=Y4=
, -=Cej(ωt+α-Δφ-r) where, C: reception amplitude Here, consider the input signal to the integration process @17 of reception pulses (1) and (2) corresponding to each transmission pulse.

For the received pulses Sl, Ss...-, the switch 6 is connected to the terminal 7.
local signal (phase is V!, Vx
, Vs ,...) Since K is phase detected,
Input signal X' to the integral processor 17! ,XI,.../
It is expressed by the following equation with reference to the equations of dXs and Vx.

X'l=X'3 =.-=D e jβ However, D is a relative amplitude in consideration of each af loss and gain, and as for the phase, a relative value determined by the configuration of the receiving system is omitted. Next, the received pulse 82°S a,... is a local signal with the switch 6 connected to the terminal 8 (the phase is V
(same as x=Va=...), the input signals to the integral processor 17 are X'g, X'a,
... is expressed by the following equation with reference to the equations X2 and (2).

X'z = X'4 = l)6 Jβ, that is, X'l
, JC'2, X'3,... are all in phase and have the same complex size, and X'
When drawn as a S and X'2t-vector diagram, it is shown in FIG. 3(a).

On the other hand, received pulse F1. In Fs, . . . , the local signal switching is reversed from that of the received pulse train (1), so the input signals Y'l, Y's to the integrator 17 are
.

... is expressed by the following formula with reference to Yl and ■
's = Y's= ・-= E e J ('-Δφ)
Note that E is the relative width in consideration of each side loss and gain, and as for the phase, the relative value determined by the configuration of the receiving system is omitted. Next, the received pulses Fx, F4,...
・ is similarly applied to the integral processor 17 and is expressed by the following equation.

Y'x=Y'a=1. = E 1!1 j (r+
Δφ) Above Y's, Y's,... and Yf, Y'
Looking at the equations a, . . . , it can be seen that the phase alternately changes by ±Δφ for each received pulse. Now, if we set Δφ = π/2 and draw a vector diagram with e'' f: Y'l and Y'* t-vector diagram, we get Figure 3 (b). Figure 3 (IL)
, (b) t- Referring to, when coherent integration processing is performed in the same phase, the integration results are added in the received pulse train (1) corresponding to (&)K in Fig. 3, and the received pulse train corresponding to Fig. 3 (b) In (2), the integration result is canceled and becomes 0 (when the number of integration pulses is 2n (n = integer))
It can be seen that the second time-around signal, which is an unnecessary wave, is suppressed.

Regarding synchronous interference waves from other radio wave application devices, a similar suppression effect can be expected when the interference waves are received from a distance with a delay of one sweep.

As a result, the effect of integration processing on the normal target reflected wave t-
It becomes possible to suppress unnecessary waves while ensuring the same.

In the first embodiment described above, the phase switching period of the local signal was explained as 2, but next, the second embodiment in which the switching period was 3 was explained.
An example will be described. Assuming that the phase of the local signal in this case is repeated as a period of 0→2π/3→O1, as in the case of the first embodiment, the received pulse within the same sweep as the transmitted pulse , all the input signals to the integral processor 170 are in phase] FIG. 4 (
→ becomes a vector diagram. Regarding the received pulse in the sweep adjacent to the sweep corresponding to the transmitted pulse, the phase of the integral processing can input signal is rotated, resulting in the vector diagram shown in FIG. 4(b). Therefore, if coherent integration processing is performed in the same phase, unnecessary waves such as second time around signals and l-sweep delayed synchronous interference waves are suppressed.

Furthermore, in general, the phase switching period of the local signal is 2,
It is possible to configure not only 3 but also 4 or more, and the set of switching phases is not limited to the above embodiment, but since the input signal to the integral processor 17 is always in phase with respect to the target reflection signal in the definite region,
Since a suppression effect due to integration can be obtained if the switching phase causes vector rotation in the input signal of the integration processing unit, various practical phase combinations are possible.

〔Effect of the invention〕

As explained above, the present invention eliminates the need for a second time-around signal, etc. by performing coherent integration by switching the phase of the radar transmission wave for each phase and performing phase detection based on the transmission wave at the time of reception. It has the effect of suppressing waves.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the temporal relationship between a transmitted pulse train and a received pulse train, and Fig. 3-
is a vector diagram showing the phase relationship of the signals before integration processing, the fourth
The figure is a vector diagram similar to FIG. 3 for other embodiments,
FIG. 5 is a diagram showing the temporal relationship between a transmission pulse train and a reception pulse train in a conventional unnecessary wave suppression method. l...Coherent oscillator, 2...Pulse modulator, 3...Frequency converter, 4...
...Transmission controller, 5...Local oscillator, 6.
...Switch, 9...Phase shifter, ll...
...Transmission/reception switch, 12...Antenna, 14.
...°°・Phase detector, 16...Mixer, 1
7...Integrator.

Claims (1)

[Claims] In a coherent pulse radar in which the phase relationship of radar transmission waves is maintained between successive transmission pulses, there is a means for changing the transmission wave phase for each transmission pulse, and a means for changing the transmission wave phase for each transmission pulse, and a means for changing the phase of the radar reception pulse signal with respect to the phase of the corresponding transmission pulse wave. What is claimed is: 1. A radar system comprising: means for performing phase detection such that the phase is detected; and coherent integration processing means for the received pulse train after the phase detection.