JPS5850482A - Radar device - Google Patents

Abstract

PURPOSE:To eliminate false echoes by providing a function of discriminating the coincidence of the distance of signals at every sweep. CONSTITUTION:Transmission signal generating circuits 1 and 2 generate a sub-transmission pulse and a main transmission pulse according to a trigger signal outputted from a timing control circuit 14, and these two kinds of signals are emitted into the air via a signal-composing circuit 3, a power amplifier 4, a transmission-reception change-over switch 5 and an antenna 6. Echo signals from a reflecting object are inputted in a correlation processing circuit 13 via the antenna 6, the transmission-reception switch 5, a reception amplifying circuit 7, matched filters 8 and 9, detection circuits 10 and 11, and a signal switching circuit 12. The correlation processing circuit 13 performs the detection of correlation as to whether or not the positions of the signals inputted currently accord with those memorized in the past, thus prohibiting the output of false echoes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse radar device for the purpose of searching and monitoring aircraft, refueling, etc., and particularly relates to a device having characteristics in the temporal arrangement of transmitted pulses and signal processing on the receiving side.

Pulse compression technology is one way to improve radar detection performance over long distances. This method improves the detection ability by increasing the average transmission power by increasing the pulse width of the transmission signal, instead of increasing the peak power value of the transmission signal. In this case, in order to prevent distance resolution from deteriorating due to an increase in pulse width, special modulation is applied within the transmission pulse width, and pulse compression is performed on the received signal on the receiving side.

On the other hand, such a pulse compression radar VC transmits a wide pulse width as described above, and since reception is impossible during transmission, the short-range radar coverage is limited to a distance corresponding to the transmission pulse width. There are drawbacks to sacrifice.

Therefore, in a radar system that requires a wide range of radar coverage from short to long distances, as shown in Figure 1, a short-range search signal is placed in front of the expanded transmission pulse for pulse compression (hereinafter referred to as the main transmission signal) A. A composite pulse transmission method has been proposed in which a short pulse width transmission signal (hereinafter referred to as a sub-transmission signal) B is added and the signal is transmitted as a set of pulse signals for each radar repetition (hereinafter referred to as a sweep) T.

In this case, the reflected echoes from the set pulse signal constituted by these two types of pulses are received by the same antenna. Figure 2 (a) is the transmission signal waveform, (b) is the reception output of the sub-reception system, (C) is the reception output of the main reception system, (d
) shows the output after switching arrangement of both receiving powers. However, there is a case where a reception echo due to the sub-transmission signal which is two times ahead exists in the long-distance reception system (hereinafter referred to as the main reception system), and an unnecessary pseudo signal A is generated in the main reception system. In Figure 1, B
is a reflected echo from object A, C is a reflected echo from object B, T1 is a short-range reception area, and T2 is a long-range reception area. In order to prevent this spurious signal from leaking into the main receiving system, generally the carrier frequencies of the main transmitting signal and the sub transmitting signal are slightly shifted, allowing frequency selection in the receiving system. There are ways to separate signals by their frequencies.

However, in the case where only one frequency is allowed as the usage frequency assigned to the radar system, the above-mentioned frequency separation is not possible. Even in this case, the response of the matched filters in each receiving system differs due to the difference in the properties of both signals, so although there is some selection function, practically sufficient separation cannot be obtained.

In other words, in the composite pulse transmission method using the pulse set shown in FIG. 1 as described above, interference of received signals between the pulse sets, that is, echoes reflected by the sub-transmission signals mix into the main receiving system. In the prior art, the interval between the set pulses is a constant value for each sweep, and the position of the pseudo echo that leaks into the main receiving system is also constant for each sweep.

Therefore, the present invention solves the problem of l'+J11? of this set of pulses. This method focuses on the fact that if the distance position of the pseudo echo that appears in the main receiving system changes every sweep, the distance position of the pseudo echo that appears in the main receiving system will change every sweep.

In other words, while a normal received signal appears at approximately the same distance for each sweep, such pseudo echoes appear at different distances for each sweep. By providing the correlation unit [l on the receiving side, it is possible to distinguish between these pseudo echoes and to eliminate them.

The present invention provides a radar system that performs composite pulse transmission 41 at one type of carrier wave frequency in this way and is equipped with a receiving system corresponding to each pulse waveform that constitutes a set of pulses.
This problem is solved by combining the method of changing the interval between the set pulses for each sweep and the range correlation processing function for the received signals on the receiving side to solve the problem of pseudo echoes caused by the leakage of the received signals between the set pulses. It is.

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

FIG. 3 shows a basic block diagram of an embodiment of a radar device 5- which uses a pulse set composed of two types of pulse signals according to the present invention. In the figure, a transmission signal generation circuit (1) and a transmission signal generation circuit (2) 2 generate a sub-transmission pulse signal and a main transmission pulse signal, respectively, in response to a trigger signal sent from a timing control circuit 14. These two types of signals are converted into a set pulse signal, that is, a composite pulse transmission signal, by the signal synthesis circuit 3, and the power amplifier 4. The signal is radiated into the air via a transmitting/receiving switch 5 and an antenna 6.

On the other hand, the echo signal from the reflecting object is the antenna 6. After being amplified through the transmitting/receiving switch 5° and the receiving amplifier circuit 7, the signal is divided and supplied to a matched filter (1) 8 and a matched filter (2) 9, respectively. A matched filter is a bandpass filter having a passband characteristic that provides an optimal reception system for sub-transmission signals, and together with the detection circuit 10 constitutes a short-distance reception system (sub-reception system). Further, the matched filter (2) 9 is a special filter having a pulse compression function corresponding to the main transmission signal, and together with the J detection circuit 11 constitutes a long-distance receiving system (main receiving system).

The video signals from these receiving systems are selected by the signal switching circuit 12 for the required range, and after the video timing is adjusted, they are sent to the correlation processing circuit 13. The correlation processing circuit 13 stores the distance information of the received signal over the past several sweeps, and performs correlation detection to determine whether the current position of the manually input signal matches that stored in the past, and detects uncorrelated input signals. That is, it has a function of prohibiting the output of pseudo echoes.

The above will become clearer if you compare and refer to FIGS. 4 and 5. FIG. 4 shows the appearance of pseudo echoes when the interval between bare pulses is constant, and FIG. 5 shows the appearance when the interval between set pulses is changed for each sweep. Figure 4(a) shows the composite pulse transmission waveform.

(b) shows the selected and arranged received video, where L is the spacing of the set of Hals, A is the pseudo echo, and L is the location of the pseudo echo. From this figure, it can be seen that the interval between the set pulses is constant for each sweep, and the position of the pseudo echo that leaks into the main receiving system is also constant for each sweep. 5(a) shows the composite pulse transmission waveform, FIG. 5(b) shows the selectively arranged received video, and FIG. 5(C) shows the output video after correlation processing, and other symbols are the same as in FIG. 4. From this figure, it can be seen that if the interval between the set pulses is changed for each sweep (1, 12), the distance position of the pseudo echo that appears in the main receiving system will change for each L2 or sweep, so the above correlation processing Echo is removed.

As explained above, the present invention makes it possible to utilize the range correlation of pseudo echoes by changing the time interval of the composite pulse for each sweep, and is configured in combination with the range correlation processing function provided on the receiving side. In particular, it can be expected to have the effect of eliminating the false echo caused by υ.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a transmission waveform of a composite pulse transmission system using a set pulse composed of two types of pulse signals,
FIG. 2 is a diagram showing an example of the waveform of a received signal resulting from the composite pulse transmission of FIG. 1, and FIG. 3 is a diagram showing one 91J of the reader device using composite pulses. FIG. 4 is a diagram showing how pseudo echoes appear when the interval between paired pulses is constant, and FIG. 5 is a diagram when the interval between paired pulses changes for every sweep according to the present invention. 1.2... Transmission signal generation circuit, 3...
Signal synthesis circuit, 4... Power amplifier, Death...
- Transmission/reception switch, 6... Antenna, 7. Receiving amplifier circuit, 8, 9... Matched filter, 10.
11... Group detection circuit, 12... Signal switching circuit, 13... Correlation processing immediate circuit, 14... Timing control circuit. 9- Bud 1 time l-T+ +-72□ Homare 2 Kuni

Claims (1)

[Claims] In a radar device that divides the radar coverage area in the distance direction and transmits two or more types of pulse signals prepared corresponding to each area as a set pulse at each radar repetition time,
A means for transmitting the set pulses by changing the interval between them randomly or in a predetermined combination every 1 tz-da repetition, and a receiving signal regarding the distance for each sweep of the receiving No. 4 corresponding to these set pulses; By providing a range correlation processing means that performs correlations for comparison with received signals of past sweeps and does not output uncorrelated signals, it is possible to prevent problems caused by reflected echo signals leaking between pulse sets. A radar device characterized by preventing