JPH0713657B2 - Bistatic radar device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radar installed on the ground, on board, on board, etc. for detecting an aircraft, a ship, etc., and in particular, a transmitter station and a receiver station are separated. The present invention relates to a bistatic radar device that is installed afterwards.

[Conventional technology]

In general, a bistatic radar device can detect only a target existing in a spatial area where a transmission beam and a reception beam intersect. Therefore, in order to effectively utilize transmitted energy to search a space, one possible method is, for example, the publication “Radar Handbook” (MISkolnik, “Rader Hankbook”, McGraw) published by McGraw-Hill, Inc. in 1970. Hill,
Inc.1970), pp.36-14 to pp.36-15, there is a method of simultaneously forming a large number of multi-beams so that the receiving side covers the entire irradiation area of the transmitting beam. .

However, this method has a drawback in that when the distance between the transmitting and receiving stations is large or the search area of the radar is large, an extremely large number of receiving beams are required and the device scale becomes unrealistic.

Therefore, in the past, for example, “E.Hanle,“ survey of bistat radar ”by E. Hanle, published in 1986 in EIE Proceedings, was published.
ic and multistatic radar ", IEEE Proceedings Vol.13
3, Part F, No.7, 1986), pp.592 to 594, "pulse chase" that scans the receive beam at high speed according to the propagation of transmit energy in the transmit beam. There was a method called.

FIG. 5 is a system diagram showing an example of the configuration of this pulse chase system. In FIG. 5, 1 is a transmitter, 2 is a transmission antenna, 3 is a transmission beam controller for generating a transmission beam scanning signal, and 4 is a transmission beam controller. Is a target, 5 is a receiving antenna, 6 is a receiving beam controller for generating a beam scanning signal for high-speed scanning of a receiving beam, 7 is a digital beam former,
Reference numeral 8 is a signal processor that performs pulse compression processing, Doppler processing, etc., 9 is a data processor that extracts a target from the received signal, and performs position locating and tracking processing, and 10 is a display device.

Next, the operation will be described.

In the transmitting station, the transmitting signal generated by the transmitter 1 is radiated into space by the transmitting antenna 2. Here, the beam formed by the transmission antenna 2 sequentially scans a required search space based on a beam scanning signal generated by the transmission beam controller 3. If the target 4 is in the transmission beam, the reflected signal from this is received by the receiving antenna 5 of the receiving station. At this time, the reception beam scans the irradiation area of the transmission beam at high speed according to the propagation of the transmission signal, as shown in FIG. The scanning speed of the reception beam can be expressed by the following equation.

Where −∂φ _R / ∂t is the scanning angular velocity of the reception beam, c
The light beam, b is the distance between the receiving station R and the transmitting station T, the angle between the baseline ▲ ▼ and transmission beams connecting the receiving station and phi _T transmitting station, phi _T is also formed between the base line and the receive beams It is a horn. As shown in the equation (1), since the scanning speed of the reception beam depends on the directivity angle φ _T of the transmission beam,
The transmission beam scanning signal generated by the transmission beam controller 3 of the transmission station is transmitted to the receiving station, and the reception beam controller 6 generates a reception beam scanning signal according to the equation (1). Based on this scanning signal, the digital beam former 7 digitally combines the reception signals from the respective elements of the reception antenna 5 to form a desired reception beam.

The principle of digital beamforming is described in, for example, H. Steyskal, "Digital Beamforming," published by H. Steiskall in 1987 in the magazine "Microwave Journal".
Antennas, An Introduction ", Microwave Journal, Janua
ry 1987, pp107-pp.124), etc.
The description is omitted here.

The signal received in this way is subjected to pulse compression processing, ranging processing, moving target detection processing for crack suppression, Doppler processing such as pulse Doppler processing, etc. in the signal processor 8 as necessary, and then data The processor 9 performs extraction of the target signal, position location, and tracking processing. In addition,
In addition to the result of the ranging process, information on the reception beam directivity angle from the reception beam controller 6 is usually used for position location. These processing results are displayed on the display 10.

Since the conventional method described here scans one reception beam, it is necessary to widen the reception beam width to some extent in order to search the transmission beam irradiation area without exception. This will be described with reference to FIGS. 7 and 8.

The first constraint on the receive beamwidth is due to the transmit beamwidth. As shown in FIG. 7, the locus of the target position received by the receiving station R at the same time is an ellipse with the transmitting station and the receiving station as the focal points. The point where the transmit beam crosses this ellipse is A,
Assuming B, the receiving beam width needs to be wider than the angle at which these two points A and B are expected. If the minimum receiving beam width obtained from this constraint is θ _R1 , θ _R1 is given by the following equation.

Here, θ _T is a transmission beam width, θ _T is an angle formed by a transmission beam with a baseline connecting the transmission station and the reception station, and θ _R is an angle formed by this baseline with the reception beam. As can be seen from the equation (2), it is necessary to widen the reception beam width in proportion to the transmission beam width.

The second constraint on the receive beam width is due to the transmit pulse width. FIG. 8 (a) is a schematic diagram showing a transmission / reception beam relationship, and FIG. 8 (b) is a timing chart of a received signal. Now, suppose that the reflected signal P _A from the target A in the transmission beam emitted from the transmission station T in FIG. 3A starts to be received at the reception station R at time t _A. When the transmission start time is t = 0, t _A is expressed by the following equation using the symbol of FIG.

Here, c is the luminous flux, where τ is the transmission pulse width or the transmission frame time in the case of the cw radar, the reflected signal P _A from the target A is from time t _A to (t _Since it will be received in the time zone of ( _A + τ), it is necessary to irradiate the target A with the reception beam during this time. Next, consider a target B located at the position given by the following equation within the same transmission beam.

▲ ▼ + ▲ ▼ = ▲ ▼ + ▲ ▼ + cτ ...
(4) reflected signals P _B from the target B, as shown in FIG. (B), since it is received in the time period of time t _B ~ (t _B + tau), at time t _B receive beams target B Have to start irradiating.
Here, using the equation (4), Therefore, in other words, at time t _A + τ (= t _B ), it is necessary that the reception beam irradiates the target A and the target B at the same time.

When this relationship is shown by an equation, the required reception beam width θ _R2 is given by the following equation.

Equation (6) indicates that the longer the transmission pulse width τ, the wider the reception beam width.

Received beam width θ that satisfies both of these two constraints
_R can be written as

θ _R = max (θ _R1 , θ _R2 ) (7) From this, it is understood that the receive beam must be wide to some extent when the transmit beam width is wide or the transmit pulse width or the transmit frame time is long.

In the above description, the transmission antenna 2 is a phased array antenna that performs electron beam scanning for convenience.
This may be considered as an antenna that mechanically performs beam scanning, and in this case, the transmission beam controller 3 may be read as a detector of the beam pointing angle. Similarly, although the receiving antenna 5 is a digital beam forming antenna with a digital beam former 7, it is considered to be a phased array antenna that electronically performs beam scanning by controlling the phase of each antenna element. But it doesn't matter.

[Problems to be Solved by the Invention]

Since the conventional bistatic radar is configured as above, if the transmission beam width is widened or the transmission pulse width (in the case of pulse radar) or the transmission frame time (in the case of cw radar) is lengthened, Since it is necessary to widen the reception beam width, there are problems that the detection distance decreases, the target resolution and position accuracy deteriorate, and the clutter reception power increases.

The present invention has been made to solve the above-mentioned problems, and sharpens the reception beam width regardless of the transmission beam width and the transmission pulse width (or the transmission frame time) and minimizes the necessary reception. It is an object of the present invention to obtain a bistatic radar device which scans a required space without fail with the number of beams.

[Means for Solving the Problems]

A bistatic radar device according to the present invention includes a transmitter station that transmits a pencil beam or a fan beam from an antenna, and a plurality of sharp receiving pencils that are installed apart from the transmitter station and intersect the transmission beam. The receiving station that simultaneously forms a beam or a bundle of fan beams and the receiving beam at one end of the coverage area that is formed by the bundle of receiving pencil beams or a bundle of fan beams described above ends the predetermined reception time period. And a step scanning means for stepwise moving the individual receiving pencil beam or fan beam so that the coverage area shifts in the propagation direction of the transmission signal by an angle corresponding to one receiving beam It is the one.

[Action]

In the present invention, since the reception beam covers the required angle range with multiple beams, each beam width can be sharpened, and the beam whose reception time period has ended is one beam position ahead in sequence. Since it is sent to, it is possible to minimize the number of received beams.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a bistatic radar apparatus according to an embodiment of the present invention, and this embodiment shows an example in which both a transmitting beam and a receiving beam are pencil beams. In FIG. 1, 1 is a transmitter, 2 is a transmitting antenna, 3 is a transmitting beam controller, 4 is a target, 5 is a receiving antenna, and 6 is a beam scanning signal for sequentially scanning n receiving beams. Receive beam controller, 7 is n digital beam
A former, 8 is a signal processor of n pieces, 9 is a data processor, and 10 is a display.

Next, the operation of this embodiment will be described.

In the transmitting station, the transmission signal generated by the transmitter 1 is radiated into space via the transmitting antenna 2. Here, the beam of the transmission antenna 2 sequentially scans a required search space based on a beam scanning signal generated by the transmission beam controller 3.
The reflected signal from the target 4 is received by the receiving antenna 5 of the receiving station. At this time, the reception beam is composed of a plurality of multi-beams including the required angle range θ _R shown in equation (7),
In the receiving beam at one end of the coverage area formed by a bundle of receiving pencil beams, when the predetermined reception time period ends, the coverage area becomes one reception beam in the propagation direction of the transmission signal. The individual receiving pencil beams are step-moved so as to be displaced by an angle corresponding to. This will be described with reference to FIG.

For simplification, this figure shows a case where three beams with a beam width θ _R / 2 are used and the transmission pulse width τ is long, and it is considered that θ _R = θ _R2 (8).

Now, each point A, B, C, D, E, F in the transmission beam shown in FIG.
It is assumed that the time when the reflected signal from B starts to be received is t = t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , t ₆ as shown in FIG. The beam receives the reflected signal from the area from point A to point B from time t _1.
Received at time t ₄ . Similarly, the beam and the reflected signals from the areas between points B and C and between points C and D are similarly received between times t ₂ and t ₅ , t ₃ and t ₆ . Where time t
_When it reaches ₄ , the beam reception time zone ends, so this beam is moved to the beam position and used for reception of the area from point D to point E. At time t ₅ , the beam is moved to the beam position. Hereinafter, if the beam is sequentially moved every time τ / 2 in this manner, the entire area is searched with three beams.

Further, in the same figure, an example using three simultaneous beams is shown, but in general, when n multi-beams are used, the beam width θ _r per one is approximately 1 / (n
It can be narrowed to -1).

However, α is an angle corresponding to the delay time for beam switching.

Although FIG. 2 illustrates the case where θ _R = θ _R2 , θ _R =
In the case of θ _R1 , there is essentially no change, and the entire area can be searched with a plurality of received beams obtained by dividing θ _R.

The receive beam controller 6 in FIG. 1 schedules the receive beams in the procedure described above,
A beam pointing angle signal is sent to the beam former 7. Based on this signal, the beam former 7
Form a multi-beam of a book. The received signals of the respective beams are integrated by the data processor 9 via the signal processor 8, and after being subjected to processing such as target extraction, position location, and tracking as necessary, they are displayed on the display 10. .

As described above, in this embodiment, the reception beam width can be sharpened without being restricted by the transmission beam width and the transmission pulse width.

In this embodiment, the pencil beam is used for both transmission and reception, but it goes without saying that the fan beam has the same effect. That is, if a fan beam that is wide in the elevation direction is used for both transmission and reception, FIG. 2 can be regarded as a diagram in which these beams are shown in a horizontal plane.

Next, a second embodiment of the present invention will be described with reference to the drawings.

In this embodiment, the transmit beam is an elevation fan beam,
This is an example when the reception beam is a pencil beam.
FIG. 3 is a system diagram showing the configuration of this embodiment. The transmitter 1, transmitter antenna 2 and transmitter beam controller 3 on the transmitter side are the same as the first embodiment except that the transmitter beam is a fan beam. The operation is similar to the example.

Next, the operation will be described. The received signal from the target 4 is received by the receiving antenna 5 of the receiving station. Here, as shown in FIG. 4, the reception beam is M fixed multi-beams that cover the required elevation angle range in the elevation direction, and n beams in the azimuth direction by the same method as in the first embodiment. Are sequentially switched according to the propagation of the transmission signal. Therefore, the beam former is divided into the azimuth direction and the elevation angle direction. The azimuth beam former 11 synthesizes n beams in the azimuth direction based on the azimuth scanning signal from the reception beam controller 6. The elevation beam former 12 further synthesizes M beams in the elevation direction. Therefore, (M × n) multi-beams are instantaneously formed. The operations of the signal processor 8, the data processor 9 and the display 10 after beam combining are the same as those in the first embodiment.

According to this embodiment, a sharp reception beam can be used for the transmission fan beam, and the entire area of the transmission beam can be searched with the minimum required number of reception beams.

In the above-described embodiments, the transmission antenna is an electronic scanning type phased array antenna, but it goes without saying that mechanical beam scanning has the same effect.

In addition, the number of reception beams n need not be fixed,
For example, it is possible to reduce the number of beams as the difference between the target angles of view θ _T and θ _R from the transmitting station and the receiving station becomes smaller, that is, as the target becomes farther.

〔The invention's effect〕

As described above, according to the bistatic radar device of the present invention, a transmitting station that transmits a pencil beam or a fan beam from an antenna, and a plurality of transmitting stations that are installed apart from the transmitting station and intersect the transmitting beam. A receiving station that simultaneously forms a sharp receiving pencil beam or fan beam bundle, and a receiving beam at one end of the coverage area formed by the multiple receiving pencil beam or fan beam bundles. At the end of a predetermined reception time period, each reception pencil beam or fan beam is stepwise moved so that the coverage area shifts in the propagation direction of the transmission signal by an angle corresponding to one reception beam. Since the step scanning means is provided, the detection distance is increased by narrowing the reception beam, the resolution and the position accuracy are improved, and With the effect of reduced Latta received power, because it requires the reception beam number at a minimum, there is an effect that requires only a device size is relatively small.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram showing a configuration of a bistatic radar device according to a first embodiment of the present invention, FIG. 2 is an operation explanatory diagram of the first embodiment, and FIG. FIG. 4 is a system diagram showing a configuration of a second embodiment of the present invention, FIG. 4 is an operation explanatory diagram of the second embodiment, FIG. 5 is a system diagram showing a configuration of a conventional bistatic radar device, and FIG. Is a conventional operation explanation diagram, No. 7
FIG. 8 and FIG. 8 are explanatory diagrams for explaining the required reception beam width. In the figure, 1 is a transmitter, 2 is a transmitting antenna, 3 is a transmitting beam controller, 4 is a target, 5 is a receiving antenna, 6 is a receiving beam controller, 7 is a digital beam former,
Reference numeral 8 is a signal processor, 9 is a data processor, 10 is a display, 11 is an azimuth beam former, and 12 is an elevation beam former. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A transmitting station for transmitting a pencil beam or a fan beam from an antenna, and a bundle of a plurality of receiving pencil beams or fan beams installed apart from the transmitting station and intersecting the transmitting beam. The receiving station formed at the same time and the receiving beam at one end of the coverage area formed by the bundle of the above-mentioned multiple receiving pencil beams or fan beams transmit the coverage area when a predetermined reception time period ends. And a step scanning means for stepwise moving individual receiving pencil beams or fan beams so as to deviate in the direction of signal propagation by an angle corresponding to one receiving beam. Radar equipment.