JP2646880B2 - Airborne radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device mounted on an aircraft for shortening the time required for detecting altitude differences and cross-sectional information of obstacles when the aircraft flies at a low altitude.

[0002]

2. Description of the Related Art FIG. 5 is a view showing the configuration of a conventional radar device for on-board an aircraft. In the drawing, 1 is a transmitter, 2 is a transmission / reception switch, 3 monopulse antenna, 4 is a monopulse antenna 3
Sum signal output from the sigma ₀ and each of the difference signal delta ₀ connected receiver, 5 signal processor, 6 indicator, 7 is an antenna driving device for driving a monopulse antenna 3.
FIG. 6 is a diagram showing a configuration of a signal processor 5 which is a component of a conventional airborne radar device. In the figure, 8 is a buffer circuit, 9 is a signal detector, 10 is a divider, and 11 is altitude. A difference detector, 12 is a distance calculator, and 13 is a terrain section detector.

Next, the operation will be described. The transmitter 1 generates a transmission pulse signal having a constant pulse repetition period, and outputs the monopulse antenna 3 via the transmission / reception switch 2.
Radiated from the outside space. Then, the reflected signal from the obstacle is received by the monopulse antenna 3 and converted into a sum signal Σ ₀ and a difference signal Δ ₀ . Further, the receiver 4 converts the sum signal Σ ₀ and the difference signal Δ ₀ converted by the monopulse antenna 3 into video signals, respectively.

The signal processor 5 has a function of detecting an altitude difference of an obstacle and a function of detecting cross-sectional information of an obstacle. The altitude difference detector 11 corresponding to each function is provided.
And the terrain section detector 13 will be described separately. First, in the altitude difference detector 11, the buffer circuit 8 in the signal processor 5 stores the sum signal Σ and difference signal Δ converted into video signals for each range bin, and outputs the sum signal Σ to the signal detector 9. Then, the sum signal Σ and the difference signal Δ are output to the divider 10. The signal detector 9 calculates CFAR from the input sum signal Σ.
(Constant False Alarm Rat
e) The signal is detected by a circuit or the like, and the subsequent altitude difference detector 1
In step 1, the range bin range to be processed is determined, and the range bin number is output to the altitude difference detector 11. Meanwhile, divider 1
0 converts the input sum signal Σ and difference signal Δ into the ratio Δ / Σ of the difference signal Δ to the sum parent signal Σ, and outputs the ratio to the altitude difference detector 11.

Next, the operation of the altitude difference detector 11 will be described with reference to FIG. FIG. 7 is a processing conceptual diagram of the altitude difference detector 11, in which 14 is an aircraft and 15 is an obstacle. This figure shows the detection of the altitude difference of the obstacle 15 ahead from the on-board radar device mounted on the aircraft 14 at the altitude H ₀ . Here, of the range bins output from the signal detector 9, the processing content of the point A that exists at the i-th range bin number will be described. The angle Δθ _i of the point A from the antenna center axis can be calculated by Expression (1) using the ratio Δ _i / Σ _i of the difference signal Δ _i to the sum signal Σ _i output from the divider 10. . Δθ _i = Km · Δ _i / Σ _i (1) where K
m = error sensitivity

[0006] The distance R _i of the i-th point of the range bin number can be calculated by equation (2). R _i = i · ΔR (2) where ΔR = range bin width The altitude difference ΔH _i of the point A from the antenna center axis is calculated by the equation (3) from the equations (1) and (2). ΔH _i = R _i · tan Δθ _i = i · ΔR · tan (Km · Δ _i / Σ _i ) (3) Then, the range of the range bin output from the signal detector 9 is expressed by the formulas (1) and (2) for each range bin. ) And equation (3)
The altitude difference of the obstacle is detected by repeating the processing represented by. Further, the above processing is processing in a certain azimuth direction. The antenna driver 7 for mechanically driving the monopulse antenna 3 scans the desired coverage area in the azimuth direction, and performs the same processing in each azimuth direction. , It is possible to detect a height difference between obstacles in a desired covered area. This altitude difference is converted into luminance information and output to the display 6 to display the altitude difference corresponding to the azimuth direction and the range on the screen.

Next, the terrain section detector 13 will be described. The buffer circuit 8 in the signal processor 5 stores the sum signal Σ and difference signal Δ converted into video signals for each range bin, and detects the sum signal Δ. The sum signal Σ and the difference signal Δ are output to the divider 10. The signal detector 9 outputs a CFAR (Constant Fa) from the input sum signal Σ.
A signal is detected by a circuit such as an alarm rate (Lse Alarm Rate) circuit, the range of the range bin to be processed is determined by the distance calculator 12 at the subsequent stage, and the range bin number is output to the distance calculator 12. On the other hand, the divider 10 receives the ratio of the difference signal Δ to the sum signal か ら (hereinafter “Δ / Σ”) from the input sum signal Σ and difference signal Δ.
The signal is referred to as “signal”) and output to the distance calculator 12.
The distance calculator 12 detects a range bin in which the polarity of the Δ / Σ signal output from the divider 10 is inverted, within the range of the range bin output from the signal detector 9. When the range bin number at which the polarity of Δ / Σ is inverted is the i-th, the slant range R _S can be calculated by the equation (4), and is output to the terrain section detector 13. R _S = i · ΔR (4) where ΔR = range bin width

Next, the terrain section detector 13 will be described with reference to FIG. FIG. 8 is a processing conceptual diagram of the terrain cross-section detector 13, in which 14 is an aircraft, and 15 is an obstacle.
This figure shows the detection of cross-sectional information of the obstacle 15 ahead in the own flight direction from the on-board radar device mounted on the aircraft 14 at the altitude H ₀ . Also, Σ in the figure indicates the sum pattern of the monopulse antenna 3, and Δ
(+) And Δ (−) are difference patterns. In (), + indicates the same phase as the sum pattern, and − indicates that the phase is opposite to the sum pattern. Assuming that the intersection point between the center axis of the antenna beam in the directivity direction θ _j and the obstacle is a point P _j , a range bin in which the polarity of the Δ / Σ signal is inverted from negative to positive is detected by the processing of the distance calculator 11, and the slant is detected. The range R _sj is determined using equation (4). The altitude H _j and the horizontal distance R _j of the point P _j Equation (5), is calculated by equation (6). R _j = R _sj · cos θ _j (5) H _j = H ₀ -ΔH _J = H ₀ -R _sj · sin θ _j (6)

[0009] The slope T _j between the intersection between the center axis and the obstacle and the point P _{j + 1} and point P _j and the point P _{j + 1} in the directivity direction theta _{j + 1} of the antenna beam (5 ) And Expression (6) are calculated by Expression (7).

[0010]

(Equation 1)

Next, the antenna driver 7 scans the antenna beam along a vertical plane in the flight direction of the own aircraft, and performs the same processing in each elevation angle direction, thereby obtaining the inclination T of the obstacle with respect to the horizontal distance R. Is calculated. By converting the inclination T of the obstacle into luminance information and outputting the luminance information to the display 6 to display the inclination T of the obstacle with respect to the horizontal distance R, it is possible to recognize cross-sectional information of the obstacle such as terrain. .

By performing the above processing, the beam is scanned in the azimuth direction, the height difference of the terrain is detected, and the beam is scanned in the elevation angle direction, whereby the cross-sectional information of the terrain can be recognized.

[0013]

Since the conventional aircraft-mounted radar apparatus is configured as described above, when detecting the altitude difference and the cross-sectional information of the obstacle ahead, a single area within a desired area is detected. Since the scanning is performed with the antenna beam and the reflected signal from the obstacle is obtained, there is a problem that the time for detecting the cross-sectional information of the obstacle becomes long.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. A digital signal received by a plurality of element antennas is temporarily stored in a buffer memory, and the received digital signal is subjected to a time-division Fourier transform. In this way, a plurality of reception beams are formed during a pulse repetition period (hereinafter, referred to as “PRI”), and the height difference of the obstacle and the cross section information are detected for each reception beam, thereby obtaining the height difference of the obstacle. It is another object of the present invention to obtain an on-board radar apparatus capable of shortening the detection time of cross-sectional information.

According to another aspect of the present invention, in addition to the above object, a transmission pulse signal is divided into a plurality of sub-pulses,
An object of the present invention is to provide an aircraft-mounted radar device capable of improving the signal-to-noise power ratio by performing beam scanning with a narrow beam in such a manner that the sub-pulses correspond to the transmission beam directing direction.

[0016]

According to the present invention, there is provided an aircraft-mounted radar device including a transmission device capable of transmitting a transmission pulse signal with a fan beam in a desired coverage area,
A beam forming circuit for forming a pair of reception beams having the same azimuth angle but different elevation angles, and a plurality of reception beams having the same azimuth angle but continuously different elevation angles is provided in a time-division manner. In the plurality of reception beams, the sum and difference of reception signals received by a pair of reception beams having different elevation angles in the azimuth direction are calculated, and the reception signals are received by two reception beams adjacent to each other in the elevation angle direction. A monopulse arithmetic circuit for calculating the sum and difference of the received signals is provided.

According to another aspect of the present invention, there is provided an airborne radar apparatus for controlling the phase of a transmission pulse signal in order to form a transmission beam directed in an arbitrary direction, instead of the transmission apparatus. , An amplifier that amplifies the output signal of the phase shifter, a transmission pulse modulation circuit that divides a transmission pulse signal into a plurality of sub-pulses, and supplies the sub-pulses to each phase shifter, and controls an azimuthal direction in which each of the sub-pulses is radiated. And a phase shift amount calculation circuit for calculating a phase shift amount necessary for forming a transmission beam in the radiation direction of each of these sub-pulses.

[0018]

According to the present invention, a received digital signal obtained by digitizing a reflected signal from an obstacle received via a plurality of element antennas is temporarily stored in a buffer memory, and the received digital signal is time-divided by a beam forming circuit. By performing the Fourier transform, a plurality of reception beams pointing in different azimuth directions are formed during one PRI, and a plurality of reception beams having the same azimuth angle and continuously different elevation angles are formed, and reception is performed for each reception beam. By processing the signal, the time required to detect the height difference and the cross-sectional information of the obstacle can be reduced.

Further, in another aspect of the present invention, in addition to the above-described operation, a transmission pulse signal generated by a transmitter is divided into a plurality of sub-pulses, and an amplifier and a transfer circuit provided corresponding to a plurality of element antennas are provided. The effective radiation power is increased by sequentially radiating the sub-pulses in different directions within the pulse width of the transmission pulse signal while scanning the narrow beam spatially synthesized using the phaser in the azimuth direction and the elevation angle direction. As a result, the signal-to-noise power ratio can be improved.

[0020]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. Note that the same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 16 denotes a transmitting antenna, and 17 denotes a transmitting antenna.
6, a transmitting device including the transmitter 1; 18, an element antenna; 19, an array antenna including a plurality of element antennas 18; 20, a buffer memory; 21, a beam forming circuit; .

Next, the operation will be described with reference to FIGS. FIG. 2 is a diagram showing a receiving beam forming method of the aircraft-mounted radar device of the present invention, in which 23 is the aircraft-mounted radar device of the present invention, 24 is a desired coverage area, and B _j1 or B _j2 is the bearing. Directional receive beams, where B ′ _j is each receive beam (where j is a natural number). The transmission pulse signal generated by the transmitter 1 is transmitted via the transmission antenna 16 by a fan beam that covers a desired coverage area 24 as shown in FIG.

Next, an array antenna tenor 19 composed of a plurality of element antennas 18 receives a reflected signal from an obstacle and outputs the signal to the receiver 4 connected to each element antenna 18. Each receiver 4 amplifies and detects the input received signal, digitizes the signal, and outputs the received digital signal to the buffer memory 20. Then, the buffer memory 20 outputs the input received digital signal to the beam forming circuit 21, and the beam forming circuit 21 Fourier-transforms the input received digital signal to form a pair of received beams B _j1 and B _j2. By repeating the division, a pair of reception beams having different azimuth angles is formed. Further, the input received digital signal is Fourier-transformed to form a plurality of received beams _B′j in a time-division manner in the elevation angle direction. By performing the above processing, the beam forming circuit 21 can form the cross-shaped reception beams B _j1 , B _j2 and B ′ _j as shown in FIG. Note that a pair of reception beams B _j1 and B _j2 and reception beams B ′ _j and B ′ adjacent in the elevation angle direction are used.
_{Since the} monopulse computation is performed by the monopulse computation circuit 22 at the subsequent stage, the interval between the beam centers of _{j + 1} is about 0.3 · θb, where the beam width is θb, as is well known to those skilled in the art.

The monopulse operation circuit 22 receives the received symbols obtained by the pair of received beams B _j1 and B _j2 and the received beams B ′ _j and B ′ _{j + 1} adjacent in the elevation direction, and receives these received signals. Are added to calculate a sum signal Σ _j . Further subtracts those received signals, calculates a difference signal delta _j. Thus, to calculate the monopulse arithmetic circuitry 21 is the sum signal sigma _j and the difference signal delta _j of each elevation angle direction,
Output to the signal processor 5.

[0025] Then the signal processor 5 is input sum signal sigma _j and the difference signal delta _j of elevation angle for each direction stored in the buffer memory circuit 8, a conventional airborne radar system in azimuth direction and elevation angle for each direction By performing the same processing as described above, altitude differences and cross-sectional information of obstacles such as terrain can be obtained.

Embodiment 2 FIG. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a configuration of an aircraft-mounted radar device according to another embodiment of the present invention. In the figure, 2, 4, 18 to 22, and 5 to 6 have exactly the same configuration as the above-mentioned aircraft-mounted radar apparatus of the present invention, 25 is a transmitting / receiving module, 26 is an amplifier, and 27 is a phase shifter. Module 26 comprises receiver 4, duplexer 2,
It comprises an amplifier 26 and a phase shifter 27. 1 is a transmitter, 28 is a transmission pulse modulation circuit connected to all phase shifters 27, 29 is a beam control circuit, and 30 is a phase amount calculation circuit connected to all phase shifters 27.

Next, the operation will be described with reference to FIGS. FIG. 4A is a diagram showing a transmission beam scanning method and a reception beam forming method of an aircraft-mounted radar apparatus according to another embodiment of the present invention, and FIG. 4B is an aircraft according to another embodiment of the present invention. FIG. 3 is a diagram illustrating transmission timing of the on-board radar device. In the figure, 31 is a airborne radar device of another aspect of the invention, since the transmission beam is in a cross shape as shown in figure, first, to describe the azimuth, B _j1 or B _j2 (here And j is a natural number.)
Each of the receive beams, B _j is the transmit beam, theta _j is the azimuthal angle of orientation of the transmitted beam B _j, the shape of the transmit beam B _j is the same as a composite of received beam B _j1 and B _j2 is there. When the elevation angle direction is described,
_j (where j is a natural number) is each received beam,
B ′ _{j, j + 1} is the transmission beam, θ ′ _j is the transmission beam B _{j, j + 1}
And the shape of the transmission beam B ′ _{j, j + 1} is the same as the combination of the reception beams B ′ _j and B ′ _{j + 1} .

Next, a method of forming a transmission beam will be described. The transmission beam is scanned in the azimuth direction, and then scanned in the elevation direction, so that the transmission beam is also formed in a cross shape as shown in FIG. You. First, the transmission method in the azimuth direction will be described. The transmission pulse signal generated by the transmitter 1 is input to the transmission pulse modulation circuit 28. The transmission pulse modulation circuit 28 divides the transmission pulse signal into a plurality of sub-pulses at the transmission timing as shown in FIG. Further, the beam control circuit 21 instructs the azimuth direction θ _{j at} which each sub-pulse is radiated, and the phase shift amount calculation circuit 30 outputs each phase shifter 27 necessary to form a transmission beam in the radiation direction θ _j of each of these sub-pulses. calculating a phase shift amount phi ₁ to [phi] _m, and outputs to the phase shifter 27. In this manner, each sub-pulse input to the phase shifter 27 is radiated from the array antenna 19 via the amplifier 26 and the transmission / reception switch 2 in the beam direction controlled by the beam control circuit 29.

Next, the method of scanning the transmission beam in the elevation angle direction will be described.
A transmission pulse is generated, divided into a plurality of sub-pulses at a transmission timing as shown in FIG. 4B, further distributed and input to a plurality of phase shifters 27. Further, the beam control circuit 29 instructs the elevation direction θ ′ _j for emitting each sub-pulse, and the phase shift amount calculation circuit 30 performs each phase shift necessary for forming a transmission beam in the emission direction θ ′ _j of each of these sub-pulses. The phase shifters φ ′ _{1 to} φ ′ _m of the phase shifter 27 are calculated and output to the phase shifter 27. In this manner, each sub-pulse input to the phase shifter 27 is radiated from the array antenna 19 via the amplifier 26 and the transmission / reception switch 2 in the beam direction controlled by the beam control circuit 29.

As described above, the transmission beams B _j and B ′ _{j
, j + 1} are B ₁ , B ₂ ... within the pulse width of the transmission pulse signal.
・ The beam is scanned sequentially in the azimuth direction, and B _1,2 ,
Each of the sub-pulses is radiated into the desired coverage area 24 while sequentially performing beam scanning in the direction of B _2,3 .

Next, the array antenna 19 receives the reflected signal from the obstacle and outputs it to the receiver 4 via the transmission / reception switch 2. Each of the receivers 4 amplifies an input received signal.
After detection, the digital signal is digitized, and the received digital signal is output to the buffer memory 20. The received digital signal is output to the beam forming circuit 20, and the beam forming circuit 21 performs a Fourier transform on the input received digital signal,
A pair of reception beams B _j1 and B _{j2 having} different elevation angles in each azimuth direction θ _j that radiates each sub-pulse, and reception beams B ′ _j and B ′ _{j + 1} adjacent in each elevation angle θ ′ _j are interposed between _one PRI. A plurality is formed by time division. Then, the monopulse operation circuit 22 and the signal processor 5 perform the same processing as that of the above-described radar device for airborne vehicle of the present invention to detect cross-sectional information of obstacles such as terrain.

[0032]

As described above, according to the present invention, a receiver is connected to each element and a buffer memory and a beam forming circuit are provided so that a large number of reception beams can be obtained in a time division manner during one PRI. Therefore, a received signal from an obstacle can be obtained during one PRI, and the processing time for detecting cross-sectional information of the obstacle can be reduced.

According to another aspect of the present invention, in addition to the above effects, the transmission pulse signal is divided into a plurality of sub-pulses, and each sub-pulse is sequentially narrowed and narrowed within a pulse width of the transmission pulse signal by a narrow beam. By radiating in the following direction, the effective radiation power can be increased, and the signal-to-noise power ratio can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an aircraft-mounted radar device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of forming a reception beam of the radar device mounted on an aircraft according to the present invention.

FIG. 3 is a configuration diagram of an aircraft-mounted radar device according to another embodiment of the present invention;

FIG. 4A is a diagram showing a transmission beam scanning method and a reception beam forming method of an aircraft-mounted radar apparatus according to another embodiment of the present invention, and FIG. 4B is an aircraft according to another embodiment of the present invention; FIG. 3 is a diagram illustrating transmission timing of the on-board radar device.

FIG. 5 is a configuration diagram of a conventional airborne radar device.

FIG. 6 is a configuration diagram of a signal processor which is a component of a conventional aircraft-mounted radar device.

FIG. 7 is a conceptual diagram of processing for detecting a height difference between obstacles.

FIG. 8 is a conceptual diagram of processing for detecting section information of an obstacle.

[Explanation of symbols]

 Reference Signs List 16 transmission antenna 17 transmission device 18 element antenna 19 array antenna 20 buffer memory 21 beam forming circuit 22 monopulse operation circuit 25 transmission / reception module 26 amplifier 27 phase shifter 28 transmission pulse modulation circuit 29 beam control circuit 30 phase shift amount calculation circuit

Claims (2)

(57) [Claims] 1. An airborne radar apparatus for detecting an obstacle ahead by forming a plurality of reception beams from reception signals received by each element antenna of an array antenna, and radiating a transmission pulse signal within a desired coverage area. A transmitter, a plurality of receivers provided corresponding to the respective element antennas, amplifying and detecting the received signal, and digitizing the received signal; a buffer memory for storing output signals of the plurality of receivers; and a buffer memory. A pair of reception beams having the same azimuth angle but different elevation angles are formed in any azimuth direction from the output signal of, and a plurality of reception beams having the same azimuth angle and continuously different elevation angles are formed in a time-division manner. A beam forming circuit that calculates the sum and difference of signals received by a pair of reception beams having different elevation angles in the azimuth direction among the plurality of reception beams, Is a monopulse arithmetic circuit for calculating the sum and difference of signals received by two adjacent receive beams, and a signal processing for detecting an altitude difference of the obstacle from an output signal of the monopulse arithmetic circuit and extracting cross-sectional information. Airborne radar device equipped with an instrument. 2. An aircraft-mounted radar device for forming a plurality of reception beams from a reception signal received by each element antenna of an array antenna to detect an obstacle ahead of the array antenna. A phase shifter that controls the phase of the transmission pulse signal to form a transmission beam directed in the direction of the amplifier, an amplifier that amplifies the output signal of the phase shifter, and divides the transmission pulse signal into a plurality of sub-pulses. A transmission pulse modulation circuit that supplies each of the phase shifters, a beam control circuit that controls each of the sub-pulses in the radiation direction, and a beam control circuit that controls each of the phase shifters necessary to form a transmission beam in the radiation direction of each of the sub-pulses. A phase shift amount calculating circuit for calculating a phase shift amount, a plurality of receivers provided corresponding to each of the element antennas for amplifying and detecting the received signal and digitizing the received signal; A buffer memory for storing an output signal of the transceiver, and a pair of reception beams having different elevation angles are formed in the azimuth direction from the output signal of the buffer memory for each azimuth direction in which each of the sub-pulses is emitted. Is a beam forming circuit that forms a plurality of reception beams in each direction that emitted the angular sub-pulse in a time-division manner, and a signal received by a pair of reception beams having different low angles in the azimuth direction among the plurality of reception beams. Calculating a sum and a difference, and calculating a sum and a difference of signals received by two reception beams adjacent to each other in the elevation angle direction; and calculating an altitude of the obstacle from an output signal of the monopulse calculation circuit. An aircraft-mounted radar device including a signal processor that detects a difference and extracts cross-sectional information.