JP2605957B2 - Airborne radar equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device mounted on an aircraft, which shortens the time required to detect a height difference between obstacles when the aircraft flies at a low altitude.

[Conventional technology]

FIG. 5 is a diagram showing a configuration of a conventional radar device mounted on an aircraft, wherein (1) is a transmitter, (2) is a transmission / reception switch, (3) is a monopulse antenna, and (4) is a monopulse antenna. Sum signal _{０ 0} and difference signal Δ output from (3)
₀ , a receiver connected to each of the signals ₀ , (5) is a signal processor,
(6) is a display, and (7) is an antenna driver for driving the 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.
(8) is a buffer circuit, (9) is a signal detector, (10) is a divider, and (11) is an altitude difference detector.

 Next, the operation will be described.

In the transmitter (1), a transmission pulse signal having a constant pulse repetition period is generated and radiated from the monopulse antenna (3) to the external space via the transmission / reception switch (2). The signal reflected from the obstacle is received by the monopulse antenna (3) and converted into a sum signal _{０ 0} and a difference signal Δ ₀ . The receiver (4) is a monopulse antenna (3)
The converted sum signal _{０ 0} and difference signal Δ ₀ are each converted into a video signal.

Next, a buffer circuit (8) in the signal processor (5) stores the sum signal Σ and the difference signal Δ converted into the video signal for each range bin, and outputs the sum signal Σ to the signal detector (9). The sum signal Σ and the difference signal Δ are output to the divider (10).
The signal detector (9) converts the sum signal Σ into a CFAR (Cons
tant False Alarm Rate)
The range bin to be processed is determined by the altitude difference detector (11) at the subsequent stage, and the range bin number is determined by the altitude difference detector (11).
Output to On the other hand, the divider (10) converts the input sum signal Σ and difference signal Δ into a ratio Δ / Σ of the difference signal Δ to the sum 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 conceptual diagram of the processing performed by the altitude difference detector (11), in which (12) is an aircraft and (13) is an obstacle. This figure shows the place where detecting the altitude difference of the front obstacle (13) from the airborne radar device on board the aircraft (12) of altitude H _0. Here, of the range bin range output from the signal detector (9), a certain range bin number i
The processing content of the second point A will be described. Point A
Angle [Delta] [theta] _i ratio of the difference signal delta _i is for the sum signal sigma _i output from the divider (10) Δ _i / _{Σ i} from the antenna center axis
Can be calculated using the following equation.

Δθ _i = Km ・ Δ _i / Σ _i (1) where Km = error sensitivity The distance R _i of the i-th point in the range bin number can be calculated by the following equation.

R _i = i · ΔR (2) Here, ΔR = range bin width From formulas (1) and (2), the altitude difference ΔH _i of the point A from the antenna center axis is calculated by the following formula.

ΔH _i = R _i · tan Δθ _i = i · ΔR · tan (Km · Δ _i / Σ _i ) (3) And the range bin range output from the signal detector (9) is expressed by the following formula (1) for each range bin. , (2) and (3) are repeated to detect an altitude difference between obstacles. Further, the above processing is processing in a certain azimuth direction. The antenna driver (7) for mechanically driving the monopulse antenna (3) scans the beam in the desired coverage in the azimuth direction. By performing the same processing in the above, it is possible to detect a difference in altitude of an obstacle 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.

[Problems to be solved by the invention]

Since the conventional aircraft radar system is configured as described above, when detecting the altitude difference of the obstacle ahead, it mechanically scans the desired area with a single beam and scans from the obstacle. Since the reflected signal is acquired with one receiving beam,
There is a problem that the time required to detect the height difference between obstacles becomes longer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and temporarily stores received digital signals received by a plurality of element antennas in a buffer memory, and further Fourier-transforms the received digital signals to obtain a pulse repetition period ( (Hereinafter referred to as "PRI"). For aircraft-mounted systems that can reduce the time required to detect obstacle height differences by forming multiple reception beams during each direction and detecting the height difference between obstacles in each azimuth direction. An object is to obtain a radar device.

According to another aspect of the present invention, in addition to the above objects, a transmission pulse signal is divided into a plurality of sub-pulses, and the sub-pulses are respectively scanned in a transmission beam directing direction by a narrow beam. It is an object of the present invention to provide an airborne radar device capable of improving a signal-to-noise ratio.

[Means for solving the problem]

The airborne radar device according to the present invention is provided with a transmission device capable of transmitting a fan beam within a desired coverage area, and a pair of reception beams having the same azimuth and different elevation angles are time-divided between 1PRI. A beam forming circuit capable of forming a plurality of beams in different azimuth directions is provided, and a monopulse arithmetic circuit for calculating a sum and a difference of signals received by a pair of receiving beams is provided at a subsequent stage.

An aircraft-mounted radar device according to another aspect of the present invention includes a phase shifter that controls a phase of a transmission pulse signal in order to form a transmission beam directed in an arbitrary direction, instead of the transmission device. An amplifier for amplifying the output signal of the phase shifter, a transmission pulse modulation circuit for dividing the transmission pulse signal into a plurality of sub-pulses and supplying the sub-pulses to each phase shifter, and a beam control for controlling the azimuthal direction in which the sub-pulses are radiated And a phase shift amount calculating circuit for calculating a phase shift amount necessary for forming a transmission beam in the radiation direction of each of these sub-pulses.

[Action]

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-divisionally Fourier transformed by a beam forming circuit. Accordingly, a plurality of reception beams pointing in different azimuth directions are formed during one PRI, and the reception signal is processed for each reception beam, thereby shortening the time required to detect a height difference between obstacles.

In another embodiment 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 phase shifter provided corresponding to a plurality of element antennas are provided. The effective radiation power is increased by sequentially radiating the plurality of sub-pulses within the pulse width of the transmission pulse signal in the directions having different azimuth angles while scanning the narrow beam spatially synthesized using the azimuth direction, The signal to noise power ratio can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Note that the same components as those in the prior 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 which (14) is a transmitting antenna, and (15) is a transmitting antenna (1).
4) and a transmitter (1).
6) is an element antenna, (17) is a multiple element antenna (1
An array antenna composed of 6), (18) a buffer memory, (19) a beam forming circuit, and (20) a monopulse operation circuit.

 Next, the operation will be described with reference to FIG. 1 and FIG.

FIG. 2 is a diagram showing a method of forming a reception beam of the aircraft-mounted radar device of the present invention, wherein (21) is an aircraft-mounted radar device of the present invention, (22) is a desired coverage area, B _j1
Alternatively, B _j2 (where j is a natural number) is each received beam. The transmission pulse signal generated by the transmitter (1) is transmitted via a transmission antenna (14) by a fan beam that covers a desired coverage area (22) as shown in FIG.

Next, an array antenna (17) composed of a plurality of element antennas (16) receives a reflected signal from an obstacle,
Output to the receiver (4) connected to each element antenna (16). Each of the receivers (4) amplifies and detects the input received signal, digitizes the signal, and outputs the received digital signal to a buffer memory. And buffer memory (1
8) converts the input received digital signal into a beam forming circuit (1
9) and is calculated as follows: For example, the direction in which the N element antennas (17) are arranged is the X axis, the angle between the arrival direction of the radio wave and the X axis is the arrival angle θ of the radio wave, the interval between the element antennas (17) is d, and the wavelength is λ. Then, the phase difference between the received signals received by the adjacent element antennas (17) is 2π (dsinθ) / λ (4), so that the j-th beam Bj is expressed by the following equation. Is calculated, N beams having the maximum gain at θj = sin ⁻¹ (jλ / Nd) can be formed. However, in equation (5), Wk is a weighting factor for side-rope suppression. Although the above calculation was considered only for the X axis,
The same calculation is performed for the two axes XY. In this way,
As shown in FIG. 2, a pair of reception beams having different azimuth angles are formed. The interval between the beam centers of the pair of reception beams B _j1 and B _j2 is determined by a mono-pulse calculation circuit (20) at the subsequent stage, and the beam width is assumed to be θb, as is well known to those skilled in the art. It is about 0.3 · θb.

And the monopulse operation circuit (20) is a pair of reception beams
The received signals obtained at B _j1 and B _j2 are input, and the received signals are added to calculate a sum signal Σ _j . Further subtracts those received signals, calculates a difference signal delta _j. In this manner, a plurality of monopulse arithmetic circuit (20) calculates a sum signal sigma _j and the difference signal delta _j of the respective azimuth directions, and outputs the signal processor (5).

Next, the signal processor (5) stores the input sum signal _{ｊ j} and difference signal Δ _j for each azimuth direction in a buffer circuit (8), and performs the same processing as the conventional aircraft-mounted radar device for each azimuth direction. By doing so, an altitude difference between obstacles can be obtained.

Next, another 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 invention of the present invention. In the figure, (2),
(4), (16) to (20) and (5) to (6) are completely the same as the above-described aircraft mounted radar apparatus of the present invention.
(23) is a transmission / reception module, (24) is an amplifier, (25) is a phase shifter, and the transmission / reception module (23) is a receiver (4), a transmission / reception switch (2), an amplifier (24) and a phase shifter ( 25). (1) is a transmitter, (26) is a transmission pulse modulation circuit connected to all phase shifters (25), (17) is a beam control circuit, and (28) is all phase shifters (25). It is a connected phase shift amount calculation circuit.

Next, the operation will be described with reference to FIG. 3 and FIG.

FIG. 4 (a) is a diagram showing a scanning direction of a transmitting beam and a method of forming a receiving beam of an airborne radar apparatus according to another embodiment of the present invention, and FIG. 4 (b) is another embodiment of the present invention. FIG. 3 is a diagram showing transmission timings of the aircraft-mounted radar device. In the figure, (29) is an aircraft-mounted radar device according to another embodiment of the present invention, and B _j1 or B _j2 (where j is a natural number) are the respective receiving beams. It is the same as each reception beam formed by the radar device. B _j is the transmission beam, θ _j is the transmission beam B _j
A azimuth angle of orientation of the shape of the transmitted beam B _j are the same as those obtained by combining the received beam B _j1 and B _j2. First,
The transmission pulse signal generated by the transmitter (1) is input to the transmission pulse modulation circuit (26). Transmit pulse modulation circuit (26)
In FIG. 4, the transmission pulse signal is divided into a plurality of sub-pulses at the transmission timing as shown in FIG. The beam control circuit (27) instructs the azimuth direction theta _j which emits the sub-pulses, the phase shift amount calculating circuit (28) each required to form a transmission beam in the radial direction theta _j of each sub-pulse calculating a phase shift amount phi ₁ to [phi] _m of the phase shifter (25), and outputs to the phase shifter (25). In this way, each sub-pulse input to the phase shifter (25) passes through the amplifier (24) and the transmission / reception switch (2) in the beam direction controlled by the beam control circuit (27). Radiated from 17).

As described above, transmit beam B _j is while B _1, B ₂ ...... sequentially beam scanned within a pulse width of the pulse signal of a transmission pulse signal, to emit respective sub-pulses to a desired covering region (22) .

Next, the array antenna (17) receives the reflected signal from the obstacle and outputs it to the receiver (4) via the transmission / reception switch (2). Each receiver (4) amplifies and detects the input received signal, digitizes the signal, and outputs the received digital signal to a buffer memory (18). The received digital signal is output to a beam forming circuit (19), and the beam forming circuit (19) performs a Fourier transform on the input received digital signal to emit a pair of signals having different elevation angles for each azimuth direction θ _j in which each sub-pulse is emitted. A plurality of reception beams B _j1 and B _j2 are formed in a time division manner between 1PRI. Then, the monopulse arithmetic circuit (20) and the signal processor (5) perform the same processing as that of the above-mentioned aircraft-mounted radar apparatus of the present invention to detect a height difference of an obstacle.

〔The invention's effect〕

As described above, according to the present invention, a receiver is connected to each element antenna, 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. Thus, a signal received from an obstacle can be obtained, and the processing time for detecting a height difference between obstacles can be reduced. Further, by providing the buffer memory, a pair of reception beams having the same azimuth angle but different elevation angles are formed in a time division manner, so that it is not necessary to provide a plurality of monopulse arithmetic circuits and signal processors for each of the pair of reception beams. In addition, the volume and mass of the device 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 radiated in a narrow beam within the pulse width of the transmission pulse signal in the direction having a different azimuth sequentially. By doing so, 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 block diagram of an airborne radar apparatus according to an embodiment of the present invention, FIG. 2 is a view showing a method of forming a reception beam of the airborne radar apparatus of the present invention, and FIG. FIG. 4 (a) is a diagram showing a scanning direction of a transmitting beam and a method of forming a receiving beam of an aircraft-mounted radar device according to another embodiment of the present invention. FIG. 4 (b) is a diagram showing the transmission timing of an airborne radar device according to another invention of the present invention, 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, and FIG. 7 is a conceptual diagram of processing for detecting altitude. In the figure, (1) is a transmitter, (2) is a transmission / reception switch, (3) is a monopulse antenna, (4) is a receiver, (5) is a signal processor, (6) is a display, (7) Is the antenna driver,
(8) is a buffer circuit, (9) is a signal detector, (10) is a divider, (11) is an altitude difference detector, (12) is an aircraft, (1)
3) is an obstacle, (14) is a transmitting antenna, (15) is a transmitting device, (16) is an element antenna, (17) is an array antenna,
(18) is a buffer memory, (19) is a beam forming circuit,
(20) is a monopulse arithmetic circuit, (21) and (29) are the radar devices mounted on an aircraft of the present invention, (22) is a desired coverage area, (2)
3) is a transmission / reception module, (24) is an amplifier, (25) is a phase shifter, (26) is a transmission pulse modulation circuit, (27) is a beam control circuit, and (28) is a phase shift amount calculation circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

(57) [Claims] 1. An aircraft mounted for detecting a difference in altitude of an obstacle ahead by forming a plurality of pairs of reception beams having the same azimuth angle and different elevation angles from reception signals received by each element antenna of an array antenna. In a radar device for use, a transmitting device that emits a transmission pulse signal using a fan beam in a desired coverage area, a plurality of element antennas that receive a reflected signal from a target in the coverage area, and each of these element antennas A plurality of receivers that are connected and amplify and detect and digitize the received signal, a buffer memory that stores output signals of the plurality of receivers, and an output signal of the buffer memory that is input and subjected to Fourier transform. A beam forming circuit for forming a plurality of the pair of reception beams in each azimuth direction for each range bin, and a sum signal from signals received by the pair of reception beams; A monopulse calculation circuit for calculating a difference signal for each pair of reception beams, and a signal processor for calculating an altitude difference of the obstacle by calculating an angle and a distance of the obstacle for each range bin from an output signal of the monopulse calculation circuit An aircraft-mounted radar device comprising: 2. A plurality of pairs of reception beams having the same azimuth angle but different elevation angles are formed in a plurality of azimuth directions from reception signals received by each element antenna of the array antenna, and an altitude difference of an obstacle in front is detected. In an airborne radar device, a transmitter that generates a transmission pulse signal at a certain pulse repetition period, and a transmission pulse signal that is connected to the transmitter and output is divided into a plurality of sub-pulses and a plurality of sub-pulses described below. A transmission pulse modulation circuit to be supplied to each phaser, and a beam control for controlling the transmission beams such that each of the sub-pulses is radiated in an azimuth direction covering a pair of reception beams arranged in the azimuth direction. And a phase shifter connected to the beam control circuit for calculating a phase shift amount of each of the phase shifters required to form a transmission beam in a radiation direction of each of the sub-pulses. A phase calculation circuit, provided corresponding to each of the element antennas, receives the transmission pulse signal from the transmission pulse modulation circuit and the phase shift amount from the phase shift amount calculation circuit, and changes the phase of the transmission pulse signal. A phase shifter, an amplifier for amplifying the output signal of the phase shifter, and radiating the output signal from the amplifier in the direction of the transmission beam controlled by the beam control circuit, and receiving the reflected signal from the target. A plurality of element antennas, a plurality of receivers provided corresponding to each of the above 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; An output signal of the buffer memory is input, a beam forming circuit that forms a plurality of the pair of reception beams for each range bin by performing Fourier transform, and a signal received by the pair of reception beams. A monopulse arithmetic circuit that calculates a sum signal and a difference signal for each pair of reception beams from the signal, and an angle and distance of the obstacle for each range bin from the output signal of the monopulse arithmetic circuit, thereby obtaining an altitude difference between the obstacles. And a signal processor for obtaining the following.