JP2855933B2 - Radar signal processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an array antenna and uses a DBF (Digital BeamFormin).
g) search and tracking radar for beamforming by technology;
For example, a ground-mounted DBF radar or a ship-mounted DB
It relates to F radar.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a configuration of a conventional signal processing apparatus for a search and tracking radar using a phased array antenna. In the figure, 1 is an antenna element, 18
Is a phase shifter, 19 is a microwave beam synthesizer, and 5 is a target detection unit.

The conventional apparatus is configured as described above. The signal received by the antenna element 1 of the array antenna is phase-shifted by the phase shifter 18 for each element, and then all elements are shifted by the microwave beam combiner 19. Are added and beam synthesized. The output of the microwave beam combiner 19 is input to the target detection unit 5 and subjected to target detection processing.
The detection result is output to the subsequent signal processing unit or target information processing unit.

The above radar signal processing method will be described with reference to FIG. FIG. 4A shows the relationship between the target approaching and approaching the array antenna and the Doppler frequency, and FIG.
Indicates the relationship between the target moving in the elevation direction, that is, the vertical direction with respect to the array antenna, and the Doppler frequency. In the figure,
20 is an array antenna, 21 is a fixed target such as a mountain, 22
Is a target facing and approaching the array antenna 20, 23 is a velocity vector of the facing approach target 22, and 24 is a fixed target 21.
25, the power spectrum of the opposing approach target 22, 26 is the target moving vertically, 27 is the velocity vector of the target 26 moving vertically, and 28 is the power spectrum of the target 26 moving vertically. .
In a conventional radar signal processing method, a received signal from each element of an array antenna is beam-synthesized in an analog manner, and a target is detected or target motion parameters are used using a temporal change amount of a phase of the synthesized wave, that is, a Doppler frequency. Was being extracted. Therefore, as shown in FIG. 4A, the Doppler frequency of a fixed target such as a mountain is zero, whereas the Doppler frequency of an opposing approaching target is not zero, so that the target can be separated from the fixed target. Was calculated from the time change rate of the Doppler frequency. On the other hand, when the target moves in the vertical direction as shown in FIG. 4B, the target Doppler frequency is fixed to zero like the fixed target, so that the target cannot be separated from the fixed target from the Doppler frequency. In addition, even when the target is moving with acceleration, the acceleration cannot be obtained from the time change rate of the Doppler frequency.

[0005]

[Problems to be Solved by the Invention] As a future trend of a target targeted by a radar, it is expected that mobility will be further improved and stealth will be further advanced in the future. On the other hand, diversification of electromagnetic interference and improvement of interference capability are expected as future trends in the environment in which radars are operated. In light of these trends, future search and tracking radars need to respond quickly to targets moving in all directions. In a future radar signal processing method, a target specification is calculated by performing detection and tracking processing for an oncoming approach target as shown in FIG. 4A. However, a vertical as shown in FIG. For targets moving in a direction, for example, those that are fired vertically from above or below the ground, or on a ship, the problem is that they are disengaged from the radar during the initial phase after firing, i.e., while moving vertically. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and is directed to a target moving in a vertical direction, and utilizing a received signal for each antenna element of an array antenna by utilizing the characteristics of a DBF. The purpose of the present invention is to obtain the acceleration of a target that moves in the vertical direction.

[0007]

SUMMARY OF THE INVENTION A radar signal processing method and apparatus according to the present invention determine a phase difference of a received signal between two arbitrary antenna elements of an array antenna having the same azimuth and different elevation angles. Means for calculating the target acceleration moving in the vertical direction by calculating the second derivative of the phase difference with time.

[0008]

According to the present invention, by utilizing the characteristics of the DBF and utilizing the received signal for each antenna element of the array antenna, the target acceleration moving in the vertical direction can be quickly obtained in the signal processing section. .

[0009]

【Example】

Embodiment 1 FIG. FIG. 1 is an overall configuration diagram of an embodiment according to the present invention. In the figure, 1 and 5 are the same as those of the above-mentioned conventional device, 2 is a receiver, 3 is an A / D converter, 4 is a digital beam forming unit, 6 is a phase detecting unit, 7 is a phase difference calculating unit, 8 is a phase difference time differential operation unit, 9 is a delay unit, 10 is a time change amount calculation unit, 11 is a differential operation unit, 12 is a vertical acceleration calculation unit, and 13 is target distance information output from the target detection unit 5. It is.

A method of processing a radar signal according to the present invention will be described with reference to FIG. In the figure, reference numerals 14 and 15 indicate the target position and the arrival direction of the radio wave at time t = t1. Similarly, at 16 and 17 time t = t2 (t2> t
The target position and the arrival direction of the radio wave in 1) are shown. At time t = t1, a radio wave from a target existing at a distance R and an elevation angle θ1 is received by each antenna element of the array antenna. At this time, any two elements having the same azimuth angle but different elevation angles, for example, Akl and Akm Phase difference of the signal received at
t1 is represented by the following equation.

[0011]

(Equation 1)

Similarly, at time t = t2 (t2> t1), the phase difference Δt2 of the received signal between the two antenna elements Akl and Akm is expressed by the following equation.

[0013]

(Equation 2)

On the other hand, from time t = t1 to time t = t2 (t
The distance Rv that the target travels in the vertical direction during 2> t1) is expressed by the following equation.

[0015]

(Equation 3)

Accordingly, the target acceleration Av that moves in the vertical direction is expressed by the following equation using the equations (1) to (3).

[0017]

(Equation 4)

In the radar signal processing device configured as described above, a signal received by the antenna element 1 is converted into a digital reception signal through a receiver 2 and an A / D converter 3 provided for each element. After that, the data is input to the digital beam forming unit 4 and beam-formed. The target detection unit 5 performs a target detection process on the beam forming result, and outputs the detection result and information on the extracted target to a subsequent signal processing unit or target information processing unit. At the same time, the distance information R of the target information obtained by the target detection unit 5 is output to the vertical acceleration calculation unit 12. Also, of the digital reception signals of all the antenna elements input to the digital beam forming unit 4, any two elements having the same azimuth and different elevation angles, for example, Ak
The received signals of the elements of l and Akm (k: the column number in the antenna element array, l and m: the row number in the antenna element array) are input to the phase calculating unit 6, and the instantaneous instantaneous phase of the received signal of each element is calculated. Is done. Phase difference calculator 7
Then, the result calculated by each phase calculator 6 is used as an input, and the phase difference of the received signal between the two antenna elements at each time described by ψ in Equation 4 is calculated. In the phase difference time differential calculation unit 8, first, the output of the phase difference calculation unit 7 is delayed by Δt by the delay unit 9, and the time change amount calculation unit 10 calculates the change amount Δψ of the phase difference due to the time change of Δt. Arithmetic unit 11
Is multiplied by 1 / Δt to calculate the time derivative Δψ / Δt of the phase difference. Similarly, in the vertical acceleration calculation unit 12, the phase difference time differential calculation unit 8 is also operated by the delay unit 9.
, And the time change amount calculating section 10 calculates the change amount of the time derivative Δψ / Δt of the phase difference due to the time change, and the differential operation section 11 calculates the time derivative Δψ / Δ of the phase difference.
The constant λ / (2πdl) according to Equation 4 with respect to the time variation of t
m) and the target distance R output from the target detection unit 5 and the reciprocal 1 / Δt of the delay time Δt by the delay unit 9 are multiplied to calculate the target acceleration Av moving in the vertical direction, and the signal processing unit or Output to the target information processing unit. In Equation 4, the wavelength λ of the radio wave and the antenna element interval dlm are known.

[0019]

According to the present invention, as described above,
Taking advantage of the characteristic of F, the phase difference of the received signal between the two elements is obtained from the digital received signal of any two elements having the same azimuth and different elevation angles among the antenna elements of the array antenna, and the second-order differentiation of the phase difference with time Can be used to calculate the acceleration of a target that moves in the vertical direction.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a radar signal processing device according to a first embodiment of the present invention.

FIG. 2 is a principle diagram of a radar signal processing method according to the present invention.

FIG. 3 is an overall configuration diagram of a conventional radar signal processing device.

FIG. 4 is a diagram illustrating a relationship between a target motion direction and a Doppler frequency for explaining a conventional radar signal processing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna element 2 Receiver 3 A / D converter 4 Digital beam forming part 5 Target detecting part 6 Phase calculating part 7 Phase difference calculating part 8 Phase difference time differential calculating part 9 Delay device 10 Time change calculating part 11 Differential calculating part 12 Vertical acceleration calculator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-279886 (JP, A) JP-A-4-147079 (JP, A) JP-A-5-150037 (JP, A) JP-A-2- 208588 (JP, A) JP-A-2-275385 (JP, A) JP-A-4-154301 (JP, A) JP-A-2-162284 (JP, A) JP-A-3-1488081 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 13/50-13/64 G01S 7/02

Claims (1)

(57) [Claims] 1. An array antenna for receiving a radio wave from a target, a receiver provided for each antenna element of the array antenna, and an A for converting an analog reception signal output from each receiver into a digital reception signal. / D converter,
A digital beam forming unit that performs digital beam forming by using an output of the A / D converter as an input; a target detecting unit that performs target detection from an output result of the digital beam forming unit; and an output of the A / D converter. .., Tn (t1) of the two received signals having the same azimuth and different elevation angles among the digital received signals.
<T2 <... <Tn) and time t1, t2,..., Tn (t1 <t2 <... <T) based on the calculation result of each phase calculator for the two elements.
n) a phase difference calculator for calculating a phase difference between the two elements, a delay unit in a phase difference time differential calculator for delaying an output of the phase difference calculator, and an output of the phase difference calculator. A time change amount calculation unit in a phase difference time differentiation operation unit for obtaining a difference from an output of the delay unit; and a phase difference time differentiation operation for multiplying an output of the time change amount calculation unit by a reciprocal of a delay time by the delay unit. A differential operation unit in the unit, a delay unit in the vertical acceleration calculation unit that delays the output of the differential operation unit,
A time change calculating unit in a vertical acceleration calculating unit for obtaining a difference between an output of the differential calculating unit and an output of a delay unit in the vertical acceleration calculating unit; and a time in the vertical acceleration calculating unit. The output of the change amount calculation unit is multiplied by the target distance output from the target detection unit and the reciprocal of a delay time by the delay unit in the vertical acceleration calculation unit, and a constant. A radar signal processing device comprising: a differential calculation unit in a vertical acceleration calculation unit that outputs to the information processing unit.