JPH0695140B2 - Surface mapping radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to, for example, an airborne surface mapping radar device for mounting an aircraft of a radar platform.

[Conventional technology]

Fig. 2 is a diagram showing a conventional airborne surface mapping radar device, in which (1) is a phased array antenna that radiates a transmitted wave in a space in a specific direction and receives a reflected wave, (2 ) Is a beam controller that controls the beam direction of the phased array antenna (1) by controlling the phase of the array antenna module, and (4) supplies a signal from the transmitter to the phased array antenna (1). , Circulator that supplies the received signal to the receiving detector, (5) High frequency (RF)
Stable local oscillator (STALO) that generates a pulse, a pulse modulator that forms a transmission pulse, and a stable local oscillator (S
TALO) (5) and an up converter that generates a transmission wave from a pulse modulator (6), (8) a radar timing generator that generates the control timing of the radar device such as the transmission pulse repetition frequency, and (9) an intermediate frequency A coherent oscillator (COHO) that oscillates (IF), (10) is a mixer that mixes the received signal with the high frequency (RF) signal of the stable local oscillator (STALO) (5) and converts it to a center frequency, (11 ) Is an IF amplifier that amplifies the intermediate frequency reception signal, (12) is a phase detector that outputs the video reception signal from the output of the coherent oscillator (COHO) (9) and the intermediate frequency reception signal, and (13) is the video reception signal Is an analog-to-digital A / D converter, (14) is an inertial plate-form sensor that detects the motion of the radar platform, and (15) is the motion data from the inertial plate-form sensor (14). Received from the beam direction A phase compensation data generator for calculating the phase change of the signal, (16) a phase compensator for correcting the phase of the received signal using the phase compensation data from the phase compensation data generator (15), and (17) a beam The Doppler frequency corresponding to the azimuth direction in
FFT calculator, (20) is a radar controller that sets the pointing direction of the antenna beam and radar timing, and (21) is a display that displays the image data output from the FFT calculator (16). .

The conventional airborne surface mapping radar is constructed as described above, and the radar platform (2
Targets (X, Y, Z) in the direction of squint angle A and elevation angle B from 2)
The transmitted wave is radiated from the phased array antenna (1) toward the ground surface, and the reflected wave from the ground surface is received by the phased array antenna (1), passes through the circulator (4), and is mixed. The signal from the stable local oscillator (STALO) (5) is converted to an intermediate frequency by the device (10), and the coherent oscillator (COH
The signal from O) (9) is converted into a video reception signal by the phase detector (12) and digitized by the A / D converter (13). The distance between the radar and the target point at the observation start time (t = 0) is calculated from the motion data (Vx, Vy, Vz) of the platform from the inertial platform sensor (14) and the beam pointing direction. And the distance between the radar and the target point at the observation time t is R (t), the phase change dθ of the received signal is
It is represented by (1).

dθ = 2π / λ (R (t) −Ro) ≈−4π / λ (VxtcosAcosB + VytsinAcosB + VztsinB)
...... (1) Generate the phase change amount calculated by equation (1) with the phase compensation data generator (15) and receive it with the phase compensator (16) so that the Doppler frequency at the center of the main beam becomes zero. Phase compensation is applied to the signal, and from the principle of Doppler beam shaping, the FFT calculator (17) detects the Doppler frequency corresponding to the azimuth direction in the beam to visualize the azimuth direction and display it. A high resolution surface map image can be displayed on 21).

[Problems to be Solved by the Invention]

The following problems have been encountered in the above-described conventional aircraft surface mounting mapping radar device. That is,
In the conventional airborne surface mapping radar, the accuracy of the inertial plate-form sensor is not so good, and there is some error in the actual motion of the plate-form and the data detected by the sensor. For this reason, there is a problem in that the Doppler frequency at the center of the main beam cannot be completely compensated to zero with respect to the phase change of the received signal, which causes the image to be defocused in the imaging by the FFT calculation.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a surface-mounted mapping radar device for an aircraft, which can obtain high-quality images.

[Means for Solving the Problems]

The surface-mounted mapping radar device for mounting on an aircraft according to the present invention uses a sum pattern and a difference pattern in the azimuth direction in which the center of the main beam is a null point by the monopulse method, and calculates the difference pattern from the phase difference between the sum pattern and the difference pattern. We propose a device that detects the Doppler frequency at the null point, calculates the phase compensation error from the Doppler frequency at the center of the main beam, and corrects the phase compensation.

[Action]

According to the present invention, a high quality image can be obtained by detecting an actual fluctuation of the plate worm and an error of data detected by the inertia plate ohm sensor and correcting the error component.

[Embodiment] FIG. 1 is a view showing an embodiment of the present invention, in which (3) represents a sum pattern of monopulses and a difference pattern signal from a signal received by a phased array antenna (1). Monopulse comparator to be made, (10a) and (10b) are the first and second mixers, (11a) and (11b) are the first and second IF amplifiers, and (12a) and (12b) are the first and second mixers. 2 phase detector, (13
a) and (13b) are first and second A / D converters, (16a) and (16
b) is the first and second phase compensators, (17a) and (17b) are the first and second FFT calculators, and (18) is the first and second FFT calculators (17a) and (17b). ) Input signal to detect the complex difference of the sum pattern and the phase difference of the difference pattern, (19) is the Δ ・ Σ calculator, and the output of (18) becomes the center of the main lobe. It is a center frequency detector that detects the frequency of the null point of the difference pattern.

In Fig. 3, the transmitted wave is radiated from the phased array antenna (1) from the radar platform (22) toward the ground surface as the target (X, Y, Z) in the squint angle A and elevation angle B directions. Then, the reflected wave from the ground surface is received by the phased array antenna (1), and the received signals of the sum pattern and the difference pattern are created by the monopulse comparator (3), and the received signal of the sum pattern is the circulator (4). And the received signals of the sum pattern and the difference pattern pass through the first and second mixers (10
In a) and (10b), the signal from the stable local oscillator (STALO) (5) is converted to the intermediate frequency, and the coherent oscillator (COHO)
By the signal from (9), the first and second phase detectors (12a),
It is converted to a video reception signal at (12b) and is digitalized at the first and second A / D converters (13a) and (13b). The amount of phase compensation (Vx, Vy, Vz) of the platform from the inertia platform sensor (14) and the amount of phase compensation for the phase change of the received signal from the beam pointing direction are expressed by equation (1). And the error component of the inertial plate-form sensor is (Ex, Ey, Ez), the output of the first and second phase compensators (16a) and (16b) of the received signal at the observation time t is
The phase error component represented by (2) is included.

Eθ (t) ≈−4π / λ (ExtcosAcosB + EytsinAcosB +
EztsinB) …… (2) FFT calculator for received signals of sum pattern and difference pattern
The Doppler frequency is detected by (17) and the Δ ・ Σ calculator (18)
When the complex complex of the sum pattern of the outputs of the first and second FFT calculators (17a) and (17b) and the difference pattern are subjected to complex multiplication and the imaginary part is taken out, a curve (23) as shown in Fig. 4 is obtained, The center frequency detector (19) detects the frequency of the null point (24). The frequency of this null point is the frequency of the beam center of the main lobe, and this frequency is expressed by Eq. (3) from the phase error component of Eq. (2).

Efd = 1 / (2π) dEθ (t) / dt ≒ −2 / λ (ExtcosAcosB + EysinAcosB + EzsinB) …… (3) Phase compensation error Eθ (t) by integrating this frequency at the observation time and multiplying by the pi 2π Can be asked. By applying this phase compensation difference to the phase compensation data generator (15), the phase compensation data is corrected, and the phase compensation is performed again by the first and second phase compensators (16a) and (16b). The Doppler frequency at the center of can be made zero, and the defocus of the image can be eliminated in the visualization by FFT calculation.

〔The invention's effect〕

As described above, the present invention, as described above, can detect the null point of the difference pattern from the phase difference between the sum pattern and the difference pattern by the monopulse method even if there is an error in the actual fluctuation of the plate ohm and the data detected by the inertia plate ohm sensor. By detecting the Doppler frequency of the main beam, calculating the phase compensation error from the Doppler frequency at the center of the main beam, and providing the means for correcting the phase compensation, it is possible to obtain a high-quality image without defocus. There is.

[Brief description of drawings]

FIG. 1 is a diagram of an aircraft-mounting surface mapping radar device showing an embodiment of the present invention, FIG. 2 is a diagram showing a conventional aircraft-mounting surface mapping radar device, and FIG. 3 is a radar platform. FIG. 4 is a diagram showing a geometrical relationship with a target ground surface to be mapped, and FIG.
It is a figure which shows the output signal of a (sigma) calculator. In the figure, (1) is a phased array antenna, (2) is a beam controller, (3) is a monopulse comparator, (4) is a circulator, (5) is a stable local oscillator (STALO), and (6) is a pulse. Modulator, (7) Upconverter, (8) Radar timing generator, (9) Coherent oscillator (COHO) that oscillates intermediate frequency (IF), (10) Mixer, (11) IF amplifier , (12) is a phase detector, (13) is an A / D converter, (14) is an inertial plate-form sensor, (15) is a phase compensation data generator, (16) is a phase compensator, (17). Is FFT calculator, (18) is Δ
Σ arithmetic unit, (19) is a center frequency detector, (20) is a radar controller, (21) is a display, and (22) is a radar platform. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An antenna for transmitting a transmitted wave from the sky at a predetermined angle to the ground and receiving a reflected wave from the ground, a beam controller for controlling the direction of the beam of the antenna, and the antenna received by the antenna. A monopulse comparator that generates a sum pattern signal and a difference pattern signal of monopulses from the generated signal, a local oscillator that generates a high frequency signal, and a coherent oscillator that oscillates an intermediate frequency (IF) signal,
The sum pattern signal and the difference pattern signal are mixed with the harmonic frequency signal of the local oscillator, respectively, and the intermediate frequency (I
F), the first and second mixers, and the first and second mixers
1st and 2nd IF which respectively amplify the output signal of the mixed note of
An amplifier, first and second phase detectors for outputting a video reception signal from the output signal of the coherent oscillator and the output signals of the first and second IF amplifiers, respectively, and the first and second phases First and second A / D converters for converting the output signals of the detectors into digital signals, an inertial platform sensor for detecting fluctuations of the Rede platform, and fluctuation data and beam pointing from the inertial platform sensor The phase of the output signal of the phase compensation data generator that calculates the phase change of the received signal from the direction and the output signals of the first and second A / D converters are respectively compensated using the output signal of the phase compensation data generator. The first and second phase compensators and the sum pattern signal and the difference pattern signal phase-compensated by the first and second phase compensators are respectively Fourier-transformed to correspond to the azimuth direction. Inputting the output signals of the first and second FFT calculators for detecting the Doppler frequency and the first and second FFT calculators, and detecting the phase difference between the conjugate complex number of the sum pattern and the difference pattern Σ calculator, a center frequency detector that detects the frequency of the null point of the difference pattern that is the center of the main lobe from the output of the Δ / Σ calculator, and the beam center of the main lobe detected by the center frequency detector From the first FFT operation and the radar control section that performs control for correcting the phase compensation data of the phase compensation data generator, the antenna beam pointing direction and the radar timing using the frequency of A surface mapping radar device, comprising: a display for displaying output image data.