JPS61138188A - Radar equipment - Google Patents

Abstract

PURPOSE:To make possible the direct measurement of the magnitude in a target cross range direction accompanying rotation motion by subjecting the demodulated signal of a sum channel signal and difference channel signal obtd. by using a monopulse antenna to Doppler frequency resolution. CONSTITUTION:The modulated signal of the sum channel signal and difference channel signal obtd. by using the monopulse antenna 41 and following up the target motion is subjected to the Doppler frequency resolution by Fourier transform circuits 711, 712. The incoming bearings of the reflected wave are determined for each of the same Doppler frequency components by measured angle processing circuits 721-72n. The distance of the cross range direction is then determined by multipliers 731-73n in accordance with the distance from the antenna 41 up to the target and the determined incoming bearings of the reflected wave. The factor to convert the coordinates of the Doppler frequency to the coordinate in the cross range direction is determined in a conversion factor setting circuit 740 by using at least two distances corresponding to the optional Doppler frequency component out of the distances in the cross range direction. The target is thus expressed with the coordinates in the distance direction and cross range direction, i.e., the coordinates indicating directly the size.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radar device, and particularly to a device suitable for measuring the physical size of a target that makes a motion including rotational motion.

[Technical background of the invention]

FIG. 3 shows a schematic configuration of a general radar device.

In this radar device, a highly stable oscillator 10 is a circuit that generates a stabilized signal of a predetermined frequency, and the generated signals are supplied to a transmitter 20 and a receiver 50, respectively. The transmitter 20 generates a pulse signal having a required repetition period based on this input signal, and supplies this to the antenna 40 via the transmitter/receiver switch 30. As a result, the same pulse signal is emitted from the antenna 40 as a transmission signal. On the other hand, the reflected wave from the target is
and is supplied to the receiver 50 via the transmitter/receiver switch 30. As described above, this receiver 50 is also supplied with the oscillation signal of the highly stable oscillator 10,
The received signal is mixed with this oscillation signal and demodulated.

This demodulated signal is supplied to the display 60 and displayed appropriately.

Incidentally, microwave band radar is generally known to be unaffected by weather and the like, but it has been considered difficult to even know the shape of a target using this microwave band radar. This is because the spatial resolution of the radar itself is coarse compared to the size of the target. Therefore, as a technology to overcome this problem, synthetic aperture rake (hereinafter abbreviated as SAR) was proposed and put into practical use. As is well known, SAR is a system in which an antenna and a transmitting/receiving device are mounted on a platform that moves at high speed, and echo data of the target is collected at numerous locations in space as the antenna and transmitting/receiving device move. This creates directivity equivalent to that of an antenna with a large aperture length, thereby increasing the resolution of the radar device.

However, if we take into account these functions of SAR, on the contrary, as long as the target object is moving, it is possible to obtain high resolution equivalent to that of SAR using ordinary fixed radar. It can also be inferred.

As an example of this, a method of obtaining high-resolution information from a rotating target will be described below with reference to FIG.

Now, if a certain point P on the target is rotating in the manner shown in FIG. is received.

However, λ is the wavelength of the radar transmission wave, and if these observations are made continuously for a time T, then the resolution with respect to the Doppler wave number feL is
4 becomes, and this (this corresponds to the resolution △ in the X-axis direction in the same figure)
X can be expressed as iζ. Note that 80 in this equation (3) is as follows, and represents the total angle through which the target (point P) rotates during the time T.

In this way, high spatial resolution can be obtained by observing a rotating target over an appropriate time span. However, the resolution obtained with this (3-n formula) is the resolution in the direction perpendicular to the distance direction (hereinafter, this direction is referred to as the cross-range direction, and the resolution in this direction is referred to as the cross-range resolution), and the resolution in the distance direction is It is assumed that this is obtained by pulse compression such as modulation within the transmission pulse.

[Problems with background technology]

Although the above-mentioned method is effective in improving the resolution by resolving the target into cross-range directions, it is not possible to directly know the size of the same target in the cross-range direction.
As a radar device, there were still issues to be solved.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a radar device that can also directly measure the size in the cross-range direction of a target that performs a motion that includes at least rotational motion.

(Summary of the Invention) In the present invention, a monopulse antenna is used as the antenna, which instantly detects the azimuth pointing error of the antenna with a single pulse response and outputs a sum channel signal and a difference channel signal according to the detection error. Then, the demodulated signals of the sum channel signal and the difference channel signal obtained by following the movement of the target are subjected to Doppler frequency decomposition to obtain the same Doppler frequency based on these two types of signals each having the same Doppler frequency component. The direction of arrival of the reflected wave for each component is determined, and then the distance from the monopulse antenna to the target determined by the arrival time of the reflected wave and the deviation from the front direction of the monopulse antenna of the target based on the direction of arrival of each reflected wave determined are calculated. Find the distance in the range direction, and then use at least two of these found distances in the cross-range direction that correspond to arbitrary Doppler frequency components to find a coefficient for converting the coordinates of the pibbler frequency into the coordinates in the cross-range direction. From this, the above target is expressed by coordinates that can directly represent the size, such as coordinates in the distance direction and coordinates in the cross range direction, and it is naturally possible to know the spatial size of the target. become able to.

〔Effect of the invention〕

As described above, according to the radar device according to the present invention, since it is possible to directly measure the size of a target in the cross-range direction that involves rotational motion, it is very useful for determining the spatial properties of the target. It can provide useful data.

Embodiment of the Invention] Figure 1 shows an embodiment of the radar device according to the invention. However, in this FIG. 1, elements having basically the same functions as the elements shown in FIG.

As is clear from FIG. 1, this embodiment uses a monopulse antenna 41 as the antenna 40 (see FIG. 3), and a new received signal processing device is installed between the receiver 50 and the display 60. 70 is interposed therebetween. As described above, the monopulse antenna 41 is an antenna that instantaneously detects the azimuth pointing error of the antenna with a single pulse response and outputs a sum channel signal and a difference channel signal according to the detection error, and also outputs a received signal. The processing device 70 determines the coordinates of the target (not shown) in the cross-range direction based on the sum channel demodulated signal Σ and the difference channel demodulated signal Δl output from the monopulse antenna 41 and demodulated by the receiver 50. This is a device that forms the main part of this invention. The functions of this received signal processing device 70 will be described in detail below with reference to FIG.

The Fourier transform circuits 711 and 712 are connected to the receiver 5.
This circuit decomposes the difference channel demodulated signal Δ and sum channel demodulated signal Σ added from 0 into Doppler frequency components for each different Doppler frequency component, that is, for each distance, and the decomposed signals Δ1, Δ2 . ...Δ.

and Σl, Σ2゜...Σ. are signals (for example, signal Δ1 and signal Σ
1. (signal Δ2, signal Σ2, etc.) are applied to separate angle measurement processing circuits 721, 722, . . . , 720. Here, as shown in FIG. 2(a), the above echo signal Σ is expressed by orthogonal coordinate transformation of the range R (distance to the target determined by the reflected wave arrival time) and the Doppler frequency fd, respectively. Σ. Although it is possible to know the shape of the target by displaying it, the size in the cross-range direction is unknown. Therefore, in this processing device 70, the following processing is further performed by the circuits after the angle measurement processing circuits 721 to 72n. These angle measurement processing circuits 721 to 72n each have a signal pair (ΔX) having the same Doppler frequency component.

Σ1), (Δ2, Σ2), ... (Δ., Σn) is a circuit that calculates the direction of arrival of reflected waves, that is, the angle measurement value for each same Doppler frequency component (Characteristics of monopulse antenna - above, Δ For each value of /Σ, the corresponding angle measurement value θ is fixedly determined), and each of the angle measurements θ1, θ2, and θn thus determined is further processed by a multiplier 731
, 732. ...Added to 73n. Multiplier 731~
73n are the accepted angle measurement values θ1 to θ, respectively. It operates to multiply by the range R mentioned above. In other words, by this. coordinate values Xl, Xg,...X in the cross range direction corresponding to each Doppler frequency component regarding the same target.
Q will be obtained. Here, these Doppler frequency fd and the coordinate X in the cross range direction are
As shown in the formula, fd=kx However: Since there is a proportional relationship called a proportional coefficient, if this coefficient k is set, the above coordinate X in the cross range direction can be linearly approximated for all Doppler frequencies. , it can be seen that coordinate transformation from the same Doppler frequency to cross-range coordinates is possible. The conversion coefficient setting circuit 740 that receives the coordinate values xI−xn is a circuit that estimates and sets the coefficient k described above from these six values by, for example, the method of least squares. Figure 2 (
As shown in 1)), the shape of the target can be expressed using coordinates such as range R and cross range X, both of which can directly represent the size.

In addition, in this embodiment, the conversion coefficient k is estimated and set based on a large number of values such as the cross-range direction coordinate values X1-Xn corresponding to each Doppler frequency component subjected to the Doppler frequency decomposition, so that the conversion coefficient k can be estimated and set fairly accurately. Basically, as long as at least two of these coordinate values X1 to XQ are known, it is possible to estimate the same coefficient. The configuration can also be simplified.

In addition, in the explanation so far, for convenience, it has been assumed that the target is in rotational motion, but the target does not necessarily have to be in pure rotational motion, and may be at least in motion that includes rotational motion. This invention can be applied as long as there is. That is, in this case, it is sufficient to omit the motion part related to the linear motion of the target and focus only on the motion part related to the rotational motion.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the radar device according to the present invention, FIG. 2 is a diagram showing the functions of the embodiment device shown in FIG. 1, and FIG. 3 is a general diagram of a conventional radar device. FIG. 4 is a schematic diagram illustrating a method for high-resolution observation of a rotating target using a fixed radar.

Claims (1)

[Claims] A radar device that radiates a pulse signal from a monopulse antenna to a target that makes a motion that includes at least rotational motion, and measures the spatial properties of the target based on the reflected waves, the sum channel obtained from the monopulse antenna. a first calculation means for decomposing the demodulated signal at any time of the signal and the difference channel signal into Doppler frequency, and two types of signals each having the same Doppler frequency component of the decomposed sum channel demodulated signal and the difference channel demodulated signal; a second calculating means for determining the direction of arrival of the reflected waves for each same Doppler frequency component based on the distance from the monopulse antenna to the target determined by the arrival time of the reflected waves and the direction of arrival of each of the reflected waves determined by the second calculation means; A third calculating means calculates the deviation distance from the monopulse antenna front direction of the target, and at least two of these calculated deviation distances corresponding to arbitrary Doppler frequency components are used to calculate each Doppler frequency. a fourth calculating means for determining a coefficient to be converted into a distance of the corresponding deviation, and measuring the spatial size of the target subjected to Doppler frequency resolution based on the determined coefficient.