JPH045154B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a target tracking system, and particularly to a tracking system for tracking a target that reflects or emits electromagnetic waves.

In principle, methods for tracking targets using electromagnetic waves can be broadly divided into active methods and passive methods. The active method is to emit electromagnetic waves such as a microwave band toward a target and receive a reflected signal that hits the target and is reflected.

The passive method receives thermal energy radiated by objects in the natural world as a signal. Thermal energy radiated by an object is determined by Planck's blackbody radiation law and spans all frequency bands from 0 to infinity. Therefore, the passive method is a method of simultaneously receiving weak electromagnetic waves emitted by a target, etc., and a reflected signal resulting from the target reflecting the weak electromagnetic waves emitted by the surrounding atmosphere and objects. In the passive method, the reception frequency of the receiver receives continuous frequency bands emitted and reflected by the target, so it can be set to any reception frequency and bandwidth depending on the purpose (actually, microwave (often set to an appropriate frequency band in the infrared region), it is not particularly necessary to determine the frequency of electromagnetic waves emitted and reflected by the target.

The principle of tracking using the passive method will be explained using FIGS. 5 and 6.

Objects emit electromagnetic waves depending on their surface temperature. In the radio wave region, the radiated power W _Z is expressed by the following equation.

W _Z = 8πkT _Z / λ ² ...(1) where k: Boltzmann's constant T _Z : Brightness temperature, expressed as εT (ε: emissivity, T: absolute temperature) λ: Wavelength Other radio waves When a radiation source is present, the apparent brightness temperature is observed due to the radiation from the object itself and reflections from other radiation sources.

Now, when only the ground surface is viewed from above with a passive tracking device (radiometer such as a microwave) 20 as shown in FIG. 5, the apparent brightness temperature T _B of the ground surface is expressed by the following equation.

T _B = (1-1/L) T _OO +ε _b・T _b /L + (1-ε _b ) T _SKY /L ...(2) However, L: Attenuation due to the atmosphere T _OO : Earth surface and passive tracking device Average path temperature between ε _b : Emissivity of the earth's surface T _b : Temperature of the earth's surface T _SKY : Sky temperature Similarly, when viewing only the target (metal) on the earth's surface with the passive tracking device 20, the apparent brightness temperature of the target T _T is expressed by the following formula.

T _T = (1-1/L) T _OO + ε _t・T _t /L + (1-ε _t ) T _sky /L ...(3) where, ε _t : Emissivity of target T _t : Temperature of target Detection of a target on the ground surface is performed by the apparent brightness temperature change, that is, the apparent brightness temperature difference △T between the ground surface and the target, so if we take the difference between T _B and T _T , △T = T _B −T _T =(1/L) {ε _b (T _b −T _sky ) −ε _t (T _t −T _sky )} ...(4). Normally, it is considered that the temperatures of the ground surface and the target are almost the same, so if T _b = T _t , equation (4) becomes the following equation.

△T(1/L) {(ε _b −ε _t ) (T _b −T _sky )} ...(5) In formula (5), L>0, T _b −T _sky >0, ε _b >ε _t
Therefore, the apparent brightness temperature of the ground surface and the target is the 6th
The relationship is as shown in the figure. Here, the passive tracking device 20
We choose the atmospheric window at _the frequency _of
0.2, T _b ≒ 290K, T _sky ≒ 100K, equation (5) is (assuming L = 1.2) △T = (1/1.2) {(0.9 − 0.2) (290 − 100)} ≒ 110K ……( 6) becomes.

On the other hand, the minimum temperature resolution ΔT _nio of the passive tracking device 20 is expressed by the following equation.

However, T _so : Passive tracking device noise temperature = T _R + T _A T _R : Receiver noise temperature T _A : Antenna background noise temperature a: Constant {2 in Dicke method (an example of radiometer reception method)} B _HF : Bandwidth of high frequency circuit Z _I : Integral time Let's substitute typical values into equation (7).

T _so = T _R + T _A = (F _N -1) T _A + T _A F _N : High frequency circuit loss, receiver noise figure = 13 (approx.
11dB) T _A :290K T _so =13×290=3770K a=2 B _HF =550MHz Z _I =50ms △T _nio = (3770×2)/√500×10 ⁶ ×50×10 ^-3 ≒1.5K … ...(8) From equations (6) and (8), it is possible to detect a target on the ground surface from above with the passive tracking device 20.

Note that, as a receiver used in the passive tracking device 20, a highly sensitive receiving method (for example, Deitske method) that can eliminate noise generated inside the receiver and fluctuations in receiver gain is known.

Now, conventionally, when a target tracking method for detecting and capturing a target that reflects or emits electromagnetic waves is configured as a tracking device that uses both an active method and a passive method, the active method and passive method tracking device ( (hereinafter referred to as "active/passive tracking device") was adopted. In the device shown in FIG. 4, initially, in order to improve the detection and acquisition of targets at long distances, the transmitter/receiver switch 2 is switched to the transmitter side by the transmitter/receiver switch signal generator 12, and the electromagnetic waves (hereinafter referred to as "electromagnetic waves") generated by the transmitter 3 are (referred to as "radio waves")
is emitted from the antenna 1, and then the transmitter/receiver switch 2
switch to the receiving side. The radio waves emitted from antenna 1 are targets, backgrounds, etc. (hereinafter referred to as "targets, etc.")
reflected by. A part of the reflected signal (hereinafter referred to as the "reflected received signal") passes through the antenna 1 and enters the active receiver 5 via a path switched to the active side by the active/passive switch 4, where it is processed such as signal detection. After that, the azimuth error and elevation angle error (hereinafter referred to as "error angle") are detected by the angle error detector 8 via the active/passive switch 7, and a tracking signal is generated. After amplification, the servo drive device 10 directs the antenna axis toward the target and performs active target tracking.

However, with the active method, when tracking a target at close range or close range, the fluctuation of the reflected reception signal and the fluctuation of the error angle signal (hereinafter referred to as "signal fluctuation") become large, making it difficult to achieve good acquisition and tracking. There are cases.

On the other hand, the passive method receives weak radio waves emitted and reflected by targets, etc., so the distance at which the target can be detected is short, but the short-range target tracking performance is good because the signal fluctuation is small. Therefore, when a target detected and captured using the active method at a long distance approaches a short distance, there is a need to switch the tracking method from the active method to the passive method to obtain good tracking characteristics.

Switching from the active method to the passive method is performed using the switching distance Rc set in advance in the switching signal generator 11 in the active/passive tracking device shown in Fig. 4.
and the active/passive tracking device measured using the active method and the distance Rt to the target,
When Rc≧Rt is satisfied, switch to passive method. That is, the active/passive switch 4,
7 to the passive side, and tracking using the passive receiver 6 is performed.

(Problem to be solved by the invention) However, in the passive method, the magnitude of the received signal of the target etc. (hereinafter referred to as "radiated received signal") is
Since attenuation is affected by environmental conditions such as weather, there may be cases where the target cannot be detected or captured under adverse weather conditions even if Rc≧Rt. In order to avoid such a situation, it is necessary to set Rc to a small value, which reduces the tracking effect of the passive method and makes it impossible to fully demonstrate its performance.

(Means for Solving the Problems) The present invention provides active tracking means and passive tracking means for obtaining an angular error signal of the target from electromagnetic waves reflected and emitted by the target, and
Target tracking that extends the target detection and acquisition distance using the passive method and improves target tracking performance at close range and point-blank range by executing active method tracking operation and passive method tracking operation in a time-sharing manner. The aim is to provide a method. The target tracking method of the present invention includes an active tracking means and a passive tracking means that obtain an angular error signal of the target from electromagnetic waves reflected and emitted by the target, a transmission/reception operation by the active tracking means, and a reception operation by the passive tracking means. a timing generator that generates a signal for switching between the active mode and the passive mode; an active/passive switch that switches between the transmitting and receiving operation of the active mode and the receiving operation of the passive mode based on a signal from the timing generator; and the passive mode tracking means. a reception method switching discriminator that compares the signal strength of the obtained target signal and the reference signal to determine the effectiveness of switching to the tracking operation by the passive method tracking means, and transmits the electromagnetic waves of the active method tracking means. The timing generator outputs a signal for switching to the passive tracking means during the period from 1 to the next transmission or the next or multiple transmissions of electromagnetic waves, and obtains an angular error signal by the active tracking means, and performs passive tracking. The method is characterized in that the operation of obtaining an angular error signal by the means is executed in a time-division manner, and the antenna is driven using either the active or passive angular error signal as determined by the reception method switching discriminator.

(Function) The present invention extends the detection and acquisition distance of a target by the passive method in a target tracking method that utilizes an active method and a passive method (hereinafter referred to as "active/passive tracking method"). In order to reduce the deterioration in target tracking performance, the timing generator 13 shown in FIG. 1 is used to perform the active method operation and the passive method operation in one cycle as shown in FIG. 2 2-a to 2-j. Execute in time division within As a result, the effectiveness of the passive tracking method is increased by optimizing and maximizing the distance over which a target can be captured and tracked by the passive tracking method under the influence of the environment such as the weather.

(Structure of the Invention) The present invention is characterized in that the target acquisition and tracking distance in the passive method can be extended by continuously executing the active method operation and the passive method operation within one cycle. . The configuration of the present invention includes an antenna 1, a radio wave transmitting/receiving switch 2, a transmitter 3, a receiver (hereinafter referred to as "active receiver") 5 that receives and detects a received signal based on the active method, and a receiver based on the passive method. A receiver (hereinafter referred to as a "passive receiver") 6 that receives and detects a received signal, a timing generator 13 that generates a signal to switch and operate both of these receivers, and an active/passive receiver that is switched according to this instruction. a switch 4, an active/passive angle error detector 14 that detects an angle error signal from the outputs of the active receiver 5 and the passive receiver 6, and a reception method switch that determines whether switching to the passive reception method is effective or not. A discriminator 15 is provided. The reception system switching discriminator 15 compares and determines the magnitude of the preset reference signal So and the detection signal Sp of the passive receiver, and executes passive system tracking when, for example, So≦Sp.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Reference is made to FIG. 1, which shows a block diagram of an active and passive tracking device according to the present invention, and to FIG. 2, which shows the states of the device and signal waveforms.

Aim the antenna 1 at _the target object, switch the transmitter/receiver switch 2 to the transmitting side as shown in 2-b by the instruction signal 2-a of the transmitter/receiver switch signal generator 12 at time T0, and switch the transmitter/receiver switch 2 to the transmitting side as shown in 2-b at time _T1. -Emit radio waves like c. Thereafter, the instruction signal 2-a of the transmission/reception switching signal generator 12 causes the transmission/reception switching unit 2 to switch to ₂ -b at time T2.
Switch to the receiving side as in The active/passive switch 4 is a timing generator 1 for time-dividing one cycle from time T ₀ to T ₀ +T _o at time T ₃ .
3, the initial value is set on the active receiver 5 side as shown in 2-e, and the reflected reception signal 2-f enters the active receiver 5, the target signal is detected, and the active/ The passive angle error detector 14 outputs an angle error signal 2-g indicating the target position.

After a certain period of time Td has elapsed after radio wave emission, the active/passive switch 4 is switched to the passive receiver 6 side as shown in 2-e in accordance with the instruction from the timing generator 13, so that the radiated reception signal 2-h is transferred to the passive receiver 6. The target signal is detected, and the angle error detector 14 outputs an angle error signal 2-i indicating the position of the target. The target signal Sp detected in the passive receiver is input to the reception method switching discriminator 15, where it is compared with a preset reference value So and judged. If the Sp intensity is sufficiently large compared to So, the passive method is selected. The angular error signal 2-i, which is the output of the angular error detector 14, is amplified by the servo amplifier 9 and input to the servo drive device 10, thereby driving the antenna 1 so that the angular error is minimized to track the target. Do this. If the reception method switching discriminator 15 determines that the strength of Sp is weaker than that of So,
Active method angle error signal 2 held
-g is amplified by the servo amplifier 9 and inputted to the servo drive device 10 to drive the antenna 1 and perform target tracking such that the angular error is minimized.

By configuring the configuration as described above, it is possible to capture and track targets at the maximum distance using the passive method, which is difficult to grasp clearly in situations where there are changes in environmental conditions such as weather. The tracking point can be stabilized, and the effectiveness of the tracking device can be maintained.

In addition, in the arrangement of the target tracking device 16 shown in FIG. 3, the maximum acquisition and tracking distance by the passive method is for a target (car) 17 traveling at approximately 20 km/hour.
In this case, the distance was approximately 150 m on clear days and approximately 100 m on cloudy days.

(Description of effects of the embodiment) As explained above, the above embodiment includes the antenna 1, the transmitter 3, the active receiver 5, the passive receiver 6, the active/passive angle error detector 14, and the timing generator 13. By combining this with the reception method switching discriminator 15, the operation for capturing and tracking the target using the active method is carried out, and the reception method switching discriminator 15 determines the magnitude of the target detection signal of the passive receiver. Since the target tracking method is switched between the active method and the passive method based on the It is also easy to incorporate into conventional tracking devices, and enables stable tracking that is not affected by radio wave interference at the true target. Moreover, by adopting this configuration, it is also possible to apply tracking using only the active method or tracking only using the passive method depending on the situation.

(Explanation of other embodiments of the invention and examples of diversion to other uses) In the above embodiment, passive mode operation is performed between the transmission of radio waves in active mode operation and the time before the next radio wave transmission. Although the above-mentioned method has been described above, a method in which active operation is performed two or more times and then passive operation is performed also produces similar effects. Furthermore, even after acquisition and tracking by the passive method has become possible, the combined use of the active method and the passive method can produce similar effects under conditions such as radio wave interference or the dissemination of false targets.

By utilizing the angular error signal, the tracking device according to this method can achieve similar effects even when used in guidance methods for guided bullets and artillery shells having a similar structure.

Further, in the above embodiment, the active receiver and the passive receiver are configured separately, but the same effect can be obtained even if the receiver uses both the active method and the passive method.

(Effects of the Invention) As explained above, according to the target tracking method of the present invention, an active method tracking means and a passive method tracking means are provided for obtaining a target angle error signal from electromagnetic waves reflected and emitted by the target, and an active method tracking means and a passive method tracking means are provided. Since the tracking operation of the passive method and the tracking operation of the passive method are executed in a time-sharing manner, it is possible to extend the target detection and acquisition distance by the passive method and improve the target tracking performance at close range and close range. can.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the target tracking method according to the present invention, Fig. 2 is an explanatory diagram showing an example of signal waveforms of each part in Fig. 1, and Fig. 3 shows the maximum target tracking distance in the passive method. An explanatory diagram showing the test method for confirmation, Fig. 4 is a configuration diagram of a conventional target tracking method, Fig. 5 is an explanatory diagram of the principle of passive method tracking, and Fig. 6 shows the brightness temperature difference between the ground surface and the target. It is an explanatory diagram. 1... Antenna, 2... Transmission/reception switch, 3... Transmitter, 4... Active/passive switch, 5...
...Active receiver, 6...Passive receiver, 7
...Active/passive switch, 8... Angle error detector, 9... Servo amplifier, 10... Servo drive device, 11... Switching signal generator, 12... Transmission/reception switching signal generator, 13... Timing generator,
14...active/passive angle error detector,
15... Reception method switching discriminator, 16... Target tracking device, 17... Target (car).

Claims (1)

[Scope of Claims] 1. Active tracking means and passive tracking means that obtain an angular error signal of the target from electromagnetic waves reflected and emitted by the target, a transmission/reception operation by the active tracking means, and a reception operation by the passive tracking means. a timing generator that generates a signal for switching between the transmission and reception operations, an active/passive switch that switches between the transmission and reception operation of the active system and the reception operation of the passive system, based on the signal from the timing generator; a reception method switching discriminator that compares the signal strength of the target signal and the reference signal obtained by the active method to determine the effectiveness of switching to the tracking operation by the passive method tracking means, The timing generator outputs a signal for switching to the passive tracking means until the next transmission or a plurality of electromagnetic wave transmissions, and obtains an angular error signal by the active tracking means, and the passive tracking means and the operation of obtaining an angular error signal according to the above method in a time-sharing manner, and the antenna is driven using either the angular error signal according to the active method or the passive method according to the judgment of the reception method switching discriminator. method.