JPH05107350A - Radar equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a radar device having a function of detecting a target signal and determining whether or not the target signal exceeds a set approach speed. [Structure] A long pulse and a short pulse are transmitted within a dwell time, and a comparator 9 determines the difference between the distance measurement values of the respective received signals and the distance corresponding to the set approach speed. [Effect] It is possible to determine whether or not the approach speed of the target exceeds the arbitrarily set approach speed at the same time as the target detection without waiting for the speed convergence time of the tracking calculation by the computer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device having a pulse compression function.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, MODERN RADA.
R SYSTEM ANALYSISpp431 (AR
FIG. 3 is a block diagram showing a conventional radar device shown in TECH HOUSE, 1988). In the figure, 1 is an antenna, 2 is a receiver, 3 is an A / D converter, 5 is a pulse compressor, 6 is a video integrator, 7 is a signal detector, 8 is a rangefinder, 12 is a calculator, and 15 is It is a transmitter.

The conventional radar apparatus is constructed as described above. For example, the target signal received by the antenna 1 is converted into a digital value by the A / D converter 3 via the receiver 2 and then the video integrator 6 is provided. After being integrated by the signal detector 7 and detected by the signal detector 7, the target distance in the range finder 8 is calculated, and the target tracking calculation is performed by the computer 12 from the target distance.

[0004]

In the conventional radar apparatus as described above, the determination as to whether the target is the high speed approach target or the low speed approach target must be based on the speed calculation result by the target tracking calculation by the computer. Therefore, there is a problem that the determination cannot be made without waiting for the time until the target tracking calculation converges.

Further, even when it is desired to detect only the target in the desired approach speed range, there is a problem that the targets in all the approach speeds are detected.

Further, in the target tracking calculation for calculating the smoothed position specifications and speed specifications of the target, since the input is only the target distance, the speed initial value of the tracking calculation must be zero and the calculation must be started. Therefore, there is a problem in that it takes a long time to converge the calculated speed value to the true target speed. (Normally, it takes more than ten times of observation (input of distance) until the calculated velocity value converges sufficiently, so it consumes more than ten times the search time interval of the radar device. .)

The present invention has been made in order to solve such a problem, and a radar device capable of determining a high-speed target equal to or faster than an arbitrarily set approaching speed at the same time as detecting a target signal and a desired approaching speed range It is an object of the present invention to provide a radar device capable of detecting only the target of 1 and a radar device capable of shortening the convergence time of the target tracking calculation.

[0008]

In a radar device according to the present invention, a transmission wave (hereinafter referred to as a long pulse) that has been frequency-modulated for pulse compression within the dwell time of the radar and an unmodulated signal. Transmitted wave (hereinafter called short pulse)
Both of them are transmitted, and when the frequency-modulated wave for pulse compression is Doppler-modulated by the moving target, the phenomenon that a distance shift proportional to the target speed occurs when the pulse is compressed is used, and the distance measurement value of each signal is calculated. In comparison, a high speed target detection signal is generated when the difference is larger than the distance corresponding to the set speed.

Further, the radar apparatus according to the present invention determines whether or not the difference between the distance measurement values of the respective signals is within the desired approach speed range, and the target distance is input to the computer only within the approach speed range. It was made to be done.

Further, the radar device according to the present invention is such that the target approach speed is calculated from the distance difference between the long pulse and the short pulse and is input to the computer.

[0011]

In the radar apparatus according to the present invention, the long pulse and the short pulse are used in combination to simultaneously detect the target and determine whether the target is equal to or higher than the desired approach speed.

Further, the target tracking calculation is carried out only when it is judged that the speed is equal to or higher than the desired approach speed.

Further, when the target is detected, the approaching speed of the target is input as the initial value of the target tracking calculation by the computer to shorten the convergence time of the tracking calculation.

[0014]

【Example】

Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 to 3, 5 to 8, 12 and 15 are exactly the same as the above conventional device. Reference numeral 4 is a switch circuit, 9 is a comparator, and 16 is a modulation signal generator.

In the radar device constructed as described above, the target signal received by the antenna 1 is converted into a digital value by the A / D converter 3 via the receiver 2 and then by the switch circuit 4. The long pulse is switched to the video integrator 6 via the pulse compressor 5, and the short pulse is switched to the video integrator 6 directly. The distances of the short pulses are calculated by the first and second rangefinders 8a and 8b, respectively, and compared. Input to the container 9. Here, the switch circuit 4 receives the switching signal generated when the modulation signal generator 16 half the dwell time has elapsed, and performs a switching operation, and the transmitter 15 receives the switching signal from the modulation signal generator 16 in the first half of the dwell time. The transmission signal modulated by the long-pulse frequency modulation signal and the latter half-pulse amplitude modulation (frequency is unmodulated) signal is supplied to the antenna 1. The comparator 9 generates a high-speed target detection signal when the distance difference between the two is greater than or equal to the distance (preset value) corresponding to the desired approach speed. The value set in advance here is calculated in advance by a known arithmetic expression of the following "Equation 1" of the target Doppler frequency (corresponding to the target approach speed) at the time of pulse compression and the distance displacement amount caused thereby. It can be calculated and set.

[0016]

[Equation 1]

Here, DR is the approach speed, ΔR is the distance shift amount, C is the speed of light, T is the transmission pulse width (long pulse width), τ is the pulse width after pulse compression, and λ is the wavelength.

The state of the timing of the transmitted wave at this time is shown in FIG.
Shown in. FIG. 4 shows that the first half of the dwell time is spent for transmitting long pulses and the second half is spent for transmitting short pulses. FIG. 5 shows how the distance difference between the received signals of the long pulse and the short pulse occurs,
In FIG. 5, the position of the short pulse reception signal is the true target distance, and 17 in the figure shows the distance shift amount that occurred during pulse compression because it was subjected to Doppler frequency modulation from the target.

Example 2. FIG. 2 shows another embodiment of the present invention, in which 13 is a distance difference discriminator and 14 is a gate circuit.

In the second embodiment shown in FIG. 2, the target distance by the long pulse and the short pulse is input to the distance difference discriminator 13.
The distance difference discriminator 13 discriminates whether or not the distance difference between the two is within a preset distance range, and when it is within the distance range, a true signal is generated. Here, the preset distance range can be obtained by converting the desired approach speed range into the distance range using "Equation 1". The gate circuit 14 passes the target distance information only when the true signal from the distance difference discriminator 13 is present, and inputs it to the computer 12. Therefore, only the target in the desired approach speed range can be detected.

Example 3. FIG. 3 shows still another embodiment of the present invention, in which 10 is a distance difference calculator and 11 is an approach speed calculator.

In the third embodiment shown in FIG. 3, the distance difference calculator 10 subtracts the target distance by the short pulse from the target distance by the long pulse in the target distance by the long pulse and the short pulse, and the result is calculated by the approach speed calculator. Enter in 11. The approaching speed calculator 11 calculates the target approaching speed from this distance difference by using "Equation 1" and inputs it to the calculator 12. Since the computer 12 obtains the target approach speed at the same time as the target detection, this is used as the initial speed value in the tracking calculation.

[0023]

Since the present invention is constructed as described above, it has the following effects.

By simultaneously using a long pulse and a short pulse within the dwell time and comparing each distance difference with a preset distance value, at the same time when the target is detected, the magnitude of the desired approach speed of the target is determined. it can.

Further, it is determined whether or not the distance difference between the long pulse and the short pulse is within a preset distance range, and only when the difference is within the range, the target distance is input to the computer to obtain a desired approach speed range. Only targets within can be detected.

Further, the distance difference between the long pulse and the short pulse is calculated, the approach speed is calculated using the calculated distance difference, and the calculated approach speed is input to the computer and set as the speed initial value for the tracking calculation. The time can be greatly reduced. (The convergence time of the tracking calculation depends on the accuracy of the input value, and it is difficult to express the shortening effect uniquely, but generally speaking, if the velocity initial value is given, the convergence time will be reduced to half. The following shortening effect can also be expected.)

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a timing diagram illustrating the method of the present invention.

FIG. 5 is a diagram for explaining a state of distance shift due to Doppler frequency modulation used by the present invention.

FIG. 6 is a block diagram showing a conventional radar device.

[Explanation of symbols]

 4 Switch Circuit 8 Range Finder 9 Comparator 10 Distance Difference Calculator 11 Approaching Speed Calculator 13 Distance Difference Discriminator 14 Gate Circuit 15 Transmitter 16 Modulation Signal Generator

Claims (3)

[Claims] 1. A transmission means for transmitting both a frequency-modulated transmission wave for pulse compression and an unmodulated transmission wave within the dwell time of a radar, and a target for the frequency-modulated transmission wave. The received signal from the target is input via the pulse compressor and the video integrator, and the first rangefinder for calculating the target distance and the received signal from the target for the unmodulated transmission wave are input via the video amplifier. , A second distance measuring device for calculating a target distance and the outputs of the first and second distance measuring devices are inputted, and a high-speed target signal is generated when a distance difference between them is equal to or more than a preset value. And a calculator for inputting the output of the comparator and the output of the second rangefinder to perform target tracking calculation. 2. A transmission means for transmitting both a frequency-modulated transmission wave for pulse compression and an unmodulated transmission wave within the dwell time of the radar, and a target for the frequency-modulated transmission wave. The received signal from the target is input via the pulse compressor and the video integrator, and the first rangefinder for calculating the target distance and the received signal from the target for the unmodulated transmission wave are input via the video amplifier. Inputting the outputs of the second distance measuring device for calculating the target distance and the first and second distance measuring devices, it is determined whether or not the distance difference between the two is within a preset distance range, and the setting is made. Distance difference discriminator that generates a true signal when within the specified distance range, a gate circuit that allows the output of the second range finder to pass by the true signal, and an output of this gate circuit as input, and target tracking calculation A radar apparatus comprising: 3. A transmission means for transmitting both a frequency-modulated transmission wave for pulse compression and an unmodulated transmission wave within a dwell time of a radar, and a target for the frequency-modulated transmission wave. The received signal from the target is input via the pulse compressor and the video integrator, and the first rangefinder for calculating the target distance and the received signal from the target for the unmodulated transmission wave are input via the video amplifier. , A second distance measuring device for calculating a target distance, and a distance difference calculating device for inputting outputs of the first and second distance measuring devices to calculate a distance difference between the two, and a target approach speed from the distance difference. And a calculator that performs target tracking calculation with the target distance calculated by the second range finder and the target approach speed calculated by the approach speed calculator as initial velocity values. Radar equipment.