JP5399056B2 - Target detection device - Google Patents

Description

  The present invention relates to a target detection device that detects a target such as a land or a building.

  As an apparatus for detecting a target, for example, there is a radar apparatus that transmits a radio wave of a microwave band, receives a reflected wave thereof, and measures a distance and an azimuth from the current position to the target. When using a radar apparatus to detect a target at a long distance with high distance resolution, it is necessary to increase the peak transmission power and emit a narrow pulse signal to space.

  By the way, in recent years, from the viewpoint of effective utilization of radio wave resources, attention has been focused on solid-state radar devices using semiconductor amplifiers that have less unnecessary radiation than electron tubes such as magnetrons and klystrons. However, since the solid-state radar device has a lower transmission power than a radar device using an electron tube, there is a problem that sensitivity to a distant target is lowered.

  In order to solve this problem, by emitting a radio wave of a long pulse signal (hereinafter referred to as “long pulse signal”) subjected to predetermined modulation, and receiving a reflected wave from a target and performing a pulse compression process An apparatus that can detect a distant target with high distance resolution (hereinafter referred to as “pulse compression radar apparatus”) is known (for example, see Non-Patent Document 1).

  However, in a conventional pulse compression radar apparatus, a reception failure may occur in a facility that receives broadcast waves, communication waves, or the like (hereinafter referred to as “radio wave receiving facility”) due to the emission of a long pulse signal. For example, when a long pulse signal emitted by this radar device is located in the image band of a receiver that employs the superheterodyne method, a wide pulse emission unique to the pulse compression radar device causes the electron tube such as magnetron or klystron to be used. Radio waves may be radiated for a longer period of time, and interference may become apparent.

  Therefore, as a countermeasure, for example, when a conventional pulse compression radar device is applied to a land-based weather radar, transmission of a long pulse signal is stopped in the direction of azimuth and elevation where it is assumed that a reception failure may occur. Therefore, a process of providing a sector blank has been performed.

Further, for example, when a conventional pulse compression radar apparatus is mounted on a ship, processing for providing an azimuth blank as shown in FIG. 8 is performed. FIG. 8 shows an anchored ship 1 equipped with a pulse compression radar device, a land 2, a radio wave launchable region 3 indicating a region where a long pulse signal can be emitted, and a region where the emission of a long pulse signal is restricted. A radio wave emission restriction area 4 shown in FIG. The pulse compression radar apparatus mounted on the ship 1 emits a long pulse signal toward the radio wave emission possible region 3 and does not emit a long pulse signal in the direction of the land 2 that is assumed to cause a reception failure. A launch area is set to avoid a reception failure on the land 2.
Supervised by Takashi Yoshida, “Revised Radar Technology”, The Institute of Telecommunications, May 25, 1999, p275-280

  However, in the conventional pulse compression radar apparatus, it is necessary to set the azimuth and the elevation angle where the radio wave transmission restriction is provided in accordance with the relationship between the area where the radio wave receiving facility is expected to exist and the position of the radar apparatus. Therefore, when a conventional pulse compression radar device is installed on a ship navigating near the beach or a moving object that is moving in a densely populated area for urban heavy rain observation, the radio wave emission restriction area should always be set optimally. It was difficult. Therefore, the conventional pulse compression radar apparatus has a problem that it is difficult to avoid a reception failure due to a long pulse signal.

  The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a target detection apparatus that can avoid a reception failure due to a long pulse signal.

In the target detection apparatus of the present invention, the first identification means transmits a short pulse signal, and the first signal generated by the reflection of the short pulse signal at the target is received from the time when the short pulse signal is transmitted. The time to the time is identified as the distance from the target. The second identification means transmits a long pulse signal having a longer pulse width than the short pulse signal after the short pulse signal, and compresses the pulse width of the second signal generated by reflection of the long pulse signal at the target. To identify the target. Further, the second identification means sets the transmission power of the long pulse signal to a smaller value as the time from the time when the short pulse signal is transmitted to the time when the first signal is received is shorter , Based on the target received specification data for the long pulse signal arriving at the target and the transmission specification data that the second identifying means has for the second signal, the transmission power of the long pulse signal is obtained, and the long pulse is obtained. Changing the beam direction of the antenna used for signal transmission and second signal reception, and setting transmission specification data based on the relative distance of each region irradiated with the long pulse signal via the beam It is.

  With this configuration, in the target detection device of the present invention, the transmission power of the long pulse signal used for target identification is set to a smaller value as the distance from the target is shorter. Therefore, compared to the case where the transmission power is not changed regardless of the distance to the target, interference / disturbance to the target due to the power of the incoming long pulse signal being too large. Obstacles are alleviated or avoided.

In addition, with this configuration, in the target detection device of the present invention, the long pulse signal reaches the target (irradiated) from the second identification unit, and on the contrary, the second signal is second from the target. The transmission power of the long pulse signal is set in consideration of the characteristics of the return path reaching the identification means. Accordingly, obstacles such as interference and interference with the above-described target can be mitigated or avoided with higher accuracy.

In addition, with this configuration, in the target detection device of the present invention, the characteristics of the forward and return propagation paths described above are taken into account for each region even when the region irradiated with the long pulse signal changes. The transmission power of the long pulse signal is set. Therefore, even when targets to be identified using long pulse signals are located in different directions or distributed, obstacles such as interference and interference with these targets are more accurately mitigated or avoided. The

Furthermore, in the target detection device of the present invention, in the target detection device according to claim 1 , the range complementing means is a range closer to and farther from the target by a combination of the first signal and the second signal. And cover.

  With this configuration, in the target detection apparatus of the present invention, the range below the pulse width of the long pulse signal on the A scope is reflected by the short pulse reflected by the reflector (including the distribution target) located within that range. Complementation is based on the resulting signal. Therefore, it is possible to relax the constraints related to positioning and range width.

In the target detection device of the present invention, in the target detection device according to claim 1 or 2 , the long pulse signal is any one of radio waves, sound waves, and light that have been subjected to the processing that enables the compression. It corresponds to.

  With this configuration, the target detection apparatus of the present invention can perform positioning and distance measurement by applying a pulse compression technique to a wave signal suitable for various targets and fields.

  According to the target detection apparatus of the present invention, obstacles such as interference and interference with the target due to the excessively high power of the long pulse signal are alleviated or avoided.

  According to the target detection apparatus of the present invention, even if the targets to be identified using the long pulse signal are located in different directions or distributed, there are obstacles such as interference and interference with these targets. It is mitigated or avoided more accurately.

  According to the target detection device of the present invention, the restrictions on positioning and range widths are eased.

  The target detection device according to the present invention enables positioning and distance measurement by applying a pulse compression technique to a wave signal suitable for various targets and fields.

  Therefore, according to the present invention, positioning and distance measurement related to a desired target can be accurately and flexibly realized without significantly changing the hardware configuration as compared with the conventional example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The target detection device according to the present invention will be described with reference to an example in which the target detection device is applied to a radar device mounted on a ship and using microwave waves.

  First, the configuration of an embodiment of a radar apparatus according to the present invention will be described.

  As shown in FIG. 1, the radar apparatus 10 according to the present embodiment includes a transmission timing instruction unit 11, a near pulse signal generation unit 12, a long pulse signal generation unit 13, a transmission unit 14, and an antenna unit 15. The radar apparatus 10 includes a receiving unit 16, a target detecting unit 17, an electric field intensity calculating unit 18, a specification data holding unit 19, a threshold data holding unit 20, a determination unit 21, and a long pulse signal instruction unit 22.

  The transmission timing instruction unit 11 generates a transmission trigger signal for instructing the timing of transmitting a near pulse signal and a long pulse signal, which will be described later, based on a predetermined pulse repetition interval (PRI), and generates a near pulse signal It outputs to the part 12 and the long pulse signal generation part 13, respectively.

  The near pulse signal generation unit 12 receives a transmission trigger signal from the transmission timing instruction unit 11 and generates a near pulse signal based on the transmission trigger signal. This near pulse signal is emitted to complement the period during which the signal cannot be received due to the sneak signal during the emission period of the long pulse signal. The signal incapable period is calculated as follows according to the long pulse signal width and the speed of light.

[Equation 1]
No signal reception period = (light speed x long pulse signal width) / 2

  For example, when a long pulse signal of 50 μs is emitted, the near pulse signal is a short-distance observation pulse for detecting a target existing in a region up to a radius of 7.5 km centered on the position of the ship on which the radar apparatus 10 is mounted. Signal. The near pulse signal is an unmodulated pulse signal having a maximum pulse width of about 4 μs, for example. Here, the target refers to land, its coastline, land or sea structure, and the like. In the following description, when the radar apparatus 10 detects a target, it is assumed that there is a radio wave receiving facility near the detected target. The near pulse signal generator 12 constitutes a first identification unit according to the present invention.

  The long pulse signal generation unit 13 receives a transmission trigger signal from the transmission timing instruction unit 11 and generates a long pulse signal based on the transmission trigger signal. This long pulse signal is a pulse signal that can detect a target that exists beyond the signal unreceivable period determined by Equation 1, centered on the position of the ship on which the radar apparatus 10 is mounted. This long pulse signal includes, for example, a signal component having a pulse width of about 20 μs to 50 μs and modulated by a predetermined modulation method. Examples of the modulation method include a chirp modulation method and a phase modulation method. The long pulse signal generator 13 constitutes a second identification unit according to the present invention.

  Here, the transmission trigger signal, the near pulse signal, and the long pulse signal will be described with reference to FIG. FIG. 2 is a timing chart conceptually showing the positional relationship of each signal on the time axis.

  First, as shown in the upper part of FIG. 2, the transmission trigger signal is generated by the transmission timing instruction unit 11 based on the PRI. As shown in the middle part of FIG. 2, the near pulse signal and the long pulse signal are generated by the near pulse signal generation unit 12 and the long pulse signal generation unit 13, respectively, based on the transmission trigger signal. That is, one near pulse signal and one long pulse signal are generated for each PRI. The time interval between the near pulse signal and the long pulse signal is, for example, a time interval corresponding to the pulse width of the long pulse signal.

  Next, the lower part of FIG. 2 shows the detection output in the receiving unit 16. From the left side of FIG. 2, the waveform of the reflected wave signal reflected by the near pulse signal at the target and the emission period of the long pulse signal are shown. A period (blind range) in which the signal cannot be received due to the sneak signal (main bang) and a waveform of the reflected wave signal in which the long pulse signal is reflected by the target are shown. As a known technique, a method of complementing the blind range using a reflected wave signal by a near pulse signal is known. In the present embodiment, the receiving unit 16 supplements the blind range.

  Returning to FIG. 1, the transmission unit 14 inputs the near pulse signal generated by the near pulse signal generation unit 12 and the long pulse signal generated by the long pulse signal generation unit 13, and emits the near pulse signal and the long pulse signal into space. The frequency is converted into a frequency, power amplification is performed, and the result is output to the antenna unit 15.

  The antenna unit 15 has an antenna 15a that emits radio waves and receives reflected waves with respect to an area of 360 degrees around the ship, and a drive that sets the scanning area of the antenna 15a by changing the azimuth angle of the antenna 15a. Unit 15b, and the transmitter 14 sequentially emits a radio wave based on a near pulse signal subjected to frequency conversion and power amplification and a radio wave based on a long pulse signal. The antenna unit 15 receives a reflected wave signal obtained by reflecting each radio wave by the near pulse signal and the long pulse signal at the target, and outputs the reflected wave signal to the receiving unit 16. In the present embodiment, the drive unit 15b is described as being capable of changing only the azimuth angle of the antenna 15a. However, the drive unit 15b is capable of changing at least one of the azimuth angle and the elevation angle of the antenna 15a. Also good.

  The reception unit 16 performs power pressure processing, detection, and long pulse signal processing on the reflected wave signal from the antenna unit 15 and outputs the detected reflected wave signal to the target detection unit 17. ing. Further, as described above, the receiving unit 16 supplements the blind range using the reflected wave signal based on the near pulse signal. The receiving unit 16 constitutes range complementing means according to the present invention.

  The target detection unit 17 detects the target land or building based on the reflected wave signal after detection. Further, when the target is not detected, the target detection unit 17 outputs a signal indicating that to the long pulse signal instruction unit 22, and when the target is detected, obtains the distance from the radar device 10 to the target, and obtains the obtained distance. A signal including information is output to the electric field intensity calculation unit 18. As a method for detecting land, buildings, etc., for example, the monotonic decrease rule of the cell average value shown in FIG. 2 of JP-A-2003-227871 can be used. The target detection unit 17 constitutes a first identification unit and a second identification unit according to the present invention.

  The electric field strength calculation unit 18 calculates the electric field strength of the pulse signal wave by the long pulse signal in the radio wave reception facility that is assumed to exist in the vicinity of the detected target based on the distance obtained by the target detection unit 17. . This electric field strength can be calculated by, for example, calculating the received power in the radio wave receiving facility that is separated from the radar apparatus 10 by the distance r by Equation 2.

[Equation 2]

The explanation of each variable is shown below.
Pr: Received power at a position r away from the radar apparatus 10 (= square of electric field strength)
Pt: Peak transmission power of long pulse signal [W]
τ: Modulation pulse width of long pulse signal [sec]
Gt: antenna gain [times] of long pulse signal
Gr: Received antenna gain of radio wave reception equipment [times]
Grec: receiver gain of radio wave reception equipment with respect to transmission wavelength of long pulse signal [times]
Ae: Opening area of reception antenna of radio wave reception facility [m ² ]
λ: long pulse signal transmission wavelength [m]
Among the variables on the right side of Equation 1, Pt, τ, Gt, and λ are variables related to transmission in the radar apparatus 10 and are hereinafter referred to as “transmission specifications”. Of the variables on the right side of Equation 1, Gr, Grec, and Ae are variables related to reception at the radio wave reception facility, and are hereinafter referred to as “reception specifications”.

  The specification data holding unit 19 holds the transmission specification and reception specification data shown in Equation 2 and is read out by the electric field strength calculation unit 18. Here, the transmission specification data is self-evident because it is determined when the radar apparatus 10 is operated. On the other hand, the data of the receiving specifications differ depending on the radio wave receiving equipment that is the target of avoiding reception disturbances. However, the receivers provided in each radio wave receiving equipment conform to the standards proposed by the standards bodies related to broadcast waves and communication waves. Since it is designed on the basis of this, it is possible to determine the data of the receiving specifications with reference to the standard. It is also possible to determine the data of the receiving specifications by conducting an experiment in advance.

  The threshold data holding unit 20 holds data on the electric field strength threshold for determining whether or not a reception failure occurs in a radio wave reception facility that is a target for avoiding reception failures. This electric field strength threshold is a value determined based on the desired signal reception power expected by the receiver in the radio wave reception facility that is a target for avoiding reception interference. For example, the threshold data holding unit 20 holds a value twice the desired signal received power of the receiver as a field strength threshold. The desired signal received power of the receiver is determined by referring to a standard proposed by a standards body regarding broadcast waves, communication waves, etc., or by conducting an experiment in advance.

  Further, the electric field strength threshold data held by the threshold data holding unit 20 will be described with reference to FIG. In FIG. 3, the horizontal axis indicates the distance from the radar apparatus 10 to the target, and the vertical axis indicates the electric field strength at the target position.

  As shown in FIG. 3, the electric field strength of the long pulse signal wave emitted by the radar apparatus 10 is inversely proportional to the square of the distance, and the electric field strength increases as the peak transmission power increases. Whether or not there is a possibility that a reception failure may occur in the radio wave reception facility due to the distance obtained by the target detection unit 17 and the electric field strength in the radio wave reception facility calculated by the electric field intensity calculation unit 18 by determining the intensity threshold Can be determined.

  Returning to FIG. 1, the determination unit 21 is based on the distance obtained by the target detection unit 17, the electric field strength in the radio wave reception facility calculated by the electric field strength calculation unit 18, and the electric field strength threshold held by the threshold data holding unit 20. Thus, the magnitude of the electric field strength in the radio wave receiving facility with respect to the electric field strength threshold is determined, and a signal indicating the determination result is output to the long pulse signal instruction unit 22. In addition, when the target detection unit 17 detects a target, the determination unit 21 outputs a signal indicating the electric field strength for each target to the long pulse signal instruction unit 22.

  The long pulse signal instructing unit 22 sets the data value of the transmission specification related to the long pulse signal based on the transmission specification and reception specification data held by the specification data holding unit 19 and the determination result of the determination unit 21. The pulse signal generator 13 is instructed. In addition, the long pulse signal instruction | indication part 22 comprises the 2nd identification means which concerns on this invention. Hereinafter, the processing of the long pulse signal instruction unit 22 will be described in detail with reference to FIG.

  FIG. 4 shows a state in which a reflected wave from the target is obtained by the near pulse signal generated based on the transmission trigger signal. As described above, by receiving this reflected wave, information on whether or not there is a target such as a land or a building, the distance from the radar apparatus 10 to the target, and the electric field strength in the radio wave receiving facility near the target are obtained and determined. The unit 21 reads out the electric field strength threshold from the threshold data holding unit 20 (see FIG. 1).

  Then, the long pulse signal instruction unit 22 outputs the long pulse signal with the maximum power to an area where there is no land or a building, or an area where there is a land or a structure but there is no reception failure. The long pulse signal generator 13 is instructed to transmit.

  In addition, the long pulse signal instruction unit 22 applies a long pulse to the region that is estimated to have a reception failure according to the difference between the electric field strength in the radio wave reception facility and the electric field strength threshold. The long pulse signal generation unit 13 is instructed to perform any one of processing for reducing the amplitude of the signal, processing for shortening the pulse width, and processing for stopping transmission of the long pulse signal. The long pulse signal generation unit 13 generates a long pulse signal based on this instruction.

  Next, the operation of the radar apparatus 10 in this embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing operations from the generation of the near pulse signal to the reception of the reflected wave by the long pulse signal in the radar apparatus 10.

  The near pulse signal generation unit 12 generates a near pulse signal based on the transmission trigger signal output from the transmission timing instruction unit 11 (step S11) and outputs the near pulse signal to the transmission unit 14.

  The transmission unit 14 converts the frequency of the input near pulse signal to a frequency to be emitted into space, performs power amplification (step S12), and outputs the amplified signal to the antenna unit 15.

  The antenna unit 15 emits a radio wave of a near pulse signal (step S13) and receives a reflected wave from the target (step S14). Then, the antenna unit 15 outputs the reflected wave signal to the receiving unit 16.

  The receiving unit 16 frequency-converts the reflected wave signal to amplify the power (step S15), and outputs it to the target detecting unit 17.

  The target detection unit 17 determines whether there is a target such as a land or a building based on the reflected wave signal (step S16).

  In step S16, when the target detection unit 17 determines that there is no target, the target detection unit 17 outputs a signal indicating that to the long pulse signal instruction unit 22, and the long pulse signal instruction unit 22 maximizes the amplitude of the long pulse signal. The long pulse signal generator 13 is instructed to set the value (step S20).

  On the other hand, if it is determined in step S16 that the target is present, the target detection unit 17 calculates the distance from the radar apparatus 10 to the target based on the time from when the near pulse signal is transmitted until the reflected signal is received. (Step S <b> 17), a signal indicating the distance is output to the electric field intensity calculation unit 18.

  When the target detection unit 17 detects the target, the electric field strength calculation unit 18 reads the data of the transmission specifications from the specification data holding unit 19 and calculates the electric field strength in the radio wave reception facility near the detected target, for example, the number described above. 2 is calculated (step S18).

  The determination unit 21 reads out the electric field strength threshold data from the threshold data holding unit 20, reads the read electric field strength threshold, the distance obtained by the target detection unit 17, and the electric field strength in the radio wave reception facility calculated by the electric field strength calculation unit 18. Based on the threshold value, the amount of electric field strength in the radio wave receiving facility with respect to the electric field strength threshold is determined, and a signal indicating the determination result is output to the long pulse signal instruction unit 22 (step S19). The determination unit 21 outputs a signal indicating the electric field strength for each target to the long pulse signal instruction unit 22.

  The long pulse signal instructing unit 22 determines the difference between the electric field strength and the electric field strength threshold in the radio wave receiving facility based on the data of the transmission specifications and the data received by the specification data holding unit 19 and the determination result of the determination unit 21. Is output to the long pulse signal generation unit 13.

  First, for a region (condition 1) where it is estimated that reception failure does not occur even when the amplitude of the long pulse signal is set to the maximum value, the long pulse signal instruction unit 22 maximizes the long pulse signal in step S20. The long pulse signal generation unit 13 is instructed to transmit with power.

  In addition, a reception failure may occur if the amplitude of the long pulse signal is set to the maximum value, but a region where the reception failure can be avoided by reducing the amplitude of the long pulse signal (or shortening the pulse width) In response to 2), the long pulse signal instruction unit 22 instructs the long pulse signal generation unit 13 to reduce the amplitude (or shorten the pulse width) of the long pulse signal according to the distance (step S21).

  Further, the long pulse signal instructing unit 22 transmits the long pulse signal for a region (condition 3) where the reception failure cannot be avoided even if the amplitude of the long pulse signal is reduced (or the pulse width is shortened). The long pulse signal generator 13 is instructed to stop (in other words, generate a long pulse signal with an amplitude value of zero) (step S22).

  Thereafter, although the illustration is simplified, the long pulse signal generation unit 13 sets the amplitude (or pulse width) of the long pulse signal based on the instruction of the long pulse signal instruction unit 22, and the transmission unit 14 The frequency of the pulse signal is converted to a frequency to be emitted into space, power amplification is performed, and the antenna unit 15 receives a reflected wave after emitting a radio wave of a long pulse signal (step S23). The receiving unit 16 performs power amplification, detection and detection of the reflected wave signal from the antenna unit 15 and pulse compression processing for the long pulse signal and complementary processing for the blind range during the transmission period of the long pulse signal.

  The operation of the radar apparatus 10 described above will be specifically described with reference to FIG. FIG. 6 shows a state where the ship 31 on which the radar apparatus 10 is mounted is navigating in the direction indicated by the dotted arrow near the coast of the land 32. It is assumed that a near pulse signal wave is emitted from the radar device 10 of the ship 31 toward a region in a direction of 360 degrees.

  The target detection unit 17 detects the sea area 41 and the areas 42 to 43 including the land by the reflected wave by the near pulse signal wave emitted by the radar apparatus 10. In addition, the target detection unit 17 obtains the distance from each coast line to the radar apparatus 10 in the regions 42 to 43 including the land. As a result, the target detection unit 17 can grasp that each coast line is distant in the order of the regions 44, 42, and 43 with the position of the radar device 10 as a reference. The electric field strength calculation unit 18 calculates the electric field strength at each distance from the regions 42 to 44 to the radar device 10. The determination unit 21 determines the amount of electric field strength in the radio wave reception facility with respect to the electric field strength threshold. The long pulse signal instruction unit 22 determines whether or not a reception failure occurs in the radio wave reception facility in each area.

  As a result, if the region 44 is a region in which the reception failure cannot be avoided even if the amplitude of the long pulse signal is reduced, the long pulse signal instruction unit 22 transmits the long pulse signal wave to the region 44. The long pulse signal generator 13 is instructed to stop firing.

  In addition, it is assumed that the regions 42 and 43 are regions where reception failure occurs when the amplitude of the long pulse signal is set to the maximum value, but reception failure can be avoided if the amplitude of the long pulse signal is reduced. The long pulse signal instructing unit 22 instructs the data of the amplitude value of the long pulse signal that can avoid the reception failure to the areas 42 and 43, respectively.

  Specifically, the long pulse signal instruction unit 22 instructs the long pulse signal generation unit 13 to set the amplitude of the long pulse signal to, for example, ¼ of the maximum value for the region 42. In addition, the long pulse signal instruction unit 22 instructs the long pulse signal generation unit 13 to set the amplitude of the long pulse signal to, for example, ½ of the maximum value for the region 43. In other words, the radar apparatus 10 mounted on the ship 31 can dynamically set the amplitude of the long pulse signal and dynamically avoid reception failures.

  As described above, according to the radar apparatus 10 of the present embodiment, according to the distance obtained by the near pulse signal, the transmission specifications of the long pulse signal so that the received electric field strength in the region where the long pulse signal is received is equal to or less than the threshold value. Since the configuration is provided with the long pulse signal instruction unit 22 for setting data, it is possible to avoid a reception failure due to a long pulse signal wave.

  Next, another aspect of the present embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating a configuration of the long pulse signal generation unit 50 obtained by changing the configuration of the long pulse signal generation unit 13 in the above-described embodiment. Other configurations are the same as those in FIG.

  As illustrated in FIG. 7A, the long pulse signal generation unit 50 includes long pulse signal generators 51 to 54, a long pulse signal selection unit 55, and a D / A conversion unit 56.

  The long pulse signal generators 51 to 54 generate long pulse signals having different amplitudes based on the transmission trigger signal.

  Specifically, each of the long pulse signal generators 51 to 54 holds table data for generating a long pulse signal, and generates a long pulse signal composed of a digital signal based on the transmission trigger signal. It is. In the example shown in FIG. 7, the long pulse signal generators 51 to 54 generate long pulse signals having maximum amplitude, 1/2 of maximum amplitude, 1/4 of maximum amplitude, and zero amplitude, respectively.

  The long pulse signal selection unit 55 selects any one of the long pulse signal generators 51 to 54 based on an instruction from the long pulse signal instruction unit 22.

  The D / A converter 56 converts the long pulse signal, which is one of the outputs of the long pulse signal generators 51 to 54 selected by the long pulse signal selector 55, into an analog signal, and transmits the transmitter 14 (not shown). To output.

  With this configuration, the long pulse signal generation unit 50 can easily generate a long pulse signal based on an instruction from the long pulse signal instruction unit 22.

  In the above description, the example in which the reception failure is avoided by reducing the amplitude of the long pulse signal has been described. However, the present invention is not limited to this, and for example, as shown in FIG. As shown as width reduction A, a long pulse signal may be composed of one shortened pulse signal equivalent to amplitude reduction.

  In the above-described embodiment, the processing for reducing the peak transmission power has been described by taking an example of performing the amplitude reduction or the pulse width reduction. However, the present invention is not limited to these, and the peak transmission is performed. A similar effect can be obtained if the process reduces power.

  In the above-described embodiment, the example in which the radar apparatus 10 is mounted on a ship has been described. However, the present invention is not limited to this. For example, the same effect can be obtained even when the radar apparatus 10 is mounted on a moving body such as a vehicle or an aircraft, or a weather radar that is fixedly installed.

  In the above-described embodiment, the radar apparatus 10 that uses microwave waves is described as an example. However, the present invention is not limited to this, and radio waves other than the microwave band or ultrasonic waves are not limited thereto. The same effect can be obtained even when applied to an apparatus for detecting a target using infrared rays, light, or the like.

  In the above-described embodiment, the radar apparatus 10 that uses microwave waves is described as an example. However, the present invention is not limited to this, and radio waves other than the microwave band or ultrasonic waves are not limited thereto. The same effect can be obtained even when applied to an apparatus for detecting a target using infrared rays, light, or the like.

  Further, in the above-described embodiment, chirp modulation for realizing pulse compression of a long pulse signal is performed based on a code sequence having “steep autocorrelation characteristics” such as a PN code or a GOLD code. May be substituted.

  In the above-described embodiment, the process for obtaining the distance to the target based on the time from when the near pulse signal is transmitted to when the reflected signal is received may not be performed based on arithmetic operations such as conversion, For example, it may be replaced by a process of identifying the time as “distance to the target”.

  Furthermore, in the above-described embodiment, the target may be a distributed target such as a cloud, fog, or wave.

  Further, in the above-described embodiment, the target that is subject to reception failure by the long pulse signal wave is not limited to the radio wave reception facility, for example, the performance deteriorates due to interference or interference caused by the incoming long pulse signal, or malfunctions. It may be a device that may cause other failures.

  As described above, in the target detection apparatus according to the present invention, the interference such as interference and interference with the target described above due to the long pulse signal is mitigated or avoided with higher accuracy. Therefore, it is useful as a target detection device.

The block diagram which shows the structure of the radar apparatus in one Embodiment of this invention. 1 is a timing chart conceptually showing the positional relationship of a transmission trigger signal, a near pulse signal, and a long pulse signal on a time axis in a radar apparatus according to an embodiment of the present invention. Explanatory drawing of the electric field strength threshold value which a threshold value data holding part holds in the radar apparatus according to an embodiment of the present invention. The figure which shows an example of a process of the long pulse signal instruction | indication part in the radar apparatus in one Embodiment of this invention. The flowchart which shows operation | movement of the radar apparatus in one Embodiment of this invention. Explanatory drawing of the operation | movement during the navigation of the ship carrying the radar apparatus in one Embodiment of this invention The figure which shows another aspect in the radar apparatus in one Embodiment of this invention. Explanatory drawing of the process which provides an azimuth blank in the conventional radar apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radar apparatus 11 Transmission timing instruction | indication part 12 Near pulse signal generation part 13 Long pulse signal generation part 14 Transmission part 15 Antenna part 15a Antenna 15b Drive part 16 Reception part 17 Target detection part 18 Electric field strength calculation part 19 Specification data holding part 20 Threshold value Data holding unit 21 Determination unit 22 Long pulse signal instruction unit 31 Ship 32 Land 41 to 44 area 50 Long pulse signal generation unit 51 to 54 Long pulse signal generator 55 Long pulse signal selection unit 56 D / A conversion unit

Claims (3)

A first pulse that transmits a short pulse signal and identifies the time from the time when the short pulse signal is transmitted to the time when the first signal generated by the reflection of the short pulse signal at the target is received is identified as a distance from the target. And a long pulse signal having a longer pulse width than the short pulse signal is transmitted after the short pulse signal, and the pulse width of the second signal generated by the reflection of the long pulse signal at the target is compressed. In the target detection apparatus including the second identification unit that identifies the target,
The second identification means includes
The shorter the time from when the short pulse signal is transmitted to the time when the first signal is received, the transmission power of the long pulse signal is set to a small value ,
The transmission of the long pulse signal based on the target reception specification data for the long pulse signal arriving at the target and the transmission specification data that the second identification means has for the second signal. Seeking power,
The direction of a beam of an antenna used for transmission of the long pulse signal and reception of the second signal is varied, and the transmission is performed based on a relative distance for each region irradiated with the long pulse signal via the beam. A target detecting apparatus for setting specification data . The target detection apparatus according to claim 1 , further comprising range complementing means that covers a range closer to and farther from the target by a combination of the first signal and the second signal. Target detection device. 3. The target detection apparatus according to claim 1, wherein the long pulse signal is any one of radio waves, sound waves, and light that have been subjected to the processing that enables the compression. Detection device.