JP3858097B2 - Target detection device - Google Patents

Description

  The present invention relates to a target detection apparatus that transmits a transmission wave toward a target and detects the target based on a Doppler frequency of a reflected wave based on the transmission wave obtained from the target, and is particularly relatively slow. It is related with the target detection apparatus suitable for the detection of the target to fly by.

As one of target detection devices that capture a target at a separated position, there is a Doppler radar using a microwave Doppler shift. Such a target detection device transmits a microwave (transmission wave) toward a target and detects a Doppler frequency of a reflected wave generated due to a relative speed between the target detection device and the target, thereby detecting the target. Detect objects. For example, the following known publications disclose details of the Doppler radar.
Electronic Communication Series "Radar Technology": Published by IEICE

  By the way, since the Doppler frequency depends on the flying speed of an object (reflector) that reflects a transmission wave, it is difficult to detect a target flying at a relatively low speed. In other words, the Doppler frequency of a target flying at low speed is close to the frequency of sea clutter (sea surface scattered waves) in the sea area where this target flies. Cannot be identified.

  The present invention has been made in view of the above technical problem, and an object of the present invention is to provide a target detection apparatus that can more accurately detect a target flying at a relatively low speed.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, according to the present invention, as a first means, a high-speed flying object is equipped, a transmission wave is transmitted toward a target, and a reflected wave by the transmission wave obtained from the target is transmitted. In a target detection apparatus for detecting the target based on a Doppler frequency,
When the level of the scattered wave based on the transmission wave acquired after the high-speed flying object starts flying is below a predetermined extended determination threshold value, the detection range of the Doppler frequency is extended to the low frequency side and the target Comprising signal processing means for detecting an object ,
The signal processing means obtains frequency data composed of a frequency component included in the detection signal for detecting the Doppler frequency and the power of the frequency component in time series,
The power of the specific frequency data in which the frequency component is included in the scattered wave region on the low frequency side is the level of the scattered wave, and the level of the scattered wave immediately after the start of flight is the reference level. A configuration is adopted in which the detection range of the Doppler frequency is expanded to the low frequency side when the level becomes lower than the reference level and below the expansion determination threshold value .

Further, as a second means, in the first means, the signal processing means extends the Doppler frequency detection range to the low frequency side when the level of the scattered wave is equal to or lower than the equipment noise level. adopt.

According to the present invention, a target that is mounted on a high-speed flying object, transmits a transmission wave toward a target, and detects the target based on a Doppler frequency of a reflected wave from the transmission wave obtained from the target. In the detection device, when the level of the scattered wave based on the transmission wave acquired after the flying of the flying object falls below a predetermined extended determination threshold value, the detection range of the Doppler frequency is extended to the low frequency side. Since the signal processing means for detecting the target is provided, the target flying at a relatively low speed can be detected more accurately.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a target detection device will be described below with reference to the drawings as the best mode for carrying out the invention.

FIG. 1 is a block diagram showing a functional configuration of a target detection apparatus according to an embodiment of the present invention. In this figure, symbol W is a target, 1 is an antenna, 2 is a high frequency circuit, 3 is a signal processing circuit (signal processing means), 4 is a changeover switch, 5 is a constant voltage circuit, and 6 is a power source. The target W is a target for position acquisition, and is a high-speed flying object such as an aircraft. In addition, the target detection device according to the present embodiment is mounted (mounted) on a high-speed flying object that is launched from the ground (including not only on land but also on the sea) and fly toward the target. The position of the target W that is also flying is captured.

  The antenna 1 transmits a transmission signal having a frequency F supplied from the high-frequency circuit 2 toward the target W as a microwave transmission wave, and receives a reflected wave generated by reflecting the transmission wave on the target W. The reflected signal is supplied to the high frequency circuit 2. The reflected wave (that is, the reflected signal) is a frequency (F + fd) obtained by shifting the frequency F of the transmitted wave by the Doppler frequency fd according to the change in the relative speed between the high-speed flying object and the target W.

  The high frequency circuit 2 supplies a transmission signal to the antenna 1, while detecting the Doppler frequency fd based on the reflected signal and the transmission signal supplied from the antenna 1 and supplies the detected signal to the signal processing circuit 3. The signal processing circuit 3 as the signal processing means detects the position of the target W based on the detection signal supplied from the high frequency circuit 2, thereby setting the trigger timing of the high-speed flying object equipped with the target detection device. Calculated and supplied as a trigger signal to the subsequent trigger device. The changeover switch 4 switches supply / non-supply of the trigger signal to the trigger device. The constant voltage circuit 5 converts the direct current (DC) power supplied from the power source 6 to a constant voltage and supplies it to the high frequency circuit 2 and the signal processing circuit 3. The power source 6 is a battery that supplies DC power to the constant voltage circuit 5.

  FIG. 2 is a block diagram showing a detailed functional configuration of the high-frequency circuit 2. As shown in this figure, the high frequency circuit 2 includes an oscillator 2a, an amplifier 2b, a power distributor 2c, a directional coupler 2d, and a mixer 2e.

  The oscillator 2a generates a transmission signal having a frequency F and supplies it to the amplifier 2b. The amplifier 2b amplifies the transmission signal to a predetermined amplitude and supplies the amplified signal to the power distributor 2c. The power distributor 2c distributes and supplies the transmission signal supplied from the amplifier 2b to the directional coupler 2d and the mixer 2e. The directional coupler 2d outputs the transmission signal supplied from the power distributor 2c to the antenna 1 in FIG. 1, and outputs the reflected signal of the frequency (F + fd) supplied from the antenna 1 to the mixer 2e. The mixer 2e multiplies the reflected signal input from the directional coupler 2d by the transmission signal input from the power distributor 2c, and outputs a detection signal of the Doppler frequency fd to the signal processing circuit 3.

  FIG. 3 is a block diagram showing a detailed functional configuration of the signal processing circuit 3. The signal processing circuit 3 includes an amplifier 3a, a BPF 3b, an A / D converter 3c, a reference voltage generator 3d, a DSP 3e, a ROM 3f, and a trigger signal generator 3g.

  The amplifier 3a amplifies the detection signal to a predetermined amplitude and supplies it to the BPF 3b. The BPF 3b is a band limiting filter that limits the detection signal supplied from the amplifier 3a to a predetermined frequency range and outputs the detection signal to the A / D converter 3c. The A / D converter 3c digitally converts the detection signal (analog signal) supplied from the BPF 3b based on the reference DC voltage supplied from the reference voltage generator 3d, and supplies it to the DSP 3e as detection data. The reference voltage generator 3d generates the reference DC voltage and supplies it to the A / D converter 3c.

  The DSP 3e is a digital signal processor that calculates the trigger timing by processing the detection data based on a program (target detection program) stored in the ROM 3f. The DSP 3e supplies the trigger timing as a processing result to the trigger signal generator 3g as an operation signal. The ROM 3f stores the target detection program in advance. The trigger signal generator 3g generates a trigger signal from the operation signal supplied from the DSP 3e, and supplies it to the subsequent trigger device.

  Next, the operation of the target detection apparatus configured as described above will be described in detail along the flowchart shown in FIG.

  When the target detection apparatus starts operation, the transmission wave is continuously radiated from the antenna 1 toward the target W, and the reflected wave generated by the reflection of the transmission wave on the target W is continuously generated by the antenna 1. Receive automatically. The reflected wave is supplied as a reflected signal from the antenna 1 to the high frequency circuit 2, converted into a detection signal by the high frequency circuit 2, and supplied to the signal processing circuit 3.

  In the signal processing circuit 3, the detection signal is amplified by the amplifier 3a and further band-limited by the BPF 3b. The detection signal is sequentially sampled at a predetermined sampling interval by the A / D converter 3c and converted into detection data that is a time-series digital signal. The DSP 3e sequentially acquires such detection data from the A / D converter 3c (step S1), and further performs an FFT operation for each of a plurality of detection data (detection data string) included in a predetermined time interval T (step S1). S2).

  That is, the DSP 3e, as a result of the FFT operation on the detection data sequence sequentially obtained from the A / D converter 3c, includes the frequency component included in the detection signal (analog signal) for a predetermined period corresponding to the detection data sequence and the frequency component. Frequency data D (i) including the power of the frequency component is sequentially calculated in time series. Here, “i” is a data number indicating the time series order of the frequency data D (i), and is a variable for specifying the time series frequency data D (i).

  Here, the frequency component indicates the Doppler frequency fd based on the relative speed between the target W and the target detection device (that is, the high-speed flying object on which the target detection device is mounted), while the power is the Doppler frequency fd. Shows the strength. In addition, it is a well-known matter that frequency data D (i) using frequency components and their power as attribute information can be obtained by performing an FFT operation on a detection data string that is a time-series signal.

  FIG. 5 is a characteristic diagram showing the time change of the Doppler frequency fd (that is, the frequency component) (in the figure, T: time interval). The Doppler frequency fd generated between the target W flying at a predetermined speed and the target detection device maintains a substantially constant frequency in a state where the distance between them is separated, but the distance between them is close. As the frequency goes down, the frequency is gradually lowered to zero at the moment each other passes. The DSP 3e calculates the Doppler frequency fd that gradually changes with the passage of time in this manner by performing an FFT operation on each detection data string.

  FIG. 6 is a frequency distribution diagram showing the frequency data D (i) with the frequency component (that is, the Doppler frequency fd) as the attribute information as the horizontal axis and the power as the vertical axis. As shown in FIG. 6, the frequency components of each frequency data D (i) are distributed in the frequency regions fl to f3.

  Of these frequency regions fl to f3, the frequency regions fl to f2 located on the low frequency side are the sea clutter (sea surface scattered wave) frequency component (sea clutter component) or a target that flies at a relatively low speed (low speed). A clutter region in which a low-speed target signal component based on a reflected wave from a target) is distributed. On the other hand, frequency regions f2 to f3 located on a high frequency side are targets (flights) flying at a standard speed (standard speed). This is a target detection area in which standard target signal components based on reflected waves from a standard target are distributed.

  Now, the frequency data D (i) having such a property is sequentially obtained in time series as a result of the FFT operation processing (step S2) of FIG. 4, but the DSP 3e detects each frequency data D (i) in the detection mode. It is determined whether or not to expand the target detection area by performing the setting process (step S3).

  FIG. 7 is a flowchart showing details of the detection mode setting process. In this detection mode setting process, the DSP 3e first sets the clutter level immediately after the start of flying of the high-speed flying object, that is, the power of the frequency data D (i) in which the frequency component is included in the clutter region to the reference clutter level ( Step S31). In a normal case, the clutter level immediately after the launch is the highest value because the altitude is low.

  After completing the setting of the reference clutter level, the DSP 3e sequentially measures the clutter level of the acquired frequency data D (i) (step S32), and each of the clutter levels is the noise level of the device (system noise level in FIG. 6). It is determined whether it is below (step S33). When this determination is “Yes”, the DSP 3e proceeds to (Step S4), regardless of whether or not the flying object is flying up, while in the case of “No”. Then, it is determined whether or not the clutter level is equal to or lower than the reference clutter level (step S34).

  When the determination in step S34 is “Yes”, the DSP 3e has a clutter level at which the target detection process (step S5) at the subsequent stage does not malfunction, that is, the clutter identification threshold (extended determination threshold) shown in FIG. It is determined whether or not (step S35). If this determination is “Yes”, the process proceeds to (step S4). On the other hand, if the determination in step S34 or step S35 is “No”, the DSP 3e shifts the process to the target detection process (step S5).

  That is, according to such a detection mode setting process (step S3), when the altitude of the high-speed flying object is sequentially increased, the clutter level is lowered to at least the clutter identification threshold value (expansion determination threshold value) ( When the clutter level falls below the clutter identification threshold value, it is determined that the flying object is flying up), and in step S4, the target detection area is expanded to the clutter area on the low frequency side, and the extended target detection area Is set. When the clutter level drops below the clutter identification threshold value (expansion determination threshold value) and the target detection area is expanded to the clutter area, the frequency data D (i) is The target signal component of the target W traveling at a low speed whose frequency component is included in the clutter region can be detected.

  If the clutter level does not fall below the reference clutter level or the clutter identification threshold (extended judgment threshold), that is, the altitude of the high-speed flying object on which the target detection device is mounted has not increased immediately after launch. In this case, or when the altitude of the high-speed flying object has increased but the clutter level has not decreased to the clutter discrimination threshold (expansion determination threshold), the target detection area is not expanded.

  And DSP3e will perform the detection process of the target W, if the process of the said step S3 or step S4 is complete | finished like FIG. 4 (step S5). That is, a signal having a power equal to or higher than the target detection threshold value in FIG. 6 is detected as a target, and the DSP 3e sets the target based on the frequency data D (i) including the frequency component in the target detection area (or the extended target detection area). The relative positional relationship with the object W is determined. Then, the trigger timing, that is, the timing at which the Doppler frequency fd becomes near zero as shown in FIG. 5 is calculated from this positional relationship (step S6).

  The DSP 3e further determines the trigger timing, that is, determines whether or not the current time has reached the trigger timing calculated in step S6 (step S7). If this determination is “Yes”, the trigger signal generator A trigger signal generation instruction is output to 3g (step S8). As a result, a trigger signal is output from the trigger signal generator 3g, and the high-speed flying object triggers.

  If the determination in step S7 is “No”, the DSP 3e returns the process to step S1 without outputting a trigger signal generation instruction to the trigger signal generator 3g, and acquires the next detection data string. The subsequent processing (steps S2 to S6) is repeated.

  According to this embodiment, when it is determined that the sea clutter component is sufficiently small, the target detection area is expanded to the clutter area, and the extended target detection area is set. In such a state in which the extended target detection area is set, the sea clutter component does not act as a disturbance in detecting the low speed target signal component, so that the low speed target can be detected more accurately than in the past.

  In the above embodiment, the low-speed target includes a training flying object set as a target in the case of flying training of a high-speed flying object, but the present invention is not limited to this. is not. The present invention can also be applied to the detection of low-speed targets other than the training flying object.

  Further, in the above-described embodiment, the case where the sea surface scattered wave (sea clutter) exists as an example of the ground scattered wave has been described. However, the present invention is applicable even under the condition where the ground scattered wave other than the sea surface scattered wave exists. .

  Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

It is a block diagram which shows the function structure of one Embodiment of the target detection apparatus which concerns on this invention. It is a block diagram which shows the detailed functional structure of the high frequency circuit in one embodiment of this invention. It is a block diagram which shows the detailed functional structure of the signal processing circuit in one embodiment of this invention. It is a flowchart which shows the process of the signal processing circuit in one embodiment of this invention. It is a characteristic view which shows the time change of the Doppler frequency fd in one embodiment of this invention. It is a frequency distribution figure of the Doppler frequency fd in one embodiment of the present invention. It is a flowchart which shows the detail of the detection mode setting process in one embodiment of this invention.

Explanation of symbols

W target 1 antenna 2 high frequency circuit 2a oscillator 2b amplifier 2c power distributor 2d directional coupler 2e mixer 3 signal processing circuit (signal processing means)
3a amplifier 3b BPF
3c A / D converter 3d Reference voltage generator 3e DSP
3f ROM
3g Trigger signal generator 4 Changeover switch 5 Constant voltage circuit 6 Power supply

Claims (2)

In a target detection device that is equipped with a high-speed flying object, transmits a transmission wave toward a target, and detects the target based on a Doppler frequency of a reflected wave from the transmission wave obtained from the target.
When the level of the scattered wave based on the transmission wave acquired after the high-speed flying object starts flying is below a predetermined extended determination threshold value, the detection range of the Doppler frequency is extended to the low frequency side and the target Comprising signal processing means for detecting an object ,
The signal processing means obtains frequency data composed of a frequency component included in the detection signal for detecting the Doppler frequency and the power of the frequency component in time series,
The power of the specific frequency data in which the frequency component is included in the scattered wave region on the low frequency side is set as the level of the scattered wave, and the level of the scattered wave immediately after the start of flight is set as the reference level. The target detection device is characterized in that when the level of the signal falls below the reference level and becomes less than or equal to the extended determination threshold, the Doppler frequency detection range is extended to the low frequency side . Target detection apparatus according to claim 1, wherein the level of the scattered waves to expand the detection range of the Doppler frequency and equal to or less than the instrument noise level to a lower frequency.

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