JP2011013182A - Target detector and method of detecting target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radar device capable of preventing several problems resulting from the saturation of a received signal acquired from a modulated pulse signal.SOLUTION: By a transmission timing determiner 111, transmission-control is exercised so that a pulse signal PPn for preliminary detection is transmitted during a preliminary detection mode and the signal is transmitted as a non-modulated pulse signal from a transmitter 12. Based on a received signal from a receiver 15, a position of a saturable target is detected by a detection scope detector 112 and stored in a map for the transmission control of a memory 113, the saturable target liable to be saturated in the receiver 15 by a received signal using a modulated pulse signal. Based on the position of the saturable target, the detection scope for saturation prevention is set by the timing determiner 111 and transmission-control is exercised so that the non-modulated pulse signal is used even in a scope where a modulated pulse signal is used in ordinary detection. A detection image is formed by an image former 17 based on the received signal of the non-modulated pulse signal by such transmission control and a pulse-compressed signal of the received signal of the modulated pulse signal.

Description

  The present invention relates to a target detection device such as a radar device that detects a target based on a reception signal obtained by reflecting a pulsed transmission signal to the target.

  Conventionally, there is a radar device that detects a target from a reflected signal by transmitting a pulse signal to a detection target region. In such a radar apparatus, there is a radar apparatus using pulse compression processing in order to improve the S / N of a received signal and improve the target detection performance.

  By the way, in a radar device using such a pulse signal, when an object having a large reflection cross-sectional area exists in the detection target region and the reception power is significantly increased, the reception signal is saturated by the LNA provided in the reception system. May end up. When the received signal is saturated in this way, the peak level of the received signal reaches its peak, and the S / N decreases, so that an accurate target detection result cannot be obtained. In particular, in the case of a radar apparatus using pulse compression processing that transmits a pulsed transmission signal (hereinafter referred to as a “modulation pulse signal”) composed of FM chirp signals, when the reception signal is saturated, the frequency component ratio of the reception signal And the frequency component ratio of the transmission signal do not coincide with each other, the level of the peak frequency is lowered or a range side lobe (side lobe on the time axis) is generated during pulse compression. For this reason, problems such as degradation of S / N and reflection signals from other objects being buried in the range side lobe occur, and accurate target detection cannot be performed.

For this reason, there are various methods as described below as methods for avoiding such saturation of the received signal.
(1) A so-called STC process, that is, a method for attenuating the received signal in an analog manner,
(2) A method for improving the dynamic range by providing two systems of a transmission system that does not attenuate the received signal and a transmission system that attenuates the received signal as shown in Patent Document 1.
(3) A method of detecting a saturation and switching between a transmission system that passes a received signal through the LNA and a transmission system that does not pass the received signal through the LNA, as shown in Patent Document 2.
There is.

Japanese Patent Laid-Open No. 2000-137071 Japanese Patent Laid-Open No. 9-72955

  However, when the above method (1) is used, the phase of the received signal changes with the attenuation of the amplitude of the received signal. Therefore, when the pulse compression processing is performed, S is the same as in the case of the saturation described above. / N deteriorates and a range side lobe occurs.

  Further, when the above method (2) is used, a plurality of receiving circuits must be provided, so that the scale of hardware is greatly increased. Further, the additional dynamic range that can be earned with such a circuit configuration is small, and saturation cannot be completely suppressed.

  Further, when the method (3) described above is used, the transmission system is switched by detecting saturation, so saturation occurs at the timing of detecting saturation.

  In view of such a problem, an object of the present invention is to realize a radar apparatus that can suppress the occurrence of problems caused by saturation of a received signal.

  The present invention relates to a target detection apparatus that detects different detection areas with different pulse-like signals, combines the detected information, and detects an area from an antenna position to a predetermined distance. The target detection apparatus includes a transmission unit, a reception unit, and a control unit.

  The transmission unit transmits at least two different pulse signals at a predetermined timing. The reception unit receives the reflected signal and generates a reception signal during a predetermined reception period corresponding to the transmitted pulse signal. The control unit detects whether or not the level of the received signal of the pulsed signal to be transmitted later exceeds a predetermined saturation threshold using the received signal with respect to the transmitted pulsed signal, and based on the detection result, the transmitting unit And control the receiver.

  In this configuration, it is possible to detect that the reception signal based on the pulse signal is saturated before the saturation actually occurs, and it is possible to execute various transmission / reception controls according to the saturation detection.

  In addition, the control unit of the target detection device of the present invention provides a detection result for a detection range detected when the level of the received signal exceeds the saturation threshold, even if the received signal is not saturated or the received signal is saturated. Control is performed so as to use a pulsed signal that does not affect the signal.

  In this configuration, as described above, since the occurrence of saturation can be detected in advance, transmission / reception control for setting a pulse signal so that the reception signal is not saturated can be executed before the reception signal is saturated, Saturation can be prevented.

  In addition, the control unit of the target detection apparatus of the present invention searches for a detection range detected when the level of the received signal exceeds the saturation threshold, using a pulse signal that does not saturate the level of the received signal.

  In this configuration, a specific saturation detection method is shown, and a saturation threshold corresponding to a saturation level of a pulse signal that actually causes saturation is set for a pulse signal that does not saturate the level of the received signal. Then, based on the fact that the pulse-like signal whose received signal level is not saturated exceeds the saturation threshold, it is possible to detect a detection range where the received signal will be saturated.

  In addition, the transmission unit of the target detection device of the present invention has predetermined two or more different pulse signals including at least a pulse signal for short range detection and a pulse signal for medium range detection. Send in order. The control unit searches for a detection range detected when the saturation threshold is exceeded, using a pulse-like signal for short range detection.

  This configuration shows the case where a pulse-like signal for short-range detection is used as a pulse-like signal used for specific saturation detection. The pulse-like signal for short-range detection is a region farther from the antenna. The fact that it is basically not saturated beyond the distance region is used. Then, by detecting saturation with the above-described saturation threshold up to the middle-range area with the pulse-like signal for short-range area detection in this way, the reception of the pulse-like signal actually set in the middle-range area is received. The detection range where the received signal will saturate can be detected before signal saturation occurs.

  In addition, the control unit of the target detection apparatus of the present invention searches for a detection range detected when the saturation threshold is exceeded, using a pulse-like signal having a constant carrier frequency.

  This configuration shows a case where a pulse signal (non-modulated pulse signal) having a constant carrier frequency is used as a pulse signal used for specific saturation detection.

  In addition, the control unit of the target detection apparatus of the present invention searches for a detection range that is detected when the carrier frequency is changed sequentially and the saturation level is exceeded, using a pulse-like signal whose amplitude level is limited.

  This configuration shows a case where a pulse signal (modulation pulse signal) whose carrier frequency changes is used as a pulse signal used for specific saturation detection.

  In addition, the control unit of the target detection apparatus of the present invention presets a preliminary detection mode for searching for a detection range detected when the saturation threshold is exceeded before the target detection process.

  In this configuration, since the possibility of saturation of the reception signal can be detected as the preliminary detection mode before the target detection is performed, the saturation of the reception signal can be prevented from the start of target detection.

  Further, the control unit of the target detection apparatus of the present invention searches for a detection range detected when the saturation threshold is exceeded, using a received signal obtained during the target detection process.

  In this configuration, the saturation of the received signal can be detected in advance even during the target detection process (during the target detection process in the normal detection mode and saturation avoidance detection mode described later), and movement is performed according to the detection result. Transmission / reception control can be performed.

  In addition, the control unit of the target detection apparatus of the present invention controls transmission / reception of a pulse signal for each direction centered on the antenna position.

  In this configuration, transmission / reception control for preventing saturation can be set in more detail including not only the distance but also the azimuth range.

  A pulse radar device according to the present invention includes the above-described target detection device and an image forming unit that forms a detection image based on a detection result obtained by the target detection device.

  In this configuration, the case where the above-described target detection device is used in a pulse radar device is shown, and it is possible to obtain an accurate target detection image corresponding to the surrounding situation by preventing saturation of the received signal. it can.

  According to the present invention, it is possible to prevent a decrease in S / N due to saturation of a received signal. In particular, when pulse compression is used, saturation of the received signal obtained from the modulated pulse signal can be prevented while actively using pulse compression processing using the modulated pulse signal. As a result, S / N degradation and range side lobe generation due to the saturation can be reliably prevented, and a radar apparatus having high target detection performance can be realized.

It is a block diagram which shows the main structures of the radar apparatus which concerns on embodiment of this invention. It is a figure which shows the concept of the map for transmission control. It is a figure which shows the transmission timing chart at the time of normal detection mode, and a figure which shows the concept of the detection range at the time of normal detection mode. It is a figure which shows the transmission timing chart at the time of preliminary | backup detection mode, and the figure which shows the concept of the detection range at the time of preliminary | backup detection mode. It is a figure which shows the transmission timing chart at the time of 1st saturation avoidance detection mode, and a figure which shows the concept of the detection range at the time of 1st saturation avoidance detection mode. It is a figure which shows the transmission timing chart at the time of 2nd saturation avoidance detection mode, and a figure which shows the concept of the detection range at the time of 2nd saturation avoidance detection mode. It is the figure which showed the example of a concept in the case of performing the detection process for saturation avoidance at the time of using a modulation pulse signal with respect to the normal short distance pulse detection range. It is a figure which shows an example of the database for transmission control.

  A target detection apparatus according to an embodiment of the present invention will be described with reference to the drawings. The target detection apparatus shown in the present embodiment is a radar apparatus, but may be another apparatus as long as it is an apparatus that detects a target using a pulse transmission signal.

FIG. 1 is a block diagram illustrating a main circuit configuration of a radar apparatus 10 according to the present embodiment.
As shown in FIG. 1, the radar apparatus 10 includes a transmission control unit 11, a transmission unit 12, a circulator 13, an antenna 14, a reception unit 15, a pulse compression unit 16, and an image forming unit 17.

  The transmission control unit 11 forms transmission control data that indicates the type, pulse width, amplitude, transmission timing, and the like of each pulse-shaped transmission signal generated by the transmission unit 12. The transmission control data set in this way is given from the transmission control unit 11 to the transmission unit 12 and the reception unit 15.

  Here, the types of pulse-shaped transmission signals are: an unmodulated pulse signal that forms a pulse-shaped waveform with a carrier signal of a constant frequency, and a pulse-shaped waveform that is formed by sequentially changing the frequency of the carrier signal. And a modulated pulse signal. In addition, the pulse width of the pulse-shaped transmission signal is determined based on the generated blind area distance, detection sensitivity, and distance resolution. The amplitude is determined according to the detection sensitivity and the operation mode of the radar apparatus 10. The transmission timing is determined according to the operation mode of the radar apparatus 10. Details of transmission control in each operation mode will be described later.

  The transmission unit 12 includes an oscillating element such as a semiconductor, generates a pulsed transmission signal composed of an unmodulated pulse signal or a modulated pulse signal based on transmission control data given from the transmission control unit 11, and supplies the pulsed transmission signal to the circulator 13. Output.

  The circulator 13 transmits the pulsed transmission signal from the transmission unit 12 to the antenna 14. The antenna 14 radiates the supplied pulsed transmission signal to the outside while continuing to rotate at a constant rotation speed at a predetermined rotation speed, and a reflected signal from an external target during a period when the pulsed transmission signal is not supplied. And outputs the received signal to the circulator 13. The circulator 13 outputs a reception signal from the antenna 14 to the reception unit 15.

  The receiving unit 15 includes an LNA (low noise amplifier), and amplifies and outputs a received signal. Transmission control data is given to the receiving unit 15. Based on the transmission control data, the receiving unit 15 outputs to the image forming unit 17 if the received signal is an unmodulated pulse signal, and if it is a modulated pulse signal. Output to the pulse compression unit 16. The unmodulated pulse signal and the modulated pulse signal output from the receiving unit 15 are also provided to the detection range segment detection unit 112 of the transmission control unit 11.

  The pulse compression unit 16 includes, for example, a Fourier transform unit, a matched filter, and an inverse Fourier transform unit. The pulse compression unit 16 performs pulse compression on the modulated pulse signal from the reception unit 15 by a known method, and converts the pulse-compressed signal into an image forming unit. 17 output.

  The image forming unit 17 forms detected image data using the reception signal of the non-modulated pulse signal from the receiving unit 15 and the signal after pulse compression from the pulse compressing unit 16. At this time, the image forming unit 17 performs known pulse integration processing as necessary. The pulse integration process is a process of integrating adjacent signals in the direction in which the sweep indicating the radiation direction of the radio wave from the antenna 14 rotates. The detected image data output from the image forming unit 17 is subjected to processing such as being displayed on a display (not shown).

  In such a radar apparatus 10, the reception signal is prevented from being saturated in the reception unit 15 by the specific transmission control of the transmission control unit 11 described below.

(Specific description of the transmission control unit 11)
The transmission control unit 11 includes a transmission timing determination unit 111, a detection range segment detection unit 112, and a memory 113.

  The transmission timing determination unit 111 is a functional unit that forms the above-described transmission control data, and executes transmission control according to the operation mode of the radar apparatus 10.

Here, the operation mode of the radar apparatus 10 includes the following operation modes.
A preliminary detection mode in which it is detected when the radar apparatus 10 is activated whether or not a target in which the reflected signal is saturated (hereinafter simply referred to as “saturable target”) is present in the detection target area.
A normal detection mode that is executed when a saturable target does not exist within the detection target area.
A saturation avoidance detection mode for detecting a target while avoiding saturation of a received signal when a target that can be saturated exists in the detection target area.

  The detection range segment detection unit 112 performs different processing in the above-described preliminary detection mode, normal detection mode, and saturation avoidance detection mode.

  In the preliminary detection mode, the detection range segment detection unit 112 acquires, for example, a reception signal based on an unmodulated pulse signal for preliminary detection, and whether the level of each reception signal is equal to or higher than a saturation threshold for preliminary detection. Is detected. Here, the saturation threshold for preliminary detection indicates a level at which the reception signal based on the modulated pulse signal in the normal detection state may be saturated when the reception unit 15 amplifies the undetected pulse signal for preliminary detection. Is converted to the level of the received signal by and is set to a value having a predetermined margin. Note that the pulse-like transmission signal for preliminary detection may be a modulated pulse signal.

  This detection processing is executed so that the preset preliminary detection range is a detection target in the distance direction over one rotation of the antenna. Then, when detecting a reception signal that is equal to or higher than the preliminary detection saturation possibility threshold, the detection range classification detection unit 112 calculates a corresponding azimuth and distance position and outputs a state transition signal to the transmission control map.

  In the normal detection mode and the saturation avoidance detection mode, the detection range segment detection unit 112 acquires the reception signal of the unmodulated pulse signal and the reception signal of the modulation pulse signal in the normal detection state or the saturation avoidance detection state.

  When the detection range division detection unit 112 acquires the reception signal based on the unmodulated pulse signal, the detection range division detection unit 112 detects whether the level of each reception signal is equal to or higher than the first saturation possibility threshold. Here, the first saturation possibility threshold is different from the above-described preliminary detection saturation possibility threshold, and may be saturated when the reception signal by the modulated pulse signal in the normal detection state is amplified by the reception unit 15. The level is converted to the level of the received signal by the non-modulated pulse signal in the normal detection state or the saturation avoidance detection state, and is set to a value having a predetermined margin.

  In addition, when the detection range segment detection unit 112 acquires the reception signal based on the modulation pulse signal, the detection range segment detection unit 112 detects whether the level of each reception signal is equal to or higher than the second saturation possibility threshold. Here, unlike the above-described saturation threshold for preliminary detection, the second saturation possibility threshold is saturated when the reception signal by the modulation pulse signal in the normal detection state or the saturation avoidance detection state is amplified by the reception unit 15. Is set to a value having a predetermined margin with respect to a reference value when setting the first saturation possibility threshold for the above-described non-modulated pulse signal.

  This detection process is continuously executed in the normal detection state and the saturation avoidance detection state. Then, when detecting a reception signal that is equal to or higher than the first saturation possibility threshold and a reception signal that is equal to or higher than the first saturation possibility threshold, the detection range classification detection unit 112 calculates a corresponding azimuth and distance position and transmits a transmission control map. A state transition signal is output to.

The memory 113 stores the pulse width of the unmodulated pulse signal and the pulse width of the modulated pulse signal according to the distance resolution. Specifically, the pulse width W _{PS of} the short-distance detection pulse signal PSn (n is a positive integer) composed of an unmodulated pulse signal in the normal detection mode, and the intermediate-distance detection pulse signal PMn composed of a modulated pulse signal. A pulse width W _{PM of} (n is a positive integer) and a pulse width W _{PL of a} long-distance detection pulse signal PLn (n is a positive integer) composed of a modulated pulse signal are stored. At this time, since the pulse signal PSn is a non-modulated pulse signal and the pulse signals PMn and PLn are modulated pulse signals that perform pulse compression, the distance resolution by the received signal of the pulse signal PSn and the pulse signals PMn and PLn The distance resolution by the signal after pulse-compressing the received signal is set to match. Further, the memory 113 also stores a pulse width W _PP of a pulse signal PPn (n is a positive integer) for preliminary detection, which is a non-modulated pulse signal in the preliminary detection mode.

  The memory 113 stores the amplitude of each pulse signal PSn, PMn, PLs and the amplitude for preliminary detection of the pulse signal PPn for preliminary detection. The amplitude for the preliminary detection is set lower than the amplitude of the pulse signal PSn for short distance detection described above even for the same unmodulated pulse signal. The amount of amplitude reduction is such that the received signal does not saturate in the receiving unit 15 even if the target having the largest reflection cross-sectional area among the targets to be detected exists in the preliminary detection range. Is set.

The memory 113 includes a transmission / reception period RT _S based on a short-range detection pulse signal PSn, a transmission / reception period RT _M based on a medium-range detection pulse signal PMn, and a long-distance detection according to the distance for each detection range in the normal detection mode. The transmission / reception period RT _L by the pulse signal PLn and the repetition period (PRF) of the pulse group are stored. The repetitive cycle of a pulse group is a pulse train composed of a short-range detection pulse signal PSn, a medium-range detection pulse signal PMn, and a long-range detection pulse signal PLn, and the group is repeatedly transmitted. This indicates the cycle. Further, the memory 113, transceiver period RT _P is stored by the pulse signal PPn for preliminary detection in accordance with the distance of the pre-detection range in the preliminary detection mode. Furthermore, the memory 113 stores the transmission / reception time RTS _′ for the unmodulated pulse signal according to the distance of the detection range of the unmodulated pulse signal used in the saturation avoidance detection mode.

  The memory 113 stores a transmission control map, which is updated and stored based on the state transition signal from the detection range segment detection unit 112. The transmission control map that is updated and stored is read by the transmission control unit 111 and used for transmission control.

  FIG. 2 is a diagram showing the concept of the transmission control map. FIG. 2A shows a case where the detection range for saturation avoidance is set only by the distance, and FIG. 2B shows a case where the detection range for saturation avoidance is set by the distance and the direction.

  As shown in FIG. 2, the transmission control map conceptually has a structure in which individual state data having a predetermined resolution is arranged in a two-dimensional region in the distance R direction and the azimuth θ direction (sweep rotation direction). Become. Note that FIG. 2 also shows a long-range pulse detection range, that is, a range where the distance R is a long-distance range, but actually, if at least a range in the distance R direction that is included in the preliminary detection range is stored. Good. Each individual state data is a state transition by a state transition signal when a received signal equal to or higher than the saturation possibility threshold is detected. For example, if a state transition signal is not received, the target individual state data is “ If it is “0” and the state transition signal is received, the target individual state data is “1”.

  In the above description, by setting a predetermined margin for the saturation possibility threshold, not only a region where the received signal is surely saturated but also a region that is likely to be saturated is set as a saturation possibility region. However, after setting the saturation possibility region without having a margin in the saturation possibility threshold, the saturation possibility region may be set widely according to the margin on the map.

  Next, control processing in each operation mode performed by the transmission control unit 11 will be described in more detail. In the present embodiment, the detection range is divided into three ranges, a short-range pulse detection range, a medium-range pulse detection range, and a long-range pulse detection range, and a different pulse-shaped transmission signal is transmitted to each to detect a target. An example is given below. In this embodiment, an example in which an unmodulated pulse signal is used as a pulse-like transmission signal for a short distance range and a modulated pulse signal is used as a pulse-like transmission signal for a medium distance range and a long distance range is shown.

Normal Detection Mode First, in order to facilitate the description of the following preliminary detection mode and saturation avoidance detection mode, transmission control in the normal detection mode will be described. Note that the normal detection mode referred to here is an operation mode that is executed when there is no saturable target in the preliminary detection mode described later. Here, the saturable target is a target whose received signal of a modulated pulse signal (especially, a modulated pulse signal used for a middle-range pulse detection range) may be saturated in the receiving unit 15. Show.

  FIG. 3A is a diagram showing a transmission timing chart in the normal detection mode, and FIG. 3B is a diagram showing a concept of a detection range in the normal detection mode.

  When the transmission timing determination unit 111 of the transmission control unit 11 detects that all the individual state data in the transmission control map of the memory 113 is “0”, it determines that the normal detection mode is set.

When the transmission timing determination unit 111 detects the normal detection mode, the transmission timing determination unit 111 obtains the pulse width W _PS of the pulse signal PSn, the pulse width W _PM of the pulse signal PMn, and the pulse width W _PL of the pulse signal PLn from the memory 113. read out. Further, the transmission timing determination unit 111 reads the amplitudes of the pulse signals PSn, PMn, and PLs. Further, the transmission timing determination unit 111 reads the transmission / reception period RT _S based on the pulse signal PSn, the transmission / reception period RT _M based on the pulse signal PMn, the transmission / reception period RT _L based on the pulse signal PLn, and the repetition period (PRF) of the pulse group.

  Then, the transmission timing determination unit 111 transmits each pulse-shaped transmission signal (pulse signals PSn, PMn, PLn) with a set amplitude based on the pulse width, the transmission / reception period, and the repetition period PRF of the pulse group. Transmission control data is given to the transmission unit 12.

In accordance with the transmission control data, the transmission unit 12 first transmits a pulse signal PS1 composed of an unmodulated pulse signal with a pulse width W _{PS as shown} in FIG. Then, the transmission timing of the pulse signal PS1 after reception period RT _S, transmits a pulse signal PM1 consisting modulated pulse signal with a pulse width _{W PM.} Then, the transmission timing of the pulse signal PM1 after reception period RT _M, transmits a pulse signal PL1 consisting of modulated pulse signal with a pulse width _{W PL.} Then, the transmission timing of the pulse signal PL1 after reception period RT _L, again, sends the pulse signal PS2 consisting of non-modulated pulse signal with a pulse width _{W PS.}

  Then, the transmission unit 12 repeatedly executes such sequential transmission of the pulse signals PSn, PMn, and PLn according to the repetition period (PRF) of the pulse group.

Receiver 15, the reception period of the period RT _S short-range detection and acquires a reception signal based on the pulse signal PSn is a non-modulated pulse signal. The receiving unit 15 outputs the received signal to the image forming unit 17.

Receiver 15, the reception period of the period RT _M intermediate- detection acquires the reception signal based on the pulse signal PMn a modulated pulse signal. The pulse compression unit 16 performs pulse compression on the received signal and outputs it to the image forming unit 17.

Receiver 15, the reception period of the period RT _L of long-range detection and acquires a reception signal based on the pulse signal PLn a modulated pulse signal. The pulse compression unit 16 performs pulse compression on the received signal and outputs it to the image forming unit 17.

  Such a normal detection process is performed when a target (saturable target) in which the reception signal of the modulated pulse signal is saturated by the receiving unit 15 is not detected in the preliminary detection mode to be described later, or when the normal detection immediately before is detected. This process is executed when no saturable target is detected in the process, and when no saturable target is detected in the immediately preceding saturation avoidance detection process. Therefore, since the reception signal of the modulated pulse signal output from the receiving unit 15 is not saturated, the S / N does not decrease and the range side lobe during pulse compression does not occur. Therefore, a good detection image can be obtained.

  In such a normal detection mode, the detection range segment detection unit 112 sequentially obtains a reception signal, and for a reception signal of an unmodulated pulse signal of a short distance detection, an unmodulated pulse signal of a short distance detection. The detection of the saturable target is continuously performed based on the first satisfiability threshold value set for use. In addition, the detection range segment detection unit 112 continuously performs detection of a saturation possibility target based on the second saturation possibility threshold set for the modulation pulse signal for medium distance detection. Then, the detection range segment detection unit 112 updates the transmission control map in the memory 113 based on these detection results. Thereby, even if the state of the detection range changes due to the movement of the target or the ship in the normal detection mode, the detection image can be continuously formed without saturating the received signal.

Preliminary detection mode When the radar apparatus 10 is activated, the transmission control unit 11 determines whether there is a target that may cause the reception signal of the modulated pulse signal to be saturated in the reception unit 15 in the preliminary detection mode. To do.

  FIG. 4A is a diagram showing a transmission timing chart in the preliminary detection mode, and FIG. 4B is a diagram showing a concept of a detection range in the preliminary detection mode.

When the transmission timing determination unit 111 enters the preliminary detection mode, the pulse width W _PP of the pulse signal PPn, the transmission / reception period RT _P , and the amplitude for preliminary detection are read from the memory 113.

Then, the transmission timing determination unit 111, these pulse width W _PP, based on the reception period RT _P, transmitting to transmit a pulse signal PPn for preliminary detection consisting of non-modulated pulse signal with an amplitude of spare detecting section 12 is given transmission control data. At this time, the transmission timing determination unit 111 sets the preliminary detection pulse signal PPn to be transmitted over one rotation (one sweep) of the antenna 14.

As shown in FIG. 4A, the transmission unit 12 determines the preliminary detection pulse signals PP1 to PPα (α is determined by the azimuth resolution), which is composed of an unmodulated pulse signal having a pulse width WPP, in accordance with the transmission control data. a positive integer) the interval between transmission and reception period RT _P, sequentially transmits over one sweep. In this case, transmission and reception period RT _P is set longer than the transmission and reception period RT _S for short pulse detection range, thereby, up to a predetermined range of medium-range pulse detection range, it is possible to pre-detection range .

  The reception unit 15 acquires a reception signal based on the preliminary detection pulse signal PPn and outputs the reception signal to the detection range segment detection unit 112. At this time, since the amplitude of the pulse signal PPn is reduced, the reception signal based on the pulse signal PPn is not saturated.

  The detection range segment detection unit 112 detects a target within the preliminary detection range from the reception signal based on the pulse signal PPn, and determines whether the level of the reception signal is equal to or higher than a preset saturation threshold for preliminary detection. To detect. Then, if there is a received signal equal to or greater than the preliminary detection saturation possibility threshold, the detection range classification detection unit 112 detects the distance and direction of the saturation possibility target from the received signal and generates a state transition signal. Then, as shown in FIGS. 2A and 2B, the detection range segment detection unit 112 sets the individual state data of the distance and direction corresponding to the saturable target in the transmission control map of the memory 113 to “1”. To "". For example, in the case of FIGS. 2A and 2B, the individual state data of the azimuths θ2 and θ3 of the distance Ds1, the individual state data of the azimuths θ1 and θ4 of the distance Ds2, and the individual state data of the azimuth θ5 of the distance Ds3. Is set to “1”. Thereby, the transmission control part 11 can know the presence or absence and presence position of a saturation possibility target.

  The transmission timing determination unit 111 of the transmission control unit 11 reads the transmission control map stored in the memory 113, and if there is a saturable target (if there is individual state data of “1”), A saturation avoidance detection mode to be described later is executed. On the other hand, if there is no saturable target (if there is no individual state data “1”), the transmission timing determination unit 111 executes the above-described normal detection mode.

Saturation avoidance detection mode When it is detected in the above-described preliminary detection mode that a saturation possibility target exists, the transmission control unit 11 performs saturation avoidance as shown in FIGS. 5 and 6 different from the normal detection mode. The transmission range is controlled by setting the detection range.

  FIG. 5A is a diagram showing a transmission timing chart in the first saturation avoidance detection mode, and FIG. 5B is a diagram showing a concept of a detection range in the first saturation avoidance detection mode. FIG. 6A is a diagram illustrating a transmission timing chart in the second saturation avoidance detection mode, and FIG. 6B is a diagram illustrating a concept of a detection range in the second saturation avoidance detection mode. .

(1) In the case of the first saturation avoidance detection mode In the first saturation avoidance detection mode, as shown in FIG. 2A, the detection range for saturation avoidance is set only by the distance.

  When the transmission timing determination unit 111 reads the transmission control map (see FIG. 2) stored in the memory 113 and detects that there is individual state data of “1”, the transmission timing determination unit 111 of “1” exists at the farthest distance position. The individual state data is detected, and the longest distance that defines the detection range for avoiding saturation is acquired. For example, in the case of FIG. 2A, the distances Ds1, Ds2, and Ds3 corresponding to the individual state data “1” are read, and the distance Ds3 is detected as the longest distance.

  As shown in FIG. 2A, the transmission timing determination unit 111 sets the range on the own device side as a detection range for saturation avoidance from the acquired longest distance. Specifically, if the longest distance Ds3 is outside the short distance pulse detection range, the transmission timing determination unit 111 sets the omnidirectional range up to the longest distance Ds3 as the saturation avoidance detection range. The transmission timing determination unit 111 sets the pulse signal PSn used in the short-range pulse detection range in the normal detection mode within the detection range for saturation avoidance. On the other hand, if the longest distance is within the short-range pulse detection range, the transmission timing determination unit 111 performs the same transmission control as in the normal detection mode.

Further, the transmission timing determination unit 111 determines a reception period RT S _'of the pulse signal PSn Maximum Distance acquired. This transmission / reception period RTS _′ is set to a time corresponding to the acquired longest distance if the saturable target is outside the short-range pulse detection range in the normal detection mode, and the saturable target is set in the normal detection mode. within short pulse detection range of time, it is set equal to the transmit and receive periods RT _S in the normal detection mode. Incidentally, transmission and reception period RT _L of the pulse signal PLn for transmission and reception period RT _M and long detection pulse signal PMn for middle distance detection is not changed. Then, the transmission timing determination unit 111 _'according to the setting of the repetition period of the pulse group is also PRF from PRF' the reception period RT _S is set to.

The transmission timing determination unit 111 generates transmission control data including the transmission / reception period RTS _′ and the pulse group repetition period PRF ′, and supplies the transmission control data to the transmission unit 12.

In accordance with the transmission control data for avoiding saturation, the transmission unit 12 first transmits a pulse signal PS1 composed of an unmodulated pulse signal with a pulse width W _{PS as shown} in FIG. Next, after a transmission / reception period RTS _′ from the transmission timing of the pulse signal PS1, a pulse signal PM1 including a modulation pulse signal is transmitted with a pulse width W _PM . Then, the transmission timing of the pulse signal PM1 after reception period RT _M, transmits a pulse signal PL1 consisting of modulated pulse signal with a pulse width _{W PL.} Then, the transmission timing of the pulse signal PL1 after reception period RT _L, again, sends the pulse signal PS2 consisting of non-modulated pulse signal with a pulse width _{W PS.}

  Then, the transmission unit 12 repeatedly executes such sequential transmission of the pulse signals PSn, PMn, and PLn according to the repetition period (PRF ′) of the pulse group.

The reception unit 15 acquires a reception signal based on the pulse signal PSn that is an unmodulated pulse signal in the reception period of the transmission / reception period RTS _′ set for saturation avoidance. The receiving unit 15 outputs a received signal to the image forming unit 17.

Receiver 15, the reception period of the period RT _M intermediate- detection acquires the reception signal based on the pulse signal PMn a modulated pulse signal. The pulse compression unit 16 performs pulse compression on the received signal and outputs it to the image forming unit 17.

Receiver 15, the reception period of the period RT _L of long-range detection and acquires a reception signal based on the pulse signal PLn a modulated pulse signal. The pulse compression unit 16 performs pulse compression on the received signal and outputs it to the image forming unit 17.

  By detecting such a target for saturation avoidance, even if there is a saturable target, the detection of the target that can be saturated is performed with an unmodulated pulse signal, and the modulated pulse signal is not used. . For this reason, it is possible to prevent the S / N drop caused by saturation of the received signal of the modulated pulse signal and the generation of range side lobes that occur during the pulse compression process. As a result, the received signal is saturated by using the modulated pulse signal, and a saturable target that cannot be detected accurately can be detected accurately using the unmodulated pulse signal. Since a modulated pulse signal can be used for distance ranges farther than the saturable target, target detection can be performed with high range resolution while maintaining high S / N for these ranges. It can be performed. Thereby, a reliable and highly accurate detection image can be formed.

(2) Second Saturation Avoidance Detection Mode In the second saturation avoidance detection mode, as shown in FIG. 2B, a saturation avoidance detection range is set by distance and direction.

  When the transmission timing determination unit 111 reads the transmission control map (see FIG. 2) stored in the memory 113 and detects that there is individual state data of “1”, the transmission timing determination unit 111 of “1” exists at the farthest distance position. The individual state data is detected, and the longest distance that defines the detection range for avoiding saturation is acquired. For example, in the case of FIG. 2B, the distances Ds1, Ds2, and Ds3 corresponding to the individual state data of “1” are read, and the distance Ds3 is detected as the longest distance.

  In addition, the transmission timing determination unit 111 acquires an azimuth range in which the individual state data “1” is distributed. For example, in the case of FIG. 2B, the orientations θ1, θ2, θ3, θ4, and θ5 corresponding to the individual state data of “1” are read, and the orientation ranges θ1 to θ5 are acquired.

  The transmission timing determination unit 111 sets a detection range for saturation avoidance from the acquired longest distance Ds3 and the azimuth ranges θ1 to θ5 as shown in FIG. Specifically, if the longest distance is outside the short-range pulse detection range, the transmission timing determination unit 111 saturates to include the azimuth range corresponding to the longest distance and the short-range pulse detection range in the normal detection mode. Set a detection range for avoidance. Then, the transmission timing determination unit 111 sets the pulse signal PSn used in the short-range pulse detection range in the normal detection mode with respect to the set detection range for saturation avoidance. In the description of the present embodiment, the case where there is one set of the longest distance Ds3 and the azimuth ranges θ1 to θ5 is shown. However, when there are a plurality of sets, the saturation avoidance is made corresponding to each set. What is necessary is just to set a detection range. On the other hand, if the longest distance is within the short-range pulse detection range, the transmission timing determination unit 111 performs the same transmission control as in the normal detection mode.

Further, the transmission timing determination unit 111 determines a reception period RT _{S 'of} the pulse signal PSn Maximum Distance Ds3 obtained. The reception period RT S _', if the saturation potential target object is a short pulse detection range of the normal detection mode is set in accordance with the longest distance Ds3 acquired, saturated possibility target object is in the normal detection mode within short pulse detection range, it is set equal to the transmit and receive periods RT _S in the normal detection mode. Such setting of transmission and reception period RT S _'is applied only to the azimuth range set for the saturation avoidance, in other azimuth range, it is transmitted and received time RT _S normal short pulse detection range is applied. Incidentally, transmission and reception period RT _L of the pulse signal PLn for transmission and reception period RT _M and long detection pulse signal PMn for middle distance detection does not change regardless of the orientation. Then, the transmission timing determination unit 111, the transmission and reception period RT _{S ',} depending on the setting of RT _S, the repetition period of the pulse group PRF for each azimuth range' is set to or PRF.

Transmission timing determination section 111, these transmission and reception period RT _{S ',} the repetition period of RT _S and pulse group PRF', generates a transmission control data including the PRF, giving to the transmission unit 12.

  In accordance with the transmission control data for avoiding saturation, the transmission unit 12, as shown in FIG. 6 (A), has an azimuth range in which the detection range for saturation avoidance is within the short-range pulse detection range (for example, PS1 in FIG. , PS2, PS3) and the azimuth range in which the detection range for saturation avoidance is outside the short-range pulse detection range (for example, the range of PSm, PSm + 1 in FIG. 6) is transmitted at different timings.

First, in the azimuth range where the detection range for saturation avoidance is within the short-range pulse detection range, for example, in the case of transmission of the pulse signal PS1 to pulse signal PS2, the pulse signal PS1 composed of an unmodulated pulse signal is transmitted with the pulse width W _PS . To do. Then, the transmission timing of the pulse signal PS1 after reception period RT _S, transmits a pulse signal PM1 consisting modulated pulse signal with a pulse width _{W PM.} Then, the transmission timing of the pulse signal PM1 after reception period RT _M, transmits a pulse signal PL1 consisting of modulated pulse signal with a pulse width _{W PL.} Then, the transmission timing of the pulse signal PL1 after reception period RT _L, again, sends the pulse signal PS2 consisting of non-modulated pulse signal with a pulse width _{W PS.} Then, the transmission unit 12 repeatedly executes such sequential transmission of the pulse signals PSn, PMn, and PLn according to the repetition period (PRF) of the pulse group.

On the other hand, in the azimuth range where the detection range for avoiding saturation is outside the short-range pulse detection range, for example, in the case of transmission of pulse signal PSm to pulse signal PSm + 1, a pulse signal PSm composed of an unmodulated pulse signal is transmitted with a pulse width W _PS . To do. Then, the transmission timing of the pulse signal PSm after reception period RT _{S ',} transmits a pulse signal PMm consisting modulated pulse signal with a pulse width _{W PM.} Then, the transmission timing of the pulse signal PMm after reception period RT _M, transmits a pulse signal PLm consisting modulated pulse signal with a pulse width _{W PL.} Then, the transmission timing of the pulse signal PLm after reception period RT _L, again, transmits a pulse signal PSm + 1 consisting of non-modulated pulse signal with a pulse width _{W PS.} Then, the transmission unit 12 repeatedly executes such sequential transmission of the pulse signals PSn, PMn, and PLn according to the repetition period (PRF ′) of the pulse group.

Receiver 15, the reception period of the reception period RT _S or saturated avoid reception period is set for RT S _'to obtain a received signal based on the pulse signal PSn is a non-modulated pulse signal. The receiving unit 15 outputs the received signal to the image forming unit 17.

Receiver 15, the reception period of the period RT _M intermediate- detection acquires the reception signal based on the pulse signal PMn a modulated pulse signal. The pulse compression unit 16 performs pulse compression on the received signal and outputs it to the image forming unit 17.

Receiver 15, the reception period of the period RT _L of long-range detection and acquires a reception signal based on the pulse signal PLn a modulated pulse signal. The pulse compression unit 16 performs pulse compression on the received signal and outputs it to the image forming unit 17.

  By performing such target detection for saturation avoidance, the same effect as in the first saturation avoidance detection mode can be obtained. Furthermore, when this second saturation avoidance detection mode is used, normal detection processing is performed except for the direction in which the saturable target exists, so that the saturable target exists in the middle-range pulse detection range. Even so, it is possible to perform the target detection using the modulated pulse signal in the other azimuth range even at the same distance position as the saturable target. Thereby, a highly accurate detection image can be formed in consideration of all directions.

  In these saturation avoidance detection modes as well, as in the above-described normal detection mode, the detection range segment detection unit 112 sequentially acquires reception signals, and for the reception signals of the non-modulation pulse signals, the non-modulation pulse signals The detection of the saturable target is continuously performed based on the first satisfiability threshold value set for use. In addition, the detection range segment detection unit 112 continuously performs detection of a saturation possibility target based on the second saturation possibility threshold set for the modulation pulse signal. Then, the detection range segment detection unit 112 updates the transmission control map in the memory 113 based on these detection results. Thereby, even if the situation of the detection range changes due to the movement of the target or the ship in the saturation avoidance detection mode, the detection image can be continuously formed without saturating the received signal.

  In the above description, the case where an unmodulated pulse signal is used for the short-range pulse detection range is shown. This is due to the fact that the vicinity of the device itself has a high reflected signal level and can detect a target with a sufficient distance resolution without using a modulated pulse signal. However, it is also possible to use a modulated pulse signal for the normal short-range pulse detection range.

  For example, FIG. 7 is a diagram showing an example of a concept when performing detection processing for avoiding saturation when a modulated pulse signal is used for a short-range pulse detection range. In the example of FIG. 7, the detection range for saturation avoidance is set only in the direction where the saturable target exists, and an unmodulated pulse signal is used. Even with such a method, the above-described effects can be obtained.

In the above description, an example using a two-dimensional transmission control map corresponding to a detection area is shown, but a transmission control database as shown in FIG. 8 may be used.
8A is a transmission control database corresponding to the transmission control map of FIG. 2A, and FIG. 8B is transmission control corresponding to the transmission control map of FIG. FIG. 8C is a database in which the relationship between the distance Ds detected by the saturation possibility threshold and the reception period RT _s is stored.

In the case of FIG. 8A, that is, when the detection range for saturation avoidance is set only by the distance from the antenna position, the longest distance and the corresponding reception period are stored in the database. In this case, in the preliminary detection mode, the longest distance Ds3 for determining the detection range for saturation avoidance is acquired from the reception signal for one rotation of the antenna, and the reception period is set to RT _S3 based on the database of FIG. Set to ^' . Thereafter, in the normal detection mode and the saturation avoidance detection mode, the longest distance is updated based on sequentially received signals, and the reception period RT _s is set based on the updated longest distance and the database shown in FIG. Update.

In the case of FIG. 8B, that is, when a detection range for avoiding saturation is set by the distance from the antenna position and the azimuth, the database detects the azimuth detected when saturation occurs and the saturation for each azimuth. The detection distance of the possibility target, the longest distance in the detection distance, and the reception period are stored. In this case, in the preliminary detection mode, the azimuth θ1 to θ5 for determining the detection range for saturation avoidance from the reception signal for one rotation of the antenna and the longest distance Ds3 obtained from the detection distance of each azimuth θ1 to θ5 are acquired. , based on a database of FIG. 8 (C), the set reception period corresponding to the longest distance Ds3 to _{RT S3} ^'. Then, in the normal detection mode and saturated avoid detection mode, we intend to update the azimuth on the basis of the received signal sequentially obtained, based on a database of longest distance to FIG. 8 (C), the updating reception period RT _s.

  Furthermore, in the above description, an example in which an unmodulated pulse signal is used for preliminary detection is shown. However, a modulated pulse signal whose amplitude is sufficiently reduced so that the received signal is not saturated may be used.

  In the above description, an example is shown in which a short-range pulse detection range, a medium-range pulse detection range, and a long-range pulse detection range are divided into three detection ranges. However, the number of divisions is not limited to this, and a plurality of detection ranges may be used. What is necessary is just to be divided into the range.

  In the above description, whether or not the reception signal of the non-modulated pulse signal is saturated is not particularly described. Of course, the transmission power may be set so as not to be saturated. However, even if the non-modulated pulse signal is saturated, it is not used for the pulse compression process, so that adverse effects due to the use of the pulse compression process can be prevented.

  Further, in each of the above-described embodiments, the radar apparatus 10 is described as an example of the target detection apparatus, but the above-described configuration can be similarly applied to a target detection apparatus other than the radar apparatus. For example, the present invention can be applied to a sonar or a fish finder that transmits a pulsed ultrasonic signal from an ultrasonic transducer and receives a reflected signal.

10-radar apparatus, 11-transmission control unit, 111-transmission timing determination unit, 112-detection range section detection unit, 113-memory, 12-transmission unit, 13-circulator, 14-antenna, 15-reception unit, 16- Pulse compression unit, 17-image forming unit

Claims (19)

A target detection apparatus that detects different detection areas with different pulse signals, combines the detected information, and detects an area from the antenna position to a predetermined distance,
A transmitter that transmits at least two different pulse signals at a predetermined timing;
A receiving unit that receives the reflected signal and generates a received signal in a predetermined reception period according to the transmitted pulse signal;
Using the received signal for the transmitted pulsed signal, it is detected whether the level of the received signal of the pulsed signal to be transmitted subsequently exceeds a predetermined saturation threshold, and based on the detection result, the transmitter and the reception A control unit for controlling the unit,
This is a target detection device. For the detection range detected when the level of the received signal exceeds the saturation threshold, the control unit does not saturate the received signal or does not affect the detection result even if the received signal is saturated. Control to use the signal,
The target detection apparatus according to claim 1. The control unit searches for a detection range that is detected when the level of the received signal exceeds the saturation threshold, using a pulsed signal that does not saturate the level of the received signal.
The target detection apparatus of Claim 1 or Claim 2. The transmission unit transmits at least two different pulse signals including a pulse signal for short range detection and a pulse signal for medium range detection in a predetermined order,
The control unit searches for a detection range detected when the saturation threshold is exceeded, using the pulse-like signal for near-field detection.
The target detection apparatus of Claim 1 or Claim 2. The control unit searches for a detection range detected when the saturation threshold is exceeded using a pulsed signal having a constant carrier frequency.
The target detection apparatus of Claim 1 or Claim 2. The control unit searches for a detection range that is detected when the saturation threshold is exceeded, using a pulse signal in which the carrier frequency sequentially changes and the amplitude level is limited,
The target detection apparatus of Claim 1 or Claim 2. The controller sets in advance a preliminary detection mode for searching for a detection range detected when the saturation threshold is exceeded before the target detection process.
The target detection apparatus according to claim 1. The control unit searches for a detection range detected when the saturation threshold is exceeded, using the received signal obtained during target detection processing.
The target detection apparatus in any one of Claims 1-7. The control unit controls transmission / reception of a pulse signal for each direction centered on the antenna position.
The target object detection apparatus in any one of Claims 1-8. The target detection device according to any one of claims 1 to 9,
An image forming unit that forms a detection image based on a detection result obtained by the target detection device;
A pulse radar device characterized by that. A target detection method for detecting different detection areas with different pulse-like signals and combining the detected information to detect an area from the antenna position to a predetermined distance,
At least two or more different pulse signals are transmitted at a predetermined timing, a reflected signal is received during a predetermined reception period corresponding to the transmitted pulse signal, and a reception signal is generated.
Using the received signal for the transmitted pulse signal, detect whether the level of the received signal of the pulse signal to be transmitted thereafter exceeds a predetermined saturation threshold, and perform transmission / reception control based on the detection result,
A target detection method characterized by this. For a detection range detected when the level of the received signal exceeds the saturation threshold, a pulse signal that does not affect the detection result even if the received signal is not saturated or the received signal is saturated is used. Control,
The target detection method according to claim 11. Using a pulsed signal that does not saturate the level of the received signal, search for a detection range that is detected when the level of the received signal exceeds the saturation threshold;
The target detection method according to claim 11 or 12. Two or more different pulse signals including at least a pulse signal for short range detection and a pulse signal for medium range detection are transmitted in a predetermined order, and a pulse signal for short range detection is transmitted. To search for a detection range detected when the saturation threshold is exceeded,
The target detection method according to claim 11 or 12. Search for a detection range detected when the saturation threshold is exceeded using a pulsed signal having a constant carrier frequency,
The target detection method according to claim 11 or 12. Searching for a detection range detected when the saturation threshold is exceeded, using a pulsed signal in which the carrier frequency changes sequentially and the amplitude level is limited,
The target detection method according to claim 11 or 12. Prior to the target detection process, a preliminary detection mode for searching for a detection range detected when the saturation threshold is exceeded is preset.
The target detection method in any one of Claims 11-16. Using the received signal obtained during the target detection process, search for a detection range detected when the saturation threshold is exceeded,
The target detection method in any one of Claims 11-17. Control transmission / reception of pulsed signals according to the orientation centered on the antenna position,
The target detection method in any one of Claims 11-18.

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