Radar apparatus and signal processing method

Abstract

To provide a radar device capable of preventing an amplitude value of a reception signal from being saturated.SOLUTION: The radar device 1 includes an amplitude-value detecting unit 31, a saturation-suppression-information generating unit 33, and a signal amplifier 25a. The amplitude value detection unit 31 detects an amplitude value of the reception signal. A saturation suppression information generation unit 33 generates saturation suppression information which is information indicating an adjustment amount of an amplitude value according to a distance from an own device and is information for preventing the amplitude value of the reception signal from being saturated on the basis of at least the amplitude value of the reception signal received immediately before. The signal amplifier 25a adjusts the amplification value of the reception signal using the saturation suppression information generated by the saturation suppression information generation unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention mainly relates to a radar device that adjusts the amplitude value of a received signal. [Background technology]

[0002] The antenna of a radar device receives not only reflected waves from targets or land, but also reflected waves from ocean waves and waves reflected from rain and snow. Therefore, in order to remove such unwanted reflected waves, a process of subtracting the amplitude value of the received signal according to the distance from the radar device has been conventionally performed. Patent Document 1 discloses this type of radar device.

[0003] The radar device in Patent Document 1 performs STC (Sensitivity Time Control). STC is a process used to remove sea clutter and adjust the signal level of a received signal according to the distance from the radar. Specifically, when a signal is received from a short distance, the sensitivity is lowered to suppress the amplitude value, and as the distance increases, the sensitivity is increased to increase the amplitude value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-120487 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the reflected wave from a distant target is attenuated, resulting in a small amplitude value of the received signal representing that target. However, if a large target is present at a long distance, the amplitude value of the received signal representing that target is large, and therefore, by performing the above-described STC on this received signal, the amplitude value of the received signal becomes even larger. In this case, the amplitude value of the received signal may exceed the upper limit (become saturated). As a result, the radar device is unable to calculate an accurate amplitude value.

[0006] In addition, radar devices have been known that transmit a transmission signal with a long pulse width and compress the pulse width of the received signal by performing pulse compression processing to improve the S / N ratio. In this type of radar device, if the amplitude value of the received signal becomes saturated, time side lobes may occur, making it impossible to appropriately compress the pulse width.

[0007] The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a radar device that can prevent the amplitude value of a received signal from becoming saturated.

[0008] The problem to be solved by the present invention is as described above. Next, the means for solving this problem and the effects thereof will be explained.

[0009] According to a first aspect of the present invention, there is provided a radar device that transmits a transmission signal to the outside and receives a reflected wave of the transmission signal as a reception signal, the radar device comprising: an amplitude value detection unit, a saturation suppression information generation unit, and an adjustment unit. The amplitude value detection unit detects the amplitude value of the reception signal. The saturation suppression information generation unit generates saturation suppression information, based on at least the amplitude value of the reception signal received most recently, which indicates an adjustment amount of the amplitude value according to the distance from the radar device itself and is information for preventing saturation of the amplitude value of the reception signal. The adjustment unit adjusts the amplitude value of the reception signal using the saturation suppression information generated by the saturation suppression information generation unit.

[0010] This prevents the amplitude value of the received signal from saturating (exceeding the upper limit.) Therefore, even if a large target exists at a long distance, for example, the accurate amplitude value of the received signal indicating the target can be determined.

[0011] In the radar device, it is preferable that the adjustment unit constitutes a part of a receiving unit that receives the received signal, and performs processing to amplify the amplitude value of the received signal based on the saturation suppression information.

[0012] In other words, if the amplitude value is amplified before the amplitude value is adjusted by the adjustment unit, the amplitude value of the received signal may become saturated during amplification. In this regard, by amplifying the amplitude value based on the saturation suppression information, it is possible to more reliably prevent saturation of the amplitude value of the received signal.

[0013] In the radar device, it is preferable that the saturation suppression information generating unit generates the saturation suppression information based on a plurality of the received signals including the most recently received received signal.

[0014] As a result, accurate saturation suppression information can be generated by generating saturation suppression information based on the plurality of received signals, and therefore saturation of the amplitude value of the received signal can be prevented more reliably.

[0015] The radar device preferably has the following configuration: the radar device includes an interference removal unit that removes interference contained in the received signal, and the amplitude value detection unit detects the amplitude value of the received signal from which interference has been removed by the interference removal unit.

[0016] Since the transmission signals of other radar devices have large amplitude values, generating saturation suppression information based on these large amplitude values ​​would result in unnecessary adjustment of the amplitude value of the received signal. In this regard, by adjusting the amplitude value of the received signal after removing interference as described above, it is possible to avoid unnecessary adjustment of the amplitude value of the received signal.

[0017] In the radar device, it is preferable that the saturation suppression information generation unit determines whether the amplitude value detected by the amplitude value detection unit exceeds a predetermined threshold, and generates the saturation suppression information so as to suppress the magnitude of the amplitude value of the portion exceeding the threshold.

[0018] This makes it possible to suppress the amplitude value only in the portion where there is a possibility of saturation, for example, and therefore to prevent the amplitude value of the received signal from decreasing overall.

[0019] The radar device preferably includes a pulse compression unit that compresses the pulse width of the received signal.

[0020] As a result, the pulse width cannot be appropriately compressed in the region where the amplitude value of the received signal is saturated, and therefore, in a radar device equipped with a pulse compression unit, the effect of the present invention, in which the amplitude value of the received signal is less likely to saturate, can be more effectively utilized.

[0021] The radar device preferably has the following configuration: the radar device includes a noise removal information generator that generates noise removal information, which is information for removing noise and describes an adjustment amount of the amplitude value according to the distance from the radar device itself. The amplitude value of the received signal is adjusted based on the noise removal information in addition to the saturation suppression information.

[0022] This makes it possible to remove noise (such as sea surface clutter) that is dependent on the distance from the aircraft when such noise exists.

[0023] According to a second aspect of the present invention, there is provided a signal processing method for receiving as a received signal a reflected wave of a transmission signal transmitted to the outside and processing the signal. Specifically, this signal processing method includes an amplitude value detection step, a saturation suppression information generation step, and an adjustment step. In the amplitude value detection step, the amplitude value of the received signal is detected. In the saturation suppression information generation step, saturation suppression information is generated based on at least the amplitude value of the received signal received immediately before, the information indicating an amount of adjustment of the amplitude value according to the distance from the own device and being information for preventing saturation of the amplitude value of the received signal. In the adjustment step, the amplitude value of the received signal is adjusted using the saturation suppression information generated in the saturation suppression information generation step.

[0024] This prevents the amplitude value of the received signal from saturating (exceeding the upper limit.) Therefore, even if a large target exists at a long distance, for example, the accurate amplitude value of the received signal indicating the target can be determined. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a block diagram of a radar device according to an embodiment of the present invention; [Figure 2] 10 is a graph showing the amplitude value of a received signal before the amplitude value is adjusted (before amplification) at the Nth time. [Figure 3] 10 is a graph showing noise removal information. [Figure 4] This is a graph obtained by correcting the Nth received signal based on noise removal information. [Figure 5] 10 is a graph showing saturation suppression information obtained based on the Nth received signal. [Figure 6] A graph combining saturation suppression information and noise removal information. [Figure 7] This graph is obtained by correcting the (N+1)th received signal based on noise removal information and saturation suppression information. DETAILED DESCRIPTION OF THE INVENTION

[0026] Next, a radar device 1 according to this embodiment will be described with reference to the drawings.

[0027] The radar device 1 includes a radar antenna 11. The radar antenna 11 is configured to transmit microwaves as transmission signals and to receive reflected waves from surrounding targets. The radar antenna 11 repeatedly transmits and receives microwaves while rotating within a horizontal plane.

[0028] The radar device 1 obtains the distance to the target based on the time difference between when the radar antenna 11 transmits the transmission signal and when it receives the reflected wave. The radar device 1 also obtains the direction in which the target is located based on the orientation of the radar antenna 11 when it transmits the transmission signal. This allows the radar device 1 to detect targets around the ship.

[0029] The radar device 1 also includes a transmission signal generator 21, a local oscillator 22, a transmitter 23, and a transmission / reception switch 24 as components for generating and outputting a transmission signal.

[0030] The transmission signal generating unit 21 generates a transmission signal with a predetermined waveform. In this embodiment, the transmission signal generating unit 21 generates a transmission signal with a long pulse width, but it may also generate a transmission signal with a short pulse width (in other words, a transmission signal that does not require subsequent processing to compress the pulse width).

[0031] The local oscillator 22 generates a local oscillator signal for converting the transmission signal generated by the transmission signal generation unit 21 into a predetermined band. The transmitter 23 converts the transmission signal generated by the transmission signal generation unit 21 based on the local oscillator signal, and outputs the converted transmission signal to the transmit / receive switch 24.

[0032] The transmission / reception switch 24 is configured to be able to switch between transmitting a transmission signal and receiving a reception signal. Specifically, when transmitting a transmission signal to the outside, the transmission / reception switch 24 outputs the transmission signal output by the transmitter 23 to the radar antenna 11. On the other hand, when receiving a reception signal, the transmission / reception switch 24 outputs the reception signal received by the radar antenna 11 to the receiver 25.

[0033] The receiving unit 25 includes a signal amplifier (adjustment unit) 25a, a frequency converter 25b, and an A / D converter 25c. The signal amplifier 25a is composed of an amplifier and the like, and amplifies the input received signal. When amplifying the received signal, the signal amplifier 25a adjusts the degree of amplification of the amplitude value depending on the distance from the own device; the specific process of adjusting the amplitude value will be described later. The frequency converter 25b converts the received signal to a baseband using a local oscillator signal generated by the local oscillator 22. The A / D converter 25c converts the received signal from an analog signal to a digital signal.

[0034] The received signal amplified and converted by the receiver 25 is input to the interference remover 26. The interference remover 26 detects and removes transmission signals of other radar devices from the signals included in the received signal.

[0035] The received signal from which interference has been removed by the interference remover 26 is input to the pulse compressor 27. The pulse compressor 27 compresses the pulse width of the received signal by using a matched filter or the like that restores the modulation that the transmission signal generator 21 applied to the transmission signal.

[0036] The received signal, whose pulse width has been compressed by the pulse compressor 27, is input to the radar image generator 28. The radar image generator 28 generates a radar image based on the input received signal by converting the received signal from a polar coordinate system into a Cartesian coordinate system, etc. The radar image generated by the radar image generator 28 is displayed on a display device 41 equipped with a liquid crystal display or the like.

[0037] It should be noted that the radar device 1 described above is an example, and it is possible to omit some of the signal processing, add other signal processing, or change the order of signal processing.

[0038] Next, a process for adjusting the amplitude value of a received signal when the signal amplifier 25a performs amplification will be described with reference to Figures 1 to 7. As shown in Figure 1, the radar device 1 includes an amplitude value detector 31, a noise removal information generator 32, a saturation suppression information generator 33, and an adjustment information storage unit 34.

[0039] The amplitude value detector 31 detects the amplitude value of the received signal from which the transmission signals of other radar devices have been removed by the interference remover 26. Specifically, every time the amplitude value detector 31 receives a received signal, it detects the amplitude value of the received signal (more specifically, the amplitude value associated with the distance from the radar device itself).

[0040] The noise removal information generator 32 generates noise removal information for removing noise (especially sea surface clutter) contained in the received signal. The noise removal information indicates an adjustment amount according to the distance from the aircraft. While any method for generating noise removal information is possible, in this embodiment, the noise removal information is generated by the user inputting one or more setting values. Therefore, the noise removal information remains constant unless the user changes the setting values.

[0041] The noise removal information may be generated based on one or more received signals. In this case, the amplitude value of the received signal is obtained from the amplitude value detector 31, and the noise removal information is generated based on the amplitude value of the received signal. In this case, new noise removal information may be generated every time a received signal is received, and the information may be automatically updated.

[0042] Figure 2 is a graph showing the amplitude value of the received signal before the amplitude value is adjusted. This graph shows the information obtained from one reception of the received signal. The horizontal axis of this graph is the distance (i.e., the time it takes to receive the received signal), and the vertical axis is the amplitude value (signal level). As shown in Figure 2, the amplitude value of the received signal is larger in areas where targets exist compared to other areas. Furthermore, due to the effects of sea surface clutter, etc., the amplitude value of the received signal decreases as the distance from the aircraft increases.

[0043] The noise removal information is information generated mainly to remove the effects of sea clutter. FIG. 3 is a graph (noise removal curve) showing the noise removal information. The horizontal axis represents the distance from the own aircraft, and the vertical axis represents the adjustment amount corresponding to that distance. The greater the adjustment amount of the received signal, the greater the degree to which the amplitude value is reduced (in other words, the smaller the amplification amount, the lower the sensitivity, and the suppression of the amplitude value). As described above, the amplitude value of the received signal tends to decrease as the distance from the own aircraft increases, so the adjustment amount of the noise removal information in FIG. 3 decreases as the distance from the own aircraft increases. The noise removal information generated by the noise removal information generation unit 32 is stored in the adjustment information storage unit 34.

[0044] The received signal shown in Figure 4 is obtained by amplifying the received signal in Figure 2 based on the noise removal information in Figure 3 and correcting the amplitude value. By performing correction based on the noise removal information, it is possible to suppress changes in the amplitude value according to the distance from the own aircraft.

[0045] The saturation suppression information generator 33 generates saturation suppression information based on the amplitude value detected by the amplitude value detector 31. The saturation suppression information is information for preventing the amplitude value of the received signal from saturating (exceeding the upper limit and making it impossible to detect a specific value), and indicates an adjustment amount according to the distance from the own device. The saturation suppression information is newly generated each time a received signal is received. When the amplitude value of the received signal exceeds a predetermined threshold, the saturation suppression information generator 33 sets an adjustment amount for the amplitude value for that portion.

[0046] In the graph shown in FIG. 4, multiple targets appear. By performing noise removal processing, the farther a target is from the aircraft, the greater the amount of amplification of the amplitude value. Therefore, if a large target exists at a long distance, the amplitude value of the portion representing that target is likely to be large. Therefore, in the example shown in FIG. 4, the amplitude value of target C, which is located the farthest, is large. Furthermore, as shown in FIG. 4, the portion representing target C exceeds the threshold, so the saturation suppression information generator 33 generates saturation suppression information so as to suppress the amount of amplification of the amplitude value of that portion.

[0047] In this manner, in this embodiment, the amplitude value of the received signal is adjusted for a portion where the amplitude value of the received signal exceeds the threshold. Therefore, if the received signal includes a transmission signal from another radar device, the amplitude value of this portion may also be adjusted because the transmission signal from the other radar device has a large amplitude value. In this regard, in this embodiment, saturation suppression information is generated based on the received signal after the interference remover 26 has removed the transmission signal from the other radar device, thereby preventing unnecessary suppression of the amplitude value of the received signal.

[0048] Fig. 5 is a graph (saturation suppression curve) showing saturation suppression information generated based on the received signal of Fig. 4. As shown in this graph, for the portion exceeding the threshold (the portion indicating target C), the amount of adjustment of the amplitude value is large (in other words, the amount of amplification is small, the sensitivity is lowered, and the amplitude value is suppressed). The saturation suppression information generated by the saturation suppression information generation unit 33 is stored in the adjustment information storage unit 34. Every time the saturation suppression information generation unit 33 receives a received signal, it generates new saturation suppression information and updates the saturation suppression information stored in the adjustment information storage unit 34.

[0049] The adjustment information storage unit 34 stores the noise removal information generated by the noise removal information generation unit 32 and the saturation suppression information generated by the saturation suppression information generation unit 33. Furthermore, the adjustment information storage unit 34 outputs the noise removal information and the saturation suppression information to the signal amplifier 25a before the signal amplifier 25a amplifies the received signal. Note that the saturation suppression information generated by the saturation suppression information generation unit 33 based on the Nth received signal is used when the signal amplifier 25a amplifies the next (N+1th) received signal.

[0050] The adjustment information storage unit 34 can generate saturation suppression information using various methods based on the amplitude value of the received signal. For example, in this embodiment, saturation suppression information is generated based only on the most recently received signal, but saturation suppression information may also be generated based on multiple received signals including the most recently received signal. For example, saturation suppression information may be generated based on the most recently received signal and the signal immediately before, or based on the most recently received signal and the signal one cycle before that received in the same direction. Note that when saturation suppression information is generated based on multiple received signals, weighting may be performed to increase the influence of the most recently received signal.

[0051] In this embodiment, the adjustment amount is set to a larger amount as the amount exceeding the threshold increases, but the same adjustment amount may be set for the area where the threshold is exceeded. Alternatively, multiple thresholds may be provided, and the adjustment amount may be set depending on which threshold is exceeded and which threshold is not exceeded.

[0052] The graph shown in Fig. 6 is a graph (amplitude value adjustment curve) that combines noise removal information and saturation suppression information (N+1th time). Signal amplifier 25a amplifies the received signal using the graph shown in Fig. 6. As described above, the greater the amount of adjustment of the amplitude value, the greater the degree to which the amplitude value is reduced (in other words, the smaller the amount of amplification).

[0053] The graph shown in Figure 7 shows the result of adjusting the amplitude value of the received signal using the graph shown in Figure 6. In the graph shown in Figure 7, the magnitude of the amplitude value according to the distance from the aircraft (the influence of sea surface clutter) is reduced, and the amplitude value in the part where the amplitude value may become saturated (the part showing target C) is suppressed.

[0054] As described above, the radar device 1 of this embodiment includes an amplitude value detector 31, a saturation suppression information generator 33, and a signal amplifier 25a. The amplitude value detector 31 detects the amplitude value of the received signal. The saturation suppression information generator 33 generates saturation suppression information, which indicates the amount of adjustment of the amplitude value according to the distance from the radar device itself and is information for preventing saturation of the amplitude value of the received signal, based on at least the amplitude value of the most recently received received signal. The signal amplifier 25a adjusts the amplitude value of the received signal using the saturation suppression information generated by the saturation suppression information generator.

[0055] This prevents the amplitude value of the received signal from saturating (exceeding the upper limit), and therefore, even for a large target (target C) located at a long distance, the amplitude value can be prevented from saturating and an accurate amplitude value can be detected.

[0056] The preferred embodiment of the present invention has been described above, but the above configuration can be modified, for example, as follows.

[0057] In the above embodiment, the removal of noise such as sea surface clutter and the adjustment of amplitude values ​​to prevent saturation are performed simultaneously, but it is also possible to perform one of the processes before the other.

[0058] In the above embodiment, the noise removal unit is configured to remove sea clutter, but it may be configured to perform other noise removal processes instead of or in addition to removing sea clutter. Examples of other noise removal processes include removing rain and snow clutter and scan correlation.

[0059] In the above embodiment, signal amplifier 25a also functions as the adjustment unit of the present invention, but an independent adjustment unit may be provided separately from signal amplifier 25a, or a different device may have the function of the adjustment unit. However, since the amplitude value is adjusted after amplification by signal amplifier 25a, there is a possibility that the amplitude value of the received signal may become saturated during amplification by signal amplifier 25a. Taking this into consideration, it is preferable that signal amplifier 25a adjusts the amplitude value.

[0060] In the above embodiment, a radar device mounted on a ship has been described as an example, but the present invention can also be applied to radar devices mounted on other moving bodies (for example, aircraft).The present invention can also be applied to radar devices installed in lighthouses, straits, harbors, etc., which detect the surrounding conditions by transmitting and receiving microwaves. [Explanation of symbols]

[0061] 1. Radar equipment 23 Transmitter 25 Receiving unit 25a Signal amplifier (adjustment section) 31 Amplitude value detection unit 32 Noise removal information generation unit 33 Saturation suppression information generation unit 34 Adjustment information storage section

Claims

1. A radar device that transmits a transmission signal to an external device and receives a reflected wave of the transmission signal as a received signal, an amplitude value detection unit that detects the amplitude value of the received signal; a saturation suppression information generating unit that generates saturation suppression information, which is information indicating an adjustment amount of the amplitude value according to the distance from the own device, based on at least the amplitude value of the received signal received immediately before, and is information for preventing the amplitude value of the received signal from becoming saturated; an adjustment unit that adjusts an amplitude value of the received signal using the saturation suppression information generated by the saturation suppression information generation unit; A radar device comprising:

2. The radar device according to claim 1, The radar device is characterized in that the adjustment unit constitutes a part of a receiving unit that receives the received signal, and performs processing to amplify an amplitude value of the received signal based on the saturation suppression information.

3. The radar device according to claim 1, The radar device is characterized in that the saturation suppression information generating unit generates the saturation suppression information based on a plurality of the received signals including the received signal received immediately before.

4. The radar device according to claim 1, an interference canceller for canceling interference contained in the received signal; The radar device is characterized in that the amplitude value detection unit detects the amplitude value of the received signal from which interference has been removed by the interference removal unit.

5. The radar device according to claim 1, The saturation suppression information generating unit determines whether the amplitude value detected by the amplitude value detecting unit exceeds a predetermined threshold, and generates the saturation suppression information so as to suppress the magnitude of the amplitude value of the portion exceeding the threshold.

6. The radar device according to claim 1, A radar device comprising a pulse compression unit that compresses the pulse width of the received signal.

7. The radar device according to any one of claims 1 to 6, a noise removal information generating unit that generates noise removal information, the noise removal information being information describing an adjustment amount of an amplitude value according to a distance from the own device; The radar device is characterized in that the amplitude value of the received signal is adjusted based on the noise removal information in addition to the saturation suppression information.

8. A signal processing method for receiving a reflected wave of a transmission signal transmitted to the outside as a received signal and processing the signal, comprising: an amplitude value detection step of detecting an amplitude value of the received signal; a saturation suppression information generating step of generating saturation suppression information, which is information indicating an adjustment amount of the amplitude value according to the distance from the own device, based on at least the amplitude value of the received signal received immediately before, and which is information for preventing the amplitude value of the received signal from becoming saturated; an adjusting step of adjusting an amplitude value of the received signal using the saturation suppression information generated in the saturation suppression information generating step; A signal processing method comprising:

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