JP5853547B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus that detects a target position and velocity by irradiating a modulated radio wave signal to a space. In particular, the present invention relates to a technique for avoiding interference with an interference signal source and effectively operating the radar apparatus when a strong interference signal source is disposed in the vicinity.

  When a radar is mounted on a narrow platform such as a vehicle, an aircraft, or a ship, interference with radio wave equipment such as a communication device, an ECM device, and another radar device becomes a problem. Conventionally, with respect to interference between these radio wave devices, countermeasures have been taken such as devising the arrangement of antennas, and in the case of radars, making the pulse transmission period different for each radar device. For example, as the latter example, there is a method as in Patent Document 1.

JP 2010-25944 (page 1-17, FIG. 1)

  In the method disclosed in Patent Document 1, the frequency of occurrence of interference is reduced by making the pulse transmission interval (period) PRI different for each on-vehicle radar device. In addition, the FMCW radar and the frequency CW radar, which are low-price and simple methods, are adopted, and the size can be reduced. However, even if the pulse transmission period is varied, it is clear that there is asynchronous interference between the radars, and it can be easily imagined that the detection performance deteriorates. Further, when the interference signal source is a device that transmits a non-periodic signal, such as a communication device or an ECM device, there is a problem that interference countermeasures based on such radar cannot be implemented.

  The present invention is for solving such problems, and there is no interference signal source even when a strong interference signal source such as a communication device, an ECM device, or another radar device is disposed in the vicinity. The purpose is to obtain the same radar performance as the case.

The radar apparatus according to the present invention is a radar apparatus that operates based on a control signal output from a control unit that controls an operation of the interference signal source, in which an interference signal source that transmits intermittent interference signals is disposed in the vicinity. A chirp modulation generation unit for generating a chirp modulation signal according to the control signal, a transmission timing controller for controlling a timing for transmitting the chirp modulation signal according to the control signal, and a transmission antenna for radiating the chirp modulation signal; A reception antenna that receives reflected signals from multiple targets located at different distances, a reception timing controller that controls reception timing according to the control signal and outputs a reception signal, and the chirp modulation signal is mixed with the reception signal A reception signal processing unit that calculates the distance of each target from the difference frequency of the transmitted and received transmission signals, the transmission The imming controller receives the stop timing information of the interference signal from the control unit, transmits the chirp modulation signal having a transmission time length set in advance before the stop timing, and the reception timing controller The reflection signal from the plurality of targets is received within the stop period at the same time as the stop timing, and the frequency change rate of the chirp signal is shorter than the time length corresponding to the maximum detection distance assumed by the transmission time length. By changing the time length from the transmission start timing of the transmission signal to the reception period start timing for each pulse hit, the time length is larger than the time corresponding to the assumed maximum detection distance. Use to detect targets in different distance ranges .

According to the present invention, an effect that for the signal processing by using the received signal of only nonexistent time interference signal, the influence of the interference signal can be suppressed to a minimum. In addition, a desired distance resolution can be obtained when receiving a target signal in a necessary distance range.

It is a block diagram showing the whole structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a time chart showing control operation of the radar apparatus concerning Embodiment 1 of this invention. It is a time chart showing control operation of the radar apparatus concerning Embodiment 2 of this invention. It is a time chart showing control operation concerning a conventional pulse radar device.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the overall configuration of a radar apparatus according to Embodiment 1 of the present invention. The chirp modulation signal generation unit 1 includes a sawtooth wave generator 2 and a voltage controlled oscillator 3, and generates a chirp modulation signal 102 by inputting the sawtooth wave 101 to the voltage controlled oscillator 3. The generated chirp modulation signal 102 is radiated as a transmission signal 103 from the transmission antenna 5 through the transmission timing controller 4. The transmission signal 103 is reflected by the target 6 to become the target reflection signal 104 and is received by the reception antenna 7 as the reception signal 105. In general, the received signal 105 is the sum of the reflected signals 104 from multiple targets at different distances.

The reception signal 105 is input to the reception signal processing unit 9 through the reception timing controller 8.
Inside the reception signal processing unit 9, the frequency converter 10 mixes the chirp modulation signal 102 with the reception signal 105 to obtain a signal 106 having a transmission / reception differential frequency. Since the transmission signal is chirp modulated, the transmission / reception differential frequency is a frequency corresponding to the delay time, that is, the distance to the target. That is, in this radar, distance information is obtained as a difference frequency of transmission / reception. The transmission / reception differential frequency signal 106 is converted into a digital signal 107 by the A / D converter 11 and stored in the memory 12. The signal 108 stored for one hit is processed by the FFT processor 13 to become target distance information 109, and the distance information to the target is displayed on the display device 14.

  The chirp modulation signal generation unit 1 may be configured by a DDS (Direct Digital Synthesizer) or the like. Further, the reception signal processing unit 9 may generate a chirp modulation signal similar to the transmission signal internally, and in that case, the reception signal processing unit 9 may be configured by digital signal processing including the frequency converter 10. The transmission timing controller 4, the reception timing controller 8, and the chirp modulation signal generator 1 are controlled by a control signal 110 from the control unit 15. The control unit 15 receives the transmission timing information 111 of the interference signal from the interference signal source 16, and determines the transmission timing and reception timing of the radar and the start timing of chirp modulation.

Since this transmission / reception timing and chirp modulation control method has the features of the present invention, these control methods will be described below. For comparison, first, problems of a normal pulse radar will be described with reference to FIG. In the figure, the vertical axis of (A) is a radar transmission signal, the vertical axis of (B) is a radar reception period, the vertical axis of (C) is a radar reception signal, and the vertical axis of (D) is an interference signal. The horizontal axis of the figure shows time. A normal pulse radar provides a reception period 42 having a length corresponding to a delay time of a reflected wave from an assumed maximum detection distance after transmitting a pulse-shaped transmission signal 41, and within a reception period from the target. The target reflected signals 43a and 43b that are reflected waves are received.
Since the delay time from the transmission of the transmission signal 41 to the reception of the target reflection signals 43a and 43b depends on the distance to the target, this delay time is measured to determine the distance to the target.

  Here, consider a case where an interference signal source in the same frequency band as the radar is present in the vicinity of the radar. When the interference signal 44 shown in FIG. 4D is transmitted within the reception period 42, the target reflected signals 43a and 43b overlapping with the interference signal 44 cannot be received, and within a distance corresponding to the time when the interference signal exists ( There is a problem that the target of the (interference period) cannot be detected. When the interference signal is an intermittent signal that is not synchronized with the pulse repetition period of the radar, such as the interference signal 44 shown in the figure, by repeatedly observing at a plurality of pulse repetition periods, within one pulse repetition period. In general, a method of compensating for a target reflected signal at a distance that could not be received is performed.

  However, when the duty ratio of the interference signal increases, there is a problem that the number of target reflected signals that are lost increases and the radar performance deteriorates. FIG. 2 shows a time chart representing the control operation of the radar apparatus in the present embodiment for solving this. In the figure, the vertical axis of (A) is the interference signal, the vertical axis of (B) is the radar transmission signal, the vertical axis of (C) is the chirp modulation signal frequency, the vertical axis of (D) is the radar reception period, and (E) , The vertical axis of (F) indicates the transmission / reception differential frequency, and the horizontal axis of each figure indicates time.

  In the present embodiment, as shown in FIG. 2, the control unit obtains the timing 201 at which the interference signal 21 stops from the interference signal transmission timing information 111 from the interference signal source 16. Next, the transmission timing controller 4 follows the control signal from the control unit, and the radar transmission signal having a length corresponding to the maximum detection distance from the timing 202 preceding the interference signal stop timing 201 by a time corresponding to the maximum detection distance. 22 is transmitted. The chirp modulation signal frequency 23a is changed linearly with time from the start of radar signal transmission 202, and so-called linear chirp modulation is performed. The frequency change direction of the chirp modulation may be up-chirp or down-chirp.

The reception period 24 is a period during which the interference signal 21 is stopped between the stop timing 201 of the interference signal 21 and the transmission signal length (a period 203 equivalent to the maximum detection distance).
Since the length of the transmission signal is as long as the maximum detection distance, the reception signal is generally a superposition of the reception signals 25a and 25b from a plurality of targets, but since the transmission signal is chirp modulated, the frequency in the reception period Is a frequency according to the distance, such as 26a and 26b. Therefore, distance information can be obtained as a frequency difference, such as 27a and 27b, by taking a difference from the transmission frequency in the reception signal processing unit. A series of the flow of the transmission signal, the chirp modulation signal frequency, and the reception period described above is defined as one pulse hit period, and the next pulse hit period starts before the period corresponding to the maximum detection distance from the stop timing of the next interference signal, and is repeated.

  The control unit 15 determines transmission timing information to be sent to the radar apparatus as follows. When the interference signal source 16 is a radar, the information of the timing 201 at which the interference signal stops can be predicted from the timing at which the previous pulse was transmitted and the pulse repetition cycle. Can be predicted from information on time slots used by the communication apparatus. Further, in the case of an interference signal source whose transmission timing can be controlled by itself, a transmission schedule itself determined by itself may be used.

As described above, according to the present embodiment, the timing at which the interference signal stops is received from the control unit, and a transmission signal having a length corresponding to the maximum detection distance is transmitted before that. It is possible to receive reflected signals from a plurality of targets existing within a distance, and there is an effect that a target reflected signal is not lost, which has been a problem with conventional radars.
In addition, since the distance information to the target is obtained from the transmission / reception differential frequency, the necessary reception period does not depend on the maximum detection distance, and the reception period can be shortened. Further, since the pulse modulation method is a low-priced and simple method, it can be downsized. Furthermore, since signal processing is performed using the received signal only during a time period in which no interference signal exists, the interference with the interference signal source can be reduced, and the deterioration of the radar performance can be minimized.

Embodiment 2. FIG.
In the first embodiment, a transmission signal having a length corresponding to the maximum detection distance is transmitted after being subjected to chirp modulation. When a sufficient frequency bandwidth cannot be used from the viewpoint of radio law or cost, the frequency of chirp modulation is used. There is a possibility that the rate of change cannot be increased, and the frequency difference between target signals having different distances is reduced, resulting in degradation of distance resolution. This embodiment is for dealing with such a problem. Since the hardware configuration is the same as that of the first embodiment, description thereof is omitted.

  In this embodiment, in order to increase the frequency change rate of chirp modulation with a limited frequency bandwidth, the transmission signal length is shortened. However, if the transmission signal length is shortened, only a target having a narrower distance range can be detected. Therefore, multiple pulse hits are divided into long-distance and short-distance, and long-distance pulse hits receive a long-distance target signal with a wide interval between transmission timing and reception timing. Then, the target signal in the short distance is received by narrowing the interval between the transmission timing and the reception timing, and the target signal from the short distance to the maximum detection distance is received by synthesizing the target signal received between the two pulse hits. .

  FIG. 3 shows a time chart of the present embodiment. In the figure, the vertical axis of (A) is the interference signal, the vertical axis of (B) is the radar transmission signal, the vertical axis of (C) is the chirp modulation signal frequency, the vertical axis of (D) is the radar reception period, and (E) , The vertical axis of (F) indicates the transmission / reception differential frequency, and the horizontal axis of each figure indicates time. As in the first embodiment, the control unit first obtains the timing 201 at which the interference signal 21 stops from the interference signal transmission timing information 111 from the interference signal source 16. Next, according to the control signal from the control unit, the transmission timing controller 4 sets a timing 302 corresponding to the maximum detection distance before the interference signal stop prediction timing 301 as the transmission signal start timing in the long distance pulse hit, From that timing, a radar transmission signal 32a having a length corresponding to one half of the maximum detection distance is transmitted.

  The chirp modulation signal frequency 33a starts linear chirp modulation from the radar signal transmission start 302. However, since the transmission signal length is one-half that of the first embodiment, the frequency change rate is doubled. In addition, since there is a period corresponding to a half of the maximum detection distance from the end of transmission of the transmission signal 32a to the start of the reception period 34, the frequency change is stopped during this period, and reception starts from timing 301 when the reception period starts. The modulation of the chirp modulation signal frequency 33b for signal processing is started. The reception period 34a is a period during which the interference signal 31 is stopped from the stop timing 301 of the interference signal 31 to a period 303 equal to the transmission signal length (corresponding to a half of the maximum detection distance).

  During this reception period, only the long-distance target signal 35b whose distance is from half the maximum detection distance to the maximum detection distance can be received, and the short-distance target signal whose distance is half or less of the maximum detection distance. 35a cannot be received. Therefore, at the time of the next short-distance pulse hit, the interval between the interference signal stop prediction timing 304 and the transmission signal start timing 305 is set to one half of the maximum detection distance, and the transmission signal 32b is transmitted during that period.

  The chirp modulation signal frequency 33c starts chirp modulation immediately after the transmission start 305, and in this pulse hit, the reception period 34b starts immediately after the transmission signal stop timing 304. Therefore, the same frequency change rate continues from the transmission signal stop timing 304. Then, the chirp modulation signal frequency 33d is changed and used for reception signal processing. Since the reception period 34b starts immediately from the transmission signal stop timing 304, the long-distance target signal 35d cannot be received, but the short-distance target signal 35c can be received. A plurality of target reflected signals from the maximum detection distance to the maximum detection distance can be received.

  As described above, in the present embodiment, the period from the short distance to the maximum detection distance is received by dividing it into two pulse hits, and the transmission signal length is shortened by a half so that transmission / reception with the same frequency bandwidth is performed. Since the frequency change rate of the chirp modulation can be doubled using the signal processing system, there is an effect that the distance resolution obtained as the frequency difference can be doubled. Similarly, if the period from the short distance to the maximum detection distance is received by dividing it into 1/3 pulse hits and the frequency change rate of the chirp modulation signal is tripled, transmission / reception of the same frequency bandwidth is performed. Three times the distance resolution can be obtained using the signal processing system. Similarly, the desired distance resolution can be obtained by dividing into more pulse hits.

DESCRIPTION OF SYMBOLS 1 Chirp modulation signal generation part 2 Saw wave generator 3 Voltage control oscillator 4 Transmission timing controller 5 Transmission antenna 6 Target 7 Reception antenna 8 Reception timing controller 9 Reception signal processing part 10 Frequency converter 11 A / D converter 12 Memory 13 FFT processor 14 Display device 15 Control unit 16 Interference signal source 21 Interference signal 22 Transmission signal 23a Transmission signal chirp modulation signal frequency 23b Reception signal processing chirp modulation signal frequency 24 Reception period 25a Short-range target reflected signal 25b Long-distance Target reflection signal 26a Short-range target reflection signal frequency 26b Long-range target reflection signal frequency 27a Short-range target reflection signal transmission / reception differential frequency 27b Long-distance target reflection signal transmission / reception differential frequency 31 Interference signal 32a Long-distance pulse Transmission signal 32b at the time of hit Signal 33a Transmission signal chirp modulation signal frequency 33b at long distance pulse hit Reception signal processing chirp modulation signal frequency 33c at long distance pulse hit Transmission signal chirp modulation signal frequency 33d at short distance pulse hit Received signal processing chirp modulation signal frequency 34a for distance pulse hit Reception period 34b for long distance pulse hit Reception period 35a for short distance pulse hit Short target reflection signal 35b for long distance pulse hit Reflection signal 35c of a long distance target at the time of a distance pulse hit Reflection signal 35d of a short distance target at the time of a short distance pulse hit Reflection signal 36a of a long distance target at the time of a short distance pulse hit Short distance at the time of a long distance pulse hit Target reflected signal frequency 36b Reflected signal frequency 36c of a long-distance target when a long-distance pulse hit occurs Reflection signal frequency 36d for the short distance target at the time of the distance pulse hit Reflection signal frequency 37a of the long distance target at the time of the short distance pulse hit Transmission / reception differential frequency 37b of the reflection signal of the long distance target at the time of the long distance pulse hit Transmission / reception differential frequency 41 of the reflection signal of the short distance target at the time of the pulse hit Transmission signal 42 of the conventional radar Reception period 43a of the conventional radar Target reflection signal 43b from the short distance target Target reflection signal 44 from the long distance target Interference signal 101 Saw wave 102 Chirp modulation signal 103 Transmission signal 104 Target reflection signal 105 Reception signal 106 Transmission / reception differential frequency signal 107 Transmission / reception differential frequency digital signal 108 Transmission / reception differential frequency signal 109 for one hit Target distance information 110 Control signal 111 Interference signal transmission timing information 201 Interference signal stop timing 202 Signal start timing 203 Timing after time equal to transmission signal length from reception period start timing 301 Interference signal stop timing at long distance pulse hit 302 Transmission signal start timing at long distance pulse hit 303 Long distance pulse hit Timing 304 after the reception period start timing is equal to the transmission signal length 304 Interference signal stop timing 305 when the short distance pulse hit transmission signal start timing 306 when the short distance pulse hit Reception period start timing when the short distance pulse hit Timing after the time equal to the transmission signal length from

Claims (1)

An interference signal source that transmits intermittent interference signals in the vicinity is disposed, and is a radar device that operates based on a control signal output from a control unit that controls the operation of the interference signal source,
A chirp modulation generation unit for generating a chirp modulation signal according to the control signal;
A transmission timing controller for controlling the timing of transmitting the chirp modulation signal according to the control signal;
A transmitting antenna that radiates the chirp modulated signal;
A receiving antenna for receiving reflected signals from a plurality of targets located at different distances;
A reception timing controller for controlling a reception timing according to the control signal and outputting a reception signal;
A reception signal processing unit that calculates a distance of each target from a differential frequency of a transmission / reception signal obtained by mixing the chirp modulation signal with the reception signal;
The transmission timing controller receives the interference signal stop timing information from the control unit, and transmits the chirp modulation signal having a transmission time length set in advance before the stop timing;
The reception timing controller receives reflected signals from the plurality of targets within the stop period simultaneously with the stop timing of the interference signal ,
The transmission time length is shorter than the time length corresponding to the assumed maximum detection distance, and the frequency change rate of the chirp signal is set larger than the case where the transmission time length is the time corresponding to the assumed maximum detection distance. A radar apparatus characterized by detecting a target in a different distance range using a plurality of pulse hits by changing a time length from a signal transmission start timing to a reception period start timing for each pulse hit .

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