JP2014159975A - Radar device and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar device capable of detecting a relative speed of an object with a preferred speed resolution and shortening processing time, by changing the number of FFT (Fast Fourier Transform) points on the basis of a distance to the object, and a method for controlling the same.SOLUTION: A radar device sets the number of integrated values used for FFT processing or the number of FFT points, for each distance gate. Therefore, The number Nfi of FFT points is input for each distance gate in a step S6, and, when the number of current FFT points is equal to the number Nfi of FFT points of the distance gate (step S7), FFT processing is performed in a step S8. The number Nfi of FFT points of a distance gate corresponding to a distant side in a detection range is set to be less than the number of FFT points of a near distance gate.

Description

  The present invention relates to a radar apparatus, and more particularly to an in-vehicle radar apparatus that is mounted on a vehicle and detects at least the position and relative speed of an object.

  A radar device that detects a target object and obtains target information such as its position and relative speed by radiating a pulse signal as a radiated radio wave and receiving and processing a reflected wave reflected by the target object is known. ing. Such a radar apparatus is mounted on a vehicle, for example, and is used for safe driving support or the like.

In order to detect the relative velocity of an object in a radar apparatus, a fast Fourier transform (FFT) that analyzes a frequency component of a reflected wave has been widely used. When the relative velocity of the object is V [m / s], the frequency of the radio wave radiated from the radar device (carrier frequency) is f0, and the speed of light is c [m / s], reflection from the object by the Doppler effect. A frequency fluctuation (Doppler frequency) fd given by the following equation is generated in the wave.
fd = 2 × (V / c) × f0 (1)
Accordingly, the relative velocity V of the object is given by the following equation.
V = fd × c / (2 × f0) (2)

  The Doppler frequency fd is obtained by FFT processing. Further, it is known that the velocity resolution of the relative velocity V of the object increases as the number of FFT points is increased by a power of two. As an example, in a conventional radar apparatus that receives reflected waves of a pulse signal output from a transmission antenna with two reception antennas provided on the left and right sides of a vehicle and detects a distance to a target object, a relative speed, and an azimuth angle, FIG. 7 shows a flow of processing for acquiring object information by FFT processing. FIG. 1 is a flowchart showing a schematic processing flow in a conventional radar apparatus. In the figure, when a period for detecting an object, that is, a period for detecting an object in a predetermined detection range is started (step S91), a pulse signal is output from the radar device at a predetermined pulse repetition period in step S92. The

  The pulse signal radiated into the air is reflected by the object and received by the two left and right receiving antennas of the radar apparatus. In step S93, a received signal is input from one of the two receiving antennas to obtain measurement data for each distance gate, and this is integrated for each distance gate. The processes in steps S92 and S93 are sequentially performed on the reception signals of the left and right receiving antennas. When the process of step S93 is completed, in step S94, it is determined whether the integration performed in step S93 has reached a predetermined number of integrations. If it is determined that the predetermined number of integrations has not been reached, the process returns to step S92 to output a radiated radio wave at the next pulse repetition period, and the integration for each distance gate in step S93 is repeated. On the other hand, when it is determined in step S94 that the predetermined number of integrations has been reached, the process proceeds to the next step S95.

  In step S95, it is determined whether or not the integral value has been acquired for a predetermined number of FFT points (hereinafter referred to as a prescribed number of FFT points) for the distance gate for which the integral value has been calculated. If it is determined that the prescribed number of FFT points has not been reached, the integral value obtained above is stored and the integral value of each distance gate is initialized, and then the processing of steps S92 to S94 is repeated to determine the next FFT point. Calculate the integral value. On the other hand, when it is determined in step S95 that the specified number of FFT points has been reached, the process proceeds to the next step S96, where FFT processing is performed using the integral value of the specified number of FFT points.

  In the next step S97, it is determined whether the equivalent sampling has reached a predetermined number of times. If it is determined that the predetermined equivalent sampling number has not been reached, an equivalent sampling process is performed in step S98 to select the next processing target distance gate. Then, the processes in steps S92 to S96 are repeated for the selected distance gate. On the other hand, when it is determined in step S97 that the predetermined equivalent sampling number has been reached, the object information on the position, relative speed, and azimuth of the object obtained by the series of processes is displayed on a predetermined display device or the like. To finish the processing of the object detection cycle.

In the processing of the conventional radar apparatus described with reference to FIG. 7, the pulse repetition period is, for example, 1 μs, the predetermined number of integrations for each distance gate is 32, the FFT point specified number is 64, and the predetermined equivalent sampling number is 16. When processing the signals received by the two left and right receiving antennas, the total processing time in one object detection cycle is:
1 μs × 32 × 64 × 16 × 2 = 65.536 ms
Thus, the time required to measure the entire area (all distance gate) (hereinafter referred to as the update rate) is about 70 ms.

For example, when the object moves at a relative speed of 40 m / s (144 km / h) for about 70 ms, the object is
40m / s x 70ms = 2.8m
Will move the distance. For example, if the number of FFT points is uniformly reduced in order to shorten the update rate, there arises a problem that the velocity resolution of the relative velocity V is uniformly reduced regardless of the distance to the object.

  Patent Document 1 describes a radar apparatus that determines the number of FFT points that satisfy the speed resolution and uses it for signal processing based on the operation mode, mode parameters, and speed resolution input from the sensor control unit. Further, it is described that the required speed resolution is changed according to the target tracking state.

JP 2009-192355 A

  In the conventional radar device described in Patent Document 1, the required speed resolution is determined according to the target tracking state, and the number of FFT points is determined based on the required speed resolution. All have the same number of FFT points. However, a high resolution is not necessarily required for an object located far away as the speed resolution. This is because a distant object has time to reach a collision even if it approaches at a high relative speed.

  However, in the conventional radar apparatus, since the number of FFT points is constant regardless of the distance to the object, the FFT processing is performed on a distant object with a speed resolution higher than necessary. On the other hand, if the number of FFT points is reduced, there is a problem in that the speed resolution is reduced to a short distance gate that requires high speed resolution. In addition, since it takes about the same processing time for each distance gate to acquire the measurement data, there is a problem that the processing time greatly increases when the number of FFT points is increased.

  The present invention has been made in view of the above problems, and by detecting the relative speed of an object with suitable speed resolution by changing the number of FFT points based on the distance to the object, the processing time is reduced. An object of the present invention is to provide a radar apparatus and a control method thereof that can be shortened.

  In order to solve the above-mentioned problem, a first aspect of the radar apparatus control method of the present invention radiates a radio wave a plurality of times at a predetermined repetition period for each object detection period, and enters a predetermined detection range for each radiated radio wave. A reflected wave reflected by a certain object is received, measurement data for each distance is acquired from the reflected wave, and an integrated value obtained by adding a predetermined number of integrations to a corresponding distance gate is acquired. As an integral value of the FFT points, a predetermined number of FFT points are acquired, and an FFT process is performed using the integral value of the FFT points, and at least a distance and a relative speed to the object are obtained using the result of the FFT process. A radar apparatus control method for detecting the number of FFT points, wherein the number of FFT points is set for each distance gate.

  Another aspect of the radar apparatus control method of the present invention is characterized in that the number of FFT points is set to be small with respect to the distance gate corresponding to a distant distance.

  According to another aspect of the radar apparatus control method of the present invention, when the distance gate corresponding to the far distance acquires the integral value of the small number of FFT points set, the repetition period is shortened to the far distance. The distance gates other than the distance gate corresponding to each distance acquire the integral value of the number of FFT points.

  Another aspect of the radar apparatus control method of the present invention is characterized in that the predetermined number of integrations is increased with respect to the distance gate in which the number of FFT points is set to be small.

  According to another aspect of the radar apparatus control method of the present invention, the number of FFT points set to a small number and the increased number of integrations are obtained by multiplying the number of FFT points and the predetermined number of integrations. It is characterized by being set to be less than the product.

  According to a first aspect of the radar apparatus of the present invention, a radio wave is radiated a plurality of times at a predetermined repetition period for each object detection period, and a reflected wave reflected by an object within a predetermined detection range is detected for each radiated radio wave. A radar apparatus that receives and acquires measurement data for each distance gate from the reflected wave, processes the measurement data with an arithmetic processing unit, and detects at least the distance to the object and the relative speed, the arithmetic processing A unit that inputs the measurement data and integrates for each distance gate; an FFT processing unit that inputs an integral value of a predetermined number of FFT points from the presum unit and performs an FFT process; and the FFT process An object detection unit that detects at least the position and relative speed of the object based on the processing result of the unit, and the number of FFT points is set for each distance gate. Features that are.

  According to the present invention, by changing the number of FFT points based on the distance to the object, the radar apparatus capable of detecting the relative speed of the object with a suitable speed resolution and reducing the processing time, and The control method can be provided.

It is a flowchart for demonstrating the control method of the radar apparatus which concerns on 1st Embodiment of this invention. 1 is a block diagram showing a configuration of a radar apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of the radar apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart for demonstrating the control method of the radar apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the radar apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart for demonstrating the control method of the radar apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart for demonstrating the control method of the conventional radar apparatus.

  A radar apparatus and a control method thereof according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. Each component having the same function is denoted by the same reference numeral for simplification of illustration and description.

(First embodiment)
When the relative speed of the object is obtained by FFT processing, the speed resolution is proportional to the number of FFT points. For this reason, if the number of FFT points is reduced, the speed resolution is lowered and the relative speed may not be detected with high accuracy.

The number of FFT points is Nf, the number of integrations of measurement data at each FFT point is Ni, the carrier frequency of the pulse signal (radio wave) radiated from the radar device is f0, the repetition frequency of the pulse signal is fp (repetition period is Tp), and When the speed of light is c [m / s], for example, when the radar apparatus is provided with two receiving antennas on the left and right and receives signals alternately, the time Ts required to acquire the integral value of the number of FFT points Nf (hereinafter this is sampled) Called the period)
Ts = Tp × Ni × Nf × 2
Given in. When this is converted to a frequency (sampling frequency fs),
fs = 1 / (Tp × Ni × Nf × 2) = fp / (Ni × Nf × 2) (3)
It becomes.

The Doppler frequency fd is given by Equation (1). The relative speed (Doppler resolution) when the Doppler frequency fd is equal to the sampling frequency fs is the minimum measurable relative speed, and the speed resolution is determined by the relative speed. The velocity resolution increases as the minimum measurable relative velocity value decreases. Assuming that the minimum relative speed is Vd, the relative speed Vd is calculated as follows from the equations (2) and (3): Vd = fs × c / (2 × f0) = fp / (Ni × Nf × 2) × c / (2 × f0) (4)
Given in. From the above equation (4), it can be seen that the minimum relative speed Vd is inversely proportional to the FFT point number Nf. Therefore, the larger the FFT point number Nf, the smaller the minimum measurable relative velocity Vd and the higher the velocity resolution.

As an example, when the number of FFT points Nf is 64, the number of integrations Ni is 32, the carrier frequency f0 is 26.5 GHz, and the repetition frequency fp of the pulse signal is 1 MHz, the sampling frequency fs given by Equation (3) is
fs = 1 [MHz] / (32 × 64 × 2) = 244 [Hz]
The minimum relative velocity Vd that can be measured from now on is
Vd = 2.44 [Hz] × c / (2 × 26.5 [GHz])
= 1.38 [m / s] = 4.97 [km / h]
It becomes.

  In the above example, when the FFT point number Nf is 64, the minimum measurable relative speed is about 5 km / h. On the other hand, the maximum measurable relative speed is given by a value obtained by multiplying the minimum relative speed Vd by the number of FFT points Nf. In this example, about 5 km / h to 160 km / h (-160 km / h to +160 km / h) It is possible to determine the speed within the range. Here, if the number of FFT points is reduced to ½, 32, the sampling frequency fs is doubled to 488 [Hz], and the minimum measurable relative speed Vd is also doubled to about 10 km / h. As a result, the relative speed is detected at a minimum value of about 10 km / h or more, and the speed resolution may be lowered, and the relative speed may not be detected with high accuracy.

  When the object is far away, it is not always necessary to detect the relative speed with a high speed resolution because there is a time margin for the collision even if the object approaches at a high relative speed. On the other hand, when the object is in the vicinity, there is little time margin until the collision is reached, so that it is required to detect the relative speed with high speed resolution. Therefore, in the radar apparatus and its control method according to the present embodiment, the relative resolution of the object can be appropriately detected by suitably changing the speed resolution based on the distance to the object. At the same time, for a far distance gate that does not require high speed resolution, the processing time is shortened by reducing the number of FFT points.

  A radar apparatus and a control method thereof according to the first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a flowchart for explaining a control method of the radar apparatus 100 of the present embodiment. FIG. 2 is a block diagram showing the configuration of the radar apparatus 100 of the present embodiment.

  In FIG. 2, a radar apparatus 100 includes a transmission unit 101 that generates a transmission signal, a transmission antenna 102 that radiates the transmission signal generated by the transmission unit 101 into the air as a radio wave, and a reflection in which the radiated radio wave is reflected by an object. A receiving antenna 103 that receives a wave, a receiving unit 104 that receives a reception signal from the receiving antenna 103 and obtains measurement data for each distance gate, and inputs measurement data for each distance gate from the receiving unit 104 An arithmetic processing unit 110 that acquires object information such as a position and a relative speed, and a control unit 105 that controls processing of each of the transmission unit 101 and the reception unit 104 are provided.

  The control unit 105 controls the transmission unit 101 to generate a pulse signal and output it to the transmission antenna 102, for example, at a pulse repetition period of 1 μs. Further, the receiving unit 104 is controlled to acquire measurement data from the received signal at a timing corresponding to a predetermined distance gate. The control unit 105 can control the receiving unit 104 to acquire measurement data corresponding to a plurality of distance gates from a single pulse signal output. The measurement data acquired by the receiving unit 104 is output to the arithmetic processing unit 110, where processing such as FFT is performed to detect object information.

  The arithmetic processing unit 110 includes a presum unit 111, an FFT processing unit 112, an object detection unit 113, and a determination unit 115, and a storage unit 114 is connected thereto. The presum unit 111 integrates the measurement data input from the receiving unit 104 for each distance gate. The FFT processing unit 112 performs an FFT process using the integral value calculated by the presum unit 111. The object detection unit 113 acquires object information including the position and relative speed of the object based on the processing result by the FFT processing unit 112. The determination unit 115 manages each process in the presum unit 111, the FFT processing unit 112, and the object detection unit 113. In addition, the determination unit 115 notifies the control unit 105 of a distance gate for which the reception unit 104 acquires measurement data.

  In the presum unit 111, the measurement data input from the receiving unit 104 is integrated for a predetermined number of integrations (hereinafter, the predetermined number of integrations is indicated by Ni) for each distance gate. Then, an integral value obtained by integrating the integration number Ni is acquired for a predetermined number of FFT points. The FFT processing unit 112 performs an FFT process using the integral value of a predetermined number of FFT points acquired by the presum unit 111.

  In the radar apparatus 100 of this embodiment, the number of integral values acquired by the presum unit 111 and used for the FFT processing by the FFT processing unit 112, that is, the number of FFT points is set for each distance gate. In this embodiment, the number of FFT points is not set to the same value common to all the distance gates, but different numbers of FFT points are set for at least a part of the distance gates. In the following, the number of FFT points of the distance gate i is represented by Nfi, and the largest Nfi is represented by Nf as the FFT point prescribed number.

  In this embodiment, the number of FFT points Nfi for each distance gate is set to a value smaller than the number of FFT points of nearby distance gates for the distance gate corresponding to the far side of the detection range of the radar apparatus 100. Thereby, in the distance gate with a small number of FFT points Nfi, the FFT processing unit 112 performs the FFT processing using the integral value with a small number of points, and the speed resolution is lowered. However, since the object in the distance has time to reach the collision, there is no problem even if the velocity resolution is lowered.

  As described above, in the distance gate corresponding to a distant place, the number of FFT points Nfi, which is the number of integral values acquired by the presum unit 111, is reduced, so that an integral value is acquired while ensuring an appropriate speed resolution. The processing time and the time required for the FFT processing can be shortened.

  A method for controlling the radar apparatus 100 according to the present embodiment will be described in more detail with reference to FIG. In the figure, when an object detection cycle is started (step S1), a pulse signal is generated by the transmission unit 101 every predetermined pulse repetition cycle, and a pulse signal is radiated from the transmission antenna 102 (step S2). When the pulse signal radiated into the air is reflected by the object, it is received by the receiving antenna 103 as a reflected wave, and the received signal is processed by the receiving unit 104. The measurement data processed by the receiving unit 104 is output to the arithmetic processing unit 110 in step S3.

  In the arithmetic processing unit 110, the determination unit 115 manages the processes of the presum unit 111, the FFT processing unit 112, and the object detection unit 113, and performs each determination described below. In step S4, the presum unit 111 adds the measurement data input from the receiving unit 104 to each distance gate to calculate an integral value.

  When the processes of steps S3 and S4 are completed, the number of integrations in the distance gate group is counted, and in step S5, it is determined whether or not the counted number of integrations has reached a predetermined integration number Ni. As a result, if it is determined that the integration number of the distance gate has reached the predetermined integration number Ni, the integration value of the distance gate is stored in the storage unit 114, and then the process proceeds to step S6. On the other hand, if it is determined in step S5 that the integration number of the distance gate has not reached the predetermined integration number Ni, the processes in steps S2 to S5 are performed again in the next pulse repetition period.

  In step S6, a preset value is input as the number of FFT points Nfi for each distance gate. The number of FFT points Nfi for each distance gate is stored in advance in the storage unit 114, for example, and is read and used.

  In step S7, it is determined whether or not the current number of FFT points is equal to the number of FFT points Nfi for each distance gate. As a result, when it is determined that the current number of FFT points is equal to the number of FFT points Nfi for each distance gate, the process proceeds to step S8 to perform the FFT process on the distance gate. On the other hand, when it is determined that the current number of FFT points is not equal to the number of FFT points Nfi for each distance gate, the processing in steps S2 to S7 is performed again in the next pulse repetition period until Nfi is reached. Add the number of FFT points. In step S8, the integral value of the number of FFT points Nfi for each distance gate is read from the storage unit 114, and FFT processing is performed using this value.

  In step S9, it is determined whether or not the equivalent sampling has reached a predetermined equivalent number of times Ns. As a result, if it is determined that the predetermined equivalent sampling number Ns has not been reached, an equivalent sampling process is performed in step S10 to select the next plurality of distance gates. And the process of step S2-S10 is performed in the pulse repetition period after the next time. In step S <b> 10, the measurement data acquisition timing is changed and notified to the control unit 105 so that the reception unit 104 acquires measurement data of a plurality of distance gates processed in the next equivalent sampling.

  On the other hand, if it is determined in step S9 that the predetermined equivalent sampling number Ns has been reached, the processing for all distance gates is completed. Then, based on the FFT processing results obtained so far, the object detection unit 113 acquires object information such as the position and relative speed of the object. Further, the object information is output to a predetermined display device or the like, and the process of the object detection cycle is ended (step S11).

  According to the radar apparatus and its control method of the present embodiment, the number of FFT points, which is the number of integral values used for FFT processing, can be set for each distance gate. In particular, by setting the number of FFT points Nfi for each distance gate to a distance gate corresponding to a far distance of the detection range, it is possible to appropriately acquire object information with a suitable speed resolution and process it together with it. The time can be shortened.

(Second Embodiment)
A radar apparatus and a control method thereof according to the second embodiment of the present invention will be described below with reference to FIGS. FIG. 3 is a block diagram showing a configuration of the radar apparatus 200 of the present embodiment. FIG. 4 is a flowchart for explaining a control method of the radar apparatus 200 of the present embodiment. The radar apparatus 200 according to the present embodiment is different from the raid apparatus 100 according to the first embodiment in the processing in the determination unit 215. In the first embodiment, the number of FFT points Nfi can be set for each distance gate, and in particular, by setting the number of FFT points Nfi small with respect to the distance gate corresponding to the far side of the detection range, the presum unit 111 and the FFT processing unit The processing time in can be shortened.

  However, a plurality of distance gates to be subjected to one equivalent sampling process are generally set at equidistant intervals from one corresponding to a short distance to one corresponding to a long distance. Therefore, even if the number of FFT points of the distance gate corresponding to the long distance is reduced, in order to obtain the measurement data of the distance gate corresponding to the short distance, the number of integral values of the short distance distance gate is the number of the FFT points. It is necessary to output a pulse signal until it reaches As a result, even if the number of FFT points of the long-distance distance gate is reduced, the number of times the pulse signal is output cannot be reduced, and as a result, the update rate of the radar apparatus cannot be shortened.

  However, it is not necessary to receive a reflected wave from a long distance after the long distance gate has acquired the integral value of the number of FFT points set thereto. As a result, the pulse repetition period, which is the interval at which the pulse signal is output, can be shortened (the pulse repetition frequency PRF can be increased). By shortening the pulse repetition period, it is possible to shorten the time taken to output the pulse signal the same number of times, and it is possible to shorten the update rate of the radar apparatus.

  In the radar apparatus 200 according to the present embodiment, after finishing the processing of the long-distance distance gate with the reduced number of FFT points, the pulse repetition period is shortened and a pulse signal is output, and the measurement data at that time is used to calculate the near distance. An FFT point for the distance gate of the distance is added. As a result, the time required to acquire the integral value of the additional FFT point can be shortened, and the update rate of the radar apparatus 200 is also shortened.

The effects of the radar apparatus according to the present embodiment will be described below for the above-described conventional radar apparatus. In the conventional radar apparatus described above, the pulse repetition period is 1 μs, the predetermined number of integrations for each distance gate is 32, the FFT point specified number is 64, and the predetermined equivalent sampling number is 16, and the radiated radio waves on both the left and right sides are measured. Is going to do. At this time, the total processing time in one object detection cycle is
1 μs × 32 × 64 × 16 × 2 = 65.536 ms
Thus, the time required for measuring the total distance gate is about 70 ms.

  In the conventional radar device described above, the detection range can be set to 36 m, for example. Here, the radar apparatus 200 of the present embodiment is applied, and the number of FFT points is set to 64 for a short distance gate up to 18 m, and the number of FFT points is half to 32 for a distance gate far from 18 m. It can be. At the same time, after acquiring the integral values of 32 FFT points, only the short-distance measurement data up to 18 m is acquired, so that the pulse repetition period can be reduced to 0.5 μs. As a result, the update rate that took about 70 ms becomes 35 ms + 35/2 ms, and can be shortened to about 52 ms.

  The control method of the radar apparatus 200 of this embodiment is demonstrated below using FIG. Here, for the short distance gate, the integral value of the FFT point Nf is obtained as the number of FFT points, and for the long distance gate, the integral value of Nf1 less than the FFT point prescribed number Nf is obtained. It shall be.

  In the radar apparatus 200 of the present embodiment, it is determined in step S21 whether or not a long distance gate is included. When a long distance gate is not included, it is determined that only a short distance gate is set, and a short pulse repetition period is set in step S22. On the other hand, when it is determined that a long distance gate is included, a normal long pulse repetition period is set in step S23.

  Thereafter, the same processing as in the first embodiment is performed from step S2 to step S5, and if it is determined in step S5 that the number of integrations has reached the predetermined number of integrations Ni, the current number of FFT points is determined by the distance gate in step S24. It is determined whether or not the number corresponds to the number of FFT points Nfi for each. As a result, when it matches Nfi, the process proceeds to step S25. In step S25, the FFT processing is performed on the long distance gate, and only the short distance gate is processed in the next and subsequent cycles.

  On the other hand, when it is determined in step S24 that the number of FFT points does not coincide with Nfi, it is determined in step S26 whether the current number of FFT points is smaller than the specified FFT point number Nf. Proceed to On the other hand, when the current number of FFT points reaches the FFT point prescribed number Nf, the process proceeds to step S27, and the FFT processing is performed on the short distance gate. After step S9, the same processing as in the first embodiment is performed.

  As described above, in the radar apparatus 200 according to the present embodiment, after acquiring the integral value of the number of FFT points necessary for the distant distance gate, the pulse signal is output with a short pulse repetition period. Then, until the number of FFT points necessary for the short-distance distance gate is reached, an integrated value is acquired from the measurement data when the pulse repetition period is shortened. As a result, the relative speed can be detected with a suitable speed resolution in the entire detection range, and the update rate can be shortened.

(Third embodiment)
A radar apparatus and a control method thereof according to the third embodiment of the present invention will be described below with reference to FIGS. FIG. 5 is a block diagram illustrating a configuration of the radar apparatus 300 according to the present embodiment. FIG. 6 is a flowchart for explaining a control method of the radar apparatus 300 of the present embodiment. The radar apparatus 300 according to the present embodiment is different from the raid apparatuses 100 and 200 according to the first and second embodiments in the processing in the determination unit 315. In the first embodiment, the number of FFT points Nfi can be set for each distance gate, and the processing time of the radar apparatus 100 is reduced by setting the number of FFT points Nfi to be small with respect to the distance gate corresponding to the far side of the detection range. It was shortened.

  If the number of FFT points Nfi of the distance gate corresponding to the far position is set to be small, not only the speed resolution at the distance gate is lowered, but also the signal-to-noise ratio (S / N ratio) when detecting an object is lowered. To do. Therefore, there is a risk that an object at a distant position may be overlooked. In particular, when the far object is a low reflection object (for example, an object having a small size), if the S / N ratio is lowered by reducing the FFT point, this may not be detected.

  Therefore, in the radar apparatus 200 of the present embodiment, for the distance gate in which the number of FFT points Nfi is set to be small, the integration number Ni of the integration value for each FFT point calculated by the presum unit 111 is increased, so that S / The N ratio is set to be higher than that of the normal measurement, so that a far object can be seen better than usual.

In a normal distance gate (distance gate corresponding to a short distance) that does not reduce the number of FFT points, FFT points having a prescribed FFT point number Nf are set. When the number of integrations per FFT point in a normal distance gate is Ni0, and the number of FFT points of the distance gate with the reduced number of FFT points and the number of integrations per FFT point are Nf1 and Ni1, respectively, the number of integrations Ni1 is It is good to decide to meet.
Nf1 × Ni1 ≦ Nf × Ni0

  The above formula is such that the product of the number of FFT points Nf1 of the distance gate with the number of FFT points reduced and the number of integrations Ni1 does not exceed the product of the normal number of FFT points Nf and the number of integrations Ni0 of the normal distance gate. It is shown that. Thereby, the update rate of the radar apparatus 300 is prevented from becoming long by changing the number of FFT points and the number of integrations. When the product of the number of FFT points and the number of integrations is the same before and after the change, the update rate does not change, and when the product becomes smaller after the change, the processing time is shortened, and this is applied to the radar apparatus 200 of the second embodiment. Sometimes the update rate is shortened.

  A control method of the radar apparatus 300 of this embodiment will be described below with reference to FIG. When the process up to the calculation of the integral value in step S4 is completed as in the first embodiment, the number of integrations Ni of the distance gate is input in step S30. The integration number Ni for each distance gate is stored in the storage unit 114, for example, and the integration number Ni is read from the storage unit 114 in step S30.

  In the subsequent step S5, it is determined whether or not the current number of integrations is equal to the number of integrations Ni of the distance gate input in step S30. If not, the processes in steps S2 to S5 are performed again in the next pulse repetition period. On the other hand, when the current number of integrations is equal to the number of integrations Ni, the FFT point number Nfi of the distance gate is input in the next step S6. In step S7, it is determined whether or not the current number of FFT points is equal to Nfi. If the number is equal, FFT processing by the FFT processing unit 112 is performed in step S8. Thereafter, the processes in steps S9 to S11 are performed in the same manner as in the first embodiment.

  According to the radar apparatus 300 of the present embodiment, the number of integrations Ni for calculating the integral value for each FFT point is increased while the number Nfi of FFT points is reduced for a far distance gate. As a result, the relative speed of a distant object can be detected with a speed resolution of an appropriate size, and the distant object can be detected with a high S / N ratio, thereby preventing the distant object from being overlooked. Is possible.

  The description in the present embodiment shows an example of the radar apparatus and the control method thereof according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the radar apparatus and its control method in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

100, 200, 300 Radar device 101 Transmitter 102 Transmitting antenna 103 Receiving antenna 104 Receiving unit 105 Control unit 110 Arithmetic processing unit 111 Presumming unit 112 FFT processing unit 113 Object detection unit 114 Storage unit 115, 215, 315 Determination unit

Claims (6)

Radio waves are radiated a plurality of times at a predetermined repetition period for each object detection cycle, a reflected wave reflected by an object within a predetermined detection range is received for each radiated radio wave, and measurement data for each distance from the reflected wave , And an integral value obtained by adding a predetermined number of integrations to the corresponding distance gate is obtained, the integral value is obtained as an integral value of one FFT point, and this is obtained by a predetermined number of FFT points. A radar apparatus control method for performing an FFT process using an integral value and detecting at least a distance and a relative speed to the object using a result of the FFT process,
A method of controlling a radar apparatus, wherein the number of FFT points is set for each distance gate. The radar apparatus control method according to claim 1, wherein the number of FFT points is set to be small with respect to the distance gate corresponding to a distant distance. When the distance gate corresponding to the far distance obtains the integral value of the set number of FFT points, the distance gates other than the distance gate corresponding to the far distance are shortened by shortening the repetition period. The radar apparatus control method according to claim 2, wherein an integral value of the number of FFT points is acquired. 4. The radar apparatus control method according to claim 2, wherein the predetermined number of integrations is increased with respect to the distance gate set with a small number of FFT points. The reduced number of FFT points and the increased number of integrations are set such that the product of both is equal to or less than the product of the original number of FFT points and the predetermined number of integrations. Item 5. A method for controlling a radar apparatus according to Item 4. Radio waves are radiated a plurality of times at a predetermined repetition period for each object detection cycle, a reflected wave reflected by an object within a predetermined detection range is received for each radiated radio wave, and measurement is performed for each distance gate from the reflected wave A radar device that acquires data, processes the measurement data with an arithmetic processing unit, and detects at least the distance and relative speed to the object,
The arithmetic processing unit is a presum unit that inputs the measurement data and integrates for each distance gate; an FFT processing unit that inputs the integral value of a predetermined number of FFT points from the presum unit and performs an FFT process; An object detection unit that detects at least a position and a relative speed of the object based on a processing result by the FFT processing unit;
The number of FFT points is set for each of the distance gates.

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