阅读说明：本技术 雷达装置 (Radar apparatus ) 是由 柏木克久 于 2019-07-17 设计创作，主要内容包括：本发明涉及雷达装置。雷达装置(1)具备：单系统的发送系统(2),发送被调频的发送信号(St)；单系统的接收系统(6),以发送信号(St)的被物标反射的反射波作为接收信号(Sr)接收,生成差拍信号(Sb)；以及信号处理部(10),基于差拍信号(Sb)来检测物标的位置。发送系统(2)具有发送天线(3),该发送天线安装于移动体(M),并向与移动体(M)的移动方向正交的方向发射发送信号(St)。信号处理部(10)基于物标的相对速度(Veff)和移动体(M)的移动速度(V)来检测物标的方位角(θ)。(The present invention relates to a radar apparatus. A radar device (1) is provided with: a single-system transmission system (2) for transmitting a frequency-modulated transmission signal (St); a single-system reception system (6) that receives, as a reception signal (Sr), a reflected wave of the transmission signal (St) reflected by the target object, and generates a beat signal (Sb); and a signal processing unit (10) that detects the position of the target object on the basis of the beat signal (Sb). The transmission system (2) has a transmission antenna (3) that is attached to a mobile body (M) and that transmits a transmission signal (St) in a direction orthogonal to the direction of movement of the mobile body (M). A signal processing unit (10) detects the azimuth angle (theta) of a target object on the basis of the relative speed (Veff) of the target object and the moving speed (V) of a moving body (M).)

1. A radar device is provided with:

a transmitting unit of a single system for transmitting a frequency-modulated transmission signal;

a single-system reception unit that receives a reflected wave of the transmission signal reflected by a target object as a reception signal and generates a beat signal that is a difference between the transmission signal and the reception signal; and

a detection unit that detects a position of the target object based on the beat signal,

it is characterized in that the preparation method is characterized in that,

the transmission unit has a transmission antenna that is attached to a mobile body and transmits the transmission signal in a direction orthogonal to a moving direction of the mobile body,

the detection unit detects an azimuth angle of the target based on the relative speed of the target and the moving speed of the moving body.

2. Radar apparatus according to claim 1,

the transmitting section repeatedly transmits a chirp signal in which the frequency linearly increases or decreases with time as the transmission signal,

the detection unit estimates a relative velocity of the target object based on a phase difference between the beat signal generated from the transmission signal and the reception signal, the chirp signal including a plurality of periods.

Technical Field

The present invention relates to a radar device that measures, for example, a distance and a direction to a target object.

Background

A radar device of FMCW (Frequency Modulated Continuous Wave) system including a transmission antenna and a reception antenna is known (non-patent document 1). The transmission antenna transmits a transmission signal composed of a chirp signal generated in an RF (Radio Frequency: electromagnetic Frequency) signal generator. The receiving antenna receives a reflected wave when a target object (target) reflects a transmission signal. The reflected wave received by the receiving antenna is down-converted into an IF (Intermediate Frequency) signal by a mixer and converted into a Digital signal by an ADC (Analog to Digital Converter). The microcomputer uses the digital signal to estimate the distance and direction (azimuth) to the target object.

Non-patent document 1: cesar Iovescu, Sandeep Rao, "The fundamental of millimeter wave sensors", Texas Instruments white paper (http:// www.ti.com/lit/wp/spy005. pdf)

However, in the radar device described in non-patent document 1, the distance to the target object is determined using the bandwidth and the period of use of the transmission signal including the chirp signal and the frequency of the IF signal. When reflected waves from a target object are received by a plurality of receiving antennas, a phase difference occurs between a plurality of IF signals corresponding to the plurality of receiving antennas. Therefore, the azimuth of the target object is determined using the phase difference between the plurality of IF signals. However, in the radar apparatus of the related art, in order to use the phase difference between the plurality of IF signals when determining the azimuth of the target object, two or more reception systems including the reception antennas are required. Therefore, there is a problem that the antenna area, the receiving circuit (including a low noise amplifier, a mixer, a filter, and the like), and the power consumption increase.

Disclosure of Invention

The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a radar apparatus which is small in size and can reduce power consumption.

In order to solve the above problem, the present invention is a radar device including: a transmitting unit of a single system for transmitting a frequency-modulated transmission signal; a single-system reception unit that receives, as a reception signal, a reflected wave of the transmission signal reflected by a target object, and generates a beat signal that is a difference between the transmission signal and the reception signal; and a detection unit that detects a position of the target object based on the beat signal, wherein the transmission unit includes a transmission antenna that is attached to a moving body and that transmits the transmission signal in a direction orthogonal to a moving direction of the moving body, and the detection unit detects an azimuth angle of the target object based on a relative speed of the target object and the moving speed of the moving body.

According to the present invention, the radar apparatus can be miniaturized and power consumption can be reduced.

Drawings

Fig. 1 is a plan view showing a state in which a radar apparatus according to an embodiment of the present invention is mounted on a mobile body.

Fig. 2 is a block diagram showing the radar apparatus in fig. 1.

Fig. 3 is a characteristic diagram showing temporal changes in the frequencies of the transmission signal, the reception signal, and the beat signal.

Fig. 4 is a characteristic diagram showing temporal changes in the frequencies of the transmission signal and the reception signal and the phase of the beat signal.

Fig. 5 is an explanatory diagram showing a positional relationship between the radar device and the target object.

Fig. 6 is a flowchart showing the position estimation process of the target object performed by the signal processing unit.

Fig. 7 is an explanatory diagram showing a relationship between a distance to a target object and a relative speed measured by the radar device.

Detailed Description

Hereinafter, a radar apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

Fig. 1 and 2 show a radar apparatus 1 according to an embodiment of the present invention. The radar apparatus 1 is an FMCW radar apparatus.

The radar device 1 includes a transmission system 2 as a transmission unit, a reception system 6 as a reception unit, and a signal processing unit 10 as a detection unit. The transmission system 2, the reception system 6, and the signal processing unit 10 are provided on, for example, a printed circuit board (not shown). The radar device 1 is mounted on a mobile body M (for example, a vehicle). The moving body M moves at a moving speed V in the X direction, for example.

The transmission system 2 transmits a frequency-modulated transmission signal St. The transmission system 2 includes a transmission antenna 3, a power amplifier 4, and a local oscillator 5. The transmitting antenna 3 transmits the local signal SL as the transmission signal St into the air. The transmission antenna 3 is constituted by, for example, an omnidirectional antenna. The transmission antenna 3 transmits the transmission signal St in the Y direction orthogonal to the traveling direction (X direction) of the mobile body M.

The power amplifier 4 amplifies the power of the local signal SL output from the local oscillator 5 and outputs the amplified power to the transmission antenna 3. The local oscillator 5 oscillates the local signal SL. Specifically, the local oscillator 5 outputs the local signal SL composed of a chirp signal whose frequency linearly increases or decreases with time, based on the chirp control signal Sc from the signal processing section 10. The local oscillator 5 outputs the generated local signal SL to the power amplifier 4 and the mixer 8.

The reception system 6 receives a reflected wave of the transmission signal St reflected by the target object as a reception signal Sr, and generates a beat signal Sb, which is a difference signal between the transmission signal St and the reception signal Sr. The reception system 6 includes a reception antenna 7 and a mixer 8. The receiving system 6 may further include a low noise amplifier and a filter. When the target object reflects the transmission signal St, the reception antenna 7 receives a reception signal Sr composed of a reflected wave (echo signal) reflected and returned from the target object.

The mixer 8 outputs the beat signal Sb from the reception signal Sr reflected by the target object based on the transmission signal St received by the reception antenna 7 and the transmission signal St (local signal SL). Specifically, mixer 8 multiplies reception signal Sr received by reception antenna 7 by local signal SL identical to transmission signal St output from local oscillator 5 to generate beat signal Sb. The mixer 8 is connected to the signal processing unit 10 via an ADC 9. The ADC9 converts the beat signal Sb from an analog signal to a digital signal.

The signal processing unit 10 performs signal processing on the beat signal Sb. The beat signal Sb converted into a digital signal by the ADC9 is input to the signal processing unit 10. The signal processing unit 10 includes, for example, FFT, a microcomputer, and the like. In addition, the signal processing unit 10 includes a storage unit 10A. The storage unit 10A stores a program of the position estimation process shown in fig. 6. The signal processing unit 10 executes a program of the position estimation process stored in the storage unit 10A. When the transmission signal St including the chirp signal of a plurality of consecutive times is transmitted, the storage section 10A stores the beat signal Sb corresponding thereto.

The signal processing unit 10 outputs a chirp control signal Sc to the local oscillator 5. The signal processing unit 10 measures the distance to the target object (distance measurement) and the direction using the beat signal Sb output from the mixer 8.

The distance measurement of the target object by the signal processing unit 10 will be described with reference to fig. 3. As shown in fig. 3, the frequency of the transmission signal St linearly increases with time from f0 to f0+ B in the chirp period Tm (period of the chirp signal). The reception signal Sr is delayed by the reciprocation time τ until the transmission signal St is reflected by the target object and returns. The frequency (peak frequency fp) of the beat signal Sb is proportional to the reciprocation time τ until the transmission signal St is reflected by the target and returns. At this time, a peak frequency fp corresponding to the reciprocation time τ appears in the frequency component of the beat signal Sb. Therefore, the signal processing unit 10 can detect the distance R of the target object by detecting the peak frequency fp of the beat signal Sb according to the formula of formula 1. Further, in the equation of equation 1, c represents the speed of light, and B represents the chirp-use bandwidth.

[ formula 1]

Next, the measurement of the orientation of the target object by the signal processing unit 10 will be described with reference to fig. 4 and 5. Fig. 5 illustrates a case where an object exists in a direction of an azimuth angle θ, which is an angle with respect to a Y direction orthogonal to the X direction. In this case, the azimuth angle θ corresponds to the arrival direction of the received signal Sr.

As shown in fig. 4, the radar apparatus 1 transmits a transmission signal St consisting of two chirp signals that are continuous from the transmission antenna 3. The transmission signal St is reflected by the target object and received as a reception signal Sr by the reception antenna 7, thereby generating a beat signal Sb. At this time, the phase of the beat signal Sb based on the first chirp signal and the phase of the second beat signal Sb are different from each other according to the relative velocity Veff between the target object and the radar device 1. Based on the phase difference at that timeThe relative velocity Veff is obtained from equation 2. Where λ is the wavelength of the transmission signal St in equation 2.

[ formula 2]

In addition, as shown in fig. 5, when the reflection direction of the reflected wave from the target toward the radar device 1 is defined as a vector r, and the moving body M moves in the X direction at the moving speed V, the relative speed Veff is defined by a unit vector r of the vector r as shown in equation 3_eAnd the inner product of the vector of the moving speed V. Therefore, the azimuth angle θ can be obtained from equation 4 based on the relative velocity Veff and the moving velocity V.

[ formula 3]

[ formula 4]

Next, the position estimation processing of the target object by the signal processing unit 10 will be described with reference to fig. 6.

In step S1 in fig. 6, transmission signal St is transmitted from transmission antenna 3 (see fig. 3 and 4). The transmission signal St from the transmission antenna 3 is reflected by the target object, and a reflected wave composed of an echo signal is generated. In step S2, the reflected wave from the target object is received by the reception antenna 7 as the reception signal Sr. The mixer 8 generates a beat signal Sb based on the reception signal Sr. The signal processing unit 10 stores the beat signal Sb in the storage unit 10A.

In step S3, the signal processing unit 10 calculates the distance R to the target object from the beat signal Sb stored in the storage unit 10A. Specifically, the beat signal Sb stored in the storage unit 10A is fourier-transformed by FFT, and the peak frequency fp at which the signal intensity increases is detected in the frequency component of the beat signal Sb. The distance R from the radar device 1 to the target object is calculated according to formula 1 based on the detected peak frequency fp.

In step S4, the signal processing unit 10 calculates the relative speed Veff between the target object and the radar device 1 from the beat signal Sb stored in the storage unit 10A. Specifically, the phase difference between the chirp signals is obtained from the beat signal Sb based on the multiple chirp signalsBased on the phase differenceAnd calculates the relative velocity Veff according to equation 2.

In step S5, the azimuth angle θ is calculated based on the relative velocity Veff. Specifically, the azimuth angle θ is calculated from equation 4 based on the relative velocity Veff. When step S5 ends, the process repeatedly proceeds to step S1.

Fig. 7 shows the result of actually measuring the distance R to the target object and the relative speed Veff using the radar device 1. Fig. 7 illustrates an example of measuring a plurality of (for example, 10) target objects O1 to O10 in a state where the radar device 1 is installed in the moving object M. The shade in the graph corresponds to the intensity of the reflected wave from the target object. The detected target objects O1 to O3 are approaching the radar device 1 in the region where the relative velocity Veff is positive. Therefore, the target objects O1 to O3 are located forward in the moving direction of the moving object M. On the other hand, the detected target objects O8 to O10 are moving away from the radar device 1 in the region where the relative velocity Veff is negative. Therefore, the target objects O8 to O10 are located rearward in the moving direction of the moving body M. The detected target objects O4 to O7 in the region where the relative speed Veff is around 0 are shown to move at almost the same speed as the radar device 1. As shown in fig. 7, the radar device 1 can measure the distance R and the relative speed Veff of each of the plurality of target objects O1 to O10. Therefore, the azimuth angle θ of the target objects O1 to O10 can be estimated from the formula 4 based on the relative speed Veff of the target objects O1 to O10 and the moving speed V of the moving body M. The arrows in FIG. 7 correspond to azimuth angles θ for the objects O1-O10.

As described above, in the radar apparatus 1 according to the present embodiment, the transmission system 2 has the transmission antenna 3, and the transmission antenna 3 is attached to the mobile body M and transmits the transmission signal St in the direction orthogonal to the moving direction of the mobile body M. Therefore, the transmission signal St can be emitted in a wide range from the front to the rear in the moving direction of the moving body M, and the target object can be detected in these ranges. The signal processing unit 10 detects the azimuth angle θ of the target based on the relative speed Veff of the target and the moving speed V of the moving body M. At this time, the relative speed Veff of the target object can be measured by the single-system transmission system 2 and the single-system reception system 6. Therefore, compared to the conventional art requiring a plurality of receiving systems, the radar apparatus 1 can be downsized and the power consumption can be reduced.

In addition, the transmission system 2 repeatedly transmits a chirp signal whose frequency linearly increases with time as the transmission signal St, and the signal processing section 10 generates a phase difference based on the phase difference of the beat signal Sb generated from the transmission signal St and the reception signal Sr based on the chirp signal including a plurality of cycles (for example, 2 cycles)The relative speed Veff of the target object is estimated. Therefore, for example, compared to a case where the relative velocity is estimated based on the change in the beat frequency (doppler shift) at the time of the rise and fall of the frequency, the phase difference based on the beat signal Sb can be usedThe relative velocity Veff of the object is more easily calculated.

In the above embodiment, in order to estimate the azimuth angle θ, it is necessary that the moving speed V is not 0 and the moving body M moves. Therefore, when the mobile body M is stopped, the azimuth angle θ of the target object may be estimated using a plurality of receiving systems as in the conventional technique, and when the mobile body M starts moving, the mobile body M may be switched to a single receiving system to estimate the azimuth angle θ of the target object.

In the above-described embodiment, the transmission signal St uses a chirp signal whose frequency linearly increases, but a chirp signal whose frequency linearly decreases may be used.

In the above embodiment, the relative velocity Veff is detected using the beat signal based on the chirp signal twice. The present invention is not limited to this, and for example, a transmission signal having a rising portion and a falling portion of the frequency may be transmitted, and the relative speed may be detected based on a change in the beat frequency at the rising time and the falling time of the frequency. In addition, the relative speed may also be detected based on a temporal change in the distance R.

In the above embodiment, the case where the transmission antenna 3 and the reception antenna 7 are each configured by a single antenna element is exemplified. The present invention is not limited to this, and the transmitting antenna and the receiving antenna may be configured by an antenna array having a plurality of antenna elements.

In the above embodiment, the radar device 1 that estimates the position of the target object in the two-dimensional plane was described as an example, but the present invention can also be applied to a radar device that estimates the position of the target object in the three-dimensional space.

The specific numerical values described in the above embodiments are merely examples, and are not limited to the illustrated values. These values are set as appropriate according to the specification of the application object, for example.

Next, the invention included in the above-described embodiments will be described. The present invention is a radar device including: a transmitting unit of a single system for transmitting a frequency-modulated transmission signal; a single-system reception unit that receives, as a reception signal, a reflected wave of the transmission signal reflected by a target object, and generates a beat signal that is a difference between the transmission signal and the reception signal; and a detection unit that detects a position of the target object based on the beat signal, wherein the transmission unit includes a transmission antenna that is attached to a moving body and that transmits the transmission signal in a direction orthogonal to a moving direction of the moving body, and the detection unit detects an azimuth angle of the target object based on a relative speed of the target object and the moving speed of the moving body.

With this configuration, the transmission unit includes a transmission antenna that is attached to the mobile body and transmits the transmission signal in a direction orthogonal to the moving direction of the mobile body. Therefore, the transmission signal can be emitted in a wide range from the front to the rear in the moving direction of the moving body, and the target object can be detected in these ranges. The detection unit detects the azimuth angle of the target based on the relative speed of the target and the moving speed of the moving object. In this case, the relative speed of the target object can be measured by the single-system transmission unit and the single-system reception unit. Therefore, compared to the conventional art requiring a plurality of receiving units, the radar apparatus can be downsized and the power consumption can be reduced.

In the present invention, the transmission unit repeatedly transmits a chirp signal whose frequency linearly increases or decreases with time as the transmission signal, and the detection unit estimates the relative velocity of the target object based on a phase difference between the beat signal generated from the transmission signal and the reception signal, the chirp signal including chirp signals of a plurality of cycles.

Thus, for example, the relative velocity of the target object can be calculated more easily based on the phase difference of the beat signals than in the case where the relative velocity is estimated based on the change in the beat frequency at the time of the rise and the fall of the frequency.

Description of the reference numerals

1 … radar device, 2 … transmission system (transmitter), 3 … transmission antenna, 4 … power amplifier, 5 … local oscillator, 6 … reception system (receiver), 7 … reception antenna, 8 … mixer, 9 … ADC, 10 … signal processing unit.