JP2005134253A - Radar system, target measuring method for radar system, and target measuring program therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the distance to a target with ease and precision in a simple structure. <P>SOLUTION: A radar system 100 performs a sending operation which transmits a modulated wave signal to a target, and a receiving operation which receives the modulated wave signal reflected from the target by time sharing with a switch period. A receiving sensitivity generation part 104 generates the receiving sensitivity of the output signal from a receiving part 102. A timing changing part 105 changes the operation timing of transmitting and receiving operation by which time sharing is carried out so that a null point may be generated. Whenever a relative delay time calculation part 106 changes operation timing, it computes relative delay time τ showing the relative time difference of a sending operation and a receiving operation. A relative delay time extraction part 109 extracts a relative delay time τs when a null point is generated. A distance calculation part 110 computes the distance to a target from a switch period and operation timing when a null point is generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radar apparatus for measuring a distance from a target, a target measurement method for the radar apparatus, and a target measurement program for the radar apparatus.

  The on-vehicle radar device measures and detects the distance from the target preceding vehicle, determines the risk of rear-end collision, and alerts the driver. Such an on-vehicle radar device is required to be miniaturized in order to be mounted on a vehicle. Therefore, in order to satisfy the above-described demands for miniaturization or cost reduction, an FM-CW radar type radar apparatus having a simple device configuration has been conventionally provided (for example, see Patent Document 1).

  The radar apparatus of the FM-CW radar system of Patent Document 1 transmits a frequency modulation signal, receives a signal reflected by the target object, and mixes it with the transmission signal to obtain the distance of the target object and Get the relative speed. A single antenna is used, and transmission and reception are performed in a time division manner.

  On the other hand, recent FM-CW radar system radar devices are required to have high precision in short-distance measurement in order to further reduce accidents and ensure safety in addition to the demand for miniaturization. In particular, in-vehicle radar devices are required to have a high distance accuracy δR for a short-range target in order to add a stop-and-go function for controlling the inter-vehicle distance at a low speed and a short interval as in a traffic jam.

When short-range distance accuracy is required, the FM-CW radar device of Patent Document 1 described above needs to increase the frequency shift ΔF shown in the following equation (1) in order to increase the distance accuracy. Distance accuracy is also related to beat frequency measurement. The distance accuracy δR is expressed by the measurement resolution δfr of the beat frequency fr,
δR = (C / (4 · fm · ΔF)) δfr (1)
(Where C is the speed of light and fm is the modulation frequency)
It becomes.

The measurement resolution δfr differs depending on the beat frequency measurement method, but when measuring the frequency by normal FFT analysis, one cycle of the beat signal is required within 1 / (2 · fm), and the beat frequency is the minimum frequency. Measured by an integer multiple of. Therefore, δfr = 2 · fm, and when the distance accuracy δR is obtained from the above equation (1),
δR = C / (2 · ΔF) (2)
It becomes. When ΔF = 100 [MHz], δR = 1.5 [m] (± 0.75 [m]).

Japanese Patent Laid-Open No. 9-243738

  However, according to the 76-GHz radar standard in the FM-CW system, various radar systems are approved, and even a stationary target can be measured with a relatively simple distance and speed. There was a problem that the performance of the distance resolution deteriorated. Also, in the equation for measuring the distance by sweeping the transmission / reception switch frequency and detecting the drop of the beat signal level (null point), the transmission / reception switch frequency becomes high at a very short distance, and the switch frequency is 0.5 [m]. However, there is a problem that it becomes impossible to put into practical use because it becomes a transmission pulse with a high repetition frequency and exceeds the legal limit of the occupied bandwidth.

Also, in other types of radar, for example, the pulse method has a problem that the pulse width Tw becomes narrow at a short distance, and the transceiver and the antenna have a wide band. For example, the minimum detection distance Rmin is
Rmin = C · Tw / 2 (3)
It becomes. Here, the relationship between the pulse width Tw and the bandwidth B is
B≈2 / Tw (4)
Therefore, if the minimum detection distance Rmin is Rmin = 0.5 [m], the bandwidth B is 600 [MHz], which requires a broadband radar transceiver and a broadband antenna, which is expensive. there were.

  In addition, if the pulse width is narrow, the transmission spectrum will be widened, and the bandwidth B will exceed the legal limit of the occupied bandwidth (500 [MHz] in Japan), and there is a problem in distance measurement. was there.

  On the other hand, in the pulse radar system, an antenna can be shared because transmission and reception are performed by time division. However, since a narrow pulse width, high-speed rising and falling characteristics are required at a short distance, a transmission modulation system and a receiving system are required. There was a problem that the performance improvement of the configuration was inevitable.

  The 2-frequency CW system is a system that switches between two frequencies, detects a Doppler signal from a target, and measures the distance from the phase difference of each Doppler signal of 2 frequencies, and is almost the same as the FM-CW system. It is a configuration. However, when there is no relative speed between the target and the radar, there is a problem that there is no Doppler signal and the distance cannot be measured. In particular, when controlling the inter-vehicle distance at a low speed and at a short interval, such as when a car is congested, the problem is remarkable.

  In order to solve the above-described problems caused by the prior art, the present invention can easily and accurately measure a distance to a target with a simple configuration, a target measurement method for the radar apparatus, and a target for the radar apparatus. The purpose is to provide a measurement program.

  In order to solve the above-described problems and achieve the object, a radar apparatus, a radar apparatus target measurement method, and a radar apparatus target measurement program according to the present invention include: a transmission operation for transmitting a modulated wave signal to a target; A radar apparatus, a target measurement method for a radar apparatus, and a target measurement program for a radar apparatus, which perform time-division with a predetermined switch cycle, and a reception operation for receiving the modulated wave signal reflected from the target, The reception sensitivity of the modulated wave signal is generated, and the operation timing of the time-division transmission / reception operation is changed so that a null point indicating that the generated reception sensitivity is insensitive is generated, The distance to the target based on the switch period and the operation timing of the transmission / reception operation changed when the null point occurs. And calculates a.

  According to the present invention, by calculating the propagation delay time from when the modulated wave signal is transmitted to when it is reflected by the target and received by forcing the reception sensitivity into the insensitive state and generating a null point. Can do.

  According to the radar apparatus, the radar apparatus target measurement method, and the radar apparatus target measurement program according to the present invention, the distance to the target can be easily and accurately measured with a simple configuration.

  Exemplary embodiments of a radar device, a radar device target measurement method, and a radar device target measurement program according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment)
First, the functional configuration of the radar apparatus according to the embodiment of the present invention will be described. FIG. 1 is a block diagram showing a functional configuration of a radar apparatus according to an embodiment of the present invention. The radar apparatus 100 includes a transmission unit 101, a reception unit 102, a transmission / reception operation control unit 103, a reception sensitivity generation unit 104, a timing change unit 105, a relative delay time calculation unit 106, a storage unit 107, a null The point detection unit 108, the relative delay time extraction unit 109, and the distance calculation unit 110 are configured.

  The transmitting unit 101 transmits the modulated wave signal to the target at a predetermined pulse period. The receiving unit 102 receives the modulated wave signal reflected from the target at a predetermined pulse period. The transmission / reception operation control unit 103 controls the transmission operation of the transmission unit 101 and the reception operation of the reception unit 102. Specifically, control is performed so that the transmission operation for transmitting the modulated wave signal to the target and the reception operation for receiving the modulated wave signal reflected from the target are performed in a time division manner.

  The reception sensitivity generation unit 104 generates reception sensitivity (signal level) of the output signal output from the reception unit 102. Specifically, the signal level of the beat signal output from the receiving unit 102 and the signal level of the amplitude signal subjected to amplitude detection can be generated as reception sensitivity. This reception sensitivity can be expressed by a voltage value, for example.

  The timing changing unit 105 changes the operation timing of the transmission / reception operation that is time-divisioned so that a null point that indicates that the reception sensitivity generated by the reception sensitivity generation unit 104 is insensitive is generated. Specifically, as will be described later, the operation timing of the transmission / reception operation is changed by sliding either one of the transmission operation waveform representing the transmission operation or the reception operation waveform representing the reception operation.

  The relative delay time calculation unit 106 calculates a relative delay time τ that represents a relative time difference between the transmission operation and the reception operation every time the timing change unit 105 changes the operation timing of the transmission / reception operation. Specifically, this relative delay time τ is based on the start time of the transmission operation when either one of the transmission operation waveform representing the transmission operation or the reception operation waveform representing the reception operation is slid. This is the time until the start time of the received operation. When the relative delay time τ coincides with the time when the actual reception operation of the modulated wave signal is OFF, the reception sensitivity of the receiving unit 102 becomes insensitive and a null point is generated.

  The storage unit 107 stores the reception sensitivity generated by the reception sensitivity generation unit 104 and the relative delay time τ corresponding to the reception sensitivity. The null point detection unit 108 compares the reception sensitivities stored in the storage unit 107, and detects a null point that indicates that the reception sensitivity of the modulated wave signal received within the operation time of the reception operation is insensitive. To do. Specifically, a predetermined threshold value is set, and the reception sensitivity that is equal to or lower than the threshold value is detected as a null point.

  The relative delay time extraction unit 109 extracts the relative delay time τs when a null point occurs from the relative delay time τ stored in the storage unit 107. Specifically, the relative delay time τs is the relative delay time τ corresponding to the null point detected by the null point detection unit 108.

  The distance calculation unit 110 calculates the distance to the target based on the predetermined switch cycle and the operation timing of the transmission / reception operation changed by the timing change unit 105 when the null point occurs. Specifically, the distance to the target is calculated based on a predetermined switch cycle and the relative delay time τs when the null point is extracted, which is extracted by the relative delay time extraction unit 109. Details of the calculation method will be described later.

  Next, an example of the hardware configuration of the radar apparatus 100 according to the embodiment of the present invention will be described. FIG. 2 is an explanatory diagram showing an example of a hardware configuration of the radar apparatus 100 according to the embodiment of the present invention.

  The radar apparatus 100 includes a clock oscillator 201, a triangular wave generation circuit 202, a high frequency voltage variable oscillator (VCO) 203, a transmission switch 204, and a transmission antenna 205. The clock oscillator 201 outputs a predetermined clock signal. The triangular wave generation circuit 202 outputs a triangular wave synchronized with the clock signal from the clock oscillator 201. The voltage variable oscillator 203 frequency-modulates the triangular wave output from the triangular wave generation circuit 202 and outputs a frequency-modulated signal. The voltage variable oscillator 203 is connected to the first mixer 213 of the receiving unit 102, and outputs a part of the frequency-modulated signal to the first mixer 213. The transmission switch 204 outputs a frequency-modulated signal to the transmission antenna 205 when the transmission driver 222 is opened and closed. The transmitting antenna 205 transmits the switched frequency modulated signal as a modulated wave signal toward the target. The clock oscillator 201, the triangular wave generation circuit 202, the voltage variable oscillator 203, the transmission switch 204, and the transmission antenna 205 constitute the transmission unit 101 shown in FIG.

  The radar apparatus 100 includes a reception antenna 211, a reception switch 212, a first mixer 213, a band pass filter (BPF) 214, and a second mixer 215. The receiving antenna 211 receives the modulated wave signal reflected from the target. The reception switch 212 outputs the modulated wave signal received by the reception antenna 211 by the opening / closing drive of the reception driver 223 to the first mixer 213. The first mixer 213 mixes outputs from the voltage variable oscillator 203 and the receiving antenna 211 and outputs an intermediate frequency signal. The band pass filter 214 passes the intermediate frequency signal from the first mixer 213 in a predetermined band. The second mixer 215 mixes the intermediate frequency signal that has passed through the band-pass filter 214 and the local oscillation signal output from the switch drive signal source (LO) 221 and converts the frequency to output a beat signal. . The reception antenna 211, the reception switch 212, the first mixer 213, the band pass filter 214, and the second mixer 215 constitute the reception unit 102 illustrated in FIG.

  Further, the radar apparatus 100 includes a switch drive signal source 221, a transmission driver 222, and a reception driver 223. The switch drive signal source 221 outputs a drive pulse signal that drives the transmission driver 222 and the reception driver 223 in accordance with a command from the signal processing unit 230. This drive pulse signal can drive the transmission driver 222 and the reception driver 223 independently at a predetermined period, and can control the opening / closing time of the transmission switch 204 and the opening / closing time of the reception switch 212. A part of the drive pulse signal is input to the second mixer 215 as a local signal. The switch drive signal source 221, the transmission driver 222, and the reception driver 223 constitute the transmission / reception operation control unit 103 shown in FIG.

  The signal processing unit 230 includes an A / D converter 231, a fast Fourier transformer (FFT) 232, a CPU 233, a ROM 234, a RAM 235, an output I / F 236, and a bus 237 connecting them. ing. The A / D converter 231 digitally converts the output signal from the second mixer 215. The fast Fourier transformer 232 performs a fast Fourier transform on the digitized beat signal from the second mixer 215 to generate a signal level of a frequency component proportional to the distance of the beat signal. The CPU 233 controls the entire signal processing unit 230. Various programs are stored in the ROM 234. The RAM 235 is used as a work area of the CPU 233 and stores a signal level of a frequency component that is proportional to the distance of the beat signal generated by the fast Fourier transformer 232. Further, the present invention is not limited to the RAM 235, and may be constituted by a readable / writable recording medium such as an EEPROM, a flash memory, or an HD.

  The signal processing unit 230 includes the reception sensitivity generation unit 104, the timing change unit 105, the relative delay time calculation unit 106, the storage unit 107, the null point detection unit 108, and the relative delay time extraction unit illustrated in FIG. 109 and the distance calculation unit 110. In other words, the reception sensitivity generation unit 104, the timing change unit 105, the relative delay time calculation unit 106, the null point detection unit 108, the relative delay time extraction unit 109, and the distance calculation unit 110 illustrated in FIG. For example, the CPU 233 executes a program recorded in a readable / writable recording medium such as a ROM 234, a RAM 235, an EEPROM, a flash memory, and an HD, thereby realizing the function. Specifically, the storage unit 107 realizes its function by a readable / writable recording medium such as a ROM 234, a RAM 235, an EEPROM, a flash memory, and an HD.

  Next, the principle of distance measurement according to the embodiment of the present invention will be described. FIG. 3 is a timing chart showing the transmission / reception principle according to the embodiment of the present invention, and FIG. 4 is a timing chart in the case where the reception operation waveform is slid and becomes null in the timing chart of FIG. As shown in FIG. 3, when the switch cycle by the transmission / reception operation control is Tsw and the duty ratio of the transmission operation control pulse is 50%, the transmission operation waveform A of the transmission unit 101 is turned on / off by the switch cycle Tsw. The pulse waveform is A reception time waveform B representing the reception time of the modulated wave signal reflected from the target is the same pulse waveform as the transmission operation waveform A, but is delayed from the transmission operation waveform A by a propagation delay time τo. .

  Further, the reception operation waveform C of the reception unit 102 is a pulse waveform having the same cycle as that of the transmission operation waveform A, but is a pulse waveform having a phase opposite to that of the transmission operation waveform A by transmission / reception operation control. Therefore, transmission / reception operations between the transmission unit 101 and the reception unit 102 are performed in a time-sharing manner. Thereby, the actual reception time Ba in which the modulated wave signal can be received coincides with the propagation delay time τo.

  As shown in FIG. 4, when the reception operation waveform C is slid by the actual reception time Ba by the timing changing unit 105, the reception unit 102 becomes insensitive (null) when the reception time Ba disappears. . Therefore, the propagation delay time τo that coincides with the actual reception time Ba can be calculated by detecting the point that becomes insensitive (null), that is, the null point.

  In order to calculate the propagation delay time τo, as shown in FIG. 4, the relative delay time τs, which is the time from when the transmission operation waveform A rises to when the reception operation waveform C rises when a null point occurs, is generated. Need to be detected. The modulated wave signal reflected from the target at a certain distance can be selected to have the lowest sensitivity by sliding the relative delay time τs of the transmission operation and the reception operation.

Here, calculation of radar propagation delay time τo and distance R will be described. When the distance to the target is R [m] and the speed of light is c [m / s], the propagation delay time τo of the radar is
τo = 2R / c (5)
It is. Also, as shown in FIG. 4, when the reception time waveform B and the reception operation waveform C are in opposite phases, the reception sensitivity of the reception unit 102 becomes insensitive (null), and therefore the distance Rn that becomes insensitive. From the above equation (5),
Rn = c · τo / 2 (6)
Can be represented.

Further, as shown in FIG. 4, the relative delay time τs when this null point occurs is the time from the rise of the transmission operation waveform A to the rise of the reception operation waveform C within one switch cycle Tsw. , Propagation delay time τo is
τo = τs−Tsw / 2 (7)
The distance Rn at which the insensitive state is obtained can be expressed as
Rn = c · (τs−Tsw / 2) / 2 (8)
Can be represented.

Even if this propagation delay time τo becomes longer than the switch period Tsw, a dead state (null) occurs. For this reason, when the propagation delay time τo exceeds the switch period Tsw, assuming that the integer part of τo / Tsw indicating the number of periods is n, the distance Rn in which the insensitive state is obtained is
Rn = {n · c · (τs−Tsw / 2)} / 2 (9)
Can be represented.

  FIG. 5 shows an example of the relationship between the signal level (reception power) Pr and the distance R when a target at a short distance is received. The vertical axis of this graph represents received power Pr. Here, null occurs at the target distance of 8.03 [m]. The propagation delay time τo is τo = 5.35 [ns], the target reflection sectional area σ is σ = 10 [dBm], the transmission power Pt is 0 [dBm], and the antenna gain G is G = 30.9 [dB]. It is. The received power when the target distance is changed with the relative delay time τs that becomes null at a distance of 8.03 [m] is shown.

  According to this graph, at the distance of about 8.03 [m], the drop of the received power Pr becomes large, and this distance becomes the distance to the near target in the insensitive state, and the characteristics of the spatial filter are sharp. I understand. Therefore, the modulated wave signal reflected from the target can be eliminated by the steep spatial filter, and the distance can be measured from the relationship between the spatial filter elimination time delay and the distance.

  FIG. 6 is an explanatory diagram showing changes in the reception level from the target when the relative delay time of the transmission / reception operation of the radar apparatus according to the embodiment of the present invention is swept in a sawtooth shape. This sweep is executed by the null point detector 108 described above. When the target is single, the switch cycle Tsw is constant, and the relative delay time τ becomes the relative delay time τs when the null point N occurs, the reception sensitivity decreases to the minimum sensitivity level Pn, and the dead state (null) It becomes. In other words, a steep BEF (Band Elimination Filter) is equivalently inserted.

  That is, the transmission modulated wave signal is received with a delay of the propagation delay time τo, and at the same time, the reception time waveform B and the reception operation waveform C of the modulated wave signal are out of phase with each other (see FIG. 4). As shown in FIG. 6, a null point N at which the reception sensitivity becomes the minimum sensitivity level Pn occurs in each search section. By comparing the reception sensitivity (minimum sensitivity level Pn) of the null point N with the reception sensitivity before and after the occurrence of the null point, the relative delay time τs when the null point N occurs can be extracted. Therefore, the distance Rn to the target can be calculated from the above equation (8) based on the relative delay time τs at the minimum sensitivity level Pn representing the insensitive state (null).

  Next, the target measurement processing procedure of the radar apparatus 100 according to the embodiment of the present invention will be described. FIG. 7 is a flowchart showing a target measurement processing procedure of the radar apparatus 100 according to the embodiment of the present invention. The transmission switch 204 is opened and closed at a constant switch cycle Tsw, and a rectangular pulse modulated wave signal is transmitted. At the same time, the reception switch 212 is opened and closed so as to be in reverse phase with the transmission switch 204, and a reception operation for detecting the reception level is started (step S701). Then, reception of this reflected echo (modulated wave signal) is detected, and reception sensitivity is generated (step S702).

  In the case of radar, reflection levels from the ground, raindrops, and the like are also received. Therefore, in order to eliminate these as noise, it is determined whether or not the reception sensitivity is a signal level equal to or higher than a predetermined set level. When it is less than the set level (step S703: No), the process proceeds to step S701. When the level is equal to or higher than the set level (step S703: Yes), the reception operation waveform C is slid by a predetermined delay change amount (step S704).

  Then, the relative delay time τ is calculated from the delay amount at the time of sliding (step S705), and the relative delay time τ and the reception sensitivity are stored in pairs (step S706). Next, it is determined whether or not the number of slides has reached a predetermined number (step S707). If not reached (step S707: No), the process proceeds to step S704. When it arrives (step S707: Yes), the relative delay time τ is swept, and the null point N is searched from the reception sensitivity for each relative delay time τ stored in step S706 (step S708). When the null point N is not detected (step S709: No), the process returns to step S701.

  When the null point N is detected (step S709: Yes), the relative delay time τs corresponding to the detected null point N is extracted (step S710). Then, based on the extracted relative delay time τs and the switch period Tsw, the propagation delay time τo is calculated from the above equation (7) (step S711). Then, the distance Rn to the target is calculated by the above equation (6) (step S712). Thereafter, the process returns to step S701.

  According to the radar apparatus 100, the distance Rn to the target can be measured by sliding the reception operation waveform C. Therefore, the distance accuracy can be improved as compared with the FM-CW radar device. In addition, since the distance is measured by sliding the switch period instead of the switch frequency, the repetition period can be increased, and the modulated wave signal does not become a steep transmission pulse, unlike the pulse-type radar device. The spectrum does not spread. Thereby, it can suppress within the legal restriction | limiting of an occupied bandwidth, and can aim at practical use. Further, unlike the pulse-type radar apparatus, the transmitter / receiver and the antenna do not have a wide band, and the radar apparatus can be made inexpensive. Even when there is no relative speed with the target, the distance to the target can be measured.

(Other configuration examples of radar equipment)
Next, another configuration example of the radar apparatus according to the embodiment of the present invention will be described. FIG. 8 is a block diagram showing a hardware configuration of another configuration example of the radar apparatus according to the embodiment of the present invention. The radar apparatus 800 shown in FIG. 8 transmits a modulated wave signal as an AM modulated wave signal, and the signal level obtained by receiving the AM modulated wave signal is used as an amplitude component of the AM modulated wave signal. It is the composition obtained from. In addition, the same code | symbol is attached | subjected about the same structure as the structure shown in FIG. 2, and the description is abbreviate | omitted.

  As shown in FIG. 8, the radar apparatus 800 includes an RF oscillator 801, a low-frequency oscillator 802, an AM modulator 803, a first amplifier 804, a transmission switch 204, and a transmission antenna 205. . The RF oscillator 801 outputs a high-frequency carrier signal to the AM modulator 803. The low frequency oscillator 802 outputs a low frequency oscillation signal to the AM modulator 803. The low frequency oscillator 802 changes the modulation frequency of the low frequency oscillation signal according to the control signal from the signal processing unit 830. The AM modulator 803 modulates the amplitude of the high frequency carrier signal with the low frequency oscillation signal and outputs an AM modulated wave signal. The first amplifier 804 amplifies the AM modulated wave signal. The amplified AM modulated wave signal is transmitted from the transmission antenna 205 via the transmission switch 204. The RF oscillator 801, low frequency oscillator 802, AM modulator 803, first amplifier 804, transmission switch 204, and transmission antenna 205 constitute the transmission unit 101 shown in FIG.

  The radar apparatus 800 includes a reception antenna 211, a reception switch 212, a second amplifier 811, an amplitude detector 812, a frequency variable bandpass filter 813, and a third amplifier 814. The second amplifier 811 amplifies the AM modulated wave signal input via the reception antenna 211 and the reception switch 212 by being reflected from the target. The amplitude detector 812 performs envelope detection of the AM modulated wave signal amplified by the second amplifier 811, and outputs a modulation component signal in addition to the direct current component. The frequency variable bandpass filter 813 is controlled by the signal processing unit 830 so as to be tuned to the modulation frequency of the low frequency oscillator 802, and selectively passes the AM-modulated wave signal detected from the amplitude detector 812, and the noise Remove ingredients. The third amplifier 814 amplifies the AM modulated wave signal that has passed through the frequency variable bandpass filter 813 and outputs the amplified signal to the signal processing unit 830. The reception antenna 211, the reception switch 212, the second amplifier 811, the amplitude detector 812, the frequency variable bandpass filter 813, and the third amplifier 814 constitute the reception unit 102 illustrated in FIG.

  The signal processing unit 830 includes an A / D converter 831, a CPU 233, a ROM 234, a RAM 235, an output I / F 236, and a bus 237 that connects them. The A / D converter 831 digitally converts the amplitude signal from the third amplifier 814. The RAM 235 is used as a work area for the CPU 233 and stores the amplitude signal digitally converted by the A / D converter 831. The signal processing unit 830 outputs a control signal for changing the modulation frequency of the low-frequency oscillator 802 to the low-frequency oscillator 802, and changes the pass center frequency of the frequency variable bandpass filter 813 to modulate the low-frequency oscillator 802. Control to tune with frequency.

  The signal processing unit 830 includes a reception sensitivity generation unit 104, a timing change unit 105, a relative delay time calculation unit 106, a storage unit 107, a null point detection unit 108, and a relative delay time extraction unit illustrated in FIG. 109 and the distance calculation unit 110. In other words, the reception sensitivity generation unit 104, the timing change unit 105, the relative delay time calculation unit 106, the null point detection unit 108, the relative delay time extraction unit 109, and the distance calculation unit 110 illustrated in FIG. For example, the CPU 233 executes a program recorded in a readable / writable recording medium such as a ROM 234, a RAM 235, an EEPROM, a flash memory, and an HD, thereby realizing the function. Specifically, the storage unit 107 realizes its function by a readable / writable recording medium such as a ROM 234, a RAM 235, an EEPROM, a flash memory, and an HD.

  Similarly to the radar apparatus 100 shown in FIG. 2 described above, this radar apparatus 800 can detect the null point N by sliding the operation waveform and easily measure the distance to the target. Therefore, the same effect as that of the radar apparatus 100 shown in FIG. 2 can be obtained by using the AM modulated wave signal.

(Another configuration example of radar device)
Next, another configuration example of the radar apparatus according to the embodiment of the present invention will be described. FIG. 9 is a block diagram showing a hardware configuration of another configuration example of the radar apparatus according to the embodiment of the present invention, and FIG. 10 is a timing chart thereof. 2 and 8 are denoted by the same reference numerals, and description thereof is omitted. The radar apparatus 900 having this configuration is configured to have both the FM-CW radar system and the functions of the radar apparatus 800 described above.

  The radar apparatus 900 includes a clock oscillator 201, a triangular wave generation circuit 202, a high-frequency voltage variable oscillator 203, a transmission amplifier 901, and a transmission antenna 205. The transmission amplifier 901 switches ON / OFF between the voltage variable oscillator 203 and the transmission antenna 205. The transmission amplifier 901 amplitude-modulates the RF frequency modulated wave signal that has been frequency-modulated by the triangular wave generation circuit 202 and the voltage variable oscillator 203. The clock oscillator 201, the triangular wave generation circuit 202, the voltage variable oscillator 203, the transmission amplifier 901, and the transmission antenna 205 constitute the transmission unit 101 shown in FIG.

  The radar apparatus 900 includes a reception antenna 211, a reception amplifier 911, a first mixer 213, a band pass filter 214, a second mixer 215, and a frequency variable band pass filter 813. The reception amplifier 911 switches ON / OFF between the reception antenna 211 and the first mixer 213. The reception antenna 211, the reception amplifier 911, the first mixer 213, the band pass filter 214, the second mixer 215, and the frequency variable band pass filter 813 constitute the reception unit 102 shown in FIG.

  The radar apparatus 900 further includes a low frequency oscillator 801, a switch drive signal source 221, a transmission driver 222, and a reception driver 223. The low frequency oscillator 801 outputs a predetermined sine wave signal as a subcarrier. The sine wave signal is input to the transmission driver 222. The sine wave signal is superimposed on a pulse waveform with a duty ratio of 50%, and the transmission amplifier 901 is driven by an ON / OFF switch.

  As a result, the RF frequency modulated wave signal frequency-modulated by the triangular wave generation circuit 202 and the voltage variable oscillator 203 is amplitude-modulated by the transmission amplifier 901 and transmitted from the transmission antenna 205 as a modulated wave signal. Therefore, the modulated wave signal transmitted from the transmitting antenna 205 includes a frequency modulation component (RF modulated wave signal to be modulated) and an amplitude modulation component. The low-frequency oscillator 801, the switch drive signal source 221, the transmission driver 222, and the reception driver 223 constitute the transmission / reception operation control unit 103 shown in FIG.

  In addition, the reception antenna 211, the reception amplifier 911, and the first mixer 213 that form the reception unit 102 receive the modulated wave signal. The frequency modulation component included in the received modulated wave signal is output as an intermediate frequency signal, and the amplitude modulation component included in the received modulated wave signal is also output. That is, the band pass filter 214 selects the intermediate frequency signal and outputs it to the signal processing unit 930, and the frequency variable band pass filter 813 selects the amplitude modulation component and outputs it to the signal processing unit 930.

  The signal processing unit 930 of the radar apparatus 900 includes an A / D converter 231, a fast Fourier transformer 232, an A / D converter 831, a CPU 233, a ROM 234, a RAM 235, and an output I / F 236. , And a bus 237 connecting them. The signal processing unit 930 includes the reception sensitivity generation unit 104, the timing change unit 105, the relative delay time calculation unit 106, the storage unit 107, the null point detection unit 108, and the relative delay time extraction unit illustrated in FIG. 109 and the distance calculation unit 110. In other words, the reception sensitivity generation unit 104, the timing change unit 105, the relative delay time calculation unit 106, the storage unit 107, the null point detection unit 108, the relative delay time extraction unit 109, which are illustrated in FIG. Specifically, the distance calculation unit 110 realizes its function by causing the CPU 233 to execute a program recorded on a readable / writable recording medium such as a ROM 234, a RAM 235, an EEPROM, a flash memory, or an HD. Specifically, the storage unit 106 realizes its function by a readable / writable recording medium such as a ROM 234, a RAM 235, an EEPROM, a flash memory, and an HD.

  The operation of the radar apparatus 900 will be described with reference to FIGS. 9 and 10. The low frequency oscillator 801 outputs a predetermined sine wave signal S 1 to the transmission driver 222. The switch drive signal source 221 outputs a drive signal S2 to the transmission driver 222 and the reception driver 223. The transmission driver 222 superimposes the sine wave signal output from the low frequency oscillator 801 on the drive signal S2 output from the switch drive signal source 221, and turns on the transmission amplifier 901 by the pulse waveform S3 with a duty ratio of 50%. Drives OFF. Similarly, the reception driver 223 outputs a pulse waveform S6 with a duty ratio of 50% obtained by sliding the drive signal S2 output from the switch drive source 221 with a control signal from the signal processing unit 930. This pulse waveform S6 drives the receiving amplifier 911 ON / OFF.

  As a result, a modulated RF carrier pulse signal S4 obtained by amplitude-modulating the modulated RF frequency-modulated signal frequency-modulated by the triangular wave generating circuit 202 and the voltage variable oscillator 203 by the transmission amplifier 901 is transmitted from the transmission antenna 205. The modulated RF carrier pulse signal S4 is reflected by the target, and is received by the reception antenna 211 as a reception waveform S5 after a propagation delay time τo proportional to the propagation distance.

  The received reception waveform S5 is amplified by the reception amplifier 911 for the time when the reception driver 223 is ON, and the reception signal S7 is input to the first mixer 213. The first mixer 213 mixes a part of the RF frequency modulated wave signal frequency-modulated by the voltage variable oscillator 203 and the received waveform S7, and generates and outputs an intermediate frequency signal of the difference frequency component. At the same time, a detection signal S8, which is a low-frequency signal component of the reception signal S7, is generated and output by the amplitude detection action of the first mixer 213.

  The intermediate frequency signal output from the first mixer 213 is input to the band pass filter 214 and the frequency variable band pass filter 813. The bandpass filter 214 outputs the intermediate frequency component of the intermediate frequency signal to the second mixer 215 by passing the intermediate frequency signal in a predetermined band. The intermediate frequency component and the local oscillation signal output from the switch drive signal source 221 are mixed, and a beat signal proportional to the propagation distance is obtained by the A / D converter 231 and the fast Fourier transformer 232 in the signal processing unit 930. Is stored in the RAM 235.

  On the other hand, the frequency variable bandpass filter 813 is controlled by the signal processing unit 930 so as to be tuned to the modulation frequency of the transmission amplifier 901. Then, the amplitude detection function of the first mixer 213 selectively passes the low-frequency modulation amplitude component input from the first mixer 213, and the amplitude digitally converted by the A / D converter 831 of the signal processing unit 930 A signal is generated and stored in the RAM 235 together with the relative delay time τ at this time. Then, according to the processing procedure shown in FIG. 7 described above, the distance Rn to the target is calculated based on the digitized amplitude signal of the low frequency modulation component stored in the RAM 235 and the corresponding relative delay time τ. .

  Therefore, according to the radar apparatus 900, the distance can be detected from the beat signal included in the intermediate frequency by the operation of the FM-CW method, so that the sensitivity is high and the target at a long distance can be detected. Further, by delaying the driving waveform of the reception amplifier with reference to the transmission pulse waveform, the target distance at a short distance can be detected with high accuracy by the null point at which the detected amplitude signal is the lowest.

  In the above-described embodiment, the null point N is generated by sliding the reception operation waveform C. However, the null point N can also be generated by sliding the transmission operation waveform A. .

  The target measurement method described in this embodiment can be realized by executing a program prepared in advance on a computer such as a personal computer or a workstation. This program is recorded on a computer-readable recording medium such as a hard disk, a flexible disk, a CD-ROM, an MO, and a DVD, and is executed by being read from the recording medium by the computer. The program may be a transmission medium that can be distributed via a network such as the Internet.

(Supplementary Note 1) A radar apparatus that performs a transmission operation for transmitting a modulated wave signal to a target and a reception operation for receiving the modulated wave signal reflected from the target in a time-sharing manner with a predetermined switch period. There,
Receiving sensitivity generating means for generating receiving sensitivity of the modulated wave signal;
Timing changing means for changing the operation timing of the time-division transmission / reception operation so that a null point indicating that the reception sensitivity generated by the reception sensitivity generation means is insensitive is generated;
Distance calculating means for calculating a distance to the target based on the predetermined switch period and the operation timing of the transmission / reception operation changed by the timing changing means when the null point occurs;
A radar apparatus comprising:

(Supplementary Note 2) The timing changing means may generate the null point by sliding one of the transmission operation waveform representing the transmission operation and the reception operation waveform representing the reception operation. The radar apparatus according to appendix 1, wherein the operation timing of the transmission / reception operation that is time-division is changed.

(Appendix 3) Relative delay time calculating means for calculating a relative delay time representing a relative time difference between the transmission operation and the reception operation every time the operation timing of the transmission / reception operation is changed by the timing changing means;
Relative delay time extraction means for extracting the relative delay time when the null point occurs from the relative delay time calculated by the relative delay time calculation means,
With
The distance calculating means calculates a distance to the target based on the predetermined switch cycle and a relative delay time extracted by the relative delay time extracting means when the null point occurs. The radar apparatus according to appendix 1 or 2, characterized by:

(Appendix 4) Transmitting means for modulating the amplitude of the modulated wave signal with a signal having a predetermined modulation frequency and transmitting the modulated wave signal;
Receiving means for receiving the modulated wave signal transmitted from the transmitting means, selecting an amplitude modulation component from the received modulated wave signal, and detecting the amplitude;
With
The reception sensitivity generation unit generates the reception sensitivity of the modulated wave signal based on the amplitude modulation component amplitude-detected by the reception unit. Radar device.

(Supplementary Note 5) Transmitting means for amplitude-modulating a predetermined frequency modulation signal and transmitting it as the modulated wave signal;
Receives the modulated wave signal transmitted from the transmission means, generates a beat signal from the frequency modulation component included in the received modulated wave signal, and amplitude modulation included in the modulated wave signal Receiving means for amplitude detection of the component;
With
Any one of Supplementary notes 1 to 3, wherein the reception sensitivity generation unit generates reception sensitivity of the modulated wave signal based on a beat signal generated by the reception unit or an amplitude-modulated component subjected to amplitude detection. A radar device according to any one of the above.

(Supplementary Note 6) A radar apparatus that performs a transmission operation for transmitting a modulated wave signal to a target and a reception operation for receiving the modulated wave signal reflected from the target in a time division manner with a predetermined switch period. A target measurement method,
A reception sensitivity generation step of generating reception sensitivity of the modulated wave signal;
A timing changing step for changing the operation timing of the transmission / reception operation that is time-divisioned so that a null point indicating that the reception sensitivity generated by the reception sensitivity generation step is in a dead state occurs;
A distance calculating step of calculating a distance to the target based on the predetermined switch cycle and the operation timing of the transmission / reception operation changed by the timing changing step when the null point occurs;
A method for measuring a target of a radar apparatus, comprising:

(Supplementary note 7) A radar apparatus that performs a transmission operation for transmitting a modulated wave signal to a target and a reception operation for receiving the modulated wave signal reflected from the target in a time division manner with a predetermined switch period. A target measurement program,
A reception sensitivity generation step of generating reception sensitivity of the modulated wave signal;
A timing changing step for changing the operation timing of the transmission / reception operation that is time-divisioned so that a null point that indicates that the reception sensitivity generated by the reception sensitivity generation step is in a dead state occurs;
A distance calculating step of calculating a distance to the target based on the predetermined switch period and the operation timing of the transmission / reception operation changed by the timing changing step when the null point occurs;
A program for measuring a target of a radar apparatus, characterized in that a computer is executed.

  As described above, the radar apparatus, the radar apparatus target measurement method, and the radar apparatus target measurement program according to the present invention are, for example, a vehicle-mounted radar apparatus, a radar apparatus target measurement method, and a radar apparatus target measurement program. Suitable for

It is a block diagram which shows the functional structure of the radar apparatus concerning embodiment of this invention. It is a block diagram which shows an example of the hardware constitutions of the radar apparatus concerning embodiment of this invention. It is a timing chart which shows the transmission / reception principle of the radar apparatus concerning embodiment of this invention. FIG. 4 is a timing chart when the reception operation waveform is slid and becomes null in the timing chart of FIG. 3. It is a graph which shows the example of the spatial filter calculation of the radar apparatus concerning embodiment of this invention. It is explanatory drawing which shows the change of the reception level from a target when the relative delay time of the transmission / reception operation of the radar apparatus concerning embodiment of this invention is swept like a sawtooth wave. It is a flowchart which shows the target measurement process sequence of the radar apparatus concerning embodiment of this invention. It is a block diagram which shows the other example of the hardware constitutions of the radar apparatus concerning embodiment of this invention. It is a block diagram which shows another example of the hardware constitutions of the radar apparatus concerning embodiment of this invention. FIG. 10 is a timing chart showing signal waveforms in the radar apparatus shown in FIG. 9. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Radar apparatus 101 Transmission part 102 Reception part 103 Transmission / reception operation control part 104 Reception sensitivity production | generation part 105 Timing change part 106 Relative delay time calculation part 107 Storage part 108 Null point detection part 109 Relative delay time extraction part 110 Distance calculation part

Claims (5)

A radar apparatus that performs a transmission operation for transmitting a modulated wave signal to a target and a reception operation for receiving the modulated wave signal reflected from the target in a time division manner with a predetermined switch period,
Receiving sensitivity generating means for generating receiving sensitivity of the modulated wave signal;
Timing changing means for changing the operation timing of the time-division transmission / reception operation so that a null point indicating that the reception sensitivity generated by the reception sensitivity generation means is insensitive is generated;
Distance calculating means for calculating a distance to the target based on the predetermined switch period and the operation timing of the transmission / reception operation changed by the timing changing means when the null point occurs;
A radar apparatus comprising:   The timing changing means is time-divisioned so that the null point is generated by sliding either one of a transmission operation waveform representing the transmission operation or a reception operation waveform representing the reception operation. The radar apparatus according to claim 1, wherein the operation timing of the transmitting / receiving operation is changed. Relative delay time calculation means for calculating a relative delay time representing a relative time difference between the transmission operation and the reception operation each time the operation timing of the transmission / reception operation is changed by the timing change means;
Relative delay time extracting means for extracting the relative delay time when the null point occurs from the relative delay time calculated by the relative delay time calculating means,
The distance calculating means calculates a distance to the target based on the predetermined switch cycle and a relative delay time extracted by the relative delay time extracting means when the null point occurs. The radar apparatus according to claim 1, wherein: A radar target measurement method that performs a transmission operation for transmitting a modulated wave signal to a target and a reception operation for receiving the modulated wave signal reflected from the target in a time-sharing manner with a predetermined switch period. There,
A reception sensitivity generation step of generating reception sensitivity of the modulated wave signal;
A timing changing step for changing the operation timing of the transmission / reception operation that is time-divisioned so that a null point indicating that the reception sensitivity generated by the reception sensitivity generation step is in a dead state occurs;
A distance calculating step of calculating a distance to the target based on the predetermined switch cycle and the operation timing of the transmission / reception operation changed by the timing changing step when the null point occurs;
A method for measuring a target of a radar apparatus, comprising: A radar target measurement program that performs a transmission operation for transmitting a modulated wave signal to a target and a reception operation for receiving the modulated wave signal reflected from the target in a time-sharing manner with a predetermined switch period. There,
A reception sensitivity generation step of generating reception sensitivity of the modulated wave signal;
A timing changing step for changing the operation timing of the transmission / reception operation that is time-divisioned so that a null point that indicates that the reception sensitivity generated by the reception sensitivity generation step is in a dead state occurs;
A distance calculating step of calculating a distance to the target based on the predetermined switch period and the operation timing of the transmission / reception operation changed by the timing changing step when the null point occurs;
A program for measuring a target of a radar apparatus, characterized in that a computer is executed.

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