JP7123571B2 - FMCW radar system - Google Patents

Description

The present invention relates to FMCW radar equipment.

2. Description of the Related Art Conventionally, radar devices for detecting obstacles and the like around vehicles are known for use in automatic driving of vehicles and driving support systems. As the number of vehicles equipped with radar devices increases with the spread of autonomous driving and driving support systems, obstacles can be accurately detected by receiving radar signals transmitted from other vehicles' radar devices as interference signals. increased risk of not being able to Therefore, such a radar device is required to detect interference and take appropriate countermeasures when it occurs. In Patent Document 1, an amplitude density of a beat signal obtained by mixing a transmission signal and a reception signal is calculated, and based on this amplitude density, an allowable upper limit and an allowable lower limit of the beat signal are set, thereby An FMCW radar signal processor for detecting and removing static noise is disclosed.

JP-A-7-110373

In the signal processing device of Patent Document 1, the permissible upper limit value and the permissible lower limit value of the beat signal are set on the assumption that the amplitude of the reference beat signal does not fluctuate. However, in a radar device such as a millimeter-wave radar, the phase noise of the transmitter of which is relatively large, the amplitude of the beat signal may fluctuate even if there is no interference. In addition, the level of the signal received by the radar device of the vehicle fluctuates according to changes in the surrounding environment of the vehicle, and accordingly the amplitude of the beat signal also fluctuates. Therefore, with the method described in Patent Document 1, it is difficult to accurately detect a low-level interference signal, and there is room for improvement in interference detection performance. In particular, when broadband interference occurs in which the frequency of the beat signal due to the interference signal varies over a wide band, it may not be possible to effectively suppress it.

An FMCW radar apparatus according to an aspect of the present invention transmits a transmission signal frequency-modulated so that the frequency changes continuously over time, receives a reception signal reflected by an object, and receives a reception signal from the object. and a waveform generator that generates a voltage waveform in which the voltage changes continuously over time; A voltage controlled oscillator for generating the transmission signal in which the frequency continuously changes with time in a downward direction; an amplifier for amplifying the transmission signal; a switch that permits or prohibits output of the transmission signal from an oscillator to the amplifier, wherein the voltage-controlled oscillator has a transmission period in which the frequency continuously changes with time from the transmission start frequency to the transmission end frequency; , and a return period in which the frequency continuously changes with time from the transmission end frequency to the transmission start frequency, and the transmission signal is generated by alternately repeating; the voltage controlled oscillator and the amplifier based on the voltage waveform so as to permit output of the transmission signal to the amplifier and inhibit output of the transmission signal from the voltage controlled oscillator to the amplifier during the return period; Toggles the connection state between
An FMCW radar apparatus according to another aspect of the present invention transmits a transmission signal that is frequency-modulated so that the frequency changes continuously over time, receives a reception signal in which the transmission signal is reflected by an object, and receives the A waveform generator for measuring a distance to an object and for generating a voltage waveform in which the voltage changes continuously over time; and a first voltage controlled oscillator for generating a first transmission signal based on the voltage waveform. and a second voltage controlled oscillator for generating a second transmission signal based on the voltage waveform, the first transmission signal or the second transmission signal being selected, and transmitting from a predetermined transmission start frequency to a predetermined transmission end. a switch for outputting the transmission signal in which the frequency continuously changes with time in an upward or downward direction up to a frequency, wherein the first voltage controlled oscillator outputs the frequency continuously from the transmission start frequency to the transmission end frequency. a transmission period in which the frequency changes continuously with time from the transmission end frequency to the transmission start frequency; and a non-generation period in which no signal is generated. The second voltage-controlled oscillator alternately repeats the transmission period, the return period, and the non-generation period at a timing different from that of the first transmission signal to generate the second transmission signal. A transmission signal is generated, and the switch selects the first transmission signal during the transmission period of the first transmission signal based on the change in the voltage waveform, and selects the first transmission signal during the transmission period of the second transmission signal based on the change in the voltage waveform. Selecting the second transmission signal, between the voltage waveform output by the waveform generator to the first voltage controlled oscillator and the voltage waveform output by the waveform generator to the second voltage controlled oscillator is provided with a predetermined phase difference, and the second voltage controlled oscillator synchronizes with the timing at which the first transmission signal changes from the transmission period to the return period, and the phase of the second transmission signal is In addition to starting the transmission period, the return period of the second transmission signal is started in synchronization with a timing at which the first transmission signal changes from the return period to the transmission period through the non-generation period. , the first voltage-controlled oscillator starts the transmission period of the first transmission signal in synchronization with a timing at which the second transmission signal changes from the transmission period to the return period, The return period of the first transmission signal is started in synchronization with the timing at which the transmission signal of is changed from the return period to the transmission period through the non-generation period.

According to the present invention, the occurrence of broadband interference in FMCW radar equipment can be avoided.

It is a figure which shows the structure of a general FMCW radar apparatus. FIG. 4 is a diagram for explaining the operation of a conventional radar device when there is an interference signal; FIG. 10 is a diagram showing an example of a temporal waveform of a received beat signal when there is an interference signal in a conventional radar device; It is a figure showing composition of a radar installation concerning a 1st embodiment of the present invention. FIG. 4 is a diagram for explaining the operation when there is an interference signal in the radar device according to the first embodiment of the present invention; It is a figure which shows the structure of the radar apparatus which concerns on the 2nd Embodiment of this invention. FIG. 9 is a diagram for explaining the operation of the voltage controlled oscillator in the radar device according to the second embodiment of the present invention; FIG. 9 is a diagram for explaining the operation when there is an interference signal in the radar device according to the second embodiment of the present invention;

(FMCW radar device)
One type of radar system is an FMCW radar system that transmits a frequency-swept chirp signal as a transmission signal. When this transmitted signal is reflected by the object, a signal delayed by the time corresponding to the distance to the object is received. can measure the distance to The FMCW radar device is promising as one of means for recognizing the surrounding environment in automatic driving of automobiles.

FIG. 1 is a diagram showing the configuration of a typical FMCW radar device. The radar apparatus of FIG. , and a receiving antenna 110 .

Under the control of the DSP 108 , the waveform generator 101 generates a voltage waveform in which the voltage changes continuously at a predetermined cycle, and outputs the voltage waveform to the voltage controlled oscillator 102 . Voltage controlled oscillator 102 generates a transmission signal with an oscillation frequency controlled according to the voltage waveform input from waveform generator 101 and outputs the signal to amplifier 103 and mixer 105 . Amplifier 103 amplifies the transmission signal input from voltage controlled oscillator 102 and outputs it to transmission antenna 109 . A transmission antenna 109 emits a transmission signal input from the amplifier 103 into space. As a result, an FMCW signal obtained by frequency-modulating a continuous wave is transmitted from the radar device.

Receiving antenna 110 receives a received signal, which is a transmitted signal reflected by an object, and outputs the received signal to low-noise amplifier 104 . Low noise amplifier 104 amplifies a received signal input from receiving antenna 110 and outputs the amplified signal to mixer 105 . Mixer 105 is composed of a multiplier, and multiplies the transmission signal input from voltage-controlled oscillator 102 and the reception signal input from low-noise amplifier 104 to generate a beat according to the frequency difference between these signals. A signal is generated and output to low pass filter 106 . Low-pass filter 106 extracts the low-frequency component of the beat signal input from mixer 105 and outputs it to AD converter 107 . The AD converter 107 converts the beat signal input from the low-pass filter 106 into a digital signal every predetermined sampling period, thereby generating a digital value of the beat signal and outputting it to the DSP 108 . The DSP 108 performs a fast Fourier transform (FFT) on the digital value of the beat signal obtained by the AD converter 107 to obtain a signal waveform in which the beat signal is decomposed into frequency components. Then, by detecting a peak exceeding a preset threshold in this signal waveform, the frequency of the beat signal corresponding to the distance to the object is obtained, and the distance to the object is calculated.

The FMCW radar apparatus of FIG. 1 generates, for example, a triangular wave or sawtooth wave voltage waveform by waveform generator 101 and outputs it to voltage controlled oscillator 102 to transmit a transmission signal obtained by frequency-modulating a continuous wave. A reflected wave of the transmitted signal reflected by the object is input as a received signal to the mixer 105 after a delay time proportional to the distance d from the object. Therefore, a beat signal with a frequency proportional to the delay time is obtained.

2. Description of the Related Art In recent years, with the spread of automatic driving and driver assistance systems, the installation of radar devices in vehicles is progressing. Such an on-vehicle radar device is used to detect the distance from a target object, the position of the target object, etc. as the surrounding environment of the vehicle, using objects such as people, obstacles, and other vehicles existing around the vehicle. . As the number of vehicles equipped with radar devices increases, radar signals transmitted from other nearby vehicles may be received as interference signals.

Here, consider a case where two FMCW radar devices using transmission signals of the same frequency band exist within a short distance. In this case, the transmission signal of one FMCW radar device becomes an interference signal to the other FMCW radar device, causing interference. The radar signal that becomes the interference signal is not limited to that of the FMCW radar system. Radar signals of other radar systems, such as the pulse radar system and the CW radar system, can also become interference signals if they are in the same frequency band.

FIG. 2 is a diagram for explaining the operation of a conventional radar device when there is an interference signal. FIG. 2 shows an example of interference operation in broadband interference in one of the two FMCW radar devices when there are two FMCW radar devices within a short distance as described above. The upper part of FIG. 2 shows how the frequencies of the transmission signal and reception signal of one FMCW radar device and the transmission signal of the other FMCW radar device detected as an interference signal by the FMCW radar device change over time. showing. The lower part of FIG. 2 shows how the frequencies of the beat signals obtained from the received signal and the interference signal change over time.

In the upper part of FIG. 2, the transmission signal indicated by a double line is a period ( hereinafter referred to as a "transmission period") and a period in which the frequency continuously changes in the downward direction from the transmission end frequency fe to the transmission start frequency fs (hereinafter referred to as a "return period"). It has a sawtooth shape. Also, the reception signal indicated by the solid line changes in frequency in the same manner as the transmission signal at a timing slightly delayed from that of the transmission signal. On the other hand, the interference signal indicated by the dashed line changes in frequency similarly to the transmission signal and the reception signal at different timings.

When each signal is frequency-modulated at different timings as described above, the beat frequency of the received signal and the beat frequency of the interference signal change as indicated by the solid and broken lines in the lower part of FIG. That is, the beat frequency of the received signal is constant within the passband of the low-pass filter 106 during the period when both the frequencies of the transmitted signal and the received signal change in the upward direction. On the other hand, the beat frequency of the interference signal is outside the passband of the low-pass filter 106 during the period when both the frequencies of the transmission signal and the interference signal are changing in the upward direction, but the beat frequency is outside the passband of the low-pass filter 106. to time t4, and the period from time t1 to time t2, which is the return period of the interference signal, changes in a V shape over a wide band according to the frequency difference between the transmission signal and the interference signal. As a result, the beat frequency of the interference signal may fall within the passband of the low-pass filter 106 during the period from time t1 to time t2, which overlaps with the transmission period of the transmission signal. , the interfering signal is received as an impulse signal that interferes with the received signal. Since the interference signal thus received is an impulse signal, its frequency spectrum is similar to that of white noise. As a result, the noise level in the received signal increases, reducing the signal-to-noise ratio (SNR) and making it difficult to detect distant targets.

An FMCW radar device mounted on a vehicle is required to reduce the interference as described above so as to prevent erroneous detection or non-detection of a target. In particular, in scenes such as automatic driving using a radar device, erroneous detection or non-detection of targets can lead to traffic accidents. In addition, as the spread of autonomous driving progresses and the number of vehicles equipped with radar equipment increases, the possibility of vehicles equipped with radar equipment using the same frequency band transmission signal as the own vehicle existing in the vicinity increases. , the probability of wideband interference occurring increases. Therefore, it is extremely important to avoid and eliminate broadband interference. Embodiments of the present invention for avoiding the occurrence of broadband interference in an FMCW radar system will now be described with reference to the drawings.

(First embodiment)
FIG. 4 is a diagram showing the configuration of the radar device according to the first embodiment of the present invention. The radar device 1 shown in FIG. 4 is an FMCW radar device, and a switch 111 is added to the same hardware configuration as in FIG. That is, the radar apparatus 1 includes the waveform generator 101, the voltage controlled oscillator 102, the amplifier 103, the low noise amplifier 104, the mixer 105, the low-pass filter 106, the AD converter 107, the DSP 108, and the transmission antenna 109, which are explained in FIG. , and a receiving antenna 110 , and a switch 111 between the voltage controlled oscillator 102 and the amplifier 103 .

The DSP 108 performs processing for calculating the distance to the object based on the digital value of the beat signal input from the AD converter 107, as described with reference to FIG. In addition to controlling the waveform generator 101, it also controls the operation timing of the radar device 1 and the like.

The radar device 1 can realize each of the functions described above by software processing executed by the DSP 108 . It should be noted that, instead of the DSP 108, hardware combining logic circuits and the like may be used.

Waveform generator 101 generates a voltage waveform in which the voltage changes continuously at a predetermined cycle, and outputs it to voltage controlled oscillator 102 and switch 111, as described with reference to FIG. Based on the voltage waveform input from the waveform generator 101 , the voltage controlled oscillator 102 alternately repeats the transmission period and the return period to generate a transmission signal, and outputs the transmission signal to the switch 111 and the mixer 105 . .

The switch 111 switches the connection state between the voltage controlled oscillator 102 and the amplifier 103 from on to off or from off to on based on the voltage waveform input from the waveform generator 101 . This permits or prohibits the output of the transmission signal from the voltage controlled oscillator 102 to the amplifier 103 . When the transmission signal output from voltage controlled oscillator 102 is input through switch 111 , amplifier 103 amplifies the input transmission signal and outputs the amplified signal to transmission antenna 109 . A transmission antenna 109 emits a transmission signal input from the amplifier 103 into space. As a result, the FMCW signal obtained by frequency-modulating the continuous wave is transmitted from the radar device 1 only while the switch 111 is on, and the transmission of the FMCW signal is stopped while the switch 111 is off.

In this embodiment, the switching timing of the switch 111 is controlled in accordance with the timing at which the change direction of the frequency of the transmission signal output from the voltage controlled oscillator 102 is switched. Specifically, based on the change in the voltage waveform input from the waveform generator 101, the switch 111 is switched from on to off at the timing when the transmission signal switches from the transmission period described with reference to FIG. 2 to the return period. Also, the switch 111 is switched from off to on at the timing when the transmission signal switches from the return period to the transmission period. As a result, the operation of the switch 111 is controlled such that the output of the transmission signal from the voltage controlled oscillator 102 is permitted during the transmission period and the output of the transmission signal from the voltage controlled oscillator 102 is prohibited during the return period.

FIG. 5 is a diagram for explaining the operation when there is an interference signal in the radar device 1 according to the first embodiment of the present invention. FIG. 5 shows an example of the operation of one radar device 1 when two radar devices 1 of this embodiment are within a short distance, and corresponds to FIG. 2 described above. That is, in the upper part of FIG. 5, the state of temporal changes in the frequency of the transmission signal and the reception signal of one radar device 1 is indicated by a double line and a solid line, respectively. In addition, the dashed line shows how the frequency of the transmission signal of the other radar device 1, which acts as an interference signal to the radar device 1, changes over time. In addition, the lower part of FIG. 5 shows how the frequencies of the beat signals obtained from the received signal and the interference signal change over time.

In the present embodiment, the switching operation of the switch 111 as described above is performed in each of the two radar devices 1, so that neither the transmission signal nor the interference signal is transmitted during the return period. Therefore, when comparing FIG. 5 and FIG. 2, in the upper part of FIG. 5, the part corresponding to the return period that existed in the upper part of FIG. 2 has disappeared for the transmission signal and the interference signal. As a result, as indicated by the dashed lines in the lower part of FIG. 5, the beat frequency of the interference signal has a period from time t3 to time t4, which is the return period of the transmission signal, and a period from time t1 to time t2, which is the return period of the interference signal. The part corresponding to each period has disappeared. Therefore, as described with reference to FIG. 2, the beat frequency of the interference signal does not fall within the passband of the low-pass filter 106, and wideband interference can be avoided.

As for the received signal generated by the reflection of the transmitted signal by the target, the portion corresponding to the return period that existed in the upper part of FIG. 2 disappears in the upper part of FIG. there is As a result, as indicated by the solid line in the lower part of FIG. 5, the beat frequency of the received signal also disappears in portions corresponding to the return period of the transmitted signal and the return period of the received signal.

According to the first embodiment of the present invention described above, the following effects are obtained.

(1) The radar device 1, which is an FMCW radar device, transmits a transmission signal that is frequency-modulated so that the frequency changes continuously over time, and receives a reception signal that is reflected by the target object. Measure the distance to In the radar device 1, the frequency of the transmission signal continuously changes with time in the upward direction from a predetermined transmission start frequency fs to a predetermined transmission end frequency fe. The radar device 1 does not transmit a transmission signal when returning the frequency from the transmission end frequency fe to the transmission start frequency fs. By doing so, the occurrence of broadband interference in the FMCW radar system can be avoided.

(2) The radar device 1 includes a waveform generator 101 that generates a voltage waveform in which the voltage continuously changes over time, a voltage controlled oscillator 102 that generates a transmission signal based on the voltage waveform, and a transmission signal from the voltage controlled oscillator 102. and a switch 111 that permits or prohibits signal output. The voltage controlled oscillator 102 has a transmission period during which the frequency continuously changes over time from the transmission start frequency fs to the transmission end frequency fe, a return period during which the frequency continuously changes over time from the transmission end frequency fe to the transmission start frequency fs, are alternately repeated to generate a transmission signal. The switch 111 permits the output of the transmission signal during the transmission period and prohibits the output of the transmission signal during the return period. Since this is done, when the frequency is returned from the transmission end frequency fe to the transmission start frequency fs, it is possible to reliably prevent the transmission signal from being transmitted with a simple configuration.

(3) As shown in FIGS. 2 and 5, the voltage controlled oscillator 102 generates a sawtooth frequency modulated transmission signal such that the transmission period is longer than the return period. By doing so, it is possible to shorten the period during which the transmission signal cannot be transmitted and the target cannot be detected as much as possible.

(Second embodiment)
FIG. 6 is a diagram showing the configuration of a radar device according to a second embodiment of the present invention. The radar system 1A shown in FIG. 6 is an FMCW radar system in which the voltage controlled oscillator 102 of FIG. 5 is replaced with two voltage controlled oscillators, a first voltage controlled oscillator 102A and a second voltage controlled oscillator 102B. Other points have the same configuration as the radar device 1 described in the first embodiment.

Waveform generator 101 generates a voltage waveform in which the voltage changes continuously at a predetermined cycle, as described with reference to FIG. . At this time, the waveform generator 101 adjusts the timing at which the frequency of the transmission signal generated by the first voltage-controlled oscillator 102A changes and the timing at which the frequency of the transmission signal generated by the second voltage-controlled oscillator 102B changes. , a phase difference is provided between the voltage waveform output to the first voltage controlled oscillator 102A and the voltage waveform output to the second voltage controlled oscillator 102B. Note that the switch 111 may output both of these voltage waveforms, or may output only one of them.

Based on the voltage waveform input from the waveform generator 101, the first voltage controlled oscillator 102A alternately repeats the transmission period and the return period as described with reference to FIG. Output. Similarly, based on the voltage waveform input from the waveform generator 101, the second voltage controlled oscillator 102B alternately repeats a transmission period and a return period at a timing different from that of the transmission signal generated by the first voltage controlled oscillator 102A. generates a transmission signal and outputs it to switch 111 and mixer 105 . However, in FIG. 6, for the convenience of illustration, an arrow indicating the transmission signal output from the second voltage controlled oscillator 102B to the mixer 105 is omitted. In order to distinguish between the transmission signals respectively generated by the first voltage controlled oscillator 102A and the second voltage controlled oscillator 102B, the former is hereinafter referred to as the "first transmission signal" and the latter as the "second transmission signal". .

The switch 111 selects the first transmission signal output from the first voltage controlled oscillator 102A or the second transmission signal output from the second voltage controlled oscillator 102B based on the voltage waveform input from the waveform generator 101. do. Then, one of the selected transmission signals is output to the amplifier 103 . When one transmission signal selected by switch 111 is input, amplifier 103 amplifies the input transmission signal and outputs it to transmission antenna 109 . A transmission antenna 109 emits a transmission signal input from the amplifier 103 into space. As a result, using one of the transmission signals selected by the switch 111, the FMCW signal obtained by frequency-modulating the continuous wave is transmitted from the radar device 1A.

In this embodiment, the transmission period of the first transmission signal output from the first voltage controlled oscillator 102A and the transmission period of the second transmission signal output from the second voltage controlled oscillator 102B are alternately repeated. , the phase difference between the voltage waveforms output from the waveform generator 101 to the first voltage controlled oscillator 102A and the second voltage controlled oscillator 102B is set. Then, the switching timing of the switch 111 is controlled so as to alternately select the first transmission signal and the second transmission signal at timings matching these transmission periods. Specifically, based on the change in the voltage waveform input from the waveform generator 101, the switch 111 is switched so that the first transmission signal is selected during the transmission period of the first transmission signal. Also, during the transmission period of the second transmission signal, the switch 111 is switched so that the second transmission signal is selected. Accordingly, the second transmission signal is transmitted without transmitting the first transmission signal during the return period of the first transmission signal, and the second transmission signal is transmitted during the return period of the second transmission signal. The operation of the switch 111 is controlled so that the first transmission signal is transmitted without delay.

FIG. 7 is a diagram for explaining operations of the first voltage controlled oscillator 102A and the second voltage controlled oscillator 102B in the radar device 1A according to the second embodiment of the present invention. The upper part of FIG. 7 shows how the first transmission signal output from the first voltage controlled oscillator 102A changes, and the middle part of FIG. 7 shows the second transmission signal output from the second voltage controlled oscillator 102B. It shows how the signal changes. The lower part of FIG. 7 shows how the transmission signal output from the switch 111 changes.

In the present embodiment, as described above, the transmission period of the first transmission signal output from the first voltage controlled oscillator 102A and the transmission period of the second transmission signal output from the second voltage controlled oscillator 102B alternate. is repeated to Specifically, as shown in the upper part of FIG. 7, the transmission period of the second transmission signal starts as shown in the middle part of FIG. be done. Similarly, the transmission period of the first transmission signal is started in synchronization with the timing when the second transmission signal switches from the transmission period to the return period. Note that, as shown in the upper and middle parts of FIG. 7, the first voltage controlled oscillator 102A and the second voltage controlled oscillator 102B operate during the period between the end of the return period and the start of the next transmission period. It has a period during which the transmission signal and the second transmission signal are not generated. These periods are hereinafter referred to as "non-generation periods".

In this embodiment, the switching operation of the switch 111 as described above is performed in accordance with the first transmission signal and the second transmission signal whose frequencies change at the above timings. As a result, as shown in the lower part of FIG. 7, the transmission period is repeated without a return period, and the transmission signal is output from the switch 111 and transmitted from the radar device 1A. Therefore, transmission signals can be transmitted without a break.

FIG. 8 is a diagram for explaining the operation when there is an interference signal in the radar device 1A according to the second embodiment of the present invention. Similar to FIG. 5, FIG. 8 shows an example of the operation of one radar device 1A when two radar devices 1A of this embodiment are within a short distance, and corresponds to FIG. 2 described above. . That is, in the upper part of FIG. 8, the state of the time change of the frequency in the transmission signal and the reception signal of one radar device 1A is shown by the double line and the solid line, respectively. Also, the dashed line shows how the frequency of the transmission signal of the other radar device 1A, which acts as an interference signal to the radar device 1A, changes over time. In addition, the lower part of FIG. 8 shows how the frequencies of the beat signals obtained from the received signal and the interference signal change over time.

In the present embodiment, the generation of the first transmission signal and the second transmission signal and the switching operation of the switch 111 as described above are performed by the two radar devices 1A, respectively. , the return period of the interference signal is 0. As a result, the beat frequency of the interference signal does not fall within the passband of the low-pass filter 106, as indicated by the dashed line in the lower part of FIG. Therefore, the occurrence of wideband interference can be avoided.

According to the second embodiment of the present invention described above, the following effects are obtained.

(4) The radar device 1A, which is an FMCW radar device, transmits a transmission signal that is frequency-modulated such that the frequency changes continuously over time, and receives a reception signal that is reflected by the target object. Measure the distance to In this radar apparatus 1A, the frequency of the transmission signal changes continuously with time in the upward direction from a predetermined transmission start frequency fs to a predetermined transmission end frequency fe. The radar device 1A does not transmit a transmission signal when returning the frequency from the transmission end frequency fe to the transmission start frequency fs. By doing so, it is possible to avoid the occurrence of broadband interference in the FMCW radar apparatus, as in the first embodiment.

(5) The radar device 1A includes a waveform generator 101 that generates a voltage waveform in which the voltage continuously changes over time, a first voltage controlled oscillator 102A that generates a first transmission signal based on the voltage waveform, and a voltage waveform and a switch 111 for selecting the first transmission signal or the second transmission signal and outputting it as the transmission signal. The first voltage controlled oscillator 102A has a transmission period during which the frequency continuously changes over time from the transmission start frequency fs to the transmission end frequency fe, and a return period during which the frequency continuously changes over time from the transmission end frequency fe to the transmission start frequency. , and a non-generation period during which no signal is generated are alternately repeated to generate the first transmission signal. The second voltage controlled oscillator 102B alternately repeats a transmission period, a return period, and a non-generation period at a timing different from that of the first transmission signal to generate the second transmission signal. The switch 111 selects the first transmission signal during the transmission period of the first transmission signal, and selects the second transmission signal during the transmission period of the second transmission signal. Thus, when the frequency of one of the first transmission signal and the second transmission signal is returned from the transmission end frequency fe to the transmission start frequency fs, the other transmission signal is reliably transmitted without transmitting it. be able to.

(6) As shown in FIG. 7, the second voltage controlled oscillator 102B starts the transmission period of the second transmission signal in synchronization with the timing when the first transmission signal changes from the transmission period to the return period. . Also, the first voltage controlled oscillator 102A starts the transmission period of the first transmission signal in synchronization with the timing when the second transmission signal changes from the transmission period to the return period. With this configuration, the return period for returning the frequency from the transmission end frequency fe to the transmission start frequency fs can be set to 0 in the transmission signal output from the switch 111 . Therefore, it is possible to shorten the modulation period T of the transmission signal and improve the measurement accuracy.

(7) As shown in FIG. 7, the first voltage-controlled oscillator 102A generates the first transmission signal frequency-modulated in a sawtooth shape so that the transmission period is longer than the return period. Also, the second voltage controlled oscillator 102B generates a second transmission signal frequency-modulated in a sawtooth shape so that the transmission period is longer than the return period. Since this is done, the frequency of the other transmission signal can be reliably returned from the transmission end frequency fe to the transmission start frequency fs during the transmission period of one transmission signal.

In the embodiment described above, an example was explained in which the frequency of the transmission signal continuously changes over time in the upward direction during the transmission period, and the frequency of the transmission signal changes continuously over time in the downward direction during the return period. The present invention can be applied even if the upstream direction and the downstream direction are interchanged. That is, in the transmission period, the frequency of the transmission signal continuously changes in the downward direction from the predetermined transmission start frequency to the predetermined transmission end frequency, and in the return period, the transmission signal frequency changes from the transmission end frequency to the transmission start frequency. The scope of application of the present invention also includes cases in which the frequency is returned by changing the frequency in the upward direction with time.

The embodiments and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Moreover, although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

1, 1A radar device 101 waveform generator 102 voltage controlled oscillator 102A first voltage controlled oscillator 102B second voltage controlled oscillator 103 amplifier 104 low noise amplifier 105 mixer 106 low pass filter 107 AD converter 108 digital signal processor (DSP)
109 transmitting antenna 110 receiving antenna 111 switch

Claims (5)

An FMCW radar apparatus that transmits a transmission signal whose frequency is frequency-modulated such that the frequency changes continuously over time, receives a reception signal in which the transmission signal is reflected by an object, and measures the distance to the object. hand,
a waveform generator that generates a voltage waveform in which the voltage changes continuously over time;
a voltage controlled oscillator for generating the transmission signal in which the frequency continuously changes with time from a predetermined transmission start frequency to a predetermined transmission end frequency in an upward or downward direction based on the voltage waveform;
an amplifier that amplifies the transmission signal;
a switch installed between the voltage controlled oscillator and the amplifier for permitting or inhibiting output of the transmission signal from the voltage controlled oscillator to the amplifier;
The voltage-controlled oscillator has a transmission period during which the frequency continuously changes over time from the transmission start frequency to the transmission end frequency, and a return period during which the frequency changes continuously over time from the transmission end frequency to the transmission start frequency. and alternately repeating to generate the transmission signal,
wherein the switch permits output of the transmission signal from the voltage controlled oscillator to the amplifier during the transmission period and inhibits output of the transmission signal from the voltage controlled oscillator to the amplifier during the return period ; An FMCW radar apparatus that switches a connection state between the voltage controlled oscillator and the amplifier based on the voltage waveform . In the FMCW radar device according to claim 1,
The voltage-controlled oscillator generates the transmission signal frequency-modulated in a sawtooth shape such that the transmission period is longer than the return period. An FMCW radar apparatus that transmits a transmission signal whose frequency is frequency-modulated such that the frequency changes continuously over time, receives a reception signal in which the transmission signal is reflected by an object, and measures the distance to the object. hand,
a waveform generator that generates a voltage waveform in which the voltage changes continuously over time;
a first voltage controlled oscillator that generates a first transmission signal based on the voltage waveform;
a second voltage controlled oscillator that generates a second transmission signal based on the voltage waveform;
A switch for selecting the first transmission signal or the second transmission signal and outputting the transmission signal as the transmission signal in which the frequency continuously changes with time from a predetermined transmission start frequency to a predetermined transmission end frequency in an upward or downward direction. and
The first voltage-controlled oscillator has a transmission period in which the frequency continuously changes with time from the transmission start frequency to the transmission end frequency, and a period in which the frequency continuously changes with time from the transmission end frequency to the transmission start frequency. alternately repeating a return period and a non-generation period in which no signal is generated to generate the first transmission signal;
the second voltage-controlled oscillator alternately repeats the transmission period, the return period, and the non-generation period at a timing different from that of the first transmission signal to generate the second transmission signal;
The switch selects the first transmission signal during the transmission period of the first transmission signal and selects the second transmission signal during the transmission period of the second transmission signal based on changes in the voltage waveform. and select
A predetermined phase difference is provided between the voltage waveform output by the waveform generator to the first voltage controlled oscillator and the voltage waveform output by the waveform generator to the second voltage controlled oscillator. cage,
The second voltage-controlled oscillator starts the transmission period of the second transmission signal in synchronization with the timing at which the first transmission signal changes from the transmission period to the return period, and starting the return period of the second transmission signal in synchronization with the timing at which the transmission signal changes from the return period to the transmission period via the non-generation period;
The first voltage-controlled oscillator starts the transmission period of the first transmission signal in synchronization with the timing at which the second transmission signal changes from the transmission period to the return period, An FMCW radar apparatus for starting the return period of the first transmission signal in synchronization with the timing at which the transmission signal changes from the return period to the transmission period via the non-generation period. In the FMCW radar device according to claim 3 ,
The first voltage-controlled oscillator generates the first transmission signal frequency-modulated in a sawtooth shape such that the transmission period is equal to the sum of the return period and the non-generation period,
The second voltage-controlled oscillator generates the second transmission signal frequency-modulated in a sawtooth shape such that the transmission period is equal to the sum of the return period and the non-generation period. In the FMCW radar device according to claim 3 or 4 ,
In the waveform generator, the transmission period in the first transmission signal overlaps with the return period and the non-generation period in the second transmission signal, and the transmission period in the second transmission signal and the return period and the non-generation period of the first transmission signal overlap each other.

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