JP2007240445A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and inexpensive radar system having desired detection precision, without worsening a reception characteristic. <P>SOLUTION: A transmission antenna 1 transmits a transmission signal with a frequency modulated by a chopping wave. Reception antennas 2A-2N are arrayed along a prescribed direction, and receives a reflected wave. The respective reception antennas 2A-2N output respectively the reception signals to respective band-pass filter parts 3A-3N of a multiplexer 30. Frequency bands different each other are set as passing bands to be allocated sequentially by dividing a substantially full frequency band of the frequency-modulated band of the transmission signal with the number of antennas, in the respective band-pass filter parts 3A-3N. A composition output signal output from the multiplexer 30 is brought into a signal arrayed time-serially with the reception signals output sequentially from the band-pass filter parts 3A-3N, by this constitution. This manner brings the same situation as the time-serial selective output of the reception signals of the band-pass filter parts 3A-3N, without using a switching circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an FM-CW radar device used for preventing collision of an automobile, and more particularly to a holographic radar device using an array antenna.

  Conventionally, as an automobile-mounted radar device that detects the orientation of an object using millimeter-wave band high-frequency signals, continuous waves that are frequency-modulated are used, and continuous reflected waves are received by a plurality of arranged receiving antennas. Various FM-CW radar devices for detecting the azimuth have been devised. For example, the radar apparatus of Patent Document 1 includes one transmitter having one transmission antenna and a plurality of receivers each having one reception antenna. And the radar apparatus of patent document 1 has detected the azimuth | direction of the detection object from the phase difference of the received signal by each receiver.

The radar device disclosed in Patent Document 2 includes one transmitter having one transmission antenna and one receiver having a plurality of reception antennas. And the radar apparatus of patent document 2 switches several receiving antennas at high speed with a switch, and detects the azimuth | direction of a detection object from the phase difference of the received signal obtained from each receiving antenna.
Japanese Patent No. 3498624 Japanese Patent No. 3622565

  The radar apparatus of Patent Document 1 requires the number of receivers corresponding to the number of reception antennas. However, a millimeter-wave band high-frequency signal receiver such as the FM-CW system is very expensive. For this reason, if the number of receiving antennas is increased in order to improve the detection accuracy, the number of receivers also increases in proportion, so that the radar apparatus becomes very expensive. In addition, the increase in the number of receivers makes it difficult to reduce the size by increasing the number of components of the radar apparatus more than simply increasing the number of antennas.

  In addition, the radar apparatus of Patent Document 2 can use one switch to reduce the number of receivers. However, a millimeter-wave high-frequency switch is also expensive, and the cost is low as in Patent Document 1. It is difficult to make. In particular, a switch having a large number of branches (couplings) such as 1 input 8 outputs (8 inputs 1 output) is particularly expensive and cannot be easily obtained. For this reason, switches with one input and two outputs (two inputs and one output) such as SPDT are used in multiple stages. However, since the loss in each switch is large, the reception loss increases as the detection accuracy is increased and the number of stages is increased. Will increase.

  Therefore, an object of the present invention is to realize a radar apparatus having a desired detection accuracy in a small size and at a low cost without deteriorating reception characteristics.

  According to the present invention, a transmitting means for transmitting a continuous wave frequency-modulated by a transmitting antenna from the transmitting antenna and a reflected wave of a continuous wave transmitted by a plurality of arranged receiving antennas are received and received signals The present invention relates to a radar apparatus comprising: a receiving unit that outputs a signal; and a detecting unit that detects the orientation of a detected object based on a received signal. The receiving means sets a plurality of divided frequency bands obtained by dividing the reception frequency band corresponding to the modulation frequency band to a plurality of receiving antennas, respectively, and continuously receives the reception signals of the plurality of divided frequency band components. It is characterized by outputting every period.

  In this configuration, the transmission means transmits a continuous wave whose frequency changes with time. Each receiving antenna of the receiving means receives the reflected wave of the transmitted continuous wave. And a receiving means passes a different frequency band, respectively with respect to the reflected wave which each receiving antenna receives. The received signals corresponding to the respective receiving antennas are formed with only frequency band components different from each other and are arranged with time. This is equivalent to the process of outputting the received signal.

  Further, the receiving means of the radar apparatus of the present invention is a multiplexer having a plurality of filters each connected to a plurality of receiving antennas, each having a different pass band for each receiving antenna, and a combining unit for combining the output signals of the plurality of filters. It is characterized by having.

  In this configuration, by changing the pass band of each filter of the multiplexer, even if the reflected wave is continuously received by all the receiving antennas, only the received signal in the corresponding frequency band is output. That is, only the reception signal from the reception antenna connected to the filter corresponding to the frequency at that time is output according to the frequency change of the transmitted continuous wave. This is equivalent to outputting a reception signal while switching a plurality of reception antennas with a switch or the like.

  Further, the plurality of receiving antennas of the radar apparatus according to the present invention are characterized by having different receiving frequency bands.

  In this configuration, each receiving antenna receives only the reflected wave in the corresponding frequency band. That is, according to the frequency change of the transmitted continuous wave, only the received signal from the receiving antenna corresponding to the current frequency is output. This is equivalent to switching a plurality of receiving antennas with a switch or the like or outputting a received signal while separating them with a plurality of filters.

  Further, the detection means of the radar apparatus according to the present invention adjusts the phase based on the azimuth detected by each time-divided reception signal and the interval between the plurality of reception antennas, and at least for one period of the modulation period. The phase is matched, and the distance of the sensing object is detected from the received signal for at least one modulation period in which the phases are matched.

  In this configuration, the reception signal corresponding to each reception antenna corresponds only to the division period obtained by dividing the modulation period, but if the reception signal for each division period is continuously output for one period, the modulation period A reception signal for one period is obtained. At this time, the received signal of each receiving antenna has a phase difference according to the detected azimuth and the interval between the receiving antennas. A continuous received signal is obtained. By using such a continuous reception signal for one period, the observation period of the beat signal frequency is lengthened, and the distance and speed detection accuracy is improved.

  In addition, the detection means of the radar apparatus according to the present invention detects the received signal strength of each time-divided period, and the received signal strength corresponding to the receiving antenna whose pass frequency is set at the end of the received frequency band is different. When it is detected that the received signal strength is lower than that of the receiving antenna, the transmitting unit is instructed to change the center frequency of the frequency modulation band.

  In this configuration, when the frequency band of the transmitted continuous wave is shifted, the frequency band of the reflected wave is shifted correspondingly. As a result, the frequency modulation band has changed by detecting that the received signal strength of the receiving antenna whose end of the receiving frequency band is set to the passband is lower than the received signal strength of other receiving antennas. Is detected. Then, the detection means outputs the amount of frequency deviation to the transmission means, and the transmission means corrects the center frequency of the modulation frequency according to the amount of deviation.

  According to the present invention, by setting a frequency band for each reception signal of each reception antenna, it is obtained by switching received signals in different frequency bands for each division period shorter than the modulation period without using a switch. be able to. As a result, it is possible to detect the azimuth by the phase difference between the received signals corresponding to each division period. As a result, a radar apparatus having a small reception loss and a desired azimuth detection accuracy can be made small and inexpensive without using a switch circuit that is an expensive circuit element.

  Further, according to the present invention, by using a multiplexer for switching the receiving antenna, it is easy to obtain, and a small size having a desired azimuth detection accuracy with a low receiving loss, only by adding a relatively inexpensive and low-loss circuit element. Can be realized at low cost.

  In addition, according to the present invention, each receiving antenna is provided with a band-pass filter function, so that a multiplexer is not required, and a small radar device having a low reception loss and a desired direction detection accuracy is further simplified. Can be realized.

  Further, according to the present invention, since the reception signal for one modulation period is obtained, the observation period of the beat signal frequency is extended, and the distance and speed of the detected object can be detected with higher accuracy.

  Also, according to the present invention, it is possible to always detect a shift of the frequency modulation band from the received signal intensity corresponding to the end of the reception frequency band and correct the frequency modulation band of the transmission signal.

A radar apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1A is a block diagram showing a main part of the radar apparatus of the present embodiment, and FIG. 1B is a passband and frequency modulation band of each filter unit 3A-3N of the multiplexer 30 shown in FIG. It is a figure which shows the relationship.

  The radar apparatus according to the present embodiment includes a transmission antenna 1, reception antennas 2A to 2N, a multiplexer 30, a signal processing circuit 4, a VCO 5, a branch circuit 6, an LNA 7, a mixer 8, and an IF amplifier 9.

  The transmission antenna 1 is a flat antenna such as a microstrip antenna or a waveguide antenna, and radiates an electromagnetic wave as a transmission signal toward a predetermined detection region including the front direction of the antenna. For example, if this radar apparatus is mounted on an automobile and forward detection is performed, a transmission signal is radiated to a detection area having a predetermined width in front of the automobile. Here, as the transmission signal, for example, as shown in FIG. 1B, a continuous wave whose frequency changes in a triangular shape with time is used.

  The reception antennas 2A to 2N are each formed of a flat antenna, a waveguide antenna, or the like, similar to the transmission antenna 1, and receives a reflected wave from the detection region. These receiving antennas 2A to 2N are composed of a receiving antenna array arranged in a straight line and the receiving antennas 2A to 2N are arranged at equal intervals d.

  The multiplexer 30 includes band-pass filter units 3A to 3N whose one ends are connected to the receiving antennas 2A to 2N, respectively, and the other ends of these band-pass filter units 3A to 3N are connected to a synthesis circuit. As shown in FIG. 1, the bandpass filters 3 </ b> A to 3 </ b> N are formed so that different frequency bands are used as passbands. Specifically, the entire frequency modulation band is divided into N, each having the same frequency width, and the respective center frequencies are f1, f2, f3,..., FN (f1 <f2 <f3 <... < fN) is set. Then, band pass filter units 3A to 3N are formed such that the divided frequency bands of these center frequencies f1, f2, f3,..., FN become the respective pass bands. Here, the frequency modulation band indicates the frequency modulation band of the transmission signal as described above, but the frequency band that can be taken by the reception signal is about the relative speed between vehicles that run with the relative speed of the sensing object facing each other. If there is, the frequency modulation band hardly changes with the frequency modulation band of the transmission signal, so that the frequency modulation band can be treated as equivalent to the frequency band that the reception frequency can take.

  Here, as a specific example of the frequency modulation band and the divided frequency band (divided frequency band), an example of the in-vehicle millimeter wave radar for FM-CW forward monitoring that operates in the 76 GHz-77 GHz band will be described. Assuming that the entire band is 300 MHz and the number of receiving antennas is N = 10, a divided frequency band of 30 MHz is set for each of the bandpass filter units 3A to 3N. Then, by setting the shift amount of the center frequency of each of the band pass filter units 3A to 3N to 30 MHz, band pass filter units 3A to 3N having pass frequency bands of different divided frequency bands are formed. Note that the pass characteristics of the bandpass filter units 3A to 3N may be set so that the ends of the passbands overlap each other, or may not be overlapped at all, and these settings depend on the specifications of the apparatus. What is necessary is just to set suitably.

The synthesis circuit is connected to the LNA 7 and synthesizes the output signals of the band pass filter units 3A to 3N and outputs the synthesized signals to the LNA 7.
Note that the multiplexer 30 may be formed of 10 bandpass filters and one synthesis circuit as described above, or a 3-1 multiplexer comprising three bandpass filters and one synthesis circuit, You may form combining suitably the 2-1 multiplexer which consists of two band pass filters and one synthetic | combination circuit.

  The LNA 7 amplifies the received combined received signal and outputs it to the mixer 8. The mixer 8 mixes the received signal from the LNA 7 and the local signal from the branch circuit 6 to generate an IF beat signal. . The IF amplifier 9 amplifies the IF beat signal and outputs it to the signal processing circuit 4. The signal processing circuit 4 detects the azimuth of the detected object using the known holographic radar principle based on the input IF beat signal and the phase difference obtained from the interval d between the receiving antennas 2A to 2N. Further, the signal processing circuit 4 calculates the distance, speed, and the like of the detected object using a known FM-CW method calculation.

  The VCO 5 generates a transmission signal in the 76 GHz band, for example, according to the modulation voltage given from the signal processing circuit 4. At this time, the VCO 5 is supplied with a modulation voltage whose voltage value fluctuates in a predetermined cycle, for example, a modulation voltage that fluctuates in a triangular wave shape in a predetermined cycle. The VCO 5 generates a transmission signal that is frequency-modulated within a predetermined frequency range, for example, a transmission signal that is frequency-modulated in a triangular wave shape as shown in FIG. To do.

  The branch circuit 6 supplies the transmission signal output from the VCO 5 to the transmission antenna 1 and a part of the transmission signal to the mixer 8 as a local signal.

  Next, the detection operation by the radar apparatus of this embodiment will be specifically described. In the following description, a radar apparatus that transmits a triangular wave transmission signal as shown in FIG. 1B will be described.

  2A shows a transmission signal transmitted from the transmission antenna 1 and an antenna reception signal Sa received by the reception antennas 2A, 2B, 2C,..., 2N with respect to an object having a relative speed of “0”. , Sb, Sc, and Sn, (B), (C), (D), and (E) are band division receptions output from the bandpass filters 3A, 3B, 3C, and 3N, respectively. It is a figure which shows signal Saf, Sbf, Scf, ..., Snf. FIG. 3 is a diagram showing the transmission signal and the combined output signal Sr of the multiplexer 30. 2 and 3, a thick broken line indicates a transmission signal waveform, and a thick solid line indicates various received signals.

  When the detection operation is started, the signal processing circuit 4 gives a modulation voltage whose voltage changes in a triangular wave shape with time to the VCO 5. During the subsequent detection operation, the signal processing circuit 4 continuously applies the same modulation voltage to the VCO 5. The VCO 5 generates a transmission signal (frequency modulation transmission signal) whose frequency continuously changes in a triangular wave shape on the time axis. The frequency-modulated transmission signal is transmitted to the transmission antenna 1 via the branch circuit 6 and radiated from the transmission antenna 1 to the detection area.

  The receiving antennas 2A to 2N constituting the receiving antenna array receive the reflected wave reflected by the object (target) in which the frequency modulation transmission signal (continuous transmission wave) exists in the detection region, and receive the antenna reception signals Sa to Sn. Each is output to each of the bandpass filter units 3A to 3N of the multiplexer 30. Here, the antenna reception signals Sa to Sn have a predetermined phase relationship according to the orientation of the sensing object and the reception antenna interval d. Specifically, the azimuth angle θ is set with reference to the antenna front direction (perpendicular to the arrangement direction of the receiving antenna array and the radiation direction). For example, the front left-hand direction is the positive direction of θ, and the front right-hand direction is the θ direction. Assuming a negative direction, the reflected wave from the object existing in the azimuth angle θ direction is sequentially received with a phase difference of exp ((j2π · d · sin θ) / λ) at each receiving antenna arranged at the interval d. The

  Each of the band-pass filter units 3A to 3N of the multiplexer 30 performs band-pass filtering processing having different pass bands on the input antenna reception signals Sa to Sn, as shown in FIGS. Such band division reception signals Saf to Snf are output.

  Specifically, the band-pass filter unit 3A performs a filter process for allowing only the frequency band of a predetermined width having the center frequency f1 to pass through the antenna reception signal Sa, and performs the band division reception signal Saf shown in FIG. Is output. Similarly, the band pass filter unit 3B outputs the band division reception signal Sbf shown in FIG. 2 (C) that includes only a frequency band having a predetermined width with the center frequency f2 as to the antenna reception signal Sb. The band pass filter unit 3C outputs the band division reception signal Sbc shown in FIG. 2 (D), which includes only a frequency band having a predetermined width with the center frequency f3 as to the antenna reception signal Sc. The band pass filter unit 3N outputs the band division reception signal Snf shown in FIG. 2 (E), which consists only of a frequency band of a predetermined width having a center frequency fN with respect to the antenna reception signal Sn.

  The multiplexer 30 combines these band division reception signals Saf to Snf by a combining circuit and outputs a combined output signal as shown in FIG. At this time, since each of the band-pass filter units 3A to 3N has a different pass band, the band-divided received signals Sbf to Snf become substantially 0 at the timing when the band-divided received signal Saf is output. Similarly, at the timing when the band division reception signal Sbf is output, the band division reception signals Saf and Scf to Snf become substantially zero, and at the timing when the band division reception signal Scf is output, the band division reception signal Saf, Sbf, Sdf to Snf are substantially zero, and the band division reception signals Saf to S (n−1) f are substantially zero at the timing when the band division reception signal Snf is output. Therefore, the combined output signal is substantially composed of the band division reception signal Saf in the frequency band of the center frequency f1 corresponding to the reception antenna 2A, and the band division reception in the frequency band of the center frequency f2 corresponding to the reception antenna 2B. It is constituted by a signal Sbf. Similarly, the frequency band of the center frequency f3 corresponding to the reception antenna 2C is configured by the band division reception signal Scf, and the frequency band of the center frequency fN corresponding to the reception antenna 2N is configured by the band division reception signal Snf. As a result, the combined output signal Sr from the multiplexer 30 is equivalent to a signal obtained by sequentially outputting the band-divided reception signals Saf to Snf for each predetermined sampling time length obtained by time division.

  The signal processing circuit 4 calculates a distance by a known FM-CW distance calculation method using the combined output signal Sr, that is, the band division reception signals Saf to Snf group obtained for each predetermined sampling time length, The phase difference between the band division received signals Saf to Snf is calculated. Then, the signal processing circuit 4 calculates the azimuth θ from the calculated phase difference and the aforementioned exp ((j · 2π · d · sin θ) / λ).

  Further, the signal processing circuit 4 performs a process of matching the phases of all the band division reception signals Saf to Snf for at least one modulation period based on the calculated phase difference. As a result, a group of reception signals having a time length shorter than one modulation period actually received by different reception antennas 2A to 2N is equivalent to reception signals continuously received by one reception antenna for one modulation period. become. The signal processing circuit 4 calculates the distance and speed of the detected object by the known FM-CW distance / speed calculation method using the reception signal having a time length corresponding to one modulation period. Thus, by calculating the distance using the reception signal for one modulation period, it is possible to obtain a result with higher accuracy than the distance calculated by each band division reception signal.

  For example, when the total width of the frequency modulation band is specifically 300 MHz and the number N of antennas is 10, 30 MHz is assigned to each antenna. That is, the frequency band of the transmission signal for each band division reception signal is given 30 MHz. Thus, if there is a frequency band of 30 MHz, a certain amount of distance measurement is possible. However, by using a 300 MHz frequency band corresponding to all band division received signals, observation can be performed with a frequency band 10 times as long as the observation time, and the distance can be calculated with higher accuracy.

  By using the configuration as described above, it is possible to detect the azimuth and distance / speed of an object without installing a switch circuit. Furthermore, by not providing a switch circuit, no switch loss occurs and reception loss can be greatly suppressed. Further, since it is not necessary to use a switch circuit having a complicated configuration as described in the prior art, a radar device can be configured with a simpler structure and a smaller size.

  In the present embodiment, an example is shown in which divided frequency bands of lower frequencies are set in order from the receiving antennas at one end of the array for the receiving antennas 2A to 2N arranged in an array, but as shown in FIG. The arrangement order of the receiving antennas and the direction of transition of the center frequency of the divided frequency band can be set without matching.

  FIG. 4 is a diagram showing a distribution of passbands (center frequencies) when the passbands (center frequencies) of the receiving antennas 2A to 2N are randomly set. In addition, f1-fN in a figure has shown the center frequency of bandpass filter part 3A-3N, respectively.

  In FIG. 4, the pass band (center frequency f3) of the band pass filter unit 3C is set to the lowest frequency band in the entire frequency modulation band, and then the pass band (center frequency fN) of the band pass filter unit 3N is set. In addition, the pass band (center frequency f1) of the band pass filter 3A is set, and the pass band (center frequency f2) of the band pass filter unit 3B is set to the highest frequency band. Even with such settings, the operations and processes described above can be executed. By randomly dividing the frequency band as described above, it is possible to detect an object that moves at a higher accuracy than when sequentially setting the divided frequency bands as described above. This is because the object position at the time of the lower frequency band and the time of the higher frequency band due to the movement of the object when the divided frequency band is shifted from the receiving antenna at one end to the receiving antenna at the other end of the object moving at high speed. This is because a deviation from the object position occurs. On the other hand, when the divided frequency band is set at random, the low frequency band and the high frequency band appear randomly in time series, and thus are not easily affected by this shift.

Next, a radar apparatus according to the second embodiment will be described with reference to FIG.
FIG. 5 is a diagram illustrating the frequency modulation of the transmission signal and the distribution of the passbands (center frequencies) of the reception antennas 2A to 2N according to the present embodiment.
The configuration of the radar apparatus of the present embodiment is the same as that of the radar apparatus of the first embodiment shown in FIG. 1A, and the frequency modulation method of the transmission signal is different from the radar apparatus of the first embodiment. Only.
The radar apparatus according to the present embodiment sets the divided frequency band by dividing the frequency modulation band into N as in the first embodiment. Then, these divided frequency bands are set to pass bands of the band pass filter units 3A to 3N connected to the receiving antennas 2A to 2N, respectively. At this time, in the present embodiment, as shown in FIG. 5, the transmission signal is output by changing the frequency into a triangular wave shape with time in each divided frequency band.

  With such a configuration, the distance and speed of the object can be detected in each divided frequency band. In addition, since the modulation period is shorter than in the case of using a triangular wave-like transmission signal as shown in the first embodiment in which the entire frequency modulation band is gradually up-modulated and down-modulated, the object distance and speed are reduced. It is possible to calculate at higher speed. Furthermore, since the distance can be calculated using only the uplink modulation of each divided frequency band, the distance of the object can be calculated at a higher speed.

Next, a radar apparatus according to a third embodiment will be described with reference to FIG.
FIG. 6A is a block diagram showing the main part of the radar apparatus of this embodiment, and FIG. 6B is a diagram showing the band pass characteristics of the receiving antennas 2A to 2N.
As shown in FIG. 6A, the radar apparatus according to the present embodiment uses only the synthesis circuit 31 without using the multiplexer 30, and each of the reception antennas 2A to 2N has a predetermined reception bandwidth. It also has a function of a band pass filter. The reception bands (pass bands) of the reception antennas 2A to 2N are set so as to substantially match the divided frequency bands assigned to the reception antennas 2A to 2N. As such receiving antennas 2A to 2N, a microstrip antenna or a waveguide slot antenna is originally used in a narrow band. For example, the antenna antenna has a pass band as shown in FIG. It can be easily realized by designing the shape.

  By adopting such a configuration, it is not necessary to use the multiplexer as shown in the first and second embodiments, and it is possible to realize a more compact and small radar device.

Next, a radar apparatus according to a fourth embodiment will be described with reference to FIG.
FIG. 7 shows the time characteristics of the signal strength of the combined output signal output to the signal processing circuit 4, where (A) is a steady state and (B) is the center frequency of the transmission signal shifted to the lower frequency side. State (C) shows a state in which the center frequency of the transmission signal is shifted to the high frequency side.

  In an initial state where the center frequency of the transmission signal does not change from the preset center frequency, the signal strength hardly changes at any time in the frequency modulation band. Therefore, as shown in FIG. 7A, the signal intensity of the combined output signal is constant.

  However, if the center frequency of the transmission signal shifts to the low frequency side due to deterioration over time or the like, a transmission signal is formed with a frequency modulation width corresponding to this center frequency, so a high frequency band of a preset transmission signal is generated. No longer. For example, in the example of FIG. 7, the transmission signal of the division frequency band of the center frequency fN becomes low, and the signal strength of the reception signal received by the reception antenna 2N is lowered as shown in FIG. 7B. On the other hand, when the center frequency of the transmission signal is shifted to the high frequency side, a low frequency band corresponding to the center frequency is not generated. For example, as shown in FIG. 7C, the signal strength of the received signal received by the receiving antenna 2A decreases.

  The signal processing circuit 4 detects such a change in signal strength of the combined output signal. Then, one of the signal strengths at both ends of the frequency band, that is, the signal strength in the frequency band corresponding to the receiving antenna 2A or the receiving antenna 2N is higher than the signal strength of the other receiving antennas 2B to 2 (N-1). When it is detected that the frequency is lower than about 3 dB, the center frequency is shifted so that the signal intensity in all frequency bands is constant. For example, if the signal intensity in the high frequency band corresponding to the receiving antenna 2N is low, the correction modulation voltage is applied to the VCO 5 by setting the center frequency of the transmission signal to be high. On the other hand, if the signal strength in the low frequency band corresponding to the reception antenna 2A is low, the correction modulation voltage is applied to the VCO 5 by setting the center frequency of the transmission signal to be low.

  By adopting such a configuration, it is possible to detect a shift in the center frequency of the transmission signal that occurs due to deterioration over time, etc., and to always correct and maintain the center frequency constant.

It is a block diagram which shows the principal part of the radar apparatus of 1st Embodiment, and the figure which shows the relationship between the pass band of each filter part of a multiplexer, and a frequency modulation band. A diagram of an example showing a transmission signal transmitted from the transmission antenna 1 and antenna reception signals received by the reception antennas 2A to 2N with respect to an object having a relative velocity of “0”, and a band-pass filter 3A, respectively. , 3B, 3C, 3N are diagrams showing band-division received signals output from. It is a figure which shows a transmission signal and the output signal of the multiplexer. It is the figure which showed distribution of the pass band (center frequency) at the time of setting the pass band (center frequency) of each receiving antenna 2A-2N at random. It is the figure which showed frequency distribution of the transmission signal of 2nd Embodiment, and distribution of the pass band (center frequency) of each receiving antenna 2A-2N. It is the block diagram which shows the principal part of the radar apparatus of 3rd Embodiment, and the figure which shows the band pass characteristic of each receiving antenna 2A-2N. FIG. 6 is a diagram illustrating time characteristics of signal strength of a combined output signal output to the signal processing circuit 4;

Explanation of symbols

  1-transmission antenna, 2A-2N-reception antenna, 30-multiplexer, 3A-3N-bandpass filter unit, 31-synthesis circuit, 4-signal processing circuit, 5-VCO, 6-branch circuit, 7-LNA, 8 -Mixer, 9-IF amplifier

Claims (5)

A transmission means comprising a transmission antenna, and transmitting a frequency-modulated continuous wave from the transmission antenna;
Receiving means comprising a plurality of receiving antennas arranged, receiving a reflected wave of a transmitted continuous wave at each receiving antenna and outputting a received signal;
Detecting means for detecting the orientation of the sensing object based on each received signal;
In a radar apparatus equipped with
The reception means sets a plurality of divided frequency bands obtained by dividing a reception frequency band corresponding to a modulation frequency band to each of the plurality of reception antennas, and continuously receives a plurality of divided frequency band component received signals in a time-division manner. A radar apparatus that outputs the signal every period.   2. The multiplexer according to claim 1, wherein the receiving means includes a multiplexer that is connected to each of the plurality of receiving antennas and includes a plurality of filters having different passbands for each of the receiving antennas and a combining unit that combines output signals of the plurality of filters. The radar device described in 1.   The radar apparatus according to claim 1, wherein the plurality of reception antennas have different reception frequency bands.   The detection means adjusts the phase based on the azimuth detected in each time-divided reception signal and the interval between the plurality of reception antennas, and matches the phase of the reception signal over at least one modulation period, The radar apparatus according to any one of claims 1 to 3, wherein a distance of a sensing object is detected from a reception signal corresponding to at least one modulation period in which the phases are matched.   The detection means detects the received signal strength of each time-divided period, and the received signal strength corresponding to the receiving antenna whose pass frequency is set at the end of the receiving frequency band corresponds to the other receiving antenna. The radar apparatus according to any one of claims 1 to 4, wherein when detecting that the received signal strength is lower than the received signal strength, the transmitting unit is instructed to change a center frequency of a frequency modulation band.

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