JP2006250558A - Signal interference verification method and radar installation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent interference with self signals and other signals without requiring a complicated constitution by combining easily and synchronously capturable signals with signals resistant to interference. <P>SOLUTION: A second signal to which an identification mark is added is transmitted to a space to be measured from a radar installation after a time delay from the transmission of a first signal from the radar installation to the space to be measured. On the basis of the received first signal after reflection at an object to be measured in the space to be measured, synchronous capture is performed. It is detected whether the second signal is received after the elapse of the time delay from the time of the reception of the first signal when synchronization is established by the synchronous capture. By identifying the identification mark added to the second signal when the reception of the second signal is detected, the presence or absence of signal interference is determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a signal confirmation method for confirming whether or not other signals interfere with each other during distance measurement using a radar device, and a radar device for executing the confirmation method. Specifically, the present invention relates to a vehicle periphery monitoring radar device intended for safety confirmation at the time of lane change for the purpose of preventing a vehicle collision, and enables rapid detection with a simple configuration as much as possible, and Signal interference check method for avoiding interference between signals transmitted from radar devices of own vehicle and other vehicles, or detecting interference and eliminating data with low reliability, and radar device About.

  2. Description of the Related Art Conventionally, a vehicle periphery monitoring radar device has been developed for safety confirmation when changing lanes for the purpose of preventing vehicle collision. Patent Documents 1 and 2 disclose this type of periphery monitoring radar device.

  The perimeter monitoring radar device disclosed in Patent Document 1 is obtained by emitting a laser beam corresponding to a PN (Pseudo noise) code, receiving a pulse train of a signal emitted by the laser beam, and the laser beam. In order to obtain a correlation with the pulse train of the signal, the pulse train is synchronously captured using a plurality of clocks whose phases are shifted and a plurality of correlators.

The periphery monitoring radar device disclosed in Patent Document 2 performs measurement using a PN code, and performs complicated processing such as a feedback system using a VCO (Voltage Controlled Oscillator) in synchronization.
JP 2002-267552 JP-A-11-83991

  However, when a PN code is used as a method for preventing mutual interference between signals at the time of distance measurement using a radar device, the following problems may occur.

  (1) It is necessary to capture synchronization between a transmission signal transmitted from the radar apparatus and a reception signal received by the radar apparatus. For the synchronization acquisition, it is necessary to perform correlation processing by changing the delay time for at least one received signal of one PN code sequence to be used. In order to perform the correlation processing, it is necessary to sequentially perform the correlation processing while shifting the phases of the reception signal and the transmission signal, which causes a problem that the processing becomes complicated and the measurement time becomes long.

  (2) It is conceivable to increase the PN code length in order to improve the accuracy for identifying the other signals. However, when the PN code length is increased, the number of necessary clocks (phase shifts) and the number of correlators are increased, which causes a problem that the system is further complicated and a long time is required for the synchronization acquisition process.

  (3) In a pulse radar apparatus using a signal that is not continuous in time, signal transmission time is short, and transmission frequency is low, it is very difficult to perform stable acquisition and tracking stably. Therefore, there is a problem that it is difficult to apply a method of preventing interference (improvement of noise resistance) by adding an ID such as a PN code.

  (4) In a short-range laser radar apparatus that measures distances at short distances, the time from transmission to reception is short, and the timing at which reflected light from an obstacle is received due to the change in distance to the measurement object Changes. Therefore, since it is impossible to distinguish whether the change in the reception timing is interference between the other signal or the distance to the measurement object, the authenticity of the received signal can be confirmed at the time of interference. It becomes difficult.

  An object of the present invention is to combine a synchronization acquisition signal and an interference prevention signal, and to prevent interference of signals from itself and other signals without requiring a complicated configuration, and a signal interference confirmation method and It is to provide a radar apparatus.

In order to achieve the above object, the signal interference confirmation method according to the present invention is a signal interference confirmation method for confirming the presence or absence of interference of other signals transmitted from the radar device when detecting the surrounding situation.
Providing a delay time after transmitting the first signal from the radar device to the measurement space, and transmitting the second signal to which the identification mark is added from the radar device to the measurement space;
Performing synchronous acquisition based on the first signal reflected and received by the measurement object in the measurement space;
Whether the second signal is received or not is detected after the delay time has elapsed from the time when the first signal is received when the synchronization is achieved. And determining the presence or absence of signal interference by discriminating the identification mark added to the second signal when reception is detected. Here, it is desirable to use a signal that can be easily acquired as the first signal and a signal that is resistant to interference as the second signal.

The radar apparatus for implementing the signal interference confirmation method according to the present invention outputs a signal to a measurement space, receives a signal reflected by a measurement object in the measurement space, and detects a surrounding situation. In the device
A signal generation unit that outputs a first signal and a second signal for measurement, a delay circuit that delays the second signal with respect to the first signal, the first signal, and the second signal A signal output unit that emits the signal to the measurement space with a delay time difference, a synchronization acquisition unit that performs synchronization acquisition based on the first signal reflected and received by the measurement object in the measurement space, and A signal discriminating unit that discriminates whether or not the signal received when the delay time elapses from the time when the first signal is received when synchronization is obtained by synchronization acquisition; It is characterized by.

  In the present invention, the signal generation unit outputs a first signal and a second signal for measurement. The delay circuit delays and outputs the second signal with respect to the first signal from the signal generation unit. The signal output unit gives a delay time difference between the first signal and the second signal, and emits these signals to the measurement space. In accordance with these series of operations, a step of providing a delay time after transmitting the first signal from the radar device to the measurement space and transmitting the second signal with an identification mark from the radar device to the measurement space Processing is performed.

  The synchronization acquisition unit acquires the synchronization based on the first signal reflected and received by the measurement object in the measurement space. Based on this operation, a process of performing synchronization acquisition based on the first signal reflected and received by the measurement object in the measurement space is performed.

  The signal discriminating unit discriminates whether or not the signal received when the delay time elapses from the time when the first signal is received when synchronization is obtained by the synchronization acquisition, is the second signal. Based on this operation, after the delay time has elapsed from the time when the first signal was received when synchronization was obtained by the synchronization acquisition, it is detected whether or not the second signal has been received, When the reception of the second signal is detected, the step of determining the presence or absence of signal interference is performed by discriminating the identification mark added to the second signal.

  As described above, according to the present invention, the time required for synchronization acquisition can be shortened by combining the signal for synchronization acquisition and the signal for interference prevention, and interference caused by discrimination of the signal for interference prevention can be reduced. Prevention can be achieved.

  Furthermore, by using a chirp signal obtained by chirp-modulating a reference pulse as the first signal, the signal output period can be extended (increase in radiant energy), and a signal source with a small output can be used.

  Further, by demodulating the chirp signal using a passive element, particularly SAW-DLL, the first signal can be narrowed by pulse compression, and synchronous acquisition can be performed based on the first signal. Complex signal processing such as FFT for synchronization can be eliminated. Furthermore, since synchronization can be reliably obtained with one light emission, there is no need to perform synchronization tracking, and synchronization acquisition can be performed without using a serial search method. There is no need to output signals continuously.

  Furthermore, when a PN code is used as the second signal, the PN code has randomness and is therefore uniformly distributed over a wide frequency spectrum range, and is resistant to interference of signals of a specific frequency. Furthermore, since it is not completely random but can be expressed by a certain function, it is reproducible and correlation can be obtained on the receiving side. By using the first signal received and pulse compressed as a narrow pulse as the synchronization signal when receiving the PN code, synchronization can be achieved before receiving the PN code, so a long PN code can be used and identified. Can be improved. Furthermore, it is possible to change the randomness by software using the same hardware (for example, FPGA (Field Programmable Gate Array), etc.), which is less expensive than manufacturing multiple types of SAW elements, and the PN code is It is easy to change the identification (ID) provided.

  Further, a chirp signal is used for the first signal, a PN code is used for the second signal, and the delay time of the second signal with respect to the first signal is changed in units of chip sections of the transmission code. The ID discrimination signal is correlated once after receiving the compressed pulse, and the code whose interval is changed in units of chips can be treated as a different code, and the number of usable codes (number of multiple connections) Can be increased. In addition, by applying to pulse radar, it is not necessary to continuously transmit signals, so energy saving, and in laser radar, the light emission frequency of the laser diode of the light source is reduced, so that the lifetime can be extended.

  Furthermore, the signal generation unit generates a PN code based on the reference pulse and a function of outputting a chirp signal obtained by chirp-modulating a reference pulse as the first signal, and outputs the PN code as the second signal. By using these signals and combining the signal for capturing synchronization and the signal for preventing interference, it is possible to prevent the interference of other signals without requiring a complicated configuration. However, the distance to the object can be measured stably in a short time.

  Further, the signal generation unit includes a passive element that chirp-modulates a reference pulse, and a SAW-DLL that spreads the reference pulse is used as the passive element. In this way, by using the chirp signal, the output period of the signal can be extended (increase in radiant energy), and the pulse can be narrowed by pulse compression, so that a signal with a small output can be used. By using passive elements, demodulation to a chirp signal is possible without requiring a complicated configuration. The transmission side can generate a signal with a digital (analog) circuit or the like without using a SAW-DLL. By using passive elements on both the transmitting and receiving sides, the chirp signal can be modulated and demodulated with a simpler configuration.

  Further, the signal generation unit has a function of outputting the first signal that is a chirp signal and the second signal that is a PN code, and the delay circuit is configured to output the second signal with respect to the first signal. The delay time is changed for each chip section of the transmission code. Since the PN code has randomness, the PN code is uniformly distributed over a wide range in the frequency spectrum, and is strong against interference of a signal of a specific frequency. Furthermore, since the PN code is not completely random but can be expressed by a certain function, it has reproducibility and can be correlated on the receiving side. Since the ID discriminating signal (interference prevention signal) is correlated only once after receiving the compressed pulse, the code whose interval is changed in units of chip sections can be treated as a different code, and the number of usable codes ( It is possible to increase the number of multiple connections).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The embodiment of the present invention combines a synchronization acquisition signal (a signal that is easy to acquire synchronization) and an interference prevention signal (a signal that is resistant to interference), without requiring a complicated configuration. It is characterized in that it is possible to measure the distance to a stable object in a short time while preventing interference.

  Specifically, in the embodiment of the present invention, after transmitting the synchronization acquisition signal on the transmission side, the synchronization acquisition signal that can distinguish between the own and other signals is delayed and transmitted, and the synchronization is performed on the reception side. After receiving the acquisition signal, it is determined whether or not there is interference by detecting whether or not the synchronization acquisition signal is received after the delay time assumed at the time of transmission, and whether or not the received signal is a signal transmitted by itself. .

A radar apparatus for carrying out a signal interference confirmation method according to an embodiment of the present invention has, as a basic configuration, a synchronization acquisition unit and a signal discrimination unit, and is intended for safety confirmation when changing lanes. The present invention relates to a vehicle periphery monitoring radar effective for use conditions.
(1) A short distance (for example, about 50 m) can be measured.
(2) It is assumed that there are a plurality of transmission sources at the same time, each transmission source is not synchronized, and transmission is performed at an arbitrary timing. This is because when a plurality of vehicles emit measurement signals, such as when the vehicle is congested in a plurality of lanes such as an expressway, the transmission sources of the vehicles are not synchronized with each other.

  In the embodiment of the present invention, the signal for synchronization acquisition, which is a signal that can be easily acquired, is distinguished from the signal received at an unknown timing that the received signal is a synchronization signal at the same time (instant) with reception, This signal can be synchronized with the synchronization signal received at the operation timing of the receiving circuit.

  A chirp signal is used as the specific synchronization acquisition signal. The reason for using the chirp signal is as follows. A pulse radar device requires a pulse with a pulse width as narrow as possible in order to improve measurement accuracy. However, a laser diode has a limit in reducing a light emission pulse width. Also, the narrow pulse width means that the amount of energy radiated to the measurement space is reduced, so that a light source with a high peak power is required. By using a chirp signal, the signal output period can be extended (increase in radiant energy), and the pulse can be narrowed by pulse compression. Therefore, a signal source with a small output may be used.

  As a modulation unit that modulates a short pulse (reference pulse) with a narrow pulse width into a chirp signal, and a chirp demodulation unit that demodulates a chirp signal received by a reception unit, it is desirable to use a passive element. In particular, it is most important to use a passive element on the receiving side. The transmitting side may generate a signal with a passive element or digital (analog) according to the receiving side element. However, when a passive element is used, a chirp is required without requiring a complicated configuration. Signal modulation and demodulation are possible.

  As passive elements for chirp signals, for example, SAW-DLL (Surface Acoustic Wave Dispersive Delay Lines) can be used. Chirp signals using passive elements such as SAW-DLL can be synchronized with a single light emission, so there is no need to perform synchronization tracking, and synchronization is possible regardless of the serial search method. The synchronization acquisition can be performed in a short time. Therefore, there is no need to output signals continuously. The chirp signal may be UP chirp, Down chirp, a composite thereof, or non-linear modulation.

  The anti-interference signal, which is a signal strong against interference, has the highest priority to be provided with a condition that it can quickly and accurately identify its own and other signals, and does not matter about the ease of synchronization acquisition. This is because the signal transmitted first bears the ease of synchronization acquisition.

  As specific interference prevention signals, for example, the values (ON / OFF) of “1” and “0” are taken in a random cycle (1,0 for an optical signal, +1, −1 for a radio signal) ) Is preferred. If '1' and '0' are repeated at a specific period, it becomes weaker to interference waves because it has a specific frequency spectrum, but it is uniform over a wide frequency spectrum due to its randomness. It becomes more resistant to interference of signals of a specific frequency. However, if it is completely random, there is no reproducibility and correlation cannot be obtained on the receiving side, so it must be expressed by a certain function.

  As a signal that satisfies the above conditions, a PN (Pseudo-random Noise) code can be used. The PN code to be used may be a GOLD code sequence, an OOC code sequence, or a Barker code regardless of the M sequence. 7A and 7B show the OOC code sequence of (341, 5, 1). The generation of the PN code may be performed by hardware processing dedicated to each code, or may be switched in software. In addition, although noise resistance is deteriorated, a code unique to each device, such as a simple binary code, may be added if it is assumed that the codes coincide completely.

  Next, an example in which a chirp signal that has been chirp-modulated using a SAW-DLL passive element is used as a synchronization acquisition signal and a PN code is used as an interference prevention signal will be described as an example.

  As shown in FIG. 1, the radar apparatus according to the embodiment of the present invention includes a transmission unit and a reception unit. The transmission unit includes a short pulse generator 1, a SAW-DLL 2 as a passive element, a delay circuit 3, a PN code generator 4, a measurement direction setting device 5, and an LD driver having a function of selecting a measurement direction. 6 and a plurality of laser diodes 7. In this embodiment, six laser diodes 7 are used, but the number of laser diodes 7 is not limited to this number.

  The receiving unit is synchronized with the photodiode 8 that receives the signal reflected from the measurement object, the amplifier (bandpass filter; BPF) 9 that amplifies and outputs the received signal from the photodiode 8, and the signal discriminating unit 10. And a capture unit 11. The signal discriminating unit 10 includes a SAW-DLL 12 as a passive element, a PN code generator 14, and a PN code correlator 15. The synchronization capturing unit 11 includes a SAW-DLL 12, a time measuring unit 16, and an arithmetic processing unit 17.

  When the measurement start trigger is input at the timing shown in FIG. 2A, the short pulse generator 1 shown in FIG. 1 shapes the short pulse, and the short pulse having a narrow pulse width shown in FIG. To the SAW-DLL 2, the delay circuit 3, and the time measuring unit 16 of the receiving unit.

  The SAW-DLL 2 performs chirp modulation by spectrum-spreading the reference pulse shown in FIG. 2B, and outputs a chirp signal having a long output period as the first signal (FIG. 2C). When the delay circuit 3 detects completion of the chirp signal output from the SAW-DLL 2 (FIG. 2D), it starts timing and outputs a PN output trigger to the PN code generator 4 with a delay time (FIG. 2). 2 (e)). When receiving the PN output trigger output from the delay circuit 3, the PN code generator 4 outputs an encoded pulse (PN code) based on the PN code as a second signal (FIG. 2 (f)). When the PN code generator 4 generates an encoded pulse based on the PN code, the encoded pulse as the second signal is given an identification mark for identifying its own signal by the PN code. The self-other signal is discriminated by detecting the identification mark of the encoded pulse. In this embodiment, the PN code generated by the PN code generator 4 is an M-sequence code, and the code length is set to a code length of 7.

  When the LD driver 6 receives the chirp signal (FIG. 2 (c)) output from the SAW-DLL 2 for the first time, the LD driver 6 drives the laser diode 7 in the measurement direction set by the measurement direction setting device 5 so that the SAW-DLL 2 The chirp signal to be output (FIG. 2C) is emitted as a first signal toward the measurement space.

  Next, when the LD driver 6 receives the PN code signal (FIG. 2 (f)) output from the PN code generator 4 after the delay time set by the delay circuit 3, the laser in the measurement direction set by the measurement direction setting unit 5 is received. The diode 7 is driven, and the PN code (FIG. 2 (f)) output from the PN code generator 4 is emitted into the measurement space as the second signal. When the first signal and the second signal emitted by the LD driver 6 are shown in time series, as shown in FIG. 2 (h), the first signal is first emitted and the first signal is emitted. Later, a second signal is fired with a delay time.

  Next, the timing for transmitting the first and second signals on the transmission side will be described. The necessary conditions for the t-sync in FIG. 2 in the embodiment are that a compressed pulse (FIG. 3B) compressed by the SAW-DLL 12 on the receiving side, which will be described later, and the received PN code (FIG. 3A). The delay time by the delay circuit 3 is set so as not to overlap.

  The SAW-DLL 12 to be described later used in the embodiment takes about 500 nsec from the reception of the chirp signal reflected by the measurement object to the output of the compressed pulse shown in FIG. 3B, and the pulse width is 300 nsec. It has a characteristic of generating a compression pulse of a certain level (FIG. 3B). Therefore, the period t-sync shown in FIG. 2 is ideally selected to be equal to or greater than ½ (≈150 nsec) of the pulse width of the compressed pulse shown in FIG. Thus, the delay time of the delay circuit 3 may be selected.

  In the embodiment, looking at the margin, the period t-sync shown in FIG. 2 is set to 500 nsec. That is, 1 μs is set from the completion of transmission of the chirp signal to the start of transmission of the PN code.

  When measuring a moving object that is a measurement object, a change in signal reception time due to the moving speed of the measurement object affects the measurement resolution, so the period t-sync shown in FIG. 2 is set. The upper limit at that time needs to be within an allowable range in the time from the start of transmission of the chirp signal to the completion of transmission of the PN code. As described above, when the upper limit of the period t-sync shown in FIG. 2 is set, since the time until the completion of transmission of the PN code is affected, when changing the code length of the PN code, the code length is set to In consideration, it is necessary to set the upper limit of the period t-sync shown in FIG. Also, by increasing / decreasing the period t-sync shown in FIG. 2 in units of PN code chips, the PN code can be shifted, and the number of usable codes (the number of multiple connections) can be increased.

  When the signal emitted from the laser diode 7 is reflected by the measurement object and changes its direction to the radar device and propagates, the photodiode 8 on the receiving side receives the reflected signal. When the chirp signal as the first signal and the PN code as the second signal subsequent thereto are present, the photodiode 8 first receives the chirp signal as shown in FIG. After receiving the PN code, the PN code is received with a delay time.

  The amplifier 9 amplifies the chirp signal received by the photodiode 7. Here, since the amplifier 9 has a function of a bandpass filter that matches the center frequency of the chirp signal received by the photodiode 7, when transmitting the PN code, the amplifier 9 has a bandpass filter passing frequency. ASK (Amplitude Shift Keying) modulation. Although the case where the PN code is ASK modulated has been described, the PN code may be PSK (Phase Shift Keying) modulated instead of the ASK modulation. When the amplifier 9 does not have the above-described bandpass filter function, the PN code may be simply OOK (On-Off Keying) modulated.

  When the SAW-DLL 12 receives the chirp signal (see FIG. 3A) amplified by the amplifier 9 at the timing shown in FIG. 2K, the SAW-DLL 12 compresses the chirp signal at the timing shown in FIG. 3B, the compressed pulse shown in FIG. 3B is generated, and the SAW-DLL 12 outputs the generated compressed pulse to the time measuring unit 16 and also outputs it to the delay circuit 13 as a synchronization signal. Here, when the distance from the radar device to the measurement object is 0 (zero), the SAW-DLL 2 outputs the short pulse (reference pulse) from the time when the short pulse generator 1 outputs the short pulse (reference pulse). The time until complete chirp modulation is defined as t-0chirp (FIG. 2 (b)). Further, t-range in FIG. 2B corresponds to the time required for a round trip until the chirp signal emitted from the radar apparatus is reflected by the measurement object and returns to the radar apparatus again.

  Since the time measurement unit 16 receives a trigger to start timing from the short pulse generator 1 when a short pulse (reference pulse) is output, the time measurement unit 16 starts timing from the input time of the trigger (FIG. 2 (i)). Timekeeping is continued until the compression pulse shown in FIG. 2 (l) is input from SAW-DLL12. The time measuring unit 16 outputs time data measured until the time when the compression pulse is input from the SAW-DLL 12 to the arithmetic processing unit 17.

  The arithmetic processing unit 17 calculates the distance from the radar device to the measurement object in the measurement space based on the time data input from the time measurement unit 17. More specifically, the transmission timing from when the short pulse generator 1 outputs a short pulse (reference pulse) until the laser diode 7 emits a chirp signal (FIG. 2), and the chirp reflected by the measurement object Based on the reception timing (FIG. 2) from when the signal is received until the compressed pulse is output from the SAW-DLL 12, the arithmetic processing unit 17 determines the radar device and the measurement target based on the time data input from the time measurement unit 17. The time when the chirp signal reciprocates between objects is calculated. Since the chirp signal in the embodiment uses an optical signal emitted from the laser diode 7 and the speed of the optical signal is known, the arithmetic processing unit 17 determines the round trip time of the chirp signal and the speed of the optical signal. To calculate the round trip distance and correct the calculated distance to the actually measured distance from the radar device to the measurement object. Since this distance calculation method is known, its details are omitted.

  On the other hand, when the photodiode 8 receives a signal at the timing of FIG. 2 (h) after the SAW-DLL 12 outputs a synchronization signal, the code acquisition unit {= (number of matches−number of mismatches ÷ code length). )} Or the like, the signal received by the photodiode 8, specifically, the transmission signal (first signal) generated by the compressed pulse shown in FIG. 3B narrowed by the SAW-DLL 12 as shown in FIG. A chirp signal) or an interference signal.

  The signal discrimination will be specifically described. When receiving the synchronization signal output from the SAW-DLL 12, the delay circuit 13 delays the delay time set by the delay circuit 3 on the transmission side, and outputs a PN code generation timing signal to the PN code generator 14. When receiving the PN code generation timing signal output from the delay circuit 13, the PN code generator 14 generates a PN code and outputs the PN code to the PN code correlator 15.

  As described above, the PN code correlator 15 receives the PN code from the PN code generator 14 with a delay of the delay time set by the delay circuit 13. The time until the PN code correlator 15 receives the PN code from the PN code generator 14 is the time from when the synchronization signal is input from the SAW-DLL 12 to the delay circuit 13 until the PN code is output from the delay circuit 13. Yes, this time corresponds to the delay time set by the delay circuit 3 on the transmission side as the time until the PN code is output for the chirp signal on the transmission side.

  When the photodiode 8 receives the PN code reflected by the measurement object subsequent to the chirp signal reflected by the measurement object, the PN code correlator 15 receives the PN code from the amplifier 9 at the time when the PN code is received from the PN code generator 14. The received PN code is received. Therefore, the PN code correlator 15 correlates the PN code output from the PN code generator 14 and the PN code output from the amplifier 9, and the compressed pulse shown in FIG. It is determined whether the signal is transmitted from its own system. By taking the correlation, the reliability of the distance measurement to the measurement object is confirmed.

  Here, when the distance from the radar apparatus to the measurement object is 0 (zero), the time of shaping the short pulse (reference pulse) shown in FIG. The time until the completion of compression of the chirp signal shown in Fig. 2 is t-0chip, and the PN code shown in Fig. 2 (f) from the time of shaping the short pulse (reference pulse) shown in Figs. 2 (b) and 2 (f) on the transmission side. Let t-0pn be the time to start transmission. The time t-sync (FIG. 2 (m)) from when the compressed pulse of FIG. 3B output from the SAW-DLL 12 is detected until the photodiode 8 starts (synchronizes) the reception of the PN code is (t -sync) = (t-0pn)-(t-0chirp), and this time t-sync is unchanged regardless of the distance measurement.

  Basically, the transmission time difference between the chirp signal (first signal) and the PN code (second signal) up to the time of transmission is also maintained in reception, so that the above explanation depends on the distance to the measurement object. First, there is a delay time corresponding to the transmission time difference between the chirp signal received by the receiving unit and the PN code. Therefore, the time difference between the chirp signal and the PN code on the transmission side and the reception side is the same.

  At the above timing, the PN code (second signal) between the transmission and reception is captured and correlated to obtain the correlation, so that the signal received by the photodiode 8 is the first signal transmitted from the transmission side of the own system. It is possible to distinguish between a certain chirp signal and a signal due to interference.

  Next, a case will be described in which a correlation between the PN code transmitted from the transmission side and the PN code received on the reception side is taken. As described above, since the PN code transmitted from the transmission side and the PN code received at the reception side are synchronized, the PN code correlator 15 includes a PN code output from the PN code generator 14 and an amplifier. The PN codes are correlated with each other by discriminating the coincidence or non-coincidence with the PN codes output by the No. 9. As described above, since the amplifier 9 has a function of detection (ASK demodulation), the PN code output from the amplifier 9 is ASK demodulated and shaped into the same signal form as the PN code transmitted from the transmission side. Has been.

  The laser diode 7 is driven based on the timing shown in FIG. 2H, and the chirp signal having the waveform shown in FIG. 4A from the laser diode 7 and a delay time with respect to this chirp signal are shown in FIG. PN code having the waveform shown in FIG. On the other hand, when received by the photodiode 8 and subjected to envelope detection (ASK demodulation) by the amplifier 9, as shown in FIG. 4B, a detection signal obtained by detecting the chirp signal shown in FIG. The received PN code obtained by detecting the PN code shown in 4 (a) is output.

  FIG. 5A shows waveforms of the detection signal and the received PN code after detection by the amplifier 9. The PN code shown in FIG. 5B is a correlation PN code output from the PN code generator 14 in synchronization with the reception timing of the compressed pulse obtained by compressing the received chirp signal with the SAW-DLL 12. The PN code received by the amplifier 9 shown in FIG. 5A and the correlation PN code output from the PN code generator 14 shown in FIG. 5B are accurately synchronized. I understand.

  The PN code correlator 15 shown in FIG. 1 simultaneously outputs the correlation PN code shown in FIG. 5B output from the PN code generator 14 and the received PN code shown in FIG. As an input, as shown in FIG.

  When the received PN code and the correlating PN code can be regarded as the same as shown in FIG. 5, the PN code correlator 15 transmits a chirp signal (first signal) transmitted from the transmitting side of the own system when the signal received by the photodiode 8 is received. 1), signal discrimination is performed (FIG. 2 (p)).

  As shown in FIG. 6, the PN code correlator 15 receives a chirp signal (first signal) transmitted from the transmission side of its own system when the received PN code and the correlation PN code do not match. Signal discrimination is performed when the signal is due to interference.

  As described above, the PN code correlator 15 determines whether or not the received PN code matches the correlation PN code, and confirms whether the signal is due to interference. Therefore, in the chirp modulation pulse radar device using SAW-DLL, when interference of the chirp signal received first in time series occurs, by checking the PN code received subsequently after receiving the chirp signal Therefore, it is possible to determine whether the received signal is a correct received signal or a received signal due to interference, and the reliability of the system is improved.

  In the embodiment of the present invention, when the received PN code and the correlation PN code are correlated, since the two PN codes are synchronized with each other, fast Fourier transform FFT (Fast Fourier Transform), discrete Fourier transform DFT Even without using a process such as (Discrete Fourier Transform), the received PN code and the correlation PN code are confirmed to match, and the correlation can be easily obtained by code correlation {= (number of matches−number of mismatches) ÷ code length}. Can be sought.

  As described above, in the embodiment of the present invention, by transmitting a chirp signal using a passive element such as SAW-DLL from the transmission side and receiving using a passive element such as SAW-DLL on the reception side, The transmission / reception time of the chirp signal is measured to measure the distance from the radar device to the measurement object. This is because the synchronization / correlation of the PN code on the receiving side is performed using a chirp signal emitted from the transmitting side as a reference signal.

  It is also possible to measure the distance between the radar apparatus and the measurement object based on an interference prevention signal such as a PN code instead of the chirp signal emitted from the transmission side. However, even if the chirp signal can be received, a part of the interference prevention signal transmitted with a delay time with respect to the chirp signal may not be received due to the interference. Further, assuming that the chirp signal and the interference prevention signal have been correctly received, the reception timing of the chirp signal needs to be measured with fine resolution by analog signal processing (or high-speed digital processing). The correlation of the interference prevention signal may be processed at a frequency about three times the chirp period of the PN code to be used. However, when the interference prevention signal is used for distance measurement between the radar apparatus and the measurement object, high-speed digital processing is also required for the correlation processing of codes.

  For the above reasons, as described above, it is desirable that the distance measurement between the radar apparatus and the measurement object is performed based on a signal for acquisition of synchronization such as a chirp signal.

  Next, it will be examined whether each of the chirp signal as the first signal and the PN code as the second signal can have both functions of synchronization acquisition and interference prevention.

  In the existing chirp (Chirp: linear FM modulation) radar system using SAW-DLL, in order to give an identification mark (ID) to the signal, multiple types of SAW are used by nonlinear FM modulation etc. Since it is necessary to fabricate the element, it is practical considering the manufacturing constraints, such as how much characterization is possible, and the cost of creating multiple masks even when fabricating with semiconductor manufacturing technology Not.

  When using a SAW element, a Matched Filtering method can be employed. In this Matched Filtering method, the interval between the electrodes formed in the SAW-DLL is modulated with a PN code, and the received PN code is instantaneously captured using the properties of the element. Is output. However, in this method, it is necessary to remake the SAW element itself every time the type of PN code is changed.

  Also from the above situation, it is difficult to obtain the merits of both short-term synchronization acquisition and interference prevention of own and other signals with a simple configuration in the conventional method, and the configuration according to the embodiment of the present invention is configured. Is effective.

  In the embodiment shown in FIG. 1, the six laser diodes 7 are switched and lit to scan the measurement object in the measurement space without using a mechanical mechanism. It is not a thing. As shown in FIG. 8A, the laser beam output from the laser diode 7 may be input to the galvano-scanner mirror 18 to scan the measurement object. Further, as shown in FIG. 8B, a combination of a set of laser diodes 7 and photodiodes (8) having no scanning mechanism may be constructed as a system for measuring in a specific direction. .

  The embodiment shown in FIG. 1 is applied to a laser radar apparatus that emits a laser diode based on the first signal and the second signal, and transmits and receives the first signal and the second signal by laser light. However, it is not limited to this. The present invention can be applied to, for example, a microwave radar apparatus that modulates radio waves based on the first signal and the second signal, and transmits and receives the first signal and the second signal using the radio waves. Furthermore, the radar apparatus according to the embodiment is used for ranging, but is not limited thereto, and may be used for communication or the like. When the present invention is applied to a laser radar apparatus, it is advantageous in terms of cost compared to millimeter waves and microwaves, and has an advantage that the circuit configuration can be simplified.

  In the case of ACC (Adaptive Cruise Control), the first signal and the second signal are output not only in the traveling direction of the vehicle but also in a wide range. Need to reduce.

  In contrast, the present invention uses pulsed radar light that emits light for a short time, so the life of the laser diode can be extended, and not only the point of synchronization acquisition but also the energy saving of the entire radar system. Can be realized.

  As described above, according to the present invention, by using a received signal that can be instantaneously synchronized as a synchronization signal, such as a chirp signal using a passive element such as SAW-DLL, as a synchronization signal, the subsequent acquisition is performed. It is possible to make a system that synchronizes signals (PN codes, etc.) with high identification of self-other signals with another indicator (ID), and the result of distance measurement using a chirp signal is correct by the signal transmitted by the own system Whether it is a result or an incorrect result due to a signal transmitted from a signal source of another system can be confirmed by examining a PN code or the like.

  The interference between the self and other signals will be described in detail. The present invention has an effect of avoiding the interference between the self and other signals by using a characteristic signal such as a chirp signal that is not often used in the laser radar apparatus. Interference between the same systems can be avoided due to differences in codes. Accordingly, it is possible to obtain both synchronization acquisition in a short time and detection of highly reliable interference with a simple configuration.

It is a block diagram which shows the radar apparatus based on the Example of this invention. In the Example of this invention, it is a characteristic view which shows the transmission / reception timing of a 1st signal and a 2nd signal. FIG. 3A is a characteristic diagram showing waveforms of a chirp signal and a PN code transmitted from the transmission side, and FIG. 3B is a characteristic showing a waveform obtained by compressing a chirp signal received on the reception side. FIG. FIG. 4A is a characteristic diagram showing the waveform of the laser beam emitted from the laser diode corresponding to the chirp signal and the PN code, and FIG. 4B is a demodulated signal and received signal that are ASK demodulated on the receiving side. It is a characteristic view which shows the waveform of a PN code. 5A is a characteristic diagram showing a waveform of a received PN code ASK demodulated by an amplifier, and FIG. 5B is a characteristic showing a waveform of a correlation PN code output from a PN code generator on the receiving side. FIG. FIGS. 6A and 6B are characteristic diagrams illustrating a case where the correlation between the received PN code and the correlation PN code does not match. FIGS. 7A and 7B are characteristic diagrams showing examples of PN codes. 8A and 8B are configuration diagrams showing another embodiment of the present invention.

Explanation of symbols

1 Short pulse generator 2 SAW-DLL
3 Delay circuit 4 PN code generator 6 LD driver 7 Laser diode 8 Photo diode 9 Amplifier (BPF)
10 Signal Discrimination Unit 11 Synchronization Acquisition Unit 12 SAW-DLL
13 Delay circuit 14 PN code generator 15 PN code correlator

Claims (15)

In the signal interference confirmation method for confirming the presence or absence of interference of other signals transmitted from the radar device when detecting the surrounding situation,
Providing a delay time after transmitting the first signal from the radar device to the measurement space, and transmitting the second signal to which the identification mark is added from the radar device to the measurement space;
Performing synchronous acquisition based on the first signal reflected and received by the measurement object in the measurement space;
Whether the second signal is received or not is detected after the delay time has elapsed from the time when the first signal is received when the synchronization is achieved. And a step of determining whether or not there is signal interference by discriminating the identification mark added to the second signal when reception is detected. In the signal interference check method according to claim 1,
A signal interference check method, wherein a chirp signal for synchronization acquisition is used as the first signal. In the signal interference confirmation method according to claim 2,
A signal interference check method, wherein the chirp signal is demodulated by a passive element. In the signal interference confirmation method according to claim 3,
A signal crosstalk confirmation method, wherein a SAW-DLL is used as the passive element, and the first signal is demodulated by the SAW-DLL. In the signal interference check method according to claim 1,
A signal interference check method using a PN code for preventing interference as the second signal. In the signal interference check method according to claim 1,
Using a chirp signal for the first signal, using a PN code for the second signal,
A signal interference check method, wherein a delay time of the second signal with respect to the first signal is changed in units of chip sections of a transmission code. In a radar device that outputs a signal to a measurement space, receives a signal reflected by a measurement object in the measurement space, and detects a surrounding situation,
A signal generator for outputting a first signal and a second signal for measurement;
A delay circuit for delaying the second signal with respect to the first signal;
A signal output unit for emitting a delay time difference between the first signal and the second signal and emitting these signals to a measurement space;
A synchronization acquisition unit that performs synchronization acquisition based on the first signal reflected and received by the measurement object in the measurement space;
A signal discriminating unit that discriminates whether or not the signal received when the delay time has elapsed from the time when the first signal is received when the synchronization is achieved by the synchronization acquisition; Radar apparatus characterized by the above. The radar apparatus according to claim 7, wherein
The radar apparatus according to claim 1, wherein the signal generator has a function of outputting a chirp signal for synchronization acquisition as the first signal. The radar apparatus according to claim 7, wherein
The radar apparatus according to claim 1, wherein the signal generation unit has a function of outputting a PN code for preventing interference as the second signal. The radar apparatus according to claim 8, wherein
The radar apparatus according to claim 1, wherein the signal generation unit includes a passive element that chirp-modulates a reference pulse and outputs a chirp signal. The radar apparatus according to claim 10, wherein
2. The radar apparatus according to claim 1, wherein the passive element is a SAW-DLL that spreads a reference pulse. The radar apparatus according to claim 8, wherein
The synchronization acquisition unit has a function of demodulating the received first signal. The radar apparatus according to claim 8, wherein
The radar apparatus according to claim 1, wherein the synchronization acquisition unit includes a passive element that demodulates the received first signal. The radar apparatus according to claim 13, wherein
The radar device, wherein the passive element is a SAW-DLL that compresses a received chirp signal and demodulates the first signal. The radar apparatus according to claim 7, wherein
The signal generation unit has a function of outputting the first signal that is a chirp signal and the second signal that is a PN code,
The radar apparatus according to claim 1, wherein the delay circuit changes a delay time of the second signal with respect to the first signal for each chip section of a transmission code.

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