JP2001074830A - System for measurement of distance between two cars by spread spectrum radar using interference removal processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a distance detection error rate from being increased by a method wherein an inherent PN code which is allocated to another vehicle which transmits interference waves is acquired from received waves, the replica signal of interference waves which are created by using the PN code is removed and the distance between two cars is measured. SOLUTION: A signal spread by a PN code from a first PN-code generator 2 is changed over by a switch 7 in such a way that the signal is transmitted to a known data section. In addition, a signal spread by a common PN code is changed over by the switch 7 in such a way that the signal is transmitted to a data section which is used to transmit vehicle information. After that, the signals are processed by a D/A converter 8 and a low-pass filter(LPF) 9, and they are modulated to a PF signal so as to be transmitted from a transmitting antenna 3. A signal which is received by a receiving antenna 3 is demodulated to a BB signal from an RF signal by a radio (RF) part 14, it is passed through an LPF 15 and an LPF 16, and it is converted by an A/D converter 17 and an A/D converter 18 so as to be sent to a baseband part. An interference-wave removal processing circuit 40 removes interference waves from an oncoming vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum using an interference canceling processing apparatus.
um) A radar inter-vehicle distance measuring system.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
There were the following.

(1) Supervision of Takashi Yoshida, "Radar Technology", IEICE, P117. (2) Masahiro Takeda, Yukiko Hanada, Ryuji Kono, "Spread Spectrum Road-to-Vehicle Communication and Ranging System Using Interference Cancellation Circuit,"
IEICE, Vol. J81-A, no. 4, p
p. 483-489 (1998). Conventional interference wave suppression techniques include an interference wave suppression technique using polarization plane control and an interference wave control technique using antenna directivity.

(1) Suppression of interference wave by polarization plane control It is assumed that all the vehicles equipped with radar devices transmit on the same polarization plane, and the transmission antenna and the reception antenna have the same angle of polarization plane to suppress the interference wave. Is the way. 4 polarization planes
By inclining by 5 °, an angle difference of 90 ° occurs between the desired wave transmitted from the own vehicle equipped with the radar device and the interference wave transmitted from the oncoming vehicle, and the interference wave can be suppressed. .

(2) Suppression of Interference by Antenna Directivity This is a method of suppressing an interference wave incident from an angle deviating from the radiation beam width by narrowing the beam width using the directivity characteristics of the antenna. For example, assuming an automobile radar whose beam spot is equivalent to one lane width (3.5 m) of a road 70 m ahead, the antenna beam width becomes about ± 1.5 °, and the interference wave of an oncoming vehicle traveling in the adjacent lane Can be suppressed.

Further, communication between a car and a road (road-to-vehicle communication)
When spread spectrum is used in the same frequency band to measure the distance between the vehicle and the vehicle, the communication signal and the distance measurement signal interfere with each other, which deteriorates the performance of communication and distance measurement. Therefore, in road-to-vehicle communication, a system has been proposed which uses a circuit for removing an interference signal transmitted from a roadside zone, cancels the interference signal, and then measures the distance between vehicles.

[0007]

In the above-described polarization plane control, which is one of the conventional interference suppression techniques, the interference wave of an oncoming vehicle can be effectively suppressed. However, the transmitted wave of the parallel running vehicle is radiated to the target vehicle of the own vehicle, and the reflected wave is received by the receiving antenna of the own vehicle, or the transmitted wave of the parallel running vehicle is radiated to the target vehicle of the parallel running vehicle. When the reflected waves are received by the own vehicle's receiving antenna, these reflected waves become interference waves for the own vehicle, and it is difficult to suppress these interference waves by polarization plane control.

Although it is possible to suppress the interference wave of the oncoming vehicle by reducing the directivity of the antenna, the interference control by the directivity characteristics of the antenna decreases as the distance between the own vehicle and the oncoming vehicle increases. .

Further, if the beam is narrowed down too much to suppress the interference, the target vehicle deviates from the reception range of the antenna at the curve, and it becomes difficult to measure the inter-vehicle distance of the target vehicle which should be measured.

Further, in order to secure a measurement range of a sufficient angle range larger than the antenna beam with the narrow beam antenna, a method of mechanically driving the antenna or an electronic beam switching by a multi-beam using a lens antenna or the like. It is necessary to add a beam scanning function such as a method.
It is necessary to secure a wide angle in order to support multi-targets or to perform inter-vehicle communication, and the wide angle increases interference signals.

Further, as proposed in the above-mentioned reference (2), when an interference canceling circuit is used for road-to-vehicle communication, since a PN code used for spreading a signal transmitted from a roadside band is known, reception is difficult. There is no need to extrapolate from the signal. FIG. 4 is a block diagram of an inter-vehicle distance system in the case where an interference canceling circuit is used for the road-vehicle communication.

In FIG. 4, reference numeral 101 denotes an antenna;
Is an interference canceling system, 111 is a first matched filter (MF1), 112 is a peak detection unit, 113 is a delay time detection unit, 114 is a distance measurement unit, 115 is a PN1 reception power estimation unit, and 116 is a PN1 reception signal estimation unit. 117, an adder, 118, a second matched filter (MF2), 11
9 is a data demodulation unit.

On the other hand, since a unique PN code used for an interference wave from another vehicle is unknown, a means for acquiring a unique PN code used by another vehicle is required to remove the interference wave. It is essential.

The present invention has been made in view of the above circumstances, and has been developed in consideration of the above-mentioned circumstances.
A code using an interference elimination processing device capable of improving the distance detection error rate by performing inter-vehicle distance measurement after removing a replica signal of an interference wave created using the acquired PN code. An object of the present invention is to provide a diffusion radar inter-vehicle distance measurement system.

[0015]

According to the present invention, there is provided a spread spectrum radar inter-vehicle distance measuring system using an interference elimination processing apparatus, wherein a base station transmitting section uses a common PN. Means for alternately transmitting a data area spread with a code and a data area spread with a unique PN code assigned to each vehicle; and
Means for acquiring a unique PN code assigned to the other vehicle, means for generating the acquired unique PN code of the other vehicle, means for despreading with the unique PN code assigned to the other vehicle, and transmission from the other vehicle. Means for estimating propagation path information of the interference wave, means for re-spreading a replica signal of the interference wave using a unique PN code and propagation path information assigned to another vehicle, and a replica signal of the interference wave from a received signal. Means for subtracting the replica signal of the interference wave, despreading with the unique PN code assigned to the own vehicle, and correlation power output obtained as a result of despreading with the unique PN code assigned to the own vehicle. And a means for calculating an inter-vehicle distance from a phase difference between the obtained correlation peak position and the transmission.

[2] A spread spectrum radar inter-vehicle distance measuring system using the interference elimination processing apparatus according to [1], wherein the means for acquiring a unique PN code assigned to the other vehicle includes: The vehicle receiving the transmission signal is provided with means for acquiring the transmitted vehicle's unique PN code by despreading with the common PN code. And

[3] A spread spectrum radar inter-vehicle distance measurement system using the interference elimination processing apparatus according to [1], wherein the means for estimating propagation path information of an interference wave transmitted from the other vehicle is common. It is characterized by comprising means for estimating propagation path information based on a signal despread by a PN code and a result of passing the signal through a decision unit.

[4] In the spread spectrum radar inter-vehicle distance measurement system using the interference elimination processing apparatus described in [1], means for improving the distance detection error rate by connecting the interference elimination units in multiple stages is provided. It is characterized by doing.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram (part 1) of a baseband processing unit in an SS radar inter-vehicle distance measurement system using an interference removal processing apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a baseband transmitting unit. This baseband transmitting unit 1 is used to measure the inter-vehicle distance between the transmitting vehicle (vehicle A) and the target vehicle, vehicle B. _A first PN code generator 2 for generating a unique code PNA to be used, a second PN code generator 3 for generating a common PN code PN _COMMON used for communication with another vehicle, a frame generator 4, a multiplier 5, 6, switch (S
W) 7.

Reference numeral 8 denotes a D / A converter, 9 denotes a low-pass filter (LPF), 10 denotes an RF (radio) unit, 11 denotes a transmitting antenna, 13 denotes a receiving antenna, and 14 denotes an RF (radio).
Parts, 15 and 16 are low-pass filters (LPF), 17,
18 is an A / D converter, 19 and 20 are multipliers, 21 and 22
Is an accumulator section, 23 is a complex operation section, 24 is a propagation path estimator, 25 is a determiner, 26 is a partner vehicle information detector,
27 is a PN code generator for the other vehicle, 28 and 30 are multipliers, 29 is a frame generator, 31 is a switch (SW),
32 is a complex operation unit, and 33 and 34 are low-pass filters (L
PF), 35 and 36 are delay circuits, 37 and 38 are adders,
Reference numeral 40 denotes an interference wave removal processing device.

As described above, the own vehicle (vehicle A), which is the transmitting vehicle,
Are known data symbols (data information is all "1") used for measuring the inter-vehicle distance to the target vehicle B, the ID number of the own vehicle (vehicle A), the vehicle position, and the unique PN of the own vehicle. It is composed of data sections of vehicle information to be transmitted to other vehicles such as codes, and is framed by the frame generation unit 4.

The framed data is the first P
Unique PN assigned to each vehicle from N code generator 2
The code and the PN code from the second PN code generator 3 are spread by a PN code common to all vehicles. For a known data section (all “1”), a signal spread with a PN code from the first PN code generator 2 is transmitted, and
For the data section for transmitting vehicle information, the second
Is switched by a switch (SW) 7 so that the signal spread by the common PN code from the PN code generator 3 is transmitted.

After that, D / A conversion by the D / A converter 8 and LPF processing by the LPF 9 are performed, modulated into an RF signal, and transmitted from the transmission antenna 11.

FIG. 2 shows a signal framed by the frame generator shown in FIG. 1 and P to be spread with respect to the signal.
It is a figure showing relation of N code.

The signal received by the receiving antenna 13 is RF
In the section 14, the RF signal is demodulated into a BB signal,
After passing through the PFs 15 and 16, the digital signals subjected to A / D conversion by the A / D converters 17 and 18 are passed through the baseband unit (baseband reception signals 9A and 9B). Reference numeral 40 denotes a circuit that removes an interference wave transmitted from an oncoming vehicle.

In the circuit 40 for removing the interference wave,
The outputs of the LPFs 33 and 34 are minus at the adders 37 and 38, and the outputs of the delay circuits 35 and 36 are plus at the adders 37 and 38. That is, the outputs of the LPFs 33 and 34 are
Since the received signals 9A and 9B are the replica signals of the interference wave and include the desired signal and the interference signal, the estimated replica signals are subtracted by the adders 37 and 38.

FIG. 3 is a block diagram (part 2) of a distance measurement processing unit of an SS radar inter-vehicle distance measurement system using an interference removal processing apparatus according to an embodiment of the present invention.

In this figure, 41 is a delay circuit, 50 is a distance measurement processing unit, 51 and 52 are multipliers, 53 and 54 are accumulator units, 55 is an I-phase multiplier, 56 is a Q-phase multiplier,
57 is an adder, 58 is a peak detector, and 59 is an inter-vehicle distance calculation unit.

The signal obtained by subtracting the estimated interference signal of the oncoming vehicle (ports 39A and 39B in FIG. 1) is passed to the distance measurement processing unit 50 shown in FIG. 3 to generate a first PN code of the own vehicle. By despreading with the PN code generated by the PN code generator 2, the correlation value of each I phase and Q phase is calculated. In order to perform power calculation from signals of correlation values of I and Q phases, I
After passing through the phase multiplier 55 and the Q-phase multiplier 56, the signal passes through an adder 57. The peak detector 58 calculates the position where the correlation peak appears from the signal passing through the adder 57. Thereafter, the inter-vehicle distance calculating section 59 obtains the inter-vehicle distance from the phase difference between transmission and reception.

As described above, according to the present invention, the inter-vehicle distance can be measured by the spread spectrum (SS) system by measuring the delay time, which is the phase difference between transmission and reception.
The own vehicle (vehicle A) as the transmitting vehicle is the target vehicle B
The data area for measuring the inter-vehicle distance to the vehicle is all known data of “1”.

The data to be transmitted is composed of this known data section and a data section of vehicle information to be transmitted to another vehicle, such as the ID number of the own vehicle (vehicle A), the vehicle position, and the unique PN code of the own vehicle. The frame is formed by the unit 4. The framed data is spread with a unique PN code assigned to each vehicle and a PN code common to all vehicles.

For a known data section (all “1”), a signal spread with a unique PN code is transmitted.
Further, for a data section for transmitting vehicle information, a switch (SW) 7 switches so that a signal spread with a common PN code is transmitted. After converting the digital signal into an analog signal, the signal is subjected to LPF processing, modulated into an RF signal, and transmitted from the transmitting antenna 11.

While the transmission is BPSK modulation, the receiving side performs QPSK demodulation because of phase rotation of the propagation path. The signal received by the receiving antenna 13 is demodulated from the RF signal to a BB signal in the RF unit 14, and the LPF 15,
After passing through 16, the A / D converted digital signal is the baseband received signal (9A, 9B).

In order to remove the interference wave, it is first necessary to know the unique PN code used by the oncoming vehicle from the received signal. Therefore, the second PN code generator 3
The I-phase baseband received signal 9A and the Q-phase baseband received signal 9B are despread using the PN code generated in the step (1), and correlation detection is performed.

Since the I-phase signal and the Q-phase signal after despreading contain propagation path information, they are input to the propagation path estimator 24 to determine the propagation path information of the oncoming vehicle. Channel estimator 24
Conjugate signal (Ae ^je1 ) ^* [e
₁ is a signal (11) obtained by despreading θ] with a matched filter.
A, 11B), the channel information can be erased,
A decision symbol 25 can generate a received symbol.

Since the transmitting side does not transmit the Q phase,
The phase reception symbol value is “0”.

The unique PN code assigned to the oncoming vehicle can be obtained by demodulating the received symbol by the other vehicle information detector 26. Based on the information obtained by the other vehicle information detector 26, a PN code generator 27 for the other vehicle generates a PN code unique to the oncoming vehicle. Opponent vehicle information detector 26
The vehicle information of the oncoming vehicle and the known data (all data information is “1”) used for measuring the inter-vehicle distance obtained by the oncoming vehicle are framed by the frame generator 29.

The common P is applied to the vehicle information data of the oncoming vehicle.
The switch (SW) 31 switches the signal spread by the N code so as to output a signal spread by the unique PN code of the oncoming vehicle for known data whose data information is all “1”. This signal contains the oncoming vehicle propagation path information (A
e ^je1 ) [e ₁ is θ], and the LPFs 33 and 34 perform filter processing to create a replica signal of the interference wave.

These I-phase and Q-phase replica signals are the I-phase reception signal (9A) and the Q-phase reception signal (9B).
, And the interference removal processing is completed. At this time, the signal 1 is set so that the data at the same
9A and 19B are adjusted by delay circuits 35 and 36.

After canceling the interference wave of the oncoming vehicle, the I-phase and Q-phase correlation powers are despread by the PN code generated by the first PN code generator 2 for generating the own PN code of the own vehicle. calculate. From the peak position of this correlation power,
By detecting the phase difference between transmission and reception, the following distance can be obtained. Rather than directly calculating the inter-vehicle distance from the baseband reception signal, by measuring the inter-vehicle distance after canceling the interference signal of the oncoming vehicle, the distance detection error rate can be improved.

As described above, according to this embodiment, all the vehicles can be demodulated by spreading with the PN code common to all the vehicles, and the unique PN of the oncoming vehicle is obtained from the demodulated data.
You can get the sign. By obtaining the unique PN code of the oncoming vehicle, an estimated interference signal can be created, and the distance detection error rate can be improved by canceling the replica signal of the interference wave.

In the above embodiment, an example in which the present invention is applied to an SS radar inter-vehicle distance measuring system for removing an interference wave transmitted from an oncoming vehicle has been described. However, by using a common spreading code, a unique PN code of another vehicle can be obtained. If it is known, it can be applied to inter-vehicle communication.

Further, the present invention is not limited to the above-described embodiment, and various modifications are possible based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0046]

As described above, according to the present invention, the following effects can be obtained.

By spreading with a PN code common to all vehicles, all vehicles can demodulate, and the unique PN code of the oncoming vehicle can be obtained from the demodulated data. Oncoming vehicle specific P
By obtaining the N code, an estimated interference signal can be created, and the distance detection error rate can be improved by canceling the replica signal of the interference wave.

[Brief description of the drawings]

FIG. 1 is a block diagram (No. 1) of a baseband processing unit in an SS radar inter-vehicle distance measurement system using an interference removal processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a signal framed by a frame generation unit shown in FIG. 1 and a PN code to be spread on the signal.

FIG. 3 is a block diagram (No. 2) of a distance measurement processing unit of the SS radar inter-vehicle distance measurement system using the interference removal processing apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram of a conventional SS radar inter-vehicle distance system using an interference cancellation processing device in road-to-vehicle communication.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 baseband transmitter 2 first PN code generator (unique PN code) 3 second PN code generator (common PN code) 4,29 frame generator 5,6,19,20,28,30,51 , 52 Multiplier 7, 31 Switch (SW) 8 D / A converter 9, 15, 16, 33, 34 Low-pass filter (L
PF) 10 RF (wireless) unit 11 transmitting antenna 13 receiving antenna 14 RF (wireless) unit 17, 18 A / D converter 21, 22, 53, 54 accumulator unit 23, 32 complex operation unit 24 propagation path estimator 25 judgment Apparatus 26 Opponent vehicle information detector 27 PN code generator for opponent vehicle 35, 36, 41 Delay circuit 37, 38, 57 Adder 40 Interference wave removal processing device 50 Distance measurement processing unit 55 I-phase multiplier 56 Q-phase multiplier 58 Peak detector 59 Distance calculation unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kiyohito Tokuda 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F-term (reference) 5J070 AA04 AB10 AC02 AD02 AE01 AF03 AH04 AH31 AH33 AH34 AH39 AH50 AJ05 AJ13 AK22 AK26 AK35 BF02 5K022 EE02 EE11 EE21 EE31 EE35

Claims (4)

[Claims] (A) means for alternately transmitting a data area spread with a common PN code and a data area spread with a unique PN code assigned to each vehicle in a baseband transmitting section; In the receiving unit, means for acquiring a unique PN code assigned to another vehicle, means for generating the acquired unique PN code of the other vehicle, means for despreading with the unique PN code assigned to the other vehicle,
Means for estimating propagation path information of an interference wave transmitted from another vehicle, means for re-spreading to create a replica signal of the interference wave using a unique PN code and propagation path information assigned to the other vehicle, and Means for subtracting the replica signal of the interference wave, and after subtracting the replica signal of the interference wave,
Means for despreading with the unique PN code assigned to the own vehicle, means for obtaining a peak position from the obtained correlation power output as a result of despreading with the unique PN code assigned to the own vehicle, A spread spectrum radar inter-vehicle distance measurement system using an interference removal processing device, comprising: means for calculating an inter-vehicle distance from a phase difference from transmission. 2. A spread spectrum radar inter-vehicle distance measurement system using the interference cancellation processing apparatus according to claim 1, wherein said means for acquiring a unique PN code assigned to said other vehicle spreads information with a common PN code. Transmitting the unique PN code of the transmitting vehicle as data information, and the vehicle receiving the transmission signal is provided with means for obtaining the unique PN code of the transmitted vehicle by despreading with the common PN code. Spread spectrum radar inter-vehicle distance measurement system using an interference cancellation processor. 3. A spread spectrum radar inter-vehicle distance measurement system using the interference cancellation processing device according to claim 1, wherein said means for estimating propagation path information of an interference wave transmitted from said another vehicle is a common PN code. A spread spectrum radar inter-vehicle distance measurement system using an interference removal processing device, comprising: means for estimating propagation path information based on a signal despread in step (1) and a determination result obtained by passing the signal through a determination unit. 4. A spread spectrum radar inter-vehicle distance measurement system using the interference cancellation processing device according to claim 1, further comprising means for improving a distance detection error rate by connecting interference cancellation devices in multiple stages. A spread spectrum radar inter-vehicle distance measurement system using an interference cancellation processing device characterized by the following.