JPH08304530A - Radar device and spectrum peak-detection method - Google Patents

Abstract

PURPOSE: To accurately identify a plurality of targets even when a plurality of peak values appear by providing, for example, a spectrum extraction means, a peak detection means, and a maximum peak value determination means. CONSTITUTION: An oscillator 11 oscillates a wave, which is modulated at a specific frequency, and the wave is subjected to FM modulation by an FM modulator 12, and is transmitted from a transmission/reception antenna 10 toward a target via a circulator 13. On the other hand, a reflection wave from the target is received by the antenna 10 and is transmitted to a mixer 14 via the circulator 13. The difference frequency between the FM modulation wave and the reflection wave is taken out as a beat signal by the mixer 14 and is transmitted to a signal processing part 20 in the form of a digital signal via an intermediate frequency amplifier 15, a flat amplifier 16, and an A/D conversion part 17. The processing part 20 performs FFT to the received digital signal to obtain a frequency spectrum and at the same time detects the position of a peak value from the obtained frequency spectrum, thus calculating the distance to the target and a relative speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device mounted on an automobile or the like and a spectrum peak detecting method used in the radar device.

[0002]

2. Description of the Related Art This type of so-called
Since the on-vehicle radar device can measure the distance and the relative speed of a vehicle traveling in front, it is expected to be useful for preventing a collision accident of the vehicle. Further, the on-vehicle radar device includes a millimeter wave radar device that uses a millimeter wave band radio signal, and the millimeter wave radar device also includes an FM that uses a continuous wave (CW) of an FM modulated wave. -There is a CW radar device.

Conventionally, as the FM-CW radar device,
The M-modulated wave is continuously transmitted as a transmission wave toward an object such as an automobile, and the reflected wave reflected by the object is received as a reception wave to extract beat frequency components of the transmission wave and the reception wave. The extracted beat frequency component is, for example, FFT (Fast Fourier Trans).
form) has been proposed to convert to a discrete frequency spectrum. By processing the discrete frequency spectrum obtained in this way, the distance to the object and the relative speed of the object can be calculated. The peak position of the frequency spectrum is usually used to calculate the distance and the relative velocity. Therefore, detecting the peak position of the frequency spectrum is extremely important for this type of radar device.

[0004]

When the above FM-CW radar device is used as a vehicle-mounted radar device,
The transmitted wave is not always reflected from a single object, but may be reflected by multiple objects.
For example, even if a plurality of cars are traveling in front of a car equipped with a radar device at intervals in the traveling direction, when these cars are viewed from a car equipped with a radar device in the rear, a plurality of cars ahead Appear to be running next to each other. In such a case, the radio waves reflected by a plurality of automobiles are received as the received waves of the radar device. Therefore, a plurality of peak values appear in the frequency spectrum obtained from such a received wave and a transmitted wave.

However, since the peak detection algorithm used in the past detects only the maximum peak value among a plurality of peak values, it can detect only the distance and the relative speed with respect to a single object. There is a drawback that.

An object of the present invention is to provide a radar device capable of calculating a distance, a relative speed and the like according to each peak value even when a plurality of peak values appear.

Another object of the present invention is to
It is to provide a peak detection method when a plurality of peak values exist.

[0008]

According to the present invention, a radar device for detecting a distance to an object and a relative speed of the object by using the radio signal is processed by processing the radio signal. A spectrum extracting means for extracting a spectrum related to the object, and a peak detecting means for detecting a peak value of the spectrum, wherein the peak detecting means detects a position having a peak value in the spectrum. Means, means for defining a predetermined range before and after sandwiching the position of the peak value, level at each position of the predetermined range is detected, and the peak value is compared with each level at the predetermined range position, the predetermined range A radar device having a determining means for determining whether or not the peak value is the maximum peak value is obtained from the change in the level inside the radar device.

Further, according to the present invention, in a spectrum peak detecting method for detecting a distance to an object and a relative speed of the object using a wireless signal, the object is processed by processing the wireless signal. The maximum peak value by extracting the frequency spectrum of the radio signal related to an object, detecting the peak value in the frequency spectrum, and determining whether the peak value is the maximum peak value within a predetermined range. Even when there are a plurality of peaks in the frequency spectrum, a spectrum peak detection method capable of identifying the plurality of maximum peak values can be obtained.

[0010]

According to the present invention, by observing the level change within a predetermined range before and after the position of the peak value with respect to a single peak value, it is determined whether or not the peak value is the maximum peak value within the predetermined range. Therefore, even if there are a plurality of peak values outside the predetermined range, the plurality of peak values can be individually separated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radar apparatus and its spectrum peak detection method according to an embodiment of the present invention will be described below with reference to the drawings.

First, referring to FIG. 1, there is shown an overall configuration of a radar apparatus according to an embodiment of the present invention. The illustrated radar device includes a transmission / reception antenna 10, from which an FM-modulated FM-modulated wave is transmitted toward a target such as an automobile, and a reflected wave reflected by the target is transmitted / received by the transmission / reception antenna 10. To be received.

In order to transmit the FM modulated wave, the radar device has an oscillator 11 composed of a voltage controlled oscillator (VCO), an FM modulator 12, and a circulator 13. Here, the oscillator 11 has a predetermined oscillation frequency f
The modulated wave of o is oscillated and sent to the FM modulator 12. This modulated wave is FM-modulated by the FM modulator 12 at the frequency fd, and then passes through the circulator 13.
An FM modulated wave is transmitted from the transmitting / receiving antenna 10 to the target. The FM modulated wave may be frequency-converted when transmitted from the transmitting / receiving antenna 10.

On the other hand, the reflected wave reflected by the target is received by the transmission / reception antenna 10 and then sent to the mixer 14 via the circulator 13. In the mixer 14, the frequency of the difference between the FM modulated wave and the reflected wave is taken out as a beat signal, and is passed through the intermediate frequency amplifier 15, the flat amplifier 16 and the A / D conversion section 17 in the form of a digital signal according to the present invention. Is sent to the signal processing unit 20 according to.

As will be described later, the signal processing section 20 obtains a frequency spectrum of the received digital signal by FFT, detects the position of the peak value from the obtained frequency spectrum, and finally, the radar device concerned. The distance R between the target and the target and the relative speed V are calculated.
As is known, the distance R is (fo + fd) /
2 takes a value proportional to 2, while the relative velocity V is (fo-
Although the value is proportional to fd) / 2, the calculation of the distance R and the relative speed V is not directly related to the present invention, and thus the description thereof is omitted here.

The signal processing unit 20 shown in FIG. 1 detects the position of each peak value even if a plurality of peak values appear in the frequency spectrum as a result of the presence of a plurality of targets, and a plurality of peak values are detected. It is characterized in that the distance R and the relative speed V between the target and the target can be calculated.

The operating principle of the signal processor 20 of FIG. 1 will be described with reference to FIGS. 2 and 3. First, in the signal processing unit 20, as a result of performing FFT on the received digital signal,
As shown in FIGS. 2 and 3, it is assumed that a discrete frequency spectrum is obtained. Here, the horizontal axis of FIGS. 2 and 3 represents the frequency (n), while the vertical axis represents the frequency level F (n). In the illustrated example, the frequency (n) is variable in the range of 0 to N. Further, a threshold level Th (n) is set in order to detect the position of the peak value, that is, the frequency position, and the peak value is detected by the frequency level F (() exceeding the threshold level Th (n). Only for frequencies (n) with n). The threshold level Th (n) shown in the figure is set higher in a state where no digital signal is received than in a case where a digital signal is received, in order to prevent malfunction due to noise or the like.

In FIG. 2, the frequency level F (n) and
The threshold level Th (n) is compared, and first, n that satisfies F (n) ≧ Th (n) is determined and is determined as the peak determination start position Ps.

Next, from the peak determination start position Ps, n to
In the section of Pw, F (n)> F (N + α) (where α = 1
Up to Pw) is continuously established, and this n is set as a temporary peak position P ′. Note that Pw is a sufficiently small section with respect to N, and in practice, a frequency section corresponding to about ½ of the length of the car body is desirable. In the case of FIG. 2, the provisional peak position P ′ is at the fourth frequency position from the beginning.
Will be calculated. The above-described operation represents that the section Pw is set backward from the temporary peak position P '.

On the other hand, when the temporary peak position P'is obtained, as shown in FIG. 3, the section Pw is set in front of the temporary peak position P ', and F (P')> F (P'- It is determined whether or not α) is continuously satisfied. When this equation is established, n at this time is set as the true peak position P01.

The above operation will now be described in more detail with reference to the waveform chart shown in FIG. It can be seen that the waveform in the example of FIG. 4 shows the peak value at the positions of ,,. Of these, at the peak position, although the downlink is temporarily generated behind that position due to noise, the downlink is Pw.
This position is not recognized as a temporary peak position because it is not continuous. On the other hand, at the peak position of, Pw
Since there are consecutive downwards, the peak position of is set as the position P01 of the true peak value.

Further, there is a downward line Pw times in succession behind the peak position, but since there is a place higher in level than the peak position in the front, the true peak value is I will not admit it. Furthermore, at the position of, before and after that,
Since there are consecutive Pw times of downward movement, this position is also recognized as the true peak value position P02. By repeating such an operation, the positions of a plurality of peak values can be sequentially detected.

Referring to FIG. 5, there is shown a flowchart for detecting the position of the above-mentioned peak value. In the illustrated example, a flag (hereinafter, FLAG) indicating whether or not to skip forward processing is used.
In this example, when FLAG is 0, the forward processing is skipped, while when FLAG is 1,
This means that processing forward is not skipped.

When the processing is started, first, FLAG becomes 0.
Is set, and skip of the forward process is designated (step S1), and then Pw + 1 is set as the frequency n (step S2). Next, the level F (n) at the position of the set frequency n is the threshold level T
If h (n) or more is determined (step S3), the level is smaller than the level F (n), and if an upslope is detected, FLAG is set to 1 (step S4), and the forward process is skipped. It is executed without being done. This time,
The frequencies n are sequentially added one by one (step S5), and this operation is continued until the frequency n becomes equal to N (step S6). When the frequency n becomes equal to N in step S6, the above processing operation is stopped.

On the other hand, while the operations of steps S3 to S6 are being repeated, in step S3, when FLAG is 1 and the level F (n) at the frequency n is equal to or higher than the threshold level Th (n), It is detected by the FLAG 1 that there is an upward slope, and this level F
(N) is set as the maximum value MAX (step S
7). At this time, the count value of the counter indicating the range of Pw is set to 0 (step S8). Then, the frequency n is incremented by 1 (step S9), and it is detected whether or not the frequency n is equal to N (step S9).
10) If they are equal, the process ends.

When the frequency n is not equal to N in step S10, it is determined whether the frequency level F (n) is equal to or more than the maximum value MAX so far (step S11).
If the frequency level F (n) is greater than or equal to the maximum value, FLA
G is set to 1 and it is determined that there is an upslope (step 1
2) Return to step S7 for backward processing.

When it is detected in step S11 that the frequency level F (n) is smaller than the maximum value MAX, the count value is incremented by 1 (step S13), and the result of the count-up is equal to Pw. It is determined whether or not (step S14). Unless the count-up result is equal to Pw, the processing operation returns to step S9, and the above-described operation is repeated.

When the count result becomes equal to Pw in step S14, it is determined whether FLAG is 0 or not (step S15). If FLAG is 0, the level is higher than the threshold level Th and the past Pw. It shows that there is no uphill during the section. Therefore, when FLAG is 0, the process proceeds from step S15 to step S5, the forward process is skipped, and the backward process is executed.

On the other hand, in step S15, FLAG
Is not 0, n-Pw-1 is set as the frequency n (step S16), and the count value is 0.
Is set to (step S17). At this point, FL
AG is set to 0 (step S18), and it is determined whether the frequency level F (n) is smaller than the maximum value MAX (step S19).

As a result of the judgment, when the frequency level F (n) is smaller than the maximum value MAX, the count value of the counter is incremented by 1 (step S20), and subsequently it is judged whether or not the count value is equal to Pw. (Step S21). In step S21, when the count value does not match Pw, the frequency n is set to n.
-1 is set (step S22), and step S19
Return to

By repeating the same operation thereafter, the frequency level F (n) larger than the maximum value MAX becomes P.
If it is determined that it is not within the range of w (step S2
1), the frequency position is determined as P0 (step S23).

In this embodiment, even after P0 is once determined in step 23, the process returns to step S5, and the same maximum value MAX and the corresponding frequency position P0 are determined until the frequency n matches N. The action for is performed.

Referring to FIG. 6, a hardware circuit for performing the operation of FIG. 5 is shown. The circuit shown in the figure receives the received digital signal and performs FFT operation on the F signal.
The FT calculator 21 is provided. The FFT calculator 21 outputs the frequency level F (n) as waveform data as a calculation result and the address ADRS indicating the position corresponding to the frequency n. It The waveform data is sequentially stored in the addresses of the RAM 22 under the control of the controller 30.

On the other hand, the threshold level Th (n) is stored in the ROM 23, and the threshold level Th (n) is output from each address of the ROM 23 under the control of the controller 30. Furthermore, RAM
22 is connected to the first to third comparators 24, 26, 28, and the first to third comparators 24, 26,
The switch 28 is selectively placed in an operating state by a switch 31 which performs a switch operation under the control of the controller 30. The RAM 22 is also connected to the RAM 25, and RA
The output of M25 is given to the second comparator 26, and
It is also supplied to the output amplifier 32.

Furthermore, the second and third comparators 26 and 28 are provided.
The comparison result of the first and second counters 27 and 29 is
And the first and second counters 27 and 29 are connected to a controller 30. Second illustrated
The counter 29 of is connected to the output amplifier 32.

In the hardware circuit having this configuration, the first comparator 24 compares the waveform data of each frequency with the threshold level, and gives the comparison result to the controller 30. When the maximum value of the waveform data is detected, the controller 30 stores the maximum value in the RAM 25 and sequentially compares it with the waveform data from the RAM 22 for the purpose of post-processing, and the comparison result by the first counter 27. To count. The count value is given to the controller 30, and it is detected whether or not it is the maximum value MAX within the range of Pw.

On the other hand, the third comparator 28 is activated during the forward processing, and compares the waveform data with the maximum value MAX stored in the RAM 25. The comparison result in the third comparison circuit 28 is counted by the second counter 29, and the controller 30 determines whether or not it is the maximum value MAX in the frequency range of Pw.

When the maximum value within the range of ± Pw is stored in the RAM 25, the output amplifier 32 operates as the second counter 29.
The output state of the RAM 25 is changed to the output state, and the output of the RAM 25 is output from the output amplifier 32 as a peak level.

From the above, it can be seen that the hardware circuit of FIG. 6 can perform the operation shown in FIG.

[0040]

According to the present invention, in a radar device adopting the FM-CW method, even if a plurality of peak values exist in the frequency spectrum obtained as a result of FFT, the positions of these peak values can be accurately obtained. Therefore, there is an advantage that a plurality of targets can be identified.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a radar device according to an embodiment of the present invention.

FIG. 2 is a spectrum waveform diagram for explaining the operation of the radar device shown in FIG.

3 is a spectrum waveform diagram for explaining another operation of the radar device shown in FIG. 1. FIG.

FIG. 4 is a waveform diagram for explaining the operation of the radar device in FIG. 1 more specifically.

FIG. 5 is a flowchart for explaining a peak detecting operation in the radar device.

FIG. 6 is a circuit diagram for realizing a radar device according to an embodiment of the present invention.

[Explanation of symbols]

 10 Transmitting / Receiving Antenna 11 Voltage Controlled Oscillator 12 FM Modulator 13 Circulator 14 Mixer 15 Intermediate Frequency Amplifier 16 Flat Amplifier 17 A / D Converter 20 Signal Processing Unit 21 FFT Operation Unit 22 RAM 23 ROM 24 First Comparator 25 RAM 26 26th 2 comparator 27 1st counter 28 3rd comparator 29 2nd counter 30 Controller 31 Switch 32 Output amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichiro Kanda 1-4-24 Jomi, Chuo-ku, Osaka-shi, Osaka NEC Home Electronics Co., Ltd.

Claims (7)

[Claims] 1. A radar device for detecting a distance to an object and a relative speed of the object using a wireless signal, and processing the wireless signal to extract a spectrum associated with the object. And a peak detecting means for detecting the peak value of the spectrum, wherein the peak detecting means sandwiches the position of the peak value and the means for detecting the position having the peak value in the spectrum. A means to set a predetermined range before and after,
Whether to detect the level at each position in the predetermined range, compare the peak value with each level at the predetermined range position, and determine whether the peak value is the maximum peak value from the change in the level within the predetermined range. And a determination means for determining. 2. The wireless signal according to claim 1, wherein the wireless signal is F
A radar device which is a continuous wave (CW) of an M-modulated wave. 3. The spectrum extracting means according to claim 2, wherein the means for transmitting the FM modulated wave as a transmission wave toward the target object, the transmission wave and the reception wave from the target object, A radar device comprising: a unit for detecting a beat between the transmitted wave and the received wave; and a unit for generating a spectrum of the beat frequency. 4. A spectrum peak detection method for detecting a distance to an object and a relative speed of the object using a wireless signal, wherein the wireless signal associated with the object is processed by processing the wireless signal. By extracting the frequency spectrum of the signal, detecting the peak value in the frequency spectrum, and determining whether or not the peak value is the maximum peak value within a predetermined range, the maximum peak value is plural in the frequency spectrum. Even if it exists
A spectrum peak detection method characterized by being able to identify a plurality of maximum peak values. 5. The wireless signal according to claim 4, wherein the wireless signal is F
A spectrum peak detection method, which is a continuous wave (CW) of an M-modulated wave. 6. The continuous wave according to claim 5, wherein the continuous wave of the FM modulated wave is transmitted as a transmission wave to an object, and
A spectrum peak detection method characterized by being received as a received wave from an object. 7. The frequency spectrum according to claim 6, wherein the beat frequencies of the transmission wave and the reception wave are F
FT (Fast Fourier Transform)
m) A spectrum peak detection method characterized by being obtained by