JPH0550383U - Millimeter-wave radar range velocity measuring device - Google Patents

Abstract

(57) [Summary] [Objective] The present invention measures the distance and speed by frequency-modulating the transmission signal of a continuous wave radar and at the same time receiving the reflection signal from the target, and at the shortest distance less than the resolution of the fast Fourier analyzer. It is intended to effectively use the beat signal according to the above. [Structure] A millimeter-wave radar range-velocity measuring device that obtains a distance and a velocity from a beat signal between a reception signal and a transmission signal by frequency-modulating the transmission signal of a transmission signal of the continuous-wave radar and appropriately repeating it On the other hand, when the spectrum level of the DC component and the frequency component adjacent to the DC component of the frequency components obtained by frequency-analyzing the beat signal increases above a predetermined value, it is determined that the target is close.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a millimeter-wave radar range-velocity measuring device for performing frequency modulation on a transmission signal of a continuous-wave radar and simultaneously receiving a reflected signal from a target to measure a distance and a velocity. In particular, the present invention aims to effectively utilize the beat signal related to the close range which is less than the resolution of the fast Fourier analyzer.

[0002]

[Prior Art]

 Conventionally, as a technology relating to a millimeter wave radar distance velocity measuring device in such a field, there is one described in "Radar Technology" (Incorporated Association: The Institute of Electronics, Information and Communication Engineers). When the transmission signal of the continuous wave radar is frequency-modulated and repeated appropriately and the beat is taken from the reception signal, the beat frequency f can be expressed as f = 4R · fm · Δf / c (1) . Here, R is the distance to the target, fm is the repetition frequency of frequency modulation, Δf is the frequency shift width, and c is the speed of light. The beat frequency f is frequency-analyzed by a fast Fourier analyzer and obtained as a peak frequency, whereby the distance to the target is obtained. Next, when the target is moving, due to the Doppler effect, the beat signal frequency f is the beat signal frequency f when the target is fixed, and the Doppler frequency fp is superimposed on the beat signal frequency f. fp can be expressed as fp = 2 · f0 · V / c (2) Here, f0 is the transmission center frequency. The direction of the frequency of the combined beat signal of f and fp alternates between rising (up) and falling (down) for each modulation cycle, and is therefore given by the following equation.

Fu (up) = f−fp (3) fd (down) = f + fp (4) Therefore, if fu (up) and fd (down) are separately measured for each half cycle of modulation, By combining these as follows, f = {fu (up) + fd (down)} / 2 (5) fp = {fu (up) -fd (down)} / 2 (6) The distance R and the velocity V are obtained from f and fp, respectively.

[0004]

[Problems to be solved by the device]

 However, when the conventional millimeter-wave radar range velocities measuring device is used by mounting it on an automobile, etc., the target is close to the target, and therefore the frequency of the beat signal is low and if there are two cycles or less between the observation zones. However, there is a problem that the resolution becomes lower than that of the frequency analyzer, and the accurate peak frequency cannot be identified, making it difficult to measure the distance.

Therefore, in view of the above problems, it is an object of the present invention to provide a millimeter wave radar range velocity measuring device capable of accurately extracting range information from a beat signal whose peak frequency cannot be identified accurately.

[0006]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention performs the frequency modulation on the transmission signal of the continuous wave radar transmission signal and repeats it appropriately, and calculates the distance and velocity from the beat signal of the reception signal and the transmission signal. In the radar range velocity measurement device, when the spectral level of the DC component and the frequency component adjacent to it among the frequency components obtained by frequency-analyzing the beat signal with respect to the target increases above a predetermined value when the target does not exist, the target Judge that it is very close.

[0007]

[Action]

 According to the millimeter-wave radar range velocity measuring device of the present invention, when the target does not exist in the spectrum level of the DC component and the frequency component adjacent to the DC component among the frequency components obtained by frequency-analyzing the beat signal with respect to the target. By determining that the target frequency has increased beyond the predetermined value, it is possible to determine that the target is in the immediate vicinity even if the accurate peak frequency cannot be identified.

[0008]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a millimeter wave radar range velocity measuring apparatus according to an embodiment of the present invention. The millimeter wave radar distance velocity measuring device shown in the figure is a sensor 1 that transmits a continuous wave signal of triangular wave modulation and mixes the continuous wave signal with a received signal reflected by a target to form a beat signal, and the sensor. A low-pass filter 2 that removes a high-pass signal so that aliasing does not occur when the signal of 1 is sampled, and an A / D (Analog to Digital) that converts the analog signal from the low-pass filter 2 into a digital signal. Converter) A converter 3 and a DSP (Digital Signal Processor) for frequency analysis of the beat signal converted into the digital signal from the A / D converter 3 and processing it into a distance and velocity signal. A signal processing unit 4, a controller 5 for controlling the distance and speed data obtained by the signal processing unit 4, and a display unit 6 for displaying the data controlled by the controller 5. .

FIG. 2 shows the formation of the output signal of the sensor of FIG. As shown by the solid line in this figure (a), a continuous transmission signal of triangular wave modulation is transmitted from the sensor 1, and the signal reflected by the target is received by the sensor 1 as shown by the dotted line. Further, as shown in FIG. 9B, the peak frequency fu of the beat signal on the rising side of the triangular wave modulation and the peak frequency fd of the beat signal on the falling side of the triangular wave modulation are formed by a mixer (not shown).

FIG. 3 is a diagram showing the configuration of the signal processing unit shown in FIG. As shown in the figure, it is composed of a high-speed Fourier analyzer (FFT), and performs a frequency analysis of the signal from the A / D converter 3, and a frequency analysis section 41, and a rising side from the frequency analysis section 41. The peak frequency fu and fd of the falling beat signal are substituted into the above equations (5) and (6) to calculate the distance and speed to the target, and the frequency component from the frequency analysis unit 41. Extraction means 43 for extracting spectral levels of 0, ΔF, 2ΔF, and storage for tabulating and storing the spectral levels of the frequency components 0, ΔF, 2ΔF obtained by the extracting means 43 when there is no target as a background. The spectrum level of the frequency components 0, ΔF, 2ΔF extracted by the storage unit 44 is compared with that of the background frequency components 0, ΔF, 2ΔF from the storage unit 44. If it is larger than this, the determination means 45 for determining that the target exists at the close range is included.

The frequency analysis unit 41 has a frequency resolution of ΔF, and the frequency is analyzed for each resolution. A frequency component 0 indicates a DC component, and ΔF indicates a first component adjacent to the DC component. , 2ΔF represents a second component adjacent to the first component. The above ΔF≈1. It is 5 KHz, and when converted into a distance, it corresponds to about 2 m, and thus 2ΔF corresponds to about 2 m × 2 = 4 m. As described above, the range of 0 to 4 m as the distance to the target is the subject of the present invention.

FIG. 4 is a flow chart for explaining a series of operations of the present invention, FIG. 5 is a diagram for explaining a measurement range by frequency, and FIG. 6 is a DC component, a first component and a second component spectrum. It is a figure which shows a cuttle level. As shown in FIG. 4, the frequency analysis unit 41 performs peak frequency analysis of the peak frequency of the beat signal (step 1). Measure the distance. When the frequency range is 0 to 2ΔF, the presence / absence of a target at a close range is detected by the level-based judgment as described below. As shown in FIG. 6, the DC component of the frequency analysis unit 41, the frequency components of the first component and the second component are extracted by the extracting means 43 (step 2). In the case of background measurement (step 3), it is confirmed that the sensor 1 has no target object, and the spectrum level of the above component is extracted as shown in FIG. 5 (a). To determine the reference level L that there is no target from the background in Fig. 5 (a), the level when there is no target is L0, and the peak frequency is as close as possible (frequency of about 3ΔF: about 4.5m). It is preferable that the level when the target is set is L1 and the S / N ratio is considered in the range of L0 <L <L1 (step 4). When the reference level for the case without a target is set, measure the target. As shown in FIG. 5B, since the spectra of the DC component, the first component and the second component are larger than the level L, it can be determined that the target exists within 0 to 4 m (step 5). This information is displayed on the display 6 via the controller 5 together with the target information of the long distance by the distance / speed calculator 42.

[0013]

[Effect of the device]

 As described above, according to the present invention, it is determined that the spectral level of the direct current component and the frequency component adjacent to the direct current component of the frequency components obtained by frequency analysis of the beat signal with respect to the target has increased above a predetermined value. By doing so, even if the accurate peak frequency cannot be identified, it can be determined that the target is close.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a millimeter wave radar range velocity measuring apparatus according to an embodiment of the present invention.

2 shows the formation of the output signal of the sensor of FIG.

FIG. 3 is a diagram showing a configuration of a signal processing unit in FIG.

FIG. 4 is a flowchart illustrating a series of operations of the present invention.

FIG. 5 is a diagram illustrating a measurement range according to frequency.

FIG. 6 is a diagram showing spectrum levels of a DC component, a first component, and a second component.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sensor 4 ... Signal processing part 41 ... Frequency analysis part 42 ... Distance speed calculation part 43 ... Extraction means 44 ... Storage part 45 ... Judgment means

Claims (1)

[Scope of utility model registration request] 1. A millimeter-wave radar range-velocity measuring device for obtaining a distance and a velocity from a beat signal between a reception signal and a transmission signal by frequency-modulating a transmission signal of a transmission signal of a continuous-wave radar and repeating appropriately. Among the frequency components obtained by frequency-analyzing the beat signal with respect to the target, it is determined that the target is close to a predetermined range when the spectrum level of the DC component and the frequency component adjacent to the DC component increases above a predetermined value. Millimeter-wave radar range and velocity measurement device.