JPH05333143A - Distance and speed measuring device - Google Patents

Abstract

PURPOSE:To prevent a target from being lost since peak frequencies approach frequently to each other due to a noise signal. CONSTITUTION:A distance and speed measuring device to measure relative distance and relative speed to a moving target object 1 from beat signal frequencies of the reflected wave of a radiated reflected continuous radar wave and a continuous radar wave, is provided with a beat signal frequency analyzing means 52 to carry out frequency analysis on beat signals, and is also provided with a peak frequency identification weight forming means 53 to form weight so as to become, large when a frequency difference between peak frequency predictable at a present point of time and peak frequency of the beat signal measured at a present point of time is small as well as to become large when a power level of the peak frequency of the beat signal measured at a present point of time is large, a beat signal determining means 54 to determine a large weight frequency as peak frequency and a distance and speed deriving means 55 to derive the relative distance and the relative speed from the peak frequency of the determined beat signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous radar wave radiated by frequency-modulating a transmission signal, which is reflected by a target, and the reflected wave is received at the same time from the peak frequency of the beat signal of the reception signal and the transmission signal. In particular, the present invention relates to a distance / speed measuring device capable of preventing a target from being lost due to frequent peak frequencies due to a noise signal.

[0002]

2. Description of the Related Art Conventionally, as a technique relating to a distance velocity measuring device in such a field, there has been one described in "Radar Technology" (Incorporated Association: Institute of Electronics, Information and Communication Engineers). In a conventional distance velocity measuring device, a transmitter forms a triangular frequency-modulated transmission signal, and a continuous radar wave (C
W) is radiated to a moving target object such as an automobile.
Then, the reflected wave of the moving target object is mixed with the received signal of the received wave received by the antenna and the transmitted signal of the radiated continuous radar wave to form a beat signal. The frequency analysis of the beat signal is performed, and the relative distance and relative speed to the moving target object are obtained from the peak frequency of the beat signal.

[0003]

By the way, in the conventional distance velocity measuring apparatus, the peak frequency analysis of the beat signal is performed at regular intervals, and the peak frequency is the same as the target movement target considering the traveling speed. Since it changes almost continuously with respect to the object, it can be easily determined that the beat signal analyzed this time and the peak frequency of the beat signal analyzed last time belong to the same moving target object, that is, the identification of the peak frequency. It was

However, when the noise signal frequently appears near the frequency of the beat signal, the peak frequency becomes inconsistent, which makes it difficult to identify the peak frequency of the beat signal, resulting in the problem of loss of the moving target object. Occurs.
Therefore, in view of the above problems, it is an object of the present invention to provide a distance velocity measuring device capable of identifying the peak frequency of a beat signal even when a noise signal frequently appears and preventing loss of a moving target object.

[0005]

In order to solve the above-mentioned problems, the present invention solves the above problems by radiating a continuous radar wave reflected by a moving target object and determining the frequency of the beat signal of the reflected wave and the continuous radar wave. A beat signal frequency analyzing unit, a peak frequency identifying weight forming unit, a beat signal determining unit, and a distance velocity deriving unit are provided in the distance velocity measuring device that measures the relative distance and relative velocity with respect to the moving target object.

The beat signal frequency analysis means analyzes the frequency of the beat signal. The peak frequency identification weight forming means has a frequency difference between the peak frequency of the beat signal measured at the present time from the peak frequency of the past beat signal obtained by the beat signal frequency analyzing means and the peak frequency of the beat signal measured at the present time. A weight is formed such that the smaller the power level is, the larger the power level of the peak frequency of the beat signal measured at the present time is.

The beat signal determining means determines, as a peak frequency, one of the peak frequencies analyzed by the beat signal frequency analyzing means, which has a greater weight by the peak frequency identifying weight forming means. The distance velocity deriving means derives the relative distance and relative velocity of the moving target object from the peak frequency of the beat signal determined by the beat signal determining means.

[0008]

According to the distance velocity measuring device of the present invention, the beat signal frequency analyzing means analyzes the frequency of the beat signal. The frequency difference between the peak frequency predicted at the present time from the peak frequency of the past beat signal analyzed by the beat signal frequency analysis means by the peak frequency identification weight forming means and the peak frequency of the beat signal measured at the present time. Is smaller, the larger is the power level of the peak frequency of the beat signal measured at the present time, the larger is the weight.
Among the peak frequencies analyzed by the beat signal frequency analyzing means by the beat signal determining means, one having a larger weight by the peak frequency identifying weight forming means is determined as a true measured peak frequency. The relative speed and the relative speed of the moving target object are derived from the peak frequency of the beat signal determined by the beat signal determining means by the distance / velocity deriving means. Therefore, even if a peak frequency due to a noise signal that is accidentally close to the predicted peak frequency frequently exists, it can be removed and the moving target object will not be lost, and stable relative distance and relative speed can be obtained. You can

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a distance velocity measuring apparatus according to an embodiment of the present invention. As shown in the figure, a distance velocity measuring device mounted on an automobile or the like continuously transmits an antenna 2 that emits a continuous radar wave (CW) to a moving target object 1 such as an automobile and receives a reflected wave thereof, and a continuous antenna 2. A continuous wave forming transmitter 3 that forms a triangular frequency-modulated transmission signal as a wave and outputs it to the antenna 2, and a reception signal of the reception wave received by the antenna 2 and a transmission signal from the continuous wave forming transmitter 3 are mixed. And a mixer 4 that forms a beat signal, and the frequency of the beat signal from the mixer 4 is analyzed to find the frequency difference between the received signal and the transmitted signal from the frequency of the beat signal, and the frequency difference of the automobile is used. Signal processing means 5 for performing signal processing for obtaining the relative distance and relative speed with respect to the moving target object 1, and displaying the relative distance and relative speed obtained by the signal processing means 5 to the driver. The opponent who is 1 And a display unit 6 to provide a vehicle information.

FIG. 2 is a diagram for explaining the relationship between the continuous radar wave, the reflected wave from the moving target object, and the frequency of the beat signal versus time. In the figure (a), the frequency versus time of the transmission signal is shown, and as shown by the solid line, the transmission signal on which triangular frequency modulation (FM) has been repeatedly formed by the continuous wave forming transmitter 3 is repeatedly formed. A continuous radar wave is output from 2. Further, the antenna 2 receives a repeated signal of frequency-modulated triangular reflected waves as shown by the dotted line in FIG. In the figure (b), the relationship between the beat signal and the time between the transmission signal and the reception signal is shown. The beat signal is obtained as the output of the mixer 4, and is obtained when the peak frequency fb of the beat signal obtained when the frequency of the transmission signal or the reception signal rises is fu and when it falls, as shown in FIG. If the frequency fb of the beat signal to be generated is fd, the following equation is obtained.

Fu = fr + fp (1) fd = fr -fp (2) where fr is the peak frequency of the beat signal when the relative velocity with the moving target object 1 is zero, and fp is the movement. These are deviations in the frequency of the beat signal due to the Doppler effect when the object 1 is moving relative to the target object 1, and can be expressed as follows.

Fr = 4RfmΔf / c (3) where R is the relative distance from the antenna 2 to the moving target object 1, fm is the frequency modulation repetition frequency, Δf is the frequency shift width, and c is Represents the speed of light. fp = 2fo.V / c (4) where fo is the transmission center frequency and V is the moving target object 1
Represents the relative speed with.

FIG. 3 is a diagram showing the configuration of the signal processing means. The signal processing means 5 shown in this figure includes an LPF (56) for applying a shallow band limitation to the analog signal from the mixer 4 to prevent aliasing due to A / D conversion, and an A for converting the output of the LPF into a digital signal. / D converter 51 (Analog to Digita
I Converter) and beat signal frequency analysis means 52 using fast Fourier transform (FFT) for frequency analysis of the beat signal from the A / D converter 51.

Further, the signal processing means 5 includes a peak frequency identification weight forming means 53 for forming a weight for identifying a peak frequency. The peak frequency identification weight forming means 5
3 will be described. The peak frequency identification weight forming means 53 comprises a peak frequency predicting means 531 for predicting the current peak frequency from the past measured peak frequencies. FIG. 4 is a diagram showing the configuration of the weight forming means in FIG. 3, and FIG. 5 is a diagram showing a state in which there are a plurality of measured peak frequencies with respect to the peak frequency predicted value of the beat signal. First, the beat signal frequency analyzing means 52 measures the rising and falling peak frequencies fu and fd of the beat signal of the moving target object 1 at regular intervals, and the result is the peak frequency predicting means 53.
Stored in 1. Further, the peak frequency predicting means 5
In FIG. 5, based on the stored peak frequency, as shown in FIG.
The peak frequencies fu (n-4), fu (n-3), fu (n-2), and fu (n-1) of the beat signals of 4, n-3, n-2, and n-1 are currently n. Fu (n) is predicted.

The peak frequency identification weight forming means 53 comprises the following weight function evaluating means 532. In the weighting function evaluation means 532, as shown in FIG. 5, with respect to the predicted peak frequency fu (n) predicted by the peak frequency prediction means 531, fu1 (n) which is δf1 apart from fu (n) as the measurement frequency. , Fu2 (n) separated by δf2 exists, it is determined which is the measured value of the moving target object 1. The determination method will be described below.

The weighting function evaluation means 532 uses the weighting function F.
By providing (L, δf), the peak frequency with the larger weight is used as the true measurement beat signal. Here, L is the power level of the measured peak frequency. This weighting function F
Examples of (L, δf) are as follows.

[0017]

[Equation 1]

As shown in these equations, the smaller the difference between the measured peak frequency and the predicted peak frequency and the larger the parameter level, the more the true peak frequency is determined. FIG. 6 is a diagram for explaining a specific example of weight formation for peak frequency identification. As shown in this figure, the power levels for the measured values fu1 (n) and fu2 (n) are L1 and L
Set to 2. In the weighting function evaluation means 532, the weighting functions F1 (L1, δf1), F2 are calculated by the above equation (5).
(L2, .delta.f2) is calculated as follows.

[0019]

[Equation 2]

In this case, the weighting function is F1 (L1, δf1
) <F2 (L2, .delta.f2), it is determined that fu2 (n) is the true measured peak frequency. The other measurement peak frequency f
It is determined that u1 (n) is due to noise. The above is for the case where the measured peak frequency does not match the predicted peak frequency,
This is to determine which of a plurality of peak frequencies existing in the neighborhood is true, and when δf = 0, that is, the predicted peak frequency and the measured frequency match, the measured frequency is set to the true measured peak frequency. ..

Further, the signal processing means 5 uses the weighting function of the peak frequency identification weight forming means 53 as the true measurement peak frequency, of the plurality of peak frequencies of the beat signal frequency analyzing means 52, the measurement peak frequency having the largest weighting function. It comprises a beat signal determining means 54 for determining and a distance velocity deriving means 55 for deriving the relative distance and relative velocity with respect to the moving target object 1 from the peak frequency of the beat signal determined by the beat signal determining means 54.

The distance / velocity deriving means 55 calculates the relative distance R and the relative distance from the peak frequency of the beat signal determined by the beat signal determining means 54 using the above equations (1), (2), (3) and (4). The velocity V is derived as follows. R = (fd + fu) c / 8 (fm.Δf) (11) V = (fd-fu) c / 4fo (12)

[0023]

As described above, according to the present invention, the smaller the difference between the predicted peak frequency at the present time and the peak frequency of the beat signal measured at the present time is, the larger the measurement is. If the power level of the peak frequency of the beat signal is increased, a weight is formed that increases, and the one with the higher weight is determined as the true measured peak frequency, and the moving target is determined from the peak frequency of the beat signal thus determined. Since the relative distance and relative velocity of the target object are derived, even if the peak frequency of the noise signal frequently happens to be close to the predicted peak frequency, it can be removed, leading to the loss of the moving target object. And stable relative distance and relative speed can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a distance velocity measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between frequency of a continuous radar wave, a reflected wave from a moving target object, and a beat signal versus time.

FIG. 3 is a diagram showing a configuration of signal processing means.

FIG. 4 is a diagram showing a configuration of a weight forming unit of FIG.

FIG. 5 is a diagram showing a state in which there are a plurality of measured peak frequencies with respect to a peak frequency predicted value of a beat signal.

FIG. 6 is a diagram illustrating a specific example of weight formation for peak frequency identification.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Moving target object 2 ... Antenna 3 ... Continuous wave forming transmitter 4 ... Mixer 5 ... Signal processing means 6 ... Indicator 51 ... A / D converter 52 ... Beat signal frequency analysis means 53 ... Peak frequency identification weight formation means 54 ... Beat signal determining means 55 ... Distance velocity deriving means 531 ... Peak frequency predicting means 532 ... Weighting function evaluating means

Claims (1)

[Claims] 1. A radiated continuous radar wave is reflected by a moving target object (1), and the relative distance between the reflected target wave and the continuous radar wave and the frequency of a beat signal from the moving target object (1), A distance velocity measuring device for measuring relative velocity, comprising beat signal frequency analyzing means (52) for performing frequency analysis of the beat signal, and a peak of a past beat signal obtained by the beat signal frequency analyzing means (52). The smaller the difference between the peak frequency currently predicted from the frequency and the peak frequency of the beat signal measured at the present time, the greater the frequency difference, and the greater the power level of the peak frequency of the beat signal measured at the present time, the greater the difference. Peak frequency identification weight forming means (53) for forming weights, and peak frequency analyzed by the beat signal frequency analyzing means (52) Of the peak frequency identification weight forming means (5
Beat signal determining means (54) for determining a peak frequency having a greater weight according to 3), and the relative distance of the moving target object (1) from the peak frequency of the beat signal determined by the beat signal determining means (54). And a distance speed deriving means (55) for deriving a relative speed.