JP2000275334A - Speed measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate the speed of a radio wave emitting source by calculating the relative Doppler frequency incident to rotation of the radio wave emitting source and an antenna from the measurements taken by a frequency measuring means and receiving a radio wave from an unknown target approaching to a measuring point or receding therefrom. SOLUTION: An antenna 1 comprises a turntable 10 turning in the horizontal direction, a motor 11 for turning the turntable 10, and an antenna element 9 fixed eccentrically from the rotational central axis 12 of the turntable 10 wherein a signal received by the antenna element 9 is outputted to a receiver 2. A Doppler frequency detector 3 detects a maximum frequency 7 and a minimum frequency 8 from a measured frequency data 6. A speed calculator 4 calculates the speed of a radio wave emitting source based on the a maximum frequency 7 and the a minimum frequency 8. Since it is not required to determine the Doppler frequency from the frequency difference between a transmitting signal and a receiving signal, frequency of the transmission signal from the radio wave emitting source is not required to be known.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed measuring system, and more particularly, to a speed measuring system for receiving a radio wave from a radio wave emitting source approaching or leaving a measuring point and measuring a moving speed of the radio wave emitting source. .

[0002]

2. Description of the Related Art An example of a conventional speed measuring system is described in Japanese Patent Application Laid-Open No. 58-186810. As shown in FIG. 6, in this conventional speed measurement system, a received signal 22 received by an antenna 16 is amplified and demodulated by a receiver 17. Reception data 2 of demodulated signal
3 is compared with the identification data 25 from the data storage unit 19 in the identification unit 18, and only a desired signal is selected.

The reception frequency data 24 of the selected signal
Is output to the Doppler shift detection unit 20, and the Doppler shift detection unit 20 calculates Doppler shift data 27 from the difference between the storage frequency data 26 output from the data storage unit 19 and the reception frequency data 24. The speed component detection unit 21 calculates a speed component from the Doppler shift data 27.

[0004]

However, the conventional system described above has the following problems. The first problem is that only the speed of the measuring point can be determined. The reason is that the Doppler frequency due to the movement of the measurement point is detected. The second issue is
That is, the transmission frequency must be known. The reason is to detect the Doppler frequency from the difference between the transmission frequency and the reception frequency.

The present invention has been made under such a background, and provides a speed measuring system which receives a radio wave from an unknown target approaching or moving away from a measuring point and calculates the speed of a radio wave emitting source. The purpose is to:

[0006]

According to a first aspect of the present invention, a moving speed of a radio wave emitting source is measured by receiving a radio wave from a radio wave emitting source approaching or leaving a measuring point. A speed measurement system, which is placed at the measurement point and receives an electric wave from the radio wave emission source, an antenna rotating means for rotating the antenna disposed eccentrically from a rotation axis, and reception by the antenna. Frequency measuring means for measuring the frequency of the radio wave, calculating the relative Doppler frequency due to the rotation of the antenna and the antenna from the measurement result by the frequency measuring means, measuring the moving speed of the radio wave emitting source A speed measurement system is provided.

According to a second aspect of the present invention, a moving speed detecting means for detecting a moving speed of the measuring point, and a moving speed of the measuring point is subtracted from a relative speed between the radio wave emitting source and the measuring point. The speed measurement system according to claim 1, further comprising a subtraction unit, wherein the movement speed of the radio wave emission source is measured.

[0008] In the speed measuring system according to the present invention, the receiving device measures the speed of the radio wave emitting source by intentionally changing the relative speed with respect to the radio wave emitting source and measuring the frequency of the received signal. More specifically, an antenna that receives a radio wave from a radio wave emission source at a variable relative speed,
It comprises a receiver for detecting the frequency of the received signal, a Doppler frequency detector for detecting the maximum value and the minimum value from the measured frequency data, and a speed calculator for calculating the speed from the maximum value and the minimum value. .

In the present invention, the relative speed is intentionally changed by rotating the antenna installed eccentrically from the rotation center axis, and the received signal contains a Doppler component. Thus, the speed and transmission frequency of the radio wave emission source can be calculated from the maximum value and the minimum value of the frequency including the Doppler component, so that the transmission frequency does not need to be known.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a speed measurement system according to an embodiment of the present invention. In this figure, a speed measuring system includes an antenna 1 for receiving a radio wave from a radio wave emitting source, a receiver 2 for measuring the frequency of a received signal 5 received by the antenna 1, and a frequency maximum based on the measured frequency data 6. It has a Doppler frequency detector 3 for detecting the value 7 and the frequency minimum value 8, and a speed calculator 4 for calculating the speed of the radio wave emission source from the frequency maximum value 7 and the frequency minimum value 8.

Next, the detailed configuration of the antenna 1 will be described. FIG. 2 is a schematic diagram of the antenna 1 in the present embodiment. The antenna 1 is a turntable 10 that rotates in the horizontal direction, and a motor 1 that rotates the turntable 10.
1 and an antenna element 9 mounted eccentrically from the rotation center axis 12 of the turntable 10, and a signal received by the antenna element 9 is output to the receiver 2.

Next, the operation of this embodiment and the mechanism of speed measurement will be described in detail with reference to the drawings. FIG.
Referring to FIG. 5, the unknown radio wave emission source is located at the point A and is approaching the velocity measurement system located at the point B at the speed VA. The antenna element 9 has a speed V on the circumference of the radius r around the point B on the turntable 10.
It is assumed that it is rotating at B. The angle φ in the figure is
Assuming that the radius r is sufficiently smaller than the distance between the points A and B, it can be regarded that φ ≒ 0. X of antenna element 9
Assuming that the rotation angle with respect to the axis is θ, the relative speed in the X-axis direction is VB · SINθ−VA.

Therefore, the frequency data 6 received by the antenna element 9 and measured by the receiver 2 can be expressed by the following equation. f = f0 + 2 (VB · SIN θ−VA) / C · f0 (1) where C is the speed of light and f0 is the transmission frequency of the radio wave emission source. The frequency output from the receiver 2 and input to the Doppler frequency detector 3 changes as shown in FIG. The horizontal axis is the rotation angle of the antenna element 9, and the vertical axis is the measurement frequency.

The Doppler frequency detector 3 detects a maximum frequency value (θ = 90 °) fmax and a minimum frequency value (θ = 270 °) fmin among the measured frequencies. Where fma
The following relational expression is obtained using x and fmin. fmax = f0 + 2 (VB−VA) / C · f0 (2) fmin = f0 + 2 (−VB−VA) / C · f0 (3)

The speed calculator 4 calculates the speed VA of the radio wave emitting source from fmax and fmin output from the Doppler frequency detector 3. When VA is obtained from the equations (2) and (3), VA = {fmax (C-2VB) -fmin (C + 2VB)} / {2 (fmax-fmin)} (4)

The transmission frequency f0 of the radio wave emission source can be expressed by the following equation. f0 = (fmax−fmin) / 4VB · C (5) In the present embodiment, the case where the radio wave emission source approaches the measurement point is shown, but the same applies to the case where the radio wave emission source moves away from the measurement point.

Next, another embodiment of the present invention will be described in detail with reference to the drawings. Although the distance measurement system in the first embodiment is fixed, it is assumed in other embodiments that the distance measurement system is mounted on a moving body. Referring to FIG. 5, another embodiment of the present invention is the first embodiment shown in FIG.
In contrast to the configuration of the embodiment, the measurement point speed detector 1
4 is added, and the speed calculator 13 is used instead of the speed calculator 4.

The operation from reception of a radio wave from a radio wave emission source by the antenna 1, measurement of the frequency by the receiver 2, and detection of the maximum frequency 7 and the minimum value 8 by the Doppler frequency detector 3 are as described above. This is the same as the embodiment. The measuring point speed detector 14 detects a speed component of the measuring point in the X-axis direction, and outputs measuring point speed data 15 to the speed calculator 13. The speed calculator 13 calculates the speed of the radio wave emission source from the frequency maximum value 7 and the minimum value 8 and the measurement point speed data 15 in the X-axis direction.

Assuming that the velocity of the measurement point in the X-axis direction is V0, the equations (1) to (5) of the above-described embodiment are as follows. f = f0 + 2 (VB · SIN θ−V0−VA) / C · f0 (6) fmax = f0 + 2 (VB−V0−VA) / C · f0 (7) fmin = f0 + 2 (−VB−V0) −VA) / C · f0 (8) VA = [fmax {C-2 (VB + V0)} − fmin {C + 2 (VB + V0)}] / {2 (fmax−fmin)} (9) f0 = (Fmax-fmin) / 4VB · C (10)

The operation of one embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the scope of the present invention. The present invention is also included in the present invention.

[0021]

As described above, the present invention has the following effects. The first effect is that the speed of the radio wave emission source can be measured. The reason is that Doppler frequency can be measured only by receiving radio waves.

The second effect is that the frequency of the transmission signal of the radio wave emitting source does not need to be known. The reason is that it is not necessary to obtain the Doppler frequency from the frequency difference between the transmission signal and the reception signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a speed measurement system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of the antenna 1 of FIG. 1;

FIG. 3 is a geometrical layout diagram for explaining the operation of the embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a rotation angle and a frequency of the antenna 1 in FIG. 1;

FIG. 5 is a block diagram showing a configuration of a speed measurement system according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a speed measurement system according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Receiver 3 Doppler frequency detector 4 Speed calculator 5 Received signal 6 Frequency data 7 Maximum frequency 8 Minimum frequency 9 Antenna element 10 Turntable 11 Motor 12 Rotation center axis 13 Speed calculator 14 Measurement point speed detector 15 Measurement point velocity data 16 Antenna 17 Receiver 18 Identification section 19 Data storage section 20 Doppler shift detection section 21 Speed component detection section 22 Reception signal 23 Reception specification data 24 Reception frequency data 25 Identification data 26 Storage frequency data 27 Doppler shift data

Claims (2)

[Claims] 1. A speed measuring system for receiving a radio wave from a radio wave emission source approaching or leaving a measurement point and measuring a moving speed of the radio wave emission source, wherein the speed measurement system is located at the measurement point. An antenna that receives a radio wave from the radio wave emission source, an antenna rotating unit that rotates the antenna disposed eccentrically from a rotation axis, and a frequency measurement unit that measures the frequency of the radio wave received by the antenna. And calculating a relative Doppler frequency due to the rotation of the antenna and the antenna from the measurement result by the frequency measurement means,
A speed measuring system for measuring a moving speed of the radio wave emitting source. 2. A moving speed detecting means for detecting a moving speed of the measuring point, and a subtracting means for subtracting a moving speed of the measuring point from a relative speed between the radio wave emitting source and the measuring point, 2. The speed measuring system according to claim 1, wherein the moving speed of the radio wave emitting source is measured.