JPH10123238A - Distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the distance measuring device for both short distances and long distances, which definitely performs the judgement as to which of the measured results of the distance measurement of a FM-CW method of a pulse method has the acuurate value. SOLUTION: The reflected wave of the transmitted wave from an airframe from the ground surface is received by a receiving part 5 and outputted to a frequency mixing part 3 as the reflected wave IW1. The frequency mixing part 3 obtains a beat signal BT based on the frequency difference between the reflected signal IW1 and a transmitted signal OW1 transmitted from a transmitting part 1 and outputs the signal to a beat-signal detecting part 7. Then, the beat-signal detecting part 7 performs the detection of the beat signal and outputs the detected signal to a controller 8. Then, the controller 8 selects the method for the distance measurement by the FM-CW method having the short measuring range when the beat signal is detected. Furthermore, the controller 8 selects the method for the distance measurement by the pulse method having the long frequency range when the beat is not detected by the beat-signal detecting part 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a distance measuring device for measuring a distance between a flying object and an object to be measured.

[0002]

2. Description of the Related Art A first conventional distance measuring device will be described with reference to FIG. FIG. 4 shows an FM-CW (Frequ
ency Modulation-Continuou
FIG. 3 is a block diagram illustrating a configuration of a distance measuring device of a swave) system. This distance measuring device is mounted on a flying object and used as an altimeter. In this figure, reference numeral 10 denotes a transmission unit, which transmits a transmission wave frequency-modulated by a triangular wave or a sawtooth wave from the antenna 11.

[0003] A receiving unit 12 receives a reflected wave, which is a return of the transmission wave transmitted from the antenna 11 from the device under test, from the antenna 13 and transmits the reflected wave to the frequency mixing unit 14 as a reflected signal. The frequency mixing unit 13 includes the receiving unit 1
It outputs a beat signal obtained from the difference between the frequency of the reflected signal from the transmitter 2 and the frequency of the same transmission signal as the transmission wave from the transmitter 10.

[0004] The operation of the above distance measuring device will be described with reference to FIGS. 4 and 5. FIG. 5 is a timing chart of signals used in the first conventional example. First, the transmission unit 10 transmits the transmission wave OW2 having the frequency characteristic modulated by the sawtooth wave shown in FIG.
Send from. The transmitted transmission wave OW2 is reflected on the ground surface and returns as a reflected wave. This reflected wave is shown in FIG.
(B) has a sawtooth-shaped frequency characteristic shown in FIG.
The frequency of the reflected wave is shifted from the frequency of the transmitted wave by the time from time t11 to time t12, which is the round trip time to the ground.

[0005] The frequency mixing section 14 includes a transmitting section 10.
From the frequency difference between time t12 and time t13 between the transmission signal OW2 from and the reflected signal from the reception unit 12,
A beat signal having a constant frequency characteristic shown in FIG. 5C is generated and output. The frequency analysis of the generated beat signal is performed, and the distance between the flying object and the measured object is calculated.

Next, a second conventional distance measuring device will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of a pulse type distance measuring device. This distance measuring device is mounted on a flying object and used as an altimeter. In the figure, 2
Reference numeral 0 denotes a transmitting unit that periodically transmits a square wave transmission pulse from the antenna 21 as a transmission wave. 22
Is a receiving unit, and transmits a reflected pulse, which is a reflected wave from the ground surface, of the transmission pulse transmitted from the antenna 21 to the antenna 2
3 is received. Reference numeral 24 denotes a pulse counting unit which internally has a pulse generation circuit of a reference frequency and a counter circuit, and performs time measurement by multiplying the count value of the counter circuit by the period of the pulse of the pulse generator. is there.

Next, the operation of the above distance measuring device will be described with reference to FIGS. FIG. 7 is a timing chart of signals used in the second conventional example. First, the transmitting unit 20 outputs a transmission pulse from the antenna 21. At the same time, the transmission unit 20 transmits the transmission pulse signal TW2 to the pulse counting unit 24. The pulse counting unit 24 is configured as shown in FIG.
At time t15 of the rising of the transmission pulse signal TW2 shown in FIG.

[0008] A reflected pulse, which is a reflected wave of the transmitted pulse from the ground, is received by the receiver 22. The receiving unit 22 converts the received reflected pulse into a reflected pulse signal RW2.
To the pulse counting unit 24. Next, the pulse counting unit 24 outputs the reflected pulse signal RW shown in FIG.
The measurement of time is stopped at the timing of time t16 when 2 is received. Here, since the time required for the transmitted transmission pulse to reciprocate is known, the distance between the ground surface and the flying object is calculated by multiplying "half the time required for reciprocation" by "speed of light".

Here, the FM-CW type distance measuring device of the first embodiment is generally used for measuring a short distance. Since the transmission wave is frequency-modulated with a triangular wave or a sawtooth wave, an error occurs if the stability of the center frequency of the triangular wave or the sawtooth wave and the transmission wave is not good. In particular, when measuring a long distance, the cycle of the triangular wave or sawtooth wave used for frequency modulation tends to be long, and the error due to the accuracy of the center frequency of the transmission wave tends to increase.

The pulse type distance measuring device of the second embodiment is generally used for measuring a long distance. this is,
The time from when the pulse is transmitted to when it returns is measured. In the case of a short distance, the measurement time is very short. Therefore, the frequency of the pulse generation circuit used for time measurement needs to be a very high frequency in order to increase measurement accuracy.

[0011] Further, for high frequency counting and distance calculation, it is necessary to improve the signal processing speed. For example, when distance measurement is performed in units of '1 m', the frequency of the pulse generation circuit used for time measurement needs a value of 'several hundred MHz'. Therefore, if both the FM-CW method and the pulse method are used to compensate for the disadvantages, and the distance between the flying object and the measured object is measured, an accurate altitude measurement value can be obtained.

[0012]

However, due to the performance of the distance measuring device, it is not clear which of the above-mentioned distance measuring devices is to be used, the boundary of the measurement limit between the short distance and the long distance. In other words, when the distance between the flying object and the object to be measured is measured by both the FM-CW method and the pulse method, it is not possible to clearly determine which measurement result to select as an accurate value. there were. The present invention has been made under such a background, and determines whether the measurement result of the FM-CW method or the pulse method is a more accurate value, and provides a short distance and a short distance that can accurately measure the distance. An object of the present invention is to provide a distance measuring device that can be used for a long distance.

[0013]

According to the first aspect of the present invention,
Mounted on a flying object, the distance between the flying object and the object to be measured,
In a distance measuring device that measures using radio waves, a transmitting unit that radiates a transmission wave to the device under test, a receiving unit that receives a reflected wave of the transmission wave reflected by the device under test, Detecting means for detecting a beat signal obtained from a frequency difference between the reflected wave received by the means and the transmission signal; and a first operation for calculating a distance between the flying object and the device under test based on the beat signal Means, a measuring means for measuring a time from transmitting the transmission wave to receiving the reception wave, and a second means for calculating a distance between the flying object and the measured object based on the data of the time. Arithmetic means;
And a selecting means for selectively selecting the distance of the result of the calculation by the first calculating means and the distance of the result of the second calculating means depending on the presence or absence of the beat signal.

According to a second aspect of the present invention, in the range finder of the first aspect, the transmitting means simultaneously transmits a frequency-modulated transmission wave and a square-wave-shaped pulse. According to a third aspect of the present invention, in the distance measuring device according to the first or second aspect, the measuring means includes:
The number of periodic pulses is counted, and time data is calculated based on the counted data. Claim 4
The invention described in any one of claims 1 to 3 is characterized in that the transmission means transmits a transmission wave at each distance measurement timing.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a distance measuring device according to an embodiment of the present invention. In this figure, reference numeral 1 denotes a transmission unit, which transmits a transmission wave and a square-wave transmission pulse frequency-modulated by a sawtooth wave from an antenna 2 and transmits the frequency-modulated transmission wave to a frequency mixing unit 3 as a transmission signal OW1. The transmission is performed, and a square-wave transmission pulse is transmitted to the pulse coefficient unit 4 as a transmission pulse signal.

The frequency mixing section 3 outputs a beat signal BT obtained from the difference between the frequency of the reflected signal IW1 from the receiving section 5 and the frequency of the same transmission signal OW1 as the transmission wave from the transmitting section 1. . The pulse counting unit 4 has a pulse generation circuit of a reference frequency and a counter circuit therein,
The time measurement is performed by multiplying the count value of the counter circuit by the pulse period of the pulse generator.

The receiver 5 receives the frequency-modulated transmission wave and the reflected wave of the square-wave transmission pulse from the device under test using the antenna 6, and converts the reflected wave of the frequency-modulated transmission wave at the device under test. The reflected wave signal IW1 is transmitted to the frequency mixing unit 3, and the reflected pulse of the square wave transmission pulse from the device under test is transmitted to the pulse counting unit 4 as the reflected pulse signal TR1.

Reference numeral 7 denotes a beat signal detection unit, which detects that the frequency mixing unit 3 is outputting a beat signal during distance measurement, and outputs a detection signal to the controller 8. The controller 8 determines whether to perform the distance measurement using the measurement result of the FM-CW method or the pulse method based on the presence or absence of the detection signal of the beat signal detection unit 7, and then determines the measurement distance. The calculation is performed, and data of the measured distance, which is the calculation result, is output.

Next, the operation of the above embodiment will be described with reference to FIGS. 1 and 2 and the flowchart shown in FIG. FIG. 2 is a timing chart showing waveforms at various parts in the operation of the radio altimeter according to the embodiment of FIG. First, in step S1, the transmitting unit 1
Performs frequency modulation using the sawtooth wave, and transmits the frequency-modulated transmission wave having the frequency characteristic shown in FIG. 2A from the antenna 2 at time t1. At the same time, in step S2, the transmission unit 1 transmits the square-wave transmission pulse shown in FIG. 2E at time t1, and the pulse counting unit 4 performs the time counting operation from time t1 when the transmission pulse signal TW1 is input. To start.

Next, in step S3, FIG.
As shown in the figure, the frequency-modulated transmission wave is transmitted at time t
The transmission pulse is transmitted by the transmission unit 1 during the period from 1 to t3, and the transmission pulse rises at time t1 and is transmitted by the transmission unit 1 for a predetermined time width, and the transmission is stopped. Then, the frequency-modulated transmission wave is reflected on the surface of the ground, and FIG.
Returns to the flying object at time t as a reflected wave having the frequency characteristic shown in FIG. Further, the transmission pulse in the form of a square wave is reflected on the surface of the earth, and returns to the flying object at time t2 as a reflection pulse shown in FIG. At this time, the pulse counting unit 4 stops the time counting operation at time t2 when the reflected pulse signal TR1 is input.

Here, the reflected wave having the frequency characteristic shown in FIG. 2A is received by the receiver 5 and transmitted to the frequency mixer 3 as a reflected signal IW1. Next, during the period from time t2 to time t3, the frequency mixing unit 3 has the frequency characteristic shown in FIG. 2C from the frequency difference between the reflected signal IW1 and the transmission signal OW1 transmitted from the transmission unit 1. The beat signal BT is obtained and transmitted to the beat signal detecting section 7. Next, the beat signal detection unit 7 detects a beat signal and transmits a detection signal shown in FIG.

Next, in step S4, the controller 8 responds to a detection signal indicating that the beat signal BT has been detected.
It is determined that the distance measurement is performed by the FM-CW method having a short measurement range. Next, in step S5, the controller 8 inputs the beat signal BT, and based on the frequency analysis,
The distance data between the flying object and the ground surface is calculated. Then, in step S6, the controller 8 outputs distance data between the flying object and the ground as a result of the calculation.

Next, at step S1, at time t4
Then, the transmitting unit 1 transmits a transmission wave having the frequency characteristic shown in FIG. 2A, and at the same time, in step S2, the transmitting unit 1 transmits a transmission pulse shown in FIG. Send. At this time, the pulse counting unit 4 starts the time counting operation from time t4 shown in FIG. 2C when the transmission signal TW1 is input from the transmission unit 1. Next, step S
In 3, the transmission unit 1 stops transmitting the transmission wave and the transmission pulse. Then, at time t5, FIG.
The reflected wave having the frequency characteristic shown in FIG. 2 and the reflected pulse shown in FIG.

Next, the receiving section 5 transmits the input reflected wave to the frequency mixing section 3 as a reflected signal IW1. However, the transmission signal OW1 and the reflection signal IW1 are different from those shown in FIG.
By comparing the frequency characteristic of the transmitted wave with the frequency characteristic of the reflected wave shown in FIG. 2 (b), no overlapping portion is seen as can be seen. Therefore, the frequency mixer 3 cannot determine the beat signal BT based on the difference between the two frequencies. As a result, the beat detection unit 7 detects the time t4 shown in FIG.
The detection signal for the beat signal is not transmitted to the controller 8 within the range of t6.

Next, in step 4, the controller 8 determines the presence or absence of the beat signal BT. However, since the detection signal is not transmitted from the beat signal detection unit 7, it is determined that the beat signal is not detected, and the distance measurement is measured. Choose to use a pulse method with a long range. Next, in step S7, the controller 8 inputs the counted time data from the pulse counting unit 4 and multiplies half the value of the time data by the “light speed” to obtain the distance between the flying object and the ground. Performs data operations. Then, in step S8, the controller 8 outputs the distance data between the flying object and the ground surface as the calculation result.

As described above, an embodiment of the present invention has been described as an altimeter for measuring a distance between a flying object and the ground surface.
One embodiment of the present invention can be applied to the measurement of a distance over a wide measurement range between a distance measuring device and an object to be measured.

[0027]

According to the first aspect of the present invention, in a distance measuring device mounted on a flying object and measuring the distance between the flying object and the object to be measured using a radio wave, the transmission wave is measured by the measuring object. Transmitting means for radiating the object, receiving means for receiving the reflected wave of the transmitted wave reflected by the measured object,
Detecting means for detecting a beat signal obtained from a frequency difference between the reflected wave and the transmission signal received by the receiving means; and a first means for calculating a distance between the flying object and the device under test based on the beat signal. Calculating means, measuring means for measuring a time from transmitting the transmission wave to receiving the reception wave, and calculating a distance between the flying object and the object to be measured based on the data of the time. The second arithmetic means, and the presence or absence of the beat signal, the selection means for selectively selecting the distance of the calculation result of the first calculation means and the distance of the result of the second calculation means, Since the distance measuring device of the FM-CW method and the pulse method is combined and which method is selected based on the presence or absence of the beat signal, both the measurement when the measurement distance is short and the measurement when the measurement distance is long can be performed with high accuracy. effective.

According to the second aspect of the present invention, in the distance measuring device according to the first aspect, the transmitting means transmits a frequency-modulated transmission wave and a square-wave-shaped pulse simultaneously, so that the distance measurement is performed. In the above, even when either the FM-CW method or the pulse method is selected, since the measurement starts at the same time, accurate measurement can be performed. According to a third aspect of the present invention, in the distance measuring device according to the first or second aspect, the measuring means counts the number of periodic pulses and calculates time data based on the counted data. Therefore, there is a term that enables time data to be accurately measured. According to a fourth aspect of the present invention, in the distance measuring device according to any one of the first to third aspects, the transmitting means transmits a transmission wave at each timing of distance measurement. Rather, it is transmitted intermittently, which has the effect of reducing the power consumption of the distance measuring device.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing an operation of the distance measuring device according to one embodiment of the present invention.

FIG. 3 is a flowchart illustrating an operation of the distance measuring device according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a first conventional distance measuring device.

FIG. 5 is a timing chart showing the operation of the first conventional distance measuring device.

FIG. 6 is a block diagram showing a configuration of a second conventional distance measuring device.

FIG. 7 is a timing chart showing the operation of the distance measuring device of the second conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmitting unit 2 antenna 3 frequency mixing unit 4 pulse counting unit 5 receiving unit 6 antenna 7 beat signal detecting unit 8 controller 10 transmitting unit 11 antenna 12 receiving unit 13 antenna 14 frequency mixing unit 20 transmitting unit 21 antenna 22 receiving unit 23 antenna 24 Pulse counting section

Claims (4)

[Claims] 1. A distance measuring device mounted on a flying object and measuring a distance between the flying object and an object to be measured using a radio wave, transmitting means for transmitting a transmission wave to the object to be measured. Receiving means for receiving the reflected wave of the transmitted wave reflected by the device under test; detecting means for detecting a beat signal obtained from a frequency difference between the reflected wave received by the receiving means and the transmission signal; A first calculating means for calculating a distance between the flying object and the measured object based on the beat signal; anda measuring means for measuring a time from transmitting the transmission wave to receiving the reception wave. A second calculating means for calculating a distance between the flying object and the object to be measured based on the time data; a distance calculated by the first calculating means based on the presence or absence of the beat signal; Alternative to the result distance of the means Distance measuring instrument, characterized by comprising selecting means for selecting, a. 2. The distance measuring instrument according to claim 1, wherein said transmitting means simultaneously transmits a frequency-modulated transmission wave and a square-wave-shaped pulse. 3. The distance measuring instrument according to claim 1, wherein said measuring means counts the number of periodic pulses and calculates time data based on the counted data. 4. The distance measuring device according to claim 1, wherein said transmitting means transmits a transmission wave at each timing of distance measurement.