JPH02227688A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To utilize a relatively low-speed circuit as an analog or digital processing circuit for processing when a short distance is measured in a short time by adjusting the period of the sweep signal of a sweep oscillation circuit. CONSTITUTION:A transmitting sweep signal generated by sweeping a frequency continuously by a sweep oscillation circuit 13 is sent to a body 1 to be measured through a transmitter 3 and a transmitting antenna 9. The reflected sweep signal which is reflected by the body 1 to be reflected is received through a receiving antenna 10 and a receiver 6 and adjusted by an amplitude adjusting circuit 11 to the same amplitude with the transmitting wave. Then an adding circuit 12 adds the transmitting wave to generate and output a composite wave. The distance between the body 1 to be measured and the receiver 6 is detected from the composite wave output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring device suitable for use in measuring distances between vehicles, etc.

[Summary of the invention]

The present invention relates to a distance measuring device suitable for measuring the distance between cars, etc., and includes a sweep oscillation means that continuously sweeps a frequency to generate a sweep signal, and a transmission sweep signal from the sweep oscillation means that is transmitted to the measured object through the transmission means. A receiving means for receiving a reflected sweep signal transmitted toward the body and reflected by the object to be measured, and an adding means for adjusting and combining the amplitude of the reflected sweep signal received by the receiving means to be the same as that of the transmitted sweep signal. By detecting the distance between the object to be measured and the receiving means from the combined wave output from the adding means, a relatively low-speed analog or digital circuit can be used.

[Conventional technology]

Conventionally, various methods have been proposed for measuring distance using ultrasonic waves, radio waves, light, and the like. FIG. 6 shows a configuration diagram of a distance measuring device using an ultrasonic handset.

In Fig. 6, the transmitting pulse (4a) generated by the pulse generating circuit (4) is transmitted to the transmitter (3) in order to measure the distance d between the object to be measured (1) and the transducers (2) and (5). ) is emitted from the transmitter (2) toward the object to be measured (1). This ultrasonic transmission pulse propagates through a medium such as air or water, hits an object to be measured (1), is reflected, and is received by a delivery device (5).

Reflected pulse (6a) taken out via receiver (6)
is supplied to a counter (7) for measuring time. Since the counter (7) has already been supplied with the transmission pulse (4a) from the pulse generation circuit (4), for example, the delay time Δt from the rising point of the transmission pulse (4a) to the rising point of the reflected pulse (6a) is measured by a counter (7).

(8) is a clock generation circuit that generates a reference clock for measuring the delay time Δt, and a delay output corresponding to the delay time Δt is taken out from the counter (7).

If this delay time Δt is known, the distance d to be measured can be determined by the following equation (1).

Here, V is 340m8 for ultrasonic waves and 3X for light.
10”-8.

[Problems to be Solved by the Invention] The conventional distance measuring device as described above is widely used in radars and the like because it can measure distances to objects to be measured at a plurality of different distances using a high-speed counter. However, it has the following drawbacks.

(b) In order to ensure the rise and fall of the pulse waveform, a high-speed, high-output transmitting device is required.

(b) Since information in the amplitude direction of the transmitted pulse and the reflected pulse is used, the influence of noise is large, and the reception gain must be adjusted according to the return distance of the reflected pulse.

(c) Particularly when using radio waves or light, when measuring short distances of around 10 m, the measurement time is approximately several tens of ns, and jitter fluctuations of the circuit itself must be suppressed to less than ins.

Therefore, such a distance measuring device requires high-speed digital or analog processing, making the device expensive in order to increase accuracy.

The present invention was made in view of the above-mentioned drawbacks, and its purpose is to provide a relatively low-speed analog or digital processing circuit for measuring short distances, even when measuring short distances in a short time on the order of several tens of nanoseconds. The objective is to obtain a distance measuring device that can be used.

[Means to solve the problem]

One example of the distance measuring device of the present invention is shown in FIG. 1, which includes a sweep oscillation means (13) that continuously sweeps the frequency and generates a sweep signal; transmitting a transmission sweep signal from the transmitting means (3) and (9) toward the object to be measured (1),
Receiving means (6) (10) and mi-receiving means (6) (10) for receiving the reflected sweep signal reflected by the object to be measured (1).
addition means (12) for adjusting and combining the amplitude of the reflected sweep signal received by the transmitted sweep signal to be the same as that of the transmitted sweep signal;
The measured object (1) is calculated from the composite wave output from the adding means (12).
and the receiving means (to) (6).

[Effect]

The distance measuring device of the present invention makes the amplitude of the reflected sweep signal received by the receiving means the same as the transmitted sweep signal and adds the transmitted sweep signal transmitted toward the object to be measured, so that the transmitted sweep signal and the reflected sweep signal are combined. If the delay time Δt between the two satisfies 2n+1/2f (mouth=0.1.2...), the amplitude of the added composite wave becomes zero, and since the frequency f is varied by the sweep, the amplitude of the composite wave The change causes zero points at some of the frequencies f that satisfy the above equation, and at frequencies lower than 10 points from which Δt = 1/2fo, the oscillation distance d can be determined, so it is possible to calculate the A distance measuring device is obtained that can use relatively slow analog or digital circuits even when measuring distance at high speed.

〔Example〕

Hereinafter, one embodiment of the distance measuring device of the present invention will be described with reference to FIGS. 1 to 3.

In FIG. 1, a continuous sine wave is emitted to the object to be measured (1) instead of a pulse wave, and the reflected wave is received. In Figure 1, a sweep oscillation circuit (13) oscillates a sine wave (13a) of a predetermined frequency f, and transmits a sine wave to the object under test (1) via a transmitter (3) and a transmitting antenna (9). The reflected sine wave that was emitted and reflected by the object to be measured (1) is received by the receiving antenna (10), and the reflected sine wave is transmitted to the receiver (
The reflected sine wave (6a
) is adjusted to be the same as the amplitude of the transmitted sine wave (13a), and the sweep oscillation circuit (13a) is adjusted using the adder circuit (12).
) and a reflected sine wave (6a) are added together to create and output a composite wave.

The operation of the above configuration will be explained with reference to FIGS. 2 and 3. Second
Figure A shows the transmitting sine wave (13a) emitted from the transmitting antenna (9) to the object under test (1), and Figure 2B shows the amplitude of the sine wave received by the receiving antenna (10) and transmitted through the receiver (6). A reflected sine wave (6a) whose amplitude has been adjusted to be the same as that of the transmitted sine wave (13a) by an adjustment circuit (11) is shown.

When combining such a transmitted sine wave (13a) and a reflected sine wave (6a) in the adder circuit (12), the transmitted sine wave (13a)
) and the reflected sine wave (6a), the delay time Δm is as follows (2)
2, where n = (L il 2..., r is the sine wave frequency. The phase of the transmitted sine wave (13a) and the reflected sine wave (6a) is reversed, and the amplitude of the composite wave output becomes zero. Become.

Now, if the frequency of the transmitted sine wave (13a) is continuously swept from high to low by the sweep oscillation circuit 13), the amplitude change of the composite wave output obtained from the adder circuit (12) will be the third As shown in the figure, the frequency points f, , 3 f, where the amplitude becomes zero at some frequencies r that satisfy the condition of the second equation
, 5 f,, 7 fa, etc., resulting in a delay time Δt= (3) 2f.

At frequencies lower than the zero frequency point to such that In other words, if you know the longest wavelength at which wavelength interference occurs, you can move from the object to be measured (1) to the receiving antenna (10
) can be found.

Therefore, the delay time Δt is Δt = 1/2 fa = 2 d/v'' (4
),', d=v/4 fa (=λ./4)...
・(5) Here, V is the propagation velocity of the sine wave, λ. is the wavelength of the sweep frequency.

The distance d can be found from equation (5).

According to the distance measuring device having the configuration shown in FIG. 1, for example, considering that the measurement distance range is about 1 m to 100 m, the oscillation frequency of the sweep oscillation circuit (13) is set to 1? It is necessary to transmit and receive wideband sweep waves covering iHz to 500 MI (actually 300 MHz at 1 m, 3 MHz at 100 m).
Therefore, the size of the antenna used for these transmissions and receptions and the configuration of the directional 6 transmitter/receiver are specified, and regulations under the Radio Law are also considered. Furthermore, in order to make the amplitudes of the transmitted and received waveforms the same, it is necessary to automatically control them according to the strength of the received waves.

A distance measuring device for solving such problems will be explained with reference to FIGS. 4 and 5. Note that parts in FIG. 4 corresponding to those in FIG. 1 are given the same reference numerals, and redundant explanation will be omitted.

In the case of FIG. 4, the sweep wave itself is not transmitted and received as in FIG. 1, but is transmitted and received on a carrier wave. In the present invention, even when received on a carrier wave, the term is included in the transmission and reception of a sweep signal. In FIG. 4, the frequency of the sweep signal of the sweep oscillation circuit (13) is set to a predetermined frequency. If the distance measurement of lm-10On+ is to be performed as described above, a sweep oscillation circuit (13) capable of sweeping in the range of IMHz to 500MHz is selected. A phase modulation circuit (17) that supplies this sweep signal f to a phase modulation circuit (17)
may be, for example, a frequency modulation circuit. Phase modulation circuit (1
For example, a carrier wave fc of about 1 to 2 GHz is supplied to 1.7). #I transmission wave fc is phase modulated by sweep signal f.

In this case, if the modulation index of phase or frequency modulation is set small, the occupied bandwidth of the output of the phase modulation circuit (17) can be made smaller than the occupied bandwidth of the sweep signal f. In addition, the frequency of the carrier wave fc is set to the optimal frequency according to the Radio Law, for example, several GH when the transmitting/receiving antennas (9), (10) and transmitting/receiving devices (3) and (6)
z~several 10G) 4z.

In this way, the carrier wave fc is phase-modulated using the sweep signal, and the phase-modulated signal fc±ω is emitted to the object to be measured (1) via the transmitter (3) and the transmitting antenna (9), and the reflected wave is received. It is fed to a limiter (14) via an antenna (10) and a receiver (6). This limiter (14) is provided to absorb fluctuations in received wave intensity.
) to maintain a constant amplitude. What is limited by the limiter (14) is a phase modulated wave, so amplitude fluctuations can be ignored as long as the wave does not fall below a certain value. It also has little effect on S/N and interference. The reflected phase modulated wave fc±ω limited by the limiter (14) is demodulated into the original sweep signal r' by the demodulation circuit (15). This demodulation circuit (15)
Of course, the demodulated sweep signal f' stores a delay time Δt that depends on the distance d to be measured, so the sweep signal f from the sweep oscillation circuit (13) and the demodulated sweep signal f' are added. A circuit (12) performs addition to obtain a composite wave output signal. Such a composite wave output signal is the third wave output signal.
Since the waveform is similar to that shown in the figure, the detection circuit (16
), the frequency f of zero amplitude included in these composite waves is
o, 3 f O+ 5 f o, 7 f o...
It is sufficient to detect the lowest frequency 10 from the point . The detection circuit (16) receives f0~ from the sweep oscillation circuit (13).
Sweep information up to nfo or only the frequency currently being swept is given. A flowchart for detecting this detection circuit (16) using a microprocessor or the like will be explained with reference to FIG. In the first step ST, the detection circuit (16) of this example sets the frequency f which becomes zero from the composite wave output signal.

=f,, rz=3ro, f3=3f,... is taken in, and in the second step ST, the frequency f,, f! , fs・
... are arranged in descending order of frequency. Next third step S
In T, the frequencies r, arranged in the second step ST, are
Let the final number n of r,...fn be 1, take f,
Proceed to the fourth step ST. In the fourth step S"T4, the value of fl is an odd number multiple (2n+
1), and if "NO", the process returns to the first step ST.

“YES” when the condition of fn=(2n+1)to is satisfied
”, then the fifth step ST, then the frequency fl+f!・
... Check whether all n items arranged in the order of fn have been completed, that is, up to n=n+1, and judge whether it is finished at the 6th step ST. If "NO", proceed to the 4th step. S
It is only necessary to return to T and look at all the signals up to n+1, and use the output signal that is in the "YES" state as the detection output signal.

Such a detection circuit (16) only needs to satisfy a speed that can follow the repetition period (several lIs to several hundred ns) of the sweep wave.

The distance measuring device of the present invention is useful for measuring distances between cars, preventing collisions between unmanned cars and people in factories, security systems such as detecting thieves, and relatively short distance measurements such as measuring cable lengths.

Note that the present invention is not limited to the embodiments described above, and various changes can be made without departing from the gist of the present invention.

〔Effect of the invention〕

According to the distance measuring device of the present invention, by adjusting the cycle of the sweep signal of the sweep oscillation circuit, detection of a delay time of several ns can be configured with an analog or digital circuit that handles a signal of about several hundred 111 seconds, and the distance Measuring equipment can be obtained at low cost.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the distance measuring device of the present invention, Fig. 2 is a waveform diagram showing the delay state between transmitted and received waves, Fig. 3 is a waveform diagram when sweeping waves are synthesized, and Fig. 4 is the main FIG. 5 is a block diagram showing another embodiment of the distance measuring device of the present invention, FIG. 5 is a flowchart of the detection circuit of the present invention, and FIG. 6 is a block diagram of a conventional distance measuring device. (1) is the object to be measured, (3) is the transmitter, (6) is the receiver,
(13) is a sweep oscillation circuit, (14) is a limiter, (
15) is a demodulation circuit, and (16) is a detection circuit.

Claims (1)

[Claims] Sweep oscillation means for generating a sweep signal by continuously sweeping a frequency; and Sweep oscillation means for generating a sweep signal by continuously sweeping a frequency; a receiving means for receiving the reflected sweep signal reflected by the receiving means; and an adding means for adjusting and combining the amplitude of the reflected sweep signal received by the receiving means to be the same as that of the transmitted sweep signal, and combining from the adding means. A distance measuring device that detects the distance between an object to be measured and a receiving means from wave output.