JP2001056370A - Real time phase difference range-finding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a measurement error based on the strength change of a reception signal and to reduce distance measurement time by obtaining distance from the ratio of the DC component of the multiplication signal of transmission and reception signals to that of the multiplication signal of a signal where the transmission signal has been subjected to specific phase shift and the reception signal. SOLUTION: The oscillation (transmission) signals of both oscillators 10 and 15 are multiplied by a mixer 14 and are inputted to a multiplier 3 and a phase shifter 2. Also, the multiplication signal of a receiver 19 is multiplied by the oscillation signal of the oscillator 15 by a mixer 20, which is inputted to the multipliers 3 and 4 via an LPF 21. The multiplier 3 multiplies an input (transmission) signal from an LPF 17 by a signal (the multiplication value of the reception signal of the receiver 19 and the oscillation signal of the oscillator 15) from the LPF 21 before inputting to an LPF 5. On the other hand, a multiplier 4 multiplies a (transmission) signal obtained by phase-shifting by a specific amount using the phase shifter 2 by a signal from the LPF 21 before outputting to an LPF 6. A divider 7 obtains the ratio of the DC components of the signal where the passage of the AC components is rejected by the LPFs 5 and 6. Distance is calculated based on the ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase difference ranging system using a carrier wave modulated by a transmission signal, and more particularly to a high-speed ranging system in which the time required for distance measurement is short.

[0002]

2. Description of the Related Art A distance measuring method using a longitudinal wave or a transverse wave is roughly classified into a pulse method and a phase difference method. In general, the pulse method refers to a distance measurement method in which a pulse wave is transmitted to a target, a pulse wave reflected by the target is received, and a round trip time from transmission to reception of the pulse wave is measured. On the other hand, the phase difference method is to transmit a carrier modulated by a transmission signal to a target, receive a carrier reflected by the target, and determine the phase difference between the modulated signal at the time of transmission and that at the time of reception due to the distance to the target. This is a distance measurement method that utilizes

FIG. 2 is a block diagram for measuring a distance by a conventional phase difference ranging method. A phase detector 30 as a phase detector for transmitting and receiving waves includes a zero-crossing detector 31,
32. The phase detection means obtains a phase difference between the transmission signal and the reception signal by measuring a time difference between the transmission signal and the reception signal at a zero crossing point (zero cross point).

However, in an actual circuit, the zero-crossing point is not strictly 0 [V], but rather several [mV] to several tens.
It operates at a threshold of about [mV]. For this reason, even if the actual distance to the target is constant, the time difference between the transmission signal and the reception signal varies due to the change in the intensity of the reception signal. As an example, as shown in FIG. 4, the intensity of the received signal _{S 2} from 4.0 4.2,4.5,5.0,5.3
, The time difference between the transmission signal and the reception signal becomes longer. For example, if the time difference is set to be output as 100 [μsec] 4 [m] measurements when, when the intensity S ₂ of the received signal has to be S2 = 4.2, the actual distance 4 [m] Can output accurate measurement values.
However, when S ₂ = 5.3, the time difference is 100 μs
If [ec] is output, the measurement distance is output as 4 [m], but as can be seen with reference to FIG. 4, the actual distance is 3 [m], and the measurement has an error of 1 [m]. I will. Also, S ₂ =
If the time difference is output as 100 [μsec] at 4.0, the measured distance is output as 4 [m], but as can be seen from FIG. 4, the actual distance is 5 [m]. , The error is 1 [m]. Therefore, when the intensity of the received signal changes, accurate distance measurement cannot be performed.

In order to reduce the time measurement error caused by the change in the received signal strength, the received wave strength adjusting unit 4
There is known a technique of measuring distance by adding 0. According to such a technique, the intensity of the received wave is adjusted by the intensity adjustment function of the received wave to obtain a received signal having a constant intensity, thereby reducing the measurement error based on the intensity change. That is, in FIG. 4, the value of the intensity S ₂ of the received signal becomes any one of the values, so that the relationship between the time difference between the transmitted and received signals at the zero crossing point (the phase difference) between the actual distance linear (pair One correspondence), so that accurate distance measurement was realized. For example, the intensity adjustment is performed using a mechanism corresponding to the aperture of the camera in the intensity adjustment unit 40.

[0006]

However, the conventional technique of measuring the distance by adding the received-wave intensity adjusting unit 40 has the following problems. That is, in such a technique, the intensity of the received signal is adjusted in order to reduce the error of the time measurement caused by the change in the intensity of the received signal, so that the time required for one distance measurement takes about several seconds.

Another problem is that accurate distance measurement cannot be performed unless the intensity of the received signal is constant during the time required for adjusting the intensity of the received signal. For example, a conventional distance measuring apparatus to which the strength adjusting unit 40 is added is installed on a pedestrian bridge,
Consider a case where a vehicle moving on a road under the pedestrian bridge is set as an object to be measured, and a distance to the object to be measured is measured. The ranging device installed on the pedestrian bridge transmits the carrier wave under the pedestrian bridge, and the point where the carrier wave is irradiated (hereinafter, referred to as
It is called "measurement point". ) Is received. Even if the car under test enters the measurement point and measures the distance to the test object before passing by the measurement point, the test object moves, so measurement is performed during the time required for adjusting the strength of the received signal. The reflectivity of the point changes. Therefore, the strength of the received signal is not properly adjusted, and the strength of the received signal cannot be constantly adjusted.
That is, if the intensity of the received signal changes during the time required for adjusting the intensity of the received signal, there is a problem that accurate distance measurement cannot be performed.

The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to perform a phase difference type distance measurement using a carrier modulated by a transmission signal. In this case, it is an object of the present invention to provide a distance measuring method which does not depend on a change in received signal strength. Another object of the present invention is to reduce a measurement error based on a change in the intensity of a received signal and to shorten the time required for distance measurement by using the distance measurement method.

[0009]

In order to solve the above-mentioned problems, a real-time phase difference ranging method according to the first invention of the present application transmits a carrier modulated by a transmission signal toward a target and reflects the carrier at the target. In the real-time phase difference ranging method that receives the carrier wave, obtains a received signal, and calculates a distance to a target based on a phase difference between the transmitted signal and the received signal, any one of the transmitted signal and the received signal One is the first signal,
Means for outputting the other signal as a second signal, shifting the first signal by a predetermined phase and outputting the signal shifted by the predetermined phase as a third signal, and multiplying and multiplying the first signal and the second signal Means for outputting the signal as a fourth signal, means for multiplying the third signal and the second signal and outputting the multiplied signal as a fifth signal, and means for outputting the fourth signal and the fifth signal. And a means for calculating the ratio of the DC components of the real-time phase difference ranging method.

The real-time phase difference ranging method according to the second invention of the present application transmits a carrier modulated by a transmission signal toward a target, receives the carrier reflected by the target, and obtains a reception signal. In a real-time phase difference ranging method that calculates a distance to a target based on a phase difference between a transmission signal and a reception signal, one of the transmission signal and the reception signal is a first signal, and the other is a second signal. Means for shifting the first signal by a predetermined phase and outputting the signal shifted by the predetermined phase as a third signal; multiplying the first signal by the second signal; Means for outputting as a signal,
Means for multiplying the third signal by the second signal and outputting the multiplied signal as a fifth signal; means for blocking the passage of the AC component of the fourth signal and passing the DC component; A real-time phase difference ranging method comprising: means for blocking the passage of the AC component of the signal and passing the DC component; and means for dividing both DC components as an input signal.

The real-time phase difference ranging method according to the third invention of the present application transmits a carrier modulated by a transmission signal toward a target, receives the carrier reflected by the target, and obtains a reception signal. In a real-time phase difference ranging method that calculates a distance to a target based on a phase difference between a transmission signal and a reception signal, one of the transmission signal and the reception signal is a first signal, and the other is a second signal. Means for shifting the first signal by a predetermined phase and outputting the signal shifted by the predetermined phase as a third signal; multiplying the first signal by the second signal; Means for outputting as a signal,
Means for multiplying the third signal and the second signal and outputting the multiplied signal as a fifth signal; dividing the fourth signal and the fifth signal as input signals; 6
And a means for blocking the passage of the alternating current component of the sixth signal and passing the direct current component of the sixth signal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a real-time phase difference ranging method according to the present invention will be described with reference to an embodiment. FIG. 1 is a block diagram of the embodiment. The configuration of the embodiment transmission is a transmission system,
It has a receiving system and a phase detector 1.

As a transmission system, an oscillator 10, a distributor 1
1, transmitter 12, transducer 13, mixer 14,
Oscillator 15, distributor 16, LPF (low-pass filter)
Seventeen. The oscillator 10 outputs a transmission signal having a frequency f, and the output signal of the oscillator 10 is input to the distributor 11.
For example, the frequency f of the oscillator 10 is set to 10 [MHz].
The splitter 11 splits the input signal into two output signals, and the splitter 11 splits the input signal from the oscillator 10 into the transmitter 1
2 and the mixer 14. The transmitter 12 is a distributor 11
A carrier wave modulated by an input signal (a transmission signal of a frequency f input from the oscillator 10) is transmitted from the transducer 13 to a target. Transducer 13
Converts an electric signal input from the transmitter 12 into a carrier. For example, when the carrier is an ultrasonic wave, an ultrasonic speaker may be used as the transducer 13. If the carrier is radio waves, the transducer 13
May be used as the transmission antenna. When the carrier wave is a light wave, a light emitting device may be used as the transducer 13. As the light emitting device, for example, an LED
(Light emitting diode) and LD (laser diode) can be used. Further, the oscillator 15 outputs an oscillation signal at a frequency (f + Δf) having a smaller difference than the frequency f of the oscillator 10. However, Δf ≠ 0 [MHz]. For example, if the frequency f of the oscillator 10 is 10 [MHz], the oscillator 1
5 (f + Δf) = 10.001 [MHz] or 9.999 [MHz], and the small difference frequency Δf of the frequency f
Absolute value | Δf | = 0.001 [MHz] = 1 [KHz]. The output signal of the oscillator 15 is input to the distributor 16. The distributor 16 converts the input signal from the oscillator 15 into the mixer 1
4 and the mixer 20. As a result, input signals from the oscillators 10 and 15 are input to the mixer 14. The mixer 14 includes the oscillator 10 and the oscillator 15
, And outputs the result to the LPF 17.
The LPF 17 blocks the input signal from passing through a frequency band equal to or higher than the frequency (2f + Δf), and the output signal of the LPF 17 is input to the multiplier 3 and the phase shifter 2 as a first basic signal.

The receiving system includes a transducer 18,
It has a receiver 19, a mixer 20, an LPF 21, an oscillator 15, and a distributor 16. The receiver 19 receives the carrier reflected by the target by the transducer 18 and outputs a received signal. Here, the received signal is shifted with respect to the transmitted signal by a phase difference す る corresponding to the distance that the carrier travels to and from the target. The received signal converts the carrier reflected by the transducer 18 into an electric signal. For example, when a carrier wave is an ultrasonic wave, an ultrasonic microphone may be used as the transducer 18. When a carrier is radio waves, a receiving antenna may be used as the transducer 18. When the carrier wave is a light wave, a light receiving device may be used as the transducer 18. As the light receiving device, for example, PD (pin photodiode), APD
(Avalanche photodiode). The output signal of the receiver 19 is input to the mixer 20.
As described above, the input signal from the oscillator 15 is input to the mixer 20 through the distributor 16. The mixer 20 multiplies the input signals from the receiver 19 and the oscillator 15 and outputs the result to the LPF 21. The LPF 21 blocks the input signal from passing through a frequency band higher than the frequency (2f + Δf),
The output signal of the LPF 21 is input to the multiplier 3 and the multiplier 4 as a second basic signal.

The phase detector 1 includes a phase shifter 2, a multiplier 3, a multiplier 4, an LPF 5, an LPF 6, and a divider 7. The phase shifter 2 shifts the input signal (first basic signal) from the LPF 17 by a predetermined phase γ and inputs the signal to the multiplier 4. Where 0
<Γ <2π. For example, the predetermined phase γ is set to π / 2. The multiplier 3 includes an input signal (first basic signal) from the LPF 17 and an input signal (second basic signal) from the LPF 21.
And outputs the result to the LPF 5. The multiplier 4 multiplies the input signal from the phase shifter 2 (the first basic signal shifted by a predetermined phase γ) with the input signal from the LPF 21 (the second basic signal), and outputs the result to the LPF 6. LPF5 is a multiplier 3
Block the input signal from the AC component from passing, and pass the DC component to output to the divider 7. The LPF 6 blocks the input signal from the multiplier 4 from passing the AC component, passes the DC component, and inputs the DC component to the divider 7. Divider 7 is LPF
5 is divided by the input DC signal from the LPF 6 as an input signal. That is, the divider 7 divides the input signal from the LPF 5 by the input signal from the LPF 6, or divides the input signal from the LPF 6 by the input signal from the LPF 5. As described above, L
Due to the configuration of PF5, LPF6 and divider 7, multiplier 3
And the DC component ratio of the output signal of the multiplier 4 and the output signal of the multiplier 4 can be obtained. Based on the output signal of the divider 7 as a function of the phase difference between the transmitted signal and the received signal, the distance can be determined.

Next, the operation of the embodiment will be described using mathematical expressions. The amplitude of the output signal of the oscillator 10 is At, the angular frequency is ω = 2πf, and the initial phase is α. At this time, the transmission signal Tx (t) output from the oscillator 10 is expressed as Tx (t) = (At / 2) [exp {j (ωt + α)} + exp {−j (ωt + α)}] = Atcos (ωt + α). You. Here, t means time, and j means an imaginary number. The transmitter 12 transmits a carrier modulated by a transmission signal of the frequency f output from the oscillator 10 to a target.

The receiver 19 receives the carrier reflected by the target by the transducer 18 and outputs a received signal. At this time, the received signal Rx (t) output from the receiver 19 is Rx (t) = (Ar / 2) [exp {j (ωt + α + ψ)} + exp {−
j (ωt + α + ψ)}]. The received signal Rx (t) will include information on the phase difference 対 応 corresponding to the distance that the carrier travels to and from the target.

The amplitude of the output signal of the oscillator 15 is Al, the angular frequency is ω + Δω = 2π (f + Δf), and the initial phase is β. At this time, the output signal Lo (t) of the oscillator 15 is Lo (t) = (Al / 2) [exp [j {(ω + Δω) t + β}] + ex
p [−j {(ω + Δω) t + β}]]. The oscillator 15 outputs an oscillation signal at a frequency f + Δf having a smaller difference than the frequency f of the oscillator 10.

The mixer 14 receives the input signal T from the oscillator 10
x (t) is multiplied by the input signal Lo (t) from the oscillator 15. At this time, the output signal Tx (t) × Lo of the mixer 14
(t) is Tx (t) × Lo (t) = (At / 2) [exp {j (ωt + α)} + exp {−j (ωt + α)}] × (Al / 2) [exp [j {(ω + Δω) t + β}] + exp [−j {(ω + Δω) t + β}]] = (AtAl / 4) [exp [j {(2ω + Δω) t + α + β}] + exp [−j {(2ω + Δω) t + α + β}] + exp {j (Δωt−α + β)} + exp {−j (Δωt−α + β)}]. The mixer 14 outputs a signal including two angular frequencies of (2ω + Δω) and Δω by multiplying signals having different angular frequencies.

The LPF 17 prevents the signal Tx (t) × Lo (t) input from the mixer 14 from passing through a frequency band equal to or higher than the angular frequency (2ω + Δω). At this time, the basic signal S ₁ (t) output from the LPF 17 is S ₁ (t) = (AtAl / 4) [exp {j (Δωt−α + β)} +
exp {−j (Δωt−α + β)}]. The LPF 17 outputs a signal including only the angular frequency Δω.

Similarly to the mixer 14, the mixer 20 multiplies the input signal Rx (t) from the receiver 19 by the input signal Lo (t) from the oscillator 15. At this time, the output signal Rx (t) × Lo (t) of the mixer 20 is Rx (t) × Lo (t) = (Ar / 2) [exp {j (ωt + α + ψ)} + exp {−j (ωt + α + ψ)} ] × (Al / 2) [exp [j {(ω + Δω) t + β}] + exp [−j {(ω + Δω) t + β}]] = (ArAl / 4) [exp [j {(2ω + Δω) ) t + α + β + ψ}] + exp [−j {(2ω + Δω) t + α + β + ψ}] + exp {j (Δωt−α + β−ψ)} + exp {−j (Δωt−α + β−ψ)}]. The mixer 20 multiplies signals having different angular frequencies to output a signal including two angular frequencies of (2ω + Δω) and Δω.

The LPF 21 prevents the signal Tx (t) × Ro (t) input from the mixer 20 from passing through the frequency band equal to or higher than the angular frequency (2ω + Δω). At this time, the basic signal S ₂ (t) output from the LPF 21 is S ₂ (t) = (ArAl / 4) [exp {j (Δωt−α + β−
ψ)} + exp {−j (Δωt−α + β−ψ)}]. The LPF 21 outputs a signal having only the angular frequency Δω.

The multiplier 3 receives the input signal S ₁ from the LPF 17.
(t) (first basic signal) and input signal S from LPF 21
₂ (t) (second basic signal). At this time, the output signal S ₁ (t) × S ₂ (t) of the multiplier 3 is S ₁ (t) × S ₂ (t) = (AtAl / 4) [exp {j (Δωt−α + β)} + exp { - j (Δωt-α + β )}] × (ArAl / 4) [exp {j (Δωt-α + β-ψ)} + exp {- j (Δωt-α + β-ψ)}] = (AtArAl 2/16) [exp [ j {2 (Δωt−α + β) −ψ}] + exp [−j {2 (Δωt−α + β) −ψ}] + exp (jψ) + exp (−jψ)]. The amplitude of the output signal of the multiplier 3 is a product of the amplitude At of the transmission signal, the amplitude Ar of the reception signal, and the square of the amplitude Al of the oscillation signal.

The LPF 5 receives the input signal S ₁ from the multiplier 3.
It blocks the passage of the (t) × S ₂ (t) AC component and passes the DC component. At this time, the output signal DC1 of the LPF ₅ is DC1 = (AtArAl 2/16) {exp (jψ) + exp (−j
ψ)}. The output signal DC1 of the LPF 5 is
And the initial phase β of the oscillator 15.

The phase shifter 2 receives the input signal S ₁ from the LPF 17.
(t) The (first basic signal) is shifted by a predetermined phase γ. However, it is assumed that 0 <γ <2π. At this time, the output signal S ₃ (t) (third basic signal) of the phase shifter 2 is S ₃ (t) = (AtAl / 4) [exp {j (Δωt−α + β−)
γ)} + exp {−j (Δωt−α + β−γ)}]. The amplitude of the _third basic signal S ₃ (t) maintains the amplitude of the first basic signal S ₁ (t).

The multiplier 4 receives the input signal S from the phase shifter 2
₃ (t) (first basic signal shifted by a predetermined phase γ) and LP
The input signal S ₂ (t) (second basic signal) from F21 is multiplied. At this time, the output signal S ₃ (t) × S of the multiplier 4
₂ (t) is S ₃ (t) × S ₂ (t) = (AtAl / 4) [exp {j (Δωt−α + β−γ)} + exp {−j (Δωt−α + β−γ)}] × ( ArAl / 4) [exp {j (Δωt-α + β-ψ)} + exp {-j (Δωt-α + β-ψ)}] = (AtArAl 2/16) [exp [j {2 (Δωt-α + β) -γ- ψ}] + exp [−j {2 (Δωt−α + β) −γ−ψ}] + exp {j (ψ−γ)} + exp {−j (ψ−γ)}]. The amplitude of the output signal of the multiplier 4 is the product of the amplitude At of the transmission signal, the amplitude Ar of the reception signal, and the square of the amplitude Al of the oscillation signal.

The LPF 6 receives the input signal S ₃ from the multiplier 4
It blocks the passage of the (t) × S ₂ (t) AC component and passes the DC component. At this time, the output signal DC2 of the LPF ₆ is DC2 = (AtArAl 2/16) [exp {j (ψ−γ)} + ex
p {−j (ψ−γ)}]. The output signal DC2 of the LPF 6 is
And the initial phase β of the oscillator 15.

The divider 7 receives the input signal DC1 from the LPF 5
Is divided by the input signal DC2 from the LPF 6, or the output signal DC2 of the LPF 6 is
Divide by C1. The divider 7 outputs the output signal DC2 of the LPF 6.
When dividing the output signal DC1 of LPF5, the output signal R of the divider 7 is R = DC2 / DC1 = (AtArAl 2/16) [exp {j (ψ-γ)} + exp {-j (ψ- _{γ)}] / (AtArAl 2} /16) {exp (jψ) + exp (-jψ)} = [exp {j (ψ-γ)} + exp {-j (ψ-γ)}] / {exp (jψ) + Exp (−jψ)}. The output signal R of the divider 7 does not depend on the amplitude At of the transmission signal, the amplitude Ar of the reception signal, and the amplitude Al of the oscillation signal. Here, since the predetermined phase γ is known, the output signal R of the divider 7 depends on the phase difference ψ between the transmission signal and the reception signal. In particular, when the phase section 2 shifts the input signal S ₁ (t) from the LPF 17 by a predetermined phase γ = π / 2, the output signal R of the divider 7 becomes R = [exp {j (ψ−π / 2). )} + Exp {−j (ψ−π / 2)}] / {exp (jψ) + exp (−jψ)} = tanψ. When the predetermined phase γ = π / 2, the divider 7
Can be expressed by a simple equation, and the distance can be easily calculated from the phase difference ψ. Also, as shown in FIG.
The relationship between the phase difference の between the transmission signal and the reception signal and the normalized distance to the target is one-to-one. Therefore, even if the intensity of the received signal changes, accurate distance measurement can be performed.

As a configuration of the embodiment, the phase shifter 2 is provided between the LPF 17 and the multiplier 4, and the phase shifter 2 shifts the input signal (first basic signal) from the LPF 17 by a predetermined phase γ. As a configuration of the embodiment, a phase shifter 2 is provided between the LPF 21 and the multiplier 4, and the phase shifter 2 shifts an input signal (second basic signal) from the LPF 21 by a predetermined phase γ. Can be implemented. Further, as a configuration of the embodiment, an LPF 5 is provided between the multiplier 3 and the divider 7, an LPF 6 is provided between the multiplier 4 and the divider 7, and the divider 7 receives an input from the multiplier 3 and the multiplier 4. Is divided as an input signal. However, as another embodiment, the LPF 5 and the LPF 6 are not provided, and the divider 7 has a direct input signal from the multiplier 3 and a direct input signal from the multiplier 4. Is divided as an input signal, and the output signal of the divider 7 is blocked by passing an AC component and passing a DC component.
The present invention can also be implemented by providing a PF.

[0030]

As described above, the present invention realizes a means for removing a signal caused by a change in intensity from a received signal when performing phase difference type ranging using a carrier modulated by a transmitted signal. There is an effect that the measurement error based on the change in the intensity can be wiped off because of the strong change in the reflectance of the object. In addition, since it is not necessary to adjust the intensity of the received signal, which is conventionally required, the period of the intensity adjustment can be omitted, and the time required for one distance measurement can be reduced to about 1/1000 (several milliseconds) of the conventional one. This has the effect of being done. further,
Since the time required for one measurement is extremely short, there is an effect that high-speed continuous measurement is enabled.

[Brief description of the drawings]

FIG. 1 is a block diagram of a real-time phase difference ranging method of the present invention.

FIG. 2 is a block diagram of a conventional phase difference ranging method.

FIG. 3 is a diagram showing a relationship between a normalized distance and a phase difference in the real-time phase difference ranging method of the present invention.

FIG. 4 is a diagram illustrating a relationship between a distance and a phase difference in a conventional phase difference ranging method.

[Explanation of symbols]

1, 30 Phase detector 2 Phaser 3, 4 Multiplier 5, 6, 17, 21 LPF 7 Divider 10, 15 Oscillator 11, 16 Divider 12 Transmitter 13, 18 Transducer 14, 20 Mixer 31, 32 Zero crossing detector 33 Counter 40 Strength adjuster S ₁ , S ₂ Received signal strength

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) EA05

Claims (3)

[Claims] 1. A carrier wave modulated by a transmission signal is transmitted toward a target, the carrier wave reflected by the target is received to obtain a reception signal, and a distance to the target is determined based on a phase difference between the transmission signal and the reception signal. In the real-time phase difference ranging method, one of the transmission signal and the reception signal is set as a first signal, the other is set as a second signal, and the first signal is phase-shifted by a predetermined amount. The phase-shifted signal is
Means for multiplying the first signal by the second signal and means for outputting the multiplied signal as a fourth signal; multiplying the third signal by the second signal; A real-time phase difference ranging method comprising: means for outputting the multiplied signal as a fifth signal; and means for calculating a ratio of a DC component between the fourth signal and the fifth signal. 2. A method of transmitting a carrier modulated by a transmission signal toward a target, receiving the carrier reflected by the target, obtaining a reception signal, and determining a distance to the target based on a phase difference between the transmission signal and the reception signal. In the real-time phase difference ranging method, one of the transmission signal and the reception signal is set as a first signal, the other is set as a second signal, and the first signal is phase-shifted by a predetermined amount. The phase-shifted signal is
Means for multiplying the first signal by the second signal and means for outputting the multiplied signal as a fourth signal; multiplying the third signal by the second signal; Means for outputting the multiplied signal as a fifth signal, means for blocking the passage of the AC component of the fourth signal and passing the DC component, and means for blocking the passage of the AC component of the fifth signal and passing the DC component And a means for dividing the both DC components as an input signal. 3. A carrier wave modulated by a transmission signal is transmitted toward a target, the carrier wave reflected by the target is received to obtain a reception signal, and a distance to the target is determined based on a phase difference between the transmission signal and the reception signal. In the real-time phase difference ranging method, one of the transmission signal and the reception signal is set as a first signal, the other is set as a second signal, and the first signal is phase-shifted by a predetermined amount. The phase-shifted signal is
Means for multiplying the first signal by the second signal and means for outputting the multiplied signal as a fourth signal; multiplying the third signal by the second signal; Means for outputting the multiplied signal as a fifth signal, means for dividing the fourth signal and the fifth signal as input signals, and outputting the divided signal as a sixth signal; Means for blocking the passage of an alternating current component and passing a direct current component.