JPS63158485A - Phase detector - Google Patents

Abstract

PURPOSE:To reduce a phase error, by averaging the phase difference of a detection signal received without being passed through a delay circuit to the original detection signal and the phase difference of a detection signal received through a 1/2 wavelength delay circuit to the original detection signal. CONSTITUTION:The original detection signal (a radio wave or sonic wave) from a signal generating part 1 is projected to an object 5 to be measured through a wave guide 2. The detection signal reflected from, transmitted through or scattered by the object 5 is received by a receiving part 7 through a wave guide 6. A receiving signal is inputted to a phase measuring part 8 and the phase difference between said signal and the original detection signal is measured. An arithmetic control part 9 operates a change-over part 3 and projects the original detection signal to the object 5 through a 1/2 wavelength delay wire 4. The phase difference at this time is also measured by the measuring part 8 and subjected to arithmetic mean along with the phase difference not passed through the delay wire 4. Whereupon, the phase error due to a leakage signal 20 is negated and measuring accuracy is enhanced. This apparatus is utilized in an ultrasonic range finder.

Description

[Detailed Description of the Invention] Objective 1 of the Invention (Industrial Application Field) This invention aims to calculate the delay time when a detection signal such as a sound wave passes through an object to be measured by determining the phase difference between the detection signal and the transmitted detection signal. The present invention relates to a phase detection device that detects a phase difference and measures a physical distance such as ω from this phase difference.

(Prior Art) As a device that detects the delay time when a detection signal passes through an object to be measured as a phase difference with the transmitted detection signal, and measures a specific physical quantity of the object to be measured from this phase difference, For example, there is a device 2 that uses sound waves to measure required physical quantities such as distance, temperature and humidity of a propagation medium.

Such measuring devices are based on substantially the same principle as described above, and devices using, for example, 'Fi magnetic waves such as microwaves as detection signals, and devices using light waves are also known.

When using microwaves or light waves, it may be difficult to detect the phase of the carrier, so a signal that has been modulated, such as intensity modulation or frequency modulation, is often used as the detection signal.

Even when ultra-Δ waves are used, a modulated signal may be used as a detection signal depending on the object to be measured.

(Problems to be Solved by the Invention) However, in the above-mentioned phase detection device, if electrical coupling occurs between the detection signal sending side and the receiving side, or if the detection signal, such as a sound wave or an electromagnetic wave, , or when reflection and scattering occurs for some reason in waves such as light waves, signals other than the detection signal that have passed through the object to be measured may be mixed into the receiving side. There is a problem in that a phase error occurs in the detection signal, resulting in a decrease in measurement accuracy.

The phase error caused by such losstalk (leakage signal), etc. is caused by the combination of the received detection signal S and crosstalk E, as shown in FIG.
Therefore, as shown in Figure 3 (B), it occurs periodically in response to changes in the physical quantity to be measured, and the period is thought to be approximately equal to one wavelength of the detection signal. .

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a phase detection device that can significantly reduce phase errors and improve measurement accuracy.

[Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention detects the phase difference between the transmitted detection signal and the detection signal that has passed through the object to be measured, and A device that measures a specific physical quantity of the target to be measured from the phase difference, and includes a signal generator that transmits a detection signal to the target, and a wavelength that is half the wavelength of the detection signal transmitted from the signal generator. a delay means having a delay characteristic corresponding to the above, and a receiving section that receives the detection signal that has passed through the object to be measured;
a first phase difference between the detection signal generated in the signal generation section and the detection signal received by the reception section without going through the delay means; a second detection signal received by the receiving section;
and a calculation means for arithmetic averaging the first phase difference and the second phase difference, and using the arithmetic averaged phase difference as a phase difference for measurement. The gist is that.

(Function) A phase error caused in the detection signal due to crosstalk occurs periodically at a period approximately equal to one wavelength of the detection signal.

When a detection signal with a phase error occurring at such a period passes through a delay means having a delay characteristic corresponding to 172 wavelengths of the detection signal, the phase error occurring in the detection signal will be 1/2 wavelength (180 ') will be delayed.

Therefore, the first phase difference between the original detection signal generated in the signal generation section and the detection signal received at the reception section without going through the delay means, and the first phase difference between the original detection signal and the detection signal received at the reception section through the delay means. When the second phase difference between the first phase difference and the second phase difference is detected by the phase measuring section and the arithmetic average of the first phase difference and the second phase difference is taken, the phase error occurring in the detection signal is penetrated and becomes noticeable. It is reduced, and a high-precision measurement is made.

(Example) Examples of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram showing the overall configuration, and FIG. 2 is a waveform diagram for explaining the phase error compensation effect by the quadratic average.

First, the configuration will be described. In FIG. 1, numeral 1 denotes a signal generating section, which is composed of a generator of either electromagnetic waves such as acoustic waves or microwaves, or light waves.

The signal generator 1 also includes a modulator for subjecting these signals to intensity modulation or frequency modulation, if necessary.

From the signal generator 1, N! of sound waves, microwaves, etc.
A signal consisting of either a single wave, a light wave signal, or a modulated signal thereof is transmitted as a detection signal.

The signal generating section 1 is connected to a switching contact C in a switching section 3 via a transmitting waveguide 2 . As the waveguide 2, a waveguide is used for microwaves, and an optical fiber is used for light waves.

A delay line (delay means) 4 is connected to the fixed contact a in the switching section 3.
is connected, and the other end of the delay 114 and another fixed contact are commonly connected, and the common connection point communicates with the medium to be measured (object to be measured) 5 via the transmitting waveguide 2 .

The switching unit 3 is switched and controlled by a control signal from a calculation control unit, which will be described later.

Further, the delay [14] has a delay characteristic corresponding to 1/2 wavelength of the detection signal, and is realized by setting the waveguide to a required length.

6 is a receiving waveguide, and the detection signal projected from the transmitting waveguide 2 onto the medium 5 to be measured is reflected by the medium 5 to be measured;
Or, after being transmitted, scattered, etc., it is guided to the receiving side waveguide 6.

The receiving waveguide 6 is connected to a receiving section 7 that receives the detection signal that has passed through the medium 5 to be measured. When the detection signal is a sound wave, a light wave, or the like, the received signal is converted into an electric signal by the receiving section 7.

Reference numeral 8 denotes a 1-phase measuring section, and the detection signal generated by the signal generating section 1 and the detection signal received by the receiving section 7 are input to the phase measuring section 8 . In the phase measuring section 8, the detection signal generated in the signal generating section 1 and the receiving section 7 without going through the delay line 4 are connected to each other.
The first phase difference between the original detection signal received at the signal generating section 1 and the second phase difference between the original detection signal generated at the signal generating section 1 and the detection signal received at the receiving section 7 via the delay line 4 are respectively Detected.

9 is a calculation control unit (calculation means), and the calculation control unit 9 is
It also has a temporary storage function for phase difference data etc. detected by the receiving section 7, and this arithmetic control section 9 performs arithmetic processing such as an arithmetic mean of the above-mentioned first phase difference and second phase difference.

Also, a control signal from the calculation control unit 9! ! 11 communicates with the switching section 3.

Next, the operation will be explained using FIG. 2.

In response to a control signal from the arithmetic control section 9, the switching section 3 is first switched to the fixed contact side, and the original detection signal generated in the signal generating section 1 and the delay 1! The first phase difference with the detection signal received by the receiving unit 7 without passing through i14 is detected by the phase measuring unit 8. The detected first phase difference signal is temporarily stored in the calculation control section 9.

When crosstalk or the like occurs, the first phase difference signal includes a phase error that occurs periodically at a period approximately equal to one wavelength of the detection signal.

Next, the switching unit 3 is switched to the fixed contact a side by a control signal from the calculation control unit 9, and the original detection signal generated in the signal generation unit 1 and the detection signal received by the reception unit 7 via the delay line 4 are A second phase difference between the two is detected by the phase meter 1111 section 8.

Since the delay line 4 has a delay characteristic corresponding to 1/2 wavelength of the detection signal, the detected second phase difference signal includes the previously detected first phase difference signal. A phase error delayed by 1/2 wave (180°) is included with respect to the phase error contained therein.

The second phase difference signal is sent to the arithmetic and q control section 9, and the arithmetic mean of the first phase difference and the second phase difference is calculated. As a result, the phase error occurring in the detection signal is canceled out, and the physical quantity of the object to be measured can be measured with good viscosity based on the phase difference from which the phase error has been removed.

Next, the above phase error removal effect will be further explained using a mathematical formula. ``Phase errors due to crosstalk, etc. exhibit periodicity approximately equal to one wavelength λ of the detection signal (second
In the figure (a)). Therefore, the phase error becomes zero for every 1/2 length.

Therefore, this phase error Δφ1 is expressed as Δφ, −ΣAn −s i n2 (n+1) πL
/λn=0 (1) It is written as follows.

On the other hand, since the delay II4 has a delay characteristic corresponding to 1/2 wavelength of the detection signal, the phase error Δφ2 in the detection signal passing through the delay line 4 is Δφ2=Σ(-1)n+
l△n-5in2n=Q ・(n+1)πL/λ (2) ((b) in Fig. 2), and the error ΔφC after taking the arithmetic mean in the arithmetic control unit 9 is ΔψC=ΣA2 m+ 1・S i n4 (m
+ 1) m=0 ・πL/λ...(3) In the above equation (3), Ao1 including the error component of the fundamental period.
Since the terms △2, A4, etc. are not included, the error ΔφC is
As shown by the waveform (c) in FIG. 2, it is significantly reduced.

In this way, the periodically occurring phase error is compensated, and accurate physical quantity measurement is performed.

Note that a certain amount of phase error with respect to the measured phase can be easily removed by offset adjustment.
It is not an important error factor in the measurement.

[Effects of the Invention] As described above, according to the present invention, a delay means having a delay characteristic corresponding to 1/2 wavelength of the detection signal is provided, and the original detection signal generated in the signal generation section is and the detection signal received by the receiving section without going through the above-mentioned delay means.
The phase difference between the original detection signal and the detection signal received by the reception section via the delay means is detected by the phase measurement section, and the calculation means calculates the first phase difference. and the arithmetic mean of the second phase difference is taken, so
This has the advantage that periodic phase errors caused in the detection signal due to crosstalk and the like are canceled out, and measurement accuracy is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the phase detection device according to the present invention, FIG. 2 is a waveform diagram for explaining the phase error compensation effect according to the same embodiment, and FIG. 3 is a phase diagram showing the phase error caused by crosstalk. FIG. 3 is a diagram showing waveforms of errors, etc. 1: Signal generation section, 2.6: Waveguide, 3: Switching section, 4: Delay line, 5: Medium to be measured (object to be measured), 7: Receiving section, 8: Phase measurement section, 9: Arithmetic control section (calculating means). Agent Patent Attorney Noriyuki Chika Agent Patent Attorney Hiroshi Mitsumata Bunsan 1 Figure

Claims (2)

[Claims] (1) A device that detects a phase difference between an emitted detection signal and a detection signal that has passed through an object to be measured, and measures a specific physical quantity of the object to be measured from the phase difference, a signal generator that transmits a signal to
a delay means having a delay characteristic corresponding to the wavelength; a receiving section that receives the detection signal that has passed through the object to be measured; and a second phase difference between the detection signal generated in the signal generating section and the detection signal received by the receiving section via the delay means.
and a calculation means for arithmetic averaging the first phase difference and the second phase difference and using the arithmetic averaged phase difference as a phase difference for measurement. A phase detection device characterized by: (2) The detection signal generated by the signal generating section is composed of a sound wave, an electromagnetic wave, a light wave, or a modulation signal of the signal. Phase detection device according to item 1.