JPS60142274A - Comparing and measuring system - Google Patents

Abstract

PURPOSE:To simplify a constitution of a measuring system, and also to improve a measuring accuracy and a stability by constituting so that an arrival time of a signal to a receiver from a transmission line to be measured and a reference transmission line, respectively is made different from each other. CONSTITUTION:A divider D divides an output signal of a signal source SG by a prescribed ratio, and outputs it simultaneously to a reference transmission line L0 and a transmission line LX to be measured. A variable attenuator VA is connected in series to the transmission line LD, and a passing signal is delayed by a signal from a signal processing control part SPC. A coupler C of a receiving side supplies signals from the transmission lines LD, LX, to a receiver REC. Subsequently, basing on a base band output signal from the receiver REC, the control part SPC forms a DC signal, and adjusts the attenuation quantity of the attenuator VA so that an absolute value of its level becomes the minimum.

Description

[Detailed Description of the Invention] A method of comparing and measuring the transmission loss of a signal transmission path, the amount of transmission, frequency characteristics, and all of their fluctuations. Figure 1 shows an example of a measurement system configuration as an example of a conventional comparative measurement method. be. In FIG. 1, a signal source SG, a divider D, and a reference transmission line L are shown. A measurement in which signals are transmitted in the following order: a parallel body of the variable attenuator VA and the transmission line under test LX, a parallel body of the suite SW, the receiver RFC, the detector SWD, and the SWD2, the comparator COMP, and the control unit CRL. It shows the system. And switch SW, receive! REC, detectors SWD1 and SWD2
is switched and controlled by a signal from a synchronizing signal generator TM.

Furthermore, the amount of attenuation of the variable attenuator VA can be changed by a signal from the control unit CRL.

The output signal of the signal source SG is transmitted by the divider D in the direction of the arrow in the figure with low loss and is divided into two directions at a constant ratio. Among these, the unidirectional reference transmission line L. The signal sent to is input to one input terminal of switch SW via variable attenuator VA. The signal sent to the transmission line under test LX in the other direction is directly input to the input terminal of the switch SW. In the switch SW, each transmission line L is connected in accordance with the synchronization signal from the synchronization signal generator TM. , LX alternately transmit signals from the receiver RFC. The output signal from the receiver RFC is further transmitted in two directions, and the detection 6 SWD□
, is transmitted to SWD2. This detector SWD, , S
The WD2 is composed of, for example, a switch and a memory circuit, and operates in synchronization with the switch SW in accordance with a synchronizing signal from a synchronizing signal generator TM. That is, for example, when the switch SW is connected to the reference transmission line LO side, the detection bswD1
On the other hand, when the switch SW is connected to the transmission line under test LX, the detector SWD2 is operated.

The output signals of the detectors swD; and SWD2 are compared by a comparator COMP, and it is determined which transmission path has a higher signal level. The output of the comparator COMP is controlled by the control device CRL to increase or decrease the amount of attenuation of the variable attenuator VA, so that the two input signal levels to the comparator COMP are finally equalized. Thus, the attenuation of the variable reducer and the reference transmission line. The transmission characteristics of the transmission line under test Lx can be known from the known characteristics of other measurement systems other than the transmission line under test LX.

However, in this conventional comparative measurement method,
Further separated from the receiver REC are detectors 5WD1 and 5WD.
2, and then the level is judged by the comparator COMP, which makes the configuration of these measuring threads complicated, and the detection 'gfSWD 1, 5WD2, comparator COMP, etc. are not used for level detection or comparison. Since it is processed as a DC signal, fluctuations in the DC level of these signal processing elements directly affect the measurement accuracy, and many switches are required, including not only the switch 8W but also the detectors 5WD1 and 5WD2. , nt++ has the disadvantage of causing deterioration in accuracy and stability.

Therefore, in view of the above-mentioned drawbacks, the present invention aims to provide a comparative measurement method that simplifies the configuration of the measurement system, improves measurement accuracy, and improves stability and placement.

The present invention, which achieves this object, sends a signal from a signal source to a fixed transmission path and a reference transmission path to which it is to be received, and receives the signals from these transmission paths by a base band receiving unit having one receiving unit.
A direct current whose level is 1° higher than the amplitude or power of at least one of the alternating current signal component or the fundamental wave 1i component received by the receiver that outputs M@k and included in the periodic signal from this receiver. In the measurement thread that connects the No. 1g processing system that outputs the signal, connect an interference reducer to at least one of the transmission line to be measured and the reference transmission line, and connect the transmission line to be measured and the reference transmission line to The signals from the two transmission paths are mutually received by the single receiver at different arrival times to the upper We receiver, and this single receiver outputs The attenuation of the variable attenuator is adjusted so that the absolute value of the level of the DC signal obtained by the processing system No. 4b becomes the minimum, and this step The method is characterized in that the transmission line to be measured is measured from the subsequent attenuation resistance and the characteristics of a measurement system other than the transmission line to be measured.

Embodiments of the present invention will now be explained with reference to FIG.
do. FIG. 2 shows an embodiment of the 7.1g signal source SG, divider, and reference transmission path. and the measurement thread t, through which the signal is transmitted in the order of the parallel body of A and the measured transmission line LX, the coupler C1 receiver RFC, and the signal processing tlI control unit SPC.
It's been a long time. A control signal is input to the variable attenuator VA from the signal processing control section SPC. Further, the signal processing control unit SPC and the signal gJ1. A synchronization signal is sent from the signal processing discount unit SPC to the signal processing unit 10j connected to the SG from the signal P-B 12 to the isG, or in the opposite direction.

The configuration shown in FIG. 2 will be explained in detail. The signal source SG periodically generates a rectangular pulse No. 16. The envelope of this signal is close to a rectangle, and the first one is sufficient, and IIJ month υ
These include an unmodulated or temporarily modulated alternating current signal whose amplitude is changed by a single rectangular pulse, and a so-called rectangular pulse obtained by periodically cutting out the i'II-flow No. 1g. This includes unchangeable or variable pitch signals whose amplitudes are varied by periodic rectangular pulses.

The time point at which the signal source SG generates the rectangular pulse-like information is synchronized with the synchronization number 18 outputted by the signal processing control unit SPC. In order to correlate the 1B@ source SG and the signal processing control section SPC, a synchronization signal may be sent to the signal processing control section SPC every time a rectangular pulse-like signal is generated periodically. Specific signal sources SG include gate oscillation or sine wave oscillators with 100% amplitude control, sine wave oscillators that can simultaneously perform J or O: 4 oscillation and amplitude modulation; for air signals. It can also be used as a signal source, such as a laser diode driven by a short signal source, or a laser diode that modulates the output light with an external variable power source driven by the same signal source. can be used as a signal source for the original signal. In addition, the latter (J, 1.9 external modulator) is claimed to have a good extinction ratio, and there are so-called ultrasonic optical modulators that make use of the transsonant effect, and 'fli,
Optical modulators using Kegen Gakusei Kuhaku can be used.

The division 5D is a standard transmission path in which the signal is transmitted in the direction of the arrow in FIG. 2 with low loss and the output of the transmission source SG is divided at a fixed ratio. and the transmission line under test Lx at the same time. In a split device that causes high loss to signals passing in directions other than the direction of the arrow in Figure 2, reflections from each element of the measurement system, such as the transmission line, variable attenuator, coupler, receiver, etc., affect measurement accuracy. This is to reduce the impact. The splitter Ri D for electrical signals includes a circuit that extracts signals through two resistors of appropriate values connected to the output terminal of a low output impedance amplifier, a directional coupler in each building, etc. There is. In addition, as a splitter for the original signal, polarizing prisms such as Wollaston prism and Lotsuzoyono prism, optical branching with a dielectric film anti-transparent mirror sandwiched between two distributed index lenses, @electric material There are Y-shaped optical waveguides formed inside or on the surface of a dielectric body, optical waveguide directional couplers similarly formed using a dielectric substrate, and semi-transparent mirrors.

Standard transmission line connected to the divider. and transmission line under test L
X is a waveguide, a coaxial line, an electric signal transmission line such as an IJ tube line or a Retzchel line, or a source such as a single mode source fiber, a multimode source fiber, a polarization maintaining optical fiber, or an aerial transmission line. It is a transmission line. In addition, the standard transmission line 1.0
It is not necessary that the transmission line LX and the transmission line under test LX are the same and unique transmission line. Especially the reference transmission path. is the divider and variable attenuator V
It may be a short-distance transmission path connecting to A, or it may be a mere space depending on the case. These transmission routes. , What is highly praised about LX is that the signal transmission time is different, and the axis alignment is 6.
Each transmission path input to C. The goal is to delay transmission so that LX signals do not overlap in time.

Reference transmission path. The variable attenuator VA connected in series is used to adjust the amount of attenuation, and allows the signal to pass with attenuation set by a signal or instruction from the signal processing controller SPC or by manual operation. This attenuation level is a value that minimizes the absolute value of the level of the DC signal produced by the signal processing controller SPC.

This will be described in detail later. Specific examples of variable attenuators VA include one that obtains attenuation by combining fixed resistors in each building, and one that obtains the attenuation amount by combining fixed resistors in each building, and one that obtains the attenuation amount by combining fixed resistors in each building, and one that obtains the attenuation amount by combining fixed resistors in each building, and one that obtains the amount of attenuation by combining fixed resistors in each building. A fixed attenuation is obtained by rotating a plate, a fixed attenuation is obtained by rotating one or both of two polarizing prisms arranged in series with the optical path, and a fixed attenuation rat Sudoku. There are devices that combine attenuators to obtain a predetermined amount of attenuation and are used for optical signals. In the example shown in FIG. 2, the variable attenuation table device A is placed in series with the reference transmission line LO, but it is placed on the side of the transmission line to be measured LX. An application is also possible in which it is placed in the LX to widen the measurement range of the transmission amount.

In addition, there are two transmission paths. Adjust the signal division ratio of the divider so that the levels of the signals reaching the receiving end of the LX are approximately equal,
It is advantageous for measurement purposes that the variable attenuator VA be used only for fine adjustment of the signal level.

Reference transmission path. and the transmission line under test Lx.The coupler C placed on the receiving end side of both transmits the signal sound with low loss in the direction of the arrow in Fig. 2, and transmits the signal sound in the direction of the arrow in Fig. It causes loss and is a 21-strong transmission path. The signal from LX is output from the output terminal of 11b'r1.

'Coupler C for electrical signals includes one that inputs the signal through each of the 21β1 resistors connected to the input terminal of the low input Innovidance amplifier and extracts the signal from the output terminal, and a directional coupler of each type. and so on. Furthermore, as a coupler for optical signals, the ones mentioned above as dividers for original signals may be used in the opposite direction.

A receiver REC can be placed after the coupler C and each transmission path. , Lx are both received.

In other words, the reference transmission path. Since the 1ttl during transmission is different from that of the transmission path to be measured, the signals transmitted through each transmission path do not overlap completely in time and are transmitted to the receiver RF C.
reach. The receiver REC is composed of one receiving element or one receiving element and a circuit system that performs signal processing of an amplifier on its output, and outputs a baseband received signal.

As the receiver REC, three types of concrete configurations are possible. In the first configuration, the output of the signal source SG is a baseband signal, and a receiving element is used that obtains an output signal with the same wave number as the input signal. Therefore, the output signal of the receiving element does not undergo frequency conversion. This is also the case when the signal is a baseband signal, such as a receiver that performs amplification using a bipolar transistor, field effect transistor, vacuum tube, etc. as a receiving element. The second configuration outputs a basebad signal by combining a receiving element without a frequency conversion function and a circuit system that performs frequency conversion at a subsequent stage, and is the output of the receiving element listed as the first configuration example above. Bipolar transistor, field effect transistor, vacuum tube, '51
A frequency converter in which a variable capacitance diode or the like is operated in a region with a non-linear input/output relationship, such as a receiver that converts to a baseband signal, or a receiver that converts the output of the receiving element in the first configuration example above to an appropriate band. There are receivers that convert the frequency of a signal, rectify the converted signal, and pass it through a low-pass filter or a band-pass filter to obtain a baseband signal. In this case, the former method of converting directly to the baseband (fN) has a simple configuration, but the oscillation frequency of the local oscillator input to the frequency converter is converted to the output of the signal source SG.
It is necessary to accurately match the frequency of the image frequency and to keep the phase difference between the signals of these image frequencies constant. The latter method, in which a basebad signal is obtained through a filter after rectification, has a slightly more complicated configuration, but is less susceptible to frequency and phase fluctuations. Note that the filter in the latter case can also be regarded as a component of the signal processing control unit 5PCO, which will be described later.

As a third configuration, the receiving element is removed from the receiver of the second configuration example, and the signal is input directly to the element that performs frequency conversion, and the receiver includes an M receiver, a PIN photodiode, an avalanche photodiode, a pyroelectric element, There are receivers for original signals that use photoconductive elements, metal/oxide/metal junction elements, etc. as receiving elements.

The signal processing control unit SPC includes a signal processing system, a control drive unit that generates a signal to adjust the attenuation amount of the variable attenuator according to the signal output from the signal processing system, and a control drive unit that controls and controls these operations.
It consists of a management part. Signal processing control unit SP
In C, a blood flow signal having a level corresponding to the amplitude or power of the AC signal component or DC signal component of this signal is created based on the baseband output signal of the received '15 REc,
l1 so that the absolute value of the level of this DC signal is the minimum.
It outputs a signal or instruction to adjust the attenuation amount of the lIJ variable attenuator VA.

Here, the 1st number processing control unit SPC will be explained in detail. Here, first, the 1
Saba will explain the signal processing method in the signal processing system.

(Explanation of the signal processing method in the object signal processing system) The signal processing method here is to create No. 1d from the output signal of the receiver REC, which serves as a guideline for adjusting the amount of reduction of the transducer. It's a method. FIG. 3(a) shows a periodic signal waveform that is the output signal of the receiver. Figure 3(b) is Figure 3(a)
This shows the AC signal waveform mentioned in the signal shown in . In this Figure 3, 'r is the output signal of the receiver (hereinafter receiver 1
t1t3 is the duration of the rectangular pulse-like signal, t2t4 is the idle time between adjacent rectangular pulse-like signals, a1a3 is the level of the rectangular pulse-like signal No. 1, ao is the reception output This is the average level of the signal. The rectangular pulse-like signal of duration t1 is a signal transmitted to either the reference transmission line or the to-be-receiving rectangular transmission line. Also,
When the free time ala3 is a positive value, there is a free space, and when the free time ala3 is a negative value, adjacent rectangular pulse signals overlap in time. Figure 3(b) crosses 1, the waveform is Figure 3(a)
) The reception output is 1g by using a filter or other means from the signal shown in
The average level of DC can be removed.

The signal processing system must have the function of outputting a blood flow signal at a level R: , °f relative to the amplitude or power of either the AC signal component or the fundamental wave signal component that is received in the dark. Although this has been described above, the signal processing method at Yotsuyu Station for the received output signal shown in FIG. 3(a) will now be described.

+l) In the signal processing method of extracting the sine wave signal component from the received output signal using a filter and obtaining a DC signal having a level corresponding to the amplitude of the 111 components of this sine wave, first, the frequency of the received output signal is extracted from the received output signal. A sine wave (the I component is extracted by a filter, and then the sine wave signal component is set to i>iCL using a diode, and then passed through a low-pass filter, or the maximum value and minimum value are peaked). Then, a direct current signal with a level corresponding to the amplitude of the sine wave signal component is obtained. The amount of attenuation of the liquid attenuator is adjusted so that the absolute value of the level of this DC signal is minimized. Here, let's assume a filter that obtains a sine wave signal component,
What is the ideal narrow I near the sexual cycle T? A filter that allows only signals in the 11 wave number band to pass through with low loss is good, and the signal extracted by this filter from the received output signal is 16
When the number levels a0 and a3 are difficult, they become zero, and al and a
3, it is desirable that it be as large as possible.

Therefore, in order for the amplitude to become zero at signal level al-a3, t□-t3. t2=t4t1+t2=T72
Naru'P FF is necessary! L1 double issue level lol a3
In order for the amplitude T to be maximum at t1=t3-2. t2-=t4
= 0 is necessary. In particular, if the former relationship of a1=a3 is not satisfied, the signal level will not be a1-a3 when the amplitude is low, and the measurement error will increase by the difference between the two values ala3. Therefore, in order to improve the measurement accuracy, it is necessary to match the output information with the waveform satisfying the waveform T shown in Section 4, Sho 1(b).

(2) In the foil processing method, the AC signal component is extracted from the received output signal using all phases of the filter, and the DC signal at the level is compared to the average amplitude of this AC signal component.
Extract the AC signal components shown in Figure 3(b) using a filter that removes only the DC signal components, such as a conotenosa.
Next, as in (1), a diode, a low-pass filter, a peak value detector, etc. are used to generate a blood flow (3) at a level corresponding to the average amplitude of the Xj: flow 1h component (3).

Then, as in (1), the attenuation f=> of the oJ variable attenuator is adjusted so that the absolute value of the level of this surface current and signal becomes the maximum. Also in this signal processing method, the received output signal shown in FIG. 4(b) is preferable. This is due to the following reason. Even if the signal level is a
Even if and a3 become small, the average amplitude does not become zero.

Of course, the average absolute value of the amplitude becomes zero when the signal levels a and a3 of the received output signal shown in Figure 3 are both zero, so if we fix the signal level a3, the signal level a1 becomes a3. When they are equal, it is minimum.

At this time, there is a1/a3 between signal levels a□ and a3.
There is a relationship as follows: =1+(t2+t4)/11. If the attenuation cover of the variable attenuator is adjusted so that the average absolute value of the amplitude is minimized, the measurement error will increase by the second term in the above equation. Therefore, in order to reduce the error, it is necessary to reduce the idle time ■1, and especially under the condition that the idle time t2-t4=0, the signal level a1a3 when tl-t3=T/2
The average amplitude for different cases is the maximum. Therefore, Figure 4 (
b) The signal is good.

(3) Input the received output signal and a sine wave signal of the same period to a multiplier, take the product, and multiply by the @flow signal component with a level proportional to the amplitude of the fundamental signal component that meets the received output signal. The third signal processing method is to extract the signal from the output signal of the device using a filter. Then, as in (1) and (2) above, the attenuation amount of the variable attenuator is adjusted so that the absolute value of the level of the DC signal is minimized. This signal processing method is also explained in the 4th section.
The signal shown in Figure (b) is preferred. This is due to the following reason. The level of the low frequency signal is proportional to the product of the received output signal and the sine wave signal, that is, in the example of the third section, t□==13.1
□+I T -(t2+t, 1o)=Σ It becomes maximum, so considering this case, the time difference t between the time at the midpoint of idle time t2 or t4 in the received output signal. The low frequency signal level included in the product of the received output signal and a sine wave signal having a phase difference corresponding to the time difference t. When is zero, the two signal levels a□ and a3 are equal, and the sum is zero. Generally, free time t2t4, time t. It is advantageous for T to be shorter than the period T. In such a case, when the low frequency signal level is zero, there is approximately the following relationship between the key signal levels a 1 a 3 .

π(to-t2) 2πtO a1/B = l + 11-T This second term becomes a measurement error, but if to-0 and tl-t2, this second term disappears. Furthermore, in the case of sacrum level a1 and arrow a3, it is desirable that the conditions for the maximum low frequency level to be satisfied at each time are tl - t3 - Σ, t2 - t4 = 0, to = o, (4) The AC signal component is extracted from the received output signal using a filter, and the AC signal component is extracted from the received output signal. The fourth signal processing method is to input the signal component as two input signals to a multiplier, and extract a blood flow signal at a level proportional to the power of the AC signal component from the output of the multiplier (i) using a filter. Also in this signal processing method, the attenuation amount of the variable attenuator is adjusted so that the absolute value of the level of the DC signal is minimized.
The average relevel of the signal, which is proportional to the square of the alternating current component in the received output signal shown in the figure, is minimized when the following relationship exists.

al/a ==l + 02 ” tJ/11 The second term in this equation is illll1 foot error, so the free time is 12.1
4 needs to be as short as possible. time 12=1
4=0, the average level in the case of level 13 aINa3 becomes maximum when t1='a=T/2Q).

The four types of signal processing methods described above treat two signals that repeat alternately in time as one alternating current signal, as shown in Figure 4(b). It detects level differences. Therefore, if it is possible to determine the presence or absence of the signal bh, there is no need to separate and compare the two signals as shown in FIG. As mentioned above, in such a signal processing method, using a received output signal sound similar to the waveform shown in FIG. 4(b) is effective in reducing measurement errors. When measuring the circuit of the embodiment shown in FIG. 2, the idle time between the rectangular pulse signal transmitted on the reference transmission line L0 and the rectangular pulse signal transmitted on the measured transmission line LX located immediately after it,
In order to equalize the idle time between the rectangular pulse signal transmitted through the transmission line under test LX and the rectangular pulse signal transmitted through the next reference transmission line Lo, the cycle of the output signal of the signal source SG is used as a reference. transmission path. It may be twice the transmission delay time between LX and the transmission line under test LX. Furthermore, in order to eliminate idle time, the duration of the rectangular pulse signal may be set to 172 of the above period. As a result, the received output signal shown in FIG. 4(b) can be obtained.

(Configuration Example of Signal Processing Control Unit SPC) Four examples of signal processing methods in the signal processing control SPC have been described above, and now an example of a circuit for performing this signal processing will be described. FIG. 5 shows the signal source SG, receiver 1c, variable attenuator VA, and signal processing ft1lf controller SPC shown in FIG. A sine wave signal component of the fundamental period is extracted with a filter, a DC signal with a level corresponding to the amplitude of this sine wave signal component is created, and the variable attenuator VA is attenuated so that the absolute value of the level of this DC signal is minimized. This is an example in which all signals or instructions for adjusting the device are output, that is, the configuration is based on the signal processing method (1) described above.

In FIG. 5, the output of the receiver RFC (ill?B
It is connected to the input side of the pass-pass filter BPF and also to the input side of the waveform monitoring unit WFM. The output of the band pass filter BPF (till) is connected to the detector DETK via the amplifier A, and is further connected to the determiner DICK via the amplifier Ask.The output side of the detector DET is connected to the drive unit via the amplifier A2k. Connected to DRV.

Also, the output side of the determiner DIC is DRIVE! 1. Connected to the cape terminal of the h capital DRY. The output side of the drive unit DRY is connected to a variable attenuator VA.

The waveform monitoring unit WFM is connected to the variable synchronous signal generator VCGK, and the variable 1llii+/4' pulse generator VWPG.
and a variable delay circuit VDC. The variable width pulse generator VWPG is connected to the variable synchronizing signal generator VCG and to the signal source SG1, and also to the variable delay circuit IA? r VDC is connected to the variable synchronization signal generator VCG and also to the determiner DIC. At this time, the bandpass filter BPF extracts the sine wave signal component of the synchronization width from the received output signal. , the reference transmission line is designed to make it possible to perform measurements by replacing the transmission line Lx to be measured in various ways. If the transmission delay time difference between

Since it is necessary to change the period of the signal component to be extracted, it is necessary to change the frequency band 1, overpass filter, and I4 (variable overband, or use several filters with appropriate passbands, and replace them by switching them with switches, etc.). Amplifier A
, A2A, can be used as much as necessary, and a part of the output of the high-J amplifier A is amplified by the amplifier A3. However, it is acceptable to increase the output μ of the device A9 by 1.5, adjust the output of the bandpass filter BPF of the detector DET and output a signal corresponding to the amplitude of the L fundamental wave component. However, this output signal does not necessarily have to be proportional to the amplitude of the fundamental wave, and it is sufficient that it changes almost immediately in response to changes in the amplitude. Ushida, judge 1) I C
416 from the band pass filter BPF is determined by the drive unit, which determines whether the signal No. 416 is positive or negative from the band pass filter BPF. It is sent to LIRV. In other words, if there is a level difference between the two signals transmitted through the reference transmission line Lo and the measured transmission line LX and reaching the receiver RFC, the determiner D The sine wave signal component of the period has a certain value other than 0, and the phase of the sine wave signal component differs by +80 depending on which signal level is higher, so the signal level of which transmission line is determined by the judgment result of judgment i!DIc. It can be determined whether the drive unit D RV is large or not.
is the drive part of the variable attenuator VA, which attenuates the low frequency signal of the detector DET amplified by the amplifier A2 and the output signal which is the determination result of the -tlj regulator 1) IC. The attenuation amount of the variable attenuation table A is adjusted by the adjustment step [<1 and its sign is determined, h so that the output of the detector DET becomes zero]. As an example of this drive unit DRV, the outputs of the determiner DIC and the amplifier A2 are displayed,
The attenuation amount of the variable attenuator VA(7) may be adjusted manually according to this display. Furthermore, as a modification of this configuration example, it is also possible to operate the drive unit 1) RV only with the output of the determiner DIC and adjust the attenuation amount so that the output of the determiner DIC becomes zero. In addition, since the object to be measured is the original transmission line, a thin gold film 'fc' is applied to a glass disk as a variable attenuator VA.
In the case of using a vapor-deposited material, it is possible to use a servo mechanism to rotate the glass disk according to the output of the judge DIC and the amplifier A2. ■The same thing can be considered when using as A.

The waveform monitoring unit WFM connected to the receiver RFC has two transmission paths with different transmission delay times. , Lx, the difference in reception time of the pulse signals transmitted, that is, the difference in transmission delay time, is calculated by referring to the synchronization signal from the OT variation synchronization signal source VCG.
I'll take it. Therefore, the waveform monitoring unit WFM measures the difference in arrival time between two pulse conditions and outputs it as a signal or an instruction.Anything can be used, for example, the output of a pulse generator that oscillates at a constant frequency. Using a digital counter, start counting with the first pulse signal that arrives, and end the lr number with the L 2 flW +th pulse signal, and compare the -m period of the pulse of the pulse A generator with the number of counted pulses. An example of calculating the transmission delay time difference is given below. The measurement piece of the transmission delay time difference of the waveform control part 1 WFM is returned to the variable synchronization signal generator VCG, and the period of IUI M (No. 5 is set), and the input signal to the receiver RE C is
So that the waveform shown in figure (b) is obtained = +B width pulse pulser ■
The output pulse width of the PG is set, and the output of the variable synchronizing signal generator VCG is transmitted to the discriminator DIC every time the pulse signal transmitted through the reference transmission line reaches the discriminator DIC. In particular, it is used to adjust the delay time m of the variable delay circuit VDC.

Note that the function of the variable delay circuit VDC can be performed during the function of the determiner DIC or the variable synchronization signal generator VCG. Here, the variable synchronization signal generator 6VCG is connected to either transmission path. Any oscillator may be used as long as it is operated to generate a synchronizing signal with a cycle sufficiently longer than the transmission delay time of the LX, and the oscillation cycle can be adjusted by inputting an analog signal or digital signal, or by manual operation. do not have. In addition, the variable width pulse generator VWPG is
It synchronizes with the signal from the DJ variable sync signal generator VCG and generates a pulse with a width sufficiently shorter than the transmission delay time difference between the two transmission lines.The pulse width is adjusted by the same means as the rsJ variable sync signal generator VCG. Any device may be used as long as it can generate a pulse signal in accordance with the input synchronization signal.

The variable delay circuit VDC is a generator VCG.

Any device similar to VWPG that can adjust the delay time of the pulse signal may be used, or it may be something like a delay line that delays the signal, or it may be possible to regenerate the pulse signal using two monostable multivibrators. It may be something that causes it to occur.

FIG. 6 shows an example of a signal processing control section sPc for performing signal processing similar to that shown in FIG. In FIG. 6, CP is the central control unit 1, which is, for example, a microprocessor, vanilla/computer, etc. equipped with an innoturface for sending and receiving signals. The bandpass filter BPF, detector DET, and drive unit DRV may be the same as those shown in FIG. The waveform monitoring unit WFM can be realized, for example, in a timer using a digital counter and a pulse generator that oscillates at a constant frequency. Here, it is sufficient to count the number of pulses generated between the times when the two pulse signals arrive and perform an appropriate conversion. As the signal generator 1fflVcG, any oscillator whose oscillation period can be adjusted by inputting an analog signal or digital signal may be used. Further, the variable width pulse generator VWPG generates a pulse signal according to the input synchronization signal, and any device that can set the pulse width by inputting the same signal as the variable synchronization signal generator VCG is suitable.

Receiver RECO receiver 1g output signal band pass filter BP
When Ii' is input to the waveform monitoring unit WFM, the bandpass filter BPF extracts the fundamental wave 1g component from the received output signal. This fundamental wave signal component is amplified by the amplifier A1, and then a low frequency signal corresponding to the amplitude of the d component is detected by the detector 6DET. Central processing unit C
At P, the attenuation of the variable attenuator VA is adjusted based on this low frequency signal 1h via the drive unit f) RV. The measurement procedure is to first increase the attenuation of the variable attenuator VA slightly when the output signal level of amplifier A2 exceeds a certain criterion, and based on this, when the output signal level of amplifier A2 decreases. The attenuation amount is increased by an appropriate amount corresponding to the output signal level of amplifier A2, and conversely, when the attenuation amount is slightly increased, as the signal level of amplifier A2 increases, the attenuation amount is decreased by an appropriate amount.
The same operation is repeated until the output signal level of becomes below the determination standard. The characteristics of the transmission line to be measured are known from the final attenuation amount at this time and the known characteristics of the measurement system other than the transmission line to be measured.

On the other hand, the waveform monitoring section WF'M connected to the bandpass filter BPF performs an auxiliary operation in order to make the received output signal as close as possible to the waveform shown in FIG. 3(b) to be suitable for this attenuation amount adjustment method. That is, the central processing unit CP first sends a command to the variable synchronization signal generator VCG to generate a synchronization signal having a cycle sufficiently longer than the transmission delay time of both transmission lines.

At the same time, the central processing unit CP generates an i11 variable width pulse g=vw
pc, here a pulse with an extremely narrow width] is generated in synchronization with the synchronization signal from the variable synchronization signal generator V C:G. The signal source SG generates a short pulse signal in accordance with the long period short pulse generated by the variable width pulse generator VWPG. This signal is transmitted through each transmission line LXLo [
7, the pulse signals are received by the receiver RFC as two pulse signals separated by the difference in their transmission delay times, and further sent to the waveform monitoring unit WFM. The waveform monitoring unit WFM is the central processing unit CP.
The arrival time difference between the two pulse signals is measured according to the command, and the result is sent to the central processing unit CP. Based on this result, the central processing unit CP sends a command to the univariate period signal generator VCG and the variable width pulse generator 6VWPG, respectively, to delay the pulse width by setting the period of the synchronization signal to twice the delay time difference. Set equal to the time difference. In this way, the ideal received output signal shown in FIG. 4(b>) is obtained.

A signal processing method corresponding to the above-mentioned (2), that is, extracting AC signal components from the received output signal using a filter,
The signal processing control unit obtains a DC signal at a level corresponding to the average amplitude part of the AC signal component and adjusts the attenuator of the variable attenuator VA so that the absolute value of the level of this blood flow signal is minimized. The ship is clear. As this signal processing control unit SPC, in the configuration example 7 shown in FIGS. 5 and 6, a high-pass filter that blocks only the DC component or a high-pass filter that blocks only the DC component or a high-pass filter that blocks the DC component and unnecessary high frequency components is used instead of the bandpass filter BPFO. An example may be a band-pass filter to remove the filter. 7 Executing the signal processing method of (1) mentioned above 1
No. 5 processing control unit spc <Fig. 5, Fig. 6) and this (2
) Signal processing 11i1J Obe SP that executes the signal processing method of
The differences from C are as follows. In other words, in the signal processing method of tl), it is necessary to completely cut off the second wave of the fundamental frequency of the received output signal, which is determined by the difference in transmission delay time between the transmission line under test, the reference, and the transmission line. The range of difference in image transmission path length that can be handled by the bandpass filter BPF is 7.
Each is less than one octave. Therefore, in (1), in order to make measurements that correspond to a wide range of transmission path length differences, it is necessary to prepare a plurality of filters with different passbands and use them by switching them with a switch or by replacing them. On the other hand, in the signal processing method (2), in principle, one band-pass filter can deal with any difference in transmission path length.

In signal processing method (1), even if there is some idle time in the received output signal, the effect of this can be reduced by a filter, but in signal processing method (2), this idle time directly affects measurement accuracy.

Figure 7 shows the third 9! which is the signal processing method (3) mentioned above.
l * In other words, input the received output signal and a sine wave signal of the same period to a multiplier to create a product, and calculate the received output signal and the level proportional to the amplitude of the included fundamental signal component. The signal processing control unit SPC extracts the DC signal component from the output of the tll 'p-device with a filter and adjusts the attenuation amount of the variable attenuator VA so that the absolute value of the level of this DC No. 1g becomes the minimum. ing. In Figure 7, HP
F is a high-pass filter that cuts off the 19. original signal in the output signal, and p%PRD is a multiplier that outputs a signal proportional to the product of two input signals.Also, LP
F is a low-pass filter, and CRL is an attenuation control section for the variable attenuator VA. s.

Oscillates in synchronization with the human power signal and outputs a sine wave signal 1
The iNJ phase oscillator, VPS, is a "shifting incest" that changes the phase of the sine wave signal.

In preparation for the actual division of 111+1, the waveform monitoring unit WFM,
Controller number generator VCG, variable width pulse generator V
The transmission delay time difference between the two transmission paths is measured using WPG, and the output pulse width of the synchronization signal generator VCG and the output pulse width of the vibration amplitude pulse generator VWPG is twice and once the above time difference, respectively. 1 similar to Figure 4(b) as
The waveform should be as follows.

Next, a high-pass filter l (PF) removes the DC component from the received output signal output from the receiver REC, and the amplifier A1 amplifies the signal and inputs it to the multiplier PRD. The other input to the oscillator PRD is the output of the synchronization signal generator VCG as the synchronous oscillation R'is o vc large input, and the phase of the sine wave No. 18 from this oscillator 80 is input to the variable phase shifter vPS. Multiplier PRD
When all DC components are extracted from the output using a low-pass filter LPF, a signal 1d having a level proportional to the amplitude of the fundamental wave can of the received output signal is obtained. The phase shift amount a of the variable phase shifter VPs is adjusted so that the output of the phase shifter PS and the output of the amplifier A1 are in phase or in opposite phases, and the absolute value of the level of the blood flow signal is maximized. do. In this signal processing method, if the phase relationship between the two inputs of the multiplier PRD is maintained, it can be determined which transmission path the signal level transmitted through is higher based on the iM multiplication signal code. Therefore, with reference to the level and sign of DC No. 1g amplified by amplifier A2, the attenuation amount of the variable attenuator VA is adjusted by the attenuation sound control unit CRL so that the absolute value of this signal level is minimized. be able to.

FIG. 8 is a configuration example of a signal processing control unit SPC for executing the signal processing method (3), similar to FIG. 7.

In FIG. 8, in addition to VDC, DRV, and CP: 1ift 5V, which is similar to the configuration example in FIG. 7, is shown. Here, DRV is a drive unit that adjusts the attenuation amount of the n1 variable attenuator VA, and VDC is a pl variable delay circuit that appropriately delays the output of CG and transmits it to the synchronous oscillator SO. CP is a central processing unit that transmits and receives information between each circuit and controls these operations.

In the example shown in FIG. 7, the variable phase shifter PS is used, but in the example shown in FIG.
c- is used to synchronize the synchronous oscillator SO. 1. In the example shown in FIG. 8, all operations are performed by the central processing unit CP. Although these points differ from the example shown in FIG. 7, the operating procedure and the functions of each component are the same.

In this way, in the 1' signal processing control unit SPC shown in FIGS. 7 and 8, in principle, one high-pass filter RPF and one low-pass filter LPF have a transmission delay time difference with respect to the reference transmission path other than $. It is possible to perform measurements on 1Ii11 transmission lines. Moreover, the area-cutting filter H, P F k
Direct conversion using a bandpass filter with an appropriate band, and multiplier P
It is also possible to remove the unnecessary frequency I3S1 from the input signal of RD-\.

The above-mentioned signal processing method (4) is executed. A signal is generated by a multiplier, and the attenuation amount of the variable attenuator VA is adjusted so that the absolute value of the 11 current signal at a level proportional to the power of the AC signal component extracted by a filter from the output signal from the multiplier is minimized. As an example of the configuration of the signal processing unit SPC, in FIGS. 7 and 8, the variable phase shifter V
It is better to remove the PS, OJ variable delay circuit VDC1 synchronous oscillator SO, and divide the output signal of the high-pass filter HRF into two to create a two-manufactured signal of 5G6PRD. In this case, it is not possible to determine which transmission line has the higher level of the signal transmitted through only the Jt-'7' output signal of the low-pass filter LPF. It is necessary to determine whether changing the attenuation amount in either direction will reduce the output of the low-pass filter LPF.

From Fig. 5 to Fig. 8 (in the g processing control unit SPC, the adjustment of the amount of attenuation of the variable attenuator or its direction is ultimately determined based on the level of the low frequency signal that can be regarded as almost direct current. .For this reason.

Offsets and fluctuations thereof in the DC signal processing elements after the detector DET or the LSI calculator PRO affect measurement accuracy. However, since neither the offset nor its fluctuation poses a problem at all in the processing stage before that, if the signal is sufficiently amplified in this stage, problems related to the DC level in the subsequent stage can be alleviated. At the same time, the parts that handle these AC signals have a superior dynamic range compared to processing methods that handle DC levels. Furthermore, in all signal processing control sections, variations in amplifier gain and filter attenuation,
and the nonlinearity of the multiplier does not directly affect the measurement error,
Furthermore, since the above embodiment uses the ratio @1lil constant method, the characteristic fluctuations of the signal SG and the receiver REC are reduced by the comparison process.

FIG. 9 is an example corresponding to FIG. 2, but IsL.

15L2 are isolators, and I and a are adder transmission lines. Isolator l5L1. l5L2 transmits all signals with low loss only in the direction of the arrow in the figure, and prevents deterioration of measurement axis due to reflection from each component on the signal path or signal leakage between two transmission paths. . - As an example, an isolator that fully utilizes the so-called Faraday rotation may be used for both electrical and optical signals. The additional transmission line La has known characteristics and plays the role of adjusting the transmission delay time.

In other words, the transmission delay time of the additional transmission line La is
By making it longer than that of O, it is possible to measure the characteristics of a transmission line LX to be measured of any length.

Furthermore, if the difference between the transmission delay intervals is made sufficiently large, the period of the received output signal will become longer, so the signal processing control unit SPC
As such, one that can process low frequency signals is sufficient. Phrasal addition transmission line 1. As a, it is sufficient that it is the same as that of the reference transmission line LO1 and the transmission line under test LX, but it is not necessary to be exactly the same.

In particular, when the defined transmission paths I and x are multimode transmission paths, the secondary transmission path 'la is provided with the function of a mode scrubber in addition to the delay function. Additionally, additional transmission line la and isolator l5L1. It is not necessary to use it at the same time as l5L2.

No. 10-1 is an embodiment targeted at the original transmission line, and the rest is the same except for the divider shown in FIG.

Here, the signal source SG has the same output signal as that of the embodiment shown in FIG. 2, but some functions are different from that of the signal source SG. This signal source SG is indicated by the broken line in FIG. In FIG. 11, LAM is the laser active medium, EX is the excitation part, and MR1
MR2 is a semi-transparent mirror, and these constitute a laser oscillator.

Also.

L1L2 is a lens system, semi-transparent, MR11VLR2
Four people direct the laser beams emitted from the reference transmission line LO and the defined transmission lines I and x, respectively. The laser may be of any kind, such as a semi-dedicated laser or a solid-state laser, and the reflecting mirror constituting the resonator may have three cylindrical tops, or may be of a type such as a lino laser.

As the coupler C shown in FIG. 10, polarizing prisms etc. described in FIG. 2 may be used, but if the coupler shown in FIG. can be configured. In Fig. 12, L1L2 is a lens system such as a distributed refractive index lens, and in the light receiving element PD, the output light from the variable attenuator VA and the transmission line under test Lx passes through the lens system and follows L2 to its light receiving surface. The light is focused on the top. On the light receiving surface, by adjusting the angles formed by each light beam condensed on the light receiving surface and the slope of the light receiving surface so that they are not on the same plane, leakage of signals between the two transmission paths can be reduced. Further, as the coupler C, the light emitted from the end of the original fiber may be directly irradiated onto the light receiving surface without using the lens system L1L2.

13 has the same functions as the embodiment shown in FIG. 9, but has a configuration in which an additional transmission line La and isolators ISL, ISL, 15L2 are added to the configuration shown in FIG.

FIG. 14 shows an example in which signals transmitted through two transmission paths are switched by a switch SW and received alternately. Although the signal source SG may generate a rectangular pulse-like signal, it is preferable that the signal source SG generates a continuous signal. This continuous signal includes a single current, an unmodulated or modulated alternating current signal, an unmodulated or modulated continuous optical signal, and the like. switch S
W alternately and periodically transmits the output signal of the signal source SG transmitted through each transmission path to the receiver REC in accordance with a command from the signal processing controller SPC.

Therefore, the output signal of the signal source SG is a series of 8 signals or a synchronous rectangular pulse-like signal synchronized with the switch SW,
These signals are simultaneously sent to the transmission line under test Lx and the reference transmission line Iio via the divider. The signal processing control unit SPC controls at least one of the AC signal component and the fundamental wave component of the periodic reception signal output by the receiver RFC.

Creates a DC signal with a level corresponding to the amplitude or power,
A necessary signal or instruction for adjusting the amount of attenuation of the variable attenuator VA is output so that the absolute value of this blood flow signal level is minimized. In this way, the variable attenuation and the transmission line under test Lx
, 51, the characteristics of the transmission line to be measured can be obtained from the known characteristics of each component other than 51. Signal processing control unit SPC
As shown in Fig. 15 to Fig. 17 (h example can be opened. Fig. 15 is a configuration example corresponding to Fig. 5. , DC is a delay circuit.

Variable synchronizing signal generator VCG%o, unlike the one in Figure 5.
J variable width pulse amplitude device VWP G, blind variable delay circuit VDC
may have a fixed function, and the reception output signal is made into a periodic signal by switching the switch SW. Figure 16 and 1
Even in the circuit shown in Fig. 7, it is sufficient to have a fixed function including the phase shifter PS, as in Fig. 15, and the waveform monitoring unit WFM shown in Figs. 6 and 7 is no longer necessary. The operation is also unnecessary. As for the switch SW, when there is a fluctuation in the loss that the signal passing through it receives.

d) 11 Since it directly affects the constant accuracy, it is necessary to use one with little variation.

FIG. 18 is an example in which a switch is used on the receiving side like in FIG. 14, but like the example shown in FIG.
．． It has a configuration in which 15L2 and an additional transmission line La are added.

Figure 19 is an example in which a switch is used on the receiving side as in Figure 14, but by placing the signal source SG shown in Figure 14 and official seal 1 with the signal source shown in Figure 10, This is an example of a configuration in which signals are sent directly from a signal source to two transmission lines, and the operation and function are similar to those in FIG. 16.

Figure 20 shows the 61) example shown in Figure 19.
5L1. An example is shown in which 15L2 and the transmission line La are added, and in this case, the f#:W device VA is placed on the side of the transmission line under test LX.

FIG. 21 shows an example in which the output 1a' of the signal source SG is alternately and periodically sent to the reference transmission line LO and the constant transmission lines I and x using a switch.

This example is the same as the example shown in FIG. 14, except that the switch SW is placed on the transmitting side. Output from the 1st number processing control unit SPC → Switch S for the i4 Reigo number
W is the output signal of the signal source SG to the transmission line under test Lx and the reference transmission line 1. o and periodically. The segments that have followed the respective transmission paths are received by the coupler C and both are received by the receiver REC. A blood flow signal with a level corresponding to the amplitude or vehicle force of at least one of the AC signal component or the fundamental wave component in the received output signal of the receiver REC is created, and the absolute fli of the level of this countercurrent signal is minimized. The 1H processing control unit SPC outputs the 1st number or instruction for adjusting the attenuation sound of the simulator VA to adjust the attenuation sound. Attenuation amount of variable attenuator VA after adjustment and transmission line Lx, IJ
Measures the strength of the transmission line under test from known characteristics. The output signal of the signal source SG is an unmodulated or modulated alternating current signal or blood flow signal, and is preferably a continuous signal.

As for the signal processing control section SPC, in the configuration examples shown in FIGS. 5 to 8, the waveform monitoring section WFM and associated operations are excluded, and the switch SW is activated by the output signal of the n1 variable width pulse generator VWPG. A driving example is provided. In this case, the variable width pulse generator VWPG and the variable synchronizing signal generator VCG may have fixed functions, but the variable phase shifter VPS,
Considering that the length of the transmission line LX to be measured varies, it is desirable that the variable delay circuit VDC has a variable function.

Similar to the example shown in FIG. 9, FIG. 22 shows the example of FIG. 21 with one addition JLa and isolator ISI, □.

An example in which IS and 2 are added is shown.

In the above-mentioned implementation 11, there are three configurations: ■ a configuration that does not use a switch, ■ a configuration that uses a switch on the receiving side (A configuration), and ■ a configuration that uses a switch on the transmitting side.
A configuration using switches on both the B side and the receiver 1g side is also possible. In the h4 configuration (2), the received output signal is strongly constrained by the two-time difference in the transmission series of the two transmission lines, and the passage plate requires a variable filter or a filter with a different complexity. ■ILD
Instead of requiring a switch of configuration f161, the period of the incoming key signal can be arbitrarily set by the switching operation of the switch, and a fixed filter can be used to cope with the transmission line Lx of abnormal length. The structure G) has an intermediate feature between the structures q) and ■. It is only necessary to decide which configuration of 1IjjL to use depending on the purpose of use. for example,
When measuring the characteristics of one transmission line under test over a long period of time or repeatedly, changes in the pass frequency band of the filter will be diminished.
When it'll be a fixed target, the other configurations (2) and (2) are suitable. In addition.

Since it is difficult to maintain the characteristics of the switch SW constant over a long period of time or in response to changes in the surrounding environment, the fewer the number of switches, the better. Furthermore, if a signal delay mechanism corresponding to the additional transmission path is prepared in the configuration q), it can be used as a comparative measurement method for various physical quantities.

As explained above, the present invention uses fewer switches or no switches at all than the conventional method, so it is possible to perform more accurate and stable measurements, and it is possible to perform signal processing as an alternating current signal. Because of this, it is easily affected by fluctuations in the DC level, and it also has great effects such as simplifying the configuration of the measurement system.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an example of a conventional comparative measurement method;
Figures 22 to 22 show examples of the comparative measurement method of the present invention,
Figure 2 is a block diagram of an example without a switch, Figure 3 (a)
(b) is a waveform diagram of an example of the received output signal waveform;
a) (b) (e) are waveform diagrams of the receiver 1g output signal suitable for implementation, Figures 5 to 8 are block diagrams showing four examples of the signal processing control section, and Figure 9 is a diagram showing other examples without a switch. FIG. 10 is a block diagram of another embodiment without a switch. FIG. 11 is a block diagram of an example of the signal source used in FIG. 10. FIG. 12 is a block diagram of an example of a coupler. FIG. 13 is a block diagram of yet another embodiment without a switch,
Fig. 14 is a block diagram of an example with a switch on the receiving side, Figs. 15 to 17 are block diagrams of three examples of the signal processing control section shown in Fig. 14, and Fig. 18 is a block diagram of an example with a switch on the receiving side. Block diagrams of other examples with FIGS. 19 and 2
FIG. 21 is a block diagram showing two examples in which a switch is provided on the receiving side; FIG. 22 is a block diagram showing two examples in which a switch is provided on the transmitting side. In the figure, AlA2A3 is an amplifier 1lIiii8. BPF is a band pass filter. C is a coupler. ACG and CG are synchronous signal generators. COMP is a comparator, and CP is a central processing unit. CRL is the control section of the range table, DDID2 is the divider, ADC and DC are the delay circuits, and DET is the detector. 1) IC is a judge. DRV is the drive unit. Ex is an excitation part, l5L1. l5L2 is Ainrater. L1L2 is the Reno's thread, La is the +1 addition transmission line, and LO is the reference transmission line. LX is the transmission line under test, LD is the laser diode, and LPF is the low-pass filter. MRI M R2 is a semi-transparent mirror. PD is a photodetector, PGU is a pulse generator. PRD is a multiplier. PS is a phase shifter. RFC is a transmission device, and SG is a signal source.

Claims (8)

[Claims] (1) Send the signal from the signal source to the transmission line under test and the reference transmission line, and receive the signals from these transmission lines with a receiver that has one receiving element and outputs a baseband reception signal. In a measurement system having a signal processing system that outputs a DC signal having a level corresponding to the amplitude or power of at least one of an AC signal component or a fundamental wave signal component included in a periodic signal from a receiver, the above-mentioned transmission path to be measured. and a reference transmission line, and a re-variable attenuator is connected to at least one of the two transmission lines, and the signals from the two transmission lines are made different in arrival time to the receiver through the measurement target transmission line and the reference transmission line, respectively. The signal is received alternately and periodically by the single receiver, and the absolute value of the level of the DC signal obtained by the signal processing system corresponding to the periodic signal output by the single receiver is the minimum. A comparative measurement characterized in that the attenuation of the variable attenuator is adjusted as follows, and the transmission line under test is measured from the adjusted attenuation amount and the characteristics of the measurement system other than the transmission line under test. method. (2) The signal source periodically generates a rectangular pulse signal No. 111, sends this rectangular pulse signal to the reference transmission line and the measured transmission line, and adjusts the duration and generation cycle of the rectangular pulse signal. At the same time, the signal transmission times of the two transmission paths are different so that the rectangular pulse-like signals that do not overlap in time are received by a receiver, and the output of the receiver is made into a periodic signal. A comparative measurement method according to claim 1. (3) The signal from the signal source is sent to the reference transmission line and the transmission line under test at the same time, and the signal passing through these two transmission lines is 2
Each input terminal is input to each input terminal of a switch that has seven input terminals, and when this switch is activated, one
The signals from the two transmission paths are alternately and periodically inputted to the receiver from the output terminals of the receiver, and the output of the receiver is periodically
The comparative measurement method according to claim 1, characterized in that it is No. u. (4) Input the signal from the signal source into one input terminal of the switch, operate this switch, and periodically send the above signal alternately to the reference transmission line and the transmission line under test connected to the two output terminals. The signals from these two transmission lines are
The comparative measuring method according to claim 1, characterized in that a periodic output signal is obtained by receiving the signal with a plurality of receivers. (5) The 1* processing system extracts a sine wave signal component having the same period as this signal from the periodic signal output by the receiver using a filter, and generates a DC signal having a level corresponding to the amplitude of this sine wave signal component. A comparative measurement method according to claim 1, 2, or 3, characterized in that the method outputs . (6) The signal processing system is characterized in that the AC signal component is extracted from the periodic signal output by the receiver using a filter, and a DC signal having a level corresponding to the average amplitude of this AC signal component is output. A comparative measurement method according to claim 1, 2, or 3. (7) The signal processing system inputs the periodic signal output by the receiver and the sine wave signal with the same period as this signal into a multiplier to calculate the product, and then calculates the product by [from the output signal of the receiver] Claims 1, 2, or 2, characterized in that a DC signal with a level proportional to the amplitude of the fundamental wave 1^- component encountered in the received signal is extracted and outputted using a filter. Comparative measurement method described in Section 3. (8) The signal processing system uses a filter to extract the current signal component from the periodic 1g signal output by the receiver, uses this AC signal component as two input signals to the multiplier, multiplies it by Claims 1 and 2 are characterized by outputting a DC signal having a level proportional to the power of the AC signal component extracted by a filter from the output signal of the calculator.
Or the comparative measurement method described in Section 3.