Displacement measurement system

Abstract

The system allows for the measurement of the position of the second transmission line relative to the first transmission line, while keeping the immovable and movable structures separate. [Solution] The displacement measuring system includes a first transmission line having a first end and a second end, the first end being mismatched and the second end being connected to a signal source; a second transmission line having a third end and a fourth end, facing the first transmission line and being relatively movable; and a phase difference detection means for detecting the phase difference between the signal at the third end of the second transmission line and the signal at the fourth end of the second transmission line.

Description

[Technical Field]

[0001] This disclosure relates to a displacement measurement system. [Background technology]

[0002] In recent years, systems for measuring the displacement of detectors that move non-contact along transmission lines have been researched and developed. For example, Non-Patent Document 1 discloses a system that generates standing waves in a transmission line, acquires the amplitude level and phase of the standing waves with a detector, and measures the displacement of the detector on the transmission line. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] IEEE Sensors Journal, Volume 23, No.16, 15 August 2023, P.18609 - 18623 "A Wide-Range Transmission Line-Based Linear Displacement Sensor" [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The system described in Non-Patent Document 1 detects the amplitude and phase of a standing wave generated on a transmission line using an antenna that moves while facing the transmission line, and estimates the displacement amount of the moving antenna from those values. In order to detect the amplitude and phase of the standing wave, the signal output by the antenna is input to a quadrature detector. As a reference frequency (phase) source for the quadrature detector, it is essential to supply a signal source whose phase and frequency do not both change due to displacement. Therefore, a coaxial cable, which is not specified, supplies the reference frequency (phase) signal to the quadrature detector. A supply path for the reference frequency (phase) signal such as the aforementioned coaxial cable is essential, and it is impossible to completely separate the non-moving structure and the moving structure. There is a problem in that it cannot be applied to a system in which the moving structure rotates infinitely along a circular transmission line.

[0005] An object of the present disclosure is to be able to measure the position of a second transmission line with respect to a first transmission line while separating a non-moving structure and a moving structure.

Means for Solving the Problems

[0006] A displacement measurement system includes a first transmission line having a first end and a second end, the first end being terminated in an unmatched manner and the second end being connected to a signal source, and a third end and a fourth end. A second transmission line that is relatively movable while facing the first transmission line, and a phase difference detection means for detecting the phase difference between the signal at the third end of the second transmission line and the signal at the fourth end of the second transmission line.

Effects of the Invention

[0007] According to the present disclosure, it is possible to measure the position of a second transmission line with respect to a first transmission line while separating a non-moving structure and a moving structure.

Brief Description of the Drawings

[0008] [Figure 1] It is a diagram of opposing transmission lines according to the first embodiment. [Figure 2]It is a diagram of an analysis model according to the first embodiment. [Figure 3] It is a diagram showing the analysis result of the transmission characteristics (S31, S41) according to the first embodiment. [Figure 4] It is a diagram explaining the physical and mathematical principle according to the first embodiment. [Figure 5] It is a diagram in which a phase difference detector is introduced with respect to FIG. 1 according to the first embodiment. [Figure 6] It is a diagram showing an example in which the transmission line is open-terminated according to the first embodiment. [Figure 7] It is a diagram showing an example in which the transmission line is short-circuited according to the first embodiment. [Figure 8] It is a diagram explaining means for expanding the measurement range according to the first embodiment. [Figure 9] It is a diagram of a system capable of measuring the displacement amount of an antenna that moves in a circular motion according to the second embodiment.

Mode for Carrying Out the Invention

[0009] (First Embodiment) FIG. 1 is a diagram showing a configuration example of a displacement measurement system 100 according to the first embodiment. The displacement measurement system 100 includes a first transmission line 101, a second transmission line 106, a first terminal 102, a second terminal 103, a third terminal 104, and a fourth terminal 105.

[0010] The first transmission line 101 has a characteristic impedance Z o The first terminal 102, the second terminal 103, the third terminal 104, and the fourth terminal 105 are pure resistors each having a resistance value Z o The displacement measurement system 100 performs displacement measurement by using a signal propagated from the first transmission line 101 to the second transmission line 106 with a space therebetween by electric field (capacitance) coupling or magnetic field (inductive coupling), with the relatively long first transmission line 101 facing the relatively short second transmission line 106.

[0011] ​

[0012] The connection point between the first termination 102 and the first transmission line 101 is defined as end port 1.

[0013] The connection point between the second termination 102 and the first transmission line 101 is defined as end port 2.

[0014] The connection point between the third termination 102 and the second transmission line 106 is defined as end port 3.

[0015] The connection point between the fourth termination 102 and the second transmission line 106 is defined as end port 4.

[0016] Port 1 of the first transmission line 101 is connected to the first termination 102. Port 2 of the first transmission line 101 is connected to the second termination 103.

[0017] Port 3 of the second transmission line 106 is connected to the third termination 104. Port 4 of the second transmission line 106 is connected to the fourth termination 105.

[0018] To investigate the ease of energy transfer between each of the end ports, Port1 to Port4, a frequency analysis was performed on the analytical model shown in Figure 2.

[0019] In Figure 2, the analysis model consists of a first transmission line 110 and a second transmission line 113. The first transmission line 110 is a microstrip line constructed on an FR4 substrate with a length of 100 mm and a width of 10 mm, and has a characteristic impedance of 50 Ω.

[0020] The second transmission line 113 is a microstrip line constructed on an FR4 substrate with a length of 20 mm and a width of 10 mm, and has a characteristic impedance of 50 Ω.

[0021] The first transmission line 110 and the second transmission line 113 are each formed on a dielectric substrate (FR4 substrate).

[0022] The first transmission line 110 and the second transmission line 113 face each other with a space of 1 mm between them. The position where they face each other is where the midpoint of the long side of the first transmission line 110 coincides with the midpoint of the long side of the second transmission line 113.

[0023] Here, the end 112 of the first transmission line 110 is defined the same as the end Port 1 described above.

[0024] The end 111 of the first transmission line 110 is defined the same as the end Port 2 described above.

[0025] The end 115 of the second transmission line 113 is defined the same as the end Port 3 described above.

[0026] The end 114 of the second transmission line 113 is defined the same as the end Port 4 described above.

[0027] The first transmission line 110 has a linear first electrode 116 provided on the upper surface of the FR4 substrate and a first ground conductor provided across the entire lower surface of the FR4 substrate. End 112 is one end of the first electrode 116. End 111 is the other end of the first electrode 116.

[0028] The second transmission line 113 has a linear second electrode 117 provided on the lower surface of the FR4 substrate and a second ground conductor provided across the entire upper surface of the FR4 substrate. End 115 is one end of the second electrode 117. End 114 is the other end of the second electrode 117.

[0029] Figure 3 shows the analysis results of the analysis model in Figure 2. Graph 120 shows the energy transfer ratio from end port 2 to end port 3, which is generally expressed as S32. Similarly, graph 121 shows the energy transfer ratio from end port 1 to end port 3, which is generally expressed as S31.

[0030] At frequencies above 5GHz, the difference between S32 in Graph 120 and S31 in Graph 121 is 8dB or more. Furthermore, around 2.25GHz, the difference between S32 in Graph 120 and S31 in Graph 121 is approximately 7dB.

[0031] Up until now, we have focused on the signal energy output to end port 3, but the signal output to end port 4 is exactly the same as the analysis results in Figure 3. That is, Graph 120 is the energy transfer ratio from end port 1 to end port 4, and corresponds to S41. Graph 121 is the energy transfer ratio from end port 2 to end port 4, and corresponds to S42.

[0032] Therefore, in the above frequency band, there is a strong dependency between the direction of the signal traveling along the first transmission line 110 and the signal energy output to the end port 3 or port 4. This property is generally known as a property of directional couplers.

[0033] This embodiment realizes a displacement measurement system 100 by utilizing the above-mentioned properties.

[0034] The principle will be explained using Figure 4 and mathematical formulas. For simplicity, the mathematical explanation will exclude electromagnetic rigor and focus only on the phase and amplitude changes of the propagating signal with respect to distance.

[0035] The displacement measurement system 100 in Figure 4 has a first termination 102 with an output impedance Z, compared to the displacement measurement system 100 in Figure 1. o The signal source 131 has been changed. Also, the second termination 103 has been changed to the termination 132 of impedance Z1.

[0036] The signal source 131 is connected to the end port 1 of the first transmission line 101 and outputs a signal to the end port 1 of the first transmission line 101. The signal source 131 is connected to the characteristic impedance Z of the first transmission line 101. oIt has an output impedance that is approximately equal to that of the first transmission line 101. Termination 132 is connected to end Port 2 of the first transmission line 101.

[0037] The impedance Z1 is the characteristic impedance Z of the first transmission line 101. o Let us assume that this is different. That is, it is shown in Equation 1.

[0038]

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[0039] Port 2 of the first transmission line 101 is mismatchedly terminated by termination 132. Port 1 of the first transmission line 101 is connected to signal source 131.

[0040] Port 2, the end of the first transmission line 101, has the characteristic impedance Z of the first transmission line 101. o It is terminated by a termination 132 having a different combined impedance Z1. The termination 132 is, for example, a reactance element or a reactance network.

[0041] The second transmission line 106 is provided opposite the first transmission line 101 and is movably positioned relative to it. The second transmission line 106 is shorter than the first transmission line 101.

[0042] The first transmission line 101 and the second transmission line 106 each have a straight shape.

[0043] At this time, reflected waves are generated at the connection interface between the termination 132 and the first transmission line 101.

[0044] Now, we define an axis parallel to the extension direction of the first transmission line 101. On this axis, the position corresponding to the end port 1 is defined as coordinate 0. Also, any coordinate on this axis is defined as x.

[0045] The signal at coordinate x on the first transmission line 101 is S 1(x) Let's assume that. S1(x) It is represented by Equation 2.

[0046] [Number]

[0047] Let the signal propagating in the direction from end Port1 to end Port2 (hereinafter referred to as the traveling wave) be S + 1(x) It is shown by Equation 3.

[0048] [Number]

[0049] Let the signal propagating in the direction from end Port2 to end Port1 (hereinafter referred to as the reflected wave) be S - 1(x) It is shown by Equation 4.

[0050] [Number]

[0051] Here, A is the signal amplitude, c is the speed of light, L is the length of the first transmission line 101, γ is the amplitude of the reflection coefficient at the terminal 132, and φ is the phase of the reflection coefficient at the terminal 132.

[0052] For simplicity, it is assumed that the first transmission line 101 is a lossless transmission line. Further, it is assumed that the first transmission line 101 can transmit an electrical signal at the speed of light c.

[0053] In the analysis result of FIG. 3, in the frequency band of 5 GHz or higher, it was explained that the graph 121 has a lower value than the graph 120. That is, in the frequency band of 5 GHz or higher, the signal energy represented by the graph 120 is considered to be an important detection signal.

[0054] Let the coupling coefficient between the first transmission line 101 and the second transmission line 106 be k.

[0055] When the first transmission line 101 and the second transmission line 106 are facing each other such that the position of end port 3 is coordinate d, the main component S of the signal detected at end port 3 is 32(d) This is given by equation 5.

[0056]

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[0057] Hereafter, this state will be described as "the second transmission line 106 is facing the first transmission line 101 at position d."

[0058] Furthermore, if the length of the second transmission line 106 is l, then the main component S of the signal detected at end port 4 is... 41(d) This is given by equation 6.

[0059]

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[0060] Here, in Figure 5, a phase difference detector 141 is introduced.

[0061] The displacement measurement system 100 in Figure 5 is an additional phase difference detector 141 connected to end ports 3 and 4, and a calculation unit 142, compared to the displacement measurement system 100 in Figure 4. The phase difference detector 141 measures the characteristic impedance Z of the second transmission line 106. o It has an input impedance that is approximately equal to that of the second transmission line 106. The phase difference detector 141 detects the signal S at the end Port 3 of the second transmission line 106. 32(d) and the signal S at Port 4, the end of the second transmission line 106 41(d) Phase difference P (d) The phase difference P output by the phase difference detector 141 is detected. (d) This is represented by Equation 7.

[0062]

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[0063] Solving equation 7 for d yields equation 8.

[0064]

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[0065] Here, λ is given by equation 9.

[0066]

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[0067] f is the frequency of the signal output by signal source 131, and λ is the wavelength of the electromagnetic wave of frequency f in a vacuum.

[0068] In Equation 8, φ is the only unknown value.

[0069] Conversely, if φ is known, then the phase difference P (d) By measuring [the value], the position d can be calculated.

[0070] The displacement measurement system 100 in Figure 6 is a diagram in which the termination 132 is changed to an open configuration compared to the displacement measurement system 100 in Figure 5. In Figure 6, the end port 2 of the first transmission line 101 is terminated in an open configuration.

[0071] The displacement measurement system 100 in Figure 7 is a diagram in which the termination 132 is short-circuited compared to the displacement measurement system 100 in Figure 5. In Figure 7, the end port 2 of the first transmission line 101 is short-circuited.

[0072] As shown in Figure 6, when terminal 132 is left open, φ and γ are given by equation 10.

[0073]

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[0074] As shown in Figure 7, when terminal 132 is short-circuited, φ and γ become as given in Equation 11.

[0075]

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[0076] As shown in Figures 6 and 7, by opening or short-circuiting terminal 132, it becomes possible to determine φ with good reproducibility.

[0077] The calculation unit 142 uses equation 8 to calculate the phase difference P detected by the phase difference detector 141. (d) Based on this, the position d of the second transmission line 106 relative to the first transmission line 101 is calculated.

[0078] According to the means of this embodiment, the two signals S output by the second transmission line 106 32(d) and S 41(d) It is possible to estimate the position d using only this. In other words, a displacement measurement system 100 can be realized that can measure the displacement of a movable antenna while keeping the immovable structure and the movable structure separate.

[0079] (Second Embodiment) Figure 8 shows an example of the configuration of the displacement measurement system 100 according to the second embodiment. The displacement measurement system 100 in Figure 8 is the same as the displacement measurement system 100 in Figure 5, but with the addition of a cumulative phase calculation unit 201 and a counting unit 202.

[0080] The counting unit 202 measures the phase difference p detected by the phase difference detector 141. (x) The value n is counted based on this. The cumulative phase calculation unit 201 calculates the phase difference p detected by the phase difference detector. (x) Based on the value n, the cumulative phase difference P (x) Perform the calculation.

[0081] In the second embodiment, we consider Equation 7.

[0082] When using a quadrature detection method as the phase difference detector 141, it is possible to output a unique detection result within the range of 0 to 360 degrees of the phase difference of the input signal. However, when the second transmission line 106 is at position x, as position x increases or decreases, the same detection result will be output periodically accordingly.

[0083] The phase difference detector 141 detects the signal S from end port 3. 32(x) and the signal S of end port 4 41(x) Phase difference p (d) It detects the phase difference p. (x) The same value is repeated over and over with the period specified in equation 12.

[0084]

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[0085] Therefore, simply the phase difference p (x) Simply observing the coordinate system is insufficient to estimate the position x. In particular, when the position x is within the range of Equation 13, the position x becomes unmeasurable.

[0086]

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[0087] Taking into account the practical constraints mentioned above, Equation 7 can be rewritten as Equation 14.

[0088]

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[0089] The counting unit 202 resets the initial value of the internal counter to 0 at a known position x0. Also, when the second transmission line 106 is at the known position x0, the counting unit 202 calculates the phase difference p of the output of the phase difference detector 141. (x) This is stored as the initial phase difference.

[0090] The second transmission line 106 moves along the first transmission line 101, and consequently the output phase difference p of the phase difference detector 141 changes. (x) When the phase difference changes, the counting unit 202 calculates the current phase difference relative to the stored initial phase difference (the output phase difference p of the phase difference detector 141). (x) ) becomes approximately zero, and the phase difference p (x) If the direction of change is positive, 1 is added to the value n of the internal counter. Also, the counting unit 202 calculates the current phase difference (output phase difference p of the phase difference detector 141) relative to the stored initial phase difference. (x) ) becomes approximately zero, and the phase difference p (x) If the direction of change is negative, subtract 1 from the value n of the internal counter.

[0091] The cumulative phase calculation unit 201 uses the value n of the internal counter of the counting unit 202 and the output phase difference p of the phase difference detector 141. (x) Based on this, the calculation in Equation 14 is performed, and the cumulative phase difference P (x) Outputs.

[0092] The calculation unit 142 uses equation 14 to calculate the cumulative phase difference P (x) Based on this, the position x of the second transmission line 106 relative to the first transmission line 101 is calculated.

[0093] With the configuration shown in Figure 8, the displacement measurement system 100 is freed from the constraint on position x shown in Equation 13. In other words, the displacement measurement system 100 can measure any position x.

[0094] According to the means of this embodiment, the two signals S output by the second transmission line 106 32(x) and S 41(x) By utilizing only this, it is possible to estimate any position x. In other words, a displacement measurement system 100 can be realized that can measure the displacement of a movable antenna while keeping the immovable structure and the movable structure separate.

[0095] (Third embodiment) In a third embodiment, a configuration for measuring the displacement of a moving body in a circular motion will be described.

[0096] Figure 9 shows an example configuration of a displacement measurement system 300 according to the third embodiment. The displacement measurement system 300 includes a first transmission line 301, a second transmission line 302, a signal source 303, a phase difference detector 304, and a calculation unit 307.

[0097] The first transmission line 301 is a transmission line configured in a ring shape. A signal source 303 is connected to the first end 305 of the first transmission line 301. The second end 306 of the first transmission line 301 is short-circuited. The first transmission line 301 has a characteristic impedance Z o The signal source 303 has an output impedance Z o It has.

[0098] The second transmission line 302 has a shape that allows it to move in a circular path opposite the first transmission line 301. The output signals from both ends of the second transmission line 302 are input to the phase difference detector 304. The characteristic impedance of the second transmission line 302 is Z o The input impedance of the phase difference detector 304 is Z. o That is the case.

[0099] The first transmission line 301 and the second transmission line 302 each have at least a portion of an arc shape.

[0100] Here, we assume that the length L of the first transmission line 301 satisfies equation 15.

[0101]

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[0102] The length L of the first transmission line 301 from the first end 305 to the second end 306 is an integer multiple of the wavelength λ of the signal output by the signal source 303.

[0103] At this time, if the length of the transmission line along the first transmission line 301 is x (hereinafter referred to as position x), the traveling wave at any position x on the first transmission line 301 is given by Equation 16.

[0104]

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[0105] Substituting L from Equation 15 for x in Equation 16, we obtain Equation 17.

[0106]

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[0107] Equation 17 means that the phases of the two signals indicated by arrows A and B in Figure 9 coincide. Since the directions of propagation of the traveling waves also coincide, the phases of the traveling waves observed at the first end 305 and the second end 306 are continuous.

[0108] Therefore, even if the second transmission line 302 is moved to a position that straddles the first end 305 and the second end 306, the output signal of the second transmission line 302 will not output an unusual phase.

[0109] Similar to the first embodiment, the phase difference detector 304 detects the phase difference between the signals at both ends of the second transmission line 302. Based on the phase difference detected by the phase difference detector 304, the calculation unit 142 calculates the position of the second transmission line 302 relative to the first transmission line 301.

[0110] According to the means of this embodiment, it is possible to measure the displacement of a moving object in a circular motion by utilizing only the two signals output by the second transmission line 106. In other words, a displacement measurement system 300 can be realized that can measure the displacement of a moving antenna in a circular motion while keeping the stationary structure and the movable structure independent.

[0111] (Other embodiments) This disclosure can also be implemented by supplying a program that implements one or more of the functions of the embodiments described above to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions.

[0112] Furthermore, the embodiments described above are merely examples illustrating how to implement this disclosure, and they should not be interpreted as limiting the technical scope of this disclosure. In other words, this disclosure can be implemented in various ways without departing from its technical concept or its main features.

[0113] This embodiment includes the following configuration. (Item 1) A first transmission line including a first end and a second end, wherein the first end is mismatched and the second end is connected to a signal source, A second transmission line, which includes a third end and a fourth end, and is relatively movable opposite the first transmission line, A phase difference detection means for detecting the phase difference between the signal at the third end of the second transmission line and the signal at the fourth end of the second transmission line. A displacement measurement system characterized by having the following features. (Item 2) The signal source has an output impedance that is approximately equal to the characteristic impedance of the first transmission line. The displacement measurement system according to item 1, characterized in that the phase difference detection means has an input impedance that is substantially equal to the characteristic impedance of the second transmission line. (Item 3) The displacement measurement system according to item 1 or 2, further comprising a calculation means for calculating the position of the second transmission line relative to the first transmission line based on the phase difference. (Item 4) The displacement measuring system according to any one of items 1 to 3, characterized in that the first end of the first transmission line is open-terminated. (Item 5) The displacement measuring system according to any one of items 1 to 3, characterized in that the first end of the first transmission line is short-circuited. (Item 6) The displacement measurement system according to any one of items 1 to 3, characterized in that the first end of the first transmission line is terminated by a reactance element having a combined impedance different from the characteristic impedance of the first transmission line, or by a reactance network. (Item 7) The displacement measurement system according to any one of items 1 to 6, characterized in that the first transmission line is formed on a dielectric substrate. (Item 8) The displacement measurement system according to any one of items 1 to 7, characterized in that the second transmission line is formed on a dielectric substrate. (Item 9) The displacement measurement system according to any one of items 1 to 8, characterized in that the second transmission line is shorter than the first transmission line. (Item 10) The displacement measurement system according to any one of items 1 to 9, characterized in that the first transmission line and the second transmission line each have a linear shape. (Item 11) The displacement measuring system according to any one of items 1 to 9, characterized in that the first transmission line and the second transmission line each have at least a portion of an arc shape. (Item 12) The first transmission line has at least a portion of its shape in an arc shape, A displacement measurement system according to any one of items 1 to 9, 11, characterized in that the length of the first transmission line from the first end to the second end is an integer multiple of the wavelength of the signal output by the signal source. (Item 13) A counting means that counts values ​​based on the phase difference detected by the phase difference detection means, The displacement measurement system according to any one of items 1 to 12, further comprising a calculation means for calculating a cumulative phase difference based on the phase difference detected by the phase difference detection means and the value. (Item 14) The aforementioned counting means is If the phase difference of the phase difference detection means with respect to the initial phase difference is approximately zero, and the direction of change of the phase difference of the phase difference detection means is positive, then 1 is added to the above value. The displacement measurement system according to item 13, characterized in that, if the phase difference of the phase difference detection means with respect to the initial phase difference is approximately zero, and the direction of change of the phase difference of the phase difference detection means is negative, 1 is subtracted from the value. (Item 15) The displacement measurement system according to item 13 or 14, further comprising a calculation means for calculating the position of the second transmission line relative to the first transmission line based on the cumulative phase difference. [Explanation of Symbols]

[0114] 101 First transmission line 102 First Terminus 103 The Second End 104 The Third End 105 The Fourth End 106 Second transmission line 110 First transmission line 111 End of the first transmission line 112 End of the first transmission line 113 Second transmission line 114 End of the second transmission line 115 End of the second transmission line Graph of 120 S32 Graph 121 S41 131 Signal source 132 Termination of impedance Z1 141 Phase difference detector 201 Accumulated Phase Calculation Unit 202 Counting Department 301 First transmission line 302 Second transmission line 303 Signal source 304 Phase difference detector 305 First end of the first transmission line 306 Second end of the first transmission line

Claims

1. A first transmission line including a first end and a second end, wherein the first end is mismatched and the second end is connected to a signal source, A second transmission line, which includes a third end and a fourth end, and is relatively movable opposite the first transmission line, A phase difference detection means for detecting the phase difference between the signal at the third end of the second transmission line and the signal at the fourth end of the second transmission line. A displacement measurement system characterized by having the following features.

2. The signal source has an output impedance that is approximately equal to the characteristic impedance of the first transmission line. The displacement measurement system according to claim 1, characterized in that the phase difference detection means has an input impedance substantially equal to the characteristic impedance of the second transmission line.

3. The displacement measurement system according to claim 1, further comprising a calculation means for calculating the position of the second transmission line relative to the first transmission line based on the phase difference.

4. The displacement measuring system according to claim 1, characterized in that the first end of the first transmission line is open-terminated.

5. The displacement measuring system according to claim 1, characterized in that the first end of the first transmission line is short-circuited.

6. The displacement measurement system according to claim 1, characterized in that the first end of the first transmission line is terminated by a reactance element having a combined impedance different from the characteristic impedance of the first transmission line, or by a reactance network.

7. The displacement measurement system according to claim 1, characterized in that the first transmission line is formed on a dielectric substrate.

8. The displacement measurement system according to claim 1, characterized in that the second transmission line is formed on a dielectric substrate.

9. The displacement measurement system according to claim 1, characterized in that the second transmission line is shorter than the first transmission line.

10. The displacement measurement system according to claim 1, characterized in that the first transmission line and the second transmission line each have a linear shape.

11. The displacement measuring system according to claim 1, characterized in that the first transmission line and the second transmission line each have at least a portion of an arc shape.

12. The first transmission line has at least a portion of its shape in an arc shape, The displacement measurement system according to claim 1, characterized in that the length of the first transmission line from the first end to the second end is an integer multiple of the wavelength of the signal output by the signal source.

13. A counting means that counts values ​​based on the phase difference detected by the phase difference detection means, The displacement measurement system according to claim 1, further comprising a calculation means for calculating a cumulative phase difference based on the phase difference detected by the phase difference detection means and the value.

14. The aforementioned counting means is If the phase difference of the phase difference detection means with respect to the initial phase difference is approximately zero, and the direction of change of the phase difference of the phase difference detection means is positive, then 1 is added to the above value. The displacement measurement system according to claim 13, characterized in that if the phase difference of the phase difference detection means with respect to the initial phase difference becomes approximately zero, and the direction of change of the phase difference of the phase difference detection means is negative, then 1 is subtracted from the value.

15. The displacement measurement system according to claim 13, further comprising a calculation means for calculating the position of the second transmission line relative to the first transmission line based on the cumulative phase difference.

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