JP2021175078A - Cable evaluation system, standing wave generator, and cable evaluation method - Google Patents

Abstract

To provide a cable evaluation system, a standing wave generator, and a cable evaluation method that can observe changes in amplitude characteristics that reflect phase changes caused by bending of a high-frequency coaxial cable.SOLUTION: A standing wave generator 20 inputs a signal to be measured output from a first input/output terminal 31 into an input port 13 of a signal analyzer 10 in a state in which a standing wave is generated by a test signal that is input from an output port 14 of the signal analyzer 10 to a second input/output terminal 32 and propagates through an RF cable 100 and a reflected signal of the test signal that is reflected by another end 100b of the RF cable 100 and propagates in the opposite direction through the RF cable 100. The signal analyzer 10 includes a cable evaluation unit 16 that calculates a difference between the amplitude characteristic of the signal to be measured before bending a predetermined length portion of the RF cable 100 and the amplitude characteristic of the signal to be measured after bending back the predetermined length portion of the RF cable 100, and displays the calculated difference on a display device 51.SELECTED DRAWING: Figure 1

Description

The present invention relates to a cable evaluation system, a standing wave generator, and a cable evaluation method, and more particularly to a cable evaluation system, a standing wave generator, and a cable evaluation method for evaluating the performance of a high-frequency coaxial cable for a millimeter wave band. ..

In recent years, 5G services that operate millimeter-wave band frequencies have started in various countries, and the production of 5G wireless devices such as 5G smartphones and local 5G devices is in full swing. At a 5G wireless device design / development company or its manufacturing factory, the output level and reception sensitivity of transmitted radio waves are measured for the wireless communication antenna of the 5G wireless device, and whether or not it meets the prescribed criteria. A performance test is conducted to determine. For example, the 5G wireless device to be tested is housed together with the test antenna in an anechoic box that is not affected by the surrounding radio wave environment, and the test antenna transmits the test signal to the 5G wireless device and receives the test signal. The so-called OTA test, in which the signal to be measured from the 5G wireless device is received by the test antenna by wireless communication, has come to be performed.

As shown in FIG. 6, the measurement system 200 for performing the OTA test on the 5G wireless device 110 includes a 5G tester 210, a frequency converter 220 having an up converter and a down converter, and an OTA chamber 230. There is. The OTA chamber 230 has a 5G radio device 110 and a test antenna 240 facing the radio communication antenna of the 5G radio device 110 in its internal space to prevent intrusion of radio waves from the outside and radiation of radio waves to the outside. It is housed in such a state. As the test antenna 240, an antenna for millimeter waves having directivity, such as a horn antenna, can be used. The test antenna 240 is adapted to transmit or receive a test signal for measuring the transmission characteristic or the reception characteristic of the 5G wireless device 110 with or from the wireless communication antenna of the 5G wireless device 110.

The frequency converter 220 and the test antenna 240 are a 2.92 mm connector (K connector) corresponding to the millimeter wave band, a 2.4 mm connector, or a high frequency coaxial cable with a 1.85 mm connector (hereinafter, simply "RF cable"). Also referred to as) 100, it is electrically connected.

The 5G tester 210 transmits a test signal to the test antenna 240 via the upconverter of the frequency converter 220 and the RF cable 100. Further, the 5G tester 210 receives the signal to be measured from the 5G wireless device 110 from the test antenna 240 via the RF cable 100 and the down converter of the frequency converter 220.

Many of the frequency converter 220 and the test antenna 240 used in the millimeter wave band measurement system 200 as described above have a voltage standing wave ratio (VSWR) of 2.5 or more. In the RF cable 100 connected to the frequency converter 220 and the test antenna 240 having VSWR of 2.5 or more in this way, for example, due to reflected waves caused by impedance mismatch at both ends of the RF cable 100, for example. A standing wave with an amplitude of 3 dB or more may occur.

FIG. 7 is a diagram for explaining signal level ripple caused by a standing wave generated between the test antenna 240 connected by the RF cable 100 and the frequency converter 220. Here, the insertion loss of the RF cable 100 is L (<1), the reflectance coefficient of the test antenna 240 is γ ₁ , and the reflectance coefficient of the frequency converter 220 is γ ₂ .

First, the measured signal level a ₀ is received by the test antenna 240. The signal to be measured becomes a signal of _{level a 1} = a ₀ L by propagating through the RF cable 100. As for the level a ₁ signal that has _{reached the frequency converter 220, a 1t} = a ₁ (1-γ ₂ ) is received by the frequency converter 220, and a _1r = a ₁ γ ₂ is reflected. _{The level a 1r} signal reflected by the frequency converter 220 _{becomes a level a 2} = a _1r L = a ₁ γ ₂ L signal by propagating through the RF cable 100.

Further, the level a ₂ signal is reflected by the test antenna 240 to become a level a _2r = a ₂ γ ₁ = a ₁ γ ₁ γ ₂ L signal. The level a _2r signal propagates through the RF cable 100 to become a level a ₃ = a _2r L = a ₁ γ ₁ γ ₂ L ² signal. Signal of the level _{a 3} having reached the frequency converter _{220, a 3t = a 3 (1} -γ 2) = a 1t γ 1 γ 2 L 2 is received by the frequency converter _{220, a 3r = a 3 γ} 2 = A ₁ γ ₁ γ ₂ ² L ² is reflected. After that, such reflection is repeated between the test antenna 240 and the frequency converter 220, and the frequency converter 220 receives signals of _{levels a 1t} , a _3t , a _5t , a _{7t, ...} It will be.

Assuming that the signal received by the frequency converter 220 is attenuated to a level that can be almost ignored after the level a _{5t, the maximum level that can be taken by the signal received by the frequency converter 220 is a 1t} + a _3t = a _1t (1 + γ ₁ γ ₂ L ^2). ). Therefore, the ripple of the signal received by the frequency converter 220 has the following equation (1) at the maximum, _{assuming that the level a 1t of} the signal reached from the test antenna 240 without being reflected by the frequency converter 220 is used as a reference level. )become that way.

Ripple size = ± 20 × log ₁₀ (1 + γ ₁ γ ₂ L ² ) ・ ・ ・ (1)
For example, when L = 0.944, γ ₁ = 2.5, and γ ₂ = 2.9, the magnitude of the ripple is ± 1.5 dB according to the equation (1).

In general, when an RF cable is bent, the phase of a signal propagating inside the RF cable changes (see, for example, Patent Documents 1 and 2). The reproducibility of the phase change due to bending differs greatly depending on the performance of the RF cable, and the phase cannot be restored even if the RF cable has low performance even if it is bent back. Therefore, even if the RF cable 100 in which the ripple due to the standing wave is generated as described above is slightly bent back, the amplitude characteristic of the signal propagating in the RF cable 100 changes significantly according to the phase change. There is. Bending back of the RF cable 100 occurs, for example, when the RF cable 100 is attached to the test antenna 240 and then installed in the OTA chamber 230.

Conventionally, as shown in FIG. 8, the performance of the RF cable is such that the input port 250a and the output port 250b of the vector network analyzer (VNA) 250 are connected to both ends 100a and 100b of the RF cable 100, respectively, and the phase and insertion loss are obtained. It was evaluated by measuring (insertion loss), reflection loss (return loss), and so on.

JP-A-2019-146113

Nobuyuki Kono, Kiyosuke Kuji, Katsuhisa Sato, Tadanori Hara, Risao Hayashi, "Changes in delay due to twisting of coaxial cable in VLBI", Journal of Geodetic Society, Vol. 40, No. 2 (1994), pp. 137-143

However, even if the frequency characteristics of the RF cable 100 before and after bending are measured with a measurement system as shown in FIG. 8 using an ideal 50Ω characteristic VNA, the noise level in the RF cable 100 The above standing wave does not occur. For this reason, conventionally, there has been a problem that even if a phase change occurs, it is not possible to observe a change in amplitude characteristics that is expected in actual operation.

The present invention has been made to solve such a conventional problem, and is a cable evaluation system capable of observing a change in amplitude characteristics reflecting a phase change caused by bending of a high-frequency coaxial cable, a standing wave generation. It is an object of the present invention to provide a device and cable evaluation method.

In order to solve the above problems, the cable evaluation system according to the present invention has a signal analyzer having an input port and an output port, and a distribution having a first input / output terminal, a second input / output terminal, and a third input / output terminal. The input port and the output port of the signal analyzer are connected to the first input / output terminal and the second input / output terminal, respectively, and one end of the high frequency coaxial cable to be tested and the first input / output terminal are connected to each other. A cable evaluation system including a standing wave generator to which three input / output terminals are connected, wherein the standing wave generator is input from the output port to the second input / output terminal and the high frequency coaxial cable. A standing wave is generated by the test signal propagating in the test signal and the reflected signal of the test signal reflected at the other end of the high-frequency coaxial cable and propagating in the opposite direction of the high-frequency coaxial cable. A signal output from the output terminal is input to the input port as a signal to be measured, and the signal analyzer uses the amplitude characteristics of the signal to be measured before bending a predetermined length portion of the high-frequency coaxial cable and the high-frequency coaxial. The configuration includes a cable evaluation unit that calculates a difference from the amplitude characteristic of the signal to be measured after the predetermined length portion of the cable is bent back and displays the calculated difference on a display device.

With this configuration, in the cable evaluation system according to the present invention, one end of the RF cable to be tested is connected to the third input / output terminal of the 3-resistance type distributor, and the test signal and reflection are reflected in the distributor and the RF cable. Generates a stationary wave with a signal. As a result, the cable evaluation system according to the present invention can observe changes in amplitude characteristics that reflect phase changes caused by bending of the RF cable, which could not be obtained by conventional measurement using only a VNA. This change in amplitude characteristics is smaller for RF cables with higher performance and larger for RF cables with poor performance. Since the cable evaluation system according to the present invention displays the obtained change in the amplitude characteristic on the display device, the performance of the RF cable to be tested can be visualized.

Further, in the cable evaluation system according to the present invention, the other end of the high-frequency coaxial cable may be open or short-circuited. Alternatively, in the cable evaluation system according to the present invention, a reflector having a desired reflection coefficient may be connected to the other end of the high-frequency coaxial cable.

With this configuration, the cable evaluation system according to the present invention can measure changes in amplitude characteristics according to the environment in which the RF cable is actually used, such as a measurement system for performing an OTA test.

Further, the cable evaluation system according to the present invention is for returning the high-frequency coaxial cable to its original straight-stretched shape after bending a predetermined length portion of the high-frequency coaxial cable having a straight-stretched shape with a predetermined curvature. It may be configured to further include a bending / stretching jig.

With this configuration, in the cable evaluation system according to the present invention, for example, by unifying the lengths of various RF cables to be tested in advance, the same bending can be performed on these cables with a bending / stretching jig. You can make a return. Further, as a result, the cable evaluation system according to the present invention can measure changes in amplitude characteristics for various RF cables under the same conditions.

Further, in the cable evaluation system according to the present invention, the standing wave generator may further include an attenuator inserted between the third input / output terminal and one end of the high frequency coaxial cable. ..

With this configuration, the cable evaluation system according to the present invention can input the signal to be measured to the input port and the output port of the signal analyzer even when the amplitude of the standing wave generated in the distributor and the RF cable is relatively large. It can be attenuated to an amplitude suitable for.

Further, the stationary wave generator according to the present invention includes a distributor having a first input / output terminal, a second input / output terminal, and a third input / output terminal, an attenuator connected to the third input / output terminal, and the like. The configuration is such that one end of a high-frequency coaxial cable and the third input / output terminal are connected via the attenuator.

Further, the cable evaluation method according to the present invention is a stationary wave including a signal analyzer having an input port and an output port, and a distributor having a first input / output terminal, a second input / output terminal, and a third input / output terminal. A cable evaluation method using a generator, in which the input port and the output port of the signal analyzer are connected to the first input / output terminal and the second input / output terminal, respectively, and the subject to be tested. A connection step for connecting one end of the high-frequency coaxial cable and the third input / output terminal, a test signal input from the output port to the second input / output terminal and propagating through the high-frequency coaxial cable, and the high-frequency coaxial cable. A signal output from the first input / output terminal is used as a signal to be measured in a state where a standing wave is generated by a reflected signal of the test signal that is reflected at the other end and propagates in the opposite direction of the high frequency coaxial cable. A standing wave generation step to be input to the input port, a first measurement step for measuring the amplitude characteristic of the signal to be measured before bending a predetermined length portion of the high frequency coaxial cable, and the predetermined length of the high frequency coaxial cable. A second measurement step for measuring the amplitude characteristic of the signal to be measured after bending back the portion, an amplitude characteristic measured by the first measurement step, and an amplitude characteristic measured by the second measurement step. It includes a cable evaluation step of calculating the difference and displaying the calculated difference on the display device.

With this configuration, in the cable evaluation method according to the present invention, one end of the RF cable to be tested is connected to the third input / output terminal of the 3-resistance type distributor, and the test signal and reflection are reflected in the distributor and the RF cable. Generates a standing wave with a signal. As a result, in the cable evaluation method according to the present invention, it is possible to observe a change in amplitude characteristics reflecting a phase change due to bending of the RF cable, which could not be obtained by a conventional measurement using only a VNA. This change in amplitude characteristics is smaller for RF cables with higher performance and larger for RF cables with poor performance. In the cable evaluation method according to the present invention, since the obtained change in the amplitude characteristic is displayed on the display device, the performance of the RF cable to be tested can be visualized.

The present invention provides a cable evaluation system, a standing wave generator, and a cable evaluation method capable of observing changes in amplitude characteristics reflecting phase changes caused by bending of a high-frequency coaxial cable.

It is a block diagram which shows the structure of the cable evaluation system which concerns on embodiment of this invention. It is a top view which shows the structure of the bending-stretching jig provided in the cable evaluation system which concerns on embodiment of this invention. It is a top view which shows the procedure of bending and stretching an RF cable by the bending and stretching jig provided in the cable evaluation system which concerns on embodiment of this invention, and (a) shows the state which the RF cable is stretched straight. (B) shows a state in which the RF cable is bent, and (c) shows a state in which the RF cable is straightened again. It is a graph which shows typically the measurement result of the signal analyzer provided in the cable evaluation system which concerns on embodiment of this invention, (a) shows the measurement result of the ultra-high performance and expensive RF cable, and (b). ) Shows the measurement results of a high-performance and relatively inexpensive RF cable, and (c) shows the measurement results of a very low-performance and very inexpensive RF cable. It is a flowchart for demonstrating the process of the cable evaluation method using the cable evaluation system which concerns on embodiment of this invention. It is a block diagram which shows the structure of the conventional measurement system for performing the OTA test for the radio device for 5G. FIG. 6 is a diagram for explaining signal level ripple caused by a standing wave generated between a test antenna connected by an RF cable and a frequency converter in the measurement system of FIG. It is a block diagram which shows the structure of the conventional measurement system for measuring the frequency characteristic of an RF cable using a VNA.

Hereinafter, embodiments of the cable evaluation system, the standing wave generator, and the cable evaluation method according to the present invention will be described with reference to the drawings. The dimensional ratio of each component on each drawing does not always match the actual dimensional ratio.

As shown in FIG. 1, the cable evaluation system 1 according to the embodiment of the present invention evaluates the performance of the RF cable 100 to be tested, and includes a signal analyzer 10, a standing wave generator 20, and a standing wave generator 20. A bending / stretching jig 40, a display device 51, an operation device 52, and a control device 53 are provided.

The RF cable 100 to be tested is, for example, a 3.5 mm connector corresponding to a millimeter wave band, a 2.92 mm connector (K connector), a 2.4 mm connector, 1.85 mm, 1.35 mm, 1.0 mm, or 0. A high-frequency coaxial cable with a .8 mm connector.

The signal analyzer 10 is, for example, a two-port VNA including a signal generation unit 11, an input / output unit 12, an input port 13, an output port 14, an amplitude characteristic measurement unit 15, and a cable evaluation unit 16. .. One end 100a of the RF cable 100 to be tested is connected between the input port 13 and the output port 14 via a standing wave generator 20.

The signal generation unit 11 is adapted to generate a test signal of an arbitrary frequency, an arbitrary signal level, and an arbitrary modulation method, for example, from several MHz to several tens of GHz.

The input / output unit 12 outputs the test signal output from the signal generation unit 11 to the output port 14. Further, the input / output unit 12 outputs the signal to be measured input from the input port 13 to the amplitude characteristic measurement unit 15.

The amplitude characteristic measuring unit 15 measures the amplitude characteristic (insertion loss S ₂₁ ) of the signal to be measured input from the input / output unit 12.

The standing wave generator 20 has three resistors of 16 + 2 / 3Ω, and a first input / output terminal 31, a second input / output terminal 32, and a third input / output terminal 33 connected to the ends of the respective resistors. Includes a 3-resistive distributor 30. The first input / output terminal 31 and the second input / output terminal 32 are connected to the input port 13 and the output port 14 of the signal analyzer 10, respectively.

Further, one end 100a of the RF cable 100 to be tested is connected to the third input / output terminal 33. The standing wave generator 20 may further include an attenuator 34 having a characteristic impedance of 50 Ω. The attenuator 34 is inserted between the third input / output terminal 33 of the distributor 30 and one end 100a of the RF cable 100 in order to attenuate the signal input / output to / from the signal analyzer 10 to an appropriate amplitude. In this case, one end 100a of the RF cable 100 is connected to the third input / output terminal 33 via the attenuator 34.

The standing wave generator 20 is a test signal that is input from the output port 14 of the signal analyzer 10 to the second input / output terminal 32 and propagates through the RF cable 100, and is reflected by the other end 100b of the RF cable 100 and is reflected by the RF cable. A standing wave is generated by the reflected signal of the test signal propagating in the opposite direction of 100. As a result, a signal to be measured, which is obtained by adding a reflected signal to the test signal input to the second input / output terminal 32, is input to the input port 13 of the signal analyzer 10 from the first input / output terminal 31.

The distributor 30 has, for example, a frequency band used of about DC to 100 GHz, and when all the terminals of the first input / output terminal 31, the second input / output terminal 32, and the third input / output terminal 33 are terminated with 50Ω. In addition, it is designed so that the amplitude balance between the terminals is even. On the other hand, if any one of the first input / output terminal 31, the second input / output terminal 32, and the third input / output terminal 33 is not terminated with 50Ω, the amplitude balance between the terminals is balanced. It collapses. In the present invention, a standing wave is generated in the distributor 30 and the RF cable 100 by using the distributor 30 in a state where the amplitude balance between the terminals is intentionally disturbed. Specifically, by opening the other end 100b of the RF cable 100, it is possible to create a situation in which the amplitude of the generated standing wave is the largest. Alternatively, the other end 100b of the RF cable 100 may be short-circuited. Alternatively, a circuit that does not cause total internal reflection, such as a reflector having a desired reflection coefficient according to the actual usage environment of the RF cable 100, may be connected to the other end 100b of the RF cable 100.

As shown in FIG. 2, the bending / stretching jig 40 is a plate-shaped member having a predetermined thickness in a direction perpendicular to the paper surface, and a predetermined length portion of a straightly extended RF cable 100 is defined. A groove-shaped bending portion 41 for bending with a curvature (1 / R) and a groove-shaped extending portion 42 for forming the RF cable 100 into a straightly extended shape are formed. For example, the width of the bent portion 41 and the extended portion 42 is 20 mm. The bent portion 41 includes two straight portions having a length of 50 mm and a curved portion having an inner diameter radius of curvature R of 120 mm and connecting the two straight portions. In this case, the predetermined length of the RF cable 100 bent by the bent portion 41 is about 380 mm. Further, the extending portion 42 is composed of a straight portion having a length of 500 mm, and includes one of the two straight portions of the bending portion 41. The RF cable 100 can be arranged on the bent portion 41 and the extended portion 42 from the direction from the front side to the back side perpendicular to the paper surface of FIG.

FIG. 3 is a diagram showing a procedure for bending and stretching the RF cable 100 using the bending and stretching jig 40. First, as shown in FIG. 3A, the RF cable 100 is arranged in the stretched portion 42, and the RF cable 100 is arranged into a straight stretched shape. At this time, the reference amplitude characteristic measuring unit 15 of the signal analyzer 10 measures the reference insertion loss S ₂₁ (hereinafter, also referred to as “reference amplitude characteristic”).

Next, as shown in FIG. 3 (b), a part of the RF cable 100 on the 100a side is left in a straight line portion common to the extending portion 42 and the bending portion 41 of the bending and stretching jig 40. By arranging the predetermined length portion of the RF cable 100 on the bending portion 41 of the bending and stretching jig 40, the predetermined length portion of the linearly extended RF cable 100 is bent with a predetermined curvature. Next, as shown in FIG. 3C, a part of the RF cable 100 on the 100a side is left in a straight line portion common to the extending portion 42 and the bending portion 41 of the bending and stretching jig 40. , The RF cable 100 is placed again in the stretched portion 42, and the RF cable 100 is returned to its original straight stretched shape. _{At this time, the insertion loss S 21} (hereinafter, also referred to as “amplitude characteristic after bending back”) is measured again by the amplitude characteristic measuring unit 15 of the signal analyzer 10.

That is, the amplitude characteristic measuring unit 15 of the signal analyzer 10 has the reference amplitude characteristic of the signal to be measured before bending the predetermined length portion of the RF cable 100 and the subject after bending back the predetermined length portion of the RF cable 100. The amplitude characteristics after bending back of the measurement signal are measured.

The cable evaluation unit 16 of the signal analyzer 10 calculates the difference between the reference amplitude characteristic measured by the amplitude characteristic measuring unit 15 and the amplitude characteristic after bending back, that is, the change in the amplitude characteristic due to bending back of the RF cable 100. Further, the cable evaluation unit 16 causes the display device 51 to display the calculated change in the amplitude characteristic. This change in amplitude characteristics is, so to speak, a conversion of the phase change of the RF cable 100 into a change in amplitude. If the other end 100b of the RF cable 100 is terminated with 50Ω, the reflection at the other end 100b is suppressed, so that almost the same amplitude characteristics can be obtained before and after bending the RF cable 100. Therefore, the change in amplitude characteristics becomes unobservable.

The graph of FIG. 4 schematically shows the frequency characteristics of the difference between the reference amplitude characteristics and the amplitude characteristics after bending back for three types of RF cables having different performances from each other. FIG. 4 (a) shows an ultra-high performance and expensive RF cable (product A), FIG. 4 (b) shows a high performance and relatively inexpensive RF cable (product B), and FIG. 4 (c) shows relatively low performance. It shows the result of a very cheap RF cable (Product C). Since the ultra-high performance RF cable (product A) is designed to suppress the phase change due to bending, the change in amplitude characteristics is extremely small. On the contrary, it was found that the lower the performance of the RF cable, the larger the change in the amplitude characteristics.

The display device 51 is composed of a display device such as an LCD or a CRT, and the reference amplitude characteristic, the amplitude characteristic after bending back, and the reference amplitude measured by the signal analyzer 10 according to the control signal output from the control device 53. Various display contents such as the difference between the characteristics and the amplitude characteristics after bending back are displayed. Further, the display device 51 displays an operation target such as a button for setting measurement conditions, a soft key, a pull-down menu, and a text box according to a control signal output from the control device 53. There is.

The operation device 52 is for receiving an operation input by a user, and is composed of, for example, a touch panel provided on the surface of the display screen of the display device 51. Alternatively, the operating device 52 may be configured to include an input device such as a keyboard or mouse. The operation input to the operation device 52 is detected by the control device 53. For example, the operating device 52 allows the user to arbitrarily specify the measurement start timing of the amplitude characteristic measuring unit 15.

The control device 53 is composed of, for example, a microcomputer including a CPU, ROM, RAM, HDD, or the like, a personal computer, or the like, and controls the operation of each of the above-mentioned parts constituting the cable evaluation system 1. Further, the control device 53 can configure at least a part of the amplitude characteristic measuring unit 15 and the cable evaluation unit 16 by software by transferring a predetermined program stored in the ROM or the like to the RAM and executing the program. be. At least a part of the amplitude characteristic measurement unit 15 and the cable evaluation unit 16 can be configured by a digital circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Alternatively, at least a part of the amplitude characteristic measuring unit 15 and the cable evaluation unit 16 can be configured by appropriately combining hardware processing by a digital circuit and software processing by a predetermined program.

The display device 51, the operation device 52, and the control device 53 may be configured in the signal analysis device 10.

Hereinafter, an example of the processing of the cable evaluation method using the cable evaluation system 1 of the present embodiment will be described with reference to the flowchart of FIG.

First, as shown in FIG. 3A, the user performs an operation of arranging the RF cable 100 on the stretching portion 42 of the bending and stretching jig 40 and adjusting the RF cable 100 into a straight stretched shape (step). S1).

Next, the user performs an operation of connecting the input port 13 and the output port 14 of the signal analyzer 10 to the first input / output terminal 31 and the second input / output terminal 32 of the standing wave generator 20, respectively. Further, the user performs an operation of connecting one end 100a of the RF cable 100 to be tested and the third input / output terminal 33 of the standing wave generator 20 via the attenuator 34 (connection step S2).

Next, the signal generation unit 11 of the signal analyzer 10 outputs a test signal from the output port 14 to the second input / output terminal 32 via the input / output unit 12. As a result, a standing wave is generated by the test signal propagating through the RF cable 100 and the reflected signal of the test signal reflected by the other end 100b of the RF cable 100 and propagating in the opposite direction of the RF cable 100. In this state, the measured signal obtained by adding the reflected signal to the test signal input to the second input / output terminal 32 is input from the first input / output terminal 31 to the input port 13 (standing wave generation step S3). ..

Next, the amplitude characteristic measuring unit 15 of the signal analyzer 10 is an RF cable 100 input from the input port 13 via the input / output unit 12 in response to a measurement start instruction from the operating device 52 by the user's operation input. The reference amplitude characteristic of the signal to be measured before bending the predetermined length portion of the above is measured. Further, the display device 51 displays the reference amplitude characteristic measured by the amplitude characteristic measuring unit 15 (first measurement step S4).

Next, as shown in FIG. 3B, the user keeps a part of the RF cable 100 on the 100a side at one end in a straight line portion common to the extending portion 42 and the bending portion 41 of the bending and stretching jig 40. In this state, by arranging the predetermined length portion of the RF cable 100 on the bending portion 41 of the bending and stretching jig 40, the work of bending the predetermined length portion of the linearly extended RF cable 100 with a predetermined curvature can be performed. Will be done. Further, as shown in FIG. 3C, the user keeps a part of the RF cable 100 on the 100a side at one end in a straight line portion common to the extending portion 42 and the bending portion 41 of the bending and stretching jig 40. In this state, the RF cable 100 is re-arranged in the stretched portion 42, and the work of returning the RF cable 100 to the original straight stretched shape is performed (step S5).

Next, the amplitude characteristic measuring unit 15 of the signal analyzer 10 is an RF cable 100 input from the input port 13 via the input / output unit 12 in response to a measurement start instruction from the operating device 52 by the user's operation input. The amplitude characteristic of the signal to be measured after bending back the predetermined length portion of is measured. Further, the display device 51 displays the amplitude characteristic after bending back measured by the amplitude characteristic measuring unit 15 (second measurement step S6).

Next, the cable evaluation unit 16 of the signal analyzer 10 determines the difference between the reference amplitude characteristic measured in the first measurement step S4 and the amplitude after bending back measured in the second measurement step S6, that is, the RF cable 100. Calculate the change in amplitude characteristics due to bending back. Further, the display device 51 displays the change in the amplitude characteristic calculated by the cable evaluation unit 16 (cable evaluation step S7).

As described above, in the cable evaluation system 1 according to the present embodiment, one end 100a of the RF cable 100 to be tested is connected to the third input / output terminal 33 of the 3-resistance type distributor 30, and the distributor 30 And a standing wave by the test signal and the reflected signal is generated in the RF cable 100. Thereby, the cable evaluation system 1 according to the present embodiment can observe the change in the amplitude characteristic reflecting the phase change due to the bending of the RF cable 100, which could not be obtained by the conventional measurement using only the VNA. This change in amplitude characteristics is smaller for RF cables with higher performance and larger for RF cables with poor performance. Since the cable evaluation system 1 according to the present embodiment displays the obtained change in the amplitude characteristic on the display device 51, the performance of the RF cable 100 to be tested can be visualized.

Further, in the cable evaluation system 1 according to the present embodiment, the other end 100b of the RF cable 100 to be tested may be open or short-circuited. Alternatively, a reflector having a desired reflectance coefficient may be connected to the other end 100b of the RF cable 100 to be tested. As a result, the cable evaluation system 1 according to the present embodiment can measure changes in amplitude characteristics according to the environment in which the RF cable 100 is actually used, such as a measurement system for performing an OTA test.

Further, the cable evaluation system 1 according to the present embodiment includes a bending / stretching jig 40 for bending back a predetermined length portion of the RF cable 100 with a predetermined curvature. For example, if the lengths of the various RF cables to be tested are unified in advance, the same bending back can be performed on these cables by the bending and stretching jig 40. Further, as a result, the cable evaluation system 1 according to the present embodiment can measure changes in the amplitude characteristics of various RF cables under the same conditions.

Further, in the cable evaluation system 1 according to the present embodiment, the attenuator 34 is inserted between the third input / output terminal 33 of the distributor 30 and one end 100a of the RF cable 100. As a result, the cable evaluation system 1 according to the present embodiment inputs the signal to be measured to the signal analyzer 10 even when the amplitude of the standing wave generated in the distributor 30 and the RF cable 100 is relatively large. It can be attenuated to an amplitude suitable for the port 13 and the output port 14.

Further, in the embodiment described above, the signal analyzer 10 outputs a test signal from the output port 14, and measures the amplitude characteristic of the signal input from the input port 13 by the amplitude characteristic measuring unit 15. However, the present invention is not limited to this. For example, the signal analyzer 10 outputs a test signal from the output port 14, and _{measures the amplitude characteristic (reflection coefficient S 11} ) of the reflected wave signal input from the output port 14 again by the amplitude characteristic measuring unit 15. It may be the one that performs port measurement. At this time, the unused first input / output terminal 31 of the distributor 30 needs to be terminated with 50Ω. Alternatively, the signal analyzer 10 outputs a test signal from the input port 13 and _{measures the amplitude characteristic (reflection coefficient S 11} ) of the reflected wave signal input from the input port 13 again by the amplitude characteristic measuring unit 15. It may be the one that performs port measurement. At this time, the unused second input / output terminal 32 of the distributor 30 needs to be terminated with 50Ω.

1 Cable evaluation system 10 Signal analyzer 11 Signal generator 12 Input / output unit 13 Input port 14 Output port 15 Oscillation characteristic measurement unit 16 Cable evaluation unit 20 Standing wave generator 30 Distributor 31 1st input / output terminal 32 2nd input Output terminal 33 Third input / output terminal 34 Attenuator 40 Bending and stretching jig 41 Bending part 42 Stretching part 51 Display device 52 Operating device 53 Control device 100 RF cable 100a One end 100b Other end

Claims (8)

A signal analyzer (10) having an input port (13) and an output port (14),
A distributor (30) having a first input / output terminal (31), a second input / output terminal (32), and a third input / output terminal (33), and the input port and the output port of the signal analyzer. A standing wave in which the first input / output terminal and the second input / output terminal are connected, respectively, and one end (100a) of the high-frequency coaxial cable (100) to be tested and the third input / output terminal are connected. A cable evaluation system (1) including a generator (20).
The stationary wave generator is input to the second input / output terminal from the output port and propagates through the high-frequency coaxial cable, and is reflected by the other end (100b) of the high-frequency coaxial cable to be reflected by the high-frequency coaxial cable. A signal output from the first input / output terminal is input to the input port as a signal to be measured in a state where a standing wave is generated by the reflected signal of the test signal propagating in the opposite direction of the cable.
The signal analyzer has the amplitude characteristics of the signal to be measured before bending the predetermined length portion of the high-frequency coaxial cable, and the amplitude of the signal to be measured after bending back the predetermined length portion of the high-frequency coaxial cable. A cable evaluation system including a cable evaluation unit (16) that calculates a difference from a characteristic and displays the calculated difference on a display device (51). The cable evaluation system according to claim 1, wherein the other end of the high-frequency coaxial cable is open. The cable evaluation system according to claim 1, wherein the other end of the high-frequency coaxial cable is short-circuited. The cable evaluation system according to claim 1, wherein a reflector having a desired reflectance coefficient is connected to the other end of the high-frequency coaxial cable. A bending / stretching jig (40) for returning the high-frequency coaxial cable to its original straight-stretched shape after bending a predetermined length portion of the high-frequency coaxial cable having a straight-stretched shape with a predetermined curvature is further provided. The cable evaluation system according to any one of claims 1 to 4, wherein the cable evaluation system is characterized in that. Any of claims 1 to 5, wherein the standing wave generator further includes an attenuator (34) inserted between the third input / output terminal and one end of the high-frequency coaxial cable. Cable evaluation system described in. A distributor (30) having a first input / output terminal (31), a second input / output terminal (32), and a third input / output terminal (33),
Includes an attenuator (34) connected to the third input / output terminal.
A standing wave generator characterized in that one end (100a) of a high-frequency coaxial cable (100) and the third input / output terminal are connected via the attenuator. A signal analyzer (10) having an input port (13) and an output port (14),
Cable evaluation using a standing wave generator (20) including a distributor (30) having a first input / output terminal (31), a second input / output terminal (32), and a third input / output terminal (33). It ’s a method,
The input port and the output port of the signal analyzer are connected to the first input / output terminal and the second input / output terminal, respectively, and one end (100a) of the high frequency coaxial cable (100) to be tested and the said. The connection step (S2) for connecting to the third input / output terminal and
The test signal that is input from the output port to the second input / output terminal and propagates through the high-frequency coaxial cable, and the test signal that is reflected by the other end (100b) of the high-frequency coaxial cable and propagates in the opposite direction of the high-frequency coaxial cable. In the state where the standing wave generated by the reflected signal of the test signal is generated, the standing wave generation step (S3) in which the signal output from the first input / output terminal is input to the input port as the signal to be measured, and the standing wave generation step (S3).
The first measurement step (S4) of measuring the amplitude characteristic of the signal to be measured before bending the predetermined length portion of the high-frequency coaxial cable, and
A second measurement step (S6) for measuring the amplitude characteristic of the signal to be measured after bending back the predetermined length portion of the high-frequency coaxial cable, and
Cable evaluation step (S7) in which the difference between the amplitude characteristic measured by the first measurement step and the amplitude characteristic measured by the second measurement step is calculated and the calculated difference is displayed on the display device (51). And, a cable evaluation method characterized by including.

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