Measuring device and measurement method

Abstract

To more quickly measure signal characteristics showing the features of an object in microwave resonance frequency measurement.SOLUTION: A measuring device (100) has a modulation signal transmission section (1) and a modulation signal reception section (2), wherein the modulation signal transmission section transmits a predetermined multi-tone modulation signal having a known spectrum to a microwave resonator (3) that is used while a measured object (4) is disposed inside, the modulation signal reception section receives a multi-tone modulation signal output from the microwave resonator, transmission characteristics of the measured object are calculated by comparing the spectrum of a multi-tone modulation signal transmitted to the microwave resonator by the modulation signal transmission section with the spectrum of a multi-tone modulation signal received by the modulation signal reception section, and the resonance frequency of the microwave resonator is calculated on the basis of the calculated transmission characteristics.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measuring device and a measuring method using microwave resonance.

Background Art

[0002] When a dielectric, which is a small article such as a tablet, is placed in a part of a microwave resonator, the resonance frequency and the resonance linewidth change compared to the state without the dielectric. Using these changes in the resonance frequency and the resonance linewidth, the characteristics of the object are measured. The characteristics of the object are, for example, weight. Such a measuring device is, for example, adopted in an article inspection device for inspecting whether the weight or volume of a manufactured article is within the standard.

[0003] Patent Document 1 describes an article inspection device. The article inspection device according to Patent Document 1 includes a transport rotating body that is disposed below a supply means for supplying articles, rotates about a horizontal axis, and accommodates and transports the articles dropped from the supply means in a recess on the outer periphery. The article inspection device includes a guide wall that is provided along the outer periphery of the transport rotating body, closes the opening of the recess that moves as the transport rotating body rotates, forms a transport chamber together with the recess, and has a terminal position that serves as an article discharge position. The article inspection device includes inspection means that is disposed below the transport rotating body and on which the articles discharged from the terminal position are placed. The recess is formed in a slit shape having a predetermined length that allows the article to move in the outer peripheral direction along the rotation direction of the transport rotating body, and has a front wall against which the article hits on the front side in the moving direction of the article due to gravity as the transport rotating body rotates, and a rear wall that pushes the article out from the inspection means on the rear side in the moving direction of the article.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a method for measuring the characteristics of small objects, a method is known in which a single-tone signal is swept using a VNA (vector network analyzer) or the like, and the transmission characteristics of a microwave resonator are measured.

[0006] Here, if the required measurement accuracy can be obtained, generally, the shorter the measurement time, the higher the utilization value, and it is considered particularly suitable when inspecting a large number of articles.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a measuring apparatus and a measuring method capable of measuring signal characteristics indicating the characteristics of an object in a shorter time.

Means for Solving the Problems

[0008] In order to achieve the above-described object, the measuring apparatus and the measuring method according to the present invention are characterized by the following [1] to [6]. [1] A modulation signal transmission unit (1) and a modulation signal reception unit (2) are provided. The modulation signal transmission unit transmits a predetermined multi-tone modulation signal having a known spectrum to a microwave resonator (3) in which an object to be measured (4) is disposed and used inside. The modulation signal reception unit receives the multi-tone modulation signal output from the microwave resonator, by comparing the spectrum of the multi-tone modulation signal transmitted by the modulation signal transmission unit to the microwave resonator with the spectrum of the multi-tone modulation signal received by the modulation signal reception unit, the transmission characteristics of the object to be measured are calculated, Based on the calculated transmission characteristics, the resonance frequency of the microwave resonator is calculated. Measuring apparatus. [2] The modulation signal reception unit calculates the weight of the object to be measured based on the calculated resonance frequency. The measuring apparatus according to [1]. [3] The modulation signal transmitting unit transmits a multi-tone modulation signal modulated based on OFDM to the microwave resonator. The measuring device according to [1]. [4] The modulation signal transmitting unit transmits a multi-tone modulation signal obtained by performing symbol mapping processing based on binary pseudo-random numbers to the microwave resonator. The measuring device according to [1]. [5] The content of the multi-tone modulation signal transmitted by the modulation signal transmitting unit to the microwave resonator is the same at the first transmission time and the second transmission time. The measuring device according to [1]. [6] A microwave measurement method using a measuring device including a modulation signal transmitting unit (1) and a modulation signal receiving unit (2), a step in which the modulation signal transmitting unit transmits a predetermined multi-tone modulation signal with a known spectrum to a microwave resonator (3) in which an object to be measured (4) is disposed and used inside; a step in which the modulation signal receiving unit receives the multi-tone modulation signal output from the microwave resonator; a step in which the modulation signal receiving unit calculates the transmission characteristics of the object to be measured by comparing the spectrum of the multi-tone modulation signal transmitted by the modulation signal transmitting unit to the microwave resonator with the spectrum of the multi-tone modulation signal received by the modulation signal receiving unit; a step in which the modulation signal receiving unit calculates the resonance frequency of the microwave resonator based on the calculated transmission characteristics; A measurement method having the above.

[0009] According to the configuration of [1] above, it is possible to provide a measuring device capable of measuring the resonance frequency of a microwave resonator that changes according to the transmission characteristics of an object to be measured in a shorter time. According to the configuration of [2] above, it is possible to provide a measuring device capable of measuring characteristics of the physical properties of an object to be measured, such as weight, in a shorter time based on the resonance frequency detected in a shorter time. According to the configuration of [3] above, a part of the technology related to the signal processing of OFDM, which is widespread in the field of wireless communication, can be applied to the measurement of the resonance frequency of a microwave resonator. According to the configuration of [4] above, the peak power with respect to the average power of a multi-tone modulation signal can be suppressed to a predetermined value or less with high probability. According to the configuration of [5] above, the modulation signal transmission unit can transmit, for example, a multi-tone modulation signal obtained by repeatedly inputting binary pseudo-random numbers and performing symbol mapping processing such as QPSK to a microwave resonator. According to the configuration of [6] above, it is possible to provide a measurement method capable of measuring the resonance frequency of a microwave resonator that changes according to the transmission characteristics of a measurement object in a shorter time.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a measurement apparatus and a measurement method capable of measuring signal characteristics indicating the characteristics of an object in a shorter time.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] FIG. 1 is a conceptual diagram showing a configuration example of a measuring device according to an embodiment of the present disclosure.

[0014] The measuring device 100 obtains physical characteristics of an object such as a small article using a microwave resonance frequency, and includes a modulation signal transmission unit 1 and a modulation signal reception unit 2. The modulation signal transmission unit 1 has a function of transmitting a modulation signal to the microwave resonator 3. The modulation signal reception unit 2 has a function of receiving a modulation signal from the microwave resonator 3. Note that the microwave resonator 3 may be incorporated in the measuring device 100, or the measuring device 100 and the microwave resonator 3 may be separate.

[0015] The modulation signal transmission unit 1 transmits a multi-tone modulation signal to the microwave resonator 3.

[0016] The measuring device 100 includes a control unit and a storage unit (not shown). The control unit is configured using, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Signal Processor), or an FPGA (Field Programmable Gate Array).

[0017] The storage unit included in the measuring device 100 stores a program executed by the control unit and various data used during execution. The storage unit may include an HDD, a ROM, a RAM, etc., and stores various programs (OS, application software, etc.) and various data executed by the control unit.

[0018] The control unit included in the measuring device 100 functionally realizes the modulation signal transmission unit 1 and the modulation signal reception unit 2 by referring to the program stored in the storage unit and executing the program.

[0019] The modulation signal transmitting unit 1 transmits a modulation signal to the microwave resonator 3. The modulation signal received by the modulation signal receiving unit 2 after passing through the microwave resonator 3 is received and analyzed. More specifically, the signal transmitted from the modulation signal transmitting unit 1 to the microwave resonator 3 is a predetermined modulation signal with a known spectrum. The modulation signal obtained after passing through the microwave resonator 3 is received by the modulation signal receiving unit 2 for spectrum analysis. The modulation signal receiving unit 2 calculates the transmission characteristics of the object under measurement by comparing the spectrum of the received modulation signal with the spectrum of the modulation signal transmitted from the modulation signal transmitting unit 1 to the microwave resonator 3. The object under measurement is a small article placed inside the microwave resonator 3. An example of the small article is a tablet, but the small article is not limited to a tablet. The modulation signal receiving unit 2 calculates the resonance frequency of the microwave resonator 3 based on the calculated transmission characteristics. For modulation, for example, ODFM with first-order modulation as phase modulation such as QPSK may be used. Note that the binary pseudo-random numbers in the figure will be described later.

[0020] FIG. 2 is a conceptual diagram illustrating a microwave resonator used in the measuring apparatus according to an embodiment of the present disclosure.

[0021] The microwave resonator 3 includes an input-side loop antenna 31, an output-side loop antenna 32, an object under measurement inlet 33, and an object under measurement outlet 34. The microwave resonator 3 generally has a rectangular outer shape. However, the outer shape of the microwave resonator 3 may be other than rectangular.

[0022] The object under measurement is inserted into the object under measurement inlet 33 of the microwave resonator 3 and discharged from the object under measurement outlet 34.

[0023] Examples of the method for inserting and discharging the object under measurement include the following. · Shoot the object under measurement with an air gun or the like. · After arranging the microwave resonator 3 such that the object under measurement inlet 33 and the object under measurement outlet 34 are vertically aligned downward, drop the object under measurement freely from the object under measurement inlet 33. ·Pass the belt of the belt conveyor from the object to be measured input port 33 toward the object to be measured output port 34, and convey the object to be measured by the belt conveyor.

[0024] When a dielectric such as a tablet, which is a non-measured object, is placed in a part of the microwave resonator 3, the resonance frequency and resonance line width of the microwave resonator 3 change with respect to the state where no dielectric is present. In addition, when a dielectric is arranged near a resonator based on a transmission line formed on a substrate, the resonance frequency and resonance line width also change. Using this change in the resonance frequency and resonance line width, the characteristics of the object to be measured are measured. The characteristics of the object to be measured mean, for example, weight, but may also be characteristics other than weight. For example, based on the change in the resonance frequency due to the presence or absence of a dielectric or a compositional change such as the moisture content, and the relationship between the volume, relative permittivity, dielectric tangent (dielectric loss), etc. of the dielectric measured in advance, the modulation signal receiving unit 2 can obtain the characteristics of the dielectric that is the object to be measured.

[0025] FIG. 3 is a conceptual diagram illustrating a microwave resonator used in a measuring apparatus according to an embodiment of the present disclosure.

[0026] For convenience of explanation, in FIG. 3, a rectangular coordinate system composed of the x-axis, y-axis, and z-axis is shown. Also, in FIG. 3, the electric field is indicated by a thick solid line and the magnetic field is indicated by a thick broken line, respectively.

[0027] When the loop plane is taken as the z-x plane, a magnetic field in the y-axis direction is generated in the loop by the current of the input-side loop antenna 31. At resonance, for example, an electromagnetic field as shown in FIG. 3 is excited. Here, for example, when the loop plane is tilted about 45 degrees around the x-axis, the magnetic field in the loop will have not only a component in the y-axis direction but also a component in the z-axis direction. A resonance mode in which the magnetic field refluxes in the z-x plane and the electric field is directed in the y-axis direction is excited.

[0028] When the three sides of the length, width, and depth of the microwave resonator 3 are made to have different lengths from each other, generally the resonance frequencies of the respective resonance modes are different. Therefore, it is possible to excite or receive a plurality of resonance modes with different electric field directions using a pair of antennas. Further, it is also possible to separately measure the resonance frequencies.

[0029] A plurality of pairs of antennas may be provided in the microwave resonator 3, such as by providing an antenna pair on the upper and lower surfaces and using a resonance mode in which the electric field is directed in the y-axis direction. As a result, it is also possible to use a plurality of resonance modes simultaneously. Note that it is not essential to provide the antenna pair on the opposing surfaces, and the antenna pair may be arranged on the same surface or an orthogonal surface as long as it is arranged to couple with the magnetic field of the resonance mode. Since the loop antenna couples with the magnetic field, an antenna by electric field coupling in which the center wire of the coaxial line protrudes into the resonator by an appropriate length may also be used.

[0030] Based on the above, an explanation will be given while referring to FIGS. 1 to 3 together.

[0031] In the measurement of the resonance frequency, it is widely performed to search for the frequency at which the intensity of the output signal transmitted through the resonator is maximized by sweeping the frequency of the input signal, such as with a VNA (vector network analyzer). Not only the amplitude but also the phase may be used.

[0032] The frequency resolution, that is, the resolution bandwidth, is approximately the reciprocal of the measurement time. When measuring the resonance frequency of a resonator, it is necessary to measure with a resolution of 1 / several times or less of the resonance linewidth. However, depending on the frequency change to be detected, a higher frequency resolution may be required. Therefore, the frequency resolution is determined according to the resonance linewidth of the target microwave resonator 3 and the frequency change to be detected. And the reciprocal of the frequency resolution is approximately the measurement time required per frequency measurement point.

[0033] When using a single-tone VNA, the measurement time becomes relatively long, while the frequency characteristics of a resonator and the like can be measured with a high SN ratio of 100 dB or more.

[0034] Here, in an application where the resonance frequency of the microwave resonator 3 is measured to inspect characteristics such as the mass of an object to be measured, an SN ratio of about 40 dB is sufficient. Therefore, in an embodiment of the present invention, when measuring the resonance frequency of the microwave resonator 3, instead of a single tone, a multi-tone signal is used to simultaneously measure a plurality of frequencies under the same signal power as in the case of a single tone. Thereby, the measurement time of the resonance frequency of the microwave resonator 3 can be shortened.

[0035] In an embodiment of the present invention, for measurement using a multi-tone signal, a broadband sub-carrier modulation / demodulation technique such as OFDM is utilized. OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing and is called orthogonal frequency division multiplexing. OFDM has become widespread in terrestrial digital broadcasting, 4G / 5G mobile communications, Wi-Fi, etc., and a signal processing unit of a measurement system can also be realized using a commercially available SDR (software-defined radio) module or the like.

[0036] The modulation signal transmission unit 1 transmits an OFDM modulation signal to the microwave resonator 3. The modulation signal reception unit 2 receives the OFDM modulation signal transmitted through the microwave resonator 3 and demodulates the signal. Then, the modulation signal reception unit 2 measures a change in complex amplitude or intensity based on the demodulation result. Thereby, the transmission characteristics of the microwave resonator 3 within the band of the modulation wave can be measured at once. By performing measurement using a multi-tone signal, the measurement time of the resonance frequency can be shortened while maintaining a necessary level of SN ratio.

[0037] The modulation signal reception unit 2 calculates the characteristics of the object to be measured based on the measured change in resonance frequency. More specifically, the modulation signal reception unit 2 calculates the weight of the object to be measured based on the measured change in resonance frequency.

[0038] Note that the measured change in resonance frequency may be utilized for measurement of physical quantities other than those described above.

[0039] FIG. 4 is a conceptual diagram illustrating the spectrum of an OFDM signal. The OFDM signal has a spectrum as shown, for example, in FIG. 4. Each frequency component that appears to overlap has orthogonality. Therefore, the modulation signal receiving unit 2 can separate and detect each complex amplitude. Note that each frequency component may be called a subcarrier, bin, or tone, etc.

[0040] FIG. 5 is a block diagram showing the configuration of an OFDM modulation / demodulation system.

[0041] The OFDM transmission system is implemented in the modulation signal transmission unit 1. The modulation signal transmission unit 1 performs symbol mapping on the bit sequence and performs serial / parallel conversion. After performing IDFT processing on the parallelized information, parallel / serial conversion is performed. I / Q modulation processing is performed on the serialized signal, and an output signal transmitted to the microwave resonator 3 is obtained. Note that the transmission of the modulation signal from the modulation signal transmission unit 1 to the microwave resonator 3 may be wireless transmission.

[0042] The OFDM reception system is implemented in the modulation signal receiving unit 2. The modulation signal receiving unit 2 performs I / Q demodulation processing on the received modulation signal and performs serial / parallel conversion on the processing result. The modulation signal receiving unit 2 performs DFT processing on the parallelized information and then performs parallel / serial conversion. The modulation signal receiving unit 2 performs demapping, which is a process reverse to symbol mapping, on the serialized signal to obtain a bit sequence.

[0043] In practice, processes such as addition / removal of a guard interval and equalization processing in the OFDM reception system may be further performed, but since these are common processes for those skilled in the art with respect to OFDM, detailed descriptions are omitted.

[0044] In the case of normal communication, particularly when using phase modulation (PSK), phase synchronization (carrier synchronization) for estimating the phase of the transmission signal is performed in the receiving system. In contrast, in the present invention, similar to a VNA, the same reference signal may be distributed and used in the transmitting system and the receiving system. By doing so, not only can the receiving system be simplified, but also the influence of the phase error remaining in the phase synchronization can be prevented, and more stable measurement with lower noise can be performed.

[0045] Here, in communication and broadcasting which are general applications of OFDM, the bit sequence to be transmitted always changes. On the other hand, in applications such as the measurement of the transmission characteristics of the microwave resonator 3, the same bit sequence may be repeatedly transmitted. That is, the content of the multi-tone modulation signal transmitted from the modulation signal transmission unit 1 to the microwave resonator 3 may be the same at the first transmission time and the second transmission time.

[0046] For example, a binary pseudo-random number may be repeatedly input and subjected to primary modulation, i.e., symbol mapping processing, such as QPSK. Since PSK has a constant amplitude, it is suitable for applications of transmission characteristic measurement. That is, the modulation signal transmission unit 1 may transmit a multi-tone modulation signal obtained by performing symbol mapping processing based on a binary pseudo-random number to the microwave resonator 3.

[0047] If all tones in the multi-tone are in the same phase, a peak about 20 dB higher than the average power will appear even for 128 tones. However, by appropriately dispersing the phases of each tone using a random number, the PAPR (peak-average power ratio) can be made 10 dB or less with a high probability. In this case, the demapping process in the OFDM receiving system becomes unnecessary, and the absolute value or intensity of the complex amplitude of each tone is calculated after the DFT process or the parallel / serial conversion process.

[0048] In the modulation signal receiving unit 2, the reception intensity of each tone is measured in advance with the output directly connected, using the reference value or calibration value, and the reference value or calibration value is stored in the storage unit. During actual measurement, the reception intensity when transmitting the modulation signal from the modulation signal transmitting unit 1 to the microwave resonator 3 is measured, and the reference value is subtracted on the modulation signal receiving unit 2 side. Thereby, the transmission characteristics are obtained. Even when using a multi-tone signal, similar to the case of using a single-tone VNA, the complex transmission characteristics may be calculated based on the ratio between the reference value and the measured value of the complex amplitude.

[0049] In particular, by repeatedly inputting binary pseudo-random numbers and performing primary modulation, i.e., symbol mapping processing, such as QPSK, it is possible to prevent the peak power from becoming large relative to the average power. Thereby, the modulation signal transmitted from the modulation signal transmitting unit 1 to the microwave resonator 3 can be prevented from becoming a pulsed signal.

Example

[0050] Assume the following measurement conditions. · Resonance frequency: 5 GHz ± 10% (4.5 GHz - 5.5 GHz) · Measurement bandwidth: 1 GHz · Q value: 500 · Resonance linewidth: 10 MHz · Resonance frequency change to be detected: 0.1 MHz · Frequency resolution: 0.1 MHz (a value sufficiently smaller than the resonance linewidth) · Number of frequency points: 10000 (measurement bandwidth / frequency resolution) · Measurement time per point: 10 μs (reciprocal of the frequency resolution)

[0051] [When measured with a single tone] · SNR (ideal value): 124 dB · Input signal: 0 dBm · Thermal noise: -124 dBm (-174 dBm / Hz × 0.1 MHz) · Total measurement time: 100 ms (10 μs × 10000) Note that the total measurement time means the sweep time of the VNA. Even if power consumption is reduced and the SNR is lowered, in the case of a single tone, the observation time cannot be shortened.

[0052] [When measured with multi-tone (10,000 tones)] · SNR (ideal value): 74 dB · Input signal: -10 dBm (with PAPR of 10 dB and peak power of 0 dBm) · Thermal noise: -84 dBm (-174 dBm / Hz × 1 GHz) (When viewed per tone, -50 dBm / -124 dBm) · Total measurement time: 10 μs

[0053] As described above, when measured with multi-tone, the measurement time is shortened to 1 / 10,000 of that of a single tone. The SNR decreases by 50 dB including the margin for PAPR.

[0054] When measuring with multi-tone, if it is difficult to use 10,000 tones, the measurement process may be appropriately divided, such as sweeping 200 tones (20 MHz bandwidth) in 50 steps. Even in this case, the measurement time is shortened to 1 / 200 compared to the case of measuring with a single tone.

[0055] Note that if the application is limited to resonance frequency measurement, another method of shortening the measurement time can be considered, such as sweeping only a range about several times the resonance linewidth and following the change in the resonance frequency.

[0056] Also, measurements based on multi-tone signals can be used for applications other than resonance frequency measurement. For example, the modulation signal transmission unit 1 inputs a modulation signal to the microwave resonator 3. The modulation signal reception unit 2 receives and analyzes the signal transmitted through it. The modulation signal reception unit 2 may perform reflection / transmission characteristic measurement based on the analysis result.

[0057] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is obvious that those skilled in the art can conceive of various modifications or corrections within the scope described in the claims, and it is naturally understood that they also belong to the technical scope of the present disclosure. For example, each step in the method according to the present disclosure may be executed in any order as long as there is no contradiction. Also, within the scope not departing from the spirit of the disclosure, the components in the above embodiments may be arbitrarily combined.

Explanation of Reference Signs

[0058] 1 Modulation signal transmission unit 2 Modulation signal reception unit 3 Microwave resonator 31 Input side loop antenna 32 Output side loop antenna 33 Object to be measured inlet 34 Object to be measured outlet 4 Object to be measured 100 Measuring device

Claims

1. A measuring device comprising a modulation signal transmitting unit (1) and a modulation signal receiving unit (2), wherein the modulation signal transmitting unit transmits a predetermined multi-tone modulation signal with a known spectrum to a microwave resonator (3) in which a measurement object (4) is disposed and used inside thereof, the modulation signal receiving unit, receives the multi-tone modulation signal output from the microwave resonator, calculates the transmission characteristics of the measurement object by comparing the spectrum of the multi-tone modulation signal transmitted by the modulation signal transmitting unit to the microwave resonator with the spectrum of the multi-tone modulation signal received by the modulation signal receiving unit, calculates the resonance frequency of the microwave resonator based on the calculated transmission characteristics, Measuring device.

2. The modulation signal receiving unit, calculates the weight of the measurement object based on the calculated resonance frequency, The measuring device according to claim 1.

3. The modulation signal transmitting unit transmits a multi-tone modulation signal modulated based on OFDM to the microwave resonator, The measuring device according to claim 1.

4. The modulation signal transmitting unit transmits a multi-tone modulation signal obtained by performing symbol mapping processing based on binary pseudo-random numbers to the microwave resonator, The measuring device according to claim 1.

5. The content of the multi-tone modulation signal transmitted by the modulation signal transmitting unit to the microwave resonator is the same at the first transmission time and the second transmission time, The measuring device according to claim 1.

6. A measurement method by a measuring device comprising a modulation signal transmitting unit (1) and a modulation signal receiving unit (2), comprising: a step of the modulation signal transmitting unit transmitting a predetermined multi-tone modulation signal with a known spectrum to a microwave resonator (3) in which a measurement object (4) is disposed and used inside thereof; a step of the modulation signal receiving unit receiving the multi-tone modulation signal output from the microwave resonator; a step of the modulation signal receiving unit calculating the transmission characteristics of the measurement object by comparing the spectrum of the multi-tone modulation signal transmitted by the modulation signal transmitting unit to the microwave resonator with the spectrum of the multi-tone modulation signal received by the modulation signal receiving unit; a step of the modulation signal receiving unit calculating the resonance frequency of the microwave resonator based on the calculated transmission characteristics; Measurement method having.

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