Measuring device and measuring 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 that utilize microwave resonance. [Background technology]

[0002] When a small dielectric object such as a tablet is placed in a part of a microwave resonator, the resonant frequency and resonant linewidth change compared to when no dielectric is present. This change in resonant frequency and resonant linewidth is used to measure the characteristics of the object. The characteristics of the object include, for example, weight. For example, such a measuring device is used in an object inspection device that checks whether the weight or volume of manufactured objects is within specifications.

[0003] Patent Document 1 describes an article inspection device. The article inspection device described in Patent Document 1 includes a conveying rotor that is disposed below a supplying means for supplying articles, rotates on a horizontal axis, and accommodates and conveys articles dropped from the supplying means in a recessed portion on its outer periphery. The article inspection device includes a guide wall that is disposed along the outer periphery of the conveying rotor and closes the opening of the recessed portion, which moves as the conveying rotor rotates. The guide wall, together with the recessed portion, defines a conveying chamber, the end position of which is the discharge position for the articles. The article inspection device also includes an inspection means that is disposed below the conveying rotor and on which articles discharged from the end position are placed. The recessed portion is formed in a slit shape with a predetermined length that allows the articles to move in the outer periphery along the rotational direction of the conveying rotor. The recessed portion has a front wall that hits the articles at the front side in the direction of movement of the articles due to gravity as the conveying rotor rotates, and a rear wall that pushes the articles out of the inspection means at the rear side in the direction of movement of the articles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-74073 Summary of the Invention [Problem to be solved by the invention]

[0005] A known method for measuring the characteristics of small objects is to use a VNA (Vector Network Analyzer) or the like to sweep a single tone signal and measure the transmission characteristics of a microwave resonator.

[0006] Here, if the required measurement accuracy can be obtained, generally, a shorter measurement time is more useful, and is considered to be 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 of the present invention is to provide a measurement device and a measurement method that are capable of measuring signal characteristics that indicate the features of an object in a shorter time. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the measurement device and the measurement method according to the present invention are characterized by the following [1] to [6]. [1] A modulated signal transmitting unit (1) and a modulated signal receiving unit (2) are provided, the modulated signal transmitting unit transmits a predetermined multi-tone modulated signal having a known spectrum to a microwave resonator (3) in which an object to be measured (4) is placed; The modulated signal receiving unit receiving a multi-tone modulated signal output from the microwave resonator; calculating a transmission characteristic of the device under test by comparing a spectrum of the multi-tone modulated signal transmitted to the microwave resonator by the modulated signal transmitter with a spectrum of the multi-tone modulated signal received by the modulated signal receiver; calculating a resonant frequency of the microwave resonator based on the calculated transmission characteristic; Measuring equipment. [2] The modulated signal receiving unit calculating a weight of the object to be measured based on the calculated resonant frequency; [1] The measuring device according to the present invention. [3] the modulated signal transmitter transmits a multi-tone modulated signal modulated based on OFDM to the microwave resonator; [1] The measuring device according to the present invention. [4] the modulated signal transmitter transmits a multi-tone modulated signal obtained by performing symbol mapping processing based on a binary pseudorandom number to the microwave resonator; [1] The measuring device according to the present invention. [5] the content of the multi-tone modulated signal transmitted by the modulated signal transmitter to the microwave resonator is the same during the first transmission and the second transmission; [1] The measuring device according to the present invention. [6] A microwave measurement method using a measurement device including a modulated signal transmitter (1) and a modulated signal receiver (2), a step in which the modulated signal transmitting unit transmits a predetermined multi-tone modulated signal having a known spectrum to a microwave resonator (3) in which an object to be measured (4) is disposed; a step in which the modulated signal receiving unit receives a multi-tone modulated signal output from the microwave resonator; the modulated signal receiving unit calculating the transmission characteristics of the device under test by comparing the spectrum of the multi-tone modulated signal transmitted to the microwave resonator by the modulated signal transmitting unit with the spectrum of the multi-tone modulated signal received by the modulated signal receiving unit; a step in which the modulated signal receiving unit calculates a resonant frequency of the microwave resonator based on the calculated transmission characteristic; A measurement method comprising:

[0009] According to the configuration [1] above, it is possible to provide a measurement device that can measure the resonant frequency of a microwave resonator, which changes depending on the transmission characteristics of an object to be measured, in a shorter time. According to the configuration [2] above, it is possible to provide a measuring device that can measure the physical property characteristics of an object to be measured, such as its weight, in a shorter time based on the resonant frequency detected in a shorter time. According to the configuration of [3] above, part of the technology related to OFDM signal processing, which is widespread in the field of wireless communications, can be applied to measuring the resonant frequency of a microwave resonator. According to the configuration [4] above, the peak power relative to the average power of the multi-tone modulated signal can be suppressed to a predetermined value or less with a high probability. According to the configuration of [5] above, the modulated signal transmitting unit can repeatedly input binary pseudorandom numbers to the modulated signal transmitting unit, and transmit a multi-tone modulated signal that has undergone symbol mapping processing using QPSK or the like to the microwave resonator. According to the configuration [6] above, it is possible to provide a measurement method that can measure the resonant frequency of a microwave resonator, which changes depending on the transmission characteristics of an object to be measured, in a shorter time. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a measurement device and a measurement method that can measure signal characteristics that indicate the characteristics of an object in a shorter time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram illustrating an example of the configuration of a measurement device according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a conceptual diagram illustrating a microwave resonator used in a measurement device according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a conceptual diagram illustrating a microwave resonator used in a measurement device according to an embodiment of the present disclosure. [Figure 4] 1 is a conceptual diagram illustrating the spectrum of an OFDM signal. [Figure 5] FIG. 1 is a block diagram showing the configuration of an OFDM modulation / demodulation system. DETAILED DESCRIPTION OF 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 an example of the configuration of a measurement device according to an embodiment of the present disclosure.

[0014] The measuring device 100 determines the physical characteristics of an object such as a small item using a microwave resonant frequency, and includes a modulated signal transmitter 1 and a modulated signal receiver 2. The modulated signal transmitter 1 has a function of transmitting a modulated signal to a microwave resonator 3. The modulated signal receiver 2 has a function of receiving a modulated signal from the microwave resonator 3. The microwave resonator 3 may be incorporated into the measuring device 100, or the measuring device 100 and the microwave resonator 3 may be separate entities.

[0015] The modulated signal transmitter 1 transmits a multi-tone modulated 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 the programs executed by the control unit and various data used during execution. The storage unit may include a HDD, ROM, 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 measurement device 100 refers to a program stored in the storage unit and executes the program, thereby functionally realizing a modulated signal transmitting unit 1 and a modulated signal receiving unit 2.

[0019] The modulated signal transmitter 1 transmits a modulated signal to the microwave resonator 3. The modulated signal that has passed through the microwave resonator 3 is received and analyzed by the modulated signal receiver 2. More specifically, the signal transmitted from the modulated signal transmitter 1 to the microwave resonator 3 is a predetermined modulated signal with a known spectrum. The modulated signal that passes through the microwave resonator 3 is received by the modulated signal receiver 2 and its spectrum is analyzed. The modulated signal receiver 2 calculates the transmission characteristics of the device under test by comparing the spectrum of the received modulated signal with the spectrum of the modulated signal transmitted from the modulated signal transmitter 1 to the microwave resonator 3. The device under test is a small object placed inside the microwave resonator 3. An example of a small object is a tablet, but the small object is not limited to a tablet. The modulated signal receiver 2 calculates the resonant frequency of the microwave resonator 3 based on the calculated transmission characteristics. For modulation, for example, ODFM with phase modulation such as QPSK as the primary modulation may be used. Note that the binary pseudorandom numbers in the figure will be described later.

[0020] FIG. 2 is a conceptual diagram illustrating a microwave resonator used in a measurement device 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, and It has an inlet 33 for an object to be measured and an outlet 34 for an object to be measured. The microwave resonator 3 has a generally rectangular outer shape. However, the outer shape of the microwave resonator 3 may be other than rectangular.

[0022] The object to be measured is put into an inlet 33 for the object to be measured of the microwave resonator 3 and is discharged from an outlet 34 for the object to be measured.

[0023] Examples of methods for putting in and taking out the object to be measured include the following. - Shoot the object to be measured using an air gun or similar. The microwave resonator 3 is arranged so that the inlet 33 for the object to be measured and the outlet 34 for the object to be measured are aligned vertically downward, and the object to be measured is allowed to fall freely from the inlet 33 for the object to be measured. The belt of the belt conveyor is passed from the inlet 33 for the object to be measured to the outlet 34 for the object to be measured, and the object to be measured is transported by the belt conveyor.

[0024] When a dielectric such as a tablet, which is an object to be measured, is placed in a part of the microwave resonator 3, the resonant frequency and resonant linewidth of the microwave resonator 3 change compared to when the dielectric is not placed. Similarly, when a dielectric is placed near a resonator based on a transmission line formed on a substrate, the resonant frequency and resonant linewidth change. These changes in resonant frequency and resonant linewidth are used to measure the characteristics of the object to be measured. The characteristics of the object to be measured refer to, for example, weight, but may also be characteristics other than weight. For example, the modulated signal receiving unit 2 can determine the characteristics of the dielectric object to be measured based on the relationship between the change in resonant frequency due to the presence or absence of a dielectric or a change in composition such as moisture content and the volume, relative dielectric constant, dielectric loss tangent (dielectric loss), etc. of the dielectric, which have been measured in advance.

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

[0026] For ease of explanation, a Cartesian coordinate system consisting of x, y, and z axes is shown in Fig. 3. In Fig. 3, the electric field is shown by a bold solid line, and the magnetic field is shown by a bold dashed line.

[0027] If the loop plane is taken to be the zx plane, the current in the input loop antenna 31 generates a magnetic field in the y-axis direction inside the loop. At resonance, an electromagnetic field such as that shown in Figure 3 is excited. Here, for example, if the loop plane is tilted about 45 degrees around the x-axis, the magnetic field inside the loop will have a z-axis component in addition to the y-axis component, and the magnetic field will circulate within the zx plane, exciting a resonance mode in which the electric field is oriented in the y-axis direction.

[0028] When the three sides (length, width, and depth) of the microwave resonator 3 are different in length, the resonant frequencies of the respective resonant modes generally differ, so it is possible to excite or receive multiple resonant modes with different electric field directions with a pair of antennas. It is also possible to measure the resonant frequencies separately.

[0029] Multiple pairs of antennas may be provided in the microwave resonator 3, such as providing antenna pairs on the top and bottom surfaces to use a resonance mode in which the electric field is oriented in the y-axis direction. This makes it possible to use multiple resonance modes simultaneously. Note that it is not essential to provide the antenna pairs on opposite surfaces, and antenna pairs may be arranged on the same surface or perpendicular surfaces as long as they are arranged to couple with the magnetic field of the resonance mode. While a loop antenna couples with a magnetic field, an antenna using electric field coupling, in which the core wire of a coaxial cable is protruded into the resonator by an appropriate length, may also be used.

[0030] Based on the above, the following description will be given with reference to FIGS.

[0031] In measuring the resonant frequency, it is common to use a VNA (Vector Network Analyzer) to sweep the frequency of the input signal and find the frequency at which the strength of the output signal transmitted through the resonator is at its maximum. In addition to amplitude, phase may also be used.

[0032] The frequency resolution, or resolution bandwidth, is approximately the reciprocal of the measurement time. When measuring the resonant frequency of a resonator, it is necessary to measure with a resolution of a fraction of the resonant linewidth or less. However, depending on the frequency change you want to detect, a higher frequency resolution may be required. Therefore, the frequency resolution is determined according to the resonant linewidth of the microwave resonator 3 in question and the frequency change you want to detect. The reciprocal of the frequency resolution is then the approximate measurement time required per frequency measurement point.

[0033] Although the measurement time is relatively long when using a single-tone VNA, it is possible to measure the frequency characteristics of resonators and the like with a high S / N ratio of 100 dB or more.

[0034] Here, in the case of measuring the resonant frequency of the microwave resonator 3 to inspect the characteristics of an object such as the mass, an SNR of about 40 dB is sufficient. Therefore, in the embodiment of the present invention, when measuring the resonant frequency of the microwave resonator 3, a multi-tone signal is used instead of a single tone, and multiple frequencies are measured simultaneously with the same signal power as in the case of a single tone. This makes it possible to shorten the measurement time for the resonant frequency of the microwave resonator 3.

[0035] In an embodiment of the present invention, measurements using multi-tone signals utilize wideband subcarrier modulation and demodulation technology such as OFDM. OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. OFDM is widely used in terrestrial digital broadcasting, 4G / 5G mobile communications, Wi-Fi, etc., and the signal processing section of the measurement system can also be realized using a commercially available SDR (software defined radio) module.

[0036] The modulated signal transmitter 1 transmits an OFDM-modulated signal to the microwave resonator 3. The modulated signal receiver 2 receives the OFDM-modulated signal that has passed through the microwave resonator 3 and demodulates the signal. The modulated signal receiver 2 then measures changes in complex amplitude or intensity based on the demodulation results. This makes it possible to measure the transmission characteristics of the microwave resonator 3 within the band of the modulated wave all at once. By using a multi-tone signal for measurement, it is possible to shorten the measurement time for the resonant frequency while maintaining the required SNR.

[0037] The modulated signal receiving unit 2 calculates the characteristics of the object based on the measured change in the resonant frequency, and more specifically, calculates the weight of the object based on the measured change in the resonant frequency.

[0038] The measured change in the resonant frequency may be used to measure physical quantities other than those mentioned above.

[0039] FIG. 4 is a conceptual diagram illustrating an example of the spectrum of an OFDM signal. An OFDM signal has a spectrum such as that shown in FIG. 4. The frequency components that appear to overlap are orthogonal. Therefore, the modulated signal receiver 2 can separate and detect each complex amplitude. Each frequency component may be called a subcarrier, bin, or tone.

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

[0041] The OFDM transmission system is implemented in a modulated signal transmitter 1. The modulated signal transmitter 1 performs symbol mapping on the bit string and performs serial-to-parallel conversion. The parallelized information is subjected to IDFT processing and then parallel-to-serial conversion. The serialized signal is subjected to I / Q modulation processing to obtain an output signal that is sent to the microwave resonator 3. Note that the modulated signal may be transmitted from the modulated signal transmitter 1 to the microwave resonator 3 wirelessly.

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

[0043] In reality, further processing such as adding / removing guard intervals and equalization processing in the OFDM receiving system may be performed, but since these are common processes for OFDM known to those skilled in the art, detailed explanations will be omitted.

[0044] In normal communications, especially when phase-shift keying (PSK) is used, phase synchronization (carrier synchronization) is performed in the receiving system to estimate the phase of the transmitted signal. In contrast, in the present invention, the same reference signal is distributed and used in the transmitting and receiving systems, just like in a VNA. This not only simplifies the receiving system, but also prevents the influence of phase errors that remain in phase synchronization, enabling lower-noise, more stable measurements.

[0045] In communications and broadcasting, which are common applications of OFDM, the transmitted bit string is constantly changing. On the other hand, in applications such as measuring the transmission characteristics of microwave resonator 3, the same bit string may be transmitted repeatedly. In other words, the content of the multi-tone modulated signal transmitted by modulated signal transmitter 1 to microwave resonator 3 may be the same during the first transmission and the second transmission.

[0046] For example, binary pseudorandom numbers can be repeatedly input and primary modulation, i.e., symbol mapping processing, can be performed using QPSK or the like. PSK has a constant amplitude, making it suitable for measuring transmission characteristics. In other words, the modulated signal transmitter 1 can transmit to the microwave resonator 3 a multi-tone modulated signal obtained by symbol mapping processing based on the binary pseudorandom numbers.

[0047] If all the tones in a multi-tone signal are in phase, even with 128 tones, a peak about 20 dB higher than the average power will appear. However, by appropriately distributing the phase of each tone using random numbers, it is possible to keep the PAPR (peak-to-average power ratio) below 10 dB with a high probability. In this case, demapping processing is not required in the OFDM receiving system, and the absolute value or intensity of the complex amplitude of each tone is calculated after DFT processing or parallel-to-serial conversion processing.

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

[0049] In particular, by repeatedly inputting binary pseudorandom numbers and performing primary modulation, i.e., symbol mapping processing, using QPSK or the like, it is possible to prevent peak power from becoming large relative to average power, thereby preventing the modulated signal transmitted from modulated signal transmitter 1 to microwave resonator 3 from becoming a pulsed signal. [Example]

[0050] Assume that the measurement conditions are as follows: ·Resonance frequency: 5GHz±10% (4.5GHz - 5.5GHz) Measurement bandwidth: 1GHz Q value: 500 Resonant linewidth: 10MHz Change in resonant frequency to be detected: 0.1MHz Frequency resolution: 0.1MHz (sufficiently smaller than the resonance linewidth) Number of frequency points: 10,000 (measurement bandwidth / frequency resolution) Measurement time per point: 10 μs (inverse of frequency resolution)

[0051] [Measured with a single tone] Ideal signal-to-noise ratio: 124dB Input signal: 0dBm Thermal noise: -124dBm (-174dBm / Hz × 0.1MHz) Total measurement time: 100 ms (10 μs × 10000) The total measurement time means the sweep time of the VNA. Even if the SNR is reduced by saving power, the observation time cannot be shortened in the case of a single tone.

[0052] [When measured with multi-tone (10,000 tones)] Ideal signal-to-noise ratio: 74dB Input signal: -10dBm (PAPR is 10dB, peak power is 0dBm) Thermal noise: -84dBm (-174dBm / Hz × 1GHz) (-50dBm / -124dBm per tone) Total measurement time: 10 μs

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

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

[0055] If the application is limited to resonant frequency measurement, other methods for shortening the measurement time can be considered, such as sweeping only a range several times the resonant linewidth and following the change in the resonant frequency.

[0056] Furthermore, measurements based on multi-tone signals can be used for purposes other than resonant frequency measurement. For example, a modulated signal transmitter 1 inputs a modulated signal to a microwave resonator 3. The modulated signal receiver 2 receives and analyzes the transmitted signal. Based on the analysis results, the modulated signal receiver 2 may measure reflection and transmission characteristics.

[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 clear to those skilled in the art that various modifications and alterations can be made within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. For example, the steps in the methods disclosed herein may be performed in any order as long as no contradictions arise. Furthermore, the components in the above embodiments may be combined in any order as long as they do not deviate from the spirit of the disclosure. [Explanation of symbols]

[0058] 1. Modulation signal transmitter 2. Modulation signal receiver 3 Microwave resonator 31 Input loop antenna 32 Output loop antenna 33 Measured object inlet 34 Measured object outlet 4 Object to be measured 100 Measuring Device

Claims

1. A modulation signal transmitting unit (1) and a modulation signal receiving unit (2) are provided, The modulated signal transmitting unit transmits a predetermined multi-tone modulated signal having a known spectrum to a microwave resonator (3) in which an object to be measured (4) is placed; The modulated signal receiving unit receiving a multi-tone modulated signal output from the microwave resonator; calculating a transmission characteristic of the device under test by comparing a spectrum of the multi-tone modulated signal transmitted to the microwave resonator by the modulated signal transmitter with a spectrum of the multi-tone modulated signal received by the modulated signal receiver; calculating a resonant frequency of the microwave resonator based on the calculated transmission characteristic; Measuring equipment.

2. The modulated signal receiving unit calculating a weight of the object to be measured based on the calculated resonant frequency; The measuring device according to claim 1 .

3. the modulated signal transmitter transmits a multi-tone modulated signal modulated based on OFDM to the microwave resonator; The measuring device according to claim 1 .

4. the modulated signal transmitter transmits a multi-tone modulated signal obtained by performing symbol mapping processing based on a binary pseudorandom number to the microwave resonator; The measuring device according to claim 1 .

5. the content of the multi-tone modulated signal transmitted by the modulated signal transmitter to the microwave resonator is the same during the first transmission and the second transmission; The measuring device according to claim 1 .

6. A measurement method using a measurement device comprising a modulated signal transmitting unit (1) and a modulated signal receiving unit (2), a step in which the modulated signal transmitting unit transmits a predetermined multi-tone modulated signal having a known spectrum to a microwave resonator (3) in which an object to be measured (4) is placed; a step in which the modulated signal receiving unit receives a multi-tone modulated signal output from the microwave resonator; the modulated signal receiving unit calculating the transmission characteristics of the device under test by comparing the spectrum of the multi-tone modulated signal transmitted to the microwave resonator by the modulated signal transmitting unit with the spectrum of the multi-tone modulated signal received by the modulated signal receiving unit; a step in which the modulated signal receiving unit calculates a resonant frequency of the microwave resonator based on the calculated transmission characteristic; A measurement method comprising:

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