CN105021885A - Frequency tracking measurement device for microwave resonant cavity - Google Patents
Frequency tracking measurement device for microwave resonant cavity Download PDFInfo
- Publication number
- CN105021885A CN105021885A CN201510250973.5A CN201510250973A CN105021885A CN 105021885 A CN105021885 A CN 105021885A CN 201510250973 A CN201510250973 A CN 201510250973A CN 105021885 A CN105021885 A CN 105021885A
- Authority
- CN
- China
- Prior art keywords
- frequency
- signal
- circuit
- resonance
- microwave
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Measurement Of Resistance Or Impedance (AREA)
Abstract
The invention relates to microwave technology, sensors, and frequency measurement and provides a frequency tracking measurement device for a microwave resonant cavity. The frequency tracking measurement device may greatly reduce cost of measuring the frequency of the microwave resonant cavity, guarantees high measurement precision with a stable electric output signal, and prevents two main defects of a network analyzer in a microwave resonant cavity test. Accordingly, a technical scheme utilized by the invention is that the frequency tracking measurement device for the microwave resonant cavity comprises an amplitude discriminating circuit, a phase discriminating circuit, a digital-to-analog converting circuit , a voltage-controlled oscillator, a circulator, the microwave resonant cavity, a detector, and a control circuit; a waveguide signal is input into the microwave resonant cavity; a reflection signal generated by the reflection of the microwave resonant cavity is output to the circulator via the detector to be selected; a selected signal enters the amplitude discriminating circuit and the phase discriminating circuit. The frequency tracking measurement device is mainly used in frequency measurement.
Description
Technical field
The present invention relates to microwave technology, sensor, frequency measurement.Specifically, the frequency-tracing measurement device of microwave cavity is related to.
Background technology
The advantages such as microwave cavity, as a kind of sensor based on microwave technology, has loss little, and Q value is high, and frequency selectivity is good, and power capacity is large and firm in structure.Main to realize the resonance of microwave region, for frequency meter, oscillator, microwave signal source, microwave filter and resonance amplifier etc.Relate to (as document [1]-[5]) in the field of microwave cavity many, the mensuration for the frequency of microwave cavity adopts network analyzer directly to measure the S parameter of resonator cavity more, obtains resonator cavity frequency.Network analyzer is to obtain the data reflection obtaining microwave cavity frequency while S parameter directly perceived not, and calibration curve information precision is not high and cannot obtain the information such as difference or variable quantity; And network analyzer equipment price is expensive, cost is higher.The application that network analyzer measures frequency and analyze in part microwave cavity is limited with above two features of network analyzer survey frequency.
In the system of microwave cavity as sensor measurement frequency, replaced the use of network analyzer by circuit design, also can significantly reduce costs carrying high-precision while, but have no mature technology report in this respect.
Summary of the invention
For overcoming the deficiencies in the prior art, provide the frequency-tracing measurement device of microwave cavity, this device significantly can reduce the cost measuring microwave cavity frequency, and ensures higher measuring accuracy with stable electrical output signal.Avoid two the main deficiencies of network analyzer in microwave cavity frequency test.For this reason, the technical scheme that the present invention takes is, the frequency-tracing measurement device of microwave cavity, comprise: amplitude discrimination circuit, phase identification of circuit, D/A converting circuit, voltage controlled oscillator, circulator, microwave cavity, wave detector, control circuit forms, input waveguide signal enters resonator cavity, undertaken reflecting the reflected signal produced by resonator cavity to output to circulator through wave detector and select, first signal enters in amplitude discrimination circuit, in amplitude discrimination circuit, output signal is converted to binary signal 0, 1 and be input to control circuit, control circuit is by 0, 1 signal judges whether resonator cavity resonance occurs, if resonance, then directly enter frequency detecting part, if there is no resonance, then returning said process, making resonator cavity reflected signal by selecting after wave detector and circulator to enter phase identification of circuit,
Phase identification of circuit carries out phase place qualification to the resonator cavity reflected signal after wave detector process, exports 0,1 signal and is sent to control circuit, and control circuit loads input waveguide frequency higher or lower than resonator cavity actual frequency by acquisition 0,1 input; Control circuit is added and subtracted input waveguide signal frequency by D/A converting circuit conversion and control voltage controlled oscillator, to approach resonator cavity actual frequency, after completing this process, then repeats with cocycle, until detect true resonance frequency f.
Amplitude discrimination circuit comprises low-pass filter, amplifier and comparer, comparer arranges reference voltage and judges amplitude, input signal enters comparer and compares after low-pass filter, amplifier, be less than reference voltage then current state be resonant condition, be greater than reference voltage then current state be non-resonant condition.
Phase identification of circuit comprises multiplier, low-pass filter and comparer, after multiplier process after filtering, the output signal of plus or minus represents homophase or anti-phase, signal frequency through microwave cavity is greater than resonance frequency then homophase, comparator reference voltage is set to zero, exports " 1 " and represents that ongoing frequency is greater than resonance frequency, export " 0 " and then represent that ongoing frequency is less than resonance frequency, binary message feeds back to D/A converting circuit and carries out feedback regulation, finally realizes rate-adaptive pacemaker.
Control circuit is realized by field programmable gate array.
Compared with the prior art, technical characterstic of the present invention and effect:
The frequency-tracing measurement device of microwave cavity of the present invention, controls to replace the method for network analyzer by the S parameter acquisition resonator cavity frequency of test microwave cavity by circuit design and FPGA platform.Have higher precision and accuracy, cost significantly reduces.
Accompanying drawing explanation
The measuring system block diagram that Fig. 1 controls based on FPGA.
Fig. 2 module one: amplitude discrimination circuit figure.
Fig. 3 amplitude identification result figure.In figure, the voltage amplitude under voltage amplitude (b) the off resonance state under (a) resonant condition.
Fig. 4 module two: phase identification of circuit figure.
Fig. 5 phase place identification result figure.In figure, (a) reflected signal frequency is greater than source signal frequency plot figure, and (b) reflected signal frequency is greater than source signal frequency plot figure.
Embodiment
The present invention proposes a kind of circuit realiration device of frequency-tracing measurement of microwave cavity, by FPGA platform reception, control circuit signal, to reach the object of following the trail of and determining microwave cavity frequency.By using compact processor and circuit significantly to reduce the cost measuring microwave cavity frequency, and ensure higher measuring accuracy with stable electrical output signal.Avoid two the main deficiencies of network analyzer in microwave cavity frequency test.
The present invention can be applicable to measure material parameter by microwave cavity, by adding the measured material of different parameters, quality in microwave cavity, by there is resonance, frequency information is gone out from tracking measurement circuit transmission, repeatedly the database of quality and frequency is set up in test, realizes material property extracting.
Microwave cavity frequency-tracing measurement system comprise fpga chip, amplitude discrimination circuit (module one, as shown in Figure 2), phase identification of circuit (module two, as shown in Figure 4), a few part of microwave component such as voltage controlled oscillator.Microwave cavity under resonant condition, by being converted into binary signal in frequency signal transmission to modular circuit through FPGA parametric controller controlling and adjustment, finally detecting the frequency of microwave cavity and exports.
Whole signal flow explaination is as follows:
Add solution in resonator cavity after, first the input waveguide signal loaded enters resonator cavity, reflected by resonator cavity, after reflected signal enters wave detector, selected by circulator, first signal enters in module one, and in module one, output signal is converted to binary signal 0,1 and is input to FPGA platform, by 0,1 signal, FPGA judges whether resonator cavity resonance occurs.If resonance, then directly enter frequency detecting part; If there is no resonance, then returning said process, making resonator cavity reflected signal by selecting after wave detector and circulator to enter module two: phase identification of circuit.
Phase identification of circuit carries out phase place qualification to the resonator cavity reflected signal after wave detector process.Export 0,1 signal and be sent to FPGA, FPGA loads input waveguide frequency higher or lower than resonator cavity actual frequency by acquisition 0,1 input.FPGA is added and subtracted by the nearly input waveguide signal frequency of DAC conversion and control voltage controlled oscillator, to approach resonator cavity actual frequency.After completing this process, then repeat with cocycle, until detect true resonance frequency f.
Frequency detecting part: because resonant frequency is too high, not easily measure, therefore obtain resonator cavity frequency by survey frequency skew.Carrying out trace by module one and module two pairs of resonator cavity actual frequencies and after detecting actual frequency, in voltage controlled oscillator, retaining the frequency f signal of resonator cavity, the resonant frequency signal f that reference signal is resonator cavity when being cavity
0, two kinds of signals enter mixer output signal difference, measure the difference obtained and output to computing machine by FPGA.
Source signal is the original signal of input resonator, and reflected signal is the output signal after resonator cavity reflection.If when frequency test signal is less than true resonance chamber frequency, source signal is contrary with resonator cavity reflected signal phase place, if when frequency test signal is greater than true resonance chamber frequency, source signal is identical with resonator cavity reflected signal phase place.After by module one, detect that resonator cavity resonance does not occur, in module two phase discriminator circuit, source signal and test signal are loaded in MC1406, relatively two signal phase information, when reflected signal frequency is greater than source signal frequency, the two phase place is identical, and output is a voltage signal being greater than 0V, as shown in Fig. 5 (a); When reflected signal frequency is less than source signal frequency, the two phase place is contrary, and output is a voltage signal being less than 0V, as shown in Fig. 5 (b).Voltage signal compares with the 0V reference voltage of LM339, by exporting binary signal 1,0 with door.If frequency test signal is less than resonance frequency, output port exports 0; If be greater than resonance frequency by measured frequency, output port exports 1, and output signal is sent to FPGA parametric controller, and FPGA controls voltage controlled oscillator (VCO) by DAC (digital-to-analog conversion) and adjusts frequency.
FPGA in the present invention only as a parametric controller, use fpga chip processor to the signal that modules exports carry out process also return signal in module or computing machine.
(1) microwave cavity is as survey sensor, has higher measurement sensistivity.Different microwave cavity types and size have different resonance frequencies, and only have and make resonator cavity reach resonance frequency by adjusting the waveguide of importing resonator cavity into, microwave cavity just can output port export resonance reflected signal.In microwave cavity, add container deposit the resonance frequency that different materials can change microwave cavity.
(2) microwave cavity produces reflected signal and passes to module one amplitude discrimination circuit: in amplitude discrimination circuit, first frequency signal is carried out filter rectification and become direct current signal.Microwave cavity amplitude output signal is under resonance condition less than 200mV.Output signal and reference voltage are that the comparer LM339 of 200mV compares.Export 2 binary signal 0,1 to FPGA processor.If output voltage is less than 200mV, as shown in Fig. 3 (a), resonator cavity is in resonant condition, and output port exports 0 to FPGA; If output voltage is greater than 200mV as shown in Fig. 3 (a), resonator cavity is in off resonance state, and output port exports 1 to FPGA.
(3) FPGA processor receives 2 binary signal that amplitude discrimination circuit sends, and judges whether resonance.If detect resonance, then control to export microwave cavity resonance frequency by FPGA; When resonator cavity off resonance, the phase relation of reflected signal and reference signal is divided into two kinds of situations: when reflected signal frequency is greater than reference signal frequency, the two phase place is identical, as shown in Fig. 5 (a); When reflected signal frequency is less than reference signal frequency, the two phase place is contrary, as shown in Fig. 5 (b).Differentiated by multiplier chip MC1496 settling signal phase place in phase identification of circuit.Compare with the 0V reference voltage of LM339 after RC filtering, by exporting binary signal with door.If carrier frequency is less than resonance frequency, output port exports 0; If be greater than resonance frequency by measured frequency, output port exports 1, and output signal is sent to FPGA parametric controller, and FPGA controls voltage controlled oscillator (VCO) by DAC (digital-to-analog conversion) and adjusts frequency.
(4), after adjusting frequency, the reflection carrier signal of microwave cavity is entered module one amplitude discrimination circuit by circulator again and differentiates.Circulate successively, until find microwave cavity resonance frequency.
The present invention is further described below in conjunction with the drawings and specific embodiments.
Fpga chip is based on the method for software and hardware combining, and software language controls, calls each several part, hardware cell survey frequency numerical value.Circulator and wave detector processing signals are the accessible signal of low frequency, and the voltage changing digital-to-analog circuit can control the output frequency of voltage controlled oscillator.
Amplitude discrimination circuit comprises low-pass filter, amplifier and comparer, arranges reference voltage and judges amplitude, output signal be less than reference voltage then current state be resonant condition, output signal be greater than reference voltage then current state be non-resonant condition.
Phase identification of circuit comprises multiplier, low-pass filter and comparer, and after multiplier process after filtering, the output signal of plus or minus represents homophase or anti-phase.Signal frequency through microwave cavity is greater than resonance frequency then homophase, and comparator reference voltage is set to zero, exports " 1 " and represents that ongoing frequency is greater than resonance frequency, export " 0 " and then represent that ongoing frequency is less than resonance frequency.Binary message feeds back to FPGA platform and carries out feedback regulation, finally realizes rate-adaptive pacemaker.
Citing document:
[1]Abhishek Kumar Jha and Mohammad Jaleel Akhtar,“A Generialized Rectangular CavityApproach for Determination of Complex Permittivity of Materials,”IEEE TRANSACTIONSON INSTRUMENTATION AND MEASUREMENT,vol.63,no.11,NOV.2014.CurrentApplied Physics,14,pp.563-569,Jan 2014。
[2]G.Gennarelli,S.Romeo,M.R.Scarfi and F.Soldovieri,“A microwave resonant sensor forconcentration measurements of liquid solutions,”IEEE Sensors J.,vol.13,no.5,pp.1857-1864,May 2013。
[3]S.Kim,H.Melikyan,J.Kim,A.Babajanyan,J.H.Lee,L.Enkhtur,B.Friedman and K.Lee,“Noninvasive in virto measurement of pig-blood D-glucose by using a microwave cavitysensor,”Diabetes Res.Clinical Pract.,pp.379-384,Jan.2012。
[4]R.Dobson,R.Wu and P.Callaghan,“Blood glucose monitoring using microwave cavityperturbation,”Electronics Letters.,vol.48,no.15,pp.1-2,May 2012。
[5]B.Kapilevich and B.Litvak,“Optimized microwave sensor for online concentrationmeasurements of binary liquid mixtures,”IEEE Sensors J.,vol.11,no.10,pp.2611-2616,Oct.2011。
Claims (4)
1. the frequency-tracing measurement device of a microwave cavity, it is characterized in that, comprise: amplitude discrimination circuit, phase identification of circuit, D/A converting circuit, voltage controlled oscillator, circulator, microwave cavity, wave detector, control circuit forms, input waveguide signal enters resonator cavity, undertaken reflecting the reflected signal produced by resonator cavity to output to circulator through wave detector and select, first signal enters in amplitude discrimination circuit, in amplitude discrimination circuit, output signal is converted to binary signal 0, 1 and be input to control circuit, control circuit is by 0, 1 signal judges whether resonator cavity resonance occurs, if resonance, then directly enter frequency detecting part, if there is no resonance, then returning said process, making resonator cavity reflected signal by selecting after wave detector and circulator to enter phase identification of circuit,
Phase identification of circuit carries out phase place qualification to the resonator cavity reflected signal after wave detector process, exports 0,1 signal and is sent to control circuit, and control circuit loads input waveguide frequency higher or lower than resonator cavity actual frequency by acquisition 0,1 input; Control circuit is added and subtracted input waveguide signal frequency by D/A converting circuit conversion and control voltage controlled oscillator, to approach resonator cavity actual frequency, after completing this process, then repeats with cocycle, until detect true resonance frequency f.
2. the frequency-tracing measurement device of microwave cavity as claimed in claim 1, it is characterized in that, amplitude discrimination circuit comprises low-pass filter, amplifier and comparer, comparer arranges reference voltage and judges amplitude, input signal enters comparer and compares after low-pass filter, amplifier, be less than reference voltage then current state be resonant condition, be greater than reference voltage then current state be non-resonant condition.
3. the frequency-tracing measurement device of microwave cavity as claimed in claim 1, it is characterized in that, phase identification of circuit comprises multiplier, low-pass filter and comparer, after multiplier process after filtering, the output signal of plus or minus represents homophase or anti-phase, signal frequency through microwave cavity is greater than resonance frequency then homophase, comparator reference voltage is set to zero, export " 1 " and represent that ongoing frequency is greater than resonance frequency, export " 0 " and then represent that ongoing frequency is less than resonance frequency, binary message feeds back to D/A converting circuit and carries out feedback regulation, finally realize rate-adaptive pacemaker.
4. the frequency-tracing measurement device of microwave cavity as claimed in claim 1, it is characterized in that, control circuit is realized by field programmable gate array.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510250973.5A CN105021885A (en) | 2015-05-15 | 2015-05-15 | Frequency tracking measurement device for microwave resonant cavity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510250973.5A CN105021885A (en) | 2015-05-15 | 2015-05-15 | Frequency tracking measurement device for microwave resonant cavity |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN105021885A true CN105021885A (en) | 2015-11-04 |
Family
ID=54411999
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510250973.5A Pending CN105021885A (en) | 2015-05-15 | 2015-05-15 | Frequency tracking measurement device for microwave resonant cavity |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN105021885A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105807132A (en) * | 2016-03-07 | 2016-07-27 | 东莞中子科学中心 | Method for detecting detuning frequency of radio-frequency cavity of accelerator |
| CN112345843A (en) * | 2020-09-17 | 2021-02-09 | 山东师范大学 | Power amplitude limiter and test system based on atmospheric pressure plasma and microwave discharge |
| US20210263112A1 (en) * | 2020-02-20 | 2021-08-26 | Hitachi Metals, Ltd. | Multicore cable inspection method and multicore cable inspection device |
| CN113437969A (en) * | 2021-05-25 | 2021-09-24 | 国仪量子(合肥)技术有限公司 | Phase-locked loop frequency synthesizer and control method thereof |
| CN113465633A (en) * | 2021-08-09 | 2021-10-01 | 东南大学 | Microwave resonant sensor for software intelligent detection and frequency shift detection method thereof |
| WO2023138167A1 (en) * | 2022-01-21 | 2023-07-27 | 深圳麦时科技有限公司 | Aerosol generating apparatus, control method, control apparatus, and readable storage medium |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4887901A (en) * | 1985-07-30 | 1989-12-19 | Centre Suisse D'electronique Et De Microtechnique S.A. | Optical fiber detection system using an intensity-modulating sensor |
| JPH0980089A (en) * | 1995-09-14 | 1997-03-28 | Advantest Corp | Frequency measuring apparatus |
| CN102590230A (en) * | 2012-01-12 | 2012-07-18 | 天津大学 | Microwave resonant cavity sensor and measurement system for measuring concentration of solution |
| CN102809572A (en) * | 2012-08-08 | 2012-12-05 | 天津大学 | System for measuring solution concentration by using perturbation method |
| CN104198811A (en) * | 2014-08-18 | 2014-12-10 | 广东电网公司电力科学研究院 | Method and device for measuring frequency of low frequency signal |
-
2015
- 2015-05-15 CN CN201510250973.5A patent/CN105021885A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4887901A (en) * | 1985-07-30 | 1989-12-19 | Centre Suisse D'electronique Et De Microtechnique S.A. | Optical fiber detection system using an intensity-modulating sensor |
| JPH0980089A (en) * | 1995-09-14 | 1997-03-28 | Advantest Corp | Frequency measuring apparatus |
| CN102590230A (en) * | 2012-01-12 | 2012-07-18 | 天津大学 | Microwave resonant cavity sensor and measurement system for measuring concentration of solution |
| CN102809572A (en) * | 2012-08-08 | 2012-12-05 | 天津大学 | System for measuring solution concentration by using perturbation method |
| CN104198811A (en) * | 2014-08-18 | 2014-12-10 | 广东电网公司电力科学研究院 | Method and device for measuring frequency of low frequency signal |
Non-Patent Citations (1)
| Title |
|---|
| 李建潼: "基于微波谐振腔的葡萄糖溶液浓度测量系统", 《电子产品世界》 * |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105807132A (en) * | 2016-03-07 | 2016-07-27 | 东莞中子科学中心 | Method for detecting detuning frequency of radio-frequency cavity of accelerator |
| CN105807132B (en) * | 2016-03-07 | 2018-10-26 | 东莞中子科学中心 | A kind of method and device of detection accelerator radio-frequency cavity off-resonance frequency |
| US20210263112A1 (en) * | 2020-02-20 | 2021-08-26 | Hitachi Metals, Ltd. | Multicore cable inspection method and multicore cable inspection device |
| US11815563B2 (en) * | 2020-02-20 | 2023-11-14 | Proterial, Ltd. | Multicore cable inspection method and multicore cable inspection device |
| CN112345843A (en) * | 2020-09-17 | 2021-02-09 | 山东师范大学 | Power amplitude limiter and test system based on atmospheric pressure plasma and microwave discharge |
| CN112345843B (en) * | 2020-09-17 | 2022-06-24 | 山东师范大学 | Power amplitude limiter and test system based on atmospheric pressure plasma and microwave discharge |
| CN113437969A (en) * | 2021-05-25 | 2021-09-24 | 国仪量子(合肥)技术有限公司 | Phase-locked loop frequency synthesizer and control method thereof |
| WO2022247215A1 (en) * | 2021-05-25 | 2022-12-01 | 国仪量子(合肥)技术有限公司 | Phase-locked loop frequency synthesizer and control method therefor |
| CN113437969B (en) * | 2021-05-25 | 2023-04-07 | 国仪量子(合肥)技术有限公司 | Phase-locked loop frequency synthesizer and control method thereof |
| CN113465633A (en) * | 2021-08-09 | 2021-10-01 | 东南大学 | Microwave resonant sensor for software intelligent detection and frequency shift detection method thereof |
| CN113465633B (en) * | 2021-08-09 | 2023-01-03 | 东南大学 | Microwave resonant sensor for software intelligent detection and frequency shift detection method thereof |
| WO2023138167A1 (en) * | 2022-01-21 | 2023-07-27 | 深圳麦时科技有限公司 | Aerosol generating apparatus, control method, control apparatus, and readable storage medium |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN105021885A (en) | Frequency tracking measurement device for microwave resonant cavity | |
| KR102331740B1 (en) | Frequency modulated radar level gauging | |
| CN105067654A (en) | Single-mode resonant cavity sensor-based solution concentration measurement method | |
| CN102048537B (en) | Multifrequency synchronous excitation current source used in bio-electrical impedance frequency spectrum measurement | |
| CN211348423U (en) | High-frequency signal measuring device | |
| CN102809572A (en) | System for measuring solution concentration by using perturbation method | |
| CN113156356A (en) | Remote calibration system and calibration method for voltage source | |
| CN101996480B (en) | Wireless sensor measurement system of self-calibration integrated circuit | |
| Olaya et al. | Phase noise and frequency stability of the red-pitaya internal PLL | |
| CN110716092B (en) | Phase noise measuring device and measuring method based on laser frequency discrimination and cross-correlation processing | |
| Fu et al. | NSRR microwave sensor based on PLL technology for glucose detection | |
| CN106092147B (en) | A kind of digital integrator for superconducting cyclotron magnetic-field measurement | |
| CN113395109B (en) | Automatic locking method and system of optical frequency comb | |
| Svensson | A wattmeter standard for the audio frequency range | |
| CN109596694A (en) | A kind of measurement analysis device suitable for different impedance electrochemical systems | |
| CN107543960A (en) | A kind of high stability crystal oscillator measurement apparatus | |
| Sonnaillon et al. | Software PLL based on random sampling | |
| Yusuf et al. | Analysis of single excitation signal for high speed ECVT data acquisition system | |
| CN201886081U (en) | Loose phase lock method-based short-term frequency stability measuring device | |
| CN104539289B (en) | A kind of appraisal procedure and device of atomic frequency standard frequency short-term stability | |
| Pei et al. | Measurement of soil electrical conductivity based on direct digital synthesizer (DDS) and digital oscilloscope | |
| CN103472330A (en) | Measuring device of frequency stability of superconducting frequency stabilization oscillator | |
| US11480536B2 (en) | Method and sensor for determining the permittivity of a cell population | |
| Teren et al. | Direct comparison of analogue and digital FGPA-based approaches to synchronous detection | |
| CN104034989A (en) | Capacitive touch sensor tester |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20151104 |
|
| WD01 | Invention patent application deemed withdrawn after publication |