Planar microwave cavity drip-in type liquid dielectric substance value detection sensor

A microwave cavity and dielectric technology, which is applied in the direction of material analysis, instruments, and measurement devices using microwave means to achieve the effect of simple processing circuits

Active Publication Date: 2019-11-26
5 Cites 4 Cited by

AI-Extracted Technical Summary

Problems solved by technology

However, this requires a certain volume of liquid to analyze the dielectric properties
Especially in the detection of biological...
View more


The invention belongs to the technical field of microwave sensing and relates to a planar microwave cavity drip-in type liquid dielectric substance value detection sensor. A square OCSRR of the detection sensor is fixed on the top surface of a single-sided FR4 substrate; a rectangular detection area exists at the top of the square OCSRR; the rectangular detection area is of a rectangular structure; two output ends of the square OCSRR are connected with two input ends in the rectangular detection area; a three-sided metal rectangular frame is arranged outside the rectangular structure; two endsof the metal rectangular frame are suspended; two metal wires in the rectangular detection area are located in the metal frame; one end of each of the two metal wires is suspended; the metal wires are arranged in the metal frame so as to form a rectangular double-loop form; the two metal wires are parallel to each other; and the direction of the inner metal wire is opposite to that of the external metal wire. According to the invention, a drip-in mode is adopted; a to-be-detected liquid is directly dripped to a sensing area; a high-precision micro-channel does not need to be additionally manufactured; the sensing end is suitable for mass production; and a back-end processing circuit is simple.

Application Domain

Material analysis using microwave means

Technology Topic

PhysicsLiquid dielectric +3


  • Planar microwave cavity drip-in type liquid dielectric substance value detection sensor
  • Planar microwave cavity drip-in type liquid dielectric substance value detection sensor
  • Planar microwave cavity drip-in type liquid dielectric substance value detection sensor


  • Experimental program(1)

Example Embodiment

[0028] The internal size of the FR4 container used in the present invention is 7.5×7.5mm 2 To cover the sensor detection area. The height of the container is 1.6 mm, which provides enough space for adjusting the volume of the liquid to be measured. The width and length of the container (i.e. c1 and c2) are respectively larger than the width of the detection area sensor (4.1×4.6mm 2 ) Large 3.4 and 2.9mm to ensure that the liquid to be tested is exposed to the electric field on the side of the container.
[0029] The parameter study of the influence of the volume of the liquid to be measured on the frequency and decibels of the reflection notch is carried out. To evaluate the different volumes of the liquid to be measured in the sensor, Figure 5 The measurement result is displayed. Evaluate the different volumes of S11 for 0.02, 0.04, 0.06, 0.08 and 0.1 mL deionized (DI) water placed on the detection area. Deionized water was chosen because of its high dielectric constant, which is suitable for limiting testing. Picture 9 It is shown that by increasing the volume of the sample liquid from 0.02 to 0.1 mL, the resonance frequency decreases and the S11 value increases. In the initial region (0.02mL to 0.08mL), the resonance frequency changes with the volume of the liquid to be measured. In the subsequent region (0.08mL to 0.1mL), the resonance frequency is constant. With the further increase of the liquid volume, the change of S11 can be ignored. The electric radiation field is concentrated on the copper surface of the sensor. Cover the liquid sample and further increase the volume of the liquid to be tested (> 0.08mL) will not affect electromagnetic energy, and the effective dielectric constant will not change. Therefore, for volume sensing applications, the operation must be performed in the first region, and for liquid characterization, the second region should be used. Once a certain volume is reached, the resonance frequency becomes constant. The saturation point is defined as the minimum volume required for liquid sensing applications. Use a micropipette to obtain the correct volume of the liquid to be tested (> 0.08mL), and test different volumes of the liquid to be tested, indicating that the sensor can successfully detect liquids with a dielectric constant of 1 to 80. The sensor exhibits the same behavior for all liquid volumes to be measured.
[0030] Four liquid measurement results:
[0031] The dielectric constant of liquid composites is measured in the frequency range of 100-375MHz. Keep the temperature at room temperature (25°C). The test liquid used in the experiment is deionized (DI) water (ε'=80, ε"=9.2), methanol (ε'=35, ε"=5.13), ethanol (ε'=22, ε"= 6.6), and butanol (ε'=17, ε'=7.21). Put these sample materials (> 0.08mL) was loaded onto the detection area and characterized to verify the proposed sensor design. Image 6 The results of the calculated parameter responses of different liquids with high dielectric constant are shown. The results revealed clear differences between the different liquids. The dielectric properties of the liquid to be tested are affected by temperature. Regarding the repeatability of the measurement and the stability of the liquid material to be tested, the liquid sample to be tested should be stored in a thermostat (25°C) closet. During the measurement, the laboratory environment should be maintained at a steady state of 25°C and the air-water heat exchanger equipment should be heated. The measurement should be carried out in a short time to avoid changes due to temperature.
[0032] The air is evaluated to calibrate the measurement value of the empty detection area, and the corresponding liquids of the other four materials are filled in the area. The results show that for an empty, air-filled detection area, the measured resonance frequency of the OCSRR sensor is 330MHz, and the return loss is 62dB. Use a micropipette to inject and control the liquid to be tested. The change of S parameter is recorded and transmitted to the computer within 30 seconds. For methanol and deionized water samples, the resonance frequencies are 231 and 204 MHz, and the return loss is 37.41 and 40.53 dB, respectively. For ethanol and butanol samples, the resonance frequencies are 264 and 284 MHz, and the return loss is 34.31 and 29.56 dB, respectively. A difference of 126 MHz was observed between the resonance frequencies of DI water and air (empty channel), and a difference of 99 MHz was observed between the resonance frequencies of methanol and air.
[0033] ANSYS High Frequency Structure Simulator (HFSS) 18.2 is used as a simulation tool to extract S11 scattering parameters. HFSS software is a full-wave frequency domain three-dimensional electromagnetic field solver. It uses the gold standard precision finite element method (FEM) to model the structure and calculate the electromagnetic field in the frequency domain. The finite element method integral equation hybrid technology is based on HFSS and domain decomposition method (DDM), and is used to solve the local area of ​​high geometric detail in complex materials. Then, HFSS 18.2 uses a field-based adaptive grid to obtain the final grid. As mentioned earlier, a constant complex permittivity value is used to model the properties of the liquid materials to be tested, water, methanol, ethanol, and butanol used in the simulation. The simulation is shifted in frequency (MHz), and the S11 reflection coefficient (dB) in the four cases results in the plot as a fitted curve format and together with the measurement data. The computer simulation of the ε'function in the MHz range is Figure 8 Is depicted as a dashed line. Picture 9 The loss tangent function in dB depicted in is represented by a dashed line. All geometric parameters of the proposed sensor. EM simulation is consistent with the measurement of pure liquid to be measured in the region of interest.
[0034] At the operating resonance frequency, the transmission coefficient S21 is approximately -0.1 to -0.2dB (independent of the liquid sample). At the resonance frequency band, the power transmission from port 1 to port 2 is almost 99%. Even if the sensor is loaded with the liquid to be measured, S11 is about -30 to -60dB for the four liquids to be measured. The power loss of S21 in the resonance region is about -0.2dB. For high-loss liquid detection, almost no loss operation, and the liquid to be tested absorbs very little power. This feature is suitable for biomedical applications.
[0035] In order to simplify the calculation, a set of exponential functions (5) and (6) are then used to derive the measurement results between the dielectric constant and the resonance frequency (in MHz) and the loss tangent and the complex dielectric constant of the liquid, respectively. The equation that characterizes the measurement results is as follows:
[0036] ε'(MHz)=11845exp(-1×f 0 (MHz)/40.61)+0.8419 (5)
[0037] loss tangent(S 11 (dB))=9.946exp(S 11 (dB)/9.345)-0.0168 (6)
[0038] Implementation results:
[0039] In order to verify the proposed method for estimating the complex permittivity and accuracy of the liquid to be tested, another experiment was performed using a DI water/ethanol mixture in the range of 10%-100%, with a step size of 10% for the liquid The concentration of ethanol. sample. In the sample, 0% ethanol means 100% deionized water. Fill the container with various concentrations of ethanol and compare with DI water alone. Picture 9 Shows the measured frequency response obtained using a vector network analyzer after loading the sensor with concentration materials with different relative complex permittivities. The changing mixture concentration corresponds to an equivalent change in resonance frequency and amplitude.
[0040] For ethanol concentrations of 100% and 10%, respectively, the resonance frequency changed from fo=264.3MHz (-34.15dB) to fo=211.2MHz (-40.92dB), which proves the deviation of the dielectric constant of 53.1MHz (6.77dB). To simplify the problem, use (5) and (6) to obtain measurement data to approximate the frequency shift of the sample, the variation of the dB factor and the interdependence between the complex permittivity. The results show that the estimated value of the complex permittivity calculated using the proposed method is consistent with the literature. However, small differences between measured values ​​and data have been observed in the literature with high ethanol scores. Based on repeatability testing, a standard deviation of 3 MHz was observed in the 100% ethanol measurement. Calculate the 3MHz change value of the liquid ethanol to be tested from (5) to obtain a dielectric constant of 1.59, and its ε'is 23.59. If there is 5% uncertainty in the literature.


no PUM

Description & Claims & Application Information

We can also present the details of the Description, Claims and Application information to help users get a comprehensive understanding of the technical details of the patent, such as background art, summary of invention, brief description of drawings, description of embodiments, and other original content. On the other hand, users can also determine the specific scope of protection of the technology through the list of claims; as well as understand the changes in the life cycle of the technology with the presentation of the patent timeline. Login to view more.

Similar technology patents

Intelligent safety shoe based on fabric pressure sensor

InactiveCN106235495ASimple processing circuitHigh measurement accuracy

Laser phase ranging module

ActiveCN105652282ASimple processing circuitsimple algorithm

Classification and recommendation of technical efficacy words

  • Simple processing circuit

Laser phase ranging module

ActiveCN105652282ASimple processing circuitsimple algorithm

Intelligent safety shoe based on fabric pressure sensor

InactiveCN106235495ASimple processing circuitHigh measurement accuracy
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products