CN106980049B

CN106980049B - Fluid dielectric property tiny change detection device based on coplanar waveguide/slot line type

Info

Publication number: CN106980049B
Application number: CN201710186355.8A
Authority: CN
Inventors: 刘伟娜; 徐世周; 詹华伟; 胥磊; 孙乃乔
Original assignee: Henan Normal University
Current assignee: Henan Normal University
Priority date: 2017-03-27
Filing date: 2017-03-27
Publication date: 2023-03-07
Anticipated expiration: 2037-03-27
Also published as: CN106980049A

Abstract

The invention discloses a fluid dielectric property tiny change detection device based on a coplanar waveguide/slotline line type, which comprises two coplanar waveguide-slotline hybrid ring couplers, wherein a coplanar waveguide-slotline balun is connected between an input port of a first hybrid ring coupler and a first 1/4 annular slotline, a fan-shaped radiation surface is loaded at the tail end of an isolation port coplanar waveguide transmission line of the first 1/4 annular slotline, two balance ports are 180-degree inverted outputs, and the tail ends of the balance ports are respectively connected with the coplanar waveguide-slotline back-to-back balun; the isolation port of the second 1/4 annular slot line is a slot line, the tail end of the slot line is loaded with a fan-shaped radiation surface, the two balance ports are in-phase output, and the tail ends of the two balance ports are respectively connected with a coplanar waveguide-slot line back-to-back balun; the balanced ports of the two hybrid ring couplers are connected by a groove line segment, respectively, and microfluidic channels are provided on the groove line segment. The invention has high sensitivity, wide frequency band, simple detection method and easy integration.

Description

Fluid dielectric property tiny change detection device based on coplanar waveguide/slot line type

Technical Field

The invention belongs to the technical field of microwave measurement, and particularly relates to a fluid dielectric property tiny change detection device based on a coplanar waveguide/slot line type.

Background

With the continuous development of microwave technology, the measurement of dielectric properties of substances plays an important role in the fields of microwave engineering, microwave chemistry, electromagnetic field biomedicine and the like. Conventional microwave dielectric property measurement can be classified into a resonance method and a non-resonance method, wherein the non-resonance method is relatively simple. In the non-resonant method, the transmission-reflection method is widely applied to broadband measurement, and the dielectric property measurement of low-loss substances can achieve higher precision.

However, for the thermal denaturation of protein, the single cell property, the microwave chemical non-thermal effect detection, the electric detection of biomedical information, etc., the measurement of the tiny changes of the dielectric property of the measured substance is faced, these tiny changes may be the medium or medium group of the measured substance is tiny, that is, the measured object is microfluid, or the measured substance is disturbed by the external factorsThe temperature or microstructure of the body is weakly shifted, causing a slight change in dielectric properties. The information of the small changes is very weak and is accompanied by strong background noise, or the signal fluctuation is strong and is in a changing state, and the traditional microwave measuring device cannot capture the weak information. Literature (Yang, Y., H. Zhang, J. Zhu, et al. Distinguishing the visual of a single layer cell with an ultra-sensitive radio frequency sensor [ J. ]], Lab Chip, 10 And (5) 553-555, 2010) proposes a radio frequency sensor, which adopts the concept of 'two branches cancel' to design a detection device. Compared with the traditional transmission-reflection method, the sensitivity is greatly improved, the characteristics of cells are detected in a radio frequency band, but the bandwidth of the detection device is limited. Accordingly, there is a need to provide alternative, more efficient and more sensitive broadband measurement devices for detecting small changes in the dielectric properties of fluids.

Disclosure of Invention

Aiming at the problems of narrow bandwidth, low sensitivity and the like in the existing technology for measuring the tiny change of the dielectric property of the fluid substance, the invention aims to provide a device for detecting the tiny change of the dielectric property of the fluid based on a coplanar waveguide/slot line type.

The invention adopts the following technical scheme for realizing the aim, and the fluid dielectric property tiny change detection device based on the coplanar waveguide/slotline line type is characterized by comprising two hybrid ring couplers with a broadband planar slotline structure, wherein a coplanar waveguide transmission line is adopted as an input port of a first hybrid ring coupler, a coplanar waveguide-slotline balun is connected between the input port and a first 1/4 annular slotline, two balance ports and an isolation port of the first 1/4 annular slotline are coplanar waveguide transmission lines, a fan-shaped radiation surface is loaded at the tail end of the isolation port, the two balance ports are 180-degree inverted outputs, and the tail ends of the balance ports are respectively connected with the coplanar waveguide-slotline back-to-back baluns; the output port of the second hybrid ring coupler adopts a coplanar waveguide transmission line, two balanced ports of a second 1/4 annular slot line are coplanar waveguide transmission lines, wherein an isolation port is a slot line, the tail end of the isolation port is loaded with a fan-shaped radiation surface, the two balanced ports are in-phase output, and the tail ends of the balanced ports are respectively connected with a coplanar waveguide-slot line back-to-back balun; the balanced ports of the two hybrid ring couplers are connected through a groove line section to form two branches of a transmission line and a reference line, and a microfluidic channel is arranged on the groove line section connecting the two hybrid ring couplers.

Further preferably, the input port of the first hybrid ring coupler and the output port of the second hybrid ring coupler are respectively connected to a vector network analyzer.

Further preferably, the microfluidic channel is a T-shaped microfluidic channel, and the T-shaped microfluidic channel is used for placing a sample to be detected.

The invention provides a fluid dielectric property tiny change detection device, which mainly comprises an input port, a transmission line, a reference line and an output port; and microfluidic channels are arranged on the two lines and used for bearing detection and reference microfluids. During the test, the tested fluid is placed on the microfluidic channel, which is equivalent to the introduction of a discontinuous structure, so that the port scattering parameter information of the test device is changed, and the change reflects the tiny change of the dielectric property of the tested object. The invention designs the fluid dielectric property tiny change detection device based on the coplanar waveguide/slotline line type by utilizing the transmission principle of the microwave, and the micro-flow channel enables the detected object to fully influence the transmission of the electromagnetic wave, so the detection sensitivity of the device can be greatly improved.

Numerical simulation is carried out on the detection device through a Finite Element (FEM) algorithm, and experimental results show that the detection device can sensitively sense weak information caused by nano-liter-level microfluid in a frequency band of 2-4.5GHz, and the limit of the change of the dielectric property of the microfluid of two detectable lines is 1.6.

Compared with the prior art, the invention has the following beneficial effects: the fluid dielectric characteristic tiny change detection device based on the coplanar waveguide/slotline structure, provided by the invention, has the advantages that the required volume of the fluid to be detected is nano-liter, the device can be applied to the fields of cytology, electromagnetic field biomedicine, microwave chemical non-thermal effect, protein thermal denaturation and the like, the detection device is high in sensitivity, wide in frequency band, simple in detection method and easy to integrate, and has the potential of being combined with other devices to form a micro analysis system.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of the core components and electric fields of the present invention;

FIG. 3 is a schematic diagram of a T-shaped microfluidic channel according to the present invention;

FIG. 4 is a graph of the transport parameters of the present invention prior to loading the microfluidics.

In the figure: 1. the waveguide-slot antenna comprises an input port, 2, an output port, 3, a signal transmission gap, 4, a middle conduction band, 5, a first 1/4 annular slot line, 51, a second 1/4 annular slot line, 6, a coplanar waveguide-slot line balun, 61, a coplanar waveguide-slot line back-to-back balun, 7, a balance port, 8, an isolation port, 9, a fan-shaped radiation surface, 10 and a slot line section.

Detailed Description

The details of the present invention are described in detail with reference to the accompanying drawings. The invention discloses a fluid dielectric property tiny change detection device based on a coplanar waveguide/slot line type, which is shown in figure 1 and comprises an input port 1 and an output port 2, wherein the input port and the output port are coplanar waveguide transmission lines which comprise two signal transmission gaps 3 and an intermediate conduction band 4; a coplanar waveguide-slot line balun 6 is connected between the input port 1 and the first 1/4 annular slot line 5; when a signal is input from an input port 1 of the first hybrid ring coupler and is transmitted to a 1/4 annular slot line 5 through a coplanar waveguide-slot line balun 6, the signal is divided into two paths of signals with the same amplitude and opposite phases, at least part of the two paths of signals can reach an isolation port 8 of the first hybrid ring coupler, the isolation port 8 adopts a coplanar waveguide transmission line, and a fan-shaped radiation surface 9 is loaded at the tail end of the coplanar waveguide transmission line; most of signals reach two balanced ports 7 of a first hybrid ring coupler consisting of coplanar waveguide transmission lines, then transition into a slot mode through a coplanar waveguide-slot line back-to-back balun 61, and respectively reach two balanced ports 7 of a second hybrid ring coupler through a slot line segment 10 part, the two balanced ports 7 of the second hybrid ring coupler are coplanar waveguide transmission lines, the slot line segment 10 and the two balanced ports 7 of the second hybrid ring coupler adopt the slot line-coplanar waveguide back-to-back balun 61, finally the two signals respectively reach an output port 2 of the second hybrid ring coupler through a second 1/4 annular slot line 51, ideally, the two signals reaching the output port 2 of the second hybrid ring coupler can be cancelled, few parts of the signals can be reflected to an isolated port 8 of the second hybrid ring coupler consisting of the slot line, and a fan-shaped radiation surface 9 is also loaded at the tail end of the isolated port 8.

Fig. 2 is a schematic diagram of the core components and electric fields of each part of the testing device provided by the present invention, and it can be seen from fig. 2 that when a signal is input from the E-arm, the part of the signal reaching the 1/4 annular groove line will be converted into two lines of signals with the same amplitude and opposite phases, i.e. the output signals of the two balance arms (balance arm 1 and balance arm 2) will have a phase difference of 180 °, and ideally, no signal is output from the H-arm; if a signal is input from the H arm, the two balance arms (balance arm 1 and balance arm 2) will output the same signal, and ideally, the E arm has no signal output.

To facilitate the detection of the dielectric properties of the microfluid, a T-shaped microfluidic channel was designed in each of the transmission line and the reference line of the two branch line section shown in FIG. 1, and the shape thereof is shown in FIG. 3. During testing, a tested sample is placed in a T-shaped microfluidic channel of a transmission line, and meanwhile, an input port 1 of the first mixed ring coupler and an output port 2 of the second mixed ring coupler are connected with a vector network analyzer respectively.

The invention relates to a method for detecting micro-change of dielectric property of fluid, wherein the object to be detected is micro-fluid or micro-change of temperature, concentration or internal structure of the fluid to be detected. The detection device provided by the invention effectively eliminates background noise when the detected object is not loaded, so that extremely weak external interference can be sensitively sensed.

Fig. 4 shows the transmission parameter condition when the detection device is not loaded with the measured object, and it can be seen from the figure that the detection device provided by the present invention effectively eliminates the background noise of the transmission line in the range of 2-4.5GHz, the transmission parameter is lower than-45 dB in the whole frequency band, when the measured object is placed in the microfluidic channel of the detection device, it is equivalent to introducing a discontinuity structure, the original balance is broken, and the small difference in the two branches will be reflected in the phase and amplitude change of the scattering parameter of the port. Research shows that the invention can sensitively sense nano-liter micro-fluid in a broadband range, and the larger the micro-fluid volume is, the higher the sensitivity is, because for the same measured fluid, the larger the volume is, the larger the frequency deviation of the transmission parameter will be.

The fluid dielectric property tiny change detection device provided by the invention is completely constructed by coplanar transmission lines, leads do not need to be welded on each part, high-sensitivity test, miniaturization manufacture and integration with other microwave circuits are more convenient to realize, a microfluid channel only needs to be arranged on a groove line segment connecting two mixing ring couplers, and specific positions have no definite requirements.

While there have been shown and described what are at present considered the fundamental principles of the invention, its essential features and advantages, the invention further resides in various changes and modifications which fall within the scope of the invention as claimed.

Claims

1. The fluid dielectric property tiny change detection device based on the coplanar waveguide/trough line type is characterized by comprising two hybrid ring couplers of a broadband planar trough line structure, wherein an input port of a first hybrid ring coupler adopts a coplanar waveguide transmission line, a coplanar waveguide-trough line balun is connected between the input port and a first 1/4 annular trough line, two balance ports and an isolation port of the first 1/4 annular trough line are coplanar waveguide transmission lines, a fan-shaped radiation surface is loaded at the tail end of the isolation port, two balance ports are 180-degree inverted outputs, and the tail ends of the balance ports are respectively connected with the coplanar waveguide-trough line back-to-back balun; the output port of the second hybrid ring coupler adopts a coplanar waveguide transmission line, two balanced ports of a second 1/4 annular slot line are coplanar waveguide transmission lines, wherein an isolation port is a slot line, the tail end of the isolation port is loaded with a fan-shaped radiation surface, the two balanced ports are in-phase output, and the tail ends of the balanced ports are respectively connected with a coplanar waveguide-slot line back-to-back balun; the balance ports of the two hybrid ring couplers are respectively connected through a groove line section to form two branches of a transmission line and a reference line, and a microfluid channel is arranged on the groove line section connecting the two hybrid ring couplers; the input port of the first hybrid ring coupler and the output port of the second hybrid ring coupler are respectively connected with a vector network analyzer; the microfluid channel is T-shaped microfluid channel, and the T-shaped microfluid channel is used for placing the tested sample.