A high-sensitivity coaxial resonant testing device for small-area microwave testing

Abstract

This invention discloses a high-sensitivity coaxial resonant testing device for small-area microwave testing, belonging to the field of electromagnetic parameter testing technology for microwave and millimeter-wave materials. The device is based on a traditional coaxial resonant cavity, incorporating a probe structure to construct a quarter-wavelength coaxial resonator with one end open and the other short-circuited. Due to the large size of the coaxial resonant cavity and the absence of dielectric filling, the device exhibits a high quality factor and high testing sensitivity. The probe is connected to the conductor inside the coaxial resonant cavity via a plug-in connection, allowing for easy replacement as needed. By changing the probe length, the device length can be adjusted to accommodate wideband testing, thus solving the problem of wideband testing. Compared to traditional half-wavelength or quarter-wavelength resonators, this invention fully considers both high sensitivity and small-area detection requirements.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic parameter testing technology for microwave and millimeter-wave materials, and specifically relates to a high-sensitivity coaxial resonant testing device for small-area microwave testing. Background Technology

[0002] With the continuous development of microwave technology, the performance requirements for microwave devices are becoming increasingly stringent. Microwave devices and circuit components are developing towards miniaturization and integration. To meet the demands of miniaturized and integrated electronic components, thin film materials have emerged. For example, dielectric thin film materials possess ferroelectric, piezoelectric, and nonlinear optical properties, and have important applications in the semiconductor industry, optical communication, and electrical communication. Alloy thin film materials, with their high permeability and high loss properties, can be used to absorb broadband microwaves and can be used to fabricate microwave absorbing materials. Heterogeneous integrated materials can simultaneously leverage the unique characteristics of each component, enabling microwave technology to be applied to different devices simultaneously, meeting the requirements of high-power devices for material stability, integration, and miniaturization. The microwave performance of thin film materials is a crucial factor affecting their use in devices. Improving testing precision and enhancing the accuracy of thin film performance testing directly impacts the application of thin film materials in microwave devices. Furthermore, the microwave performance of fabricated thin film materials may exhibit inhomogeneity or inconsistency at different locations, necessitating accurate testing of these localized small areas.

[0003] Commonly used methods for testing the dielectric properties of materials include the network parameter method and the resonant cavity method. The network parameter method primarily measures the scattering or reflection parameters of the port network of the sample under test (SUT) to determine the microwave properties of the SUT. This method can achieve broadband frequency sweep testing. In practice, some planar circuits and transmission structures in the network parameter method can be fabricated into probe structures, enabling the detection of small, localized areas, but the test sensitivity is low. The resonant cavity method typically places the SUT inside a cavity. After the sample is placed inside, the resonant system within the cavity is disturbed. The microwave properties of the sample are determined by measuring the changes in the resonant frequency and quality factor parameters. Due to its more rigorous solution method and the high quality factor of the resonant cavity, it offers higher sensitivity and more accurate test results. However, it is difficult to fabricate for testing small, localized areas and can only perform multi-point frequency testing. When testing in different frequency bands, the cavity dimensions need to be redesigned.

[0004] Both of the above testing methods require sample preparation before testing can be performed, which is not suitable for applications requiring high uniformity and consistency of microwave parameters for thin film materials. This is because testing the uniformity and consistency of microwave parameters for thin film materials requires both the ability to detect small, localized areas and sufficient testing sensitivity to also test the properties of low-loss materials. Summary of the Invention

[0005] The purpose of this invention is to provide a high-sensitivity coaxial resonant testing device for small-area microwave testing. This device combines the testing requirements of high sensitivity and small-area detection, thereby expanding its application range.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-sensitivity coaxial resonant test device for small-area microwave testing includes a coaxial resonant cavity, a short-circuit cover, a coaxial connector with a flange, and a probe.

[0008] The coaxial resonant cavity includes an outer conductor, inside which is an inner conductor coaxial with the outer conductor. The outer wall of the inner conductor and the inner wall of the outer conductor do not contact each other. The inner conductor is a combination of a cylinder and a cone, with the cone located at one end of the cylinder and seamlessly connected to the cylinder. The other end of the cylinder is fixed at the center of the short-circuit cover. The outer conductor is a combination of a hollow cylinder and a hollow truncated cone. The upper end face of the hollow cylinder is fixedly connected to the short-circuit cover, and the lower end face of the hollow truncated cone is fixedly connected to a coaxial connector with a flange.

[0009] The short-circuit cover plate is provided with two coupling devices, which are symmetrically distributed on both sides of the center position of the short-circuit cover plate and extend through the short-circuit cover plate into the cavity of the outer conductor for coupling excitation and reception.

[0010] The coaxial connector with a flange also has an inner conductor and an outer conductor, with the outer conductor connected to the outer conductor of the coaxial resonant cavity;

[0011] One end of the probe passes through the inner conductor of the coaxial connector with a flange and then plugs into the inner conductor of the coaxial resonant cavity.

[0012] Furthermore, the short-circuit cover plate is provided with two coupling holes, and each of the two coupling devices extends into the outer conductor cavity through one coupling hole.

[0013] Furthermore, both coupling devices are SMA connector type magnetic coupling rings.

[0014] Furthermore, the coaxial connector with flange is connected to the outer conductor of the coaxial resonant cavity using a tenon and mortise joint to ensure good electrical continuity of the inner conductor, reduce higher-order modes, and achieve better impedance matching.

[0015] Furthermore, the ratio of the cylindrical height to the conical height of both the outer and inner conductors of the coaxial resonant cavity is 2:1.

[0016] Furthermore, the probe has a cylindrical structure or a planar structure.

[0017] By adopting the above technical solution, the present invention has the following advantages:

[0018] 1) This invention connects a coaxial resonant cavity to a probe to construct a quarter-wavelength coaxial resonator. Since the coaxial resonant cavity is not filled with dielectric material, it has a larger size and a higher quality factor than the coaxial probe at the lower end, thus having the advantage of high detection sensitivity. The probe has the advantage of small-area detection. The two are connected by a coaxial connector with a flange, so that the device has the advantages of both high sensitivity and small-area detection.

[0019] 2) The probe of this invention can be selected to adopt a cylindrical or planar structure according to requirements. During the setup process, the probe is connected to the conductor inside the coaxial resonant cavity via a plug-in method. With the help of a coaxial connection with a flange, probes of different lengths can be replaced and stable operation can be achieved. By changing the length of the probe, the resonant frequency of the entire coaxial resonator can be changed, so that the test device is not limited to multi-frequency testing, but can also perform testing over a wide frequency range. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a high-sensitivity coaxial resonant testing device for small-area microwave testing proposed in this invention.

[0021] Figure 2 This is a schematic diagram of the conductor structure inside the coaxial resonant cavity of a high-sensitivity coaxial resonant testing device for small-area microwave testing proposed in this invention.

[0022] Figure 3 This is a schematic diagram of the coaxial resonant cavity outer conductor structure of a high-sensitivity coaxial resonant testing device for small-area microwave testing proposed in this invention.

[0023] Figure 4 This is a schematic diagram of a test system for a high-sensitivity coaxial resonant test device for small-area microwave testing proposed in this invention;

[0024] Figure 5 The image shows the test results of a polyethylene film using a high-sensitivity coaxial resonant testing device for small-area microwave testing proposed in this invention.

[0025] Figure label:

[0026] 1. Coupling device; 2. Short-circuit cover; 3. Coaxial resonant cavity; 4. Shaft connector with flange; 5. Probe; 2-1. Cylinder constituting the inner conductor; 2-2. Cone constituting the inner conductor; 2-3. Cylindrical drill hole; 3-1. Outer conductor fixing hole; 3-2. Cavity of outer conductor; 3-3. Boss; 4-1. Test platform; 4-2. Three-dimensional moving platform; 4-3. L-shaped bracket; 4-4. Sample lifting platform; 4-5. Coaxial resonant probe tester. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 , Figure 2 , Figure 3 As shown in the figure, this embodiment provides a high-sensitivity coaxial resonance testing device for small-area microwave testing, including a coaxial resonant cavity 3, a short-circuit cover plate 2, a coaxial connector 4 with a flange, and a probe 5.

[0029] The coaxial resonant cavity includes an outer conductor, within which is an inner conductor coaxial with the outer conductor. The outer wall of the inner conductor and the inner wall of the outer conductor do not contact each other. The inner conductor is a combination of a cylinder 2-1 and a cone 2-2. The cone 2-2 is located at one end of the cylinder 2-1 and is seamlessly connected to it. The other end of the cylinder 2-1 is fixed at the center of the short-circuit cover 2. The tip of the cone 2-2 has a blind hole along the cylindrical direction; the blind hole is a cylindrical drill hole 2-3. The outer conductor is a combination of a hollow cylinder and a hollow truncated cone. The upper end face of the hollow cylinder is fixedly connected to the short-circuit cover 2, and the lower end face of the hollow truncated cone is fixedly connected to a coaxial connector 4 with a flange. The ratio of the length of the cylindrical portion to the length of the conical portion of both the outer and inner conductors of the coaxial resonant cavity is 2:1. When the hollow cylinder of the outer conductor is fixed to the short-circuit cover plate 2, an outer conductor fixing hole 3-1 can be opened on the short-circuit cover plate 2 to achieve fixation.

[0030] Two coupling devices 1 are provided on the short-circuit cover plate 2, symmetrically distributed on both sides of the center position of the short-circuit cover plate 2, and extending through the short-circuit cover plate 2 into the cavity 3-2 of the outer conductor for coupling excitation and reception. Both coupling devices 1 are magnetic coupling rings in the form of SMA connectors. The short-circuit cover plate 2 has two coupling holes, and each coupling device extends into the cavity 3-2 of the outer conductor through one coupling hole. Both coupling devices 1 are fixed in the coupling holes with screws, and after fixing, the line connecting their centers is perpendicular to the axis of the coaxial resonant cavity 2.

[0031] The flanged coaxial connector 4 also has an inner conductor and an outer conductor, with the outer conductor connected to the outer conductor of the coaxial resonant cavity. For ease of disassembly and reassembly, this embodiment uses a tenon-and-mortise joint to connect the flanged coaxial connector 4 to the outer conductor of the coaxial resonant cavity. Specifically, a boss 3-3 is provided at the bottom of the hollow frustum-shaped outer conductor of the coaxial resonant cavity, and a recessed platform on the flanged coaxial connector 4 is adapted to the boss 3-3. During assembly, the boss and recessed platform are directly mated to achieve a seamless connection, thus ensuring the airtightness of the coaxial resonant cavity. The probe 5 has a cylindrical or planar structure. One end of the probe 5 passes through the inner conductor of the flanged coaxial connector and is inserted into the cylindrical drill hole 2-3 in the inner conductor of the coaxial resonant cavity. In use, the inner conductor of the flanged coaxial connector ensures the stability of the connection between the probe and the coaxial resonant cavity.

[0032] Example 1

[0033] The high-sensitivity coaxial resonant testing device for small-area microwave testing described above is fabricated according to the following dimensions: Specifically, the radius of the cylinder 2-1 of the inner conductor of the coaxial resonant cavity is 2.5 mm, and the radius of the end of the cone is 0.9 mm. The radius of the hollow cylinder of the outer conductor of the coaxial resonant cavity is 8.7 mm, and the radius of the end of the hollow cone is 2.1 mm. The height of the hollow cylinder of the outer conductor of the coaxial resonant cavity is 20 mm, and the height of the hollow cone is 10 mm. Two coupling holes are symmetrically arranged at a distance of 7.3 mm from the axis of the coaxial resonant cavity 3. The coupling device 1 is an SMA connector type magnetic coupling ring, and the plane of the ring is perpendicular to the axis of the coaxial resonant cavity 3.

[0034] Based on the aforementioned high-sensitivity coaxial resonance testing device for small-area microwave testing, this embodiment constructs a testing system. For example... Figure 4 As shown, the testing system includes a testing platform 4-1, a three-dimensional moving platform 4-2, an L-shaped bracket 4-3, a sample lifting platform 4-4, and a coaxial resonant probe tester 4-5. The three-dimensional moving platform 4-2 and the sample lifting platform 4-4 are fixed on the testing platform 4-1. The L-shaped bracket 4-3 is an inverted "L" shape, with one side movably fixed on the three-dimensional moving platform 4-2 and the other side parallel to the sample lifting platform 4-4. The aforementioned high-sensitivity coaxial resonant tester for small-area microwave testing is installed on the other side of the L-shaped bracket 4-3, with its probe facing the sample lifting platform 4-4 after installation.

[0035] During testing, the two ports of the vector network analysis are connected to coupling device 1 in the high-sensitivity coaxial resonance testing device for small-area microwave testing, respectively, to measure the resonance frequency without material. The polyethylene film is placed on the sample lifting platform 4-4, and the probe of the coaxial resonance testing device 4-5 is positioned on the polyethylene film by adjusting the three-dimensional moving platform 4-2. The resonance frequency is measured at this time, and the change of the resonance frequency before and after the material is added is observed.

[0036] The testing system was used to test polyethylene films with a thickness of tens of micrometers. The results of the resonant frequency change before and after the test are shown in the figure below. Figure 5 As shown, the resonant point has a significant shift, with a shift of 16.26MHz.

[0037] In summary, the high-sensitivity coaxial resonant testing device for small-area microwave testing provided in this embodiment introduces a probe structure based on a traditional coaxial resonant cavity, thereby constructing a quarter-wavelength coaxial resonator with one end open and the other short-circuited. Connecting the coaxial probe to the coaxial cavity effectively extends the original coaxial cavity, giving the coaxial resonator a larger size. Due to the larger size of the coaxial resonant cavity and the absence of dielectric filling, this device has a high quality factor and high testing sensitivity. The probe is connected to the conductor inside the coaxial resonant cavity via a plug-in connection, allowing it to be replaced as needed. By replacing probes of different lengths, the device length can be adjusted to suit broadband testing, solving the problem of broadband testing. Compared to traditional half-wavelength or quarter-wavelength resonators, the resonant testing device in this embodiment fully considers both high sensitivity and small-area detection requirements.

[0038] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A high-sensitivity coaxial resonant testing device for small-area microwave testing, comprising a coaxial resonant cavity, a short-circuit cover, a coaxial connector with a flange, and a probe, characterized in that: The coaxial resonant cavity includes an outer conductor, inside which is an inner conductor coaxial with the outer conductor. The outer wall of the inner conductor and the inner wall of the outer conductor do not contact each other. The inner conductor is a combination of a cylinder and a cone, with the cone located at one end of the cylinder and seamlessly connected to it. The other end of the cylinder is fixed at the center of the short-circuit cover. The outer conductor is a combination of a hollow cylinder and a hollow truncated cone, with the hollow truncated cone located at one end of the hollow cylinder. The upper end face of the hollow cylinder is fixedly connected to the short-circuit cover, and the lower end face of the hollow truncated cone is fixedly connected to a coaxial connector with a flange. The short-circuit cover plate is provided with two coupling devices, and the center line connecting the two coupling devices is perpendicular to the axis of the coaxial resonant cavity. The two coupling devices are symmetrically distributed on both sides of the center position of the short-circuit cover plate and extend through the short-circuit cover plate into the cavity of the outer conductor for coupling excitation and reception. The flanged coaxial connector also has an inner conductor and an outer conductor, with the outer conductor connected to the outer conductor of the coaxial resonant cavity; the inner conductor of the flanged coaxial connector is used to ensure the stability of the connection between the probe and the coaxial resonant cavity. One end of the probe passes through the inner conductor of the coaxial connector with a flange and is then inserted into the inner conductor of the coaxial resonant cavity. The probe is connected to the coaxial resonant cavity to form a quarter-wavelength coaxial resonator.

2. The high-sensitivity coaxial resonance testing device for small-area microwave testing as described in claim 1, characterized in that: The short-circuit cover plate is provided with two coupling holes, and each of the two coupling devices extends into the outer conductor cavity through one coupling hole.

3. The high-sensitivity coaxial resonance testing device for small-area microwave testing as described in claim 1, characterized in that: Both coupling devices are SMA connector type magnetic coupling rings.

4. The high-sensitivity coaxial resonance testing device for small-area microwave testing as described in claim 1, characterized in that: The coaxial connector with flange is connected to the outer conductor of the coaxial resonant cavity by a tenon and mortise joint.

5. A high-sensitivity coaxial resonance testing device for small-area microwave testing as described in claim 1, characterized in that: The ratio of the length of the cylindrical portion to the length of the tapered portion of both the outer and inner conductors of the coaxial resonant cavity is 2:

1.

6. A high-sensitivity coaxial resonance testing device for small-area microwave testing as described in any one of claims 1 to 5, characterized in that: The probe has a cylindrical or planar structure.

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