Dielectric constant test device based on TM0np mode parallel plate dielectric resonator

Abstract

The present invention belongs to the field of microwave testing technology and specifically provides a dielectric constant testing device based on a TM0np mode parallel plate dielectric resonator, which is used to solve the problem of limited operating modes when traditional dielectric resonators are used to measure the complex dielectric constant of dielectric materials. The present invention comprises: an upper metal plate, a lower metal plate, a dielectric material, a concentric device, an upper coupling probe, a lower coupling probe, and a probe adjustment device. The dielectric material is arranged between the upper and lower metal plates, and the three are connected by the concentric device to form a concentric dielectric resonator. The upper and lower metal plates are both provided with coupling holes at their centers, and the upper and lower coupling probes are correspondingly arranged. The dielectric resonator uses a coupling method of probes located on the outer surfaces (upper and lower surfaces) of the upper and lower metal plates to excite the TM0np mode. When performing complex dielectric constant testing of microwave dielectric materials based on this resonator, high-precision testing can be achieved and multi-mode operation can be performed.

Description

Technical Field

[0001] The present invention belongs to the field of microwave testing technology, and specifically provides a dielectric constant testing device based on a TM0np-mode parallel plate dielectric resonator. Background Art

[0002] In recent years, dielectric properties have played a crucial role in the widespread application of electromagnetic shielding and absorbing materials, as well as in the development of wave-transmitting materials in the radio field. Dielectric parameters such as the dielectric constant ε and dielectric loss tanδ, measured under microwave conditions, are important indicators of a material's electromagnetic performance. Therefore, accurately measuring these parameters in practical applications is crucial for their application. The complex dielectric constant is a key electromagnetic parameter of dielectric materials. Currently, electromagnetic parameter testing methods in the microwave and millimeter wave bands can be categorized into network parameter methods and resonance methods based on the test principle. Typical network parameter methods include transmission-reflection methods, time-domain methods, and free-space methods. These methods offer wide test bands, high test speeds, and a wide range of test frequencies, but their accuracy is lower than that of resonance methods, making them inadequate for high-precision testing. Typical resonance methods include the resonant perturbation method, resonant cavity method, quasi-optical cavity method, and dielectric resonator method. Compared to network parameter methods, resonance methods have narrower test bands, slower test speeds, and fewer test frequencies, but offer higher accuracy.

[0003] The concept and theory of dielectric resonators were first proposed by Richtmyer in 1939. However, due to the lack of suitable dielectric materials, the theory lay dormant for over 20 years, with no practical development. Dielectric resonators only gained further attention in 1962, when Okaya and Barash described the theoretical and experimental results of TiO2 and SrTiO3 dielectric resonators. Dielectric resonators, with their advantages of miniaturization, light weight, high quality factor, low loss, high dielectric constant, excellent frequency and temperature stability, and ease of integration, are widely used in microwave communications, radar navigation, electronic countermeasures, satellite relay, missile guidance, and test instrumentation. They are indispensable components in microwave and millimeter-wave systems. In recent years, a variety of dielectric resonator-based test devices for measuring the electromagnetic parameters of dielectric materials have emerged in the microwave and millimeter-wave bands. However, traditional dielectric resonators have limited operating modes for measuring the complex dielectric constant of dielectric materials. Therefore, designing dielectric resonators for multimode operation has become a research priority. Summary of the Invention

[0004] The present invention aims to address the problem of limited operating modes when measuring the complex dielectric constant of a dielectric material using a conventional dielectric resonator. A dielectric constant testing device based on a TM0np mode parallel plate dielectric resonator is proposed. The dielectric material and upper and lower metal plates in the resonator are formed by a concentric arrangement. The TM0np mode is excited by coupling probes located on the outer surfaces of the upper and lower metal plates. This resonator can achieve high-precision testing of the complex dielectric constant of microwave dielectric materials, enabling multi-mode operation.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A dielectric constant testing device based on a TM0np mode parallel plate dielectric resonator includes: an upper metal plate of the resonator, a lower metal plate of the resonator, a dielectric material, a resonator concentric device, an upper coupling probe, a lower coupling probe, and a probe adjustment device. The device is characterized in that the dielectric material is arranged between the upper metal plate of the resonator and the lower metal plate of the resonator, and the three form a concentric structure through the resonator concentric device and together constitute a dielectric resonator; coupling through holes are provided at the center positions of the upper metal plate of the resonator and the lower metal plate of the resonator, and an upper coupling probe and a lower coupling probe are correspondingly arranged; the upper coupling probe and the lower coupling probe are connected to the probe adjustment device.

[0007] Furthermore, the upper metal plate of the resonator and the lower metal plate of the resonator are arranged parallel to each other and are both made of circular metal plates of the same size.

[0008] Furthermore, the upper coupling probe and the lower coupling probe are both coaxial probes, which are correspondingly arranged at the coupling through holes of the upper metal plate and the lower metal plate of the resonator. The upper coupling probe is located on the upper surface of the upper metal plate of the resonator, and the lower coupling probe is located on the lower surface of the lower metal plate of the resonator; the diameter of the coupling through hole matches the outer diameter of the coupling probe, and the depth of the coupling probe in the coupling through hole is adjusted by the probe adjustment device to achieve coupling adjustment and reach a weak coupling state.

[0009] Furthermore, the resonator concentric device is configured to be in a circular ring shape, with an outer diameter being as large as the upper and lower metal plates of the resonator and an inner diameter being as large as the dielectric material.

[0010] Based on the above technical solution, the beneficial effects of the present invention are:

[0011] The present invention provides a dielectric constant testing device based on a TM0np-mode parallel-plate dielectric resonator. Unlike the conventional ring coupling method of dielectric resonators, the present invention adopts a top-to-bottom probe coupling method and a concentric device to enable the resonator to operate in the TM0np mode. Ultimately, the present invention has the advantage of achieving broadband multimode testing within the measured frequency range using a single sample to be tested, facilitating the testing of dielectric materials within a wide frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the structure of the dielectric constant testing device based on the TM0np mode parallel plate dielectric resonator in the present invention.

[0013] Figure 2 This is a schematic diagram of the TM0np-mode parallel plate dielectric resonator in the present invention.

[0014] Figure 3 This is a schematic diagram of a traditional dielectric resonator (ring coupling). DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention is further described in detail below with reference to embodiments and drawings.

[0016] This embodiment provides a dielectric constant test device based on a TM0np-mode parallel plate dielectric resonator, the structure of which is as follows: Figure 1 As shown, it includes: upper and lower metal plates 1 of the resonator, a dielectric material 2, a resonator concentric device 3, upper and lower coupling probes 4, and a probe adjustment device 5; wherein the dielectric material is located between the upper and lower metal plates of the resonator, the upper and lower coupling probes and the probe adjustment device are respectively arranged on the outer surfaces (upper surface and lower surface) of the upper and lower metal plates, and the dielectric material and the upper and lower metal plates achieve a concentric effect through the resonator concentric device;

[0017] The dielectric material is pressed tightly by the upper and lower metal plates of the resonator, forming the dielectric resonator part together with the upper and lower metal plates. The dielectric material and the upper and lower metal plates are concentrically connected by the resonator concentric device to achieve the purpose of only exciting the TM0np mode and avoiding the generation of TMmnp mode in the non-concentric state.

[0018] The upper and lower metal plates of the resonator are parallel to each other and are both made of circular metal plates. Specifically, they are two cylinders with the same radius and thickness and are parallel to each other. A coupling hole is set at the center of each.

[0019] The coupling probes are two coaxial probes, which are respectively set at the coupling holes at the center of the upper and lower metal plates of the resonator. The diameter of the coupling holes set at the center of the metal plates matches the outer diameter of the coupling probes.

[0020] The resonator concentric device is set to a circular ring shape, with an outer diameter equal to the upper and lower metal plates and an inner diameter equal to the dielectric material; the material of the resonator concentric device is preferably a high-hardness, easy-to-process acrylic material.

[0021] Based on the above dielectric constant test device, the calculation method of the complex dielectric constant is:

[0022] Based on the electromagnetic theory of parallel plate waveguides, the lower and upper operating frequency limits of the TM0np mode are:

[0023]

[0024]

[0025] Where c0 is the speed of light in free space, d s is the thickness of the dielectric material, f c coax is the cutoff frequency of the coaxial line that excites the resonator (for a 1.0 mm coaxial line, f c coax =133GHz), ε rs and ε ra are the dielectric constants of the dielectric material and air, respectively, n and p represent the number of half-standing waves distributed along the radial and longitudinal directions of the electromagnetic field, respectively;

[0026] E z The wave equation that is satisfied is derived from Maxwell's equations as follows:

[0027]

[0028] Considering the TM0np mode, the solution of the above equation is given by:

[0029] E z1 =A np J0(k r1 ρ)cos(β1z)(4)

[0030] E z2 =B np K0(k r2 ρ)cos(β2z)(5)

[0031] Wherein, subscripts 1 and 2 represent the dielectric region and free space region, respectively.

[0032]

[0033]

[0034]

[0035]

[0036] A np and B np is a coefficient determined according to the boundary conditions, β is the axial wave number, J0(x) and K0(x) are the first kind Bessel function and the second kind modified Bessel function, respectively;

[0037] The other field components of TM0np can be obtained by substituting equations (4) to (5) into the following relationships:

[0038]

[0039]

[0040] The following characteristic equation of the TM0np mode can be derived from the continuity conditions of the tangential components of E and H between the dielectric region and the free space region:

[0041]

[0042] By solving equation (12), the relative dielectric constant ε is derived from the measured resonant frequency and size parameters rs ; When solving equation (12), all the field components in each region can be determined; then, the loss tangent tanδ can be obtained from the Q of the PPDR resonator using the following equation u (no-load Q factor) to obtain:

[0043]

[0044] Among them, Q c is the Q factor due to conductor loss; W s and W a are the electrical energies stored in the dielectric region and the air region, respectively, which can be calculated by the following integral expressions:

[0045]

[0046]

[0047] Q c It can be approximated as:

[0048]

[0049] Where δ is the skin depth of the conductor, σ is the electrical conductivity, and μ0 is the magnetic permeability of free space.

[0050] The schematic diagram of the dielectric constant test device based on the TM0np mode parallel plate dielectric resonator in this embodiment is as follows: Figure 2 As shown in the figure, the conventional dielectric constant test device of dielectric resonator is shown in the figure Figure 3 As shown, from Figure 2 、 Figure 3 It can be seen from the comparison results that the dielectric constant testing device based on the TM0np-mode parallel plate dielectric resonator of the present invention can realize multi-mode testing in a wide frequency range without the influence of stray modes.

[0051] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A dielectric constant test device based on a TM0np-mode parallel plate dielectric resonator, comprising: A resonator upper metal plate, a resonator lower metal plate, a dielectric material, a resonator concentric device, an upper coupling probe, a lower coupling probe, and a probe adjustment device; characterized in that the dielectric material is arranged between the upper metal plate and the lower metal plate of the resonator, and the three form a concentric structure through the resonator concentric device and together constitute a dielectric resonator; coupling through holes are provided at the center positions of the upper metal plate and the lower metal plate of the resonator, and upper coupling probes and lower coupling probes are correspondingly arranged; the upper coupling probe and the lower coupling probe are connected to the probe adjustment device.

2. The dielectric constant testing device based on the TM0np mode parallel plate dielectric resonator according to claim 1, characterized in that: The upper metal plate of the resonator and the lower metal plate of the resonator are arranged parallel to each other and are both made of circular metal plates of the same size.

3. The dielectric constant testing device based on the TM0np mode parallel plate dielectric resonator according to claim 1, characterized in that: The upper coupling probe and the lower coupling probe are both coaxial probes, which are correspondingly arranged at the coupling holes of the upper metal plate and the lower metal plate of the resonator. The diameter of the coupling hole matches the outer diameter of the coupling probe. The depth of the coupling probe in the coupling hole is adjusted by the probe adjustment device to adjust the coupling amount and achieve a weak coupling state.

4. The dielectric constant testing device based on the TM0np mode parallel plate dielectric resonator according to claim 1, characterized in that: The resonator concentric device is arranged in a circular ring shape, with an outer diameter equal to that of the upper and lower metal plates of the resonator and an inner diameter equal to that of the dielectric material.

Images