CN-115932412-B - Millimeter wave dielectric test system and method for low-loss material under action of low-frequency microwave electric field

CN115932412BCN 115932412 BCN115932412 BCN 115932412BCN-115932412-B

Abstract

The invention aims to provide a millimeter wave dielectric test system and method for a low-loss material under the action of a low-frequency microwave electric field, and belongs to the technical field of microwave and millimeter wave dielectric material tests. The dielectric testing system combines the quasi-optical cavity and the rectangular resonant cavity, adjusts the electric field intensity at the position of the low-loss material by controlling the size of the input excitation signal through the rectangular resonant cavity so as to simulate the external environment, tests the millimeter wave band dielectric property of the material to be tested through the quasi-optical cavity method, avoids the problems of mode interference between the excitation signal and the test signal, large span of the frequency band in the vector network analyzer during testing and the like, and greatly improves the testing accuracy.

Inventors

GAO YONG
ZHANG WEI
LI XINGXING
ZOU YIXUAN
SHEN RONGHUA
ZHU HUI
ZHANG YUNPENG
GAO CHONG
YU CHENGYONG
LI EN
XIE CHUNMAO

Assignees

电子科技大学

Dates

Publication Date: 20260508
Application Date: 20221207

Claims (7)

1. The millimeter wave dielectric testing system for the low-loss material under the action of the low-frequency microwave electric field is characterized by comprising a first vector network analyzer (1), a second vector network analyzer (2), a first isolator (3), a power amplifier (4), a second isolator (5), a directional coupler (6), a matching load (11), a microwave electric probe (12), a rectangular resonant cavity (13), a quasi-optical cavity spherical mirror (14), a first quasi-optical cavity coaxial coupling ring (15), a second quasi-optical cavity coaxial coupling ring (16) and a quartz test tube (17); The input end of the first isolator (3) and the coupling end (9) of the directional coupler are respectively connected with two ports of the first vector network analyzer (1), the output end of the first isolator (3) is sequentially connected with the power amplifier (4), the second isolator (5) and the output end (7) of the directional coupler (6), the input end (8) of the directional coupler (6) is connected with the microwave electric probe (12), the isolation end (10) of the directional coupler is connected with the matching load (11), the microwave electric probe (12) is arranged in a cavity at one end of the rectangular resonant cavity (13), a quartz test tube (17) with an opening at the top is arranged in a cavity at the other end of the rectangular resonant cavity (13), the height of the quartz test tube is the same as that of the rectangular resonant cavity, and the quartz test tube (17) is arranged at a quarter cavity of the rectangular resonant cavity (13) close to the other end; The quasi-optical cavity spherical mirror (14) is arranged right above the quartz test tube (17), the normal line at the center of the quartz test tube passes through the spherical center of the quasi-optical cavity spherical mirror, a material (18) to be tested is placed at the bottom center of the quartz test tube (17), the first quasi-optical cavity coaxial coupling ring (15) and the second quasi-optical cavity coaxial coupling ring (16) are symmetrically arranged on the quasi-optical cavity spherical mirror (14), and the first quasi-optical cavity coaxial coupling ring (15) and the second quasi-optical cavity coaxial coupling ring (16) are respectively connected with two ends of the second vector network analyzer (2).
2. The millimeter wave dielectric test system for low-loss materials under the action of a low-frequency microwave electric field according to claim 1, wherein the microwave electric probe (12) is used for injecting excitation signals into the rectangular resonant cavity (13), the directional coupler (6) is used for accurately acquiring the power of the excitation signals actually injected into the rectangular resonant cavity (13), the power amplifier (4) is used for amplifying the power of the excitation signals, and the first isolator (3) and the second isolator (5) are used for reducing the influence of reflected signals on the first vector network analyzer (1) and the power amplifier (4).
3. A millimeter wave dielectric test system for low-loss materials under the action of low-frequency microwave electric field according to claim 1, characterized in that the radius of said quartz cuvette (17) should be larger than the beam waist radius of gaussian beam at the same height.
4. The millimeter wave dielectric test system for low-loss materials under the action of low-frequency microwave electric field according to claim 1, wherein the surface of the quasi-optical cavity spherical mirror (14) is silver-plated.
5. The millimeter wave dielectric test system for low-loss materials under the action of a low-frequency microwave electric field according to claim 1, wherein the rectangular resonant cavity (13) is a standard rectangular resonant cavity, and the distance D 2 between the center of the quasi-optical cavity spherical mirror (14) and the top of the quartz test tube (17) is equal to the difference between the quasi-optical cavity length D and the height D of the rectangular resonant cavity.
6. A method for dielectric testing of low loss material based on the millimeter wave dielectric test system of low loss material under the action of low frequency microwave electric field as claimed in any one of claims 1-5, comprising the steps of: step 1, adjusting the distance d 2 between the center of the quasi-optical cavity spherical mirror and the top of the quartz test tube, wherein a resonance peak appears on a second vector network analyzer; Step 2, fixing the position of the quasi-optical cavity spherical mirror in the step 1, and performing cavity test without placing a material to be tested, and recording the cavity resonance frequency f 0 at the moment by using a second vector network analyzer; Step 3, placing the material to be tested at the center of the bottom of the quartz test tube, and testing the resonant frequency f L of the material to be tested under the required microwave electric field intensity by using a second vector network analyzer; Step 4, calculating the dielectric constant epsilon r of the material to be measured according to the resonant frequency f L of the material to be measured, which is measured in the step 3, and the cavity resonant frequency f 0 , which is measured in the step 2, wherein the calculation process is specifically that, ε r ＝n 2 (4) Wherein R 0 is the curvature radius of the quasi-optical cavity, t is the thickness of the material to be measured, n is the refractive index of the sample to be measured, omega 0 is the beam waist radius of the quasi-optical cavity, D is the cavity length of the quasi-optical cavity, c is the propagation speed of electromagnetic waves, q is the number of longitudinal modes of the resonant electromagnetic field in the quasi-optical cavity, k is the wave number when the quasi-optical cavity loads the sample to be measured, and D 1 , D' and s 0 are all intermediate variables.
7. The method of dielectric testing of low loss material according to claim 6, wherein the microwave electric field strength in step 3 is changed by adjusting the input power of the first vector network analyzer, and the relationship between the microwave electric field strength and the input power is specifically: The excitation signal frequency is adjusted to enable the rectangular resonant cavity to work in TE 102 mode, and for the TE 102 mode of the rectangular resonant cavity, the electromagnetic field distribution in the cavity is as follows: Wherein E 0 is the intensity amplitude of the low-frequency microwave electric field, Z TE is the wave impedance of TE mode, eta is the free space wave impedance, a is the length of the rectangular resonant cavity, and d is the height of the rectangular resonant cavity; If only the cavity wall causes conduction loss in the rectangular resonant cavity, the cavity loss P c is: Wherein H t is tangential magnetic field component of cavity wall surface, b is width of rectangular resonant cavity, R s is surface resistance of rectangular resonant cavity, lambda is electromagnetic wave working wavelength in resonance, eta is wave impedance; The quality factor Q c for the rectangular cavity is: Wherein k 1 is the wave number when the rectangular resonant cavity resonates, and omega 0 is the resonant angular frequency; When the rectangular resonant cavity is in a resonant state, the electric field energy storage W e is equal to the magnetic field energy storage W m , Wherein epsilon is the dielectric constant in the rectangular resonant cavity, The conjugation of E y is adopted, and V is the internal volume of the rectangular resonant cavity; Assuming that the microwave input power P TE102 to excite the cavity is injected into the cavity entirely, only the cavity wall metal loss P c is considered, defined by the quality factor: The electric field intensity maximum values of the rectangular resonant cavity and the material to be tested are obtained by the simultaneous formulas (5), (6), (7), (8) and (9):

Description

Millimeter wave dielectric test system and method for low-loss material under action of low-frequency microwave electric field Technical Field The invention belongs to the technical field of microwave and millimeter wave dielectric material testing, and particularly relates to a system and a method for testing low-loss materials under the action of a low-frequency microwave electric field. Background The microwave electromagnetic material is an important component of the current material science and is widely applied to the fields of millimeter wave communication and the like. The low-loss electromagnetic material has wide application range and is used in microwave devices such as dielectric waveguides, dielectric blocks in coaxial lines, circuit substrates, antenna covers and the like, so that the low-loss electromagnetic material belongs to one of important branches of the microwave electromagnetic material. With the development of technology, low-loss materials are increasingly applied to the millimeter wave device field, and meanwhile, dielectric constant is one of the most basic parameters for describing the characteristics of the low-loss materials. If the dielectric property of the low-loss material can be mastered in advance and the targeted design is carried out before the low-loss material is selected, the performance of the millimeter wave device can be effectively ensured. With the rapid development of communication and Internet of things application, various miniaturized and low-power-consumption base stations are densely distributed in future wireless communication systems, electromagnetic energy of space electromagnetic radiation is increased year by year, but millimeter wave devices are easily affected by external electromagnetic interference, and stability and safety of the devices are affected. Therefore, it is important to test the dielectric of the low-loss material in millimeter wave band in the environment of low-frequency microwave electric field equivalent to the external space. At present, a resonant cavity method is often used for dielectric property test of a low-loss material, but little research is carried out on millimeter wave frequency band test of dielectric constant of the low-loss material in a low-frequency microwave electric field environment. The university of electronic technology Li En team (Gao Yong. Research on microwave dielectric properties under high power of typical materials [ D ]. University of electronic technology, 2019.) proposes to test and research on dielectric properties of materials under the action of low-frequency microwave electric field by using multi-mode properties of resonant cavities, but the research is that the materials under the action of low-frequency microwave electric field are tested in dielectric constants of low-frequency microwave wave bands, namely, the generated microwave electric field environment and microwave signals for testing dielectric properties of the materials are almost in the same frequency band or adjacent frequency bands. If the test frequency band is adjusted to the millimeter wave band, the problems that firstly, a single resonant cavity is difficult to cover the low frequency to millimeter wave band at the same time, and secondly, even if the single resonant cavity can cover the low frequency to millimeter wave band at the same time by a hybrid mode suppression technology, the problem of mode interference is easy to form among different modes, and the accuracy and the precision of the test are affected to a certain extent are caused. Disclosure of Invention Aiming at the problems existing in the background technology, the invention aims to provide a millimeter wave dielectric test system and a millimeter wave dielectric test method for a low-loss material under the action of a low-frequency microwave electric field. The test system combines the quasi-optical cavity and the rectangular resonant cavity, adjusts the electric field intensity of the position where the low-loss material is positioned by controlling the size of an input excitation signal through the rectangular resonant cavity so as to simulate the external environment, and avoids the problems of large frequency band span and mode interference caused by excitation and test in the rectangular resonant cavity by a quasi-optical cavity method, so that the test result is more accurate. In order to achieve the above purpose, the technical scheme of the invention is as follows: The low-loss material millimeter wave dielectric test system under the action of a low-frequency microwave electric field comprises a first vector network analyzer 1, a second vector network analyzer 2, a first isolator 3, a power amplifier 4, a second isolator 5, a directional coupler 6, a matching load 11, a microwave electric probe 12, a rectangular resonant cavity 13, a quasi-optical cavity spherical mirror 14, a first quasi-optical cavity coaxial coupling ring 15, a second quasi-opt