Device and method for measuring wave transmission rate of P-band radar wave-transmitting material

Abstract

The invention discloses a device and a method for measuring the wave transmission rate of a P-band radar wave-transmitting material, and belongs to the technical field of microwave testing. The specific method comprises the following steps: selecting three calibration pieces; placing a calibration piece / to-be-tested sample at a central hole of a metal screen, and respectively arranging an electromagnetic wave transmitting antenna and an electromagnetic wave receiving antenna at opposite positions on two sides of the calibration piece / to-be-tested sample; the transmitting antenna transmits electromagnetic waves, and the receiving antenna receives the electromagnetic waves transmitted by the calibration piece / the to-be-tested sample; respectively placing the three calibration pieces and the to-be-measured sample in a center hole of the metal screen, and measuring and storing scattering parameters S21 of the three calibration pieces and the to-be-measured sample; calculating to obtain theoretical values of the wave transmissivity corresponding to the three calibration pieces; and calculating the wave transmissivity of the to-be-measured sample based on the theoretical wave transmissivity values of the three calibration pieces and the measured data. According to the invention, the problem of inaccurate test caused by limiting conditions such as strict requirements on a test environment, large size of a to-be-tested sample, insufficient time resolution, no applicability of a TRL calibration method and the like in an existing wave transmission rate test method is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave testing, and in particular relates to a device and method for measuring the wave transmittance of a P-band radar wave-transmitting material. Background Art

[0002] Radar translucent material (RTM) is a material that allows electromagnetic waves to penetrate without being absorbed or reflected, thereby protecting radar equipment or systems from external interference. It plays an important role in radar technology, especially in the manufacture of aircraft radomes and antenna windows, and has certain military application value. The transmittance of radar translucent materials is an important indicator to characterize the performance of radar translucent materials. Since the transmittance changes with the angle of incidence, it is crucial to accurately measure the transmittance of radar translucent materials at different angles for material design and application.

[0003] After the production of radar wave-transmitting materials, they need to be tested for performance, such as wave transmittance test. At present, the test methods for the wave transmittance of radar wave-transmitting materials are mainly divided into two categories: focusing lens test method and far-field irradiation test method. The focusing lens method is only applicable to high-frequency bands. In the P-band, the size of the required lens antenna will be very large, which will not only greatly increase the cost, but also make the lens preparation quite difficult. In order to avoid the edge effect brought by the test sample, the far-field irradiation method often requires a larger test sample, requiring the sample size to be no less than 1.25 times the antenna receiving port surface. In the P-band, its side length needs to be one meter or even more than two meters; at the same time, it must be carried out in a microwave darkroom, which requires a wider test space and a more complex test environment, which is costly and cannot be used under environmental constraints. At the same time, these traditional wave transmittance test methods are all time domain test methods. In the high-frequency band, the time domain gating technology can effectively filter out unexpected signals such as reflection and scattering, and the measurement results are relatively accurate. However, the P-band has a narrow frequency band, and the signal converted back to the time domain has insufficient time resolution. The time domain gating technology cannot effectively separate the useful signal from the interference signal, which will cause the measurement result to be distorted and difficult to apply. At the same time, the commonly used TRL calibration method is also difficult to apply to the test of the transmittance of radar transparent materials. In summary, the test of the transmittance of radar transparent materials in the P-band is extremely inconvenient.

[0004] Therefore, a new technical solution is needed for the accurate measurement of the transmittance of P-band radar transparent materials. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a device and method for measuring the wave transmittance of a P-band radar wave transparent material. During the measurement process, a calibration piece with known wave transmittance characteristics is used to measure several calibration pieces and a sample to be tested, thereby completing an accurate measurement of the wave transmittance of the sample to be tested. The frequency domain measurement method of the present invention solves the problem of inaccurate testing caused by the existing wave transmittance test method having strict requirements on the test environment, large size of the sample to be tested, insufficient time resolution, and TRL calibration method no longer applicable, thereby achieving accurate measurement of the wave transmittance of radar wave transparent materials in the P band.

[0007] The technical solution of the present invention is: a method for measuring the wave transmittance of a P-band radar wave-transmitting material, and the specific steps are as follows:

[0008] Select three calibration pieces;

[0009] The calibration piece / sample to be tested is placed at the center hole of the metal screen, and an electromagnetic wave transmitting antenna and an electromagnetic wave receiving antenna are arranged at opposite positions on both sides thereof; the transmitting antenna transmits electromagnetic waves, and the receiving antenna receives electromagnetic waves transmitted by the calibration piece / sample to be tested;

[0010] Place the three calibration pieces and the sample to be tested in the center hole of the metal screen, measure and save the scattering parameters S of the three calibration pieces and the sample to be tested. 21 , denoted as V1, V2, V3 and V4 respectively;

[0011] The theoretical wave transmittance values ​​corresponding to the three calibration pieces are calculated and recorded as T1, T2 and T3 respectively;

[0012] Based on the theoretical values ​​of the wave transmittance of the three calibration pieces and the measured data, the wave transmittance T4 of the sample to be tested is calculated:

[0013]

[0014] in,

[0015] A further technical solution of the present invention is that the three calibration pieces are respectively a straight-through calibration piece and two polytetrafluoroethylene plates with different thicknesses.

[0016] A further technical solution of the present invention is that the sizes of the two polytetrafluoroethylene plates with different thicknesses are 450mm×450mm×5mm and 450mm×450mm×10mm respectively.

[0017] A further technical solution of the present invention is: the plane where the metal screen is located is used as a phase reference plane, and the distances between the electromagnetic wave transmitting antenna and the electromagnetic wave receiving antenna and the phase reference plane are equal.

[0018] A further technical solution of the present invention is that the distance between the electromagnetic wave transmitting antenna, the electromagnetic wave receiving antenna and the phase reference plane is 2000 mm.

[0019] A further technical solution of the present invention is: the calculation method of the theoretical value of the wave transmittance corresponding to the calibration piece is:

[0020] The theoretical transmittance value T1 of the through calibration component is set to 1;

[0021] The calculation formulas for the theoretical transmittance values ​​T2 and T3 of two PTFE plates with different thicknesses are as follows:

[0022]

[0023] in, θ t Represents the transmission angle of electromagnetic waves in the material, θ i represents the incident angle of the electromagnetic wave in the material, d1 and d2 represent the thickness of the two polytetrafluoroethylene plates respectively, R represents the reflectivity; k0 represents the propagation constant in free space; γ represents the propagation constant in the material; ε represents the dielectric constant of the material;

[0024] A further technical solution of the present invention is: the calculation formula of the reflectivity is:

[0025]

[0026] Here, d represents the thickness.

[0027] A device for measuring the wave transmittance of a P-band radar wave-transmitting material, characterized in that it comprises a metal screen assembly and an electromagnetic wave transmitting antenna and a receiving antenna arranged on both sides thereof, wherein the electromagnetic wave emitted by the transmitting antenna passes through a calibration piece / a sample to be measured placed on the metal screen assembly and is received by the receiving antenna;

[0028] The transmitting antenna and the receiving antenna are respectively connected to a vector network analyzer through microwave cables. The vector network analyzer is used to generate a test signal and process a received signal.

[0029] A further technical solution of the present invention is: the metal screen assembly includes a metal screen, a bracket and a base, the metal screen is installed on the base through the bracket, and the three are fixedly connected in a detachable manner; a plurality of lockable universal rollers are installed at the bottom of the base plate.

[0030] A further technical solution of the present invention is: pyramidal wave absorbing units are arranged on both sides of the metal screen assembly to absorb environmental electromagnetic waves and eliminate background reflections.

[0031] Beneficial Effects

[0032] The beneficial effects of the present invention are as follows: the present invention belongs to a frequency domain measurement method, which combines the measurement device with the wave transmittance calculation, and can obtain the wave transmittance of the P-band radar wave transparent material, thereby reducing the requirements for the test device, such as reducing the distance between the transmitting and receiving antennas and the size of the sample to be tested, but still having a high accuracy.

[0033] The present invention avoids the problem that the traditional time domain method in the P band cannot effectively separate the useful signal and the interference signal by using the time domain gating technology due to insufficient time resolution, resulting in distorted measurement results.

[0034] Furthermore, the metal screen assembly of the present invention is provided with pyramidal wave absorbing units on both sides and the ground to absorb environmental electromagnetic waves, eliminate background reflections, and improve accuracy. The base of the metal screen assembly of the present invention is provided with a lockable universal roller, which can conveniently move and fix the placement of the test device, and has stronger applicability. The environmental parameters are calibrated using a calibration piece with known transmittance characteristics, thereby realizing accurate measurement of the transmittance of radar-transparent materials in the P band. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Front view of the P-band radar wave-transmittance material transmittance measurement system;

[0036] Figure 2 Top view of the P-band radar wave-transmittance material transmittance measurement system at vertical incidence;

[0037] Figure 3 Top view of the P-band radar wave-transmitting material transmittance measurement system at oblique incidence;

[0038] Figure 4 Schematic diagram of the metal screen assembly structure;

[0039] Figure 5 Side view of the metal screen assembly;

[0040] Figure 6 Comparison results of the amplitude of the wave transmittance of the sample to be tested when the P band is incident vertically;

[0041] Figure 7 Phase contrast results of the transmittance of the sample under test at vertical incidence in the P band;

[0042] Figure 8 Comparison results of the amplitude of the wave transmittance of the sample under test at 45° oblique incidence in the P band;

[0043] Fig. 9 Phase contrast results of the transmittance of the sample under test at 45° oblique incidence in the P band.

[0044] Explanation of the reference numerals: 1-transmitting antenna, 2-receiving antenna, 3-vector network analyzer, 4-microwave cable, 5-metal screen assembly, 6-metal screen, 7-opening, 8-bracket, 9-base, 10-lockable universal roller. DETAILED DESCRIPTION

[0045] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0046] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0047] Based on the characteristics of the P-band, the use of traditional transmittance testing methods will result in insufficient time resolution, huge size of the sample to be tested, and the TRL calibration method is no longer applicable, resulting in inaccuracy when testing the transmittance of radar transparent materials, and high cost and difficulty in application. The present invention proposes a measuring device for the transmittance of P-band radar transparent materials, including a metal screen assembly 5, a transmitting antenna 1 and a receiving antenna 2 located on both sides of the metal screen assembly 5, the transmitting antenna 1 is used to transmit electromagnetic waves, and the receiving antenna 2 is used to receive electromagnetic waves; the height of the transmitting and receiving antennas relative to the ground can be adjusted so that the electromagnetic waves emitted by the transmitting antenna can be aimed at the sample to be tested, and the electromagnetic waves transmitted by the sample to be tested can be received by the receiving antenna; the transmitting and receiving antennas can be rotated 90° around their own radiation axis to achieve switching between vertical polarization incidence and parallel polarization incidence; the transmitting and receiving antennas are connected to a vector network analyzer 3 via a microwave cable 4, and the vector network analyzer 3 is used to generate test signals and process received signals;

[0048] The metal screen assembly 5 includes a metal screen 6, a bracket 8 and a base 9. The metal screen 6, the bracket 8 and the base 9 are detachably connected. The middle opening of the metal screen 5 is used to place the sample to be tested or the calibration piece. The bracket 8 is fixed on both sides of the metal screen 5. The four corners of the bottom of the base 9 are respectively installed with lockable universal rollers 10; the pyramid absorbing units are placed on both sides of the metal screen assembly 5 and on the ground to absorb environmental electromagnetic waves, eliminate background reflections, and improve accuracy; rotating the metal screen assembly can achieve adjustment of the incident angle within a wide range.

[0049] The plane where the metal screen 6 is located is defined as the reference plane. The mobile metal screen assembly 5 can realize electromagnetic wave incidence at different angles. Three calibration pieces are respectively placed on the platform at the central opening 7 of the metal screen 6. The three calibration pieces can be a straight-through calibration piece and two flat materials with known wave transmittance, or three flat materials with known wave transmittance. The wave transmittance measurement values ​​of the three calibration pieces are calculated, and the parameter settings of the field test equipment for the wave transmittance of the wave transparent material are kept unchanged. The calibration piece is removed and replaced with the sample to be tested to obtain the wave transmittance measurement value of the sample to be tested. The above four wave transmittance measurement values ​​and the theoretical wave transmittance values ​​of the three calibration pieces are used, and the environmental parameters are calibrated using the calibration piece with known wave transmittance characteristics, so that the accurate measurement of the wave transmittance of the radar transparent material to be tested can be completed under this test environment.

[0050] The present invention is a frequency domain testing method, which uses a calibration piece with known transmittance characteristics to calibrate environmental parameters. Cone-shaped absorbing units are laid on both sides of the metal screen assembly and on the ground to absorb environmental electromagnetic waves, eliminate background reflections, and improve accuracy. Convenient and accurate measurement of the transmittance of radar transparent materials can be achieved in the P band.

[0051] The specific steps of the test method of the radar wave-transmitting material transmittance of the P-band of the present invention are as follows:

[0052] In the test method for the wave transmittance of P-band radar wave-transmitting materials, the plane corresponding to the theoretical value of the wave transmittance is defined as plane T, the theoretical values ​​of the wave transmittance of the three calibration pieces are recorded as T1, T2 and T3, and the wave transmittance of the sample to be tested is recorded as T4;

[0053] The plane corresponding to the measured transmittance value is defined as plane V. The scattering parameters S of the three calibration pieces and the sample to be tested are measured by the field test device for the transmittance of radar transparent materials. 21 The measured values ​​are recorded as V1, V2, V3 and V4;

[0054] The wave transmittance T4 of the sample to be tested is calculated using the theoretical wave transmittance values ​​of the three calibration components and the measured data:

[0055]

[0056] in:

[0057]

[0058] Example:

[0059] Reference Figure 1-5As shown, this embodiment proposes a test device for measuring the transmittance of radar-transparent materials in the P-band, including a metal screen assembly 5, a transmitting antenna 1 and a receiving antenna 2 located on both sides of the metal screen assembly 5, and the transmitting and receiving antennas are double-ridged horn antennas working in the P-band. The platform at the position of the central opening 7 of the metal screen 6 is used to place the sample to be tested or the calibration piece. The transmitting and receiving antennas are 2000mm away from the reference plane. The three calibration pieces are a straight-through calibration piece, a polytetrafluoroethylene plate with a size of 450mm×450mm×5mm, and a polytetrafluoroethylene plate with a size of 450mm×450mm×10mm. The sample to be tested is an FR4 board with a size of 450mm×450mm×8mm.

[0060] The theoretical transmittance value T1 of the through calibration component is:

[0061] T1=1 (3)

[0062] The thicknesses of the two polytetrafluoroethylene plates are d1 and d2 respectively, and the theoretical values ​​of their wave transmittance are calculated by the following two formulas:

[0063]

[0064] in: θ t Represents the transmission angle of electromagnetic waves in the material, θ i represents the incident angle of the electromagnetic wave in the material, d1 and d2 represent the thickness of the two polytetrafluoroethylene plates respectively, R represents the reflectivity; k0 represents the propagation constant in free space; γ represents the propagation constant in the material; ε represents the dielectric constant of the material;

[0065]

[0066] Among them, θ t Represents the transmission angle of electromagnetic waves in the material, θ i represents the incident angle of the electromagnetic wave in the material, d1 and d2 represent the thickness of the two polytetrafluoroethylene plates respectively, R represents the reflectivity; k0 represents the propagation constant in free space; γ represents the propagation constant in the material; ε represents the dielectric constant of the material;

[0067] The plane where the metal screen 6 is located is defined as the phase reference plane, and three calibration pieces with known transmittance characteristics are used by replacing the straight-through calibration piece and polytetrafluoroethylene plates with different thicknesses.

[0068] For the traditional method of wave transmittance test, it is only necessary to measure and save the scattering parameters S of the straight-through calibration piece and the sample to be tested. 21 , and dividing the two values ​​can get the wave transmittance of the sample to be tested.

[0069] This embodiment provides a method for measuring the transmittance of a radar-transparent material in the P band, and the specific steps are as follows:

[0070] 1) Calculate the theoretical transmittance values ​​corresponding to the three calibration pieces, denoted as T1, T2 and T3;

[0071] 2) The transmitting antenna 1 and the receiving antenna 2 are located on both sides of the metal screen assembly 5. The transmitting antenna 1 is used to transmit electromagnetic waves, and the receiving antenna 2 is used to receive electromagnetic waves. The plane where the metal screen 6 is located is defined as the reference plane; the three calibration pieces and the sample to be tested are placed on the reference plane respectively, and the scattering parameters S are measured and saved. 21 , denoted as V1, V2,

[0072] V3 and V4;

[0073] 3) Using the scattering parameter S in step 2) 21 The measured values ​​V1, V2, V3 and V4 and the theoretical wave transmittance values ​​T1, T2 and T3 calculated in step 1) can be used to obtain the wave transmittance T4 of the radar wave transparent material to be measured:

[0074]

[0075] in:

[0076]

[0077] Calculate the transmittance T4 using the traditional method:

[0078]

[0079] The comparison results of the amplitude and phase of the wave transmittance of the sample to be tested based on the present invention at vertical incidence and oblique 45° incidence in the P band and the traditional method are shown in Figure 6-9 The test results of the present invention are close to the theoretical values ​​and are superior to those of the traditional methods.

[0080] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for measuring the transmittance of P-band radar transparent materials, characterized in that The specific steps are as follows: Select three calibration pieces; The calibration piece / test sample is placed at the center hole of the metal screen, and an electromagnetic wave transmitting antenna and an electromagnetic wave receiving antenna are arranged at opposite positions on both sides thereof; The transmitting antenna transmits electromagnetic waves, and the receiving antenna receives the electromagnetic waves transmitted by the calibration piece / sample to be tested; Place the three calibration pieces and the sample to be tested in the center hole of the metal screen, measure and save the scattering parameters S of the three calibration pieces and the sample to be tested. 21 , denoted as V1, V2, V3 and V4 respectively; The theoretical wave transmittance values ​​corresponding to the three calibration pieces are calculated and recorded as T1, T2 and T3 respectively; Based on the theoretical values ​​of the wave transmittance of the three calibration pieces and the measured data, the wave transmittance T4 of the sample to be tested is calculated: in, 2. The method for measuring the transmittance of a P-band radar transparent material according to claim 1, characterized in that: The three calibration pieces are respectively a straight-through calibration piece and two polytetrafluoroethylene plates with different thicknesses.

3. The method for measuring the transmittance of a P-band radar transparent material according to claim 2, characterized in that: The sizes of the two PTFE plates with different thicknesses are 450 mm × 450 mm × 5 mm and 450 mm × 450 mm × 10 mm respectively.

4. The method for measuring the transmittance of a P-band radar transparent material according to claim 2, characterized in that: The plane where the metal screen is located is used as a phase reference plane, and the electromagnetic wave transmitting antenna, the electromagnetic wave receiving antenna and the phase reference plane are at equal distances.

5. The method for measuring the transmittance of a P-band radar transparent material according to claim 4, characterized in that: The distance between the electromagnetic wave transmitting antenna, the electromagnetic wave receiving antenna and the phase reference plane is 2000 mm.

6. The method for measuring the transmittance of a P-band radar transparent material according to claim 2, characterized in that: The calculation method of the theoretical value of the wave transmittance corresponding to the calibration piece is: The theoretical transmittance value T1 of the through calibration component is set to 1; The calculation formulas for the theoretical transmittance values ​​T2 and T3 of two PTFE plates with different thicknesses are as follows: in, θ t Represents the transmission angle of electromagnetic waves in the material, θ i represents the incident angle of the electromagnetic wave in the material, d1 and d2 represent the thickness of the two polytetrafluoroethylene plates respectively, R represents the reflectivity; k0 represents the propagation constant in free space; γ represents the propagation constant in the material; ε represents the dielectric constant of the material.

7. The method for measuring the transmittance of a P-band radar transparent material according to claim 6, characterized in that: The calculation formula of the reflectivity is: Here, d represents the thickness.

8. A device for measuring the transmittance of P-band radar transparent materials, characterized in that: A method for measuring the transmittance of a P-band radar-transparent material according to any one of claims 1 to 7; comprising a metal screen assembly and an electromagnetic wave transmitting antenna and a receiving antenna disposed on both sides thereof, wherein the electromagnetic wave emitted by the transmitting antenna passes through a calibration piece / test sample placed on the metal screen assembly and is received by the receiving antenna; The transmitting antenna and the receiving antenna are respectively connected to a vector network analyzer through microwave cables. The vector network analyzer is used to generate a test signal and process a received signal.

9. The device for measuring the transmittance of a P-band radar transparent material according to claim 8, characterized in that: The metal screen assembly comprises a metal screen, a bracket and a base. The metal screen is mounted on the base via the bracket, and the three are fixedly connected in a detachable manner. A plurality of lockable universal rollers are mounted at the bottom of the base plate.

10. The device for measuring the wave transmittance of a P-band radar transparent material according to claim 8, characterized in that: Corner pyramid wave absorbing units are arranged on both sides of the metal screen assembly to absorb environmental electromagnetic waves and eliminate background reflections.

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