Radio frequency signal injection device for complete machine low-level direct drive test and design method thereof

Abstract

The invention relates to the technical field of HIRF airworthiness tests, and discloses a radio frequency signal injection device for a complete machine low-level direct drive test and a design method thereof.The radio frequency signal injection device comprises a fixed support and a connector, the connector comprises an input end inner conductor, an input end outer conductor is arranged on the outer side of the input end inner conductor, and the input end outer conductor is connected with the fixed support; one end of the input end inner conductor and one end of the input end outer conductor are fixedly connected with a conical inner conductor and a conical outer conductor respectively. A coaxial input signal is converted into a high-power radio-frequency current injection conversion device which is easily connected with a low-level direct drive test grounding loop and a test piece current injection point, can bear passing radio-frequency power of 2000 watts, and keeps 50-ohm coaxial impedance structure matching from an input end to an injection end. High-power uniform injection connection and test of a tested piece in a low-level direct drive test can be realized.

Description

Technical Field

[0001] The invention relates to the field of HIRF airworthiness test, and more specifically, to a radio frequency signal injection device for low-level direct drive test of a whole machine and a design method thereof. Background Art

[0002] High-intensity radiated field (HIRF) refers to the electromagnetic environment generated by radiation from ship radar, airport surveillance radar, AM and FM radio stations, VHF television transmitters, mobile communication base stations, etc. that civil aircraft may encounter under current flight guidelines. It affects the safety of aircraft. HIRF protection test verification is a rigid requirement for the airworthiness of civil aircraft.

[0003] There are two main types of HIRF airworthiness test methods for complete aircraft: high-level and low-level. Since high-level test methods are difficult to implement, low-level airworthiness test verification methods are mostly used. Complete aircraft HIRF low-level tests are divided into low-level direct drive tests (LLDD), low-level scanning current tests (LLSC), and low-level scanning field tests (LLSF). Due to many problems such as the large size of low-frequency antennas that are difficult to set up, difficulty in polarization mode conversion, and low low-frequency radiation efficiency, the low-frequency band mostly uses the radiation equivalent injection test method - low-level direct drive test method.

[0004] The low-level direct drive (LLDD) test method mainly includes two forms: the single-side loop method and the coaxial loop method. The coaxial loop method regards the DUT as a coaxial inner conductor, and the multiple return conductors placed outside the DUT as coaxial outer conductors, with air as the medium between the two to form a coaxial structure. In the LLDD test, the high-power RF current needs to be injected into the DUT skin through the injection belt connection, and the other end of the DUT is connected to the return conductor to form a current loop. The efficient injection technology of broadband high-power RF signals is one of the key technologies of the LLDD test.

[0005] Most of the existing patents for RF converters are related to the conversion between different transmission structures, and there is no low standing wave, high-power RF injection device that can be used for low-level direct drive test of the whole machine. In the existing whole machine low-level direct drive (LLDD) test, the RF high-power current injection efficiency is low due to poor port standing wave ratio and large power reflection, and the high-frequency link impedance mismatch is serious, which limits the test frequency band. Summary of the invention

[0006] The present invention provides a radio frequency signal injection device for a low-level direct drive test of a whole machine and a design method thereof, which solves the problems of low radio frequency high-power current injection efficiency due to large power reflection caused by poor port standing wave ratio, and limited test frequency band caused by serious impedance mismatch of high-frequency link in the existing low-level direct drive test of the whole machine.

[0007] The invention provides a radio frequency signal injection device for a low-level direct drive test of a whole machine, comprising a fixing bracket and a connector, wherein the connector comprises an input end inner conductor, an input end outer conductor is arranged outside the input end inner conductor, one end of the input end inner conductor and the input end outer conductor are respectively fixedly connected with a cone inner conductor and a cone outer conductor, one end of the cone inner conductor and the cone outer conductor away from the connector are respectively fixedly connected with an output end inner conductor and an output end outer conductor, the cone outer conductor and the output end outer conductor are respectively located outside the cone inner conductor and the output end inner conductor, the input end inner conductor, the cone inner conductor and the output end inner conductor constitute an internal link, the input end outer conductor, the cone outer conductor and the output end outer conductor constitute a return link, and the internal link and the return link constitute a coaxial impedance matching structure.

[0008] In a preferred embodiment, a circle of through holes 1 are equidistantly provided on the surface of the inner conductor at the output end, and a circle of through holes 2 are equidistantly provided on the surface of the outer conductor at the output end. Through hole 1 is used to connect to the injection point of the test object, and through hole 2 is used to connect to the test ground loop network.

[0009] In a preferred embodiment, the connector is an L29 connector, the input end outer conductor has a mounting flange, and the four corner mounting holes can be fixed to the conical outer conductor by screws. The input end inner conductor and the conical inner conductor are screwed together.

[0010] In a preferred embodiment, the conical inner conductor adopts a conical structure, and the middle cone and the outer conductor form a 50 ohm coaxial impedance match to reduce the large reflection caused by the step capacitance caused by the sudden change of the inner conductor cross section. The conical inner conductor adopts a hollow structure and is made of metal materials such as copper and aluminum; the output end inner conductor is made of metal materials such as copper and aluminum, and is integrally formed or welded with the conical inner conductor.

[0011] In a preferred embodiment, the conical outer conductor is connected to the input end outer conductor, made of metal materials such as copper and aluminum, and treated with conductive anti-oxidation processes. The output end outer conductor is made of metal materials such as copper and aluminum, and is integrally formed or welded with the conical outer conductor.

[0012] In a preferred embodiment, the insulating medium serves to space and fix the conical inner conductor and the conical outer conductor, is hollowed out while retaining strength, and is fixed with high-strength plastic screws (non-metallic); the fixing bracket is made of metal materials such as copper or aluminum, and is welded to the conical outer conductor at least at two locations on both sides of the center of gravity; the base is made of high-strength plastic material to serve as an isolation.

[0013] The present invention also provides a design method for a radio frequency signal injection device for a low-level direct drive test of a whole machine, comprising the following steps:

[0014] S1: Determination of the diameter size of the cone inner conductor and cone outer conductor: In order to minimize the large reflection caused by the step capacitance caused by the sudden change in the cross section of the cone inner conductor, the inner diameter of the cone outer conductor input end must be consistent with the inner diameter of the input end outer conductor. The coaxial impedance calculation formula is:

[0015]

[0016] In the formula, , is the inner diameter of the conical outer conductor, is the outer diameter of the inner conductor of the cone, is the dielectric constant of the medium, then the inner diameter of the outer conductor of the 50 ohm coaxial cone is The outer diameter of the inner conductor of the cone The ratio is:

[0017]

[0018] The outer diameter of the input end of the cone inner conductor can be obtained from the coaxial impedance calculation formula;

[0019] S2: Further determine the dimensions of the input inner conductor and the input outer conductor injection end to ensure that the converter cutoff frequency is greater than 200MHz, using the theoretical calculation formula for the coaxial connector cutoff frequency:

[0020]

[0021] In the formula, is the speed of light;

[0022] S3: Substitute the inner diameter of the conical outer conductor and the outer diameter of the conical inner conductor into the theoretical calculation formula of the coaxial connector cutoff frequency to calculate the coaxial connector cutoff frequency , meeting the requirement of greater than 200MHz.

[0023] S4: Determine the transition cone length from the input end to the injection end of the conical outer conductor, and optimize it through the RF simulation software HFSS / CST to meet the input and output requirements.

[0024] The beneficial effects of the present invention are:

[0025] The present invention converts a coaxial input signal into a high-power RF current injection conversion device which is easily connected to a low-level direct drive test ground loop and a test piece current injection point. The device can withstand 2000 watts of RF power and maintain 50 ohm coaxial impedance structure matching from the input end to the injection end, thereby realizing high-power uniform injection connection and testing of the test piece in a low-level direct drive test.

[0026] The present invention can reduce link mismatch, increase test data accuracy and equipment utilization efficiency under the same conditions by adopting appropriate impedance matching design, so that low-level direct drive tests can be performed at higher frequency bands, solving the existing problems of low high-power injection efficiency and incompatibility with high-frequency extension. At the same time, it also avoids the problem of excessive standing wave ratio of the injection port due to impedance mismatch, resulting in excessive reflected power, thereby affecting the stability of amplifier performance or even damaging it. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the design method of the present invention.

[0028] Figure 2 It is a schematic diagram of the overall structure of the present invention.

[0029] Figure 3 The present invention Figure 1 sectional view of .

[0030] Figure 4 It is a standing wave ratio curve diagram of the radio frequency signal injection device of the present invention.

[0031] In the figure: 1. fixing bracket; 2. connector; 21. inner conductor of input end; 22. outer conductor of input end; 3. inner conductor of cone; 31. inner conductor of output end; 32. through hole 1; 4. outer conductor of cone; 41. outer conductor of output end; 42. through hole 2; 5. insulating medium. DETAILED DESCRIPTION

[0032] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and the functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the contents of this specification. Each example may omit, replace or add various processes or components as needed. In addition, the features described relative to some examples may also be combined in other examples.

[0033] like Figure 2-Figure 3As shown, a radio frequency signal injection device for low-level direct drive test of the whole machine includes a fixing bracket 1 and a connector 2, the connector 2 includes an input end inner conductor 21, an input end outer conductor 22 is arranged outside the input end inner conductor 21, one end of the input end inner conductor 21 and the input end outer conductor 22 are respectively fixedly connected with a conical inner conductor 3 and a conical outer conductor 4, an insulating medium 5 is installed between the conical inner conductor 3 and the conical outer conductor 4, and the ends of the conical inner conductor 3 and the conical outer conductor 4 away from the connector 2 are respectively fixedly connected with an output end inner conductor 31 and the output end outer conductor 41, the cone outer conductor 4 and the output end outer conductor 41 are respectively located on the outside of the cone inner conductor 3 and the output end inner conductor 31, the input end inner conductor 21, the cone inner conductor 3 and the output end inner conductor 31 constitute an internal link, the input end outer conductor 22, the cone outer conductor 4 and the output end outer conductor 41 constitute a return link, the internal link and the return link constitute a 50 ohm coaxial impedance matching structure, during detection, the internal link and the return link are respectively connected to the two ends of the device under test through cables. In this embodiment, the device under test is an aircraft body.

[0034] Furthermore, a circle of through holes 32 are equidistantly provided on the surface of the inner conductor 31 at the output end, and a circle of through holes 42 are equidistantly provided on the surface of the outer conductor 41 at the output end. The through holes 32 are used to connect to the injection point of the test object, and the through holes 42 are used to connect to the test ground loop network.

[0035] In the above technical solution, the connector 2 adopts the L29 type K head (external thread) form, and can also be N type, BNC type, etc.

[0036] In the above technical solution, for the conical inner conductor 3, in order to minimize the large reflection caused by the step capacitance caused by the sudden change of the cross section of the conical inner conductor 3, the conical inner conductor 3 adopts a conical structure to achieve the purpose of expanding the injection end. According to the skin effect of radio frequency signal transmission, the conical inner conductor 3 adopts a hollow structure, and metal materials such as copper and aluminum are selected, and the conductive and anti-oxidation processes are processed to reduce weight and save costs.

[0037] In the above technical solution, the output end inner conductor 31 is integrally formed with the conical inner conductor 3 or connected by welding, and is made of metal materials such as copper and aluminum. A through hole 32 is designed at the injection end of the output end inner conductor 31, and a circle of through holes 32 are arranged at equal intervals along the edge. The more through holes 32 there are, the closer the impedance matching is to the standard value, and the more uniform the skin current distribution is.

[0038] In the above technical solution, for the conical outer conductor 4, a conical structure is adopted to maintain consistent impedance with the conical inner conductor 3. The conical outer conductor 4 is connected to the output end outer conductor 41. Metal materials such as copper and aluminum are selected, and conductive and anti-oxidation processes are adopted to increase the service life.

[0039] In the above technical solution, for the output end outer conductor 41, a metal material such as copper or aluminum is selected, which is integrally formed or welded with the conical outer conductor 4. A through hole 42 is designed at the injection end of the output end outer conductor 41, and a circle of through holes 42 are evenly spaced along the edge to facilitate the return cable connection and make the electric field evenly distributed around the periphery of the measured device.

[0040] In the above technical solution, an insulating medium 5 is also provided, and the insulating medium 5 is provided at least in two places for isolating and fixing the conical inner conductor 3 and the conical outer conductor 4. The insulating medium 5 is hollowed out while retaining sufficient strength, and is fixed to the conical inner conductor 3 and the conical outer conductor 4 with high-strength non-metallic plastic screws to reduce its own weight.

[0041] In the above technical solution, the fixing bracket 1 is made of metal materials such as copper or aluminum, and is welded to the conical outer conductor 4 at least at two locations on both sides of the gravity center. The base of the fixing bracket 1 is made of high-strength plastic material to play an isolation role. Handles are provided on both sides for easy transportation.

[0042] The above technical solution is to convert the coaxial input signal into a high-power RF current injection conversion device that is easily connected to the low-level direct drive test ground loop and the test piece current injection point. It can withstand 2000 watts of RF power and maintain 50 ohm coaxial impedance structure matching from the input end to the injection end, which can realize high-power uniform injection connection and testing of the test piece in the low-level direct drive test.

[0043] like Figure 1 As shown, this embodiment also provides a design method for a radio frequency signal injection device for a low-level direct drive test of a whole machine, comprising the following steps:

[0044] S1: Determination of the diameter size of the conical inner conductor 3 and the conical outer conductor 4: In order to minimize the large reflection caused by the step capacitance due to the sudden change in the cross section of the conical inner conductor 3, the inner diameter of the input end of the conical outer conductor 4 must be consistent with the inner diameter of the input end outer conductor 22. The coaxial impedance calculation formula is:

[0045]

[0046] In the formula, , is the inner diameter of the conical outer conductor 4, is the outer diameter of the conical inner conductor 3, is the dielectric constant of the medium, then the inner diameter of the 50 ohm coaxial conical outer conductor 4 The outer diameter of the conical inner conductor 3 The ratio is:

[0047]

[0048] The outer diameter of the input end of the conical inner conductor 3 can be obtained from the coaxial impedance calculation formula;

[0049] S2: Further determine the dimensions of the input inner conductor 21 and the input outer conductor 22 injection end to ensure that the converter cutoff frequency is greater than 200MHz, using the theoretical calculation formula of the coaxial connector cutoff frequency:

[0050]

[0051] In the formula, is the speed of light;

[0052] S3: Substitute the inner diameter of the conical outer conductor 4 and the outer diameter of the conical inner conductor 3 into the theoretical calculation formula of the coaxial connector cutoff frequency to calculate the coaxial connector cutoff frequency , meeting the requirement of greater than 200MHz.

[0053] S4: Determine the transition cone length from the input end to the injection end of the conical outer conductor 4, and optimize it through the RF simulation software HFSS / CST to meet the input and output requirements, such as Figure 4 shown.

[0054] By adopting appropriate impedance matching design, link mismatch can be reduced, and the accuracy of test data and equipment utilization efficiency under the same circumstances can be increased, so that low-level direct drive tests can be carried out in higher frequency bands, solving the existing problems of low high-power injection efficiency and incompatibility with high-frequency extension. At the same time, it also avoids the problem of excessive standing wave ratio of the injection port due to impedance mismatch, resulting in excessive reflected power, which affects the stability of amplifier performance or even damages it.

[0055] The above describes an embodiment of the present embodiment, but the present embodiment is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present embodiment, ordinary technicians in this field can also make many forms, all of which are within the protection of the present embodiment.

Claims

1. A radio frequency signal injection device for low-level direct drive test of a whole machine, characterized in that: The invention comprises a fixing bracket (1) and a connector (2), wherein the connector (2) comprises an input end inner conductor (21), an input end outer conductor (22) is arranged outside the input end inner conductor (21), one end of the input end inner conductor (21) and the input end outer conductor (22) are respectively fixedly connected to a conical inner conductor (3) and a conical outer conductor (4), one end of the conical inner conductor (3) and the conical outer conductor (4) away from the connector (2) are respectively fixedly connected to an output end inner conductor (31) and an output end outer conductor (41), the conical outer conductor (4) and the output end outer conductor (41) are respectively located outside the conical inner conductor (3) and the output end inner conductor (31), the input end inner conductor (21), the conical inner conductor (3) and the output end inner conductor (31) constitute an internal link, the input end outer conductor (22), the conical outer conductor (4) and the output end outer conductor (41) constitute a return link, and the internal link and the return link constitute a coaxial impedance matching structure.

2. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The surface of the inner conductor (31) at the output end is provided with a circle of first through holes (32) at equal intervals, and the surface of the outer conductor (41) at the output end is provided with a circle of second through holes (42) at equal intervals. The first through hole (32) is used to connect to the injection point of the test object, and the second through hole (42) is used to connect to the test ground loop network.

3. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The conical inner conductor (3) adopts a conical hollow structure, is made of copper or aluminum, and is treated using a conductive anti-oxidation process.

4. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The output end inner conductor (31) is integrally formed with the conical inner conductor (3) or is connected by welding, and the material of the output end inner conductor (31) is copper or aluminum.

5. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The conical outer conductor (4) and the conical inner conductor (3) maintain consistent impedance, and the conical outer conductor (4) is a conical structure.

6. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The conical outer conductor (4) is connected to the output end outer conductor (41), and is made of copper or aluminum and is processed by conductive and anti-oxidation processes.

7. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The output end outer conductor (41) is made of copper or aluminum and is integrally formed or welded with the conical outer conductor (4).

8. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The radio frequency signal injection device also includes an insulating medium (5), wherein the insulating medium (5) is provided at least at two locations and is used to isolate and fix the conical inner conductor (3) and the conical outer conductor (4), and the insulating medium (5) is hollowed out and fixed to the conical inner conductor (3) and the conical outer conductor (4) using high-strength non-metallic plastic screws.

9. The RF signal injection device for low-level direct drive test of a whole machine according to claim 1, characterized in that: The fixing bracket (1) is made of copper or aluminum and is welded to the conical outer conductor (4) at at least two locations on both sides of the gravity center. The base of the fixing bracket (1) is made of high-strength plastic material.

10. A design method for a radio frequency signal injection device for a low-level direct drive test of a whole machine according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Determination of the diameter size of the conical inner conductor (3) and the conical outer conductor (4): In order to minimize the large reflection caused by the step capacitance due to the sudden change in the cross section of the conical inner conductor (3), the inner diameter of the input end of the conical outer conductor (4) must be consistent with the inner diameter of the input end outer conductor (22). The coaxial impedance calculation formula is: ； In the formula, , is the inner diameter of the conical outer conductor (4), is the outer diameter of the conical inner conductor (3), is the dielectric constant of the medium, then the inner diameter of the 50 ohm coaxial conical outer conductor (4) The outer diameter of the conical inner conductor (3) The ratio is: ； The outer diameter of the input end of the conical inner conductor (3) can be obtained from the coaxial impedance calculation formula; S2: Further determine the dimensions of the input end inner conductor (21) and the input end outer conductor (22) injection end to ensure that the converter cutoff frequency is greater than 200 MHz, using the theoretical calculation formula of the coaxial connector cutoff frequency: ； In the formula, is the speed of light; S3: Substitute the inner diameter of the conical outer conductor (4) and the outer diameter of the conical inner conductor (3) into the theoretical calculation formula for the cutoff frequency of the coaxial connector to calculate the cutoff frequency of the coaxial connector. , meet the requirement of greater than 200MHz; S4: Determine the transition cone length from the input end to the injection end of the conical outer conductor (4), and optimize it through the RF simulation software HFSS / CST to meet the input and output requirements.

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