A method and device for measuring uniformity of microwave resonant cavity field

Abstract

The present invention discloses a method and device for measuring the uniformity of a microwave resonant cavity field. According to the non-resonant perturbation theory, the electromagnetic field at the corresponding position in space will change before and after the perturbation, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 , and S 11 This is another quantity that can be detected by a vector network analyzer. Therefore, we can use a vector network analyzer to measure the S of the electromagnetic field before and after the perturbation. 11 value to determine how much the electromagnetic field has changed, and then derive ΔS 11 Value, according to ΔS 11 The consistency of the test results is used to judge the processing accuracy of the device under test.

Description

Technical Field

[0001] The present invention relates to the application field of klystron technology, and in particular to a method and device for measuring the uniformity of a microwave resonant cavity field. Background Art

[0002] A klystron is an electro-vacuum device that generates microwave power. It primarily consists of an electron cavity, an input cavity, a clustering cavity, an output cavity, and a collector. The input and clustering cavities operate in the microwave band, interacting with electrons at high frequencies to accelerate and cluster the electron beam.

[0003] Machining and tuning the input and cluster cavities are crucial processes for ensuring a klystron operates at rated power, especially for C- and X-band multi-beam klystron cavities. The nose cone should be uniform after fine machining. However, due to machining errors, the traditional method of measuring fine-machined dimensions with a ruler is difficult due to the inherent influence of the nose cone structure.

[0004] Therefore, there is an urgent need to provide a method and device for measuring the uniformity of the microwave resonant cavity field. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method and device for measuring the uniformity of the microwave resonant cavity field. According to the non-resonant perturbation theory, the electromagnetic field at the corresponding position in space will change before and after the perturbation, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 , and S 11 This is another quantity that can be detected by a vector network analyzer. Therefore, we can use a vector network analyzer to measure the S of the electromagnetic field before and after the perturbation. 11 value to determine how much the electromagnetic field has changed, and then derive ΔS 11 Value, according to ΔS 11 The consistency of the test results is used to judge the processing accuracy of the device under test.

[0006] The technical solution of the present invention is: a method for measuring the uniformity of a microwave resonant cavity field, comprising the following steps:

[0007] Step 1: Select a suitable perturbator according to the size of the device under test, wherein the device under test is composed of multiple beam channels, and the beam channels are composed of a nose cone hole, a nose cone gap, and a drift tube;

[0008] Step 2: Start the vector network analyzer and perform microwave calibration. Connect the vector network analyzer to the probe via a test cable, and place the probe into the nose cone of the device under test using a probe fixture.

[0009] Step 3: Use a vector network analyzer to read the parameter S of the device under test at the operating frequency when no perturbation body is placed.11,u ;

[0010] Step 4: Place the perturbation body and the perturbation body tooling into the nose cone gap of the device under test, and use a vector network analyzer to read the parameter S of the device under test at the operating frequency when the perturbation body is placed. 11,p ;

[0011] Step 5: Before and after the perturbation, the electromagnetic field at the corresponding position in the space will change, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 value;

[0012] By comparing the ΔS of the electromagnetic field before and after perturbation in step 3 and step 4 11 Value, to judge the change of electromagnetic field;

[0013] Step 6: When multiple ΔS 11 When the consistency of ΔS is greater than 95%, the device under test is judged to meet the requirements; when one of the ΔS 11 When the consistency is less than 95%, it is determined that the processing of the device under test does not meet the requirements.

[0014] Furthermore, in step 1, the perturbation body is made of metal material.

[0015] Furthermore, in step 2, the probe fixture is made of polytetrafluoroethylene material to fix the probe in the cavity of the nose cone hole.

[0016] Furthermore, the probe and the nose cone hole maintain the same axial direction.

[0017] Furthermore, in step 5, the relationship between the change of the electromagnetic field of the device under test before and after being perturbed is as follows:

[0018] ΔS 11 =S 11,p (ω)-S 11,u (ω)=-jω[k e E 2 -k m H 2 ] / P in

[0019] S 11,p 、S 11,u are the reflection coefficients before and after perturbation, respectively;

[0020] ΔS 11 is the difference in electromagnetic field reflection coefficient before and after perturbation;

[0021] P in is the average microwave power entering the resonant cavity;

[0022] k e 、k mare the shape factors associated with the perturbator;

[0023] ω is the angular frequency;

[0024] E and H represent the change in electric field and magnetic field at that point, respectively.

[0025] Furthermore, when the perturbation body is a cylindrical structure, ΔS 11 Mainly determined by the electric field component. When the measured electric field is higher than the design value, the nose cone gap is reserved shorter, and when the measured electric field is lower than the design value, the nose cone gap is reserved longer; or

[0026] When the perturbation body is a circular ring structure, ΔS 11 Mainly determined by the magnetic field component. When the measured magnetic field is lower than the design value, the nose cone gap is reserved shorter, and when the measured magnetic field is higher than the design value, the nose cone gap is reserved longer.

[0027] Furthermore, in step 6, the consistency is multiple ΔS 11 Respectively at multiple ΔS 11 compared with the average value.

[0028] A microwave resonant cavity field uniformity testing device includes a vector network tester, a test connection line, a probe and a probe tool, a device to be tested, and a perturbation body and a perturbation body tool;

[0029] The probe is assembled in the nose cone hole of the device under test through a probe fixture;

[0030] The perturbation body is assembled in the nose cone gap of the device under test through a perturbation body fixture;

[0031] The vector network tester is connected to the probe via the test connection line.

[0032] Furthermore, the perturbation body is a metal material with a cylindrical, ring or cage-like structure.

[0033] Furthermore, the probe fixture and the perturbation body fixture are respectively coaxially arranged with the drift tube.

[0034] The beneficial technical effects of the present invention are:

[0035] A resonant cavity of a multi-injection klystron usually operates in the fundamental mode TM01, and the resonant cavity is composed of multiple beam channels, namely, the nose cone hole, the nose cone gap and the drift tube.

[0036] Ideally, if the processing of these beam channels is exactly the same, the electromagnetic field distribution formed by the resonant cavity will also be exactly the same on these beam channels. The changes in the electromagnetic field that can be made by placing the same perturbation body at the corresponding nose cone gap position of each beam channel should also be consistent, that is, the S11 The changing values ​​of the parameters should also be consistent.

[0037] On the contrary, if one beam channel is processed inconsistently with other beam channels, the change in the field caused by placing the perturbation body at the corresponding nose cone gap position in the beam channel will be different from the change caused by placing it in other beam channels.

[0038] This difference can be seen through S 11 The difference in the parameter change value is reflected. Therefore, the reflection coefficient S before and after the perturbation body is placed can be measured. 11 The consistency of the electromagnetic field in the resonant cavity of the multi-beam klystron is evaluated by comparing the changes in the electromagnetic field of the multi-beam klystron cavity.

[0039] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0041] Figure 2 It is a schematic structural diagram of the probe and the probe tooling, the perturbation body and the perturbation body tooling of the present invention being assembled on a device under test;

[0042] Figure 3 This is the actual test data diagram of Example 1 of the present invention:

[0043] Figure a shows the reflection coefficient at the 1942.43 MHz frequency point before interference.

[0044] Figure b is the reflection coefficient at the same frequency point of drift tube No. 1 after interference; Figure c is the reflection coefficient at the same frequency point of drift tube No. 2 after interference; Figure d is the reflection coefficient at the same frequency point of drift tube No. 3 after interference; Figure e is the reflection coefficient at the same frequency point of drift tube No. 4 after interference; Figure f is the reflection coefficient at the same frequency point of drift tube No. 5 after interference; Figure g is the reflection coefficient at the same frequency point of drift tube No. 6 after interference;

[0045] Figure 4 This is the actual test data diagram of Example 2 of the present invention:

[0046] Among them, Figure a is the reflection coefficient at the frequency point of 1942.43MHz before interference; Figure b is the reflection coefficient at the same frequency point of drift tube No. 1 after interference; Figure c is the reflection coefficient at the same frequency point of drift tube No. 2 after interference; Figure d is the reflection coefficient at the same frequency point of drift tube No. 3 after interference; Figure e is the reflection coefficient at the same frequency point of drift tube No. 4 after interference; Figure f is the reflection coefficient at the same frequency point of drift tube No. 5 after interference; Figure g is the reflection coefficient at the same frequency point of drift tube No. 6 after interference;

[0047] The accompanying drawings are:

[0048] 1. Vector analyzer; 2. Test connection line; 3. Probe and probe tooling; 31. Probe tooling; 32. Probe; 4. Device under test; 5. Perturbator and perturbator tooling; 51. Perturbator tooling; 52. Perturbator. DETAILED DESCRIPTION

[0049] In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0050] It should be noted that the terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, for the purposes of describing the embodiments of the present application herein.

[0051] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship described in the embodiments and shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0052] like Figure 1 and Figure 2 As shown, the present invention specifically relates to a method for measuring the uniformity of a microwave resonant cavity field, comprising the following steps:

[0053] Step 1: Select a suitable perturbator according to the size of the device under test, wherein the device under test is composed of multiple beam channels, and the beam channels are composed of a nose cone hole, a nose cone gap, and a drift tube;

[0054] In step 1, the perturbation body is made of metal material.

[0055] Step 2: Start the vector network analyzer and perform microwave calibration. Connect the vector network analyzer to the probe via a test cable, and place the probe into the nose cone of the device under test using a probe fixture.

[0056] In step 2, the probe fixture is made of polytetrafluoroethylene material to fix the probe in the cavity of the nose cone hole.

[0057] The probe and the nose cone hole maintain the same axial direction.

[0058] Step 3: Use a vector network analyzer to read the parameter S of the device under test at the operating frequency when no perturbation body is placed. 11,u ;

[0059] Step 4: Place the perturbation body and the perturbation body tooling into the nose cone gap of the device under test, and use a vector network analyzer to read the parameter S of the device under test at the operating frequency when the perturbation body is placed. 11,p ;

[0060] Step 5: Before and after the perturbation, the electromagnetic field at the corresponding position in space will change, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 value;

[0061] By comparing the ΔS of the electromagnetic field before and after perturbation in step 3 and step 4 11 Value, to judge the change of electromagnetic field;

[0062] Based on the theory of non-resonant perturbation, this application proposes a method for measuring the electromagnetic field consistency of a multi-beam klystron tube. Perturbation refers to the use of small metal objects to fill the originally empty space, and the distribution of the electromagnetic field will be changed due to the presence of the metal objects.

[0063] According to the non-resonant perturbation theory, the electromagnetic field at the corresponding position in space will change before and after the perturbation, and this change will be reflected in the reflection coefficient of the electromagnetic field, that is, S 11 Come up, and S 11 This is another quantity that can be detected by a vector network analyzer. Therefore, we can use a vector network analyzer to measure the S of the electromagnetic field before and after the perturbation. 11 The non-resonant perturbation theory gives the change of the electromagnetic field at any point in space before and after the perturbation and its S 11 The relationship between parameter changes is as follows:

[0064] ΔS 11 =S 11,p (ω)-S 11,u (ω)=-jω[k e E 2 -k m H2 ] / P in

[0065] S 11,p 、S 11,u are the reflection coefficients before and after perturbation, respectively;

[0066] ΔS 11 is the difference in electromagnetic field reflection coefficient before and after perturbation;

[0067] P in is the average microwave power entering the resonant cavity;

[0068] k e 、k m are the shape factors associated with the perturbator;

[0069] ω is the angular frequency;

[0070] E and H represent the change in electric field and magnetic field at that point, respectively.

[0071] A resonant cavity of a multi-injection klystron usually operates in the fundamental mode TM01, and the resonant cavity is composed of multiple beam channels, namely, the nose cone hole, the nose cone gap and the drift tube.

[0072] Ideally, if the processing of these beam channels is exactly the same, the electromagnetic field distribution formed by the resonant cavity will also be exactly the same on these beam channels. The changes in the electromagnetic field that can be made by placing the same perturbation body at the corresponding nose cone gap position of each beam channel should also be consistent, that is, the S 11 The changing values ​​of the parameters should also be consistent.

[0073] On the contrary, if one beam channel is processed inconsistently with other beam channels, the change in the field caused by placing the perturbation body at the corresponding nose cone gap position in the beam channel will be different from the change caused by placing it in other beam channels.

[0074] This difference can be seen through S 11 The difference in the parameter change value is reflected. Therefore, the reflection coefficient S before and after the perturbation body is placed can be measured. 11 The consistency of the electromagnetic field in the resonant cavity of the multi-beam klystron is evaluated by comparing the changes in the electromagnetic field of the multi-beam klystron cavity.

[0075] Furthermore, when the perturbation body is a cylindrical structure, ΔS 11 Mainly determined by the electric field component. When the measured electric field is higher than the design value, the nose cone gap is reserved shorter, and when the measured electric field is lower than the design value, the nose cone gap is reserved longer; or

[0076] When the perturbation body is a circular ring structure, ΔS 11Mainly determined by the magnetic field component. When the measured magnetic field is lower than the design value, the nose cone gap is reserved shorter, and when the measured magnetic field is higher than the design value, the nose cone gap is reserved longer.

[0077] Step 6: When multiple ΔS 11 When the consistency of ΔS is greater than 95%, the device under test is judged to meet the requirements; when one of the ΔS 11 When the consistency is less than 95%, it is determined that the processing of the device under test does not meet the requirements.

[0078] In step 6, the consistency is multiple ΔS 11 Respectively at multiple ΔS 11 compared with the average value.

[0079] Example 1:

[0080] The microwave cavity field uniformity test method described above was used for measurements. The resonant cavity under test was the third harmonic resonant cavity of a 650 MHz multi-beam klystron tube, and the theoretical design value of its electromagnetic field frequency was 1942.43 MHz. The test system used a KEYSIGHT E5071C vector network analyzer. According to the test method, the vector network analyzer was connected to the probe via a test cable. The probe was then inserted into the probe fixture to form a probe and fixture assembly. The probe and fixture assembly was then inserted into either nose cone hole on one side of the test cavity.

[0081] The sweep frequency range of the vector network analyzer is set to 1932MHz-1952MHz, and the number of measurement points (scanning points) is 1601. In the S11 measurement mode of the vector network analyzer, the electromagnetic field resonance frequency of the cavity is obtained to be 1942.43MHz, and the value of the electromagnetic field reflection coefficient before perturbation S is obtained at this frequency point. 11,u is -0.6847dB, such as Figure 3 As shown in Figure a".

[0082] Then the perturbation body is installed in the perturbation body fixture, and the perturbation body and fixture components are inserted into the 6 nose cone gaps on the other side of the measurement resonant cavity in turn, and the electromagnetic field reflection coefficient S after perturbation at the frequency point of 1942.43MHz is obtained respectively. 11,μ,1 =-0.6515dB, S 11,μ,2 =-0.6534dB, S 11,μ,3 =-0.6513dB, S 11,μ,4 =-0.6534dB, S 11,μ,5 =-0.6535dB, S 11,μ,6 =-0.6524dB. The measurement results are as follows Figure 3 As shown in Figures b to g.

[0083] Then calculate the ΔS of each re-entrant structure according to the formula 11 value, and obtain ΔS 11，1 =-0.0332dB, ΔS 11，2 =-0.0313dB, ΔS 11，3 =-0.0334dB, ΔS 11，4 =-0.0312dBΔS 11，5 =-0.0313dB,ΔS 11，6 =-0.0323dB. Their consistency is 96.57%, 97.51%, 95.95%, 97.20%, 97.51%, 99.38%, all better than 95%. The results show that the machining and welding accuracy of the third harmonic resonant cavity of the multi-beam klystron meets the design requirements.

[0084] Example 2:

[0085] The microwave cavity field uniformity test method described above was used for measurements. The resonant cavity under test was the third harmonic resonant cavity of a 650 MHz multi-beam klystron tube, and the theoretical design value of its electromagnetic field frequency was 1942.43 MHz. The test system used a KEYSIGHT E5071C vector network analyzer. According to the test method, the vector network analyzer was connected to the probe via a test cable. The probe was then inserted into the probe fixture to form a probe and fixture assembly. The probe and fixture assembly was then inserted into either nose cone hole on one side of the test cavity.

[0086] The sweep frequency range of the vector network analyzer is set to 1932MHz-1952MHz, and the number of measurement points (scan points) is 1601. In the S11 measurement mode of the vector network analyzer, the electromagnetic field resonance frequency of the cavity is obtained to be 1942.43MHz, and the electromagnetic field reflection coefficient S before perturbation is obtained at this frequency point. 11,u The value of is -0.6979dB, such as Figure 4 As shown in Figure a.

[0087] Then the perturbation body is installed in the perturbation body fixture, and the perturbation body and fixture components are inserted into the 6 nose cone gaps on the other side of the measurement resonant cavity in turn, and the electromagnetic field reflection coefficient S after perturbation at the frequency point of 1942.43MHz is obtained respectively. 11,μ,1 =-0.6792dB, S 11,μ,2 =-0.6468dB, S 11,μ,3 =-0.6762dB, S 11,μ,4 =-0.6677dB, S 11,μ,5 =-0.6424dB, S 11,μ,6 =-0.6474dB. The measurement results are as follows Figure 4 As shown in Figures b to g.

[0088] Then calculate the ΔS of each re-entrant structure according to the formula 11 value, and obtain ΔS 11，1 =-0.0187dB, ΔS 11，2 =-0.0511dB, ΔS 11，3 =-0.0217dB, ΔS 11，4 =-0.0302dBΔS 11，5 =-0.0555dB,ΔS 11，6 =-0.0505dB. Their consistency is 49.34%, 65.17%, 57.26%, 79.68%, 53.56%, 66.75%, all worse than 95%. The results show that the machining and welding accuracy of the third harmonic resonant cavity of the multi-beam klystron does not meet the design requirements.

[0089] A microwave resonant cavity field uniformity testing device includes a vector network tester, a test connection line, a probe and a probe tool, a device to be tested, and a perturbation body and a perturbation body tool;

[0090] The probe is assembled in the nose cone hole of the device under test through a probe fixture. The probe fixture is made of polytetrafluoroethylene and has a convex structure, which plays the role of fixing the probe and positioning it in the nose cone cavity.

[0091] The perturbation body is assembled in the nose cone gap of the device under test through the perturbation body fixture. The perturbation body fixture is made of polytetrafluoroethylene material and has a convex structure, which plays the role of fixing the perturbation body and positioning it in the nose cone cavity.

[0092] The vector network tester is connected to the probe via the test connection line.

[0093] The device can test multi-injection klystrons of various structural types, such as high-power and high-efficiency klystrons.

[0094] Furthermore, the perturbation body is a metal material with a cylindrical, ring or cage-like structure.

[0095] Furthermore, the probe fixture and the perturbation body fixture are respectively coaxially arranged with the drift tube to ensure measurement accuracy.

[0096] The above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solutions recorded in the above embodiments within the technical scope disclosed by the present invention, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A method for measuring the uniformity of a microwave resonant cavity field, characterized in that: The following steps are involved: Step 1: Select a suitable perturbator according to the size of the resonant cavity to be measured, where the resonant cavity to be measured is composed of multiple beam channels, and the beam channels are composed of a nose cone hole, a nose cone gap, and a drift tube; Step 2: Start the vector network analyzer and perform microwave calibration. Connect the vector network analyzer to the probe via a test cable, and place the probe into the nose cone of the resonant cavity to be measured using a probe fixture. Step 3: Use a vector network analyzer to read the reflection coefficient before perturbation at the working frequency of the resonant cavity to be measured when no perturbation body is placed. ; Step 4: Place the perturbation body and the perturbation body tooling into the nose cone gap of the resonant cavity to be measured, and use a vector network analyzer to read the perturbation reflection coefficient at the working frequency of the resonant cavity to be measured when the perturbation body is placed. ; Step 5: Before and after the perturbation, the electromagnetic field at the corresponding position in space will change, and this change will be reflected in the reflection coefficient of the electromagnetic field. value; By comparing the reflection coefficient before perturbation in step 3 and the reflection coefficient after perturbation in step 4 Get the difference Δ between the electromagnetic field reflection coefficient before and after perturbation , to judge the changes in the electromagnetic field; Step 6: When multiple Δ When the consistency of the two is greater than 95%, it is determined that the processing of the resonant cavity to be tested meets the requirements; when one of the Δ When the consistency is less than 95%, it is determined that the processing of the resonant cavity to be tested does not meet the requirements.

2. The method for measuring microwave cavity field uniformity according to claim 1, wherein: In step 1, the perturbation body is made of metal material.

3. The method for measuring microwave cavity field uniformity according to claim 1, wherein: In step 2, the probe fixture is made of polytetrafluoroethylene material to fix the probe in the cavity of the nose cone hole.

4. The method for measuring microwave cavity field uniformity according to claim 3, wherein: The probe and the nose cone hole maintain the same axial direction.

5. The method for measuring microwave cavity field uniformity according to claim 1, wherein: In step 5, the relationship between the changes of the electromagnetic field of the resonant cavity to be measured before and after being perturbed is as follows: ； 、 are the reflection coefficients before and after perturbation, respectively; Δ is the difference in electromagnetic field reflection coefficient before and after perturbation; is the average microwave power entering the resonant cavity; 、 are the shape factors associated with the perturbator; is the angular frequency; E and H represent the changes in the electric field and magnetic field at the corresponding positions, respectively.

6. The method for measuring microwave cavity field uniformity according to claim 5, characterized in that: When the perturbation body is a cylindrical structure, Mainly determined by the electric field component; when the measured electric field is higher than the design value, the nose cone gap is reserved shorter, when the measured electric field is lower than the design value, the nose cone gap is reserved longer; or When the perturbation body is a circular ring structure, It is mainly determined by the magnetic field component; when the measured magnetic field is lower than the design value, the nose cone gap is reserved to be shorter, and when the measured magnetic field is higher than the design value, the nose cone gap is reserved to be longer.

7. The method for measuring microwave cavity field uniformity according to claim 1, characterized in that: In step 6, the consistency is multiple Δ Respectively with multiple Δ compared with the average value.

8. A testing device using the method for measuring microwave cavity field uniformity according to any one of claims 1 to 7, characterized in that: Including vector network analyzer, test connection line, probe and probe tooling, resonant cavity to be tested and perturbation body and perturbation body tooling; The probe is assembled into the nose cone hole of the resonant cavity to be measured through a probe fixture; The perturbation body is assembled in the nose cone gap of the resonant cavity to be measured through the perturbation body fixture; The vector network analyzer is connected to the probe via the test connection line.

9. The testing device according to claim 8, characterized in that: The perturbator is a metal material with a cylindrical, ring or cage-like structure.

10. The testing device according to claim 8, characterized in that: The probe fixture and the perturbation body fixture are respectively coaxially arranged with the drift tube.

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