Preparation method of garnet ferrite with high dielectric constant and medium saturation magnetization for microwave communication

Abstract

The invention discloses a preparation method of garnet ferrite with high dielectric and medium saturation magnetization for microwave communication, and belongs to the field of microwave ferrite materials. According to the characteristics of the oxide raw material, a multi-stage sintering process is adopted, the solid-phase reaction completion degree in the sintering stage is higher, and the material performance is more excellent; the sintering process is optimized, composition segregation is inhibited, the porosity is reduced, a sintered sample is more compact, the microstructure is improved, the dielectric loss is reduced, and the performance of the material is improved; the process is simple, the production period is short, the adopted formula does not contain lanthanide rare earth ions, and the material production cost is low. Meanwhile, the invention provides a C-band miniaturized microstrip circulator, which adopts a novel structural design of combining a small Y junction and a fishbone, realizes good impedance matching between the circulator and an external circuit, has the advantages of compact structure, small volume, light weight, low loss and the like, and can be mainly applied to various same-frequency duplexer systems.

Description

Technical Field

[0001] The present invention belongs to the field of microwave ferrite materials, and particularly relates to a preparation method of garnet ferrite with high permittivity and medium saturation magnetization for microwave communication. Background Art

[0002] In radar and 5G communication systems, as a duplex device, the ferrite circulator plays roles such as two-way signal transmission and isolation. With the development of microwave communication systems, the requirements for device miniaturization, light weight, and high performance are becoming increasingly stringent. According to the working principle of the ferrite circulator and electromagnetic wave theory, high frequency is an important way to miniaturize the device. However, for ferrite circulators that need to operate in the low-frequency microwave band, to achieve miniaturization and light weight, it is necessary to improve the performance of ferrite materials and the design of the circulator. According to the design theory of the ferrite circulator, the radius of the conductor junction of the circulator is inversely proportional to the square root of the dielectric constant and the effective magnetic permeability of the ferrite material. Therefore, increasing the microwave dielectric constant (ε′) of the ferrite material and using a ferrite / dielectric ceramic composite substrate have become important technical ways for the miniaturization, light weight, and low-loss design of the circulator. As an important type of ferrimagnetic material, garnet ferrite has the unique advantage of low loss. Since its saturation magnetization is not high, usually lower than 2000 Gs, it has become the preferred material for L-X band ferrite circulators.

[0003] In recent years, the rise of high-permittivity garnet ferrite materials has provided key material support for the miniaturization and light weight of ferrite circulators. The dielectric constant of conventional yttrium iron garnet ferrite is relatively low (about 14), while the dielectric constant of current high-permittivity garnet ferrite can be as high as about 25. The main technical way to increase the dielectric constant of ferrite is to increase the concentration of polarized ions inside the ferrite through ion substitution. However, this will cause other performance degradation of the material, such as an increase in the ferromagnetic resonance line width and a decrease in the Curie temperature. Research results show that the ferromagnetic resonance line width of conventional dielectric constant yttrium iron garnet ferrite polycrystalline materials can be as low as about 10 Oe, while the ferromagnetic resonance line width of high-permittivity yttrium iron garnet ferrite polycrystalline materials is usually about 30 Oe. Especially for garnet ferrite materials with a dielectric constant higher than 25, it is not only difficult to obtain a low ferromagnetic resonance line width but also difficult to obtain low microwave dielectric loss. Since the ferromagnetic resonance line width and dielectric loss are important parts of the microwave loss of ferrite, they will have an important impact on the insertion loss, bandwidth, etc. of the circulator. For garnet ferrite with medium saturation magnetization, it is usually necessary to use non-magnetic metal ions to replace magnetic Fe 3+Ions are used to reduce the saturation magnetization, but this will cause a decrease in the Curie temperature of the material, resulting in a decrease in the temperature stability of the material and further a decrease in the temperature stability of the device. Therefore, how to obtain garnet ferrite materials with high permittivity, low loss, and high temperature stability has become a research hotspot in ferrite materials. Existing high-permittivity garnet ferrite materials mostly use precious indium or lanthanide rare-earth ions to regulate the linewidth and temperature stability of the materials. With the further improvement of the requirements for circulators, there is still a need and room for further optimization and improvement in the performance and preparation process of such garnet ferrite materials.

[0004] Ferromagnetic circulators for C-band usually adopt low-field design. The ferrite material works on the left side of the ferromagnetic resonance region, and both the normalized magnetization intensity (P) and the normalized magnetic field intensity (σ) are less than 1, making it difficult to achieve miniaturized design. And the microwave wavelength (λ) range of the C-band is 3.75 cm to 7.5 cm. Limited by the microwave wavelength, it is difficult to reduce the volume of the microstrip circulator when using λ / 4 multiples for impedance matching, which is not conducive to the miniaturization and lightweight development of microwave components. Summary of the Invention

[0005] The present invention mainly aims at the problems of miniaturization, lightweight, and large bandwidth of garnet ferrite devices, and proposes a preparation method of high-permittivity medium-saturation magnetization garnet ferrite for microwave communication, focusing on improving the permittivity of the garnet ferrite material, reducing the ferromagnetic resonance linewidth and microwave dielectric loss, so as to meet the requirements of miniaturization, lightweight, and large bandwidth for ferrite circulators / isolators applied to radar and 5G communication systems. Adopting a multi-step sintering process to improve the uniformity of the material microstructure, enabling the ferrite to have a high permittivity (the permittivity ε' is about 28), medium saturation magnetization (4πM s is about 1250 Gs), low ferromagnetic resonance linewidth (ΔH ≤ 25 Oe), and low microwave dielectric loss (tanδ ε ≤ 2×10 -4 ).

[0006] The technical solution adopted by the present invention is as follows:

[0007] A preparation method of high-permittivity medium-saturation magnetization garnet ferrite for microwave communication, comprising the following steps:

[0008] Step 1. Batching:

[0009] Using analytically pure Y2O3, Bi2O3, CaCO3, ZrO2, V2O5, CuO, ZnO, and Fe2O3 as raw materials, according to the chemical formula Bi a Ca b Y 3-a-b Zr c V d Cu e Zn fFe 5-c-d-e-f-δ O 12 Calculate the stoichiometric ratio of and weigh the raw materials; where 1 ≤ a ≤ 1.5, 0.5 ≤ b ≤ 1.5, 0.1 ≤ c ≤ 0.6, 0.2 ≤ d ≤ 0.6, 0.02 ≤ e ≤ 0.05, 0.01 ≤ f ≤ 0.04, 0 ≤ δ ≤ 0.03, and δ is the iron deficiency amount;

[0010] Step 2. Primary ball milling:

[0011] Add deionized water to the powder weighed in Step 1 for primary ball milling. The ball milling speed is 220 - 260 rpm, the ball milling time is 4 - 8 h, and the powder particle size D50 is 0.8 - 1.0 μm;

[0012] Step 3. Pre - sintering:

[0013] Dry the primary ball - milled material obtained in Step 2, then screen it and perform pre - sintering. The pre - sintering temperature is 800 - 900 °C and the time is 3 - 5 h;

[0014] Step 4. Secondary ball milling:

[0015] Add deionized water to the pre - sintered material obtained in Step 3 for secondary ball milling. The ball milling speed is 220 - 260 rpm, the ball milling time is 8 - 12 h, and the powder particle size D50 is 1.2 - 2.5 μm;

[0016] Step 5. Granulation:

[0017] Dry the secondary ball - milled material obtained in Step 4, then add a binder and perform granulation and screening;

[0018] Step 6. Molding:

[0019] Press the granulated material obtained in Step 5 into shape. The pressing pressure is 180 - 210 MPa;

[0020] Step 7. Sintering:

[0021] Sinter the green compact obtained by pressing in Step 6 in a high - temperature furnace. The sintering temperature is 900 - 1000 °C, the holding time is 10 h. After sintering, the garnet ferrite is obtained.

[0022] Furthermore, the purity of each raw material in Step 1 is: the purity of Y2O3 is 99.99%, the purity of Fe2O3 is 99.3%, the purity of CaCO3 is 98.5%, the purity of Bi2O3 is 99%, the purity of ZrO2 is 99%, the purity of V2O5 is 99%, the purity of CuO is 99%, and the purity of ZnO is 99%.

[0023] Furthermore, in Step 2, the mass ratio of balls : powder : deionized water is 4 : 1 : 1.5.

[0024] Further, the process of pre-sintering described in step 3 is as follows: In the heating stage, first use rapid heating, with a heating rate of 1-2 °C / min to raise the temperature to 500 °C, and then raise it to the target temperature of 800-900 °C at a rate of 0.5-1 °C / min, and keep the temperature for 3-5 h; In the cooling stage, a combined fast and slow cooling rate is used to control grain defects, average particle size, and microstructural uniformity. Specifically, when the temperature is above 500 °C, use rapid cooling, with a rate of 3-4 °C / min; when the temperature is less than 500 °C, use slow cooling, with a rate of 1-2 °C / min.

[0025] Further, in step 4, the mass ratio of ball:material:deionized water is 4:1:1.5.

[0026] Further, in step 5, the binder is an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 8-15 wt%, and the particle size D50 of the granulated powder is 200-250 μm.

[0027] Further, in step 7, the sintering process is a multi-stage sintering process. First, use rapid heating, with a heating rate of 3-4 °C / min. After raising the temperature to 650 °C, use slow heating, with a rate of 0.5-1 °C / min. After raising the temperature to the sintering target temperature of 900-1000 °C, keep the temperature for 10 h; In the cooling stage, use rapid cooling with a rate of 2-3 °C / min when the temperature is above 700 °C, and cool down to room temperature at a rate of 0.5-0.7 °C / min when the temperature is below 700 °C, and finally obtain a high-performance ferrite substrate.

[0028] A C-band miniaturized microstrip circulator includes a dielectric substrate, a ferrite wafer surrounded by the dielectric substrate, and microstrip circuits located on the upper and lower surfaces of the ferrite wafer and the dielectric substrate; Among them, the ferrite wafer is a high-dielectric medium-saturation magnetization garnet ferrite substrate prepared by the above method, with a dielectric constant ε′ of 27-29 and a saturation magnetization 4πM s of 1240-1260 Gs, an iron resonance line width ΔH of 22-26 Oe, and a dielectric loss tanδ ε of 1-2×10 -4 ; The microstrip circuit is a double-Y-junction microstrip circuit.

[0029] Further, the dielectric constant of the dielectric substrate is 30, which is comparable to that of the ferrite wafer; the diameter of the ferrite wafer is 2.8-3.5 mm, and the size of the composite structure of the ferrite wafer and the dielectric substrate is 8 mm (length) × 8 mm (width) × 0.5 mm (height) (excluding the permanent magnet).

[0030] Further, the microstrip circuit is a double-Y microstrip circuit, including a large-Y junction, a small-Y junction, and a fishbone structure. The large-Y junctions form an angle of 120° with each other, and the large-Y junction and the small-Y junction form an angle of 60°. The fishbone structure is located between the large-Y junction and the small-Y junction, playing a role in optimizing the impedance matching of the circuit. The central metal circular junction of the large-Y junction is connected to the microstrip line port through a matching circuit to achieve broadband matching of the circuit.

[0031] Further, the small-Y junction includes a narrow strip portion connected to the central metal circular junction of the large-Y junction and a wide strip portion away from the central metal circular junction of the large-Y junction. Among them, the width of the narrow strip portion is 0.35 - 0.55 mm, the width of the wide strip portion is 1.6 - 2 mm, and a slit with a designed width of 0.2 - 0.3 mm is provided in the wide strip portion.

[0032] Further, the width of the fishbone structure is 0.08 - 0.13 mm, and the angle between adjacent fishbones is 10°.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The preparation method of the high-dielectric and medium-saturation magnetization garnet ferrite material for microwave communication provided by the present invention adopts a multi-stage sintering process according to the characteristics of the oxide raw materials. The solid-phase reaction in the sintering stage is more complete, and the material properties are more excellent. The sintering process is optimized to inhibit component segregation, reduce the porosity, make the sintered sample more dense, improve the microstructure, reduce the dielectric loss, and enhance the material properties. The process is simple, the production cycle is short, and the lanthanide rare-earth ions are not contained in the formula, so the material production cost is low.

[0035] 2. The high-dielectric and medium-saturation magnetization garnet ferrite substrate material prepared by the present invention has a dielectric constant of about 28, an iron resonance linewidth ΔH ≤ 25 Oe, a saturation magnetization of 4πM s of about 1250 Gs, and a dielectric loss tanδ ε ≤ 2×10 -4 . It can effectively reduce the design size of microwave ferrite devices, meet the development requirements of miniaturization. The low linewidth can reduce the insertion loss of the device, which helps to increase the working bandwidth of microwave devices.

[0036] 3. A C-band miniaturized microstrip circulator proposed by the present invention adopts a novel structural design combining a new type of small-Y junction and "fishbone" to achieve good impedance matching between the circulator and the external circuit. It has the advantages of compact structure, small volume, light weight, low loss, etc., and can be mainly applied to various co-frequency duplexer systems. Compared with conventional garnet ferrite materials, after applying the garnet ferrite material with high dielectric constant and low loss provided by the present invention, the volume of the device is reduced by about 40%, and the device has excellent performance. Description of the Drawings

[0037] Figure 1 SEM image of the ferrite material of Example 1;

[0038] Figure 2 SEM image of the ferrite material of Example 2;

[0039] Figure 3 XRD pattern for phase analysis of the ferrite material of Example 1;

[0040] Figure 4 XRD pattern for phase analysis of the ferrite material of Example 2;

[0041] Figure 5 Schematic diagram of the circulator structure of Example 3;

[0042] Figure 6 Simulation result diagram of the circulator of Example 3; where, (a) return loss, (b) isolation, (c) insertion loss, (d) voltage standing wave ratio. Detailed implementation manners

[0043] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0044] Example 1

[0045] A preparation method of a high-dielectric and medium-saturation magnetization garnet ferrite material for microwave communication, comprising the following steps:

[0046] Step 1. Batching:

[0047] Using Y2O3 with a purity of 99.99%, Bi2O3 with a purity of 99%, CaCO3 with a purity of 98.5%, ZrO2 with a purity of 99%, V2O5 with a purity of 99%, CuO with a purity of 99%, ZnO with a purity of 99%, and Fe2O3 with a purity of 99.3% as raw materials, and weighing the raw materials according to the stoichiometric ratio of the chemical formula Bi a Ca b Y 3-a-b Zr c V d Cu e Zn f Fe 5-c-d-e-f-δ O 12 ; where a = 1.245, b = 1.31, c = 0.44, d = 0.46, e = 0.03, f = 0.02, δ = 0;

[0048] Step 2. Primary ball milling:

[0049] The powder weighed in step 1 was added with deionized water and ball-milled once, the ball-milling speed was 241 rpm, the ball-milling time was 6 h, and the powder particle size D50 was 0.8-1.0 μm;

[0050] Step 3. Pre-burn:

[0051] The primary ball mill obtained in step 2 is dried, sieved, and pre-fired at a temperature of 860°C for 5 hours;

[0052] Step 4. Secondary ball milling:

[0053] The pre-sintered material obtained in step 3 was added with deionized water for secondary ball milling, the ball milling speed was 241 rpm, the ball milling time was 8 h, and the powder particle size D50 was 1.2-2.5 μm;

[0054] Step 5. Granulation:

[0055] After drying the secondary ball-milled material obtained in step 4, a 12 wt% polyvinyl alcohol (PVA) aqueous solution is added to granulate and screen;

[0056] Step 6. Molding:

[0057] The granulated material obtained in step 5 is pressed into a mold at a pressing pressure of 200 MPa;

[0058] Step 7. Sintering:

[0059] The green compact formed in step 6 is sintered in a high temperature furnace at a sintering temperature of 900-1000° C. for a holding time of 10 hours. After sintering, the garnet ferrite is obtained.

[0060] Example 2

[0061] A method for preparing a high-dielectric medium saturation magnetization garnet ferrite material for microwave communication comprises the following steps:

[0062] Step 1. Ingredients:

[0063] Using 99.99% pure Y2O3, 99% pure Bi2O3, 98.5% pure CaCO3, 99% pure ZrO2, 99% pure V2O5, 99% pure CuO, 99% pure ZnO and 99.3% pure Fe2O3 as raw materials, according to the chemical formula Bi a Ca b Y 3-a-b Zr c V d Cu e Zn f Fe 5-c-d-e-f-δ O 12Calculate the stoichiometric ratio and weigh the raw materials; where a = 1.290, b = 1.31, c = 0.44, d = 0.46, e = 0.03, f = 0.02, δ = 0;

[0064] Step 2. Primary ball milling:

[0065] Add deionized water to the powder weighed in Step 1 for primary ball milling. The ball milling speed is 241 rpm, the ball milling time is 5 h, and the powder particle size D50 is 0.8 - 1.0 μm;

[0066] Step 3. Pre-sintering:

[0067] Dry and screen the primary ball milled material obtained in Step 2, and then perform pre-sintering. The pre-sintering temperature is 860 °C and the time is 5 h;

[0068] Step 4. Secondary ball milling:

[0069] Add deionized water to the pre-sintered material obtained in Step 3 for secondary ball milling. The ball milling speed is 241 rpm, the ball milling time is 8 h, and the powder particle size D50 is 1.2 - 2.5 μm;

[0070] Step 5. Granulation:

[0071] After drying the secondary ball milled material obtained in Step 4, add an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 12 wt% and perform granulation and screening;

[0072] Step 6. Molding:

[0073] Press the granulated material obtained in Step 5 into shape, and the pressing pressure is 200 MPa;

[0074] Step 7. Sintering:

[0075] Sinter the green compact obtained by pressing in Step 6 in a high-temperature furnace. The sintering temperature is 900 - 1000 °C, the holding time is 10 h, and after sintering is completed, the garnet ferrite is obtained.

[0076] The properties of the ferrite materials obtained in Examples 1 - 2 are shown in Table 1:

[0077] Table 1 Properties of Ferrite Materials in Examples 1 - 2

[0078]

[0079] Example 3

[0080] A C-band miniaturized microstrip circulator, as Figure 5As shown in the figure, it includes a dielectric substrate, a ferrite wafer surrounded by the dielectric substrate, and microstrip circuits located on the upper and lower surfaces of the ferrite wafer and the dielectric substrate. Among them, the ferrite wafer is a high-dielectric medium-saturation magnetization garnet ferrite substrate prepared in Example 1. The diameter of the ferrite wafer is 3.2 mm, and the size of the composite structure of the ferrite wafer and the dielectric substrate is 8 mm (length) × 8 mm (width) × 0.5 mm (height) (excluding the permanent magnet). The dielectric constant of the dielectric substrate is 30. The microstrip circuit is a double-Y-junction microstrip circuit, including a large Y-junction, a small Y-junction, and a fishbone structure. The angle between the large Y-junctions is 120°, the angle between the large Y-junction and the small Y-junction is 60°, and the fishbone structure is located between the large Y-junction and the small Y-junction. The small Y-junction includes a narrow strip part connected to the central metal round junction of the large Y-junction and a wide strip part far from the central metal round junction of the large Y-junction. Among them, the width of the narrow strip part is 0.5 mm, the width of the wide strip part is 1.8 mm, a gap with a designed width of 0.3 mm is provided in the wide strip part, the width of the fishbone structure is 0.12 mm, and the angle between adjacent fishbones is 10°.

[0081] After the microwave signal is input from the microstrip port 1, it enters the central junction through the matching circuit, circulates under the action of the ferrite, enters the matching circuit connected to the next microstrip port, and then is transmitted to the microstrip port 2. The neodymium iron boron permanent magnet biases the ferrite.

[0082] Figure 6 The S-parameters and standing wave ratio simulation results of the miniaturized microstrip circulator in Example 3 are shown. It can be seen that the circulator has excellent circulation function in the frequency band of 4.63 - 6 GHz. The insertion loss from the microstrip port 1 to the microstrip port 2 is less than 0.26 dB. The reverse isolation S from the microstrip port 1 to the microstrip port 2 12 is greater than 20 dB within 4.63 - 6 GHz, the 20 dB bandwidth is 1.37 GHz, and the insertion loss S 21 is less than 0.26 dB within 4.5 - 6 GHz, and the voltage standing wave ratio is less than 1.25 within 4.63 - 6 GHz.

[0083] The overall size of the circulator in Example 3 is 8 mm × 8 mm × 0.5 mm (excluding the permanent magnet), with a small size, light weight, and relatively compact structure. Compared with the C-band traditional circulator using conventional ferrite materials and conventional structures, the volume of the miniaturized microstrip circulator of the present invention is reduced by about 40%, and the relative bandwidth reaches about 26%.

Claims

1. A preparation method of garnet ferrite with high dielectric constant and medium saturation magnetization for microwave communication, characterized in that, It includes the following steps: Step 1. Batching: Using Y2O3, Bi2O3, CaCO3, ZrO2, V2O5, CuO, ZnO and Fe2O3 as raw materials, according to the chemical formula Bi a Ca b Y 3-a- b Zr c V d Cu e Zn f Fe 5-c-d-e-f-δ O 12 Calculate and weigh the raw materials; where 1 ≤ a ≤ 1.5, 0.5 ≤ b ≤ 1.5, 0.1 ≤ c ≤ 0.6, 0.2 ≤ d ≤ 0.6, 0.02 ≤ e ≤ 0.05, 0.01 ≤ f ≤ 0.04, 0 ≤ δ ≤ 0.03, and δ is the iron deficiency amount; Step 2. Primary ball milling: Perform primary ball milling on the powder materials weighed in Step 1; Step 3. Pre-sintering: Dry and screen the primary ball milled materials obtained in Step 2, and then perform pre-sintering. The pre-sintering temperature is 800 - 900 °C, and the time is 3 - 5 h; Step 4. Secondary ball milling: Perform secondary ball milling on the pre-sintered materials obtained in Step 3; Step 5. Granulation: After drying the secondary ball milled materials obtained in Step 4, perform granulation; Step 6. Molding: Press the granulated materials obtained in Step 5 into a mold; Step 7. Sintering: Sinter the green compact obtained by pressing in Step 6 in a high-temperature furnace. The sintering temperature is 900 - 1000 °C, and the holding time is 10 h. After sintering is completed, the garnet ferrite is obtained.

2. The preparation method of the garnet ferrite with high dielectric constant and medium saturation magnetization for microwave communication according to claim 1, wherein, In Step 2, the mass ratio of balls:materials:deionized water is 4:1:1.5, the ball milling rotation speed is 220 - 260 rpm, the ball milling time is 4 - 8 h, and the powder particle size D50 is 0.8 - 1.0 μm.

3. The preparation method of the garnet ferrite with high dielectric constant and medium saturation magnetization intensity for microwave communication according to claim 1, characterized in that, The process of the pre-sintering in Step 3 is as follows: In the heating-up stage, first increase the temperature to 500 °C at a heating rate of 1 - 2 °C / min, and then increase the temperature to the target temperature of 800 - 900 °C at a heating rate of 0.5 - 1 °C / min, and hold for 3 - 5 h; In the cooling-down stage, the cooling rate is 3 - 4 °C / min when the temperature is above 500 °C, and the cooling rate is 1 - 2 °C / min when the temperature is less than 500 °C.

4. The preparation method of the garnet ferrite with high dielectric constant and medium saturation magnetization for microwave communication according to claim 1, characterized in that, In Step 4, the mass ratio of balls:materials:deionized water is 4:1:1.5, the ball milling rotation speed is 220 - 260 rpm, the ball milling time is 8 - 12 h, and the powder particle size D50 is 1.2 - 2.5 μm.

5. The preparation method of the garnet ferrite with high dielectric constant and medium saturation magnetization intensity for microwave communication according to claim 1, characterized in that, The process of the sintering in Step 7 is as follows: In the heating-up stage, first increase the temperature to 650 °C at a heating rate of 3 - 4 °C / min, and then increase the temperature to the sintering target temperature of 900 - 1000 °C at a heating rate of 0.5 - 1 °C / min, and then hold for 10 h; In the cooling-down stage, the cooling rate is 2 - 3 °C / min when the temperature is above 700 °C, and the cooling rate is 0.5 - 0.7 °C / min when the temperature is below 700 °C.

6. A C-band miniaturized microstrip circulator, characterized in that, It includes a dielectric substrate, a ferrite wafer surrounded by the dielectric substrate, and microstrip circuits located on the upper and lower surfaces of the ferrite wafer and the dielectric substrate; among them, the ferrite wafer is a high-dielectric medium-saturation magnetization garnet ferrite substrate obtained by the method described in any one of Claims 1 - 5.

7. The C-band miniaturized microstrip circulator according to claim 6, characterized in that, The dielectric constant of the dielectric substrate is 30, and the diameter of the ferrite wafer is 2.8 - 3.5 mm.

8. The C-band miniaturized microstrip circulator according to claim 6, characterized in that, The microstrip circuit is a double-Y-junction microstrip circuit, including a large Y-junction, a small Y-junction, and a fishbone structure. The angle between the large Y-junctions is 120°, the angle between the large Y-junction and the small Y-junction is 60°, and the fishbone structure is located between the large Y-junction and the small Y-junction.

9. The C-band miniaturized microstrip circulator according to claim 8, characterized in that, The small Y-junction includes a narrow strip part connected to the central metal circular junction of the large Y-junction and a wide strip part far from the central metal circular junction of the large Y-junction. Among them, the width of the narrow strip part is 0.35 - 0.55 mm, the width of the wide strip part is 1.6 - 2 mm, and there is a gap with a designed width of 0.2 - 0.3 mm in the wide strip part; the width of the fishbone structure is 0.08 - 0.13 mm, and the angle between adjacent fishbones is 10°.

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