Lumped parameter ferrite circulator based on LTCC (Low Temperature Co-Fired Ceramic) process

Abstract

The invention belongs to the field of microwave passive devices, and relates to a lumped parameter ferrite circulator based on an LTCC (Low Temperature Co-Fired Ceramic) process. The circulator comprises an inductor strip, an insulating layer, a central ferrite cylinder, an LTCC multi-layer ceramic dielectric plate and a metal grounding layer, wherein the inductor strip, a capacitor upper metal pole plate and the metal grounding layer adopt a three-dimensional laminated circuit structure design; the central ferrite cylinder is embedded in the LTCC multilayer ceramic dielectric plate and is used for applying a bias magnetic field perpendicular to the circulator; the whole device is realized based on an LTCC process, interlayer and external electrical connection is carried out through metalized via holes, the circuit design is simplified, and meanwhile, the size of the device is also reduced. According to the lumped parameter ferrite circulator, the structure and design defects of an existing lumped parameter ferrite circulator are overcome by adopting passive element integration, obvious progress is made in the aspects of electromagnetic performance, stability and efficiency, and innovation and practicability are shown in the aspects of device design scheme and material selection and application.

Description

Technical Field

[0001] The invention belongs to the field of microwave passive devices and relates to a lumped parameter ferrite circulator based on LTCC technology. Background Art

[0002] A circulator is a passive, non-reciprocal microwave magnetic device that can achieve unidirectional circular transmission of electromagnetic waves. The current demand for communication systems is broadband and miniaturization. For stripline and microstrip circulators, the lower the operating frequency, the larger the radius of the central guide disk of the circulator. However, for lumped parameter circulators, the size of the device has little to do with the frequency. The use of lumped element technology can effectively reduce the size of the circulator. Lumped parameter circulators are based on lumped parameter elements (such as inductors and capacitors) and achieve non-reciprocal transmission through discrete elements. Due to their own characteristics, they are mainly used in low-frequency applications in high-tech fields such as satellite communications and electronic countermeasures.

[0003] Existing lumped parameter circulators often still use surface mount capacitors in practical applications; however, in device design, discrete component surface mount capacitors will occupy a large space, increase device processing steps, and limit the miniaturization and integration of devices. Currently, the industry has not yet found a good way to achieve device miniaturization and integration while ensuring parameter performance for lumped parameter circulators.

[0004] The defects of existing circulators are mainly as follows:

[0005] Large size: In the L-band, traditional circulators are usually large in size and cannot meet the requirements of modern communication systems for miniaturization and integration of microwave devices.

[0006] Relatively low performance and integration levels: Existing circulator designs often cannot take into account low cost, high performance and high integration at the same time, and cannot meet the needs of modern communication systems. This is mainly because traditional circulator designs find it difficult to achieve both efficient RF characteristic optimization and high-density integration at the same time.

[0007] The main technical problems that need to be solved urgently are as follows:

[0008] How to achieve miniaturization: With the popularization of modern electronic communication equipment, the demand for miniaturization of communication equipment is becoming more and more important. Therefore, how to design and realize a smaller circulator is another important technical challenge.

[0009] How to improve performance and achieve high integration: Modern communication systems require high-performance, low-cost circulators. In addition, in order to adapt to the trend of miniaturization and integration, circulators must have the ability to be highly integrated with other microelectronic communication devices. Therefore, how to design and implement circulators with higher performance, lower cost and higher integration is an important technical challenge at present. Summary of the invention

[0010] In view of the above-mentioned problems, in order to solve the problem that the existing lumped parameter circulator cannot well meet the current application requirements for further miniaturization and integration, the present invention provides a lumped parameter ferrite circulator based on the LTCC process, which realizes the lumped parameter circulator through structural design optimization and combines the LTCC process to ensure miniaturization and integration while ensuring parameter performance.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] A lumped parameter ferrite circulator based on LTCC technology comprises an inductor strip, an insulating layer, a central ferrite column, an LTCC multilayer ceramic dielectric plate and a metal grounding layer.

[0013] The central ferrite column is embedded in the LTCC multilayer ceramic dielectric plate, and its upper and lower surfaces are coplanar with the upper and lower surfaces of the LTCC multilayer ceramic dielectric plate. The central ferrite column applies a bias magnetic field perpendicular to the circulator.

[0014] The LTCC multilayer ceramic dielectric plate comprises, from top to bottom, an LTCC dielectric layer upper plate, a capacitor upper metal plate and an LTCC dielectric layer lower plate.

[0015] The upper plate of the LTCC dielectric layer is provided with a first conductor via metal filling hole, a second conductor via metal filling hole and a grounding via metal filling hole; the lower plate of the LTCC dielectric layer is provided with a grounding via metal filling hole.

[0016] There are three metal plates on the capacitor, which are placed in the same layer between the upper and lower plates of the LTCC dielectric layer, and are interconnected with the three inductor strips one by one through the first conductor via metal filling holes; and are connected to the external feeding port through the second conductor via metal filling holes.

[0017] There are three inductor strips, which are stacked on the upper surface of the central ferrite cylinder and the LTCC multilayer ceramic dielectric board. Adjacent layers of inductor strips are separated by an insulating layer, and the three inductor strips are cross-stacked at 120 degrees to form a stacked mesh inductor structure of insulating layer-conductor-insulating layer-conductor-insulating layer-conductor from top to bottom; one end of each inductor strip is connected to the corresponding metal plate on the capacitor through a first conductor via metal filling hole, and the other end is connected to the metal grounding layer through a grounding via metal filling hole.

[0018] The metal grounding layer is located on the lower surface of the LTCC multilayer ceramic dielectric plate, and together with the metal plate on the capacitor, forms an embedded capacitor.

[0019] Furthermore, the central ferrite cylinder is made of microwave ferrite material with a high dielectric constant, a relative dielectric constant of 22 to 26, and a saturation magnetization intensity of 4πM.S It is 1600~1900Gs; the dielectric constant of LTCC multilayer ceramic dielectric board is 28~32, and the dielectric loss is below 0.001; the sintering temperature of all ceramic materials (including dielectric ceramics and gyromagnetic ferrites) is 880~920℃.

[0020] Furthermore, the inductor strip, metalized via, metal plate on the capacitor, and metal grounding layer are made of metals with high electrical conductivity such as gold, silver, or silver-palladium alloy.

[0021] Furthermore, the total thickness of the LTCC multilayer ceramic dielectric board is 0.3 mm, the thickness of the upper LTCC dielectric layer board is 0.2 mm, and the thickness of the lower LTCC dielectric layer board is 0.1 mm.

[0022] Furthermore, the thickness of the insulating layer is 0.02-0.05 mm.

[0023] The present invention utilizes LTCC technology and adopts passive components to integrate lumped parameter ferrite circulators to simultaneously meet the requirements of large capacitance and miniaturization. LTCC technology is a multi-layer wiring substrate technology that laminates unsintered cast ceramic diaphragms together to form a multi-layer circuit with printed interconnection conductors, components and circuits, and sinters the structure into an integrated ceramic multilayer material high-density microelectronic component technology; LTCC technology has the advantages of high packaging density, good radio frequency characteristics, high reliability, etc. Therefore, the present invention combines LTCC technology to prepare capacitors to achieve small size, low cost and system integration, so as to overcome the structural and design shortcomings of existing lumped parameter ferrite circulators and obtain a laminated lumped parameter ferrite circulator with a three-dimensional structure.

[0024] The lumped parameter ferrite circulator based on LTCC technology of the present invention has the following significant technical advances:

[0025] 1. Comprehensive application of high-performance materials: By using microwave ferrite with high dielectric constant and low sintering temperature, the performance of device materials is optimized, which helps to improve the electromagnetic performance of the circulator.

[0026] 2. Accurate electromagnetic matching: Due to the use of high-precision ceramic dielectric plates and ferrite materials, the electromagnetic matching is significantly improved, thereby improving the quality and efficiency of electromagnetic signal transmission.

[0027] 3. Extremely low dielectric loss: The dielectric loss of the ceramic dielectric plate used is less than 0.001, which greatly reduces the transmission loss of electromagnetic signals during operation and improves the working efficiency and performance of the circulator.

[0028] 4. High temperature stability: The sintering temperature of ceramic materials and ferrite materials is 880-920°C, which can ensure that the circulator can maintain a stable overall structure even in a high temperature environment.

[0029] 5. Optimized circuit design: The inductor strip, the metal plate on the capacitor and the metal ground layer adopt a stacked structure and are connected through metallized vias, which simplifies the circuit design and reduces the size of the device.

[0030] 6. High conductivity materials: The center conductor, stripline circuit, metal-filled holes and metal grounding layer are made of gold, silver or silver-palladium alloy with high conductivity, which further reduces resistance and loss.

[0031] 7. Miniaturization and high integration: Current lumped parameter circulators generally use surface mount components. The thickness of the components themselves and the surface mount process required for processing are not conducive to the miniaturization and integration of the device. Through LTCC technology, passive components can be directly embedded in multilayer ceramics, and multiple materials can be sintered together, effectively reducing the size of the device, which meets the needs of modern communication systems for device miniaturization and integration.

[0032] 8. Low cost and high manufacturability: The LTCC process is suitable for low-cost and large-scale manufacturing. At the same time, the process is mature, which is conducive to large-scale commercial application.

[0033] 9. Higher device stability: Compared with discrete components, co-fired integrated passive devices can omit solder joints, effectively avoiding solder joint failure. At the same time, they have a shorter heat dissipation path, which can effectively solve thermal stress problems.

[0034] In summary, the present invention is the first to combine LTCC technology with high dielectric constant gyromagnetic ferrite to obtain a three-dimensional laminated lumped parameter ferrite circulator, which realizes the three-dimensional design of the circuit structure, and adopts passive component integration to meet the needs of large capacitance and miniaturization at the same time, achieving small size, low cost and system integration to overcome the structural and design shortcomings of existing lumped parameter ferrite circulators. The present invention has not only made significant progress in electromagnetic performance, stability and efficiency, but also demonstrated innovation and practicality in device design and material selection and application. These advantages give lumped parameter ferrite circulators a broader and more efficient application prospect in modern communication electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the present invention.

[0036] Figure 2 It is a schematic diagram of the decomposition structure of the present invention.

[0037] Figure 3 It is a schematic diagram of the exploded structure of the LTCC multilayer ceramic dielectric board of the present invention.

[0038] Figure 4 It is a top view of the present invention.

[0039] Figure 5 It is a schematic top view of the planar structure of the LTCC multilayer ceramic dielectric board of the present invention.

[0040] Figure 6 FIG. 4 is an S-parameter curve of a lumped parameter ferrite circulator based on LTCC process according to an embodiment of the present invention.

[0041] Figure 7 FIG. 4 is an example of the relationship between the standing wave ratio and the frequency of a lumped parameter ferrite circulator based on the LTCC process.

[0042] Figure numerals: insulating layer 1, inductor strip 2, central ferrite cylinder 3, first conductor via metal filling hole 4, LTCC multilayer ceramic dielectric board 5, LTCC dielectric layer upper board 5-1, capacitor upper metal plate 5-2, grounding via metal filling hole 5-3, LTCC dielectric layer lower board 5-4, second conductor via metal filling hole 6, metal grounding layer 7. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0044] Example:

[0045] A lumped parameter ferrite circulator based on LTCC technology, see Figures 1 to 5 , there are three ports, including an inductor strip 2, an insulating layer 1, a central ferrite cylinder 3, a first conductor via metal filling hole 4, a LTCC multilayer ceramic dielectric board 5, a second conductor via metal filling hole 6 and a metal grounding layer 7.

[0046] The central ferrite column 3 is embedded in the LTCC multilayer ceramic dielectric plate 5, and its upper and lower surfaces are coplanar with the upper and lower surfaces of the LTCC multilayer ceramic dielectric plate. The central ferrite column 3 is made of YIG ferrite with a relative dielectric constant of 22 to 26 and a saturation magnetization of 1600 to 1900 Gauss, a diameter of 1.2 mm, and a thickness of 0.3 mm.

[0047] The LTCC multilayer ceramic dielectric plate 5 is located outside the central ferrite cylinder 3, and is composed of an LTCC dielectric layer upper plate 5-1, a capacitor upper metal plate 5-2, and an LTCC dielectric layer lower plate 5-4 from top to bottom. The total thickness of the LTCC multilayer ceramic dielectric plate 5 is 0.3 mm, the thickness of the LTCC dielectric layer upper plate 5-1 is 0.2 mm, and the thickness of the LTCC dielectric layer lower plate 5-4 is 0.1 mm.

[0048] The LTCC multilayer ceramic dielectric board is made of LTCC ceramic diaphragms with a relative dielectric constant of 30 and a loss tangent value of less than 0.001, and the outer dimensions are 4mm×4mm×0.3mm.

[0049] The upper plate 5-1 of the LTCC dielectric layer is provided with a first conductor via metal-filled hole 4, a second conductor via metal-filled hole 6 and a ground via metal-filled hole 5-3; the lower plate 5-1 of the LTCC dielectric layer is provided with a ground via metal-filled hole 5-3.

[0050] Three kinds of metallized circular vias are made on the LTCC multilayer ceramic dielectric board 5, and silver paste is used to fill the holes to make metallized vias 4, 5-3 and 6, and the diameter of each single circular hole is 0.1mm, wherein the height of the first conductor via metal filling hole 4 is 0.19mm, 0.25mm and 0.31mm respectively, the height of the grounding via metal filling hole 5-3 is 0.3mm, 0.36mm and 0.42mm respectively, and the height of the second conductor via metal filling hole 6 is 0.19mm. For the second conductor via metal filling hole 6, the three metallized circular vias corresponding to each port are connected through the metallized square filling holes that overlap with the three circular via structures, and are used as external feeding ports after being filled with silver paste. The square filling holes used to connect the circular vias are 0.4mm long, 0.1mm wide and 0.05mm deep. Silver paste is used to make three upper metal plates 5-2 of the capacitor at appropriate positions, with a thickness of 10μm, and the three external feeding ports are connected through the second conductor via metal filling holes 6.

[0051] There are three inductance bars 2, which are stacked on the central ferrite cylinder 3 and the upper surface of the LTCC multilayer ceramic dielectric plate 5; the adjacent layers of inductance bars 2 are separated by an insulating layer 1, so that the inductance bars 2 are not directly connected, and the three inductance bars 2 are cross-stacked at 120 degrees, and the mutual coupling is based on the gyromagnetic coupling of ferrite; from top to bottom, a laminated mesh inductance structure of insulation layer-conductor-insulation layer-conductor-insulation layer-conductor is formed; one end of each inductance bar 2 is connected to the corresponding metal plate 5-2 on the capacitor through the first conductor via metal filling hole 4, and the other end is connected to the metal grounding layer 7 through the grounding via metal filling hole 5-3. The thickness of the insulating layer 1 is 20μm. The thickness of the inductance bar 2 is 50μm.

[0052] The metal grounding layer 7 is located on the lower surface of the LTCC multilayer ceramic dielectric board 5 and together with the metal plate on the capacitor constitutes an embedded capacitor. The thickness of the metal grounding layer 7 is 0.1 mm.

[0053] The dimensions and material performance parameters of the above parts are calculated based on the non-reciprocal network theory of the circulator to obtain the initial values, and then the device model is established using the three-dimensional electromagnetic simulation software HFSS and simulation experiments are carried out. The final values ​​are obtained after parameter optimization. After optimization, the relationship between the device's input return loss S11, input return loss S22, isolation S12, insertion loss S21 and standing wave ratio VSWR and the operating frequency is as follows: Figure 6 and Figure 7 shown.

[0054] Since the circulator of this embodiment uses high dielectric constant YIG ferrite and LTCC passive components with a three-dimensional laminated structure, the device is miniaturized, with a size of only 4mm×4mm×0.58mm. In the frequency range of 1805MHz to 1880MHz, the isolation exceeds -19dB, the return loss is less than -19dB, and the insertion loss is greater than -0.2dB, which well takes into account the requirements of miniaturization and high performance. Compared with the prior art, the present invention realizes the lumped parameter ferrite circulator based on the LTCC process for the first time, which is smaller in size; and the process flow is more simplified, the process stability is better (failure of solder joints), and the system integration is better.

[0055] It can be seen from the above embodiments that the present invention adopts a three-dimensional laminated circuit structure design for the inductor strip, the metal plate on the capacitor and the metal grounding layer; the central ferrite cylinder is embedded in the LTCC multilayer ceramic dielectric plate to apply a bias magnetic field perpendicular to the circulator; the overall device is realized based on the LTCC process, and the interlayer and external electrical connections are made through metallized vias, which greatly simplifies the circuit design and also reduces the device size. The present invention uses passive component integration to meet the needs of large capacitance and miniaturization at the same time, achieving small size, low cost and system integration to overcome the structural and design shortcomings of existing lumped parameter ferrite circulators. The present invention has not only made significant progress in electromagnetic performance, stability and efficiency, but also demonstrated innovation and practicality in device design and material selection and application. These advantages make lumped parameter ferrite circulators have a broader and more efficient application prospect in modern communication electronic equipment.

Claims

1. A lumped parameter ferrite circulator based on LTCC technology, characterized in that: It includes an inductor strip, an insulating layer, a central ferrite cylinder, a LTCC multilayer ceramic dielectric board and a metal grounding layer; The central ferrite column is embedded in the LTCC multilayer ceramic dielectric board through the top and bottom, and the upper and lower surfaces of the central ferrite column are coplanar with the upper and lower surfaces of the LTCC multilayer ceramic dielectric board; The LTCC multilayer ceramic dielectric plates are respectively, from top to bottom, an LTCC dielectric layer upper plate, a capacitor upper metal plate and an LTCC dielectric layer lower plate; The upper plate of the LTCC dielectric layer is provided with a first conductor via metal filling hole, a second conductor via metal filling hole and a ground via metal filling hole; the lower plate of the LTCC dielectric layer is provided with a ground via metal filling hole; There are three upper metal plates of the capacitor, which are placed in the same layer between the upper and lower plates of the LTCC dielectric layer, and are interconnected with the three inductor strips one by one through the first conductor via metal filling holes; and connected to the external feeding port through a second conductor via metal filling hole; There are three inductance strips, which are stacked and arranged on the upper surface of the central ferrite cylinder and the LTCC multilayer ceramic dielectric plate. Adjacent layers of inductance strips are separated by an insulating layer, and the three inductance strips are cross-stacked at 120 degrees to form a stacked mesh inductance structure of insulating layer-conductor-insulating layer-conductor-insulating layer-conductor from top to bottom; one end of each inductance strip is connected to the corresponding metal plate on the capacitor through a first conductor via metal filling hole, and the other end is connected to the metal grounding layer through a grounding via metal filling hole; The metal grounding layer is located on the lower surface of the LTCC multilayer ceramic dielectric plate, and together with the metal plate on the capacitor, forms an embedded capacitor.

2. The lumped parameter ferrite circulator based on LTCC technology as claimed in claim 1, characterized in that: The central ferrite cylinder adopts microwave ferrite material with high dielectric constant, whose relative dielectric constant is 22-26 and saturation magnetization intensity is 1600-1900Gs; the dielectric constant of LTCC multilayer ceramic dielectric board is 28-32 and dielectric loss is below 0.001; the sintering temperature of all ceramic materials is 880-920℃.

3. The lumped parameter ferrite circulator based on LTCC process as claimed in claim 1, characterized in that: The materials of the inductor strip, the metalized via hole, the metal plate on the capacitor and the metal grounding layer are gold, silver or silver-palladium alloy.

4. The lumped parameter ferrite circulator based on LTCC process as claimed in claim 1, characterized in that: The thickness of the insulating layer is 0.02-0.05 mm.

5. The lumped parameter ferrite circulator based on LTCC process as claimed in claim 1, characterized in that: The total thickness of the LTCC multilayer ceramic dielectric board is 0.3 mm, wherein the thickness of the upper LTCC dielectric layer board is 0.2 mm, and the thickness of the lower LTCC dielectric layer board is 0.1 mm.

6. The lumped parameter ferrite circulator based on LTCC process as claimed in claim 1, characterized in that: The design method is as follows: the initial values ​​of the dimensions and material performance parameters of each component are calculated based on the non-reciprocal network theory of the circulator; then the device model is established and simulated using the three-dimensional electromagnetic simulation software HFSS, and the final values ​​are obtained after parameter optimization.

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