LTCC (Low Temperature Co-Fired Ceramic) ultra-miniaturized lumped parameter ferrite circulator

Abstract

The invention belongs to the field of microwave passive devices, and relates to an LTCC (Low Temperature Co-Fired Ceramic) ultra-miniaturized lumped parameter ferrite circulator. According to the invention, the inductor strip, the strip line circuit, the capacitor upper metal pole plate and the metal grounding layer are designed by adopting a three-dimensional laminated circuit structure; 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 greatly simplified, the size of the device is reduced, and the whole size is only 2mm * 2mm * 1.02 mm. The requirements of large capacitance and miniaturization are met at the same time, and subminiaturization, low cost and system integration are achieved; the lumped parameter ferrite circulator not only makes obvious progress in the aspects of electromagnetic performance, stability and efficiency, but also shows innovativeness and practicability in the aspects of device design scheme and material selection and application, and due to the advantages, the lumped parameter ferrite circulator has a wider and more efficient application prospect in modern communication electronic equipment.

Description

Technical Field

[0001] The invention belongs to the field of microwave passive devices and relates to an LTCC ultra-miniaturized lumped parameter ferrite circulator. Background Art

[0002] A circulator is a passive, non-reciprocal magnetic device that can control the unidirectional circular transmission of electromagnetic waves. The current communication system requires broadband and miniaturization. For a stripline circulator, the lower the operating frequency, the larger the radius of the central ferrite disk, which is not conducive to miniaturization. The size of a lumped parameter circulator has little to do with the frequency. The use of lumped element technology is a classic method to break through the relationship between the size and wavelength of a microwave circuit. Its adjustment process is mainly a simple eigenvalue problem.

[0003] Lumped parameter circulators are mainly used in low-frequency applications in high-tech fields such as satellite communications and electronic countermeasures. Surface mount capacitors are often used in actual applications. However, in device design, discrete surface mount capacitors take up a large space, limiting the miniaturization and integration of devices. Currently, the industry has not found a good way to achieve device miniaturization and integration while ensuring parameter performance. In RF modules, capacitors take up a large space, which also significantly limits the realization of system integration.

[0004] The defects of the prior art are mainly as follows:

[0005] Large size: Traditional lumped parameter circulators usually occupy a large space in the L-band and are not easy to meet the miniaturization requirements of modern communication systems.

[0006] Limited performance and integration: Existing circulator designs are difficult to achieve low cost, high performance, and high integration at the same time, and cannot meet the development needs of high-density integration of today's communication systems. This is mainly due to the inefficiency of traditional design methods in RF characteristic optimization and high-density integration.

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

[0008] How to achieve miniaturization: With the widespread use of mobile devices and IoT devices, the demand for miniaturization of communication equipment is increasing. Therefore, how to develop and design more compact circulators has become a key technical challenge.

[0009] How to improve performance and achieve high integration: Modern communication systems require high performance and low cost for circulators. At the same time, in order to meet the development trend of miniaturization and high integration, circulators need to be able to be integrated with other microelectronic devices. Therefore, how to develop circulators with better performance, lower cost and easy integration has become the current core technical problem. 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 an LTCC ultra-miniaturized lumped parameter ferrite circulator, which achieves ultra-miniaturization and system integration while ensuring the performance of the lumped parameter circulator through structural design and combined with the LTCC process.

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

[0012] A LTCC ultra-miniaturized lumped parameter ferrite circulator comprises an inductor strip, an insulating layer, and the following layers stacked in sequence from top to bottom: a high dielectric ferrite layer, a first metal grounding layer, a first LTCC ceramic dielectric layer, a strip line circuit, a second LTCC ceramic dielectric layer, a second metal grounding layer, a third LTCC ceramic dielectric layer, a metal plate on a capacitor, a fourth LTCC ceramic dielectric layer and a third metal grounding layer.

[0013] Among them, the number of inductor strips, stripline circuits and metal plates on capacitors is 3, and the three are in a one-to-one correspondence, that is, one inductor strip, one stripline circuit and one metal plate on a capacitor form a one-to-one correspondence.

[0014] The inductor strips are stacked on the upper surface of the high dielectric ferrite layer, adjacent layers of inductor strips are separated by an insulating layer, and 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.

[0015] The first metal grounding layer is connected to each inductor strip through metallized vias, and the second metal grounding layer is connected to the first and third metal grounding layers through metallized vias; the third metal grounding layer and the metal plates (three) on the capacitor constitute an embedded grounding capacitor, and the three grounding capacitors are placed on the same LTCC ceramic dielectric layer at the same time.

[0016] The inductor strip, stripline circuit and metal plate on the capacitor are connected through metallized vias penetrating each LTCC ceramic dielectric layer to form a non-reciprocal circuit of a three-dimensional laminated structure in a lumped parameter circulator. The specific connection relationship is:

[0017] One end of the inductor strip 1 is connected to the stripline circuit 1 through a metallized via, and the other end is connected to the first metal grounding layer through a metallized via; the stripline circuit 1 is connected to the metal plate 1 on the capacitor through the metallized via;

[0018] One end of the inductor strip 2 is connected to the stripline circuit 2 through a metallized via, and the other end is connected to the first metal grounding layer through a metallized via; the stripline circuit 2 is connected to the metal plate 2 on the capacitor through the metallized via;

[0019] One end of the inductor strip 3 is connected to the stripline circuit 3 through a metallized via, and the other end is connected to the first metal grounding layer through a metallized via; the stripline circuit 3 is connected to the metal plate 3 on the capacitor through the metallized via.

[0020] And the stripline circuit is connected to the external port through a metallized via to realize power feeding.

[0021] Furthermore, the high dielectric ferrite layer adopts microwave ferrite material with high dielectric constant, whose relative dielectric constant is 25-30 and 4πMs is 1200-1800Gs; the dielectric constant of the LTCC ceramic dielectric layer is 22-30 and the dielectric loss is below 0.001; the sintering temperature of the high dielectric ferrite and LTCC ceramic dielectric layer materials are both 880-900°C.

[0022] Furthermore, the inductor strip, the strip line circuit, the metalized via, the metal plate on the capacitor, the first, second and third metal grounding layers are made of gold, silver or silver-palladium alloy.

[0023] Furthermore, the thickness of the insulating layer is 0.05 mm.

[0024] Furthermore, the thickness of the inductor strip is 0.05 mm.

[0025] Furthermore, the thickness of the first, second and third metal grounding layers are all 0.05 mm.

[0026] Furthermore, the thickness of the first LTCC ceramic dielectric layer is 0.1 mm, the thickness of the second LTCC ceramic dielectric layer is 0.11 mm, the thickness of the third LTCC ceramic dielectric layer is 0.16 mm, the thickness of the fourth LTCC ceramic dielectric layer is 0.04 mm, and the plane area is 2 mm×2 mm.

[0027] Furthermore, the above-mentioned LTCC ultra-miniaturized lumped parameter ferrite circulator has an overall size of 2mm×2mm×1.02mm, an isolation of more than -18dB in the frequency range of 1805MHz to 1880GHz, a return loss of more than -18dB, and an insertion loss of more than -0.5dB.

[0028] 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 is made by stacking unsintered cast ceramic diaphragms together to form a multi-layer circuit with printed interconnection conductors, components and circuits, and firing 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, and high reliability. Therefore, the present invention uses a three-dimensional design of the circuit structure and 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 the existing lumped parameter ferrite circulators and obtain a laminated lumped parameter ferrite circulator with a three-dimensional structure.

[0029] The LTCC ultra-miniaturized lumped parameter ferrite circulator provided by the present invention has the following significant technical advances:

[0030] 1. Accurate electromagnetic matching: By adopting high-precision ceramic dielectric layers, the electromagnetic matching is significantly improved, and the quality and efficiency of signal transmission are improved.

[0031] 2. High temperature stability: The sintering temperature range of ceramic materials is 880-900°C, and it has excellent thermal stability, which can ensure that the circulator still has good electromagnetic performance under harsh conditions such as high temperature.

[0032] 3. Application of high-performance materials: The use of high dielectric constant and low-temperature sintered microwave ferrite optimizes the performance of ferrite materials, thereby broadening the operating range of the circulator and improving the electromagnetic performance while reducing the size of the device.

[0033] 4. Miniaturization and high integration: Using LTCC technology, passive components (such as inductors, capacitors, etc.) can be directly embedded in multilayer ceramics, which greatly reduces the volume and achieves high-density integration, which is suitable for the miniaturization requirements of modern communication equipment.

[0034] 5. High conductivity materials: Inductor strips, stripline circuits, metalized vias, metal plates on capacitors and metal ground layers are made of gold, silver or silver-palladium alloys with high conductivity, further reducing resistance and loss.

[0035] 6. Optimized circuit design: The stripline circuit adopts a laminated structure and is connected to the inductor strip through metallized vias, which simplifies the matching complexity of the circuit design and also reduces the size of the device.

[0036] 7. Optimization design of grounding capacitor: Compared with traditional lumped parameter circulators, the volume of the capacitor has always been a problem restricting the size of the lumped parameter circulator. The present invention greatly reduces the size of the circulator and realizes ultra-miniaturization of the device by making the third metal grounding layer and the metal plate on the capacitor form an LTCC buried grounding capacitor.

[0037] 8. Low cost and high manufacturability: LTCC process is easy to mass produce, with low manufacturing cost. At the same time, the process is mature and suitable for large-scale commercial applications.

[0038] 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.

[0039] In summary, the present invention is the first to obtain a laminated lumped parameter ferrite circulator with a three-dimensional structure based on high dielectric constant gyromagnetic ferrite and combined with LTCC technology, realizing the three-dimensional design of circuit (capacitor, inductor, transmission line) structure, and using passive component integration to simultaneously meet the needs of large capacitance and miniaturization; the overall size of the entire LTCC ultra-miniaturized lumped parameter ferrite circulator is only 2mm×2mm×1.02mm, and the isolation in the frequency range of 1805MHz~1880GHz exceeds -18dB, the return loss exceeds -18dB, and the insertion loss is greater than -0.5dB; ultra-miniaturization, low cost and system integration are achieved, overcoming the structural and design shortcomings of the existing lumped parameter ferrite circulator. The present invention has not only made significant progress in electromagnetic performance, stability and work efficiency, but also demonstrated innovation and practicality in device design and material selection and application. These advantages make the lumped parameter ferrite circulator have a broader and more efficient application prospect in modern communication electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the decomposition structure of the present invention.

[0041] Figure 2 Schematic diagram of the upper plane structure of the high dielectric ferrite layer in the embodiment.

[0042] Figure 3 FIG. 4 is a schematic diagram of the upper plane structure of the first LTCC ceramic dielectric layer in the embodiment.

[0043] Figure 4 Schematic diagram of the upper plane structure of the second LTCC ceramic dielectric layer in the embodiment.

[0044] Figure 5 FIG. 4 is a schematic diagram of the upper plane structure of the third LTCC ceramic dielectric layer in the embodiment.

[0045] Figure 6 FIG. 4 is a schematic diagram of the upper plane structure of the fourth LTCC ceramic dielectric layer in the embodiment.

[0046] Figure 7 It is a top view of the structure of the present invention.

[0047] Figure 8 FIG. 4 is an S-parameter curve of the LTCC ultra-miniaturized lumped parameter ferrite circulator of the embodiment.

[0048] Fig. 9 FIG. 4 is a graph showing the relationship between the standing wave ratio and frequency of the LTCC ultra-miniaturized lumped parameter ferrite circulator of the embodiment. DETAILED DESCRIPTION

[0049] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0050] Example:

[0051] An LTCC ultra-miniaturized lumped parameter ferrite circulator, see Figures 1 to 7 : comprising an inductor strip (2), an insulating layer (1), and the following stacked layers from top to bottom: a high dielectric ferrite layer (3), a first metal grounding layer (4), a first LTCC ceramic dielectric layer (5), a strip line circuit (6), a second LTCC ceramic dielectric layer (7), a second metal grounding layer (8), a third LTCC ceramic dielectric layer (9), a metal plate on a capacitor (10), a fourth LTCC ceramic dielectric layer (12), and a third metal grounding layer (13).

[0052] Insulation layer: Three insulation layers are placed above the three inductor strips respectively so that the inductor strips are not directly connected to each other. The thickness is 50μm.

[0053] Inductor strips: Three inductor strips are placed above the high-dielectric ferrite layer at an angle of 120°, each of which is separated by an insulating layer. The inductor strips are coupled to each other by the gyromagnetic coupling of the ferrite. The thickness is 50μm.

[0054] The thickness of the first, second and third metal grounding layers are all 50 μm, and electrical connection between layers is achieved through metallized vias (11).

[0055] High dielectric ferrite layer: located above the first metal grounding layer, using microwave ferrite material with high dielectric constant, its relative dielectric constant is 25-30, saturation magnetization 4πMs is 1200-1800Gs, and its size is 2mm×0.4mm. In this embodiment, six circular vias are made in this ceramic dielectric layer, such as Figure 2 As shown, the three metalized vias 11-3-1, 11-3-2, and 11-3-3 are vias for connecting the inductor strip and the strip line circuit, and the three metalized vias 11-3-4, 11-3-5, and 11-3-6 are vias for connecting the inductor strip and the first metal grounding layer. The metalized vias are filled with silver paste and have a diameter of 0.15 mm. A bias magnetic field perpendicular to the circulator is applied to the center area of ​​the high dielectric ferrite layer.

[0056] The first LTCC ceramic dielectric layer: It is made of LTCC ceramic films with a relative dielectric constant of 24 and a loss tangent of 0.001. It is located below the first metal grounding layer and has an outer contour size of 2mm×2mm×0.1mm. Figure 3 As shown: three vias 11-4-1, 11-4-2, and 11-4-3 are made on the first metal grounding layer, and the via radius is 0.21mm; seven circular vias are made on the first LTCC ceramic dielectric layer: 11-5-1, 11-5-2, 11-5-3, 11-5-4, 11-5-5, 11-5-6, and 11-5-7. The last vias numbered 1, 2, and 3 are vias for connecting inductors and strip circuits, and vias 4, 5, 6, and 7 are vias for connecting the first metal grounding plate and the second metal grounding plate. The metallized vias are made by filling with silver paste, with a diameter of 0.15mm and a height of 0.1mm.

[0057] The second LTCC ceramic dielectric layer is made of the same ceramic film as the first LTCC ceramic dielectric layer, and is arranged below the first LTCC ceramic dielectric layer 5, with the strip line circuit sandwiched between the two, and the outer contour size is 2mm×2mm×0.11mm. Figure 4 As shown: three rectangular electrodes 6-1, 6-2, and 6-3 are printed on the upper surface of the dielectric layer as feeding ports; three circular metallized vias 11-7-1, 11-7-2, and 11-7-3 are made on the dielectric layer to connect the capacitor and the stripline circuit; connecting vias 11-7-4, 11-7-5, 11-7-6, and 11-7-7 are made to connect the first metal grounding layer and the second metal grounding layer; the metallized vias are made by filling the holes with silver paste, and the diameter is 0.15 mm and the height is 0.11 mm. The stripline circuit is printed on the second LTCC ceramic dielectric layer and connected to the three external ports.

[0058] The third LTCC ceramic dielectric layer is made of the same ceramic diaphragm as the first LTCC ceramic dielectric layer, and is disposed below the second LTCC ceramic dielectric layer 7, with the second metal grounding layer sandwiched between the two, and the outer contour size is 2mm×2mm×0.16mm. The upper surface of this dielectric layer is fully metallized to make a second metal grounding layer with a thickness of 50μm, and three vias 11-8-1, 11-8-2, and 11-8-3 are made on the metal grounding layer, and the via radius is 0.21mm. Seven circular vias are made at positions 11-9-1, 11-9-2, 11-9-3, 11-9-4, 11-9-5, 11-9-6, and 11-9-7 on the dielectric layer, wherein vias 1, 2, and 3 are vias for connecting capacitors and stripline circuits, and vias 4, 5, 6, and 7 are vias for connecting the second metal grounding plate and the third metal grounding plate. The metallized vias are made by filling the holes with silver paste, and have a diameter of 0.15 mm and a height of 0.16 mm. The specific plane layout is as follows: Figure 5shown.

[0059] The fourth LTCC ceramic dielectric layer: It is made of the same ceramic diaphragm as the first LTCC ceramic dielectric layer, and is arranged below the third LTCC ceramic dielectric layer 9, with the upper metal plates (3) of the capacitor sandwiched between the two, and the outer contour size is 2mm×2mm×0.04mm. The lower surface of the dielectric layer is fully metallized, and a third metal grounding layer is made with a thickness of 50μm. Three square electrodes 10-1, 10-2, and 10-3 are printed on the upper surface of the dielectric layer, so that the three electrodes and the third metal grounding layer form an embedded capacitor. Vias 11-12-4, 11-12-5, 11-12-6, and 11-12-7 are made to connect the second metal grounding layer and the third metal grounding layer. The metallized vias are made by filling with silver paste, and the diameter is 0.15mm and the height is 0.04mm. The specific plane layout is as follows: Figure 6 shown.

[0060] The dimensions and material performance parameters of the above parts are calculated by the non-reciprocal network theory of the circulator to obtain the initial values, and then the device model is established and the simulation experiment is carried out using the three-dimensional electromagnetic simulation software HFSS. The final values ​​are obtained after parameter optimization. After optimization, the relationship between the input return loss S11, output return loss S22, isolation S12, insertion loss S21 and standing wave ratio VSWR of the device and the operating frequency is as follows: Figure 8 and Fig. 9 shown.

[0061] Since the circulator of this embodiment is a parallel capacitive junction circulator, the metallized vias connect the inductor strip, the embedded capacitor and the strip line circuit to form a three-dimensional laminated structure, and the strip transmission line and LTCC laminated capacitor of the three-dimensional laminated structure are used to achieve ultra-miniaturization of the device, with a size of only 2mm×2mm×1.02mm, and an isolation of more than -18dB, a return loss of more than -18dB, and an insertion loss of more than -0.5dB in the frequency range of 1805MHz to 1880GHz, 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.

[0062] It can be seen from the above embodiments that the present invention adopts a three-dimensional laminated circuit structure design for the inductor strip, stripline circuit, metal plate on the capacitor and metal grounding layer; the overall device is implemented based on the LTCC process, and the electrical connection between layers and the outside is carried out through metallized vias, which greatly simplifies the circuit design and also reduces the size of the device. 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 give lumped parameter ferrite circulators a broader and more efficient application prospect in modern communication electronic equipment.

Claims

1. An LTCC ultra-miniaturized lumped parameter ferrite circulator, characterized in that: It includes an inductor strip, an insulating layer, and the following layers stacked in sequence from top to bottom: a high dielectric ferrite layer, a first metal grounding layer, a first LTCC ceramic dielectric layer, a strip line circuit, a second LTCC ceramic dielectric layer, a second metal grounding layer, a third LTCC ceramic dielectric layer, a metal plate on a capacitor, a fourth LTCC ceramic dielectric layer, and a third metal grounding layer; Among them, the number of the inductor strip, the strip line circuit and the metal plate on the capacitor is 3, and the three are in a one-to-one correspondence; The inductor strips are stacked on the upper surface of the high dielectric ferrite layer, adjacent layers of inductor strips are separated by an insulating layer, and 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; The first metal grounding layer is connected to each inductor strip through a metallized via, and the second metal grounding layer is connected to the first and third metal grounding layers through a metallized via; the third metal grounding layer and the metal plate on the capacitor form an embedded grounding capacitor, and the three grounding capacitors are placed on the same LTCC ceramic dielectric layer at the same time; The inductor strip, the stripline circuit and the metal plate on the capacitor are connected through the metallized vias penetrating the LTCC ceramic dielectric layers to form a non-reciprocal circuit of a three-dimensional laminated structure in the lumped parameter circulator; the specific connection relationship is: One end of the inductor strip 1 is connected to the stripline circuit 1 through a metallized via, and the other end is connected to the first metal grounding layer through a metallized via; the stripline circuit 1 is connected to the metal plate 1 on the capacitor through the metallized via; One end of the inductor strip 2 is connected to the stripline circuit 2 through a metallized via, and the other end is connected to the first metal grounding layer through a metallized via; the stripline circuit 2 is connected to the metal plate 2 on the capacitor through the metallized via; One end of the inductor strip 3 is connected to the strip line circuit 3 through a metallized via, and the other end is connected to the first metal grounding layer through a metallized via; the strip line circuit 3 is connected to the metal plate 3 on the capacitor through the metallized via; And the stripline circuit is connected to the external port through a metallized via to realize power feeding.

2. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The high dielectric ferrite layer adopts microwave ferrite material with high dielectric constant, whose relative dielectric constant is 25-30 and 4πMs is 1200-1800Gs; the dielectric constant of the LTCC ceramic dielectric layer is 22-30 and the dielectric loss is below 0.001; the sintering temperature of the high dielectric ferrite and LTCC ceramic dielectric layer materials are both 880-900℃.

3. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The materials of the inductor strip, the strip circuit, the metalized via hole, the metal plate on the capacitor, and the first, second and third metal grounding layers are gold, silver or silver-palladium alloy.

4. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The thickness of the insulating layer is 0.05 mm.

5. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The thickness of the inductor strip is 0.05 mm.

6. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The thickness of the first, second and third metal grounding layers are all 0.05 mm.

7. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The thickness of the first LTCC ceramic dielectric layer is 0.1 mm, the thickness of the second LTCC ceramic dielectric layer is 0.11 mm, the thickness of the third LTCC ceramic dielectric layer is 0.16 mm, the thickness of the fourth LTCC ceramic dielectric layer is 0.04 mm, and the plane area of ​​each layer is 2 mm×2 mm.

8. The LTCC ultra-miniaturized lumped parameter ferrite circulator according to claim 1, characterized in that: The overall size is 2mm×2mm×1.02mm. The isolation exceeds -18dB in the frequency range of 1805MHz to 1880GHz, the return loss exceeds -18dB, and the insertion loss is greater than -0.5dB.

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