Laminated-type ceramic radio-frequency low pass filter and preparation method therefor

Abstract

The invention discloses a laminated-type ceramic radio-frequency low pass filter and a preparation method therefor. The low pass filter comprises four leading-out terminal electrodes and an inner circuit, wherein the electrodes are the input terminal positive electrode, the output terminal positive electrode and two common grounding terminals in sequence; and the inner circuit comprises an inner electrode which is formed by a plurality of built-in capacitors and a plurality of built-in inductors located in the three-dimensional spaces of different dielectric layers. The inductors are in vertical three-dimensional helical structure; and the dielectric layers of the inductors and the capacitors utilize high-frequency low-loss ceramic materials. According to the filter, the dielectric material layers are the high-frequency ceramic material layers; the capacitance and inductance of inner components can achieve minimal adjustment, and a monolithic structure can be realized easily; the preparation technology is mature; consistency is good; the filter is suitable for volume production; and therefore, the low pass filter has the advantages of high cut-off frequency, wide operating frequency range, high out-of-band rejection, good rectangular degree, high reliability and good radio-frequency usage consistency and the like.

Description

technical field [0001] The invention belongs to the technical field of filters, and more specifically relates to a laminated ceramic radio frequency low-pass filter and a preparation method thereof. Background technique [0002] A filter is a frequency-selective two-port network that has always played a very important role in the communications industry. [0003] The multilayer chip RF low-pass filter is a new type of filter. With the development of communication technology, its operating frequency range is getting wider and higher, and the frequency of use is getting higher and higher. The trend of miniaturization and high frequency development is very Obviously (the frequency of products in some fields has reached 40GHz, or even higher). The emergence of a new generation of mobile communication technology and the demand for new weapons and equipment have led to a rapid increase in the market demand for small-sized multilayer chip RF filters with a wide operating frequency...

AI Technical Summary

Problems solved by technology

[0005] At present, there are two main ways to develop and produce small-sized multilayer chip low-pass filters: purely inductive or purely capacitive single-element form and LC structure form, and its technology is mature in single-element form, but this small Size multilayer chip filters are mainly low cut-off frequency, and have the characteristics of low out-of-band suppression performance and poor squareness

[0006] Although the traditional LC structure filter is produced in a small area and has good in-band flatness, it has poor consistency in the use of radio frequency bands and is also difficult to mass produce

[0007] At present, most of the more mature multilayer chip filters adopt simple π-type and T-type structures such as "dual capacitor + single inductor" or "single capacitor + double inductor". The external suppression characteristics are good, but the cut-off frequency is low, which leads to the limitation of its use frequency, and it is difficult to develop in the direction of high frequency

[0008] In addition, there are always some deficiencies in the announced low-pass filter with laminated multilayer ceramic structure, such as the prior art 1, the publication number is CN1578129, and the title of the invention is "a multilayer chip ceramic low-pass filter" In the patent application documents of , the low-pass filter adopts a planar spiral inductance structure. In the small-volume microwave segment filter, the parasitic capacitance introduced by the inductance of this structure has a great influence on the frequency characteristics, and as its volume becomes smaller, Its influence is getting deeper and deeper

[0009] Prior art 2 is a patent application document with the publication number CN101404485A and the title of the invention "a laminated chip filter and its preparation method", in which the filter is prepared by co-firing ferrite and ceramics. Size, large out-of-band rejection, large rectangularity, wide operating frequency, etc., but relatively low cut-off frequency, and poor reliability of the filter, etc.

Reasons for poor reliability: It is not easy to match the special-shaped materials between ferrite and ceramic materials

Especially when the use environment is relatively harsh, the stress between the special-shaped materials will inevitably occur, which will easily lead to cracks inside the product, which will affect its use

[0010] Prior art 3. The publication number is CN10216396A, and the patent application document of the invention title is "a multi-layer chip filter and its preparation method", in which the filter is prepared by punching holes in the ceramic dielectric material and injecting ferrite material , although to a certain extent alleviated the problem of reliability caused by the matching of heterogeneous materials of the filter in the patent publication number CN101404485A, it still cannot be completely avoided, and there is still a hidden danger of test reliability

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