CN110492208A - The flat coaxial cavity filter of miniaturization - Google Patents

Abstract

The invention proposes a miniaturized flat coaxial cavity filter, which mainly solves the problems of complicated assembly, high cost and large loss of the current coaxial filter. It includes an upper metal cover (1), two feed structures (2), an intermediate metal inner conductor (3) and a lower metal cover (4); the two feed structures are located on the upper metal cover, The middle metal inner conductor is sandwiched between the upper metal cover and the lower metal cover; the upper metal cover is provided with a plurality of upper partitions (13) and a plurality of tuning screws (12), and the middle metal inner conductor includes two The taps (32), multiple resonators (33) and peripheral fixing parts (31) are of an integrated structure; the lower metal cover plate is provided with multiple lower partitions (41) and multiple ridge metal blocks (42) , the coupling coefficient is controlled by the upper and lower partitions, and the resonant frequency of the resonator is lowered by the ridge metal block. The invention has low loss, low cost, small volume and easy processing, and can be used in mobile base station systems.

Description

Miniaturized flat coaxial cavity filter

technical field

The invention belongs to the technical field of radio frequency and microwave, in particular to a flat coaxial cavity filter, which can be used in a mobile base station system.

Background technique

With the development of 5G mobile communication and multiple-input multiple-output MIMO technology, metal and dielectric filters with small size and low loss are more and more used in mobile base stations, and their design methods are becoming more and more popular. focus on. In filter theory, the unloaded Q value reflects the size of the filter loss, and the larger the unloaded Q value, the smaller the filter loss. Most of the traditional base station filters are coaxial filters, but the size of the coaxial filter is too large, and it is necessary to process the inner and outer conductors separately, and then install all the inner conductors into the outer conductors separately, resulting in complicated processing procedures , It takes a lot of time to debug after the processing is completed, so the cost of the coaxial filter is relatively high. Although the suspended air stripline filter has the advantage of flatness, the intermediate conductor layer is a suspended dielectric substrate, resulting in a low Q value, and the coupling between non-adjacent cavities is difficult to control, so it is difficult to popularize in base station filters application.

In 2016, Cai Hui and others applied for a patent "a coaxial cavity filter", the patent number is CN206116570U. By decomposing the filter shell into a single thin-walled cavity, the production efficiency is improved and the heavy shell is omitted. , saving materials, reducing weight, thereby reducing costs. This kind of coaxial all-metal filter still needs to process the inner and outer conductors separately, which does not fundamentally solve the problems of high assembly cost and high debugging cost of the coaxial all-metal filter.

Contents of the invention

The purpose of the present invention is to address the shortcomings of the above-mentioned prior art, and propose a high-Q miniaturized flat coaxial cavity filter to reduce the overall size and processing complexity of the metal coaxial cavity filter of the base station. Improve machining accuracy, reduce loss and cost.

The technical idea of the present invention is to realize all the inner conductors of the coaxial cavity filter using an integrally processed flat metal structure to reduce the processing and installation difficulties of the inner conductors, thereby reducing costs and improving precision; by using Two layers of metal cover plates with metal partitions form the outer conductor, and the flattened metal inner conductor structure is suspended in the middle layer to improve the Q value of the cavity, thereby achieving the effect of low loss; by using a stepped impedance resonator, and A ridge structure is added to the lower cover plate on the wider side of each resonator to realize capacitive loading and thus realize the miniaturization of the filter.

According to the above ideas, the high-Q miniaturized flat coaxial cavity filter provided by the present invention includes an upper metal cover plate, two feed structures, an intermediate metal inner conductor and a lower metal cover plate, two feed The structure is located on the upper metal cover, and there is an air cavity between the upper metal cover and the lower metal cover, which is characterized by:

The intermediate metal inner conductor includes two taps, multiple resonators and peripheral fixtures, the two taps are respectively fixed on the first resonator and the last resonator, all resonators are fixed on the peripheral fixtures, and It is formed into a flat integrated structure through the metallization process of the metal plate or the medium surface, and is sandwiched between the upper metal cover plate and the lower metal cover plate;

The upper metal cover plate is provided with a plurality of upper partitions, the lower metal cover is provided with a plurality of lower partitions and a plurality of ridge metal blocks, and each upper partition is closely aligned with each lower partition , and run through the air cavity between the upper metal cover plate and the lower metal cover plate, and a plurality of ridge metal blocks are located under the plurality of resonators.

Preferably, each resonator adopts a T-shaped stepped impedance resonator, and the width of one end close to the peripheral fixing member is smaller than the width of the other end.

Preferably, each upper partition is located above between the narrower ends or wider ends of every adjacent two resonators among the plurality of resonators, and each lower partition is located at each phase of the plurality of resonators. The bottom between the narrower end or the wider end of two adjacent resonators is used to isolate the electric field or magnetic field, and control the coupling coefficient between the two adjacent resonators to be positive or negative.

Preferably, the plurality of ridge metal blocks are located directly below the wider ends of the plurality of resonators, so as to reduce the resonant frequency of the resonators and reduce the size of the resonators.

Preferably, the upper metal cover plate and the lower metal cover plate are made of metal material or medium surface metallization.

The present invention has the following technical advantages:

1. The middle flattened metal inner conductor of the present invention is integrally formed, and the surface of the upper and lower metal cover plates is made of metal material or metallized material on the dielectric surface, which can reduce the processing complexity and dielectric loss of the filter , so as to realize the characteristics of low cost and low loss.

2. The present invention adopts a layered combination method to process the upper and lower metal cover plates and the flat integrated metal inner conductor of the middle layer respectively, and then sandwich the metal inner conductor between the upper and lower metal cover plates, which is easy to assemble.

3. The present invention introduces a ridge metal block located on the lower metal cover plate under all resonators, so that capacitive loading is formed between the ridge metal block and each resonator, thereby reducing the resonant frequency of the resonator to achieve the effect of miniaturization.

4. The present invention introduces a partition between the upper and lower metal cover plates, which can flexibly control whether the coupling coefficient between adjacent resonant units is positive or negative.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic structural view of the upper metal cover plate in the present invention;

Fig. 3 is the schematic diagram of the structure of the intermediate metal inner conductor in the present invention;

Fig. 4 is a schematic structural view of the lower metal cover plate in the present invention;

Fig. 5 is a schematic diagram of a single resonator structure in the present invention;

Fig. 6 is the simulation curve of the resonant frequency of a single resonator according to the embodiment of the present invention as the distance d between the resonator and the ridge metal block changes;

Fig. 7 is the simulation curve of the unloaded Q value of a single resonator according to the embodiment of the present invention as the distance d between the resonator and the ridge metal block changes;

FIG. 8 is a simulation curve of scattering parameters according to an embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in further detail below in conjunction with accompanying drawing:

Referring to Figure 1, this embodiment includes four parts: two feed structures 2, an upper metal cover 1, a lower metal cover 4, and an intermediate metal inner conductor 3. The two feed structures 2 are located on the upper metal cover Above the plate 1, there is an air cavity between the upper metal cover 1 and the lower metal cover 4. The upper metal cover 1 and the lower metal cover 2 are made of metal materials or medium surface metallization, and the middle metal The inner conductor 3 is formed into a flat integrated structure by metallizing the surface of the metal plate or the medium, sandwiched between the upper metal cover 1 and the lower metal cover 4, the upper metal cover 1 and the lower metal cover 4 and the intermediate metal inner conductor 3 are silver-plated.

Referring to Fig. 2, the upper metal cover plate 1 includes a plurality of upper partitions 13, two small holes 11 and a plurality of tuning screws 12. In this example, the number of upper partitions is taken as thirteen, but not limited. The number of tuning screws is twenty-three.

Referring to Fig. 3, the intermediate metal inner conductor 3 includes two taps 32, a plurality of resonators 33 and peripheral fixing parts 31, the two taps 32 are respectively fixed on the first resonator and the tenth resonator, and all the resonators are fixed On the peripheral fixture 31, each resonator 33 adopts a T-shaped stepped impedance resonator, and the width near one end of the peripheral fixture 31 is smaller than the width of the other end. In this example, but not limited to, the number of resonators is ten .

Referring to Fig. 4, the lower metal cover plate 4 includes a plurality of lower partitions 41 and a plurality of ridge metal blocks 42. In this example, the number of lower partitions is taken as thirteen, and the number of ridge metal blocks is 13. The value is ten.

Referring to FIG. 5 , a plurality of ridge metal blocks 42 are located on the lower metal cover plate 4 directly below the wider ends of the plurality of resonators 33 .

The two feed structures 2 are respectively connected to the two taps 32 through two small holes 11, and a plurality of tuning screws 12 are located above the wider end of each resonator in the plurality of resonators 33 and every adjacent two Above between the narrower ends or between the wider ends of the resonators, each upper partition 13 is located above between the narrower ends or between the wider ends of every two adjacent resonators 33 in the plurality of resonators 33, each Each lower partition 41 is located below between the narrower ends or between the wider ends of every two adjacent resonators 33, and each upper partition 13 is closely aligned with each lower partition 41, And run through the air cavity between the upper metal cover 1 and the lower metal cover 4 .

In this example, ten tuning screws are located above the wide ends of the ten resonators, and thirteen tuning screws are located above each of the ten resonators between the narrow ends or between the wide ends of each adjacent resonator . The thirteen upper baffles are located above the narrower ends or the wider ends of every two adjacent resonators among the ten resonators, and the thirteen lower baffles are located between every two adjacent resonators among the ten resonators. The thirteen upper partitions are closely aligned with the thirteen lower partitions between the narrower ends or the wider ends of the resonators, and run through the gap between the upper metal cover and the lower metal cover. air cavity.

In this example, the advantage of miniaturization is achieved by using a stepped impedance resonator and performing ridged metal block processing to reduce the overall size of the circuit. By adding a partition to isolate the electric field or the magnetic field, the coupling coefficient between different resonators is positive or negative. The resonant frequency of each resonator is controlled by the tuning screw located directly above the resonator near the open end, and the coupling coefficient between each two resonators is controlled by the tuning screw located between the two resonators, the longer the tuning screw , the lower the resonant frequency of the resonator, the smaller the coupling coefficient between the resonators.

Effect of the present invention can be further illustrated by following simulation:

Simulation 1, using the commercial simulation software HFSS_15.0 to simulate and calculate the single resonator of the filter in the above embodiment, and obtain two parameters of the single resonator of the filter, wherein the resonant frequency obtained varies with the resonator and the ridge The results of the change of the distance d between the metal blocks are shown in Figure 6, and the obtained unloaded Q value varies with the distance d between the resonator and the ridge metal block, and the results are shown in Figure 7.

The abscissa in Fig. 6 is the spacing d, the unit is mm, and the range is from 1 mm to 5 mm, and the ordinate is the resonant frequency of a single resonator, the unit is GHz, and the range is 2.1 GHz to 3.0 GHz. It can be seen from FIG. 6 that as the distance d increases from 1 mm to 5 mm, the resonant frequency of a single resonator increases from 2.19 GHz to 2.79 GHz. In this example, d=2 mm. The above results show that the use of ridge metal blocks can effectively reduce the size of the resonator, thereby realizing the miniaturization of the filter.

The abscissa in Fig. 7 is the spacing d, the unit is mm, and the range is from 1 mm to 5 mm, and the ordinate is the unloaded Q value of a single resonator, without units, and the range is 2125-2625. It can be seen from FIG. 7 that as the distance d increases from 1mm to 5mm, the unloaded Q value of a single resonator increases from 2140 to 2610, and d=2mm in this example. The above results show that the use of ridge metal blocks will reduce the unloaded Q value while reducing the size, but the magnitude of the unloaded Q value is not reduced sharply and is still within an acceptable range.

Simulation 2, using the commercial simulation software HFSS_15.0 to simulate and calculate the overall structure of the filter in the above embodiment, and obtain the variation of the scattering parameters of the overall structure of the filter with frequency, as shown in FIG. 8 .

The abscissa in Figure 8 is the frequency, the unit is GHz, the range is from 2.4GHz to 2.8GHz, the ordinate is the decibel value of the scattering parameter amplitude, the unit is dB, the range is -120dB-5dB, and S11 represents the reflection of port 1 coefficient, S21 represents the transmission coefficient from port one to port two. It can be seen from Figure 8 that in the range from 2.515GHz to 2.675GHz, S11 is less than -20dB, and S21 is greater than -0.5dB, which shows that the filter loss is small. The whole circuit size is 108mm×35mm, which shows that the filter has a small volume.

The above simulation results show that, compared with the prior art, the miniaturized flat metal coaxial cavity filter proposed by the present invention has the advantages of compact size and easy processing while ensuring low loss.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (5)

1. A miniaturized flat coaxial cavity filter, including an upper metal cover (1), two feed structures (2), an intermediate metal inner conductor (3) and a lower metal cover (4) , the two feed structures (2) are located on the upper metal cover (1), and an air cavity is formed between the upper metal cover (1) and the lower metal cover (4), which is characterized in that: The intermediate metal inner conductor (3) includes two taps (32), a plurality of resonators (33) and peripheral fixtures (31), and the two taps (32) are fixed on the first resonator and the last resonator respectively. On the resonator, all resonators are fixed on the peripheral fixing parts (31), and formed into a flat integrated structure through the metallization process of the metal plate or the surface of the medium, sandwiched between the upper metal cover plate (1) and the lower metal cover between the plates (4); The upper metal cover (1) is provided with a plurality of upper partitions (13), and the lower metal cover (4) is provided with a plurality of lower partitions (41) and a plurality of ridge metal blocks (42) , each upper partition (13) is closely aligned with each lower partition (41), and runs through the air cavity between the upper metal cover (1) and the lower metal cover (4), multiple A ridge metal block (42) is located below the plurality of resonators (33). 2. The filter according to claim 1, characterized in that each resonator (33) is a T-shaped stepped impedance resonator, and the width of one end close to the peripheral fixing member (31) is smaller than the width of the other end. 3. The filter according to claim 1, characterized in that, each upper partition (13) is located between the narrower ends or the wider ends of each adjacent two resonators in the plurality of resonators (33) Above the space, each lower partition (41) is located between the narrower ends or the wider ends of each adjacent two resonators in the plurality of resonators (33), in order to isolate the electric field or magnetic field, Controls the coupling coefficient between these two adjacent resonators to be positive or negative. 4. The filter according to claim 1, characterized in that, a plurality of ridge metal blocks (42) are located directly below the wider ends of the plurality of resonators (33), in order to reduce the resonant frequency of the resonators and reduce the Dimensions of the resonator. 5. The filter according to claim 1, characterized in that, the upper metal cover plate (1) and the lower side metal cover plate (4) are made of metal material or dielectric surface metallization.