CN202159756U - Quasi-elliptic function type planar integrated waveguide band-pass filter - Google Patents

Abstract

The utility model relates to a quasi-elliptic function type planar integrated waveguide band-pass filter which belongs to the technical field of microwave devices. The quasi-elliptic function type planar integrated waveguide band-pass filter comprises two planar integrated waveguides which are mutually overlapped, each planar integrated waveguide is divided into four cavities by adopting a coupling slit formed by a metalized through hole, the four cavities are respectively a signal input and output cavity, a first coupling cavity, a second coupling cavity and a third coupling cavity sequentially from the signal input and output end to the inside; and a first coupling window (6) is arranged on the narrow-edge electric wall of the two third coupling cavities, a second coupling window (7) is arranged in the middle position of the two second coupling cavities, and two third coupling windows (8) are arranged in the vicinities of wide edges of the two first coupling cavities. The quasi-elliptic function type planar integrated waveguide band-pass filter has the characteristics of planar integrated waveguide high-power capacity, high Q value, low loss, simplicity in processing, small volume and high degree of integration; and cross-coupling in different forms is utilized among the cavities of the two planar integrated waveguides, and the filtering property with multiple transmission zero points is obtained.

Description

A quasi-elliptic function planar integrated waveguide bandpass filter

technical field

The utility model belongs to the technical field of microwave devices and relates to a plane integrated waveguide bandpass filter.

Background technique

Filter is a very important device in microwave circuits. In the case of increasingly tight spectrum resources and increasingly serious electromagnetic interference, higher requirements are placed on the performance and cost of filters. An ideal filter characteristic should be no attenuation in the passband and as large an attenuation as possible in the forbidden band. Traditional frequency-selective devices, such as: Butterworth flattest filter and Chebyshev filter can only improve the frequency-selective characteristics by increasing the order of the filter to meet the requirements. The weight and volume of the filter produced in this way Both are very large and cannot meet the miniaturization requirements of modern communications. Although the elliptic function filter has good selectivity, it is more difficult to realize. On the basis of the transfer function of the elliptic function filter, researchers developed a quasi-elliptic function filter, and proposed the idea of using quasi-elliptic function approximation to reduce the difficulty of implementation. The characteristics of this filter function are between Chebyshev and elliptic functions. In the case of the same order, the slope is steeper than the former, and it is easier to realize than the latter. This kind of filter with limited out-of-band transmission zeros is often implemented in the form of resonant cavity cross-coupling.

Filters based on metal waveguides usually have the advantages of high Q value, low loss, good selectivity, and large power capacity, but they require high processing accuracy, high cost, large volume, and are difficult to integrate with active circuits. Although filters based on planar circuit technologies such as microstrip lines and coplanar lines are easy to integrate with active circuits, they usually have large radiation, large loss, low Q value, and poor performance. Substrate integrated waveguide technology has the advantages of easy integration and convenient fabrication of planar circuits, and has excellent performance similar to metal waveguide filters.

Contents of the invention

The purpose of this utility model is to provide a quasi-elliptic function type planar integrated waveguide bandpass filter, which has the structural characteristics of a planar integrated waveguide, small size, high integration; at the same time, it has a lower insertion loss in the working frequency band And standing wave, the characteristics of high out-of-band suppression.

The technical scheme of the utility model is as follows:

A quasi-elliptic function planar integrated waveguide bandpass filter, as shown in Figure 1, includes a first dielectric layer 2 and a second dielectric layer 4 overlapping each other, with a second metal layer 3 between the two dielectric layers, and the second dielectric layer The upper surface of a dielectric layer 2 has a first metal layer 1, and the lower surface of a second dielectric layer 4 has a third metal layer 5; along the edges of both sides of the long side of the device, there are two rows of metallized through holes connected to the three-layer metal layer. wall, so that the first metal layer 1, the first dielectric layer 2 and the second metal layer 3 form a first plane integrated waveguide, while making the second metal layer 3, the second dielectric layer 4 and the third metal layer 5 form a second plane Integrated waveguide; one narrow side edge of the device has an electric wall formed by a row of metallized through holes connected to the three-layer metal layer, and the other narrow side is open; the first and second planar integrated waveguides have three columns connected to the three-layer metal layer. Metallized through-holes; metallized through-holes connected to three metal layers in each column are respectively connected to the upper and lower electrical walls, with a certain distance in the middle to form a coupling seam; the three coupling seams are parallel to each other, respectively integrating the first and second plane integrated waveguide Divided into four cavities, from the signal input and output end to the inside: the signal input and output cavity, the first coupling cavity, the second coupling cavity and the third coupling cavity; the opening in the second metal layer 3 (as shown in Figure 3) There are the following rectangular coupling windows: the first coupling window 6 located at the narrow electric wall of the third coupling cavity in the first and second planar integrated waveguides, the second coupling window 6 located in the middle of the second coupling cavity in the first and second planar integrated waveguides The windows 7 are two third coupling windows 8 located near the wide side of the first coupling cavity in the first and second planar integrated waveguides.

The quasi-elliptic function type planar integrated waveguide bandpass filter provided by the utility model has the characteristics of up and down symmetry, the input signal is input from any port, and sequentially passes through the signal input and output cavity of one of the planar integrated waveguides, the first coupling cavity, and the second coupling cavity. The cavity and the third coupling cavity are output through the third coupling cavity, the second coupling cavity, the first coupling cavity and the signal input and output cavity through another planar integrated waveguide. Among them, the signal is coupled and transmitted from the third coupling cavity of one planar integrated waveguide to the third coupling cavity of the other planar integrated waveguide through the first coupling window 6, and the second coupling cavity of the two planar integrated waveguides passes through the second coupling cavity. The coupling window 7 performs cross-coupling, and the first coupling cavities of the two planar integrated waveguides perform cross-coupling through the third coupling window 8. The filtering characteristics (insertion loss) of the entire filter are shown in FIG. 4 .

Compared with the prior art, the utility model has the following advantages:

The quasi-elliptic function type planar integrated waveguide bandpass filter provided by the utility model has the characteristics of high power capacity, high Q value, low loss, simple processing, small volume and high integration of planar integrated waveguide; Different forms of cross-coupling are used between the cavities to obtain filtering characteristics with multiple transmission zeros; high-performance frequency selectivity can be achieved within a specified frequency range, and a certain number of transmission zeros are available in the forbidden band. Its frequency selection performance is much better than Chebyshev filters and Butterworth filters of the same order.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the quasi-elliptic function planar integrated waveguide bandpass filter provided by the utility model.

Fig. 2 is a schematic diagram of the structures of the first and third metal layers in the quasi-elliptic function planar integrated waveguide bandpass filter provided by the present invention.

Fig. 3 is a schematic diagram of the structure of the second metal layer in the quasi-elliptic function planar integrated waveguide bandpass filter provided by the present invention.

Fig. 4 is an insertion loss diagram of the quasi-elliptic function planar integrated waveguide bandpass filter provided by the utility model.

Detailed ways

A quasi-elliptic function planar integrated waveguide bandpass filter, as shown in Figure 1, includes a first dielectric layer 2 and a second dielectric layer 4 overlapping each other, with a second metal layer 3 between the two dielectric layers, and the second dielectric layer The upper surface of a dielectric layer 2 has a first metal layer 1, and the lower surface of a second dielectric layer 4 has a third metal layer 5; along the edges of both sides of the long side of the device, there are two rows of metallized through holes connected to the three-layer metal layer. wall, so that the first metal layer 1, the first dielectric layer 2 and the second metal layer 3 form a first plane integrated waveguide, while making the second metal layer 3, the second dielectric layer 4 and the third metal layer 5 form a second plane Integrated waveguide; one narrow side edge of the device has an electric wall formed by a row of metallized through holes connected to the three-layer metal layer, and the other narrow side is open; the first and second planar integrated waveguides have three columns connected to the three-layer metal layer. Metallized through-holes; metallized through-holes connected to three metal layers in each column are respectively connected to the upper and lower electrical walls, with a certain distance in the middle to form a coupling seam; the three coupling seams are parallel to each other, respectively integrating the first and second plane integrated waveguide Divided into four cavities, from the signal input and output end to the inside: the signal input and output cavity, the first coupling cavity, the second coupling cavity and the third coupling cavity; the opening in the second metal layer 3 (as shown in Figure 3) There are the following rectangular coupling windows: the first coupling window 6 located at the narrow electric wall of the third coupling cavity in the first and second planar integrated waveguides, the second coupling window 6 located in the middle of the second coupling cavity in the first and second planar integrated waveguides The windows 7 are two third coupling windows 8 located near the wide side of the first coupling cavity in the first and second planar integrated waveguides.

In the above technical solution, the first and second dielectric layers are made of polytetrafluoroethylene with a dielectric constant of 2.1, and the thickness is 3mm; the thickness of the first and third metal layers is 1.5mm, and the thickness of the second metal layer is 3mm; all metallized through holes The diameter is 2mm, and the distance between two adjacent metallized through holes is 3.2mm; the narrow side width of the first and second planar integrated waveguides is 51.19mm; in the first and second planar integrated waveguides: the length of the third coupling cavity is 36.78mm, and the length of the second coupling cavity 38.79mm, the length of the first coupling cavity is 29.36mm, the coupling slot width between the third and second coupling cavity is 19.1mm, the coupling slot width between the second and first coupling cavity is 22.9mm, the first coupling cavity and the signal input and output cavity The width of the coupling slit between them is 31.7 mm; the first coupling window 6 is 19.76 mm long and 3 mm wide, the second coupling window 7 is a square with a side length of 11.99 mm, and the two third coupling windows 8 are 5.31 mm long and 5 mm wide.

The above specific quasi-elliptic function type planar integrated waveguide bandpass filter, the insertion loss simulation results are shown in Figure 4: the passband insertion loss is less than 0.45dB, the out-of-band suppression is greater than 30dB at 150MHz, and the passband is 3.1GHz to 3.4GHz .

Claims (2)

1. integrated waveguide bandpass filter in accurate elliptic function type plane; Comprise overlapped first dielectric layer (2) and second dielectric layer (4); Has second metal level (3) between the two layer medium layer; First dielectric layer (2) upper surface has the first metal layer (1), and second dielectric layer (4) lower surface has the 3rd metal level (5); Edge, both sides along the long limit of device has the electric wall that two rows connect the plated-through hole formation of three-layer metal layer; Make the first metal layer (1), first dielectric layer (2) and second metal level (3) form the first plane integrated waveguide, make second metal level (3), second dielectric layer (4) and the 3rd metal level (5) form the second plane integrated waveguide simultaneously; The edge, a narrow limit of device has the electric wall that a row connects the plated-through hole formation of three-layer metal layer, and another narrow limit is open; The plated-through hole that has three row connection three-layer metal layers in first and second plane integrated waveguide; The plated-through hole that every row connect the three-layer metal layer links to each other with upper and lower electric wall respectively, and the centre has a determining deviation, forms coupling slot; Article three, coupling slot is parallel to each other, and respectively first and second plane integrated waveguide is divided into four cavitys, is followed successively by inward from signal input output end: signal input and output chamber, first coupling cavity, second coupling cavity and the 3rd coupling cavity; Have following rectangle coupling window in second metal level (3): first coupling window (6) that is arranged in electricity wall place, the narrow limit of first and second plane integrated waveguide the 3rd coupling cavity; Be arranged in second coupling window (7) in first and second plane integrated waveguide second coupling cavity centre position, be arranged near two the 3rd coupling windows (8) of first and second plane integrated waveguide first coupling cavity broadside.

2. the integrated waveguide bandpass filter in accurate elliptic function type plane according to claim 1 is characterized in that, said first dielectric layer (2) and second dielectric layer (4) material are polytetrafluoroethylene.

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