A miniaturized waveguide filter based on equivalent surface plasmon polaritons

Abstract

The application discloses a miniaturized waveguide filter based on equivalent surface plasmon polaritons, which comprises a bottom metal waveguide, a top metal cavity connected with the upper surface of the bottom metal waveguide and a metal grating sheet arranged between the bottom metal waveguide and the top metal cavity; the bottom metal waveguide is through on both sides, the opening of the top metal cavity faces downward and is communicated with the upper surface of the bottom metal waveguide, and the metal grating sheet has a plurality of equidistant grating units. The application realizes a wide-band, low-insertion-loss and miniaturized waveguide filter based on equivalent surface plasmon polaritons, is simple in design, reduces design time and improves design efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microwave components, in particular to a miniaturized waveguide filter based on equivalent surface plasmon polaritons. BACKGROUND

[0002] Metal waveguide filters are widely used in microwave or millimeter wave relay communication, microwave measurement, radar and other systems due to their high power capacity, low insertion loss, high mechanical strength and other advantages, and are important passive devices for suppressing interference signals. However, due to the inherent large size and weight of traditional waveguide filters, it is difficult to meet the miniaturization requirements of advanced communication systems.

[0003] Currently, there are three technologies for realizing miniaturized waveguide filters: one is to design filters based on substrate integrated waveguide technology, but the power capacity is much lower than that of metal waveguide filters; two is to use light metal materials or synthetic materials, but the reliability is low and it is difficult to be used in harsh environments; three is to use a different theoretical method from traditional theory to design filters, but this method is often difficult to design filters and has a long simulation period. In addition, metal waveguide filters are often used to design narrowband filters, and it is not easy to realize wideband filters.

[0004] Equivalent surface plasmon polaritons can effectively improve the performance of traditional devices and show great potential in improving traditional microwave system devices. However, existing filter designs based on equivalent surface plasmon polaritons mainly rely on substrate integrated waveguide technology, which is difficult to meet the requirements of high power capacity and miniaturization. Therefore, how to realize a wideband, low insertion loss, and miniaturized waveguide filter is still a great challenge in filter design. SUMMARY

[0005] In view of the problems existing in the prior art, the present application proposes a miniaturized waveguide filter based on equivalent surface plasmon polaritons, aiming to realize a wideband, low insertion loss, and miniaturized waveguide filter.

[0006] The present application is realized by the following technical scheme: a miniaturized waveguide filter based on equivalent surface plasmon polaritons, characterized in that it comprises a bottom metal waveguide, a top metal cavity connected to the upper surface of the bottom metal waveguide, and a metal grid sheet arranged between the bottom metal waveguide and the top metal cavity.

[0007] The bottom metal waveguide and the top metal cavity are placed above and below, and the inner top surface of the top metal cavity is parallel to the inner bottom surface of the bottom metal waveguide. The two sides of the bottom metal waveguide are through, and the opening surface of the top metal cavity faces downward and is in communication with the upper surface of the bottom metal waveguide. The metal grid sheet is arranged at the intersection position of the opening surface of the bottom metal waveguide and the top metal cavity, and the metal grid sheet has a plurality of equally spaced grid units.

[0008] Further, the low frequency cutoff frequency of the passband is controlled by adjusting the width W1 of the bottom metal waveguide, and the high frequency cutoff frequency of the passband is controlled by adjusting the width W2 of the top metal cavity opening.

[0009] Further, the cavity structure of the top metal cavity is a trapezoidal structure, and the bottom metal waveguide is a rectangular waveguide.

[0010] Further, a cuboid slot for placing a metal grid sheet is arranged above the bottom metal waveguide.

[0011] Further, each metal grid unit and the top metal cavity and the bottom metal waveguide form an equivalent surface plasmon unit.

[0012] Further, the overall size of the miniaturized waveguide filter is 1.3λ0*1.27λ0*1.3λ0, wherein λ0 is the wavelength corresponding to the working frequency of the filter.

[0013] Further, the internal mode of the miniaturized waveguide filter during operation is a hybrid mode, specifically including an equivalent surface plasmon surface wave mode and a TE 10 mode.

[0014] Further, the overall structure of the miniaturized waveguide filter is symmetrical about the axis.

[0015] Further, the out-of-band high frequency suppression frequency of the filter is controlled by adjusting the upper side length of the trapezoidal cavity.

[0016] Compared with the prior art, the present application has the following advantages and positive effects: (1) wide frequency band, the present application controls the low frequency cutoff frequency of the passband by adjusting the transverse width W1 of the bottom metal waveguide, and controls the high frequency cutoff frequency of the passband by adjusting the transverse width W2 of the top metal cavity, thereby realizing adjustable passband and realizing the wideband design difficult to achieve by traditional metal waveguide filters. (2) low insertion loss, the propagation mode of the miniaturized waveguide filter based on the equivalent surface plasmon is a hybrid mode, including a surface wave mode of the equivalent surface plasmon and a TE 10 mode, and the transmission performance is excellent due to the stronger binding ability of the surface wave mode compared with a single mode. (3) miniaturization, the miniaturized waveguide filter based on the equivalent surface plasmon proposed by the present application has a size of only 1.3λ0*1.27λ0*1.3λ0, λ0 is the wavelength under the corresponding working frequency, and the size is greatly reduced compared with traditional filters, the length of the waveguide transition section is reduced, and the structure is more compact. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of the overall structure of the embodiment of the present application.

[0018] Figure 2 The side view of the whole structure of the embodiment of the present application.

[0019] Figure 3 The structural schematic diagram of the top layer metal cavity, the bottom layer metal waveguide and the metal grid sheet of the present application.

[0020] Figure 4 The structural schematic diagram of the equivalent surface plasmon unit of the present application.

[0021] Figure 5 The dispersion curve diagram of the equivalent surface plasmon unit of the present application.

[0022] Figure 6 The transmission coefficient of the embodiment of the present application when the width W1 of the bottom layer metal waveguide is different.

[0023] Figure 7 The transmission coefficient of the embodiment of the present application when the width W2 of the top layer metal cavity is different.

[0024] Figure 8 The S parameter diagram of the embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to clearly illustrate the technical features of the present application, the present application will be described in detail below with specific embodiments and in conjunction with the drawings.

[0026] As shown in the drawings, it is an embodiment of a miniaturized waveguide filter based on equivalent surface plasmon, which comprises a bottom layer metal waveguide 1, a top layer metal cavity 2, a metal grid sheet 3 and two flanges 4, which are standard WR-90 flanges. Figures 1 to 4 The bottom layer metal waveguide 1 and the top layer metal cavity 2 are placed one above the other, and the inner top surface of the top layer metal cavity 2 is parallel to the inner bottom surface of the bottom layer metal waveguide 1; the two sides of the bottom layer metal waveguide 1 are through, and the opening surface of the top layer metal cavity 2 faces downward and communicates with the upper surface of the bottom layer metal waveguide 1; the metal grid sheet 3 is arranged at the position where the opening surface of the bottom layer metal waveguide 1 intersects with the top layer metal cavity 2, and the metal grid sheet 3 has a plurality of grid units at equal intervals, and the three are fixed into a whole through the metal through holes on the two sides, and the two flanges 4 are connected to the two sides of the above-mentioned whole respectively.

[0027] In this embodiment, the width W1 of the bottom layer metal waveguide controls the low frequency cutoff frequency of the filter passband, and the width W2 of the top layer metal cavity is the same as the width of the metal grid sheet, and the width W2 of the top layer metal waveguide controls the high frequency cutoff frequency of the filter passband.

[0028]

[0029] ​In this embodiment, the cavity structure of the top layer metal cavity is a trapezoidal structure cavity, the upper side length of the trapezoidal structure is 0.5 mm, the lower side length is 12.1 mm, and the height is 10.16 mm. The out-of-band high-frequency suppression frequency of the filter is controlled by adjusting the upper side length of the trapezoidal cavity.

[0030] Please refer to Figure 3 , the structure diagram of the top layer metal cavity, the bottom layer metal waveguide and the metal grid sheet of the present application is shown. The cavity structure of the top layer metal cavity is a trapezoidal body. In this embodiment, the cross-sectional size of the bottom layer metal waveguide is the standard WR-90 waveguide cross-sectional size, and the metal grid sheet includes 30 equidistant grid units, each grid unit has a length P of 1 mm and a thickness of 0.2 mm. There is a 31.6*30.86*0.6 mm cuboid groove above the bottom layer metal waveguide for placing the metal grid sheet. In combination with Figure 4 , the equivalent surface plasmon unit structure of the present application is shown, and the unit period is equal to the grid unit length, which is 1 mm.

[0031] As Figure 5 shown is the eigenmode dispersion curve of the equivalent surface plasmon unit structure, the starting frequency point of the curve is the low-frequency cutoff frequency of the corresponding filter passband, and the asymptotic frequency point is the high-frequency cutoff frequency of the corresponding filter passband.

[0032] Figure 6 The transmission coefficient of this embodiment at different widths W1 of the bottom layer metal cavity is shown. The wider the width W1 of the bottom layer metal waveguide, the lower the starting frequency of the dispersion curve of the equivalent surface plasmon unit, and the lower the low-frequency cutoff frequency of the corresponding filter.

[0033] Figure 7 The transmission coefficient of this embodiment at different widths W2 of the top layer metal cavity is shown. The wider the width W2 of the top layer metal cavity, the lower the asymptotic frequency of the dispersion curve of the equivalent surface plasmon unit, and the lower the high-frequency cutoff frequency of the corresponding filter.

[0034] Figure 8 The S parameters of the 6.6-12 GHz bandpass filter finally designed in this embodiment are shown. As shown in the figure, the filter of this embodiment has good passband characteristics in the range of 6.6-12 GHz, and the return loss is greater than -15 dB. The insertion loss at the center frequency of 9.3 GHz is about 0.05 dB. In addition, the filter has a certain out-of-band suppression performance, and the attenuation is greater than -40 dB. The stopband performance starts to decrease at about 14.5 GHz, because higher order modes will be transmitted in the equivalent surface plasmon waveguide.

[0035] In summary, the miniaturized waveguide filter based on equivalent surface plasmon polaritons provided by the application controls the low-frequency cutoff frequency of the filter passband by adjusting the width W1 of the bottom metal waveguide, controls the high-frequency cutoff frequency of the filter passband by adjusting the width W2 of the top metal cavity, and finally designs the passband of the miniaturized waveguide filter based on equivalent surface plasmon polaritons as 6.6GHz-12GHz. The filter has the advantages of wide frequency band, low insertion loss and miniaturization.

[0036] In addition, the specific implementation methods of the present application are many, and the above description is only the preferred embodiment of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, further improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. An equivalent surface plasmon polariton based miniaturized waveguide filter, characterized in that: The application relates to a waveguide filter, which comprises a bottom metal waveguide, a top metal cavity connected with the upper surface of the bottom metal waveguide, and a metal grid plate arranged between the bottom metal waveguide and the top metal cavity; the bottom metal waveguide and the top metal cavity are arranged in a vertical mode, the inner top surface of the top metal cavity is parallel to the inner bottom surface of the bottom metal waveguide; the two sides of the bottom metal waveguide are through, the opening surface of the top metal cavity faces downward and communicates with the upper surface of the bottom metal waveguide; the metal grid plate is arranged at the position where the opening surface of the bottom metal waveguide intersects with the top metal cavity, and a plurality of equidistant grid units are arranged on the metal grid plate. The cavity structure of the top layer metal cavity is a trapezoidal structure, that is, the cross section of the top layer metal cavity is trapezoidal, the cross section is perpendicular to the transmission direction of the waveguide, the bottom layer metal waveguide is a rectangular waveguide, the width of the top layer metal cavity and the width of the metal grid piece are the same, the low frequency cutoff frequency of the passband is controlled by adjusting the width of the bottom layer metal waveguide The high frequency cutoff frequency of the passband is controlled by adjusting the width of the top layer metal cavity opening The high frequency rejection frequency of the filter is controlled by adjusting the upper side length of the trapezoidal cavity.

2. The compact waveguide filter based on equivalent surface plasmon polaritons of claim 1, wherein, A cuboid groove for placing the metal grid plate is arranged above the bottom metal waveguide; each metal grid unit, the top metal cavity and the bottom metal waveguide form a subwavelength period unit.

3. The compact waveguide filter based on equivalent surface plasmon polaritons of claim 1, wherein, The overall size of the miniaturized waveguide filter is 1.3 x 1.27 x 1.3 wherein is the corresponding wavelength at the filter operating frequency.

4. The compact waveguide filter based on equivalent surface plasmon polaritons of claim 1, wherein, The overall structure of the miniaturized waveguide filter is symmetrical about the axis.

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