A Ka-band gap waveguide filter with adjustable passband

Abstract

The present invention provides a gap waveguide filter with adjustable passband in the Ka band, comprising: a top metal plate, a metal pin, an artificial surface plasmon, a bottom metal plate and two flanges; the top metal plate is connected to a flange on both sides; the bottom metal plate is connected to a flange on both sides; the top metal plate and the bottom metal plate are arranged opposite to each other and in parallel; the metal pins are arranged on the bottom metal plate, and at least two groups of metal pins are arranged, and each group of metal pins has at least one row of metal pins arranged from one flange to another flange; there is an air gap between the top metal plate and the metal pins; the artificial surface plasmon is arranged on the bottom metal plate and is located between the two groups of metal pins. Under the condition of adjustable passband, the overall performance of the filter is improved and the design cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of filters and relates to a gap waveguide filter with adjustable Ka-band passband. Background Art

[0002] As an important RF front-end device in communication systems, filters are widely used in radar, satellite and other communication systems due to their excellent microwave frequency selectivity. It can be used as a link selection device in microwave transceiver systems, or as an attenuation device in a certain frequency band.

[0003] Surface plasmons can break through the diffraction limit and have strong local field enhancement characteristics, which can realize the transmission and processing of optical information at the nanoscale. For a long time, surface plasmons have only worked in the optical band, mainly because metals are regarded as ideal conductors in the microwave or terahertz bands and cannot excite surface plasmons. In recent years, artificial surface plasmons working in the microwave and terahertz bands have been discovered. Artificial surface plasmons have good development prospects and applications in devices such as antennas, power splitters, and filters.

[0004] The existing bandpass filters based on artificial surface plasmons have at least the following problems:

[0005] 1. Existing bandpass filters based on artificial surface plasmons mostly work in the Ku and lower frequency bands, which cannot meet users' requirements for bandwidth and speed of data transmission.

[0006] 2. Existing bandpass filters based on artificial surface plasmons mostly use microstrip structures. Microstrip transmission lines are semi-open structures and use dielectrics as transmission media. They have the disadvantage of large losses, and this disadvantage will be further amplified when they are used in high-frequency bands.

[0007] 3. The unit structure and the transition structure at the feeding point of the existing bandpass filter based on artificial surface plasmon are relatively complex, requiring higher processing accuracy and increasing processing costs. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a Ka-band gap waveguide filter with adjustable passband, which improves the overall performance of the filter and reduces the design cost under the condition of adjustable passband.

[0009] The present invention is achieved through the following technical solutions:

[0010] A gap waveguide filter with adjustable passband in the Ka band, comprising: a top metal plate, metal pins, artificial surface plasmons, a bottom metal plate and two flanges;

[0011] The two sides of the top metal plate are respectively connected to a flange; the two sides of the bottom metal plate are respectively connected to a flange; the top metal plate and the bottom metal plate are arranged opposite to each other and in parallel;

[0012] The metal pins are arranged on the bottom metal plate, and at least two groups of the metal pins are arranged, and each group of metal pins has at least one row of metal pins arranged in a direction from one flange to another flange; there is an air gap between the top metal plate and the metal pins; the artificial surface plasmon is arranged on the bottom metal plate and is located between the two groups of metal pins.

[0013] Preferably, the distance between the two groups of metal pins gradually decreases from the flange position to the position between the two flanges.

[0014] Furthermore, the maximum distance between the two groups of metal pins is the length of a standard WR-28 waveguide cross section.

[0015] Furthermore, the minimum distance between the two groups of metal pins is 5.32-5.72 mm.

[0016] Preferably, each group of metal pins is provided with two rows of metal pins in a direction from one flange to another flange.

[0017] Preferably, the sum of the height of the metal pin and the thickness of the air gap is equal to the width of a standard WR-28 waveguide cross section.

[0018] Preferably, the height of the artificial surface plasmon increases gradually from the flange position to the position between the two flanges.

[0019] Furthermore, the artificial surface plasmon includes three metal blocks of different heights on both sides and five metal blocks of equal heights in the middle.

[0020] Preferably, the gap waveguide filter is a symmetrical structure as a whole.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The gap waveguide filter with adjustable passband in the Ka band of the present invention has the following advantages. (1) The present invention combines the advantages of gap waveguide and artificial surface plasmon. The low-frequency cutoff frequency of the passband can be controlled by adjusting the distance between two groups of metal pins, that is, the slot width of the slot gap waveguide. The high-frequency cutoff frequency of the passband can be controlled by adjusting the height of the artificial surface plasmon. Thus, the passband is adjustable, so that the gap waveguide filter can work in the Ka band. The Ka band electromagnetic wave is a rare frequency band that can break through the atmospheric window. It is expected to become the mainstream electromagnetic frequency band for satellite-to-ground communication and is expected to be used in the Ka band satellite communication system. The adjustable passband can meet the user's demand for bandwidth and speed of data transmission. (2) Low loss. The present invention is a gap waveguide. The gap waveguide forms an electromagnetic shielding structure by two parallel metal surfaces. One of the metal surfaces forms a bed of nails. When this bed of nails is placed parallel to the other metal surface as an artificial magnetic conductor surface, an electromagnetic bandgap structure will be formed between the two surfaces. The transmission structure suppresses the dispersion mode and the electromagnetic waves propagate only in the air, and adopts an all-metal structure, so the gap waveguide filter of the present invention has the characteristics of low loss. The structure of the present invention reduces the in-band transmission loss while taking into account the out-of-band attenuation performance. (3) Easy to process. Compared with the traditional cavity waveguide, the gap waveguide does not require a tight electrical connection of the waveguide wall, which reduces the requirements for the processing technology. For example, the rectangular waveguide is a metal structure closed on all four sides. During processing, the welding requirements between the metal walls are very high. The contact condition of the metal walls will have a great impact on the performance of the rectangular waveguide, which greatly increases the difficulty of processing rectangular waveguide devices. Therefore, it is very difficult to apply rectangular waveguides to high-frequency communication devices such as millimeter wave communications. As a substitute for the traditional waveguide, the gap waveguide replaces the waveguide arm of the traditional waveguide with a periodic structure. The electromagnetic bandgap structure prevents the electromagnetic wave from radiating to both sides of the waveguide, thereby solving the problem that the wide side and the narrow side of the cavity waveguide must be tightly electrically connected. Since the two metal surfaces of the gap waveguide no longer need direct physical contact, and the artificial surface plasmon of the present invention is loaded in the slot of the gap waveguide, the filter has the characteristics of easy processing. (4) Strong anti-interference ability. Compared with microstrip transmission lines, when integrated with other components, due to the inherent packaging structure of the gap waveguide structure, the flange integrated design is adopted for mutual docking, and no additional shielding cover and isolation components are required. Therefore, there is no need to consider the effects of resonance caused by adding additional components and traditional cavity packaging structures. Therefore, the present invention has the characteristics of strong anti-interference ability. (5) Easy to dissipate heat. Compared with the closed rectangular waveguide filter, the metal pins and air gaps on both sides of the filter based on the gap waveguide replace the metal wall, so that heat escapes from both sides, which can better ensure the stability of the communication system and is suitable for applications with higher operating frequencies and higher power capacity density.

[0023] Furthermore, the distance between the two groups of metal pins gradually decreases from the flange to the middle of the two flanges, which can achieve a smooth transition from the flange to the slot gap waveguide without adding other transition or conversion structures, greatly reducing the loss of electromagnetic energy.

[0024] Furthermore, the sum of the height of the metal pin and the thickness of the air gap is the width of the standard WR-28 waveguide section, which can ensure the uniformity of the transverse cross-sectional dimensions of the electromagnetic wave from sending to transmission, reduce energy loss and facilitate processing and testing.

[0025] Furthermore, the height of the artificial surface plasmon increases from the flange position to the position between the two flanges, which can realize sub-wavelength confinement of the electromagnetic field in the slot of the slot gap waveguide and effectively excite the surface electromagnetic waves of the surface plasmon. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the gap waveguide filter with adjustable passband in the Ka band of the present invention, and there is a standard WR-28 flange plate integrated with the filter on each of the left and right sides.

[0027] Figure 2 This is a schematic diagram of the distribution of the component units of the gap waveguide filter with adjustable Ka-band passband of the present invention. In order to make the display clearer, the top metal plate and the flanges on both sides are hidden.

[0028] Figure 3 The figure is a schematic diagram of the metal pin structure of the gap waveguide filter with adjustable Ka-band passband according to the present invention.

[0029] Figure 4 The present invention is a schematic diagram of the artificial surface plasmon structure of the gap waveguide filter with adjustable Ka-band passband.

[0030] Figure 5 The transmission coefficient of the gap waveguide filter with adjustable passband in the Ka band of the present invention at different slot widths;

[0031] Figure 6 The transmission coefficient of the gap waveguide filter with adjustable passband in the Ka band of the present invention at different artificial surface plasmon heights;

[0032] Figure 7 The figure is an S parameter diagram of the gap waveguide filter with adjustable passband in the Ka band of the present invention;

[0033] Figure 8 The electric field distribution diagrams of the gap waveguide filter with adjustable passband in the Ka band of the present invention at 28, 33 and 38 GHz respectively;

[0034] Fig. 9This is a heat distribution diagram of the Ka-band passband-adjustable gap waveguide filter of the present invention when it is working. DETAILED DESCRIPTION

[0035] In order to further understand the present invention, the present invention is described below in conjunction with embodiments. These descriptions are only to further explain the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0036] like Figure 1 and 2 The present invention provides a gap waveguide filter with adjustable passband in the Ka band, comprising: a top metal plate 1, metal pins 2, artificial surface plasmons 3, a bottom metal plate 4 and two flanges 5. The flanges 5 are preferably standard WR-28 flanges.

[0037] The two sides of the top metal plate 1 are connected to the upper parts of the two flanges 5, and the two sides of the bottom metal plate 4 are connected to the lower parts of the two flanges 5. The top metal plate 1 and the bottom metal plate 4 are arranged opposite to each other and in parallel.

[0038] The metal pins 2 are embedded in the bottom metal plate 4, and at least two groups are arranged. Each group of metal pins 2 is arranged in at least one row from one flange 5 to another flange 5 to prevent lateral leakage of electromagnetic energy; the distance between the two groups of metal pins 2 is the cross-sectional length of the slot gap waveguide formed, and changing the distance can control the low-frequency cutoff frequency of the filter passband. The artificial surface plasmon 3 is arranged on the bottom metal plate 4 and is located between the two groups of metal pins 2, that is, in the slot of the slot gap waveguide. The low-pass characteristics of the artificial surface plasmon 3 itself provide the high-frequency cutoff frequency of the filter passband. The bottom metal plate 4 provides a unified bottom support for the metal pins 2 and the artificial surface plasmon 3.

[0039] There is an air gap between the top metal plate 1 and the metal pin 2 , and there is an equivalent capacitance between the bottom surface of the top metal plate 1 and the top of the metal pin 2 .

[0040] In a specific embodiment, the distance between the two groups of metal pins 2 gradually decreases from the position of the flange 5 to the position between the two flanges 5, the maximum distance is the length of the standard WR-28 waveguide section, and the minimum distance (i.e., the slot width d) determines the low-frequency cutoff frequency of the filter passband.

[0041] In a specific embodiment, the height of the artificial surface plasmon 3 increases from the position of the flange 5 to the position between the two flanges 5. In a specific embodiment, the artificial surface plasmon 3 includes three metal blocks of different heights on both sides (transition units) and five metal blocks of uniform height in the middle (complete units), and the height of the complete unit determines the high-frequency cutoff frequency of the filter passband.

[0042] In a specific embodiment, the filter is a symmetrical structure as a whole.

[0043] Example

[0044] like Figure 1 As shown, the embodiment of the present invention provides a gap waveguide filter with adjustable passband in the Ka band, comprising: a top metal plate 1, a metal pin 2, an artificial surface plasmon 3 and a bottom metal plate 4, with a standard WR-28 flange designed to be integrated with the filter on each of the left and right sides. The top metal plate 1 and the bottom metal plate 4 both have a size of 69.80 mm × 18.32 mm × 3 mm, and are respectively connected to the upper and lower parts of the standard WR-28 flange to form an integrated design structure.

[0045] The metal pin 2 is arranged on the bottom metal plate 4 to form an air gap with the top metal plate 1. The sum of the height of the metal pin 2 and the thickness of the air gap is equal to the width of the standard WR-28 waveguide section, 3.56 mm.

[0046] In the attached Figure 2 The distribution of metal pins 2 and artificial surface plasmons 3 is shown in FIG. Two groups of metal pins 2 are provided, and the distance between the two groups of metal pins 2 gradually decreases from the standard WR-28 flanges on both sides to the middle. The maximum distance is the length of the standard WR-28 waveguide section 7.12 mm, and the minimum distance is the slot width d of the slot gap waveguide. Changing the slot width d can control the low-frequency cutoff frequency of the filter passband. The artificial surface plasmon 3 is located between the two groups of metal pins 2. The artificial surface plasmon (3) includes three metal blocks of different heights on both sides (transition units) and five metal blocks of uniform height in the middle (complete units).

[0047] In the attached Figure 3 The structure of the metal pin 2 constituting the gap waveguide is shown in FIG. The final dimensions of the metal pin 2 are determined by parameter analysis of the metal pin 2 using the dispersion mode method: the side length of the bottom surface of the metal pin 2 is 1.2 mm, the pin height is 2.3 mm, the air gap height is 1.26 mm, and the metal pin 2 is spaced 1.6 mm apart.

[0048] In the attached Figure 4 The artificial surface plasmon 3 shown in FIG. 1 is composed of a metal block embedded in an underlying metal plate 4. By analyzing its dispersion curve, it is determined that the size of the metal block of the complete unit is 1.0 mm × 0.7 mm × 1.65 mm, and the interval between the metal blocks is 1.1 mm. The height of the complete unit determines the high-frequency cutoff frequency of the filter passband.

[0049] Attached Figure 5The transmission coefficient of the gap waveguide filter with different slot widths d is shown. It can be seen from the figure that the low-frequency cutoff frequency increases with the decrease of the slot width d, which corresponds to the frequency of the dispersion curve of the gap waveguide unit. At the same time, the high-frequency cutoff frequency remains at 35.30 GHz, with almost no change. Therefore, the low-frequency cutoff frequency of the gap waveguide filter of the present invention can be adjusted by changing the slot width d.

[0050] Attached Figure 6 The transmission coefficient of the gap waveguide filter is shown when the height of the complete unit of the artificial surface plasmon changes. The higher the height of the artificial surface plasmon, the lower the asymptotic frequency of its unit dispersion curve, and the lower the high-frequency cutoff frequency of the corresponding filter. At the same time, the low-frequency cutoff frequency remains basically unchanged.

[0051] Attached Figure 7 The S parameters of the bandpass filter finally designed by the present invention in the Ka band (26.5-40GHz) are shown. It can be seen from the figure that in the range of 29.7-35.4GHz, the filter has good passband characteristics, the return loss is greater than 10dB, and the insertion loss at the center frequency of 32.55GHz is 0.14dB. In addition, the filter has good out-of-band suppression performance, and its attenuation is greater than 35dB. At about 40GHz, the stopband performance begins to decline because higher-order modes will be transmitted in the gap waveguide.

[0052] By the attached Figure 8 The electric field distribution of the filter at 28 GHz, 33 GHz and 38 GHz can further illustrate the working principle of the gap waveguide filter of the present invention. Figure 5 As shown in the figure, the filter passband range is 29.7GHz-35.4GHz, so 33GHz is in the passband, and 28GHz and 38GHz belong to the low-frequency and high-frequency cutoff bands respectively. Figure 8 (b) It can be seen that at 33 GHz, electromagnetic energy is effectively transmitted from the input port to the output port, and the local field enhancement effect of artificial surface plasmon is obvious. Figure 8 As shown in (a), at 28 GHz, energy is fed into the left port and rapidly decays when it passes through the transition structure and reaches the fixed slot width, verifying the effect of the slot width of the gap waveguide on the low-frequency electromagnetic waves. Figure 8 (c) shows the electric field distribution in the filter at 38 GHz. As shown in the figure, the electromagnetic wave can be transmitted in the slot gap waveguide through the transition structure until it reaches the artificial surface plasmon and begins to attenuate, further verifying the influence of artificial surface plasmon on high-frequency electromagnetic waves.

[0053] Attached Fig. 9This is a thermal analysis diagram performed in COMSOL Multiphysics 5.5 to verify the heat dissipation performance of the air gaps between the metal pins and above the metal pins. The ambient temperature is set to 20°C and the input power is set to 100W. The heat transfer coefficient h used to calculate the convective heat flux density is set to 5. The temperature distribution of the gap waveguide filter is shown in the figure. Its operating temperature is about 49°C. When other conditions remain unchanged and only the gap waveguide is replaced by a rectangular waveguide, the operating temperature is about 128.5°C. This shows that the gap waveguide filter has good heat dissipation performance and is suitable for applications with higher operating frequencies and higher power capacity density.

[0054] In summary, the gap waveguide filter with adjustable passband in the Ka band of the present invention can control the low-frequency cutoff frequency of the passband by adjusting the distance between the two groups of metal pins, that is, the slot width of the slot gap waveguide, and can control the high-frequency cutoff frequency of the passband by adjusting the height of the artificial surface plasmon. The passband of the gap waveguide filter finally designed is 29.7GHz-35.4GHz. In addition, the gap waveguide filter of the present invention has a simple structure, is easy to process, has low loss, is easy to dissipate heat, and is suitable for the Ka band with high operating frequency and high power capacity density.

Claims

1. A gap waveguide filter with adjustable passband in Ka band, characterized in that: include: A top metal plate (1), metal pins (2), artificial surface plasmons (3), a bottom metal plate (4) and two flanges (5); Both sides of the top metal plate (1) are connected to a flange (5) respectively; both sides of the bottom metal plate (4) are connected to a flange (5) respectively; the top metal plate (1) and the bottom metal plate (4) are arranged vertically opposite to each other and in parallel; The metal pins (2) are arranged on the bottom metal plate (4), and the metal pins (2) are arranged in at least two groups, and each group of metal pins (2) is provided with at least one row of metal pins (2) in a direction from one flange (5) to another flange (5); an air gap exists between the top metal plate (1) and the metal pins (2); the artificial surface plasmon (3) is arranged on the bottom metal plate (4) and is located between the two groups of metal pins (2); The distance between the two groups of metal pins (2) gradually decreases from the position of the flange (5) to the position between the two flanges (5); the height of the artificial surface plasmon (3) increases from the position of the flange (5) to the position between the two flanges (5); and the artificial surface plasmon (3) comprises three metal blocks of unequal heights on each side and five metal blocks of equal heights in the middle.

2. The Ka-band passband-adjustable gap waveguide filter according to claim 1, characterized in that: The maximum distance between the two groups of metal pins (2) is the length of a standard WR-28 waveguide section.

3. The Ka-band passband-adjustable gap waveguide filter according to claim 1, characterized in that: The minimum distance between the two groups of metal pins (2) is 5.32-5.72 mm.

4. The Ka-band passband-adjustable gap waveguide filter according to claim 1, characterized in that: Each group of metal pins (2) is provided with two rows of metal pins (2) in a direction from one flange (5) to another flange (5).

5. The Ka-band passband-adjustable gap waveguide filter according to claim 1, characterized in that: The sum of the height of the metal pin (2) and the thickness of the air gap is equal to the width of the standard WR-28 waveguide section.

6. The Ka-band passband-adjustable gap waveguide filter according to claim 1, characterized in that: The gap waveguide filter is a symmetrical structure as a whole.

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