Terahertz waveguide filter with high out-of-band rejection

Abstract

The utility model discloses a terahertz waveguide filter with high out-of-band rejection, and relates to the technical field of optimization of terahertz waveguide filters. Comprising an input waveguide, a first single-mode resonant cavity, a plurality of central resonant cavities, a second single-mode resonant cavity and an output waveguide, central axes of the input waveguide, the first single-mode resonant cavity, the plurality of central resonant cavities, the second single-mode resonant cavity and the output waveguide are positioned on the same straight line, adjacent central resonant cavities are sequentially connected through coupling cavities, the input waveguide and the output waveguide adopt standard rectangular waveguides, and the central resonant cavities adopt TM210 high-order mode elliptical resonant cavities. The terahertz-band waveguide Chebyshev filter overcomes the defects that a traditional terahertz-band waveguide Chebyshev filter does not have an out-of-band transmission zero point and is low in out-of-band rejection degree. Compared with a traditional waveguide Chebyshev filter, the waveguide Chebyshev filter has a transmission zero point outside a low-frequency band, the zero point position is controllable, the out-of-band rejection degree is higher, and the vertical central resonant cavity is more compact in structure and low in loss.

Description

Technical Field

[0001] The utility model relates to the technical field of optimization of terahertz waveguide filters, in particular to a terahertz waveguide filter with high out-of-band suppression. Background Art

[0002] Bandpass filters are an indispensable component of communication systems and can be implemented in a variety of forms, including waveguide filters and microstrip line filters. In the terahertz frequency band (0.1THz to 10THz), waveguide bandpass filters are the optimal choice for this frequency band, as waveguides are closed cavities with lower losses. Filters play a frequency-selective role, and out-of-band rejection is a key filter specification, determining the filter's filtering characteristics. Higher out-of-band rejection indicates better filtering characteristics. In engineering practice, traditional waveguide Chebyshev filters are often used in solid-state transceiver links in the terahertz frequency band. Their relatively simple structure is a key advantage. However, traditional Chebyshev filters lack out-of-band transmission zeros, resulting in low out-of-band rejection. Achieving higher out-of-band rejection often requires more orders, which increases filter losses. Furthermore, in the terahertz frequency band, traditional Chebyshev filters employ a flat, cascaded structure, which is not compact enough, and their excessive length increases losses. Utility Model Content

[0003] The purpose of this utility model is to provide a terahertz waveguide filter with high out-of-band suppression, overcoming the shortcomings of conventional waveguide Chebyshev filters in the terahertz frequency band, which lack an out-of-band transmission zero and exhibit low out-of-band suppression. Compared to conventional waveguide Chebyshev filters, this filter features a controllable out-of-band transmission zero at low frequencies, resulting in higher out-of-band suppression. Its vertical central resonant cavity structure is more compact and reduces losses.

[0004] In order to solve the above technical problems, the present invention adopts the following solutions:

[0005] A terahertz waveguide filter with high out-of-band suppression includes an input waveguide, a first single-mode resonant cavity, several central resonant cavities, a second single-mode resonant cavity and an output waveguide, whose central axes are located on the same straight line and are connected in sequence through coupling cavities. The input waveguide and the output waveguide adopt standard rectangular waveguides, and the central resonant cavity adopts TM 210 High-order mode elliptical resonator.

[0006] In some specific embodiments, the central resonant cavity is vertical, the height of the central resonant cavity is higher than the height of a standard rectangular waveguide, the width is smaller than the width of a standard rectangular waveguide, the length of the central resonant cavity is greater than the height of the central resonant cavity, and the width of the central resonant cavity is the width along the direction of the center line connecting the first single-mode resonant cavity and the second single-mode resonant cavity.

[0007] In some specific embodiments, the height and width of the first single-mode resonant cavity and the second single-mode resonant cavity are consistent with the height and width of a standard rectangular waveguide, and the width of the first single-mode resonant cavity and the second single-mode resonant cavity is greater than the width of the central resonant cavity.

[0008] In some specific embodiments, each corner of the central resonant cavity is configured as a chamfer.

[0009] In some embodiments, the central resonant cavity can operate in both a main resonant mode and a non-resonant mode.

[0010] In some embodiments, the central resonant cavity operates in the same passband as the Chebyshev filter when operating in the main resonant mode.

[0011] In some embodiments, the central resonant cavity can couple energy with non-adjacent resonant cavities when operating in a non-resonant mode.

[0012] In some embodiments, the height of the coupling cavity is consistent with the height of a standard rectangular waveguide, the width is smaller than the width of the central resonant cavity, and the length is smaller than the width of the standard waveguide.

[0013] Beneficial effects of the utility model:

[0014] The utility model discloses a terahertz waveguide filter with high out-of-band suppression, wherein the central resonant cavity is based on TM 210 High-order mode elliptical resonator is realized. This TM 210 High-order mode elliptical resonator and ordinary filter TE 101 Compared to a single-mode rectangular resonant cavity, the main resonant mode not only produces the same passband as a traditional filter resonant cavity, but also allows energy coupling between non-adjacent resonant cavities through non-resonant modes, thereby introducing a transmission zero in the filter's low-frequency band and significantly improving the filter's out-of-band suppression. Furthermore, the central resonant cavity is vertical, with its length greater than its height, reducing the overall filter length. This makes the filter structure more compact and reduces losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of a traditional waveguide Chebyshev filter in the prior art;

[0016] Figure 2 Schematic diagram of performance parameters of a conventional waveguide Chebyshev filter in the prior art;

[0017] Figure 3 A schematic structural diagram of a terahertz waveguide filter with high out-of-band suppression provided by an embodiment of the present utility model;

[0018] Figure 4A schematic diagram of filtering performance parameters of a 0.2 THz frequency band third-order filter provided by an embodiment of the present utility model;

[0019] Figure 5 This is a schematic diagram of transmission zero point position control provided by an embodiment of the present utility model.

[0020] Description of reference numerals:

[0021] 1-input waveguide, 2-first single-mode resonant cavity, 3-center resonant cavity, 4-second single-mode resonant cavity, 5-output waveguide, 6-coupling cavity. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the embodiments and drawings, but the implementation manner of the present invention is not limited thereto.

[0023] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "longitudinal", "lateral", "horizontal", "inside", "outside", "front", "back", "top", "bottom", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the utility model product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "opened," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0025] The traditional waveguide Chebyshev filter structure consists of several single-mode resonant cavities cascaded together, and these single-mode resonant cavities adopt a flat structure to ensure that the electromagnetic wave signal can stimulate TE when transmitted in the cavity. 101 Mode resonance. The height of the single-mode resonant cavity is the same as the height of the input and output waveguides.

[0026] Specifically, the traditional waveguide Chebyshev filter structure in the terahertz band is based on TE 101 The single-mode rectangular resonant cavity realizes the filtering characteristics. Taking the third-order waveguide Chebyshev filter in the 0.2THz (200GHz) frequency band as an example, its structure is as follows: Figure 1As shown, its filtering performance parameters are as follows Figure 2 As shown in the figure, S21 represents insertion loss and S11 represents return loss. Out-of-band rejection refers to the S21 parameter level outside the filter's passband. The faster the out-of-band S21 decreases and the steeper the slope of the curve, the higher the filter's out-of-band rejection. The figure shows that in the 0.2 THz frequency band, a third-order traditional waveguide Chebyshev filter has no out-of-band transmission zero, the S21 curve decreases slowly, and the out-of-band rejection is low.

[0027] In order to solve the problem that the traditional waveguide Chebyshev filter has no out-of-band transmission zero point and is not compact enough, the present invention is described in detail below with reference to the accompanying drawings and in combination with embodiments:

[0028] Example 1:

[0029] like Figure 3 As shown, this embodiment provides a terahertz waveguide filter with high out-of-band suppression, including an input waveguide 1, a first single-mode resonant cavity 2, a plurality of central resonant cavities 3, a second single-mode resonant cavity 4 and an output waveguide 5, whose central axes are located on the same straight line and are connected in sequence by coupling cavities 6. The input waveguide 1 and the output waveguide 5 are standard rectangular waveguides, and the central resonant cavity 3 is a TM210 high-order mode elliptical resonant cavity.

[0030] To achieve a more compact filter structure and reduce losses, the central resonant cavity 3 is vertical. Its height is higher than that of a standard rectangular waveguide, while its width is smaller. Its length is greater than its height, and its width is measured along the line connecting the centers of the first single-mode resonant cavity 2 and the second single-mode resonant cavity 4. The length of the central resonant cavity 3 is greater than the width of a standard rectangular waveguide.

[0031] The height and width of the first single-mode resonant cavity 2 and the second single-mode resonant cavity 4 are consistent with those of a standard rectangular waveguide, and the widths of the first single-mode resonant cavity 2 and the second single-mode resonant cavity 4 are greater than the width of the central resonant cavity 3. The height of the coupling cavity 6 is consistent with that of a standard rectangular waveguide, the width is less than the width of the central resonant cavity 3, and the length is less than the width of a standard waveguide.

[0032] In order to facilitate processing, each corner of the central resonant cavity 3 is chamfered.

[0033] A transmission zero is introduced in the filter's low-frequency band, significantly improving the filter's out-of-band rejection. Central resonant cavity 3 can operate in both main resonant and non-resonant modes. When operating in the main resonant mode, central resonant cavity 3 has the same passband as a Chebyshev filter. When operating in the non-resonant mode, central resonant cavity 3 can couple energy with non-adjacent resonant cavities.

[0034] This embodiment takes the 0.2THz frequency band third-order filter as an example, the structure is as follows Figure 3 As shown, the filter characteristics of this embodiment are similar to those of traditional waveguide Chebyshev filters in the terahertz frequency band. The difference is that the central resonant cavity 3 is implemented based on a TM210 high-order mode elliptical resonant cavity. Compared with the TE101 single-mode rectangular resonant cavity of ordinary filters, this TM210 high-order mode elliptical resonant cavity not only has a main resonant mode that produces the same passband as the traditional filter resonant cavity, but also can couple energy between non-adjacent resonant cavities through non-resonant modes, thereby introducing a transmission zero in the filter's low-frequency band and greatly improving the filter's out-of-band suppression. At the same time, the TM210 high-order mode elliptical resonator is upright, the height of the central resonator is h, the width is a, and the length is b. The length of the standard rectangular waveguide is a1, the width is b1, and the height is h1. It can be seen that a<hh1, b>b1. This design of the central resonant cavity 3 as an upright type not only satisfies the requirement that the electromagnetic wave signal can excite the TM210 mode resonance when transmitted in the cavity, but also reduces the overall filter length, which makes the filter structure more compact and reduces the loss.

[0035] The 0.2THz frequency band third-order filter designed in this embodiment is used for experiments, and its filtering performance parameters are obtained as follows: Figure 4 shown. Figure 4 The results show that the terahertz waveguide filter with high out-of-band suppression has a transmission zero outside the low-frequency band, a steep slope of the S21 parameter curve, a high roll-off coefficient, and high out-of-band suppression.

[0036] The filter structure described above uses only one central resonant cavity 3 of the TM210 high-order mode elliptical resonant cavity. Multiple TM210 high-order mode elliptical resonant cavities can also be used. Two adjacent central resonant cavities 3 are connected by a coupling cavity 6. When the filter has multiple TM210 high-order mode elliptical resonant cavities, multiple out-of-band transmission zeros can be introduced to further improve the performance of the filter.

[0037] It should be noted that this embodiment only provides a filter operating in the 0.2THz frequency band. In actual use, the frequency of the filter can be changed by adjusting the size of the resonant cavity, and can be used in the entire THz frequency band. In addition, the transmission zero point position of the filter can be manually controlled as needed. By controlling the relative position of the TM210 high-order mode elliptical resonant cavity, the transmission zero point at a specific position can be achieved. The results of manual control are shown in Figure 2. Figure 5 shown.

[0038] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will be able to make various modifications and improvements without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A terahertz waveguide filter with high out-of-band suppression, characterized in that: The invention comprises an input waveguide (1), a first single-mode resonant cavity (2), a plurality of central resonant cavities (3), a second single-mode resonant cavity (4), and an output waveguide (5), the central axes of which are located on the same straight line and are connected in sequence via coupling cavities (6). The input waveguide (1) and the output waveguide (5) adopt standard rectangular waveguides, and the central resonant cavity (3) adopts a TM210 high-order mode elliptical resonant cavity.

2. The terahertz waveguide filter with high out-of-band suppression according to claim 1, characterized in that: The central resonant cavity (3) is vertical, the height of the central resonant cavity (3) is higher than the height of a standard rectangular waveguide, the width is smaller than the width of the standard rectangular waveguide, the length of the central resonant cavity (3) is greater than the height of the central resonant cavity (3), and the width of the central resonant cavity (3) is the width along the direction of the center line connecting the first single-mode resonant cavity (2) and the second single-mode resonant cavity (4).

3. The terahertz waveguide filter with high out-of-band suppression according to claim 2, characterized in that: The height and width of the first single-mode resonant cavity (2) and the second single-mode resonant cavity (4) are consistent with the height and width of a standard rectangular waveguide, and the width of the first single-mode resonant cavity (2) and the second single-mode resonant cavity (4) is greater than the width of the central resonant cavity (3).

4. The terahertz waveguide filter with high out-of-band suppression according to claim 1, characterized in that: Each corner of the central resonant cavity (3) is arranged as a chamfer.

5. The terahertz waveguide filter with high out-of-band suppression according to claim 1, characterized in that: The central resonant cavity (3) can operate in two modes: a main resonant mode and a non-resonant mode.

6. The terahertz waveguide filter with high out-of-band suppression according to claim 5, characterized in that: When the central resonant cavity (3) operates in the main resonant mode, the passband is the same as that of the Chebyshev filter.

7. The terahertz waveguide filter with high out-of-band suppression according to claim 5, characterized in that: When the central resonant cavity (3) operates in a non-resonant mode, it can perform energy coupling with non-adjacent resonant cavities.

8. The terahertz waveguide filter with high out-of-band suppression according to claim 2, characterized in that: The height of the coupling cavity (6) is consistent with that of a standard rectangular waveguide, the width is smaller than that of the central resonant cavity (3), and the length is smaller than the width of the standard waveguide.

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